Current situation and research progress of luteolin in the treatment of gastrointestinal malignant tumors

Abstract

Luteolin, known for its anti-inflammatory and antioxidant properties, has garnered attention for its potential anticancer effects. Research has shown that luteolin can modulate the proliferation, migration, invasion, drug resistance, and apoptosis of digestive tract cancer cells by targeting specific pathways. This review summarizes the current understanding of luteolin’s impact on five types of digestive tract malignancies both in vitro and in vivo, elucidates its molecular mechanisms in regulating these cancers, and highlights the existing limitations and gaps in research. This analysis aims to inform the safety assessment, enhance the bioavailability, and guide the formulation development and clinical utilization of luteolin in the context of digestive tract malignancies.

Introduction

In recent years, the global incidence and mortality rates of digestive tract malignant tumors have been on the rise, attributed to various risk factors including poor dietary habits, sedentary lifestyles, and heightened stress levels [1]. Malignant tumors affecting the digestive tract constitute a significant portion of all cancer cases, encompassing colorectal cancer(CRC), hepatocellular carcinoma(HCC), gastric cancer(GC), esophageal cancer(EC), pancreatic cancer(PC), and other malignancies related to food digestion [2]. Notably, CRC, HCC, and GC rank as the second, third, and fifth leading causes of cancer-related deaths worldwide in 2022, contributing to 9.3%, 7.8%, and 6.8% of all cancer mortalities, respectively [3]. This trend poses a substantial threat to the well-being of individuals in modern society.

Traditional treatment modalities for digestive tract malignant tumors encompass surgical resection, chemotherapy, radiotherapy, immunotherapy, targeted therapy, among others. Despite advancements in these treatments, patients often experience adverse effects stemming from the diseases and therapies, such as weakness, reduced appetite, nausea, vomiting, bloating, irregular bowel movements, hematochezia, insomnia, and poor sleep quality. These symptoms significantly impact patients’ quality of life and overall survival. Consequently, there is an urgent need to explore novel therapeutic agents and strategies to address these challenges.

In recent years, there has been a growing scholarly interest in utilizing plants for treating malignant tumors, with a particular focus on luteolin, a natural flavonoid polyphenol. Luteolin is commonly found in fruits and vegetables like peppers, carrots, broccoli, celery, and coriander [4], as well as in traditional Chinese medicinal herbs such as honeysuckle, purple perilla [5], scutellaria baicalensis, dandelion, and corn silk [6]. Its therapeutic properties include an ti-cancer, anti-inflammatory, and antioxidant effects [7]. Research on luteolin’s mechanisms of action in disease treatment has revealed its involvement in mediating various signaling pathways, such as PI3K/AKT [8, 9], MAPK [10, 11], and STAT3 [12]. These pathways contribute to inducing tumor cell apoptosis, promoting autophagy, arresting the cell cycle, inhibiting epithelial-mesenchymal transition (EMT), enhancing tumor cell peroxidation, and modulating intestinal flora distribution. These actions collectively suppress the proliferation, migration, invasion, and drug resistance of gastrointestinal tumors, providing a solid theoretical foundation and empirical support for the efficacy of luteolin in disease management.

Structure of luteolin

Luteolin is a classic flavonoid with a C6-C3-C6 skeleton, comprising two benzene rings, each bearing hydroxyl groups at positions 5, 7, 3′, and 4′, and an oxygen-containing heterocycle with a C2-C3 double bond [13] (SMILES: C1 = CC(= C(C = C1C2 = CC(= O)C3 = C(C = C(C = C3O2)O)O)O)O). With four hydroxyl groups and a C2-C3 double bond, luteolin demonstrates the capacity to chelate metal ions, inhibit peroxides, and interact with biological targets. This ability enables luteolin to modulate the activity of reactive oxygen species (ROS) scavenging enzymes, act as an antioxidant, regulate pro-inflammatory factors, and induce apoptosis or autophagy. Intriguingly, luteolin can also exhibit pro-oxidative effects and demonstrate anticancer properties under specific circumstances [14, 15] (Fig. 1B).

Fig. 1.

Structures of the flavonoids. A. Structures of Flavone; B. Structures of Luteolin; C. Structures of Apigenin; D. Structures of Kaempferol

Compared with other flavonoids such as apigenin (which contains only three hydroxyl groups), the polyhydroxyl structure of luteolin endows it with stronger binding affinity to proteins and confers protective effects against thermal denaturation. Additionally, the hydroxyl group at the 3′ position enhances luteolin’s antioxidant potential [16, 17]; in contrast to flavonoids with hydroxyl group deficiencies at positions such as 3′, 4′, and 7 (e.g., kaempferol), the presence of hydroxyl groups at the 3′, 4′, and 7 positions enables luteolin to exhibit potent immunomodulatory activity in reversing immunosuppression. Notably, the hydroxyl group at the 3′ position plays a pivotal role in mediating the biological activities of flavonoids [17] (Fig. 1).

Luteolin and colorectal cancer

Luteolin demonstrates multifaceted anticancer effects in both the prevention and treatment of CRC, with its mechanism of action showing significant dose-dependency. Yoo et al. discovered that luteolin activates the p53 signaling pathway, leading to apoptosis and cell cycle arrest in CRC cells by upregulating p53 and its target genes p21, Noxa, and Bax. Additionally, luteolin increases levels of LC3-II and Beclin 1 proteins in a p53-dependent manner [18]. Similarly, Song et al. observed that luteolin reduces the expression of p-MEK 1 and p-ERK 1/2 in CRC cells in a dose-dependent manner. This reduction is followed by upregulation of apoptosis-related proteins BAX and cleaved Caspase-3, and downregulation of Bcl-2. These findings suggest that luteolin induces apoptosis in CRC cells by inhibiting phosphorylation of the MAPK pathway. Moreover, the study indicates that luteolin downregulates DNA repair proteins, such as HMGB1, LIG, and XRCC1, while upregulating ERCC-3, resulting in DNA single-strand breaks and ultimately apoptosis. Furthermore, the research reveals that luteolin treatment decreases levels of G2-M phase-related proteins Cyclin B1 and CDC2, while increasing p-CHK1 in a concentration-dependent manner. This indicates that luteolin can induce G2/M phase arrest in CRC cells, thereby inhibiting CRC cell proliferation [10]. Potočnjak et al. demonstrated that luteolin dose-dependently suppressed the expression of Wnt3 and β-catenin in CRC cells. Moreover, luteolin decreased Bcl-2 levels in a dose-dependent manner by activating ERK, JNK, and p38 signaling pathways. This led to the upregulation of pro-apoptotic proteins Bax, cleaved-caspase 3, and cleaved-PARP, ultimately inducing apoptosis in CRC cells. Additionally, luteolin upregulated the expression of LC3B-I and LC3B-II through the activation of the ERK/FOXO3a pathway. Furthermore, it enhanced the expression of Atg7, Beclin-1, and acidic autophagy vesicles, suggesting that luteolin induced autophagy in CRC cells in a dose-dependent manner. However, it was noted that autophagy primarily served as a compensatory mechanism for apoptosis in this context [11].

Chakraborty et al. showed that luteolin is one of the best botanical compounds against metastatic CRC and that luteolin can inhibit CRC cell metastasis in a time-and dose-dependent manner by significantly reducing p-beta-catenin and inhibiting p-GSK3-beta expression. Luteolin inhibits the expression of PI3K-α and AKT1 by binding to PI3K-α and AKT1, and finally reduces CRC cell proliferation and induces its death. Luteolin can also inhibit the expression of p-50 by binding to the DNA binding domain p-50 monomer of NF-KB to limit the pro-metastatic effect of pro-inflammatory factors on CRC [9]. Similarly, Yao et al. believed that luteolin effectively inhibited the migration and invasion of CRC cells in vitro, which was related to the inhibition of PTN expression by luteolin through upregulation of miR-384. The decrease of PTN expression finally inhibited the expression of matrix metalloproteinases MMP-2, MMP-3, MMP-9 and MMP-16 related to tumor migration [19].

Ferroptosis is also one of the most important ways that luteolin exerts its anti-CRC effect. Zheng et al. found that luteolin further reduced the expression of tumor survival-related protein GPX4 by up-regulating the expression of HIC1 in CRC cells, induced lipid peroxidation by up-regulating the accumulation of total ROS and MDA, and finally induced Ferroptosis in CRC cells, while the combination of luteolin and Erastin could strengthen this process. In vivo studies also showed that luteolin significantly reduced tumor mass and volume by combining with Erastin, and significantly down-regulated the expression of Ki67 and GSH in tumor tissues. Increased MDA expression significantly induced Ferroptosis in CRC cells, which was the same as in vitro results [20].

Intestinal flora is closely related to CRC, luteolin also plays an active role in regulating flora. Pérez-Valero et al. found that luteolin intraperitoneal injection can significantly reduce the incidence of CRC tumor in mice. By detecting the bacterial species in the intestinal tract of mice, luteolin can increase some bacterial species associated with good CRC prognosis in the intestinal tract, such as Prevotella, Butyricoccaceae, Clostridia vadin BB 60 and Muribaculum, etc., and reduce harmful bacterial populations such as: Clostridiaceae, Actinomycetota, Christensenellaceae, Eggerthellaceae, Anaerovoracaceae and Clostridia UCG-014 reduce intestinal inflammation, reduce the risk of CRC cell DNA mutation and prevent CRC by changing the distribution and quantity of colorectal flora [21].

When luteolin is used in combination with some chemotherapeutic drugs, luteolin can mediate multiple pathways such as cell apoptosis, autophagy, and inhibition of angiogenesis, improving the sensitivity of CRC cells to chemotherapeutic drugs. Özerkan et al. found that luteolin promoted apoptosis of CRC cells by reducing mitochondrial membrane potential, inhibited cisplatin resistance of CRC cells, and enhanced inhibition of cisplatin resistant CRC cells [22]. In addition, Jang et al. found that luteolin could up-regulate p53-dependent apoptosis, inhibit heme oxygenase-1 (HO-1)-mediated cell protection, promote apoptosis ratio of CRC cells and enhance drug sensitivity of CRC cells to oxaliplatin when luteolin was used in combination with oxaliplatin, suggesting that luteolin and oxaliplatin had synergistic effect [8]. Erdoğand et al. found that luteolin combined with 5-FU could significantly reduce the expression of P53, Bcl-2 and AKT mRNA in CRC cells, reduce the expression of Bcl-2, mTOR and AKT protein, significantly increase the expression of P38 MAPK and PTEN mRNA, and increase the expression of Bax, p53, PTEN and P38 MAPK protein. The combination of luteolin and 5-FU significantly reduces the production of VEGF and promotes apoptosis in CRC cells by regulating PTEN/AKT/mTOR pathway, indicating that the synergistic effect of luteolin and 5-FU mediates the production of PTEN/AKT/mTOR pathway [23]. At the same time, Yang et al. found that luteolin could target to inhibit the expression of GPSM2, mediate PI3K/AKT/FOXO3 signaling pathway to further inhibit the expression of CyclinB1 and the activity of CyclinB1/CDC2 complex, promote the expression of P21 and p-CDC2, lead to G2/M arrest of CRC cells, and induce apoptosis of CRC cells by inhibiting the expression of Bcl-2 and promoting the expression of Bax and cleaved Caspase-3. The experiment also indicated that luteolin inhibited CRC cell invasion, colony formation and cell viability by inhibiting MMP9 and vimentin expression and upregulating E-cadherin expression. It should be noted that this experiment also proves that luteolin can enhance the anti-tumor effect of 5-FU by inhibiting the expression of GPSM2, PCNA and p-Foxo1a/3a in CRC cells, and proves the coordinated effect of luteolin and 5-FU [24]. Monti et al. found that luteolin could induce CRC cells to accumulate in S phase and promote apoptosis. Luteolin significantly inhibited HIF-1-dependent transcriptional activity of CRC cells by mediating the increase of HIF-1a expression, and inhibited the expression of immune escape markers CD44 and CD47 regulated by HIF-1 transcription, which increased the sensitivity of CRC cells to chemotherapy drugs. Interestingly, this study also found that luteolin can also mediate the increase of LC3-II to induce protective autophagy in CRC cells [25]. We summarize the results of luteolin on different CRC cell lines via different pathways (Table 1).

Table 1.

The results of Luteolin on different CRC cell lines via different pathways

Type of cancer	In Vitro/In Vivo	Sex	Module	Samples	Cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
CRC	In Vitro	–	–	–	HCT116	0, 10, 20, 30, 40 µM	–	p21↑, Noxa↑, Bax↑, LC3–II↑, Beclin1↑, p53↑	[18]
CRC	In Vitro	–	–	–	HCT-116 HT-29	0, 10, 20, 40 µM	–	p-MEK1↓, p-ERK1/2↓, BAX↑, Bcl-2↓, Cleaved casepase-3↑, HMGB1↓, LIG↓, XRCC1↓, ERCC-3↑, p-CHK1↑, CDC2↓, Cyclin B1↓	[10]
CRC	In Vivo	♀	BALB/c nude	12	HCT-116	0, 20, 40 mg/kg	Tail vein injection	HMGB1↓, LIG↓, XRCC1↓, ERCC-3↑, p-MEK1↓, p-ERK1/2↓	[10]
CRC	In Vitro	–	–	–	SW620	0, 1, 2, 5, 10 µM	–	Wnt3↓, β-catenin↓, p-ERK1/2↑, ERK↑, p-JNK1/2↑, p-p38↑, Bcl-2↓, Bax↑, Beclin-1↑, cleaved-caspase 3↑, cleaved-PARP↑, FOXO3a↑, LC3B-I↑, LC3B-II↑, Atg7↑, acidic autophagy vesicles↑	[11]
CRC	In Vitro	–	–	–	HCT-15	0, 10, 20 µM	–	p-β- catenin↓, GSK3-β↓, p-GSK3-β↓, PI3K-a↓, AKT1↓, NF-Κb p-50↓	[9]
CRC	In Vitro	–	–	–	HT29 SW480 SW620 Lovo	0, 10, 50, 100 µM	–	MMP-2↓, MMP-3↓, MMP-9↓, MMP-16↓, miR-384↑, PTN↓	[19]
CRC	In Vivo	♂	BALB/c nude	39	HT29	100 mg/kg	Gavage	Inhibits in vivo metastasis of tumors	[19]
CRC	In Vitro	–	–	–	HCT116 SW480	0, 1.56, 3.125, 6.25, 12.5, 25, 50 µM	–	ROS↑, MDA↑, HIC1↑, GSH↓	[20]
CRC	In Vivo	♂	BALB/c nude	25	HCT116	0.60 mg/kg	Gavage	Ki67↓, GSH↓, MDA↑	[20]
CRC	In Vivo	♂	Fischer 344	40	–	0.25 mg/kg	Intraperitoneal injection	Prevotella↑, Butyricicoccaceae↑, Clostridia vadinBB60↑, Muribaculum↑, Clostridiaceae↓, Actinomycetota↓, Christensenellaceae↓, Eggerthellaceae↓, Anaerovoracaceae↓, Clostridia UCG-014↓	[21]
CRC	In Vitro	–	—	–	HCT116	0.01, 0.1, 1, 5, 10, 25 µM	–	P53↑, AKT↑, AMPK↓(> 10 µM), Nrf↑, ARE↑, HO-1↑	[8]
CRC	In Vivo	♂	BALB/c nude	28	HCT116	0.50 mg/kg	Intraperitoneal injection	P53↑, HO-1-	[8]
CRC	In Vitro	–	–	–	HT-29	0, 50, 100, 200, 400, 600, 800, 1000 µg/ml	–	P53↓, Bcl-2↓, Bax↑, AKT↓, mTOR↓, VEGF↓ P38 MAPK↑, PTEN↑, p53↑	[23]
CRC	In Vitro	–	–	–	RKO SW480	0, 5, 10, 20, 40, 80 mg/kg	–	cyclinB1↓, cyclinB1/cdc2↓, P21↑, p-cdc2↑, Bcl-2↓, Bax↑, E-cadherin↑ Cleaved Caspase-3↑, MMP9↓, vimentin↓,	[24]
CRC	In Vivo	♀	BALB/c nude	20	RKO SW480	0, 20 mg/kg	Tail vein injection	GPSM2↓, PCNA↓, p-FoxO1a↓, p-FoxO3a↓	[24]
CRC	In Vitro	–	–	–	HCT116	0, 3.125, 6.25, 12.5, 25, 50, 100 µg/ml	–	Reduces mitochondrial membrane potential	[25]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

Luteolin and hepatocellular carcinoma

Luteolin can mediate several classical pathways and inhibit HCC cell proliferation, migration or invasion. Yu et al. found that luteolin can promote the upregulation of HCC prognostic gene ESR1, induce G2/M arrest of HCC cells, inhibit cell migration and promote apoptosis by inhibiting AKT and MAPK-JNK signaling pathways [26]. Similarly, Im et al. found that luteolin induced the increase of cleaved Caspase-3, cleaved caspase-8, cleaved Caspase-9 and cleaved PARP expression in HCC cells by inhibiting AKT/OPN signaling pathway, while inhibiting the expression of XIAP, Mcl-1 and Bid, indicating that luteolin could activate caspase dependent apoptosis of HCC cells [27]. In addition, Ma et al. pointed out that luteolin up-regulates the AKT1/MDM2/p53 (p21, GADD45, DR5, etc.) signaling pathway inhibited by AKT1 and the key factors downstream of AKT/Fox (TRAIL, p15, p21, etc.) signaling pathway, thereby inhibiting the expression of CDK1, CDK2, CDK4, CDK6, CycE, CycA by inhibiting the expression of AKT1. Luteolin can also inhibit the expression of S phase protein, DNA synthesis, RNA synthesis and protein synthesis-related genes, resulting in cell cycle arrest and apoptosis. The study also found that luteolin could inhibit the expression of SRC and downstream components of SRC-STAT3 pathway, such as HGF, FGF, VEGF, HIFa, AKT1, CXCL10, IFNγ, SOCS, Bcl-xL, MCL1, c-MYC and CycD, and promote the expression of p21, GFAP and BIRC5, causing HCC cell cycle arrest and apoptosis [28]. In addition to inhibiting PI3K/AKT signaling pathway, Yang et al. found that luteolin can inhibit FLOT expression by up-regulating miR-6809-5p, and then inhibit Erk1/2, p38, JNK and NF-κB/p65 signaling pathways, causing cell cycle arrest and apoptosis, and finally significantly inhibiting the proliferation of HCC cells in vivo [29]. Moreover, Nazim et al. found that luteolin increased the sensitivity of HCC cells to TRAIL by up-regulating the expression of DR5, LC3-II, cleaved Caspase-3 and cleaved caspase-8 mediated by JNK in HCC cells, down-regulating the expression of p62, and finally promoting autophagy of HCC cells [30]. Leed et al. found that luteolin could induce endoplasmic reticulum stress in HCC cells with p53 deletion, increase cleaved PARP and decrease PCNA, up-regulate p21mRNA associated with cell cycle arrest and decrease the expression level of TAP6, which indicated that luteolin’s ability to inhibit HCC was related to p53 deletion. Interestingly, luteolin also induced up-regulation of LC3-II and down-regulation of P62 in p53-deleted HCC cells, inducing protective autophagy of HCC, while luteolin had no significant effect on autophagy of p53 wild-type HCC cells, indicating that luteolin could exert anticancer effects through p53-dependent and p53-independent pathways [31]. In addition, Xu et al. found that luteolin can inhibit the migration and proliferation of HCC by inhibiting YAP signaling pathway [32].

Luteolin, when used in combination with other drugs, can significantly enhance the inhibitory effect on HCC. Cai et al. found that the proportion of CD8⁺ T lymphocytes in peripheral blood, spleen and tumor tissues of subcutaneous xenografted HCC mice treated with luteolin increased, the immune activity of CB8⁺ T cells was significantly increased due to more granzyme B, INF-γ and TNF-a, and there were higher expression of cleave Caspase-3, Caspase-3, caspase-8, Caspase-9, Bax and Bcl-2 in HCC tissues, which proved that luteolin could enhance the infiltration of CD8⁺ T cell lymphocytes into HCC cells. It also enhances CD8⁺ T cell cytotoxicity [33]. Alshamranid et al. found that when polymer micelles (PMs) containing luteolin and doxorubicin were treated with HCC cells, luteolin and doxorubicin could play a synergistic role, and this mode of administration improved drug stability and delivery efficiency, and promoted apoptosis of HCC cells [34]. Luteolin can not only enhance the sensitivity of HCC to chemotherapy drugs, but also combine with oncolytic pox virus and show significant anti-HCC effect. Wang et al. found that oncolytic pox virus carrying IL-24 gene (VV-IL24) combined with luteolin inhibited the activity of HCC cells more than either drug alone, indicating that the combination of the two drugs had synergistic effect. The expression of cleaved PARP, cleaved Caspase-3, cleaved caspase-8 was increased and the expression of proCaspase-3, procaspase-8, XIAP was decreased in HCC cells treated with luteolin, which indicated that luteolin could activate caspase dependent apoptosis system and inhibit the proliferation of HCC cells. In vivo studies also found that the combination group significantly reduced the expression of CD31 and Ki67 compared with the single drug group, and promoted the increase of IL-24 and Caspase-3 expression, and finally inhibited the proliferation and angiogenesis of HCC [35].

Many researchers have significantly improved the availability and effect of luteolin by changing different modes of administration. Cao et al. found that PLGA/liposomes loaded with luteolin modified by PD-L1 (L-PD-SP/Ls) had good targeting to HCC. This preparation can promote the release of lactate dehydrogenase by HCC cells by reducing the expression of Bcl-2, indicating that luteolin can mediate mitochondrial apoptosis to inhibit the growth of HCC cells, and improve the bioavailability of luteolin through PD-L1 targeting [36]. Elnaggar et al. found that loading lutein-phospholipid Complexes Into chylomicrons (LPC-CM) had higher anticancer efficacy against HCC. The complex enhances the dissolution and absorption of luteolin through endocytosis, and finally induces apoptosis and autophagy in HCC cells. In vivo experiments found that LPC-CM in a sustained release state achieved targeted therapy for liver, compared with free luteolin, the growth inhibition rate of HCC cells increased by 2.6 times, and this growth inhibition of HCC was achieved by inducing apoptosis of HCC cells [37]. Elsayed et al. found that treatment with nanoemulsion nanoparticles loaded with luteolin (LUT-ENPs) can promote long-term release of luteolin in vivo. The results of the stability study showed that the amount of luteolin exuded from LUT-ENPs, the vesicle size and the percentage of luteolin released increased over time. Compared with luteolin suspension alone, LUT-ENPs treatment significantly improved liver biomarkers, decreased oncogene GPC3 expression, decreased NO and MDA content in HCC tissue, and increased glutathione and SOD levels in liver tissue, demonstrating that LUT-ENPs treatment has stronger inhibitory effect on HCC cells and higher safety [38]. We summarized the results of the effects of luteolin on different HCC cell lines through different pathways (Table 2).

Table 2.

The results of Luteolin on different HCC cell lines via different pathways

Type of cancer	In Vitro/In Vivo	Sex	Module	Sample	Cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
HCC	In Vitro	–	–	–	SK-Hep-1	0, 20, 40, 80 µM	–	p-AKT↓, OPN↓, XIAP↓, Mcl-1↓, Bid↓, cleaved Caspase-3↑, cleaved Caspase-8↑, cleaved Caspase-9↑, cleaved PARP↑,	[27]
HCC	In Vitro	–	–	–	Huh-7	0, 3.125, 6.25, 12.5, , 25, 50, 100 µM	–	AKT1↓, SRC↓, p21↑, GADD45↑, DR5 ↑, TRAIL↑, p15↑, HGF↓, FGF↓, VEGF↓, HIFa↓, AKT1↓, CXCL10↓, IFNγ↓, SOCS↓, Bcl-xL↓, MCL1↓, c-MYC↓, CycD↓, p21↑, GFAP↑, BIRC5↑, CDK1↓, CDK2↓, CDK4↓, CDK6↓, CycE↓, CycA↓	[28]
HCC	In Vivo	♀	BALB/c nude	22	Huh-7	50 mg/kg	Not specified	miR-6809-5p↑, Ki-67↓, p-Erk1/2↓, p-p38↓, p-JNK↓, p-NF-κB/p65↓,	[29]
HCC	In Vitro	–	–	–	Huh7 Hep3B	0, 5, 10, 20 µM	–	p-JNK↑, DR5↑, LC3-II↑, p62↓, cleaved Caspase-3↑, cleaved caspase-8↑	[30]
HCC	In Vitro	–	–	–	Hep3B HepG2	0, 1, 2.5, 5, 10 µM	–	p21↑, cleaved PARP↑, TAP63↓, PCNA↓, LC3-II↑, P62↓	[31]
HCC	In Vitro	–	–	–	Huh-7 HepG2 PLC/PRF/5 293T	0, 20, 40, 60, 80 µM	–	p-Yap/Yap↑	[32]
HCC	In Vivo	♀	BALB/c	16	H22	50, 100, 200 mg/kg	Gavage	CD8T(CD3e, CD8a, CCL5, CCL21)↑, Granzyme B↑, INF-γ↑, TNF-a↑, cleaved Caspase-3↑, Caspase-3↑, Bax↑, caspase-8↑, Bcl-2↑, Caspase-9↑	[33]
HCC	In Vitro	–	–	–	HepG2	0, 0.78, 1.56, 3.125, 6.25, 12.5, 25, 50, 100 µg	–	Induce apoptosis	[34]
HCC	In Vitro	–	–	–	MHCC97-H Hep3B	0, 0.625, 1.25, 2.5, 5 µg/ml	–	cleaved PARP↑, cleaved Caspase-3↑, cleaved caspase-8↑, proCaspase-3↓, procaspase-8↓, XIAP↓	[35]
HCC	In Vivo	♀	BALB/c nude	32	MHCC97-H	50 mg/kg	Intraperitoneal injection	IL-24↑, CD31↓, Ki67↓, Caspase-3↑	[35]
HCC	In Vitro	–	–	–	HepG2	0, 10, 20, 100 µg/ml	–	Bcl-2↓, LDH↑	[36]
HCC	In Vitro	–	–	–	HepG2	24 µg/ml	–	Induce apoptosis and autophagy	[37]
HCC	In Vivo	♂	CD-1	80	EAC	10 mg/kg	Intraperitoneal injection	Inhibit tµMor growth	[37]
HCC	In Vivo	♂	Wistar	90	–	10 mg/kg	Gavage	GPC3↓, NO↓, MDA↓, GSH↑, SOD↑	[38]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

Luteolin and gastric cancer

Related studies provide different perspectives on the mechanism of luteolin in GC apoptosis. Yajie et al. found that Bax, Caspase-3 and Cytochrome c were significantly increased and Bcl-2 was significantly decreased in GC cells treated with luteolin in combination with LY294002, which was more significant than that treated with luteolin alone, suggesting that the combination group could induce apoptosis synergistically, and the ability of luteolin to inhibit GC cell proliferation might be related to PI3K/AKT signaling pathway [39]. Lu et al. found that luteolin inhibited ERK1/2 and PI3K/AKT/mTOR signaling pathway by mediating DUSP1, 2, 4, 5 and CXCL16 after acting on GC cells, increased Cytochrome c in a dose-dependent manner, activated the expression of cleaved Caspase-9 and cleaved Caspase-3, induced the increase of Bax/Bcl-2 ratio, and promoted GC cell apoptosis, indicating that luteolin could induce GC cell apoptosis through endogenous pathway [40].

Luteolin can inhibit the proliferation, migration, invasion and drug resistance of GC cells by inhibiting PI3K/AKT/mTOR, NF-κB, Notch, MAPK and other classical pathways. Pu et al. showed that luteolin could inhibit the expression of Cyclin D1, Cyclin E, Bcl2, and promote the expression of p21, Bax, thereby inducing apoptosis and cycle arrest, and finally inhibiting the colony formation of GC cells. In addition, luteolin can also inhibit the proliferation of GC cells by regulating the expression of microRNA, namely, promoting the expression of tumor suppressor miR-139, miR-34a, miR-422a and miR-107, inhibiting the expression of tumor promoter miR-21, miR-155, miR-224 and miR-340, and promoting the expression of E-cadherin by inhibiting tumor migration-related proteins MMP2, MMP9, N-cadherin and vimentin. To inhibit the migration and invasion of GC cells. The experiment also confirmed that luteolin can inhibit multiple signaling pathways related to GC cell development, such as Notch1, p-PI3K, p-AKT, p-mTOR, p-ERK, p-STAT3, and promote p-P38 signaling pathway, but whether these pathways inhibit GC proliferation, migration and invasion by affecting the above molecules remains to be further studied [41]. Zhou et al. found that luteolin targets HK1 by inducing tumor suppressor gene miR-34a, thereby inhibiting the expression of HK1, p-MAPK and p-ERK, promoting the expression of P53 and P21, inducing G1 phase arrest of GC cells, and then inhibiting the proliferation and colony formation of GC cells [42]. Radzieewska et al. found that luteolin treatment of GC cells increased the expression of NF-KB mRNA and induced pro-inflammatory factors that promote tumor growth and immune escape: IL-8, IL-10 mRNA level significant expression, inhibit the activation of anti-apoptotic protein MUC1 mucin extracellular domain expression, promote GC growth ADAM-17 expression has an inhibitory effect, which proves that luteolin may activate IL-8, IL-10, NF-κB expression inhibit MUC1 and ADAM-17 expression, and finally inhibit GC growth, but this study also shows that the high expression of IL-8, IL-10, NF-κB in some literatures means the hyperfunction of GC cells, which may be caused by different cell line selection, The study indicates that the increasing effect of luteolin on the pro-inflammatory factor IL-8 appears to be reversible with high doses of luteolin, a finding that warrants further investigation [43]. Zang et al. found that luteolin can reduce the level of p-AKT in GC cells, down-regulate the interaction between NICD and β-catenin, and then inhibit the proliferation ability of GC cells, and mediate the inhibition of Notch1 signaling pathway to reverse the EMT of GC cells to a certain extent, resulting in GC cytoskeleton contraction, cell size reduction, and inhibition of GC cell migration and invasion ability, indicating that luteolin can inhibit the proliferation, migration and invasion of GC cells by inhibiting Notch, β-catenin and AKT signaling pathways [44]. Zang et al. found that luteolin inhibited VEGF secretion by down-regulating Notch1 signaling pathway, dose-dependently inhibited the formation of HUVECs in GC cells, and then inhibited the proliferation and migration of GC cells caused by the interaction between GC cells and HUVECs [45].

In combination chemotherapy, luteolin combined with other chemotherapy drugs can reduce GC resistance to chemotherapy drugs and improve the efficacy of chemotherapy drugs. Ma et al. found that luteolin combined with oxaliplatin significantly reduced the expression of Cyclin B1, CDK1, TRAP1 and Cdc25C closely related to G/M cell arrest or apoptosis, inhibited ERK1/2 phosphorylation, promoted ROS accumulation in GC cells, destroyed mitochondrial function, induced Bcl-2/Bax protein ratio reduction, finally led to GC cell apoptosis, induced MMP expression reduction, and inhibited GC cell migration and invasion [46]. Similarly, Ren et al. also showed that luteolin combined with oxaliplatin treatment of GC cells could up-regulate the expression of Cyclin D1, up-regulate the expression of apoptosis-related proteins Bax, cleaved Caspase-3 and Cytochromeme c, and down-regulate the expression of Bcl-2 and Caspase-3, which indicated that luteolin combined with oxaliplatin could induce GC cells to stay in G0/G1 phase and induce GC cell apoptosis, and jointly inhibit the occurrence and development of GC [47]. In addition, Song et al. found that luteolin treatment of GC cells could enhance the binding of SHP-1 and STAT3, destroy the binding of HSP90 and STAT3, significantly inhibit STAT3 phosphorylation in cisplatin-resistant GC cells, and dose-dependently inhibit the expression of survival-promoting genes Mcl-1, Bcl-xL and Survivin downstream of STAT3, and finally inhibit chemotherapy resistance caused by excessive activation of STAT3 [48].

In order to improve the bioavailability of luteolin, there are studies based on existing drug delivery methods applied to luteolin therapy. Ding et al. incorporated luteolin into Her-2 antibody-modified poly nanoparticles (HER-2-PLGA-NPs). GC cells recognized HER-2-PLGA-NPs with higher phagocytosis efficiency, which provided the possibility of targeted drug delivery. Compared with free luteolin alone, Lutein-loaded nanoparticles mediated Her-2 targeted delivery significantly increased the inhibition efficiency of GC cells. The study also found that luteolin may inhibit GC cells by up-regulating FOXO1 expression [49].

As mentioned above, the structure of luteolin determines the function of luteolin. Induce the decrease of antioxidant enzyme (SOD) activity and increase of ROS in GC cells, inhibit the activity of METC Complexes I, III and V at the same time, destroy mitochondrial outer membrane by down -regulating Bcl-2 and up-regulating Bax protein, and then induce apoptosis, and reduce cell membrane permeability by down-regulating the activity of Na/K-ATPase and Ca/Mg-ATPase binding enzyme in cell membrane, thus mediating GC cell death [50]. We summarize the results of luteolin action on different GC cell lines via different pathways (Table 3).

Table 3.

The results of Luteolin on different GC cell lines via different pathways

Type of cancer	In Vitro/In Vivo	Sex	Module	Sample	Cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
GC	In Vitro	–	–	–	MKN45	0, 10, 30, 50 µmol/L	–	Bax↑, Caspase-3↑, Cytochrome c↑, Bcl-2↓, p-AKT↓	[39]
GC	In Vitro	–	–	–	BGC-823	0, 20, 40, 60 µM	–	Cytochrome c↑, cleaved Caspase-9↑, cleaved Caspase-3↑, Bax/Bcl-2↑, p-ERK1/2, PI3K↓, AKT↓, mTOR↓	[40]
GC	In Vitro	–	–	–	MKN45 BGC823	0, 5, 10, 20, 30, 40, 60, 80, 100 µM	–	Cyclin D1↓, Cyclin E↓, Bcl-2 ↓, p21↑, Bax↑, Notch1↓, p-PI3K↓, p-AKT↓, p-mTOR↓, p-ERK↓, p-STAT3↓, miR-139↑, miR-34a↑, miR-422a↑, miR-107↑, miR-21↓, miR-155↓, miR-224↓, miR-340↓, E- cadherin↑, MMP2↓, F- MMP9↓, N-cadherin↓, Vimentin↓	[41]
GC	In Vivo	–	BALB/c nude	16	MKN-45 BGC823	20 mg/kg	Intraperitoneal injection	Ki-67↓	[41]
GC	In Vitro	–	–	–	AGS BGC823 SGC7901	0, 5, 10, 20, 50, 100 µM	–	HK1↓, P53/P21↑, p-MAPK/p-ERK↓, miR-34a↑	[42]
GC	In Vivo	–	BALB/c nude	40	BGC823	10 mg/kg	Intraperitoneal injection	miR-34a↑, P53/P21↑, p-MAPK/p-ERK↓	[42]
GC	In Vitro	–	–	–	CRL-1739	0, 20, 40, 60, 100 µM	–	NF-κB↑, IL-8↑, IL-10↑, MUC1↓, ADAM-17↓	[43]
GC	In Vitro	–	–	–	Hs-746T MKN28 NCI-N87	0, 10, 20, 30, 50 µM	–	p-AKT↓, Notch1↓, NICD/β-catenin↓	[44]
GC	In Vivo	♂	BALB/c nude	8	MKN28	10 mg/kg	Intraperitoneal injection	β-catenin↓, Ki67↓, Notch1↓	[44]
GC	In Vitro	–	–	–	Hs-746T MGC-803	0, 10, 30 µM	–	Notch1↓, VEGF↓, HUVECs↓, VMs↓	[45]
GC	In Vitro	–	–	–	MFC	0, 10, 20, 30, 40, 50, 60, 70, 80 µM	–	Cyclin B1↓, CDK1↓, TRAP1↓, Cdc25C↓, p-ERK1/2↓, MMP↓, Bcl-2/Bax↓, ROS↑	[46]
GC	In Vitro	–	–	–	SGC-7901	0, 10, 20, 30, 40 50, 60 µM	–	Cyclin D1↑, Bax↑, Bcl-2↓, Cleaved Caspase-3↑, Caspase-3↓, Cytochrome c↑	[47]
GC	In Vitro	–	–	–	SGC7901/DDP SGC7901 HGC-27 BGC803 BGC823 MGC803	0, 2.5, 5, 10, 20 µM	–	Mcl-1↓, Bcl-xL↓, Survivin↓, STAT3↓, p-STAT3↓, SHP-1/STAT3 compound↑, HSP90/STAT3 compound↓	[48]
GC	In Vivo	♂	BALB/c nude	60	SGC7901/DDP SGC7901 HGC-27	20 mg/kg	Intraperitoneal injection	Mcl-1↓, Bcl-xL↓, Survivin↓, STAT3↓, p-STAT3↓, SHP-1/STAT3 compound↑, HSP90/STAT3 compound↓	[48]
GC	In Vitro	–	–	–	SGC-7901 BGC-823	0, 1.25, 2.5, 5, 10, 12.5, 25, 50, 100 µg/ml	–	FOXO1↑	[49]
GC	In Vitro	–	–	–	HGC-27 MKN-45 MFC	0, 10, 20, 30, 40, 50, 60, 70, 80 µM	–	SOD↓, ROS↑, Na/K-ATPase↓, Ca/Mg-ATPase↓, Bcl-2↓, Bax↑, METC Complexes I, III, V↓	[50]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

Luteolin and esophageal cancer

Luteolin can induce cell cycle arrest and apoptosis of EC cells, and then inhibit the proliferation of EC cells. Chen et al. found that luteolin could arrest EC cells in G2/M phase by up-regulating cell cycle inhibitor proteins p21 and p53. In addition, studies have also found that luteolin dose-dependently activates the expression of cPARP, CYT-C, BimL and BimS, and induces apoptosis by activating Caspase-3, indicating that luteolin can promote EC cell apoptosis by reducing mitochondrial membrane potential, thereby inhibiting EC cell proliferation [51].

Luteolin can regulate apoptosis of EC cells through various pathways, thereby reducing drug resistance or increasing drug sensitivity of EC cells. Liu et al. found that luteolin can inhibit EC cell migration and invasion in a dose-dependent manner, and inhibit cell proliferation by promoting apoptosis. Specifically, luteolin inhibits VRK1-mediated c-JUN phosphorylation, thereby inhibiting the transcription process of c-MYC, and finally improves the sensitivity of EC cells to cisplatin, which means that VRK1/c-JUN/c-MYC signaling pathway may be a potential pathway for regulating the sensitivity of EC cells to chemotherapeutic drugs [52]. Zhao et al. found that luteolin can inhibit the drug resistance of paclitaxel-resistant EC cells by inhibiting the expression of PI3K/AKT signaling pathway and UBR5 in a dose-dependent manner. Luteolin also inhibited the proliferation of EC cells by inhibiting the expression of p-AKT and UBR5 in vivo, which was consistent with the results in vitro. In addition, luteolin can also up-regulate the epithelial marker protein β-catenin and the core protein ZO-1 of the cell-cell junction complex in vivo, indicating that the inhibitory effect of luteolin on EC cell drug resistance may be realized by inhibiting the stemness characteristics in EC cells [53]. Yang et al. found that luteolin significantly increased the total apoptosis rate of paclitaxel-resistant EC cells in a dose-dependent manner by down-regulating the expression of EMT-related proteins Snail, N-cadherin, MMP-2 protein and stem cell markers SOX-2, CD44 and CD133, and induced cell cycle arrest in G/M phase, significantly inhibiting cell migration, invasion ability and drug resistance. At the same time, luteolin has strong binding ability with the active sites of FAK, SRC and AKT, and can inhibit the expression of FAK, SRC and ErbB2 to varying degrees, and down-regulate the expression of p-FAK/FAK, p-SRC/SRC and p-AKT3/AKT3. This study suggests that the ability of luteolin to inhibit EC cell drug resistance may be related to FAK/SRC/PI3K/AKT signaling pathway [54]. Luteolin significantly increased the expression of ROS, p-ASK1, p-MKK4, p-JNK and JNK when used in combination with low dose paclitaxel, indicating that the combination of luteolin and paclitaxel activated ROS/JNK signaling pathway. In addition, the expressions of Bax/Bcl-2, Noxa, cleaved Caspase-9 and cleaved Caspase-3 were increased after co-treatment, indicating that the apoptosis rate of EC cells was increased, the proliferation and colony formation of EC cells were inhibited, and SIRT1 and N-cadherin were significantly decreased, indicating that EC cell metastasis was also inhibited. Combination therapy can not only inhibit tumor growth rate in vivo, reduce the expression of SIRT1 and N-cadherin, but also enhance the expression of vimentin, Claudin-1 and ZO-1, and further promote the expression of Bax, Noxa, Bid and Puma by significantly increasing the expression of p-ASK1, p-MKK4, p-JNK and JNK, and down-regulate the expression of anti-apoptotic protein Mcl-1, and finally activate the expression of Caspase-9 and Caspase-3. It was further confirmed that luteolin combined with low dose paclitaxel could inhibit EC cell migration, EMT and induce apoptosis through ROS/JNK signaling pathway [55]. We summarize the results of luteolin on different EC cell lines via different pathways (Table 4).

Table 4.

The results of Luteolin on different EC cell lines via different pathways

Type of cancer	In Vitro/In Vivo	Sex	Module	Sample	Cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
EC	In Vitro	–	–	–	EC1 KYSE450	0, 20, 40, 60, 80, 100 µM	–	p21↑, p53↑, Caspase-3↑, Reduces mitochondrial membrane potential	[51]
EC	In Vivo	♀	BALB/C-nu	16	EC1-E-GFP	50 mg/kg	injection administration	Inhibit tumor growth	[51]
EC	In Vitro	–	–	–	ECA109 KYSE	0, 10, 20, 50, 100 µM/ul	–	pc-JUN↓, c-MYC↓, VRK1↓	[52]
EC	In Vivo	–	BALB/C-nu	40	Ec9706	5 mg/kg	Intraperitoneal injection	Inhibit tumor growth Enhance cisplatin resistance	[52]
EC	In Vitro	–	–	–	TE-1/PTX EC109/PTX	0, 10, 20, 40 µM	–	PI3K↓, AKT↓, UBR5↓, SOX2↓	[53]
EC	In Vivo	♀	BALB/c nude	20	EC109 EC109/PTX	50 mg/kg	Intraperitoneal injection	p-AKT↓, UBR5↓, β-catenin↑, ZO-1↑	[53]
EC	In Vitro	–	–	–	EC1 EC1/PTX	0, 20, 40, 60, 80, 100, 120 µM	–	Snail↓, N-Cadherin↓, MMP-2↓, SOX-2↓, CD44↓, CD133↓, FAK↓, SRC↓, ErbB2↓, p-FAK/FAK↓, p-SRC/SRC↓, p-AKT3/AKT3↓	[54]
EC	In Vivo	♀	BALB/c nude	25	EC1/PTX	20, 40 mg/kg	Intraperitoneal injection	p-FAK/FAK↓, p-SRC/SRC↓, BCRP↓, p-AKT3/AKT3↓, ErbB2↓, P-gp↓, MRP1↓	[54]
EC	In Vitro	–	–	–	TE-1 EC109	0, 10, 20, 30, 40, 60, 80, 120, 160 µM	–	Bax/Bcl-2↑, Noxa↑, clCaspase-9↑, cleaved Caspase-3↑, ROS↑, p-ASK1↑, p-MKK4↑, p-JNK↑, JNK↑, SIRT1↓, N-Cadherin↓	[55]
EC	In Vivo	♀	BALB/c nude	24	EC109	50 mg/kg	Intraperitoneal injection	SIRT1↓, N-Cadherin↓, vimentin↑, Claudin-1↑, ZO-1↑, Bax↑, Noxa↑, Bid↑, Puma↑, Caspase-9↑, Caspase-3↑, p-ASK1↑, p-MKK4↑, p-JNK↑, JNK↑, Mcl-1↓	[55]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

Luteolin and pancreatic cancer

Luteolin can affect PC cells through various pathways and exhibit significant anticancer activity. Luteolin promotes PC cell apoptosis directly or indirectly, and then inhibits PC cell growth. Li et al. found that luteolin can specifically bind to Bcl-2, induce BAX release from Bcl-2 through mitochondrial depolarization pathway, and dose-dependently increase the activation of Caspase-3 and PARP, trigger PC cell apoptosis, and finally achieve the effect of inhibiting PC cell growth. In vivo experiments, it was also observed that luteolin could inhibit tumor tissues without causing damage to normal tissues, which proved that luteolin had good safety [56]. Moeng et al. found that luteolin can down-regulate the expression of oncogene miR-301-3p in PC cells and increase the level of its direct target caspase-8. By promoting PC cell apoptosis in this way, luteolin enhances PC cell sensitivity to TRAIL, a tumor necrosis factor-related apoptosis-inducing ligand, while TRAIL inhibits cell growth by inducing PC cell cycle arrest in G0/G1 phase [57].

STAT3 signaling pathway is abnormally activated in many tumors and induces tumor proliferation, migration and invasion by affecting inflammatory factors, immune system and energy metabolism pathways [58]. Luteolin can inhibit PC cell proliferation, migration and invasion by affecting STAT3 signaling pathway related molecules. Huang et al. found that luteolin could significantly inhibit STAT3 expression, mediate STAT3 signaling pathway to inhibit IL-6-induced secretion of MMP 2, MMP 7, MMP 9 and EMT, and dose-dependently increase the expression of metastasis-related protein CDH1 and decrease the expression of CDH2, vimentin, ZEB1 and Snail, indicating that luteolin inhibited PC cell migration and invasion by inhibiting STAT3 pathway [59]. In addition, Kato et al. found that luteolin delayed tumor lesions in pancreatic ductal PanINs and PDACs, inhibited Ki-67 labeling index in PDACs, and dose-dependently inhibited PDAC cells and induced G1 arrest in PDAC cells. The expression of p-STAT3 and DPYD was also significantly decreased. A positive correlation between p-STAT3 and DPYD was also found. STAT3 expression plays an important role in acinar duct metaplasia and PanIN to PDAC multistep carcinogenesis, suggesting that luteolin can inhibit PDAC cell proliferation and pancreatic cell carcinogenesis by inhibiting p-STAT3 and DPYD [12].

Luteolin can also reduce drug resistance of PC cells when used in combination with chemotherapy drugs. Kato et al. found that luteolin combined with 5-FU could inhibit the expression of DPYD in PC cells with high expression of DPYD, thus inhibiting tumor proliferation, migration, invasion and 5-FU resistance mediated by DPYD. This therapeutic effect was not significant when luteolin alone was used to treat PC, demonstrating the synergistic effect of 5-FU and luteolin [60].

Due to the poor water solubility and low bioavailability of luteolin, Karole et al. studied to improve the bioavailability of luteolin in order to enhance the therapeutic effect by non-invasively overcoming the intestinal epithelial barrier through lutein-loaded nanospheres (LUT-NPs), improving the absorption and utilization of intestinal lymphatic system mediated by micropleated cells, and then specifically targeting PC cells, dose-dependently up-regulating the expression of Caspase-3 and down-regulating the expression of VEGF-A, FAK, TNF-a and Ki-67. LUT-NPs exhibit stronger antiangiogenic ability than luteolin suspension alone, inhibiting PC cell growth in vivo [61]. We summarize the results of luteolin on different PC cell lines via different pathways (Table 5).

Table 5.

The results of Luteolin on different PC cell lines via different pathways

Type of cancer	In Vitro/In Vivo	sex	Module	Sample	cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
PC	In Vitro	–	–	–	SW1990	100 nm, 0, 1, 10, 100, 200 µM	–	Bcl-2↓, Caspase-3↑, PARP↑, BAX↑	[56]
PC	In Vivo	♀	SCID	24	–	0, 75, 150 mg/kg	Gavage	Inhibit tumor growth	[56]
PC	In Vitro	–	–	–	PANC-1	0, 25, 50 µM	–	miR-301-3p↓, caspase-8↑	[58]
PC	In Vitro	–	–	–	PANC-1 SW1990	0, 20, 40, 80, 160, 320 µM	–	STAT-3↓, MMP2↓, MMP7↓, MMP9↓, CDH1↑, CDH2↓, Vimentin↓, ZEB1↓, Snail↓	[59]
PC	In Vitro	–	–	–	MIAPaCa2 KP4 PANC1	0, 10, 25, 50, 75, 100 µM	–	p-STAT3↓, DPYD↓	[12]
PC	In Vivo	♀	Syrian golden hamsters	53	–	100 ppm in diet	Medication administration through diet	p-STAT3↓, DPYD↓, Ki-67↓	[12]
PC	In Vivo	–	KSN/Slc	59	AsPC1-DPYD AsPC1-LacZ	100 ppm in diet	Medication administration through diet	DPYD↓	[60]
PC	In Vivo	♂	Wistar	12	PANC-1	–	Oral administration	Caspase-3↑, VEGF-A↓, FAK↓, TNF-a↓, Ki-67↓,	[61]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

The toxicological characteristics of luteolin

Luteolin has exhibited beneficial pharmacological effects in the treatment of digestive tract malignancies, with most studies indicating minimal pharmacological toxicity. This finding underscores the clinical safety of luteolin and supports the expansion of its application. However, it is important to note that luteolin is not devoid of harm at any dosage. Certain safety studies have identified its toxic properties under specific conditions.

The research conducted by Li, X. et al. demonstrated that luteolin significantly increases the risk of DNA damage and chromosomal aberrations in human lymphoblastoid TK6 cells by mediating the upregulation of cytochrome P450 1A1 (CYP1A1) and cytochrome P450 1A2 (CYP1A2) expression [62]. This ultimately triggers the apoptosis program. Animal experiments by Abdulmannan H. Fateh et al. revealed that administering a decoction of verbena extract to female rats resulted in noticeable deformities in their newborns [63]. Further mechanistic analysis indicates that this malformation phenotype may be associated with the abnormal activation of luteolin in regulating the differentiation of mesenchymal cells into the osteogenic lineage and the formation of the cartilage core. Moreover, the severity of the malformation exhibits a clear dose-dependent relationship with the exposure dose of luteolin.

Mitsuyoshi MATSUO et al. found that luteolin can mediate an increase in ROS levels in normal human cells, thereby exerting cytotoxic effects [64]. Additionally, the study indicated that luteolin possesses dual functions as both an antioxidant and a pro-oxidant. The predominance of its functional advantages largely depends on factors such as drug concentration, cell lines, and the culture environment. In conclusion, luteolin, when administered within a specific dose range, may induce pharmacological toxicity in cells, tissues, or organs. This underscores the importance of conducting systematic research on the drug toxicity of luteolin, as such studies can provide a robust experimental foundation for optimizing its precise clinical application (Table 6).

Table 6.

Research results on the toxicity of Luteolin drugs

In Vitro/In Vivo	sex	Module	Sample	cell line	Luteolin in vitro and in vivo doses	Route of administration	Result	References
In Vitro	–	–	–	TK6	0, 0.625, 1.25, 2.5, 5, 10 µM	–	CYP1A1↑ CYP1A2↑	[62]
In Vivo	♀	Sprague-Dawley	50	–	–	Oral administration	Induce mesenchymal cells to differentiate into osteogenic lineages	[63]
In Vitro	–	–	–	TIG−1 HUVE	0, 50, 100, 150, 200 µM	–	ROS↑	[64]

“↑”indicates up-regulation, “↓”indicates down-regulation, and - indicates cell administration or an unknown route of administration or gender

Conclusion

Malignant tumors of digestive tract threaten the life and health of modern people with high mortality, complicated complications and poor prognosis. Although there are many kinds of chemotherapy, immunotherapy and targeted therapy drugs for digestive tract malignant tumors, the drug resistance problem of digestive tract malignant tumors always affects the treatment effect, and it is urgent to find new treatment schemes. Under this background, the modernization research of traditional Chinese medicine provides a new scheme for the treatment of digestive tract malignant tumor. The extraction of effective components of traditional Chinese medicine, combined with modern pharmacology and pathology research, plays an important role in the treatment of modern digestive tract malignant tumor.

In conclusion, a review of the existing research indicates that luteolin exerts its anti-CRC effects primarily through several mechanisms: it activates the MAPK-ERK/JNK and PI3K/AKT signaling pathways to promote tumor cell apoptosis; it mediates lipid peroxidation reactions that induce ferroptosis in tumor cells; and it regulates the composition and function of the intestinal microbiota. Regarding its effects on anti-HCC, luteolin induces tumor cell cycle arrest by inhibiting the STAT3 and PI3K-AKT pathways, while also exerting anti-cancer effects through immune system reprogramming. Mediating the inhibition of the Notch/β-catenin-AKT pathway suppresses the proliferation, migration, and angiogenesis of GC. This intervention also impairs the formation of the mitochondrial electron transport chain (METC) complex I/III/Vx, promotes apoptosis in GC cells, and enhances cisplatin sensitivity through mechanisms such as increasing the binding of SHP-1 to STAT3. Luteolin induces apoptosis in EC cells by activating the ROS/JNK pathway while inhibiting the FAK/SRC/PI3K-AKT pathway, thereby increasing their sensitivity to paclitaxel. Additionally, luteolin mediates the p53/p21 pathway to induce cell cycle arrest in EC cells. By inhibiting the STAT3/DPYD pathway, luteolin suppresses EMT-related molecules, which in turn inhibits the metastasis and invasion of PC. Concurrently, downregulating DPYD enhances the chemosensitivity of PC to 5-FU (Table 7) (Fig. 2).

Table 7.

The main mechanisms of Luteolin in treating malignant tumors of the digestive tract

Type of cancer	Main mechanism of action
CRC	MAPK-ERK/JNK and PI3K/AKT-mediated apoptosis	Mediating lipid peroxidation to promote ferroptosis	Alterations in the gut microbiota/Changes in the intestinal microbiota
HCC	Blockade of the STAT3 and PI3K-AKT pathways induces cell cycle arrest	Immune system reprogramming
GC	Notch/β-catenin-AKT pathway	Inhibiting the formation of METC complexes I/III/V to promote GC cell apoptosis	Enhance the binding of SHP-1 to STAT3 and other pathways to inhibit cisplatin resistance in GC
EC	Overactivating the ROS/JNK pathway and inhibiting the FAK/SRC/PI3K-AKT pathway to induce EC cell apoptosis	Mediating the p53/p21 pathway to induce EC cell cycle arrest
PC	Mediating the STAT3/DPYD pathway to inhibit EMT-related molecules	Downregulating DPYD to enhance chemosensitivity to 5-FU

Fig. 2.

Main Mechanisms of Luteolin in Gastrointestinal Malignant Tumors

Discussion

Flavonoids such as luteolin, quercetin, daidzein and catechin are widely found in traditional Chinese herbal medicine, and luteolin stands out among many flavonoids for its significant anti-tumor and antioxidant effects. Although luteolin has been extensively studied for its anti-gastrointestinal cancer activity, there are still some limitations in the study of luteolin. Firstly, the poor water solubility and low bioavailability of luteolin limit the experimental results. In order to explore the best effect of luteolin on malignant tumors, the best route of administration or different routes of administration should be selected for experiments, studies have utilized neutrophil-mimetic nanoparticles and membrane-coated drug carriers for drug delivery, which provides to provide insights into achieving precise targeted therapy of luteolin against tumors and reducing systemic toxicity [65]. Secondly, most of the existing studies focus on the mechanism of luteolin inducing tumor cell apoptosis, and the exploration of autophagy, ferroptosis, immune system, energy metabolism and digestive tract flora is obviously insufficient, so the anti-cancer mechanism of luteolin needs to be analyzed from multiple dimensions. Thirdly, although there have been studies comparing luteolin with other flavonoids in terms of efficacy, such studies are relatively few, and most of them only focus on the cytotoxicity of drugs to tumor cells, but lack of exploration of the differences in related mechanisms. At the same time, it is necessary to explore the synergy between flavonoids and whether the combination of flavonoids will further enhance the synergy with chemotherapy drugs, immune drugs and targeted drugs. Fourth, compared with in vitro administration that directly acts on tumor cell targets, in vivo administration of luteolin is characterized by bioavailability largely determined by the route of administration due to hepatic and renal metabolism and other factors. Therefore, the discrepancy between the in vivo administration concentration and actual bioavailability may lead to differences from the results of in vitro administration. Finally, although luteolin has demonstrated good anticancer effects in different cell lines and animal tumor models of digestive tract malignancies, there is still a lack of large-sample, multicenter evidence-based medical validation of long-term clinical safety and efficacy.

In conclusion, future research on luteolin should focus on improving its bioavailability through multiple routes of administration, carriers, and modifications; regulating the stability of drug efficacy, prolonging the drug circulation time, and enhancing targeting effects; reducing potential drug toxicity; deepening the research on its mechanisms to clarify the core targets and pathways underlying its therapeutic effects; conducting in-depth pharmacokinetic and toxicological studies; verifying its therapeutic effects through combination therapy strategies and long-term clinical trials; reducing drug extraction costs; and expanding the research and development scale. These efforts aim to promote the formulation development of luteolin, facilitate its translation from laboratory research to clinical application, and provide safer and more effective therapeutic options for patients with digestive system malignancies.

To sum up, future research on luteolin should focus on enhancing bioavailability, deepening mechanism research, exploring combination therapy strategies and carrying out long-term clinical validation, so as to promote the formulation development of luteolin, promote the transformation of luteolin from laboratory research to clinical application, and provide safer and more effective treatment options for patients with malignant tumors of digestive tract.

Author contributions

Zeyu Tu: Writing—Original Draft, Writing—review and editing, Conceptualization, Software, Methodology, Investigation, Data Curation, Visualization. Peipei Yang: Writing—review and editing, Software, Investigation, Visualization, Validation. Hengchao Guan: Writing—review and editing, Investigation, Visualization. Xinyan Shu: Writing—review and editing, Validation, Data Curation. Yinghong Li: Writing—review and editing, Investigation, Data Curation. Tianlu Chu: Writing—review and editing, Data Curation, Validation. Yuhao Teng: Writing—review and editing, Data Curation. Yuanyuan Xu: Writing—review and editing, Data Curation. Peng Shu: Writing—review and editing, Conceptualization, Supervision, Resources, Funding acquisition, Project administration.

Funding

This study was supported by the National Natural Science Foundation of China (No. 82374539), the Major Project of Jiangsu Administration of Traditional Chinese Medicine (No. ZD202214), and the Jiangsu Province Chinese Medicine Leading Talents Training Object Project (No. SLJ0327), Nanjing University of Chinese Medicine Gastric Cancer Clinical Specialty Institute Project (No. LCZBYJYZZ2024-001).

Data availability

No datasets were generated or analysed during the current study.

Declarations

Competing interests

The authors declare no competing interests.