Interferon Gamma Inducible Protein 30: from biological functions to potential therapeutic target in cancers

Abstract

Interferon Gamma Inducible Protein 30 (IFI30), also known as Gamma-Interferon-Inducible Lysosomal Thiol Reductase (GILT), is predominantly found in lysosomes and the cytoplasm. As the sole enzyme identified to catalyze disulfide bond reduction in the endocytic pathway, IFI30 contributes to both major histocompatibility complex (MHC) class I-restricted antigen cross-presentation and MHC class II-restricted antigen processing by decreasing the disulfide bonds of endocytosed proteins. Remarkably, emerging research has revealed that IFI30 is involved in tumorigenesis, tumor development, and the tumor immune response. Targeting IFI30 may provide new strategies for cancer therapy and improve the prognosis of patients. This review provided a comprehensive overview of the research progress on IFI30 in tumor progression, cellular redox status, autophagy, tumor immune response, and drug sensitivity, with a view to providing the theoretical basis for pharmacological intervention of IFI30 in tumor therapy, particularly in immunotherapy.

Introduction

Interferon Gamma Inducible Protein 30 (IFI30), one of the interferon-stimulated genes (ISGs) [1], encodes the only known lysosomal thiol reductase (IFI30), also referred to as Gamma-Interferon-Inducible Lysosomal Thiol Reductase (GILT). ISGs are a class of genes that can be inducibly upregulated by interferon (IFN), which is commonly divided into three types: Type I IFN (IFN-α and IFN-β), Type II IFN (IFN-γ), and Type III IFN (IFN-λ) [2]. IFN-γ has been shown to regulate the expression of numerous ISGs, whose distinct expression patterns confer various effects, such as inhibiting growth, enhancing immune cell-mediated killing, triggering apoptosis, and other pro-tumorigenic functions like the increased cancer cell stemness and the expression of immunosuppressive ISGs [2]. The promoter of IFI30 contains the IFN-γ-specific response elements and, therefore, IFI30 is defined as an IFN-γ-specific ISG [3]. Synthesized as a precursor and undergoing mature form in the endosome/lysosome system, IFI30 is constitutively expressed in many antigen-presenting cells [4–6], and also induced by IFN-γ in other cell types.

IFI30, the sole enzyme known to catalyze disulfide bond reduction in the endocytic pathway, has been increasingly recognized for its crucial involvement in the progression of various diseases, particularly in tumor immunosurveillance. Enhancing major histocompatibility complex (MHC) class I and class II-restricted processing and presentation of antigens containing disulfide bonds is the most well-known role of IFI30. IFI30 catalyzes the reduction of disulfide bonds in a low pH environment [7], relaxes the tertiary structure of the antigen, and exposes hidden binding areas to enhance CD4⁺ and CD8⁺ T-cell responses against various cancers [8, 9]. Notably, more research conducted in recent years has revealed that IFI30, which is aberrantly expressed in a range of tumors, including diffuse large B-cell lymphoma (DLBCL) [6], melanoma [10–12], glioma [13], and breast cancer [14, 15], exerts indispensable roles in tumorigenesis, progression, and immunosurveillance, potentially serving as a target for tumor therapy. However, IFI30 might have distinct roles in various types of tumors. Consequently, a comprehensive understanding of IFI30’s function in tumor progression might offer new perspectives on tumor-targeted therapy and rationale to improve immunotherapy’s efficacy.

Here, the roles of IFI30 in tumor progression, cellular redox status, autophagy, tumor microenvironment, and drug sensitivity were reviewed, along with the underlying molecular mechanisms. We also summarized the current knowledge on the expression, regulation, and physiological functions of IFI30. This review gave a thorough overview of IFI30’s function in cancer and offered new perspectives on immunotherapy and tumor-targeted therapy.

Biological characterization of IFI30

Primarily located in endosomes, lysosomes, phagosomes, and cytoplasm [16], IFI30 exhibits maximal reductase activity at the acidic pH range of 4.5 to 5.5 and is the only sulfhydryl reductase in the family of thioredoxin reductases that operates in acidic environments [17]. Human IFI30 is a secreted protein containing 261 amino acids, which includes a 224-amino acid precursor form and a 37-amino acid functional signal sequence. The 35 kDa precursor is tagged with mannose-6-phosphate (M6P) residues, which then enter the lysosome through the M6P receptor (M6PR)-mediated endocytosis pathway. N-acetylglucosamine-1-phosphotransferase (GNPT) catalyzes the transfer of GlcNAc-1-phosphate from UDP-GlcNAc to the C6-hydroxyl groups of specific mannose residues of the IFI30 precursor in the endoplasmic reticulum and early Golgi. The phosphodiester bond is subsequently hydrolyzed by the uncovering enzyme (UCE), releasing GlcNAc and exposing mannose-6-phosphate (M6P) residues, which are recognized by M6P receptors (M6PRs) [4, 18]. M6P-tagged IFI30 precursors are transported to the endosome or lysosome via the M6PR-mediated endocytosis pathway. The IFI30 precursor’s N- and C-terminal propeptides are then cleaved into a 30 kDa mature form. A small amount of the precursor can be secreted outside the cell as a dimer [4] (Fig. 1).

Fig. 1.

Mechanistic and functional roles of IFI30 in cancers. (a) Mechanism of IFI30 expression, regulation and secretion. (b) Overexpressed IFI30 promotes EMT and enhances cancer cell proliferation, migration, invasion, and chemoresistance by activating the EGFR/AKT/GSK3β/β-catenin pathway to up-regulate the expression of Slug, or activating the IL6-STAT6 signaling pathway. (c) The oncogenic effects of IFI30 are manifested by promoting tumor immunosuppressive cell infiltration (e.g., TAM) and immune checkpoint expression. (d) IFI30 exerts an inhibitory effect on the proliferation and progression of various cancers by suppressing oxidative stress, regulating autophagy, and increasing the sensitivity to radiotherapy and chemotherapy through stimulation of multiple oncogenic signals. (e) IFI30 contributes to MHC class I and II-restricted antigen processing presentation and may determine the efficiency of CD8⁺ and CD4⁺ T cell responses. The figure was created by BioRender (https://biorender.com/)

IFI30 is highly expressed in antigen-presenting cells (APCs) including bone marrow-derived dendritic cells (DC), B-cells (progenitor and cell lineage), and monocytes/macrophages [4, 5, 18–20], but also to some degree in some fibroblasts, mature T-cells, and thymocytes. In other cell types [21], such as melanoma cell lines, human umbilical vein endothelial cells, immature monocytes and monocyte progenitors, IFI30 is either induced by inflammatory agents like IFN-γ. IFI30 is involved in the reduction of protein disulfide bonds and regulates the processing of both endogenous and exogenous antigens [22]. In addition to regulating MHC class II-restricted antigen presentation and CD4⁺ T cell activation [18], IFI30 is also involved in MHC class I-restricted exogenous antigen processing and presentation, which in turn activates CD8⁺ T cell and regulates the body’s antiviral and anti-tumor immune response [23].

Expression and regulation of IFI30

The expression of IFI30 is significantly upregulated by IFN-γ. The promoter region upstream of the first exon of the IFI30 gene sequence contains two gamma-activated sequences (GAS), which are the specific sequences activated by IFN-γ [3]. IFN-γ promotes the expression of IFI30 in fibrosarcoma and melanoma cell lines through the janus kinase (JAK) / signal transducer and activator of transcription 1(STAT1) pathway [7]. The transcription factor STAT1 undergoes phosphorylation and dimerization, binds to the IFI30 promoter, and rapidly increases its expression. Nevertheless, it was found that STAT1 may exert a dual role in regulating IFI30 expression [24], with STAT1 repressing IFI30 expression in the absence of IFN-γ through direct interaction with the IFI30 promoter. In addition, the differentiation of macrophages serves as a distinctive mechanism for triggering IFI30 expression. Immature monocytes are induced to differentiation by treatment with phorbol 12-myristate 13-acetate (PMA) or Toll-Like Receptor 4 (TLR-4) ligands, which in turn trigger IFI30 expression through the nuclear factor kappa-B (NF-κB) signaling pathway and Interferon Regulatory Factor 3 (IRF3) [20].

Functional roles of IFI30 in the immune system

IFI30 in antigen processing and presentation

IFI30 is the only reductase known to enhance MHC class II-restricted antigen processing and presentation by reducing protein disulfide bonds [25]. The reduction and unfolding of protein disulfide bonds, damaged in IFI30^−/− mice [18], is essential for exposing antigenic epitopes and binding antigenic molecules to MHC class II molecules. The reductase active site of IFI30 is composed of a thioredoxin-like CXXC motif containing Cys-46 and Cys-49 (Fig. 2), as indicated by in vitro studies. The Cys-46 thiol group undergoes a nucleophilic attack on the substrate disulfide bond to form an IFI30-substrate mixed disulfide intermediate [16], followed by an intramolecular attack of the Cys-49 thiol, leading to the release of the reduced substrate and oxidized IFI30. The substrate is further hydrolyzed and digested by lysosomal proteins to generate antigenic peptides that bind to MHC class II, thereby stimulating T cells [26]. Cys-46 or Cys-49 mutations eliminate IFI30-dependent MHC Class II antigenic epitope processing [9]. The dependence of IFI30 relies on whether the antigenic epitopes necessitate reduction to be exposed for MHC class II binding, and the topology of certain epitopes that is sufficient to denature the region for Class II binding even in the absence of reduction by IFI30 or at acidic pH alone. Furthermore, IFI30 also participates in the MHC class II-restricted antigen presentation by directly binding to alleles of MHC class II molecules, such as human leukocyte antigen DR (HLA-DR), and co-localizing with HLA-DM and HLA-DR in phagosomal vesicles [9]. In melanoma, IFI30 may contribute to the MHC class II epitope presentation of multiple melanoma antigens (TRP1, TRP2, and gp100) and stimulate melanoma-specific CD4⁺ T cell activation [27, 28].

Fig. 2.

The roles of IFI30 in the process of antigen processing and presentation. The process of MHC class I cross-presentation in antigen-presenting cells involves the translocation of exogenous proteins from the phagosome to the cytoplasm. Prior to retrotransport into the cytoplasm, the large proteins within the phagosome must be unfolded and/or partially cleaved. IFI30 promotes the unfolding, protein hydrolysis, and reverse transport of disulfide-bond-containing antigens, facilitating the generation of MHC class I peptide complexes that activate CD8 T cells (Left). MHC class II molecules are synthesized in the endoplasmic reticulum, form heterodimers, and bind to Ii. The MHC II-Ii complex is directed toward the endocytosis pathway guided by the cytoplasmic tail of Ii. The process of antigen hydrolysis and sequence cleavage of Ii, which permits CLIP binding in the MHC class II peptide-binding groove, is carried out by cathepsins. Mature IFI30 is localized in lysosomes and late endosomes, where it catalyzes the disulfide bond reduction of proteins [16]. IFI30 promotes the generation of MHC class II-peptide complexes in response to HLA-DM and stimulates CD4 T cells (Right). The figure was created by BioRender (https://biorender.com/)

IFI30, in addition to affecting MHC I-restricted recognition and cross-presentation of antigens [23], has also been implicated in the MHC class II-restricted presentation of antigens containing disulfide bonds [18]. Cross-presentation refers to the processing of viral, tumor, or exogenous antigens for presentation by MHC class I molecules to CD8⁺ T cells. In APCs (mainly dendritic cells and phagocytes), antigens or antigen fragments are translocated from the phagosome to the cytoplasm, where they are further degraded by the proteasome and transported to the endoplasmic reticulum via the TAP transporter. Peptides with the appropriate length and sequence in the endoplasmic reticulum bind to newly synthesized MHC class I molecules to activate CD8⁺ T cells [29]. Phagocytosed or endocytosed antigens must be unfolded and/or partially proteolyzed for translocation into the cytoplasm, and disulfide-bond-containing antigens require reduction by IFI30 for optimal cross-presentation (Fig. 2). Based on in vivo study, IFI30 facilitates the activation of CD8⁺ T cells via enhancing MHC class I-restricted cross-presentation, transforming them into cytotoxic T cells, and subsequently sensitize colon carcinoma cells to enhanced immune surveillance [30]. The recognition and initiation of certain influenza A virus hemagglutinin and neuraminidase antigenic epitopes by CD8⁺ T cells in vivo are also regulated by IFI30.

Thus, IFI30 contributes to MHC class I and II-restricted antigen processing and presentation, potentially influencing the efficiency of CD8⁺ and CD4⁺ T cell responses.

The roles of IFI30 in the proliferation, maturation and activation of T cells

IFI30 plays a crucial role in the immune system’s processing and presentation of antigens, while also reducing T cell autoreactivity. Constitutively expressed in T cells, IFI30 is mainly co-localized with lysosome-associated membrane protein 2 (LAMP-2). The level of IFI30 appears to be developmentally regulated by T cells. The low levels of IFI30 observed in immature thymocytes (CD4⁺CD8⁺ T cells) were increased in mature thymocytes (CD4⁺/CD8⁺ T cells) and even further in peripheral T cells. IFI30 has been reported to inhibit T cell proliferation and activation [31], and to diminish T cell sensitivity and autoimmune responses [32].

On the one hand, IFI30 may negatively regulate T-cell activation by reducing the disulfide bonds of certain T-cell surface molecules, such as the TCR/CD3 complex. The TCRα and TCRβ chains are connected by disulfide bonds [33, 34], and each chain contains Ig-like domains that may be the target for thiol reductase. On the other hand, activation of extracellular regulated protein kinases (ERK1/2) is required for the positive selection of T cells. IFI30-deficient T cell exhibits a higher level of superoxide anion due to the decreased superoxide dismutase 2 (SOD2), followed by a more pronounced phosphorylation of ERK1/2 and induction of CD69 upon CD3 engagement, allowing for a better response to TCR-induced cytotoxicity [32] and a significant increase in T-cell sensitivity. Furthermore, IFI30 also manipulates redox potential in T cells by eliminating reactive oxygen species (ROS), thereby inhibiting T cell activation [35, 36]. It has been shown that the half-life of ROS may be prolonged in the absence of IFI30, leading to stronger activation of IFI30-deficient T cells [31]. The contact between IFI30 and ROS can be achieved either by diffusion of the latter into the lysosomes, or indirectly by the effect of IFI30 on molecules that can be translocated (passively or actively) through the lysosomal membrane.

In addition, the upregulation of IFI30 in T cells infiltrating sites of inflammation is thought to degrade local T cell function. Indeed, T cells infiltrating tumors are frequently functionally defective [37], and the expression of IFI30 in T cells from patients with metastases of breast cancer [38], medulloblastoma [39], and DLBCL [40] was considerably higher than that in patients without metastases, indicating that the oncogenic function of IFI30 partly through regulating the immunosuppressor process of T cells [41]. Therefore, regulating IFI30 expression may be a key strategy for modulating inflammatory and immunological responses.

Expression and function of IFI30 in tumors

Expression of IFI30 in cancers

The expression of IFI30 varies in different cancers. We summarized the expression pattern of IFI30 in malignancies based on The Cancer Genome Atlas (TCGA) dataset (Fig. 3). 18 of 33 tumors’ mRNA expression levels of IFI30 were significantly higher than those in paraneoplastic tissues, including bladder uroepithelial carcinoma (BLCA), breast invasive carcinoma (BRCA), cervical squamous cell carcinoma (CESC), colon adenocarcinoma (COAD), esophageal carcinoma (ESCA), Glioblastoma multiforme (GBM), head and neck squamous cell carcinoma (HNSC), low-grade glioma (LGG), liver hepatocellular carcinoma (LIHC), ovarian serous cystadenocarcinoma (OV), pancreatic adenocarcinoma (PAAD), rectum adenocarcinoma (READ), skin cutaneous melanoma (SKCM), stomach adenocarcinoma (STAD), testicular germ cell tumors (TGCT), thyroid carcinoma (THCA), uterine corpus endometrial carcinoma (UCEC), and uterine carcinosarcoma (UCS). The mRNA level of IFI30 was lower than that of paraneoplastic tissues only in thymoma (THYM), which may indicate an underpinning role of IFI30 in the immune system.

Fig. 3.

Expression of IFI30 in various cancers based on TCGA database. Gene Expression Profiling Interactive Analysis (GEPIA) was used to analyze mRNA expression levels of IFI30 in cancers and adjacent tissues

However, emerging studies identified significant heterogeneity of IFI30 expression in certain cancers compared to normal tissues actually, which has been observed in DLBCL [6, 42, 43], melanoma [10, 44], breast cancer [14, 45], etc., suggesting that IFI30 may affect the clinical prognosis of different types of cancers. In addition, in GBM [46] and clear cell renal carcinoma (ccRCC) [47, 48], IFI30 is significantly up-regulated and correlates with poor prognosis. In conclusion, the aberrant expression in cancers suggests that IFI30 may be a potential therapeutic target for specific cancer types.

IFI30 in the progression of tumor

Aberrant expression of IFI30 is strongly linked to the progression of certain types of malignant tumors. We summarized the relationship between IFI30 and the survival of different cancer patients based on survival correlation analysis, specifically overall survival (OS) and disease-specific survival (DSS). As shown in Fig. 4, IFI30 plays distinct roles in various malignancies. The Cox proportional hazards (PH) model analysis revealed a substantial correlation between the expression of IFI30 with OS and DSS in GBM, LGG, acute myeloid leukemia (LAML), uveal melanoma (UVM), THYM, CESC, SKCM, and OV. Among them, patients with higher IFI30 expression in GBM, LGG, LAML, UVM, and THYM exhibited lower survival rates. Consistent with the survival analysis, studies have provided further evidence that higher IFI30 expression in GBM and gliomas with a mesenchymal subtype or wild-type isocitrate dehydrogenase is associated with lower survival in patients [12, 44, 49]. Silencing IFI30 inhibits cell proliferation, colony formation, migration, and tumor growth, and induces apoptosis and cell-cycle arrest, hence suppressing the malignant progression of GBM [13, 46, 50, 51]. IFI30 also promotes stemness, epithelial-mesenchymal transition (EMT), cellular invasion, and chemoresistance [52, 53] by increasing the nuclear translocation of β-catenin, facilitating the activation of the epidermal growth factor receptor (EGFR)/protein kinase B (AKT)/GSK3β pathway, and up-regulating Slug expression, which could serve as an independent indicator for poor prognosis in GBM (Fig. 1). Furthermore, elevated expression of IFI30 is regarded as a risk factor and has also been shown to be associated with reduced patient survival in prostate cancer [42, 43], and with low responsiveness to treatment in acute myeloid leukemia (AML) [54]. Due to its overexpression with a poor prognosis caused by immune cell infiltration, IFI30 was recently found to be negatively associated with survival and was identified as a potential biomarker and immunotherapeutic target for gastric cancer (GC) [55] and ccRCC [47, 48, 56, 57].

Fig. 4.

Association between IFI30 expression with overall survival (OS) and disease-specific survival (DSS). Survival data were obtained from the TCGA database. (a) Forest plot of the association between IFI30 expression and OS in 33 types of tumors. (b) Forest plot of the association between IFI30 expression and DSS in 33 types of tumors

On the contrary, patients with high IFI30 expression were strongly associated with prolonged survival in CESC, SKCM and OV. The overexpression of IFI30 was initially demonstrated to be associated with improved survival in DLBCL [6]. Subsequently, IFI30, as an independent gene, was positively linked with survival in adenocarcinoma of the esophagogastric junction (AEG) and chromosomal unstable gastric cancers [58]. Recently, IFI30 was additionally discovered to be associated with improved survival in melanoma [11, 44, 59] and cervical cancer [60] due to its high expression, intact MHC II antigen presentation pathway and cooperation with CD8⁺ T cell infiltration. However, the role of IFI30 in breast cancer is rather debatable. It has been suggested that the deficiency of IFI30 is related to low disease-free survival in breast cancer patients [15], and that IFI30 inhibits proliferation, migration and invasion of breast cancer cells by suppressing ROS production and autophagy, thereby enhancing sensitivity to cancer treatment [14]. Nevertheless, other research has reached the opposite conclusion, suggesting that IFI30 enhances the proliferation, migration and invasion of breast cancer cells. These contrasting conclusions may be related to breast cancer subtypes, which have different pathogenesis, prognosis, and systemic therapeutic options. Still, the exact mechanism of IFI30 in different subtypes of breast cancer remains unknown.

Overall, IFI30 plays an indispensable role in the development of malignant tumors such as melanoma, GBM and breast cancer. The dual effects demonstrated by IFI30 in distinct cancers imply that IFI30 may regulate specific targets and signaling pathways, and the characteristics and mechanisms of its action still need a deeper exploration.

IFI30 in tumor oxidative stress

IFI30 modulates the cellular oxidoreductive status and critically impacts cell proliferation and autophagy. The deficiency of IFI30 is associated with an overall increase in intracellular oxidative stress and autophagy levels [32, 61, 62]. Deletion of IFI30 increases intracellular ROS in breast cancer cells [14], leading to a shift in the glutathione disulfide (GSSG)/glutathione (GSH) ratio towards the oxidized form (GSSG), which decreases mitochondrial membrane potential and elevates oxidative stress levels. IFI30 deficiency further increases mitochondrial autophagy by activating the ERK1/2 signaling pathway and promoting the translocation of the nuclear high mobility group box 1 (HMGB1) protein into the cytoplasm [61], and the increased clearance of damaged mitochondria subsequently reduces the amount of mitochondrial proteins including SOD2, resulting in a further increase in superoxide levels. Increased ROS also stimulate the phosphorylation and nuclear translocation of the transcription factor forkhead box O (FOXO), affecting the transcription and protein-coding of multiple target genes including p21 and p27 [50, 63], which may further elucidate the IFI30-induced dysregulation of SOD2 expression and cell cycle-related proteins. In addition, ROS also triggers autophagy by directly altering proteins associated with autophagy [64] (Fig. 1).

Moreover, IFI30 also dramatically regulates the oxidoreductive state and proliferation of fibroblasts and T cells. Deficiency of IFI30 in fibroblasts and T cells elevates ROS levels, decreases the expression and activity of SOD2, and increases the ratio of GSSG/GSH [32, 61, 65], ultimately promoting cell proliferation [31, 65].

Currently, there are few studies on IFI30 in oxidative stress. However, the existing studies indicate that IFI30 may affect tumor progression by altering the cellular oxidoreductive status. Further understanding of IFI30’s role in redox homeostasis is crucial to identifying potential targets for tumor therapy.

IFI30 in tumor autophagy

Alterations in tumor autophagy are caused by mutations in key autophagy genes or inappropriate activation of autophagy regulators, which are intimately associated with tumorigenesis, progression, and drug sensitivity. Tumorigenesis is associated with decreased autophagy, which contributes to the expression of oncogenes and the degradation of damaged components or proteins in oxidatively stressed cells. Conversely, with the progression of cancer, activation of autophagy enhances tumor stress tolerance and facilitates tumor progression by delivering nutrients and fulfilling the metabolic needs of proliferating tumors. The formation of a trimer composed of Beclin-1, phosphatidylinositol 3-kinase (PI3K) (Vps34), and autophagy-related gene 14 (ATG14) has been reported to mediate the initiation of autophagy. In the presence of ATG4, the LC3 precursor is processed into soluble LC3-I, which is covalently conjugated to phosphatidylethanolamine via ATG7, ATG3, and the ATG12-ATG5-ATG16L1 complex to generate LC3-II. After binding to ubiquitinated proteins, p62 combines with LC3-II, which is localized on the inner membrane of autophagosomes, to produce a complex that is subsequently degraded in autophagic lysosomes [66]. In recent years, IFI30 has been found to regulate tumor autophagy. In melanoma and breast cancer, IFI30 significantly induced the expression of Beclin-1, while promoting the degradation of LC3I, LC3II, and lysosomes [45, 67], and increased the sensitivity to radiotherapy. However, the opposite conclusion was obtained in a proteomics-based investigation, where overexpression of IFI30 down-regulated ATG5 and ATG7 in breast cancer cells, indicating that IFI30 might suppress autophagy via altering proteins associated with autophagy directly [14]. Furthermore, enhanced autophagy was also observed in IFI30-deficient fibroblasts [61]. The previous results also confirmed the potential of IFI30 in regulating tumor autophagy [45, 61, 67], whereas the precise mechanisms underlying IFI30’s diverse impacts on tumor autophagy may depend on the subtype and the stage of cancer, and the in-depth mechanisms need to be further investigated (Fig. 1).

The role of IFI30 in tumor immunity and immune microenvironment

Antigen processing and presentation is the key mechanism for the immune system to recognize and target tumor cells and begins with the internalization of tumor-associated antigens by APCs [68], which then combine with MHC molecules to form complexes. The MHC-peptide complexes are transported to the cell surface [69], where T cells are activated upon recognizing them, resulting in an effective anti-tumor response. Through the inhibition of antigen expression, modification of antigen processing and presentation capabilities, and creation of an immunosuppressive microenvironment, tumor cells can evade recognition and destruction by the immune system. As IFI30 is a specific sulfhydryl reductase in the thioredoxin reductase family, overexpression of IFI30 improves the presentation of disulfide-bond-containing MHC class I and II-restricted antigenic epitopes, which enhances CD4⁺ and CD8⁺ T-cell responses against a wide range of tumors by reducing the disulfide bonds, loosening the tertiary structure of the antigen, and exposing the hidden binding regions [8, 9]. Several melanoma antigens (Ags) have been proposed as immunotherapeutic targets, including tyrosinase, TRP1, TRP2, NY-ESO-1, gp-100, and Mart-1, all of which contain MHC I/II-restricted epitopes and require IFI30-dependent MHC molecules for optimal presentation [27, 28, 70]. However, the study including 16 human melanoma cell lines revealed that melanoma cells expressing MHC class I/II-restricted antigenic molecules with low or no IFI30 expression were unable to present the MHC class I/II-restricted epitopes of the endogenous melanoma antigen [27], which may be one of the mechanisms of immune evasion. Exogenous enhancement of IFI30 generates a greater pool of antigenic peptides in melanoma cells to enhance CD4⁺/CD8⁺ T cell recognition [10]. The immunological response in colon cancer is also markedly improved by overexpression of IFI30, which increases MHC class I molecules and supports antigen presentation to cytotoxic CD8⁺ T cells [30]. In addition to elevating HLA-DM molecules, IFI30 also plays a pivotal role in Ag processing by stimulating acid cathepsin activity and destroying disulfide bonds formed during cysteinylation. IFI30 dramatically elevates the activity of cysteinyl proteases, cathepsins B, L and S, and the aspartyl protease cathepsin D in melanoma cells, which in turn facilitates epitope loading onto MHC class II molecular in the endolysosomal compartments and enhancing CD4⁺ T cell recognition [22]. Moreover, cysteinylation is an important aspect of peptide modification, and cysteinylated Ags form strong disulfide bonds that necessitate further IFI30-dependent endosome processing before being loaded onto HLA-DR molecules for efficient stimulation of T-cells. Prostate-specific membrane antigen PSMA⁺⁺459 epitopes are cysteinylated at normal physiological concentrations of cystine, thereby inhibiting T-cell activation. IFI30 inserted into prostate cancer cells reduces cysteinylation in endosomal and lysosomal, and directly enhances MHC class II antigen processing and the presentation of PSMA⁺⁺459 epitope, resulting in increased CD4⁺ T cell activation [71]. On the other hand, IFI30-mediated processing and presentation of disulfide-bonded self-antigens epitopes were shown to be potentially involved in shaping central tolerance, contributing to the manipulation of thymic selection to alter T cell function. In thymic APCs, particularly medullary thymic epithelial cells (mTECs), IFI30 preferentially promotes MHC Class II-restricted presentation and negative selection of thymic, enhances central T-cell tolerance, and restricts the function of T cells recognizing the melanoma-associated self-antigens [59]. The aforementioned studies revealed the important role of IFI30-mediated MHC class I and II-restricted antigen processing and presentation in tumor immunity. Overexpression of IFI30 may further increase the sensitivity to immune checkpoint therapy [11] and aid in the development of a novel whole-cell vaccine utilizing IFI30 transfection ex vivo to enhance tumor immune recognition, which may represent a new strategy for anti-tumor immunity. However, IFI30-mediated central tolerance to tumor self-antigens limits T-cell responses to potentially immunodominant tumor epitopes, which may be an essential issue that cannot be ignored in developing IFI30 as a target for cancer immunotherapy.

The tumor microenvironment (TME) is a complex and dynamic interaction between tumor cells and surrounding stromal tissue. The surrounding stromal tissue consists of heterogeneous cell populations including immune cells, fibroblasts, and endothelial cells. The macrophage in the tumor microenvironment is also called tumor-associated macrophage (TAM), including anti-tumorigenic M1 and pro-tumorigenic M2 phenotypes. With high heterogeneity, M2 macrophages have complex and diverse functions including promoting tumor proliferation and metastasis, stimulating tumor neovascularization, inducing the formation of immunosuppressive microenvironment and promoting immune escape. With tumor progression, TAM polarizes toward the M2 phenotype, with significantly reduced expression of MHC class I/II and suppressed antigen presentation, showing a pro-tumorigenic effect, which may account for IFI30’s conflicting functions throughout the immune response in various cancers. Many studies have confirmed that overexpression of IFI30 in GBM is associated with poor prognosis and immunosuppressive microenvironment [49, 50, 72]. GBM patients with elevated IFI30 also exhibit a large infiltration of M2-type macrophage and high expression of immune checkpoints including CD163, programmed cell death 1 ligand 1 (PD-L1), and interleukin 10 (IL-10) [49, 50]. In hepatocellular carcinoma, massive M2 macrophage infiltration was also discovered to coexist with elevated IFI30 expression [73]. As a secreted protein in a co-culture system of lung cancer cells and monocytes, IFI30 also promoted metastasis and immune evasion of cancer cells [74]. In addition, overexpression of IFI30 in breast cancer has also been shown to significantly promote TAM polarization toward the M2 phenotype and increase the expression of PD-L1, which targets programmed death protein 1 (PD-1) on activated T cells, leading to increased immune evasion and CD8⁺ T cell depletion [75]. Targeting IFI30 could potentially affect the efficacy of PD-L1 blockade. Also, IFI30 directly participates in the maturation and activation of T cells [8, 61, 70]. Modulation of the IFI30-TAM-T cell axis could be a prospective strategy to regulate the functional infiltration of T cells in cancer immunotherapy. Collectively, the expression of IFI30 reflects TME formation and prominently influences the immune response status of macrophages. Although IFI30 suppresses tumor progression by augmenting the expression of MHC class I/II molecules in TAM, improving the presentation of disulfide-bond-containing MHC-restricted antigenic epitopes, facilitating effector cell recruitment, and orchestrating innate and adaptive antitumor responses. However, the above studies also revealed an innovative mechanism of IFI30-mediated immunosuppression by promoting TAM recruitment and polarization (M2), as well as immune checkpoint expression. The overall balance and timing of IFI30 expression and downstream signaling pathways during tumor development may critically determine effective versus suppressive immune responses as well as the immunological profile of immunotherapeutic approaches. The therapeutic efficacy of the IFI30-TAM-T cell axis may depend on balancing its pro- and anti-tumorigenic effects, and additional research is required to understand its safety and toxicity profile comprehensively.

Based on previous findings, we think that IFI30 regulates tumor immunity mainly through two aspects: (1) IFI30 can directly participate in the processing and presentation of tumor-specific antigens, and facilitate the generation of MHC-peptide complexes, thus strengthening the T cell immune response. (2) IFI30 can also exert its oncogenic effects by increasing tumor immunosuppressive cell infiltration (e.g. TAM) and immune checkpoint expression. The contrasting effects of IFI30 on the immune response of various cancers, are potentially due to the tumor’s immunogenicity. Contrary to immunogenic tumors (hot tumors, e.g., melanoma), non-immunogenic tumors (cold tumors, e.g., GBM, hepatocellular carcinoma) are characterized by low T-cell infiltration, low tumor mutational load, and immunosuppressive tumor microenvironment. Due to the absence of surface antigens in non-immunogenic tumors, IFI30 is functionally limited in antigen processing and presentation, which in turn promotes the proliferation and infiltration of tumor-immunosuppressive cells (e.g., M2-type macrophages). Given that IFI30 is aberrantly expressed in multiple cancers, the immunomodulatory function of IFI30 in other solid tumors, particularly pancreatic cancer, which is intrinsically resistant to immunotherapy, is unclear. Furthermore, considering the essential role of IFI30 in antigen processing and presentation, we can’t ignore the potential risks for patients during IFI30-targeted therapy (Fig. 1).

IFI30 and tumor resistance

Studies have indicated that IFI30 is linked to drug resistance [52, 54, 56], which is common in tumor therapy. Through the autophagy-lysosomal degradation pathway, IFI30 inhibits paired box gene 3 (PAX-3), a potential target in advanced metastatic melanoma. Additionally, it upregulates the expression of p53 and the tumor suppressor protein Daxx, which greatly increases the sensitivity of melanoma cells to chemotherapy or low-dose radiotherapy [67]. In colorectal cancer (CRC), drug sensitivity (IC50 values) also showed that patients in the high IFI30 group were more sensitive to agents such as stauroporine, ERK_2440, alpelisib, cisplatin, 5-fluorouracil, entospletinib, dihydrorotenone, taf15496, eriotinib, AZD3759, gefitinib, and osimertinib [76]. The potential role of IFI30 in breast cancer therapeutic sensitivity is firstly confirmed by its association with increased sensitivity of breast cancer cells to chemotherapy, anti-HER2 therapy and radiotherapy [14]. Conversely, the diversity of IFI30’s role in breast cancer is also reflected in a significant positive correlation ( r = + 0.82; P < 0.05) with the magnitude of anthracycline resistance in breast tumor cells, with temporal and causal relationships [77].

Nevertheless, dysregulation of IFI30 appears to confer chemoresistance in GBM, relapsed/refractory (R/R) AML and GC. Somatic mutation studies of GBM patients revealed that IDH1 and ATRX were more frequently mutated in the low IFI30 group, while the wild-type of IDH1 and ATRX had a higher incidence of temozolomide (TMZ) resistance [78, 79]. In addition, IFI30 can directly or indirectly down-regulate the chemosensitivity of glioma cells to TMZ through the transcription factor Slug [52] or the IL6-STAT6 signaling pathway [49], which is considered a classical target of tumor chemoresistance (Fig. 1). In R/R AML, IFI30 promotes resistance to MEC (mitoxantrone, etoposide, cytarabine) combined with ixazomib by increasing the level of antioxidants and decreasing endoplasmic-reticulum stress response [54]. In GC, screening by the Cancer Genome Project (CGP) database, the low IFI30 group demonstrated reduced IC-50 values for cisplatin, eletriptolide, FMK, GSK1070916, GSK429286A, HG-5-113-01, T0901317, and tarazole Pani [55], which suggests that patients with low IFI30 expression are more sensitive to chemotherapy.

In summary, the aforementioned studies further enhance the potential of IFI30 in modulating drug resistance in tumors. Even while the outcomes differ, they are basically consistent with the previous roles of IFI30 in the respective tumors, which will contribute to the development of IFI30-targeted chemotherapy and provide a new rationale for more effective anti-tumor combination therapies.

Drug candidates targeting IFI30 in cancer

According to ClinicalTrials.gov and Cortellis Drug Discovery Intelligence (CDDI), there are currently no drug candidates targeting IFI30 for the treatment of cancer in clinical trials. In the preclinical stage, there are also fewer compounds have been reported to inhibit tumor progression by affecting IFI30 expression. Crucially, Ye et al. discovered that the proliferation of breast cancer cells treated with IFI30 recombinant protein was significantly suppressed [14], which preliminarily corroborated the potential value of IFI30 in treating breast cancer and laid an important foundation for subsequent research and application. Frondanol A5, a sea cucumber extract, improves the innate immune system of CRC mice by increasing the expression of IFI30 and the phagocytosis macrophage to exert anti-CRC effects [80]. Propofol, a commonly used intravenous anesthetic, reduces IFI30 expression via modulating the circ_0047688/miR-516b-5p axis to suppress GBM progression [81], providing a viable therapeutic avenue for GBM treatment. In addition, it was preliminarily found that lapatinib and PD-0332991 (palbociclib) were the most potent IFI30 inhibitors by screening 481 and 518 molecules in the GTRPv2 and GDSC databases. Further experimental validation is needed to confirm these findings [75].

The above drug candidates’ effects on tumor progression were not directly evaluated in animal models or clinical trials, and the mechanistic explorations mainly relied on in vitro experiments with cell lines or isolated cells, which might not accurately reflect the complex and variable in vivo conditions. Consequently, the results may not translate directly into therapeutic benefits for cancer patients, and further study will have to be done to develop more effective drug candidates targeting IFI30.

Conclusion and future perspective

Cancer has become a major public health problem in the world. With in-depth studies on tumor biology, immunology, and molecular biology, numerous promising cancer therapeutic targets have been identified for different characteristics of cancers, such as FXYD3 [82] for cancer stem cells and miR-182 [83] for cancer immunity. Over the past few years, the study of IFI30 has come a long way. As the only known lysosomal thiol reductase in the endocytosis pathway, IFI30 is regarded as a crucial target for enhancing MHC-restricted antigen processing and presentation. IFI30 possesses unique advantages in regulating tumorigenesis, including stimulating the processing and presentation of MHC class I and II-restricted antigens; modulating T-cell proliferation, maturation, and activation; facilitating the infiltration of immunosuppressive cells and the expression of immune checkpoints to establish a tumor-immunosuppressive microenvironment; maintaining the cellular oxidoreductive state and regulating autophagy. Targeting IFI30 synergistically enhances anti-tumor immune responses with ICBs, new combination strategies for tumor immunotherapy and novel cell therapy and/or vaccines utilizing IFI30 transfection ex vivo are being actively developed. IFI30 could be a promising therapeutic target for the treatment of cancers and the reversal of drug resistance.

However, some challenging questions remain to be addressed. There are many controversies about the function of IFI30 in cancers, with conflicting findings observed in breast cancer [14, 15, 45]. We initially speculate that these discrepancies may be related to the diversity of tumor subtypes and gene mutations, which contribute to variations in tumor immunogenicity. GBM, triple-negative breast cancer and other non-immunogenic tumors weaken the function of IFI30 in antigen processing and presentation due to their low T-cell infiltration and tumor antigen deficiency. Instead, IFI30 promotes the proliferation and infiltration of tumor-immunosuppressive cells, and increases immune checkpoint expression to exert its oncogenic effect, which is associated with poor prognosis. Therefore, the characteristics and intrinsic molecular mechanisms of IFI30 in different tumors and subtypes still need to be further explored, and the delicate regulation of IFI30 and combination therapy targeting specific tumor subtypes may prove to be a crucial area for future research. Furthermore, IFI30 is abnormally expressed in a variety of cancers, but the regulation of its expression, especially epigenetic regulation, remains unclear. Bioinformatics analysis indicates a decrease in the methylation level of the IFI30 promoter, and more in-depth experiments are still needed in the future.

IFI30 has been identified as a new biomarker for multiple cancers that can be easily applied in the clinic by serological or immunohistochemical (IHC) assays for predicting patients’ prognosis, immune profile, and drug sensitivity, with great potential for guiding systemic therapy based on IFI30 expression. Up to date, however, there is no drug candidate targeting IFI30 for the treatment of cancer in clinical trials. The exploration of potential compounds, recombinant proteins, vaccines and cell therapies targeting IFI30 holds promising prospects and may offer novel approaches to enhance the effectiveness of tumor immunotherapy. Finally, given the fundamental physiological function of IFI30 in antigen processing and presentation as well as in the regulation of autoimmunity, the potential negative effects of fighting bacterial and viral infections must be taken into account while investigating anti-tumor therapies targeting IFI30. Therefore, the development of new therapy candidates that selectively target IFI30 in cancer to avoid potential off-target effects is an important future direction.

Author contributions

S.Z: Writing– original draft, Visualization. L.R: Data curation. W.L: Data curation. Y.Z: Data curation. Y.Y: Visualization. H.Y: Visualization. F.X: Visualization. W.C: Visualization. X.L: Visualization. X.Z: Visualization. G.D: Conceptualization, Supervision. J.W: Conceptualization, Supervision.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethical approval

Not applicable.

Competing interests

The authors declare no competing interests.