Nuclear and membrane-bound hormone receptors in glioblastoma: Expression, functionality, and therapeutic implications

AbstractAbstract

The 2021 WHO classification of brain tumors emphasizes integrating molecular features with histopathology, notably redefining astrocytoma and glioblastoma entities. Recent research underscores the influence of sex hormones in glioblastoma development and therapy response. This review focuses on the 5-year updated understanding of the role of nuclear and membrane receptors in glioblastoma biology and therapy. Notably, androgen receptor expression is linked to worse outcomes, but recent studies suggest androgen signaling might sustain anti-tumor immunity. Estrogen receptor subtypes, as well as nuclear or membrane progesterone receptors, show divergent roles. Beyond classical nuclear receptors, attention is paid to membrane-bound and G protein-coupled receptors (GPCRs), which regulate key pathways in glioblastoma progression. Among them, G protein-coupled membrane estrogen receptor, the G protein-coupled estrogen receptor, is gaining attention for its ability to modulate cell proliferation and tumor behavior. CXCR4, a chemokine receptor, is now seen as a critical driver of tumor growth and immune evasion. Cannabinoid receptors are also implicated in glioblastoma proliferation and drug resistance. Dopamine receptors, particularly DRD2 and DRD3, are emerging as regulators of glioblastoma stem cell maintenance and therapy resistance. Targeting hormone and GPCR-related pathways, especially considering sex-specific factors, offers promising avenues for developing personalized glioblastoma treatments and enhancing current therapy outcomes.

Key Points.

• Steroids, mainly estrogens and androgens, play a contradictory role in glioblastoma, depending on the receptors expressed in tumor cells or tumor micro-environment.

• G protein-coupled receptors are a class of receptors that contribute to key processes in glioblastoma.

• Both nuclear hormone receptors and their membrane-bound counterpart activities may be modulated for the development of precision medicine against glioblastoma.

In 2021, WHO classification of brain tumors adopted an integrated approach, combining histopathological features with key molecular alterations¹. The definition of tumor entities is now based on precise genetic criteria, which improves the accuracy of diagnosis, prognosis, and therapeutic choice.

These molecular criteria are essential to refine the diagnosis, assess prognosis, and guide treatment decisions, particularly for targeted therapies and inclusion in clinical trials.

The key changes for classification of diffuse glioma entities are:

• Astrocytoma, IDH-mutant (IDH-mut), which now includes what was formerly called “anaplastic astrocytoma” and “IDH-mutant glioblastoma,” graded from 2 to 4.

• Glioblastoma (GB) is now only IDH-wildtype (IDH-wt) tumors with defined molecular features; the term no longer applies to IDH-mut tumors.

Besides, an increasing number of studies have underscored the pivotal role of immune environment, sex, and hormones in gliomagenesis, glioma progression, and response to treatment. Gliomas, particularly glioblastoma (GB), exhibit distinct sex-based disparities in adults, with higher incidences of these tumors in males compared to females (1.4:1 ratio). This sex disparity tends to narrow in older populations, suggesting that sex hormones play a significant role in this difference. Estrogens, particularly via their nuclear and membrane receptors, have been shown to exert protective effects in female patient and preclinical models (all from IDH-wildtype [IDH-wt] cells), potentially explaining the lower incidence of gliomas in premenopausal women compared to men of similar age.^2,3 Conversely, androgens have been implicated in promoting cell proliferation and invasion and cancer stem cell survival in male models, highlighting the important role of hormonal regulation in GB initiation and growth.⁴ These differences go beyond incidence rates and extend to tumor biology, progression, and how gliomas respond to standard therapies.

Sex also appears to influence the progression of gliomas and plays a crucial role in the response to standard treatments, with male gliomas generally being more aggressive and exhibiting poorer prognoses compared to their female counterparts. In preclinical models, female GB tend to exhibit slower growth and greater sensitivity to chemotherapy and radiation.⁵ Male patients often show a less favorable response to conventional therapies, such as temozolomide (TMZ), when compared to females. Estrogen and other sex hormones modulate directly the efficacy of treatments through DNA repair mechanisms. For instance, estrogen is known to protect against DNA damage, which might explain why postmenopausal women, who have lower estrogen levels, tend to have worse clinical outcomes compared to younger, premenopausal women. On the other hand, androgens may contribute to chemotherapy resistance in males, highlighting the need to develop sex-specific treatment strategies.⁶

In parallel to understanding the influence of sex on gliomas, several teams aimed at identifying the expression levels, modulators of classical nuclear hormone receptor activity, and exploring their mechanism of action in tumor cells and microenvironment of both sexes, as a crucial step toward the development of more tailored, effective, and personalized therapies for glioma patients. Other receptors, such as G protein-coupled receptors (GPCRs), which respond to a variety of extracellular stimuli, including hormones, have been studied for their role in GB.⁷ Even if their mechanism of action is not limited to sex hormone signaling, it seems important to investigate the role of these membrane receptors in gliomagenesis, as their targeting is increasingly showing an effect on the environment, particularly the immune system.

This review updates over the last 5 years the key role of nuclear hormone receptors and focuses on the emerging involvement of membrane receptors in GB genesis, progression, and response to treatments (Figure 1). PubMed and ClinicalTrials databases were searched during June 2025 using keywords “Glioblastoma” or “Glioma” and each “hormone receptor.” Reviews and research articles published between January 2020 and June 2025 were selected, with a few exceptions published between 2018 and 2020 if no more recent data were available: reviews were used to set the background of pre-existing knowledge, whereas original articles were deeper analyzed by all 3 authors for an update (Table 1). Publications that address the role of hormones in a multiscale and translational perspective in both in vitro and in vivo models were considered particularly relevant (Table 2).

Figure 1.

Nuclear and membrane hormone receptors orchestrate key biological responses in GB. Overview of the impact of nuclear hormone receptors and several classes of GPCRs (rhodopsin, adhesion, frizzled/taste2) on key cancer hallmarks (proliferation, migration, invasion, motility, tumor growth, tumor progression, angiogenesis, and immunomodulation) in GB based on articles published from 2020 to 2025. Nuclear hormone receptors direct modulation of genomic processes or trigger activation of indirect nongenomic signaling cascades, namely PI3K/Akt, mTOR, Wnt/b-catenin, NF-κB, and JAK-STAT3. Whereas signaling mechanisms of GPCRs remain largely unexplored in GB, they are well documented in various cancer: these membrane-bound receptors activate heterotrimeric G proteins and downstream signaling pathways like cAMP/PKA, PLC/IP3/DAG/PKC, PI3K/Akt, Wnt/b-catenin, Hippo-YAP/TAZ, and MAPK/ERK. This figure was created using Biorender.com. AR, androgen receptor; ER, estrogen receptor; GB, Glioblastoma; GPCR, G protein-coupled receptor; GPCRs, G protein-coupled receptors; GPER, G protein-coupled estrogen receptor; GR, glucocorticoid receptor; mPR, membrane progesterone receptor; MR, mineralocorticoid; NK, neurokinin; PR, progesterone receptor.

Table 1.

Pubmed search strategy and GB models associated with each cited publication: the articles that describe the role of hormones or compounds in both in vitro and in vivo models are considered particularly relevant and cited in bold

Keyword “glioblastoma” OR “glioma” AND “…”	Database mining	Cells cultured in vitro		Rodent models		Patients samples	Clinical trial	Review articles
		Established cell lines (murine or human)	Primary cell line	Immuno-deficient	Immuno-competent		Epidemiological studies
GR/MR	Orda et al. 202411	Aldaz et al. 20218	Gonzales-Aponte et al. 2025  10	Gonzales-Aponte et al. 2025  10	Gonzales-Aponte et al. 2025  10	Aldaz et al. 20218
		Nakatani et al. 20169
		Gonzales-Aponte et al. 2025  10
AR	Chang et al. 202228	Zalcman et al. 201823		Zalcman et al. 201823	Zhao et al. 2021  30	Zalcman et al. 201823		Kairemo et al. 202325
	Fariña-Jeronimo et al. 202229	Zalcman et al. 202127		Zhang et al. 202422	Lathia et al. 2024  35	Zalcman et al. 202127		Xiao et al. 202436
	Zhang et al. 202422	Siminska et al. 202226		Zalcman et al. 2023  31		Lysiak et al. 202224
	Felici et al. 202520	Zhao et al. 2021  30		Li et al. 202334		Siminska et al. 202226
		Chang et al. 202228		Lathia et al. 2024  35		Zalcman et al. 2023  31
		Zalcman et al. 2023  31
		Yavuz et al. 202432
		Zhang et al. 202422
		Li et al. 202334
		Lathia et al. 2024  35
ER	Hirtz et al. 202239	Simińska et al. 202438	Liu et al. 201844	Liu et al. 201844		Simińska et al. 202438	Daswani and Khan 202137
		Hönikl et al. 202040	Sareddy et al. 202145	Sareddy et al. 202145		Hönikl et al. 202040
		Qu et al. 201941	Zhou et al. 201946	Zhou et al. 201946		Qu et al. 201941
		Qu et al. 202242		Zhang et al. 2021  138		Liu et al. 201844
		Li et al. 202343		Pratap et al. 2023  139
		Liu et al. 201844
		Sareddy et al. 2021  45
		Zhou et al. 201946
		Zhang et al. 2021  138
		Pratap et al. 2023  139
PR/mPR	Del Moral-Morales et al. 202016	Dumitru et al. 2023  19				Dumitru et al. 2023  19	Dumitru et al. 2023  19	Llaguno-Munive et al. 202113,14
		Del Moral-Morales et al. 202016						Cahill and Neubauer 202117
								Bello-Alvarez et al. 202212
								Thomas et al. 202215
GPER	Guo et al. 202350	Hirtz et al. 2022  51	Hirtz et al. 2022  51	Hirtz et al. 2022  51		Hirtz et al. 2022  51
	Hirtz et al. 202239	Hirtz et al. 202152		Aguilar-Garcia et al. 2023140				Fuentes and Silveyra 201947
	Hirtz et al. 202152	Peña-Gutierrez et al. 202256						Xu et al. 201953
		Gonzales de Valvidia et al. 201957
		Gutierrez-Almeida et al.202259
		Aguilar-Garcia et al. 2023140
		Mendez-Luna et al. 2025141
CXCR4		Carmo et al. 201064			Alghamri et el. 2022  70	Dadgar et al. 202572	Smith et al. 201467	Wu et al. 202365
		Alghamri et el. 2022  70			Wei et al. 202571		Thomas et al. 201968	Würth et al. 201466
							Cao et al. 202469
CCR1		Zeren et al. 202373
CCR5	Pant et al. 2024  75	Zhao et al. 202574
					Pant et al. 2024  75
CB1/CB2	Costas-Insua and Guzman 202378	Taha et al. 202577					Twelves et al. 202181	Rocha et al. 201480
		Kim and Ghil 202579					Bhaskaran et al. 202482
DRD1	Yang et al. 2020  84	Yang et al. 2020  84	Yang et al. 2020  84	Yang et al. 2020  84				Rosas-Cruz et al. 202187
			Xue et al. 2024  86			Xue et al. 2024  86
				Xue et al. 2024  86
DRD2/3	He et al. 2021  88	He et al. 2021  88	He et al. 2021  88	Jeon et al. 2023  85	He et al. 2021  88	Jeon et al. 2023  85	Arrillaga-Romany et al. 202089
		Mubeen et al. 202490	Wang et al. 2023  92	Wang et al. 2023  92	Shi et al. 2023  91	Hong et al. 2025  95
		Shi et al. 2023  91	Williford et al. 202194	Williford et al. 202194	Wang et al. 2023  92	Wang et al. 2023  92
		Wang et al. 2023  92	Hong et al. 2025  95	Hong et al. 2025  95	Liu et al. 202193
		Liu et al. 202193
NK1R		Muñoz et al. 2022102				Mehboob et al. 202297	Krolicki et al. 2019100, 2023101
		Ghahremani et al. 2021104						Afshari e al. 2021103
		Mehrabani et al. 2021105						Mishra et al. 202196
		Rezaei et al. 2022106
		Ebrahimi et al. 2023107
MC4R		Vaglini et al. 2018  110		Vaglini et al. 2018  110		Vaglini et al. 2018  110		Caruso et al. 2013109
GPR133	Frenster et al. 2020117		Frenster et al. 2021118			Frenster et al. 2020117
GPR56		Ganesh et al. 2022,  120  2023  121				Ganesh et al. 2022  120		Buzatu et al. 2023,113 2024114
ELTD1				Zalles et al. 2022122				Langenhan 2023115
	Safaee et al. 2022125	Safaee et al. 2022125	Ravn-Boess et al. 2023123	Ravn-Boess et al. 2023123				Nair et al. 2021116
CD97	Zhou et al. 2024  127	Zhou et al. 2024  127	Eichberg et al. 2021124	Slepak et al. 2023126				Stephan et al. 2021112
(ADGRE5)			Slepak et al. 2023126	Zhou et al. 2024  127
			Zhou et al. 2024  127
FZD7	Phon et al. 2023129	Dreyer et al. 2023  130	Dreyer et al. 2023  130	Dreyer et al. 2023  130				Schiöth et al. 2005128
	Sun et al. 2025131
TAS2R	Costa et al. 2025  132					Costa et al. 2025  132

Abbreviations: AR, androgen receptor; ER, estrogen receptor; FZD, frizzled; GPER, G protein-coupled estrogen receptor; GR, glucocorticoid receptor; mPR, membrane progesterone receptor; MR, mineralocorticoid; NK, neurokinin; PR, progesterone receptor.

Table 2.

Detailed information from the most relevant articles published from January 2020 to June 2025

Keyword “glioblastoma” OR “glioma” AND “…”	Article	Number of authors	Database mining	Cells cultured in vitro		Rodent models		Patient samples	Main findings
				Cell lines (murine or human)	Primary cell line	Immuno-deficient	Immuno-competent
GR/MR	Gonzales-Aponte et al. 2025  10	9		GL261; LN229	Human B165	Nude orthotopic	C57/Bl6 orthotopic		Glucocorticoids ↑ GB growth in a circadian-dependent manner Loss of glucocorticoid signaling ↓ GB growth
AR	Zhao et al. 2021  30	16		U138; U87; LN229	Murine MGPP-3		Orthotopic		AR antagonists ↓ GB proliferation and target cancer stem cells in vitro and in vivo
	Zalcman et al. 2023  31	6		U87 ZH-161		Nude orthotopic			AR antagonists optimized for BBB crossing slow GB growth more potently than TMZ
	Lathia et al. 2024  35	16		GL261 SB28		SCID orthotopic ± castration	C57BL/6 orthotopic ± castration ±RAG1−/−; ±GRflox		Castration ↑ tumor growth into the brain Androgens drive anti-tumor immunity
ER	Sareddy et al. 2021  45	9		U87; U251; LN229	Human GSC080409, GSC101310, GSC111010, GSC040815	Nude orthotopic			ERβ overexpression or ERβ agonists ↓ the GB stem cells mediated tumor growth and ↑ mice overall survival
	Zhang et al. 2021  138	7		U87; LN18; U251; LN229; SVG p12		Nude heterotopic			Toosendanin blocks the PI3K/Akt/mTOR signaling and triggers cell cycle arrest, apoptosis and invasion inhibition
	Pratap et al. 2023  139	15		U87; U251	Human GSC-090909, GSC-031417, GSC-040815, GSC-082209, GSC-101310, GSC-111010, GSC-012015	SCID heterotopic	C57BL/6 orthotopic		ERβ agonist exposure is well tolerated and GB cell survival in vitro and in vivo
PR/mPR	Dumitru et al. 2023  19	11		H4; U343; U251	Human neutrophils from donor blood			Hannover cohort Magdeburg cohort	PGRMC1 ↑ tumour-related inflammation and ↑ the progression of GB
GPER	Hirtz et al. 2022  51	6		U87; U251	RADH87	Nude heterotopic		Human GB samples	↑ Lipid and steroid synthesis pathways ↓ Tubulin polymerization ↓ Tumor size and Ki-67 immunostaining
CXCR4	Alghamri et al. 2022  70	33		RPA; OL61; DF-1; HF2303			C57BL/6 orthotopic		Encapsulation with SPNP coated with the transcytotic peptide iRGD (AMD3100-SPNPs) sensitize the tumor to radiotherapy and to anti-GB immunity
CCR5	Pant et al. 2024  75	18	TCGA CGGA				C57BL/6 orthotopic		Administration of BMS-687681 ↑ Survival Synergizes with anti-PD-1 therapy
DRD1	Yang et al. 2020  84	10	TCGA	U87; U251	GB primary cultured cells	Nude heterotopic			Lower expression in GB and low expression is linked to a low survival DRD1 agonist ↓ Cell growth and disrupts autophagic flux Combination of SKF83959 and TMZ leads to a synergistic therapeutic effect
	Xue et al. 2024  86	22			GG16; P3; BG5; BG7	Nude orthotopic			SKF83566, a DRD1 antagonist, potentially targets the invasion-related genes SKF83566 ↑ anti-tumor activity
DRD2/3	Jeon et al. 2023  85	21			GB primary cultured cells	Nude orthotopic			↑ DRD2 Expression in GB DRD2 signaling ↑ GB stem-like cells and GB growth by activating MET Inhibition of DRD2 ↑ DRD2-TRAIL receptor interaction and cell death
	He et al. 2021  88	11	TCGA	GL261	HK-374; HK-382		C57BL/6 orthotopic		DRD2 antagonist ONC201 ↑ antitumor activity ↑ the efficacy of radiation without increasing toxicity
	Shi et al. 2023  91	13		U87; T98G; LN229; A172; U118; GL261			C57BL/6 orthotopic		DRD2 level ↑ by TMZ DRD2 antagonist haloperidol ↑ ferroptosis and ↑ TMZ efficacy
	Wang et al., 2023  92	11		GL261; U251; U87	GB primary cultured cells	Nude orthotopic	C57BL/6 orthotopic	Human GB samples	Chronic stress ↑ DRD2 in GB DRD2 inhibitor combined with TMZ synergistically ↓ growth
	Hong et al. 2025  95	16			GB primary cultured cells	Nude orthotopic		Human GB samples	DRD2 and DRD3 expressions ↑ in GB DRD2/3 antagonist combined with TMZ ↓ invasiveness and stemness Combining PER and TMZ ↓ growth
MC4R	Vaglini et al. 2018  110	9		U87; U118		Nude heterotopic		Human GB samples	Selective inhibition ↑ antiproliferative and pro-apoptotic effects Combined with TMZ exhibits a highly synergistic effect on cell viability and significantly ↓ tumor volume
GPR56	Ganesh et al. 2022  120	13		U373; U251; U87				Human GB samples	Heterogeneous expression of GPR56 with lowered expression in hypoxic regions Involved in the mesenchymal transition
CD97	Zhou et al. 2024  127	15	TCGA; CGGA; REMBRANDT	U87; U251; 293T; GL261	GB primary cultured cells	Nude orthotopic			Maintain the tumorigenic capacity of GSCs CD97-targeted CAR Th9 cells ↑ cytotoxic activity and ↑ survival
FZD7	Dreyer et al. 2023  130	9		U251; LN229	PDX	NOD/SCID orthotopic			FZD7 depletion ↓ tumor growth and ↑ overall survival
TAS2R	Costa et al. 2025  132	10		U87; U373				Human GB samples	20 out of the 26 human TAS2Rs present and active in GB cells

Abbreviations: AR, androgen receptor; BBB, blood–brain barrier; ER, estrogen receptor; GB, glioblastoma; GPER, G protein-coupled membrane estrogen receptor; GR, glucocorticoid receptor; GSC; glioblastoma stem cell; mPR, membrane progesterone receptor; MR, mineralocorticoid; PDX, Patient derived xenograft; PER, perphenazine; PR, progesterone receptor; SPNP, synthetic protein nanoparticle; TMZ, temozolomide.

Part 1: Nuclear Hormone Receptors and GB

Nuclear hormone receptors include mineralocorticoid (MR)/glucocorticoid receptors (GRs), progesterone receptors (PRs), androgen receptors (ARs), and estrogen receptors (ERs). Here, we will examine the main advances made in nuclear hormone receptors targeting and highlight the most promising compounds currently targeting these receptors for the treatment of GBs (Table 3).

Table 3.

Nuclear hormone receptor-targeting compounds in GB—cellular impact overview published over the last 5 years

Target	Compound	Action	Model	Key outcomes	PubMed/Clinical Trial references
MR	Aldosterone	Agonist	In vitro	↓ Growth	Aldaz et al. 20218
	Spironolactone	Antagonist	In vitro	↑ Proliferation ↑ Radioresistance
GR	Dexamethasone	Agonist	In vitro (T98G)	↑ Proliferation ↑ Radioresistance	Aldaz et al. 20218
PR	Mifepristone (RU486)	Antagonist	In vivo syngeneic (rat) orthotopic xenograft model	↓ Tumor proliferation in combination with TMZ	Llaguno-Munive et al. 202014
AR	Enzalutamide	Antagonist	In vitro	↓ Cell viability	Zalcman et al. 202127
	Enzalutamide	Antagonist	In vitro	↑ Apoptosis	Chang et al. 202228
	Enzalutamide	Antagonist	In vivo orthotopic xenograft model	↑ Survival	Zalcman et al. 202331
	Enzalutamide	Antagonist	In vitro + syngeneic orthotopic xenograft model	↓ GSC population ↓ GSCs density ↑ survival	Zhao et al. 202130
	Bicalutamide	Antagonist	in vivo orthotopic xenograft model	↑ Survival and synergized with TMZ with a more soluble formulation	Zalcman et al. 202331
	S4	Selective androgen receptor modulator (SARM)	In vitro	↓ Cell survival, ↓ Clonogenicity, ↓ Migration, ↑ Apoptosis, ↑ Senescence, ↑ ROS production	Yavuz and Demircan 202432
	TE5	Synthesized from the antagonist Tanshinone IIA	In vitro + in vivo orthotopic xenograft model	↑ Cell cycle arrest ↑ Anti-tumour activity	Zhang et al. 2024 33
ERβ	Liquiritigenin	Agonist	In vitro (GSC) + in vivo orthotopic xenograft model	↓ Cell viability, ↓ Neurosphere formation, ↑ Apoptosis, ↓ Tumor growth	Sareddy et al. 202145
	LY500307	Agonist
	TSN (Toosendanin)	Modulator	In vitro + in vivo orthotopic xenograft model	↑ ERβ/p53-mediated apoptosis, ↓ Tumor size ↓ PI3K/Akt/mTOR signaling pathway	Zhang et al. 2021138
	CIDD-0149897	Agonist	In vivo orthotopic xenograft model	↓ Tumor volume, ↑ Survival	Pratap et al. 2023139

Abbreviations: AR, androgen receptor; ER, estrogen receptor; GR, glucocorticoid receptor; MR, mineralocorticoid; PR, progesterone receptor.

Mineralocorticoid/Glucocorticoid Receptors

Mineralocorticoid is a key component in the regulation of electrolyte balance, blood pressure, and fluid homeostasis. It is also implicated in various pathological processes, including gliomagenesis. Using Rembrandt and TCGA low-grade glioma (LGG) or GB cohorts, Aldaz et al.⁸ showed that MR expression decreases with glioma grade and that low MR expression is associated with tumor progression and poor prognosis. However, these data should be qualified by glioma subtype, since, unlike in LGG, classical or mesenchymal GB, a high MR expression is of good prognosis in the proneural GB subtype. The authors also addressed the impact of MR activity in GB cell lines and conclude that the MR agonist aldosterone tended to reduce growth, whereas the MR antagonist spironolactone triggered proliferation and radioresistance. Furthermore, the involvement of MR was explored in the context of dexamethasone (DEX) administration, a GR agonist frequently used to reduce cerebral edema and thus symptoms of glioma patients. Unlike what was previously achieved with C6 murine glioma cells, GR activation promoted proliferation and stemness in some human GB cell lines in cooperation with spironolactone-dependent MR inhibition.^8,9

More recently, the key role of circadian timing for glucocorticoid release and synchronized gene expression as a driver for GB tumor growth/regression was highlighted. Unlike in other cancers, murine or human GB cells maintain a circadian clock and synchronize to the host via GR signaling.¹⁰ Therefore, daily glucocorticoid signaling promotes GB growth and accelerates disease progression, suggesting that a precise timing of DEX administration could either support or repress tumor growth, regardless of tumor type and host immune status. In conclusion, MR activation and chronopharmacological fine-tuning of glucorticoid administration could be a promising way to combine anti-inflammatory properties and anti-tumor effects.

Progesterone Receptor

A recent in silico study identified hub genes of various conserved glioma signaling modules and the key role of PI3K/Akt and calcium signaling pathways. Drug candidates that could be used to regulate the expression of those genes were selected. This analysis pointed out the potential role of the PR agonist norgestimate and synthetic progestogens (ethisterone and nomegestrol) as glioma signature modulators.¹¹ These agonists should be validated in vitro and in vivo. Like estrogens, progestogens and their associated signaling are suspected of protecting against the development and aggressiveness of gliomas. High doses of progestogens appear to inhibit GB development, mainly via repression of the nuclear PR isoform PR-B and decreased expression and activity of EGFR (Epidermal Growth Factor Receptor) and the PI3K/Akt/mTOR (Phosphatidyl-Inositol-3-Kinase/Protein Kinase B/mammalian Target Of Rapamycin) and Wnt/β-catenin signaling pathways. Nevertheless, PR expression was reported to be higher in GB than grade II gliomas and normal brain. Functional evidence indicates that low/physiological concentrations of progesterone and its metabolites, allopregnanolone and 5α-dihydroprogesterone, activate transcriptional activity of PR and/or PR/cSrc (cellular proto-oncogene tyrosine-protein kinase) interaction and subsequent rapid nongenomic signaling that could enhance proliferation and invasion.¹² By blocking the capacity of progesterone to stimulate the growth, migration and invasion of human astrocytoma cell lines (U373 and D54), the PR inhibitor mifepristone (RU486) was highlighted as a promising adjuvant drug in the treatment of GB.^13,14

Besides nuclear PRs, membrane progesterone receptors (mPRα to ε) trigger progesterone and allopregnanolone Gi-protein-dependent signaling in the brain.¹⁵ In GB, a high expression of mPRδ is of good prognosis, whereas a low expression of mPRε predicts better survival, especially in men. Both are downregulated by progesterone in GB cells.¹⁶ Other nonclassical receptors that mediate the nongenomic responses to progesterone are PGRMCs (Progesterone Receptor Membrane Component), which are members of the cytochrome b5-related membrane-associated progesterone receptor family. Both PGRMC1 and PGRMC2 subtypes are expressed in reproductive tissues, especially in granulosa cells, where they solely mediate progesterone response.¹⁷

PGRMC1 is also expressed in various regions of the healthy brain, where it participates in steroid response, metabolic control, survival, as well as synaptic dysgenesis and cognitive decline in Alzheimer’s disease.¹⁸

Recently, Dumitru et al.¹⁹ demonstrated the key role of PGRMC1 in GB cells and their immune microenvironment. PGRMC1 is highly expressed in GB compared to other cancer types, but low PGRMC1 expression predicts better overall and progression-free survival. Knockdown of PGRMC1 in GB cells triggers a lower metabolic activity, proliferation, and invasion ability, associated with downregulation of ITGB1 and TCF1/7 markers. No clear association between PGRMC1 knockdown and response to GB therapy is established. However, PGRMC1 level modulates GB cells/neutrophil interactions, suggesting that GB tissues with a high PGRMC1 expression are more likely to recruit neutrophils than tissues with low levels of PGRMC1. Overall, low PGRMC1 expression and activity were identified as a good prognosis marker in GB, which mediated critical tumor cell intrinsic functions and their interplay with the immune environment. In this context, targeting PGRMC1 may foster the development of new therapeutic strategies for the treatment of GB.

Androgen Receptor

In a machine learning study that compares the exposome of GB patients and controls, endogenous testosterone level was recently identified as a potential risk factor for developing a GB.²⁰ Androgen exposure (testosterone or dihydrotestosterone) is described as enhancing GB cell proliferation, invasion, and migration and promoting GB immune evasion through the stimulation of AR signaling.²¹ However, the expression of AR is not of overall survival prognostic value for GB patients.²² In a reference review, Zalcman et al.²³ reported that the nuclear AR gene is amplified in 27% of GB specimens from men and 38.2% from women. Compared to normal brain samples, AR-RNA is overexpressed (>2.5-fold) in 93% of GB samples. Thirty percent of the GB also express a constitutively active AR-splice variant (AR-V7/AR3).²³ Łysiak et al. confirm that AR copy number and mRNA expression level do not differ between sexes but show from TCGA-GBM database analysis that survival probability correlates with a low AR expression in females, whereas with a high AR expression in males. Moreover, promoter methylation of AR is partly sex-specific and associated with AR mRNA expression. Gene set enrichment analysis also points toward a sex-dependent association between AR expression and functionality, even if AR expression significantly associates with only 1 gene set enrichment, DNA repair genes in males, but not in females.²⁴ AR-protein is induced (>2-fold) and detectable by [18F]FDHT-PET imaging in 56% the GB samples.^23,25 Its expression is higher in the enhancing tumor region and in the peritumoral region with no significant differences between men and women.²⁶

Moreover, knockdown of AR expression or pharmacological inhibition of AR by enzalutamide treatment triggers cell apoptosis in vitro and regression of subcutaneous xenografted tumors, suggesting that both AR expression and activity support gliomagenesis.^23,27,28 Indeed, AR activity is associated with worse prognosis and shortened patient survival.²⁹ Therefore, enzalutamide could be of interest for targeting GB stem cell (GSCs).³⁰ The anti-tumor efficacy of enzalutamide and another AR agonist, bicalutamide, was confirmed in U87 or ZH-161 intracranially implanted in nude mice with a dose-dependent extension of survival. Moreover, treatment with a new and more soluble formulation of bicalutamide improved preclinical model survival and synergized with TMZ.³¹

Since EGFR was shown to drive AR phosphorylation and its consecutive androgen-independent activation in several types of cancer, Zalcman et al.²⁷ examined the relationship between both receptors. AR and EGFR gene expressions correlated in GB tumor samples, and EGFR or EFGRvIII variant overexpression stimulated AR expression, nuclear translocation, and downstream Akt-dependent signaling in GB cells in vitro. Conversely, the EGFR inhibitor afatinib blocked AR nuclear translocation and downstream signaling, and the combination of afatinib and enzalutamide yielded improved efficacy against GB cell proliferation.²⁷

This anti-tumor effect of AR blockage led to the development of multiple strategies to inhibit AR activity in GB in vivo.

Yavuz and Demircan³² explored the potential anti-tumor properties of S4, an aryl propionamide-derived selective AR modulator with a high binding affinity to AR. High doses of S4 appear to decrease LN229 and U87 survival, clonogenicity, migration, and cell cycle key gene expression while stimulating apoptosis, senescence, and reactive oxygen species production. Even if the effect is less obvious, S4 seems to effectively limit the TMZ-resistant U87 cell tumorigenicity. No data are available in vivo.

Zhang et al.³³ designed a novel L-shaped ortho-quinone analog of tanshinone IIA (TE5), a fat-soluble active compound from Salvia miltiorrhiza, that binds AR and enhances its degradation through the proteasome. TE5 also triggers PI3/AkT-dependent cell cycle arrest in vitro and anti-tumor activity in subcutaneous xenografted mice.

Li et al. aimed to target heat shock 27 protein (HSP27), the main chaperone protein that stabilizes AR. They identified 2 derivatives of N-(3-((2,5-dimethoxybenzyl)oxy)-4-(methylsulfonamido) phenyl)-4-methoxybenzamide), with improved blood–brain barrier (BBB) penetration that inhibited HSP27 chaperone activity and consequently lowered AR and Arv7 protein levels in GB cells. AR misshaping/destabilization triggered inhibition of U87 and T98G cell proliferation in vitro and slower growth of subcutaneously xenografted tumors.³⁴

Taken together, these publications underscore the relevance of new therapeutic strategies targeting directly or indirectly AR activity in combination or not with AR knockdown or standard chemotherapy.

Conversely to previous studies, Lathia et al.³⁵ indicated that when assessed in immunocompetent and orthotopic murine models, androgen signaling loss accelerates GB growth. They demonstrate that AR functionality sustains male anti-tumor immunity. Indeed, castration leads to hyperstimulation of the hypothalamus/pituitary axis, enhanced ACTH production, adrenal gland stimulation, and elevated serum glucocorticoid levels, resulting in a systemic attenuation of T-cell function and thus ineffective tumor control. These data are in line with previous work indicating that steroid hormones modulate both GSCs survival/undifferentiated phenotype and their immune microenvironment in a sex-dependent manner.^4,35,36 Consequently, further assessments of androgen signaling impact in GB and their relationship with therapeutic strategies and patient survival should be addressed in an immunocompetent context, considering the entire tumor micro- and macro environment.

Estrogen Receptors

In GB, the ambivalent role of estrogen signaling has been extensively studied and appears to depend on sex, dose, nature of estrogenic compound, and the relative expression of a combination of receptor isoforms. The great variety of available isoforms and their respective contributions are rarely studied, leading sometimes to contradictory results.^2,21 Nevertheless, nuclear ER expressions have been related to culture conditions in vitro, glioma grade, patient survival, and response to treatment.³⁷

Simińska et al.³⁸ examined the expression of ESR1 and ESR2 genes corresponding to ERα/ERβ proteins in U87 cells cultured in various stress conditions (hypoxia, nutrient deficiency, or necrotic conditions) as well as in various GB tumor areas (enhancing region, tumor core, or peritumoral tissue). ESR1 mRNA is slightly induced by hypoxia, but the ERα protein remains in the cytoplasm, probably inactive, in U87 GB cells as well as in tumor sections of both sexes. Conversely, ESR2 mRNA seems to be downregulated by hypoxia and nutrient deficiency, and ERβ protein localizes into the nucleus in enhancing and peritumoral tumor regions in males and peritumoral area only in females, suggesting a possible transcriptional activity. In this study, no assessment of aromatase (CYP19 gene) expression or activity was performed. Hirtz et al. described an association between low ESR1 mRNA expression and better overall survival in IDH-wt grade glioma (now renamed as GB). In females, ESR1 gene expression also correlated with immune response and T-cell activation gene set enrichment. In males, low CYP19 expression associated with survival modulation of cell adhesion potential.³⁹

Conversely, the expression of the ERα canonical protein (66 kDa) lowers with grade, but its high expression, combined or not to aromatase one is associated with longer survival in GB patients of both sexes. In vitro, estradiol pretreatment of GB cells also improved TMZ sensitivity.⁴⁰ Recently, ERα36, the 36kDa ERα variant that can mediate cell proliferation through estrogen or anti-estrogen signaling in different cancer cells, was detected in GB tumor samples and cell lines. ERα36 modulates tamoxifen- or estrogen-dependent proliferation of GB cells.⁴¹ Qu et al.⁴² showed that low concentrations of estrogen trigger ERα36/EGFR/SRC/MAPK nongenomic signaling. Moreover, ERα36/EGFR downregulation impaired growth and invasion of U87 and U251 cells. The ERα36 modulator SNG162 targets ERα36 nuclear location and thus prevents GB cell invasion.⁴³ Taken together, these data highlight the anti-tumoral role of ERα66 versus the pro-tumoral impact of ERα36 in GB and suggest that its modulation could be a new way to prevent tumor growth and aggressiveness.

ERβ has multiple isoforms, each with distinct roles in GB progression. ERβ2 and ERβ4 expressions are relatively low in GB, and their involvement in tumor control remains to be determined. ERβ1 is moderately expressed in GB cells and considered antitumoral through suppression of mTOR/NF-κB/JAK-STAT3 signaling. In murine xenograft models, re-expression of ERβ1 extends survival relative to controls. Conversely, ERβ5 is upregulated in GB, activates mTOR/NF-κB/JAK-STAT3 signaling, and promotes malignancy through enhancement of anchorage-independent growth, migration, and invasion.⁴⁴ In preclinical models, ERβ5-expressing tumors shorten survival compared to ERβ1-expressing ones. Moreover, the ratio of ERβ1 to ERβ5 influences GB behavior since ERβ1 overexpression may antagonize ERβ5 oncogenic effects. Overall, Sareddy et al.⁴⁵ demonstrated that ERβ overexpression and/or activity in GB cells enhance DNA damage response, apoptosis, sensitivity to DNA-damaging compounds like TMZ and reduce GSCs viability, renewal, and proliferation.⁴⁶ From a translational point of view, several compounds that enhance ERβ1 and inhibit ERβ5 signaling or shift the isoform balance were designed to counteract GB. These compounds remain strictly preclinical to date, except for the agonists Liquiritigenin and LY500307, which are the leading candidates moving toward human trials in GB, which benefit from nonglioma clinical data and display good safety and BBB permeability.⁴⁵

Estrogens can bind to nuclear ERα and ERβ as well as to the G protein-coupled membrane estrogen receptor (GPER) to mediate their actions.⁴⁷ G protein-coupled membrane estrogen receptor belongs to the GPCRs membrane receptors family. Numerous studies have confirmed the real interest of GPER and other types of GPCRs in GB. In the second part of this review, we will examine the main advances made in GPCR targeting, including GPER, and highlight the most promising compounds currently targeting GPCRs for the treatment of GB.

Part 2: Membrane GPCRs and GB

GPCRs are one of the largest families of transmembrane proteins involved in signal transduction. These receptors are membrane-bound proteins with 7 transmembrane α-helices that transduce extracellular signals into intracellular responses by activating heterotrimeric G proteins. GPCRs respond to a wide variety of extracellular stimuli—such as hormones, neurotransmitters, and sensory stimuli—and activate intracellular cascades that regulate diverse physiological processes. The GRAFS classification system, proposed by Fredriksson et al.⁴⁸ in 2003, groups human GPCRs into 5 main classes: G (Glutamate), R (Rhodopsin), A (Adhesion), F (Frizzled/Taste2), and S (Secretin).

GPCRs account for almost 4% of the human genome and are prime targets in pharmacology, with about 30%-40% of drugs currently on the market acting on these receptors. In 2021, Byrne et al.7 underscored the relevance of targeting these receptors for the treatment of GB while there were no approved therapies targeting GPCRs in GB. Apart from GPER, the other GPCRs have not yet been studied in terms of sex differences. Nonetheless, the crucial role of these receptors in GB is well established. Several recent studies have highlighted the growing interest of GPCRs in gliomas, since a 13GPCR-gene signature included 9 genes upregulated in high-grade glioma (CELSR1, F2RL2, FZD1, FZD2, FZD5, FZD7, GPR107, HRH1 and P2RY1) and 4 genes downregulated in high-grade glioma (GABBR1, GPRC5B, HTR2A and P2RY12) has been identified for human glioma prognosis.⁴⁹ However, few of them have been studied recently in the context of GB. Using databases, Guo et al.⁵⁰ also showed that GPCRs in combination with tumor microenvironment (TME) classification can serve as prognostic markers for GB, emphasizing that the environment has an impact on the role of these receptors in GB.

Since the WHO 2021 new classification of GBs, few, if any, studies have been published on glutamate or on secretin-type GPCRs, whereas numerous studies have confirmed the real interest of other types of GPCRs in GB. Here, we will examine the main advances made in GPCR targeting and highlight the most promising compounds currently targeting GPCRs for the treatment of GBs (Tables 4 and 5).

Table 4.

GPER-Targeting Compounds in GB—Cellular impact overview published over the last 5 years

Compound	GPER selectivity	Model	Key outcomes	PubMed references
E2	Agonist	In vitro	↑ Proliferation	Gutiérrez‑Almeida et al. 202259
Anastrozole	Aromatase inhibitor	In vivo syngeneic (rat) orthotopic xenograft model	↓ Cell number, ⌀ Tumor volume	Aguilar-Garcia et al. 2023140
G-1	Agonist	In vitro (U251 and LN229) 1 µM	↓ Proliferation, potentiated the efficacy of TMZ	Hirtz et al. 202152
		In vitro (U251 and RADH87; 1 µM or IC50 dose) + in vivo heterotopic xenograft model	↑ Lipid and steroid synthesis pathways ↓ Tubulin polymerization ↓ Tumor size and Ki-67 immunostaining	Hirtz et al. 202251
		In vitro (C6) 10 nM	↑ Proliferation	Gutiérrez‑Almeida et al. 202259
G-15	Antagonist	In vitro (U251 and LN229)	⌀ Cell proliferation and viability ⌀ Apoptosis	Hirtz et al. 202152
		In vitro (C6)	↓ Cell proliferation and viability ↑ Apoptosis	Gutiérrez‑Almeida et al. 202259
L-06 and  L-37	GPER inhibitors Synthesized from G-1- PABA	In vitro (GB and GSC)	↓ Neurospheres formation ↓ Migration	Méndez-Luna et al. 2025141

Abbreviations: GB, glioblastoma; GPER, G protein-coupled membrane estrogen receptor; GSC, glioblastoma stem cell; G-1-PABA, 3aS,4R,9bR)-4-(6-bromobenzo[d][1,3]dioxol-5-yl)3a,4,5,9b-tetrahydro-3H-cyclopenta[c] quinoline-8-carboxylic acid; TMZ, temozolomide.

Table 5.

GPCRs-targeting compounds in GB—cellular impact and clinical overview published over the last 5 years

Target	Compound	Action	Model	Key outcomes	PubMed/Clinical Trial references
CXCR4	AMD3100 (Plerixafor)	Antagonist	Clinical	No benefit of the combination of Plerixafor and TMZ and whole-brain radiation therapy or high-grade glioma (not limited to GB) patients	Cao et al. 202469/phase II clinical trial: NCT03746080
	AMD3100-SPNPs	Antagonist	In vitro + in vivo syngeneic orthotopic xenograft model	↓ Proliferation, ↑ Immunogenic cell death, sensitizing the tumor to radiotherapy	Alghamri et al. 202270
	AMD3100 (formulated into micelles)	Antagonist	In vivo syngeneic orthotopic xenograft model	In combinaison with CPI-444: ↑ Antitumor response	Wei et al. 202571
CCR1	BX471 (Berlex)	Antagonist	Murine glioma (GL261) and microglia in-vitro coculture model	↓ Microglia stimulated glioma cell invasion	Zeren et al. 202373
	MG-1-5	Antagonist
CCR2/CCR5	BMS-687681	Antagonist	In vivo syngeneic orthotopic xenograft model	↑ Mice survival	Pant et al. 202475
CB1/CB2	Nabiximols (Sativex)	Antagonist/ partial agonist	Clinical	Effect of combination of nabiximols to standard TMZ therapy on patients survival	Bhaskaran et al. 202482/phase II clinical trial: NCT05629702 (ongoing)
	SMA-WIN 55,212-2	Nonselective CB1/CB2 agonist	In vitro epithelial (LN18) and mesenchymal (A172) GB cell lines	↑ Cell toxicity	Taha et al. 202577
DRD1	SKF83959	Agonist	In vitro + in vivo heterotopic xenograft model	↓ GB growth	Yang et al. 202084
DRD1/DRD5	SKF83566	Antagonist	In vitro GSC cells + in vivo orthotopic GSC (BG5) derived xenografts model	↓ Proliferation, ↓ GSC sphere formation, ↓ Invasion	Xue et al. 2024 86
DRD2/DRD3	ONC201 (dordaviprone)	Antagonist	Patient-derived GB lines and syngeneic and patient-derived orthotopic xenograft mouse models	↓ Self-renewal, ↓ Clonogenicity, ↓ Cell viability. Combined treatment of ONC201 and radiation prolonged survival	He et al. 202188
			Clinical	Progression free-survival effect on patients with recurrent GB	Phase II clinical trial: NCT02525692 (ongoing)
	Perphenazine (PER)	Antagonist	In vitro patient-derived human GB tumorspheres + in vivo orthotopic xenograft model	Combined treatment with PER and TMZ synergistically ↓ Cell viability, prolongs survival	Hong et al. 202595
DRD2	Iloperidone (ILO)	Antagonist	In vitro	↓ Growth, ↓ Migration, ↑ Apoptosis, alone or in combination with TMZ	Mubeen et al. 202490
	Haloperidol	Antagonist	In vitro + in vivo syngeneic orthotopic xenograft model	↑ Ferroptosis, ↑ TMZ efficacy	Shi et al. 202391
	Pimozide	Antagonist	In vitro + in vivo orthotopic xenograft model	↓ Cell proliferation, delays tumor growth alone or in combination with TMZ	Wang et al. 202392
	Paliperidone	Antagonist	In vitro GB-macrophage co-culture + in vivo syngeneic orthotopic xenograft model	↓ GB Growth, ↓ GB macrophage co-culture induced PD-L1 expression	Liu et al. 202193
DDR3	SRI-21979	Antagonist	In vitro, GB cells and GB cells isolated from xenografts	↓ Cell growth, ↑ Sensitivity of GB cells to TMZ	Williford et al. 202194
	SRI-30052	Antagonist	In vitro GB cells isolated from xenografts	↓ Cell growth	Williford et al. 202194
NK1R	Aprepitant	Antagonist	In vitro	↓ Neuropeptide substance P increased ROS level	Ghahremani et al. 2021104
			In vitro	↓ Cell viability, ↓ Metabolic activity, ↓ Intracellular ROS levels	Mehrabani et al. 2021105
			In vitro	↓ Cell viability, ↓ Proliferation, ↓ ROS production	Rezaei et al. 2022106
			In vitro	↓ Cell growth, ↓ Cell migration, ↑ Apoptosis, alone or in combination with 5-ALA	Ebrahimi et al. 2023 107
MC1-4R	Bremelanotide	Agonist	In vitro	↑ Cell death	Suzuki et al. 2024111

Abbreviations: 5-ALA, 5-aminolevulinic acid; GB, glioblastoma; GSC, glioblastoma stem cell; NK, neurokinin; PER, perphenazine; ROS, reactive oxygen species; TMZ, temozolomide.

Rhodopsin-Type GPCRs and GB

R (Rhodopsin)-type GPCRs are the most numerous classes, including most hormones, olfactory, adrenergic, and dopaminergic receptors.

GPER, the Membrane G-Coupled ER

G protein-coupled membrane estrogen receptor, also known as GPR30, is encoded by the GPER1 gene. Hirtz et al.⁵¹ demonstrated, using the TCGA-LGG database, that a high GPER expression correlates with a better survival in overall population (males and females) and in females (but not males) in IDH-wt and IDH-mutant (IDH-mut) grade 3 gliomas (WHO 2016). However, no difference was observed for GPER expression between males and females. This suggests that not only GPER expression but also its activation by endogenous hormones may be linked to better survival in GB patients. This result was confirmed with the TCGA-GBM database on IDH-wt patients receiving chemotherapy and radiotherapy.⁵²

G protein-coupled membrane estrogen receptor displays pro-tumoral or anti-tumoral properties in different types of cancer, including breast, endometrial, prostate, ovarian, cervical, thyroid, lung, melanoma, and colorectal cancer.^53–55 G protein-coupled membrane estrogen receptor is expressed in U251, U87, LN229, and T98 human GB cell lines, but its expression is higher in healthy human astrocytes, in line with its good prognosis value in GB patients.^51,56

Post-translational glycosylation gives rise to 2 forms of GPER protein: a 42kDa native and a 60kDa glycosylated forms. Both are detected in GB cells in the cytoplasm, plasma membrane, and into the nucleus.⁵⁶ Hirtz et al.⁵² showed that GPER is mainly cytoplasmic in LN229, whereas it is found both cytoplasmic and associated with the plasma membrane in U251. As the N-terminal domain residue Asn44 seems critical for a mature and functional protein in the plasma membrane, the receptor may display differential functionalities in both cell lines.⁵⁷

To understand the impact of GPER in vitro, the GPER-specific agonist G-1 is widely used, as well as other ligands listed in Table 4.

Hirtz et al. first explored the role of G-1 on GB U251 and LN229 cell proliferation. G-1 triggers a tubulin polymerization blockage leading to reversible G2/M arrest. Moreover, G-1 potentiates the efficacy of TMZ, which is the current standard chemotherapy treatment (Stupp protocol, 2005⁵⁸), and both treatments extend mitotic arrest.⁵² The antagonists G-15 and G-36 did not alter cell proliferation or reverse the G-1-induced proliferation arrest, suggesting that the phenotypic effects observed with G-1 are likely independent of GPER functionality. Hirtz et al.⁵¹ also demonstrated that IC50 G-1 exposure modulates lipid and steroid synthesis pathways as well as affects division process depending on the duration of the treatment.

Another study investigated the effect of GPER on proliferation and apoptosis in C6 GB rat cells, using the agonists E2, G-1, a combination of both, and the antagonist G-15. E2 and G-1 increase GPER protein expression as well as decrease GPER mRNA expression. Namely, the antagonist G-15 decreased cell proliferation and viability by inducing apoptosis.⁵⁹

Research conducted by Hirtz et al. as well as Gutiérrez‑Almeida et al. indicated opposing effects of G-1 in GB. These differences could be explained by the G-1 dose used. Hirtz et al. used G-1 concentrations up to 1 µM, whereas Gutiérrez-Almeida et al. used lower concentrations around 10 nM.

To validate G-1 impact in vivo, Hirtz et al.⁵¹ grafted U87 cells subcutaneously in nude mice exposed to G-1 or vehicle. G-1 treatment induced an antitumor effect by decreasing the tumor size and Ki-67 immunopositivity of the tumor.

Given that the role of G-1 as a GPER agonist remains debated in the literature,^52,60 additional investigations using alternative approaches to modulate GPER expression and/or activity are required to clarify its potential pro- or antitumoral effects in GB.

Other Rhodopsin-type GPCRs, which do not bind sex hormones, are also interesting avenues for targeting GBs.

Chemokine Receptors

Chemokine receptors are involved in various cellular processes such as chemotaxis of immune cells, inflammation, migration, or proliferation⁶¹ and classified as typical GPCRs and atypical chemokine receptors. We will focus on the typical GPCRs.

Chemokine receptors are highly expressed in GB cell lines and patients tissues.⁶² Data available in public databases such as TCGA (LGG and GBM) and Ivy Glioblastoma Atlas project confirmed that the expression of many chemokine receptors is increased in IDH-wt gliomas compared to IDH-mut gliomas, namely CCR1, CCR5, CCR6, CCR10, CX3CR1, CXCR2, and CXCR4.⁶³ Antagonists targeting these receptors are therefore of great interest.

The most promising chemokine receptor in GB treatment is CXCR4. CXCR4 and its ligand CCL12 play a crucial role in inflammatory response, EMT, and angiogenesis and promote motility and proliferation of GB cells through signaling pathways, including PI3K/Akt, PLC/IP3, and ERK1/2, leading to calcium release from the endoplasmic reticulum through inhibition of adenylate cyclase and reduced cAMP production.^64–66 AMD3100 (Plerixafor) is the best-known CXCR4 antagonist with promising effects in the treatment of GB.⁶² Several clinical trials were designed to evaluate the safety and tolerability of plerixafor in combination with bevacizumab (NCT01339039)⁶⁷ or with chemo/radiotherapy combined to TMZ (NCT01977677).⁶⁸ Combination of plerixafor with chemo/radiotherapy is beneficial for patient (65% of patients had IDH-wt status) survival and improves local control of tumor recurrence.⁶⁸ More recently, a phase II clinical trial did not demonstrate any benefit on the median overall survival for high-grade glioma (not limited to GB) patients having the combination of Plerixafor and TMZ and whole-brain radiation therapy (NCT03746080).⁶⁹ To enhance the potential of Plerixafor in the treatment of GB, several studies have recently attempted to propose a new formulation of this compound to improve the BBB passage. Encapsulation with synthetic protein nanoparticles (SPNP) coated with the transcytotic peptide iRGD (AMD3100-SPNPs) led to the induction of immunogenic cell death (ICD), sensitizing the tumor to radiotherapy and to anti-GB immunity.⁷⁰ Interestingly, the combination of AMD3100 and CPI-444, an A2AR inhibitor, both formulated into micelles, improved ICD induced by AMD3100, alleviated the immunosuppressive TME, and significantly inhibited tumor growth in vivo.⁷¹ Therefore, CXCR4 targeting opens promising therapeutic opportunities for the treatment of GB. In addition, CXCR4 is overexpressed in GSCs and may contribute to GSCs maintenance.⁷ High expression of CXCR4, particularly in high-grade gliomas, was correlated with elevated uptake of molecular imaging agent targeting CXCR4. Targeting CXCR4 by peptide-conjugated radionuclide such as ⁶⁸Ga-Pentixafor will enable better diagnosis and recurrence assessment after surgery or chemoradiotherapy.⁷²

Other chemokine receptors play a role in GB tumor progression. CCR1 participates in leukocyte trafficking in normal conditions and was described as an actor of tumor progression. The main ligand for CCR1 is CCL3, even if many other chemokines have been shown to bind to and activate CCR1. Two CCR1 antagonists, BX471 (Berlex) and a novel inhibitor MG-1-5, are able to inhibit microglial-activated murine GL261 glioma cell invasion in a dose-dependent manner.⁷³

CCR5 is responsible for GB migration in TME.⁷⁴ Administration of BMS-687681, a dual antagonist of CCR2 and CCR5, improves the survival of mice bearing orthotopic GL261 tumors and synergizes robustly with anti-PD-1 therapy.⁷⁵

CXCR4 targeting is currently the most advanced compared to other chemokines receptors. Its optimization appears very promising in vitro and in preclinical models although its efficacy in patients remains to be confirmed.

Cannabinoid Receptors

Cannabinoid receptors, primarily CB1 and CB2, are GPCRs integral to the endocannabinoid system.⁷⁶ CB1, predominantly expressed in neurons, is involved in the regulation of adenylate cyclase, ion channel activity, and synaptic neurotransmitter release. In contrast, CB2, primarily localized to immune cells and pathologically altered brain regions, contributes to the modulation of inflammatory responses and cellular survival mechanisms.⁷⁷

CB1 and CB2 expressions increase with glioma grade (between TCGA-LGG and TCGA-GBM patient samples). However, these databases do not consider the new WHO 2021 classification. In the CGGA database, CB1 expression is significantly up-regulated in IDH-wt grade 4 gliomas versus IDH-mut grade 4 gliomas, while CB2 expression does not change.⁷⁸ Furthermore, activation of CB2 increases cell migration and proliferation in U87 cell line.⁷⁹ Previous studies showed that administration of THC (Δ9-Tetrahydrocannabinol), a partial CB1 and CB2 receptor agonist, and CBD (cannabidiol) had an anti-tumoral effect on the GB xenografted mouse model.⁸⁰ Subsequently, the safety and tolerability of nabiximols (Sativex; THC/CBD at 1:1 ratio) in combination with a high dose of TMZ was assessed on patients with recurrent GB (NCT01812603 and NCT01812616).⁸¹ In the same way, the safety of the THC+CBD (TN-TC11G) combination at a 1:1 ratio, adding TMZ and radiotherapy in patients with newly diagnosed GB, is in progress (NCT03529448). A phase 2 multicenter study is currently underway to assess whether the addition of nabiximols to standard TMZ therapy improves survival of patients with recurrent MGMT-methylated IDH-wt patients (NCT05629702).

Other cannabinoids, such as WIN 55 212-2, a CB1/CB2 nonselective synthetic agonist, have shown interesting antitumor effects in oral and pancreatic tumor cells.⁸³ However, the use of this molecule for the treatment of GB is limited, since it crosses the BBB only to a limited extent. Styrene–maleic acid-WIN micelles induce high cell toxicity in LN18 (epithelial) and A172 (mesenchymal) GB cells, revealing a mesenchymal-specific mechanism.⁷⁷

Currently, the best therapeutic strategy targeting cannabinoid receptors in GB is to target CB1 and CB2. However, to better describe and understand the role of each receptor, it would be interesting to find molecules that specifically target each of them.

Dopamine Receptors

Dopamine receptors (D₁-D₅) are divided into D1-like subtypes (DRD1, DRD5)—which activate Gₛ to stimulate cAMP—and D2-like subtypes (DRD2-DRD4), which inhibit cAMP via Gᵢ coupling. While crucial for neurophysiological functions, emerging evidence involves dopamine receptor signaling in GB.⁷

DRD1 expression was investigated in GB samples. In the TCGA database, GB has lower expression of DRD1 compared to normal control, and low DRD1 is linked to a low survival.⁸⁴ SKF83959, a DRD1 agonist, decreases cell growth and disrupts autophagic flux, leading to tumor cell death. Furthermore, the combination of SKF83959 and TMZ leads to a synergistic therapeutic effect both in vivo and in vitro.⁸⁴ A more recent study reported that DRD1 expression in patient-derived GB cells exhibited variability.⁸⁵ Recently, Xue et al.⁸⁶ identified SKF83566, a BBB-permeable DRD1 antagonist that potentially targets the invasion-related genes expressed in GB. SKF83566 exhibits anti-tumor activity in vitro and in orthotopic GSC (BG5)-derived xenografts in nude mice.⁸⁶

These conflicting findings highlight the limited understanding of DRD1 receptor involvement in GB and underscore the need for further research to clarify their potential therapeutic relevance.⁷

DRD2 is significantly upregulated in GB tumors relative to adjacent nontumoral brain tissue.^85,87 In recent years, numerous DRD2 antagonists have raised great interest in the treatment of GB. DRD2 antagonist ONC201 (dordaviprone) demonstrates p53-independent antitumor activity in preclinical models of GB. It also improves the efficacy of radiation without increasing toxicity in mouse models of GB.⁸⁸ A phase II clinical trial is underway to demonstrate its efficacy, particularly in patients with recurrent GB (NCT02525692).⁸⁹ DRD2 expression increases with TMZ treatment.^90,91 The combination of TMZ with the antipsychotics iloperidone, haloperidol, or pimozide, all 3 of which act as DRD2 antagonists, reduces GB cell growth and migration, enhances apoptosis, and improves TMZ efficacy in vitro and in vivo.^90–92 These effects may be mediated through MET and TRAIL receptor signaling pathways, which are, respectively, associated with cell survival, proliferation, and migration, and the induction of cell death.⁸⁵ Interestingly, the antipsychotic paliperidone inhibits GB growth in an orthotopic xenograft mice model and reduces PD-L1 expression both in GB cells and their microenvironment, suggesting that combining DRD2 antagonists with standard immunotherapy could enhance therapeutic outcomes in GB.⁹³

The expression levels of DRD 3, 4, and 5 are very low in patient-derived GB cells,⁸⁵ and DRD3 shows similar expression between GB patient samples and nontumor samples in TCGA database.⁹⁴ Nevertheless, DRD2 and DRD3 expressions are higher in tumor tissues than in the tumor-free cortex of patients with GB from the Severance dataset.⁹⁵ DRD2/3 antagonist perphenazine (PER) combined with TMZ induces cytotoxic and synergistic effects in patient-derived GB tumorspheres by decreasing invasiveness and stemness. In vivo combining PER and TMZ suppresses tumor growth in mouse orthotopic xenograft model using tumorspheres.⁹⁵ Higher levels of DRD3 mRNA and not of DRD2 and DRD4, associated with worse patient prognosis in primary MGMT unmethylated GBs. Targeting DRD3 may offer therapeutic potential in TMZ-resistant GB, as the selective DRD3 antagonists SRI-21979 and SRI-30052 inhibited the growth of both parental U251 and TMZ-resistant GB cells. SRI-21979-treated PDX-derived neurospheres trigger upregulation of genes involved in apoptotic pathway.⁹⁴

Thus, various DRD2/3 antagonists have shown promising anti-tumor effects and synergy with TMZ in preclinical models, highlighting their potential as therapeutic targets, especially in TMZ-resistant and immunotherapy-responsive GB cases. However, there is currently a lack of clinical trial results to truly see the relevance of targeting dopamine receptors in GB.

Neurokinin 1 Receptor

Neurokinin receptors—NK₁R, NK₂R, and NK₃R—are activated by tachykinins (substance P, neurokinin A, B), playing key roles in pain, inflammation, smooth muscle contraction, and immune regulation.⁹⁶ NK1R is the most studied tachykinin receptor and is more expressed in grade 4 astrocytoma and GB than in normal tissue, making it a valuable target for theragnostic approaches.⁹⁷ Substance P activation of NK1R promotes GB cell proliferation by stimulating the Erk/MAPK and Akt signaling pathways.⁹⁸ Modified substance P analogs such as DOTA-[Thi8, Met(O2)11]SP show high NK1R affinity and stability, enabling selective targeting of tumor cells and vasculature.⁹⁹ Clinical studies using targeted alpha therapy [213Bi]Bi- and [225Ac]Ac-labeled DOTA-SP demonstrate safety and potential efficacy, although 213Bi short half-life limits long-term therapeutic impact.^100,101 Actinium-225 offers a promising alternative due to its longer half-life and effective tumor cell targeting, including GB stem-like cells. Locoregional α-radioisotope delivery (intracavitary) remains a promising and evolving strategy for treating recurrent GB.

NK1R inhibition induced cell death in GAMG and U87 cells, while there was no effect on normal cells.¹⁰² Several NK1R antagonists have been studied in GB¹⁰³. Among them, aprepitant, clinically approved against chemotherapy-induced nausea, has demonstrated significant anti-tumoral activity in the GB context through oxidative stress modulation.^104–106 The combination of aprepitant and 5-aminolevulinic acid, a prodrug that elicits fluorescent porphyrins, leads to a synergistic decreased cell viability and migration and induced apoptosis in U87 cells.¹⁰⁷ Meanwhile, aprepitant-based radioconjugates targeting NK1R display high affinity in vitro but with limited specificity.¹⁰⁸

These findings highlight NK1R as a promising therapeutic target in GB, with both radiolabeled ligands and specific antagonists. However, there is a lack of in vivo data and clinical validation to confirm the therapeutic value of targeting NK1R in GB.

Melanocortin Receptor-4

Melanocortins are peptides with anti-inflammatory and neuroprotective activity. There are 5 melanocortin receptors (MCRs; MC1-5R), with only MC4R being present in astrocytes and, hence, is referred to as a neural MCR.¹⁰⁹

MC4R is expressed in GB cells and GB patient tissues, and its selective inhibition by the brain penetrant nonpeptidic antagonist ML00253764 induces antiproliferative and pro-apoptotic effects via suppression of ERK1/2 and Akt phosphorylation.¹¹⁰ When combined with TMZ, ML00253764 exhibits a highly synergistic effect on GB cell viability in vitro and significantly reduces tumor volume in vivo compared to monotherapies, with excellent tolerability.¹¹⁰ Conversely, activation of MCR by the nonselective agonist bremelanotide—clinically used to treat hypoactive sexual desire disorder—has been shown to downregulate survivin expression and promote cell death in GB cells, suggesting that MCR stimulation may sensitize GB cells to apoptotic mechanisms.¹¹¹

These results suggest that targeting MCRs, particularly MC4R, holds therapeutic potential in GB by modulating key survival pathways and enhancing the efficacy of standard treatments like TMZ. However, these data are based on a few studies and need to be supplemented by new studies on a larger sample of models.

Taken together, all these data show the central role of Rhodopsin-type GPCRs in GB progression.

The second class of GPCRs of therapeutic interest for the treatment of GB are the adhesion-type GPCRs.

Adhesion GPCR

Adhesion GPCRs (aGPCRs) form the second largest GPCR subfamily (33 human receptors), with extended N-terminal extracellular domains harboring modules like EGF (Epidermal Growth Factor), cadherin, immunoglobulin, and pentraxin for cell–cell and cell–matrix adhesion. Adhesion GPCRs have been implicated in diverse physiological and pathological processes, including immune responses, endocrine and nervous system functions, tumorigenesis, brain development, BBB formation, regulation of cerebral angiogenesis, and the maintenance of GSCs stemness.¹¹² Adhesion GPCRs can signal through canonical pathways by coupling with various G proteins, including Gαs, Gαi, Gα12/13, and Gαq. In addition, aGPCRs are also capable of G protein-independent, noncanonical signaling, as BAI1 has been implicated in Rac1-mediated signaling.¹¹² The expression of most aGPCRs is upregulated in GB, such as GPR124 (ADGRA2), GPR133 (ADGRD1), CD97 (ADGRE5), EMR2 (ADGRE2), GPR56 (ADGRG1), and ELTD1 (ADGRL4) involved in cellular migration and invasion, stem cell self-renewal, extracellular matrix remodeling, or vascularization.^113–115

In contrast, BAI1 (ADGRB1), an aGPCR with markedly reduced expression in GB compared to normal brain tissue, is thought to exert antitumor effect. BAI1 participates in canonical G protein signaling through Gαq and Gα12/13, as well as in noncanonical pathways that activate Rho signaling, promote ERK phosphorylation, and involve β-arrestin binding.¹¹² In cancer cells, BAI1 expression results in reduced tumor growth and angiogenesis. Moreover, BAI1 expression inversely correlates with tumor progression.¹¹⁶

Expression of GPR133 is higher in IDH-wt tumors than in IDH-mut tumors from patients undergoing surgical resection.¹¹⁷ This receptor promotes tumorigenesis through intramolecular cleavage, which enhances canonical signaling by facilitating dissociation of the cleaved N-terminal fragment at the plasma membrane, as demonstrated in patient-derived GB cell cultures.¹¹⁸

Expression of GPR56 in GB tumor (WHO 2016¹¹⁹) is heterogeneous with lowered expression in hypoxic regions. GPR56 is involved in the mesenchymal transition of GB.¹²⁰ A better understanding of the molecular mechanisms and pathways involved in GPR56 role in the mesenchymal transition of GB was recently established by a Multi-Omics approach.¹²¹

ELTD1 for epidermal Growth Factor Latrophilin and 7 transmembrane domain-containing protein 1. In GB, ELTD1 is upregulated in endothelial and tumor cells and is involved in angiogenesis.¹¹³ ELTD1 targeting with a monoclonal antibody led to reduced GB tumor volume, normalized vascularization, and increased animal survival in orthotopic GB xenograft model.¹²²

CD97 is highly expressed in IDH-wt GB tumors and immune cells, whereas its expression is significantly lower in IDH-mut astrocytomas.¹²³ In patient-derived GSCs, endogenous CD97 expression positively correlated with radiographic invasion pattern and in vitro invasion rate.¹²⁴ Functional studies have shown that CD97 overexpression enhances both proliferation and invasion rates of patient-derived GSCs, while CD97 knockdown decreases invasiveness in vitro.¹²⁴ Transcriptomic profiling of 14 GB tumors revealed that elevated CD97 expression is associated with activation of the mitogenic pathway and changes in the GB immune microenvironment.¹²⁵ These findings underscore the dual role of the CD97 in GB invasion and proliferation.¹²⁶ Mechanistically, CD97 promotes Warburg metabolism and activates the MAPK pathway via phosphorylation of its C-terminal tail and recruitment of β-arrestin.¹²³ Therapeutically, targeting CD97 with an antibody–drug conjugate selectively induced cell death in patient-derived GB cultures without affecting astrocytes or neural stem cells.¹²³ More recently, CD97 has been shown to maintain the tumorigenic capacity of GSCs through mTORC2–AKT signaling, and CD97-targeted CAR Th9 cells demonstrated potent cytotoxic activity in vitro and prolonged survival in mouse models.¹²⁷

Several aGPCRs are involved in key process in GB progression, and their presence at the cell membrane may represent a promising target for therapeutic application. However, only a limited number of studies in the past 5 years have investigated the effects of specific ligands on these receptors in the context of GB, and the current findings require further validation before aGPCRs can be considered accurate therapeutic targets for GB.

Frizzled/Taste2 Type GPCRs and GB

GPCR class F includes Frizzled (FZD) and Taste2 receptors (TAS2R). FZD receptors mediate Wnt signaling, influencing processes such as embryonic development, cell proliferation, and tissue homeostasis. TAS2R, on the other hand, are involved in detecting bitter compounds, contributing to taste perception and protective responses against toxins.¹²⁸ Among FZD receptors, FZD7 is the most studied in the GB context. FZD7 is upregulated in brain samples from GB patients (TCGA and CGGA databases, 77% of IDH-wt patients) compared to normal brain. Among patients, FZD7 is upregulated in IDH-wt vs IDH-mut patients.¹²⁹ These results are consistent with data published by Dreyer et al.,¹³⁰ showing that FZD7 depletion significantly suppresses tumor growth and prolongs overall survival in a mouse intracranial xenograft model. A high-throughput virtual screening identified cycloartobiloxanthone, as a promising inhibitor of FZD7.¹³¹ Its interest in GB therapy has yet to be studied.

Little is known about TAS2R in GB. Recently, it was shown that 20 out of the 26 human TAS2Rs are present and active in GB cells, but the therapeutic potential of these targets has yet to be fully assessed.¹³²

To date, few studies have examined the impact of Frizzled/Taste2 GPCR signaling in GBs by studying only the expression of these receptors. Their functionality must be proven in new studies to demonstrate the relevance of targeting these receptors.

In conclusion, all these findings underscore the importance of investigating the role of GPCRs and their potential as therapeutic targets in GB. In addition to well-characterized GPCRs, emerging receptors such as the Glucagon-Like Peptide 1 Receptor, a member of the secretin family of GPCRs^133,134 and metabotropic glutamate receptor 3 (Grm3), the predominant Grm subtype expressed in GB and part of the glutamate receptor class, are gaining attention.¹³⁵ While the role of Grm3 in GB progression remains to be fully elucidated, these receptors represent promising avenues for further investigation.¹³⁶ Importantly, despite growing recognition that GB exhibits hormone sensitivity, the influence of sex on receptor expression and function has rarely been considered. A recent study demonstrated that inhibition of the GABA receptor B (GABBR) enhances survival in GB in a sex- and immune-dependent manner, further emphasizing the necessity of integrating sex as a biological variable in future research on GPCRs in GB.¹³⁷

Conclusion

The evolving classification of GB, guided by molecular profiling, marks a pivotal shift in neuro-oncology. Since most patient studies are based on databases using the WHO 2016 classification, the re-annotation of public databases and biobank samples is needed. Understanding the diverse roles of hormone receptors in both sexes also opens new frontiers in GB treatment. Besides classical steroid nuclear receptors, GPCR and noncanonical hormone signaling pathways through GPER, or cannabinoid, dopamine, and chemokine receptor-regulated processes pave the way for new therapeutic avenues to control and counteract tumor growth and invasiveness (Figure 1), targeting not only GB cells but also the tumor micro/macro environment. Nevertheless, the development and validation of ligands able to cross efficiently the BBB and challenged in immune-competent models appear crucial for the modulation of hormone/cytokine receptor activities in vivo. Continued research into receptor signaling and TME interactions in males or females not only highlights the biological complexity of GB but also emphasizes the importance of sex-specific pathways and individualized therapeutic strategies.

Conflict of Interest Statement

None declared.

Funding

A.G. is the recipient of a PhD fellowship from the University of Lorraine. The research was founded by The Cancéropôle Grand Est, Projet émergence 2025 (GLIOLIG).