Beyond the anti-PD-1/PD-L1 era: promising role of the BTLA/HVEM axis as a future target for cancer immunotherapy

Small molecules from antibody pharmacophores (SMAbPs) as a hit identification workflow for immune checkpoints

Small-molecule modulators of immune checkpoints are poised to revolutionize cancer immunotherapy. However, efficient strategies for hit identification are lacking. We introduce small molecules from antibody pharmacophores (SMAbPs), a workflow leveraging cocrystal structures of checkpoints with antibodies to create pharmacophore maps for virtual screening. Applying SMAbPs to five immune checkpoints yielded hits with submicromolar potency in both cell-free and cellular assays. Notably, SMAbPs identified the most potent T cell immunoglobulin and mucin-domain containing-3 and V-domain immunoglobulin suppressor of T cell activation (VISTA) inhibitors reported to date and first-in-class modulators of B and T lymphocyte attenuator, 4-IBB, and CD27. Targeting inhibitory and costimulatory checkpoints with hits identified through SMAbPs demonstrated remarkable in vivo antitumor activity, exemplified by MG-V-53 (VISTA inhibitor) and MG-C-30 (CD27 agonist), which significantly reduced tumor volumes in MC38 and EG7-OVA mouse models, respectively.

The frontier of neoadjuvant therapy in non-small cell lung cancer beyond PD-(L)1 agents

INTRODUCTION

While surgical resection is the cornerstone of treatment for resectable lung cancer, neoadjuvant/adjuvant chemotherapy has shown limited improvement in survival rates over the past decades. With the success of immune checkpoint inhibitors (ICIs) in advanced NSCLC, there is growing interest in their application in earlier stages of the disease. Recent approvals for neoadjuvant/adjuvant ICIs in stage II-IIIA NSCLC highlight this shift in treatment paradigms.

AREAS COVERED

In this review, we aim to explore available data regarding alternative agents beyond the PD-(L)1 inhibitors, such as monoclonal antibodies against CTLA4, LAG3, TIGIT, antiangiogenic drugs, and novel therapies (antibody drug conjugates, bispecific antibodies) in neoadjuvant/perioperative regimens.

EXPERT OPINION

Novel agents and combinations (with or without ICI or/and chemotherapy), guided by molecular profiling and immune phenotyping, showed promise in improving surgical and survival outcomes. Crucial is, also in early setting, to identifying biomarkers predictive of treatment efficacy in order to personalize neoadjuvant/perioperative treatment strategies.

Focusing on CD8+ T-cell phenotypes: improving solid tumor therapy

Vigorous CD8+ T cells play a crucial role in recognizing tumor cells and combating solid tumors. How T cells efficiently recognize and target tumor antigens, and how they maintain the activity in the "rejection" of solid tumor microenvironment, are major concerns. Recent advances in understanding of the immunological trajectory and lifespan of CD8+ T cells have provided guidance for the design of more optimal anti-tumor immunotherapy regimens. Here, we review the newly discovered methods to enhance the function of CD8+ T cells against solid tumors, focusing on optimizing T cell receptor (TCR) expression, improving antigen recognition by engineered T cells, enhancing signal transduction of the TCR-CD3 complex, inducing the homing of polyclonal functional T cells to tumors, reversing T cell exhaustion under chronic antigen stimulation, and reprogramming the energy and metabolic pathways of T cells. We also discuss how to participate in the epigenetic changes of CD8+ T cells to regulate two key indicators of anti-tumor responses, namely effectiveness and persistence.

Programmed death receptor (PD-)1/PD-ligand (L)1 in urological cancers : the "all-around warrior" in immunotherapy

Programmed death receptor-1 (PD-1) and its ligand, programmed death ligand-1 (PD-L1) are essential molecules that are key in modulating immune responses. PD-L1 is constitutively expressed on various immune cells, epithelial cells, and cancer cells, where it functions as a co-stimulatory molecule capable of impairing T-cell mediated immune responses. Upon binding to PD-1 on activated T-cells, the PD-1/PD-L1 interaction triggers signaling pathways that can induce T-cell apoptosis or anergy, thereby facilitating the immune escape of tumors. In urological cancers, including bladder cancer (BCa), renal cell carcinoma (RCC), and prostate cancer (PCa), the upregulation of PD-L1 has been demonstrated. It is linked to poor prognosis and enhanced tumor immune evasion. Recent studies have highlighted the significant role of the PD-1/PD-L1 axis in the immune escape mechanisms of urological cancers. The interaction between PD-L1 and PD-1 on T-cells further contributes to immunosuppression by inhibiting T-cell activation and proliferation. Clinical applications of PD-1/PD-L1 checkpoint inhibitors have shown promising efficacy in treating advanced urological cancers, significantly improving patient outcomes. However, resistance to these therapies, either intrinsic or acquired, remains a significant challenge. This review aims to provide a comprehensive overview of the role of the PD-1/PD-L1 signaling pathway in urological cancers. We summarize the regulatory mechanism underlying PD-1 and PD-L1 expression and activity, including genetic, epigenetic, post-transcriptional, and post-translational modifications. Additionally, we discuss current clinical research on PD-1/PD-L1 inhibitors, their therapeutic potential, and the challenges associated with resistance. Understanding these mechanisms is crucial for developing new strategies to overcome therapeutic limitations and enhance the efficacy of cancer immunotherapy.

Causal influence of immune factors on the risk of diabetic retinopathy: a mendelian randomization study

OBJECTIVES

Diabetic retinopathy (DR) is a prevalent microvascular complication in diabetic patients. Various mechanisms have been implicated in the pathogenesis of DR. Previous studies have observed the relationship between immune factors and DR, but the causal relationship has not been determined.

METHODS

We conducted a two-sample Mendelian randomization (MR) analysis of 731 immune cells and DR, using publicly available genome-wide association study (GWAS) summary statistics, to evaluate potential causal relationships between them. Four types of immune traits were included in the analysis through flow cytometry. GWAS statistics for DR were obtained from the Finngen database, which performed GWAS on 190,594 European individuals (Ncase = 14,584, Ncontrol = 176,010) to assess genetically predicted DR. The primary method used to perform causality analysis was inverse variance weighting (IVW).

RESULTS

Following false discovery rate (FDR) correction, 11MFI-DR, 5AC-DR, 5RC-DR, and 1MP-DR reached a significant causal association level (PFDR < 0.05). Notably, all AC traits exhibited potential associations with a decreased risk of DR(OR < 1), while a majority of MFI traits, along with the singular MP trait, exhibited potential associations with an increased risk of DR (OR > 1). The highest proportion of T-cell subsets in the final results.

CONCLUSION

This study elucidates that the progression of DR is intricately influenced by immune responses, thereby confirming the immunological susceptibility of DR. Our findings may offer new targets for diagnosing and treating DR, as well as aid in developing therapeutic strategies from an immunological standpoint.

Small cell lung cancer: emerging subtypes, signaling pathways, and therapeutic vulnerabilities

Small cell lung cancer (SCLC) is a recalcitrant cancer characterized by early metastasis, rapid tumor growth and poor prognosis. In recent decades, the epidemiology, initiation and mutation characteristics of SCLC, as well as abnormal signaling pathways contributing to its progression, have been widely studied. Despite extensive investigation, fewer drugs have been approved for SCLC. Recent advancements in multi-omics studies have revealed diverse classifications of SCLC that are featured by distinct characteristics and therapeutic vulnerabilities. With the accumulation of SCLC samples, different subtypes of SCLC and specific treatments for these subtypes were further explored. The identification of different molecular subtypes has opened up novel avenues for the treatment of SCLC; however, the inconsistent and uncertain classification of SCLC has hindered the translation from basic research to clinical applications. Therefore, a comprehensives review is essential to conclude these emerging subtypes and related drugs targeting specific therapeutic vulnerabilities within abnormal signaling pathways. In this current review, we summarized the epidemiology, risk factors, mutation characteristics of and classification, related molecular pathways and treatments for SCLC. We hope that this review will facilitate the translation of molecular subtyping of SCLC from theory to clinical application.

BTLA and PD-1 signals attenuate TCR-mediated transcriptomic changes

T cell co-inhibitory immune checkpoints, such as PD-1 or BTLA, are bona fide targets in cancer therapy. We used a human T cell reporter line to measure transcriptomic changes mediated by PD-1- and BTLA-induced signaling. T cell receptor (TCR)-complex stimulation resulted in the upregulation of a large number of genes but also in repression of a similar number of genes. PD-1 and BTLA signals attenuated transcriptomic changes mediated by TCR-complex signaling: upregulated genes tended to be suppressed and the expression of a significant number of downregulated genes was higher during PD-1 or BTLA signaling. BTLA was a significantly stronger attenuator of TCR-complex-induced transcriptome changes than PD-1. A strong overlap between genes that were regulated indicated quantitative rather than qualitative differences between these receptors. In line with their function as attenuators of TCR-complex-mediated changes, we found strongly regulated genes to be prime targets of PD-1 and BTLA signaling.

The opportunities and challenges of using PD-1/PD-L1 inhibitors for leukemia treatment

Leukemia poses a significant clinical challenge due to its swift onset, rapid progression, and treatment-related complications. Tumor immune evasion, facilitated by immune checkpoints like programmed death receptor 1/programmed death receptor ligand 1 (PD-1/PD-L1), plays a critical role in leukemia pathogenesis and progression. In this review, we summarized the research progress and therapeutic potential of PD-L1 in leukemia, focusing on targeted therapy and immunotherapy. Recent clinical trials have demonstrated promising outcomes with PD-L1 inhibitors, highlighting their role in enhancing treatment efficacy. This review discusses the implications of PD-L1 expression levels on treatment response and long-term survival rates in leukemia patients. Furthermore, we address the challenges and opportunities in immunotherapy, emphasizing the need for personalized approaches and combination therapies to optimize PD-L1 inhibition in leukemia management. Future research prospects include exploring novel treatment strategies and addressing immune-related adverse events to improve clinical outcomes in leukemia. Overall, this review provides valuable insights into the role of PD-L1 in leukemia and its potential as a therapeutic target in the evolving landscape of leukemia treatment.

Modulation of blood T cell polyfunctionality and HVEM/BTLA expression are critical determinants of clinical outcome in anti-PD1-treated metastatic melanoma patients

The need for reliable biomarkers to predict clinical benefit from anti-PD1 treatment in metastatic melanoma (MM) patients remains unmet. Several parameters have been considered in the tumor environment or the blood, but none has yet achieved sufficient accuracy for routine clinical practice. Whole blood samples from MM patients receiving second-line anti-PD1 treatment (NCT02626065), collected longitudinally, were analyzed by flow cytometry to assess the immune cell subsets absolute numbers, the expression of immune checkpoints or ligands on T cells and the functionality of innate immune cells and T cells. Clinical response was assessed according to Progression-Free Survival (PFS) status at one-year following initiation of anti-PD1 (responders: PFS > 1 year; non-responders: PFS ≤ 1 year). At baseline, several phenotypic and functional alterations in blood immune cells were observed in MM patients compared to healthy donors, but only the proportion of polyfunctional memory CD4+ T cells was associated with response to anti-PD1. Under treatment, a decreased frequency of HVEM on CD4+ and CD8+ T cells after 3 months of treatment identified responding patients, whereas its receptor BTLA was not modulated. Both reduced proportion of CD69-expressing CD4+ and CD8+ T cells and increased number of polyfunctional blood memory T cells after 3 months of treatment were associated with response to anti-PD1. Of upmost importance, the combination of changes of all these markers accurately discriminated between responding and non-responding patients. These results suggest that drugs targeting HVEM/BTLA pathway may be of interest to improve anti-PD1 efficacy.

The Immune Checkpoint BTLA in Oral Cancer: Expression Analysis and Its Correlation to Other Immune Modulators

In oral squamous cell carcinoma (OSCC) tissues, an immunotolerant situation triggered by immune checkpoints (ICPs) can be observed. Immune checkpoint inhibitors (ICIs) against the PD1/PD-L axis are used with impressive success. However, the response rate is low and the development of acquired resistance to ICI treatment can be observed. Therefore, new treatment strategies especially involving immunological combination therapies need to be developed. The novel negative immune checkpoint BTLA has been suggested as a potential biomarker and target for antibody-based immunotherapy. Moreover, improved response rates could be displayed for tumor patients when antibodies directed against BTLA were used in combination with anti-PD1/PD-L1 therapies. The aim of the study was to check whether the immune checkpoint BTLA is overexpressed in OSCC tissues compared to healthy oral mucosa (NOM) and could be a potential diagnostic biomarker and immunological target in OSCC. In addition, correlation analyses with the expression of other checkpoints should clarify more precisely whether combination therapies are potentially useful for the treatment of OSCC. A total of 207 tissue samples divided into 2 groups were included in the study. The test group comprised 102 tissue samples of OSCC. Oral mucosal tissue from 105 healthy volunteers (NOM) served as the control group. The expression of two isoforms of BTLA (BTLA-1/2), as well as PD1, PD-L1/2 and CD96 was analyzed by RT-qPCR. Additionally, BTLA and CD96 proteins were detected by IHC. Expression levels were compared between the two groups, the relative differences were calculated, and statistical relevance was determined. Furthermore, the expression rates of the immune checkpoints were correlated to each other. BTLA expression was significantly increased in OSCC compared to NOM (pBTLA_1 = 0.003; pBTLA_2 = 0.0001, pIHC = 0.003). The expression of PD1, its ligands PD-L1 and PD-L2, as well as CD96, were also significantly increased in OSCC (p ≤ 0.001). There was a strong positive correlation between BTLA expression and that of the other checkpoints (p < 0.001; ρ ≥ 0.5). BTLA is overexpressed in OSCC and appears to be a relevant local immune checkpoint in OSCC. Thus, antibodies directed against BTLA could be potential candidates for immunotherapies, especially in combination with ICI against the PD1/PD-L axis and CD96.

γδ T cells and the PD-1/PD-L1 axis: a love-hate relationship in the tumor microenvironment

Gamma delta (γδ) T cells demonstrate strong cytotoxicity against diverse cancer cell types in an MHC-independent manner, rendering them promising contenders for cancer therapy. Although amplification and adoptive transfer of γδ T cells are being evaluated in the clinic, their therapeutic efficacy remains unsatisfactory, primarily due to the influence of the immunosuppressive tumor microenvironment (TME). Currently, the utilization of targeted therapeutic antibodies against inhibitory immune checkpoint (ICP) molecules is a viable approach to counteract the immunosuppressive consequences of the TME. Notably, PD-1/PD-L1 checkpoint inhibitors are considered primary treatment options for diverse malignancies, with the objective of preserving the response of αβ T cells. However, γδ T cells also infiltrate various human cancers and are important participants in cancer immunity, thereby influencing patient prognosis. Hence, it is imperative to comprehend the reciprocal impact of the PD-1/PD-L1 axis on γδ T cells. This understanding can serve as a therapeutic foundation for improving γδ T cells adoptive transfer therapy and may offer a novel avenue for future combined immunotherapeutic approaches.

Targeting BTLA with the peptide inhibitor HVEM(14-39) - A new way to restore the activity of T cells in melanoma

The complex of B- and T-lymphocyte attenuator (BTLA) and herpes virus entry mediator (HVEM) plays a critical role in immune regulation and has emerged as a promising therapeutic target for cancer treatment. In this study, we investigated the potential of the peptide inhibitor HVEM(14-39) to restore peripheral T cell activity in patients with advanced melanoma. In these patients, CD8+ T cells downregulated BTLA expression and increased HVEM expression upon activation. The addition of HVEM(14-39) reduced the percentage of BTLA+ CD8+ T cells and increased the subpopulation of HVEM+ CD8+ T cells. Additionally, HVEM(14-39) enhanced T cell activation, proliferation, and the shift toward effector memory T cell subpopulations. Finally, this peptide affected the proliferation rate and late apoptosis of melanoma cell line in co-culture with T cells. These findings suggest that HVEM(14-39) can overcome T cell exhaustion and improve antitumor responses. Peptide-based immunotherapy targeting the BTLA-HVEM complex offers a promising alternative to monoclonal antibody-based therapies, with the potential for fewer side effects and higher treatment efficacy.

The BTLA-HVEM axis restricts CAR T cell efficacy in cancer

The efficacy of T cell-based immunotherapies is limited by immunosuppressive pressures in the tumor microenvironment. Here we show a predominant role for the interaction between BTLA on effector T cells and HVEM (TNFRSF14) on immunosuppressive tumor microenvironment cells, namely regulatory T cells. High BTLA expression in chimeric antigen receptor (CAR) T cells correlated with poor clinical response to treatment. Therefore, we deleted BTLA in CAR T cells and show improved tumor control and persistence in models of lymphoma and solid malignancies. Mechanistically, BTLA inhibits CAR T cells via recruitment of tyrosine phosphatases SHP-1 and SHP-2, upon trans engagement with HVEM. BTLA knockout thus promotes CAR signaling and subsequently enhances effector function. Overall, these data indicate that the BTLA-HVEM axis is a crucial immune checkpoint in CAR T cell immunotherapy and warrants the use of strategies to overcome this barrier.

Immune checkpoint inhibitors: breakthroughs in cancer treatment

Over the past two decades, immunotherapies have increasingly been considered as first-line treatments for most cancers. One such treatment is immune checkpoint blockade (ICB), which has demonstrated promising results against various solid tumors in clinical trials. Monoclonal antibodies (mAbs) are currently available as immune checkpoint inhibitors (ICIs). These ICIs target specific immune checkpoints, including cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein 1 (PD-1). Clinical trial results strongly support the feasibility of this immunotherapeutic approach. However, a substantial proportion of patients with cancer develop resistance or tolerance to treatment, owing to tumor immune evasion mechanisms that counteract the host immune response. Consequently, substantial research focus has been aimed at identifying additional ICIs or synergistic inhibitory receptors to enhance the effectiveness of anti-PD-1, anti-programmed cell death ligand 1 (anti-PD-L1), and anti-CTLA-4 treatments. Recently, several immune checkpoint molecular targets have been identified, such as T cell immunoreceptor with Ig and ITIM domains (TIGIT), mucin domain containing-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), V-domain immunoglobulin suppressor of T cell activation (VISTA), B and T lymphocyte attenuator (BTLA), and signal-regulatory protein α (SIRPα). Functional mAbs targeting these molecules are under development. CTLA-4, PD-1/PD-L1, and other recently discovered immune checkpoint proteins with distinct structures are at the forefront of research. This review discusses these structures, as well as clinical progress in mAbs targeting these immune checkpoint molecules and their potential applications.

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Herpesvirus Entry Mediator as an Immune Checkpoint Target and a Potential Prognostic Biomarker in Myeloid and Lymphoid Leukemia

Herpesvirus entry mediator (HVEM) is a molecular switch that can modulate immune responses against cancer. The significance of HVEM as an immune checkpoint target and a potential prognostic biomarker in malignancies is still controversial. This study aims to determine whether HVEM is an immune checkpoint target with inhibitory effects on anti-tumor CD4+ T cell responses in vitro and whether HVEM gene expression is dysregulated in patients with acute lymphocytic leukemia (ALL). HVEM gene expression in tumor cell lines and peripheral blood mononuclear cells (PBMCs) from ALL patients and healthy controls was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Tumor cells were left untreated (control) or were treated with an HVEM blocker before co-culturing with CD4+ T cells in vitro in a carboxyfluorescein succinimidyl ester (CFSE)-dependent proliferation assay. HVEM expression was upregulated in the chronic myelogenous leukemia cell line (K562) (FC = 376.3, p = 0.086) compared with normal embryonic kidney cells (Hek293). CD4+ T cell proliferation was significantly increased in the HVEM blocker-treated K562 cells (p = 0.0033). Significant HVEM differences were detected in ALL PBMCs compared with the controls, and these were associated with newly diagnosed ALL (p = 0.0011) and relapsed/refractory (p = 0.0051) B cell ALL (p = 0.0039) patients. A significant differentiation between malignant ALL and the controls was observed in a receiver operating characteristic (ROC) curve analysis with AUC = 0.78 ± 0.092 (p = 0.014). These results indicate that HVEM is an inhibitory molecule that may serve as a target for immunotherapy and a potential ALL biomarker.

Exploring the regulatory mechanism of intestinal flora based on PD-1 receptor/ligand targeted cancer immunotherapy

Serving as a pivotal immunotherapeutic approach against tumors, anti-PD-1/PD-L1 therapy amplifies the immune cells' capability to eliminate tumors by obstructing the interaction between PD-1 and PD-L1. Research indicates that immune checkpoint inhibitors are effective when a patient's gut harbors unique beneficial bacteria. As such, it has further been revealed that the gut microbiome influences tumor development and the efficacy of cancer treatments, with metabolites produced by the microbiome playing a regulatory role in the antitumor efficacy of Immune checkpoint inhibitors(ICBs). This article discusses the mechanism of anti-PD-1 immunotherapy and the role of intestinal flora in immune regulation. This review focuses on the modulation of intestinal flora in the context of PD-1 immunotherapy, which may offer a new avenue for combination therapy in tumor immunotherapy.

Pan-immune inflammation value as a prognostic biomarker for cancer patients treated with immune checkpoint inhibitors

Background

Immune checkpoint inhibitors (ICIs) represent a paradigm shift in the development of cancer therapy. However, the improved efficacy of ICIs remains to be further investigated. We conducted a systematic review and meta-analysis to evaluate the pan-immunoinflammatory value (PIV) and PILE score used to predict response to ICI therapy.

Methods

We searched selected databases for studies on pan-immune inflammation values and their association with outcomes of treatment with immune checkpoint inhibitors. We used hazard ratios (HRS) and 95% confidence intervals (CI) to summarize survival outcomes. All data analyses were performed using STATA 15.0.

Results

7 studies comprising 982 patients were included in the meta-analysis. The pooled results showed that higher PIV was significantly associated with shorter overall survival OS (HR = 1.895, 95%CI: 1.548-2.318) and progression-free survival (PFS) (HR = 1.582, 95%CI: 1.324-1.890). Subgroup analyses also confirmed the reliability of the results.

Conclusions

High PIV and PILE metrics are associated with lower survival in cancer patients receiving ICIs.

[A pan-cancer analysis of TTC9A expression level and its correlation with prognosis and immune microenvironment]

OBJECTIVE

To investigate the expression level of tetratricopeptide repeat protein 9A in tumors and its association with the patients' prognosis and immune infiltration.

METHODS

TTC9A expression in different tumor tissues and its association with prognosis, DNA methylation, tumor mutation burden (TMB), and microsatellite instability (MSI) were analyzed based on data from TCGA and GTEx. TIMER and xCell were used to analyze the relationship between TTC9A expression and immune infiltration. Western blotting and RT-qPCR were used to detect the expression of TTC9A in 4 types of cancer cell lines.

RESULTS

TTC9A expressions were significantly increased in many tumors and down-regulated in a few cancer types (P < 0.05). Western blotting and RT-qPCR showed that TTC9A expressions were elevated in lung, colon and liver cancer cells but decreased in bladder cancer cells. In head and neck squamous cell carcinoma, renal clear cell carcinoma, renal papillary cell carcinoma, low-grade glioma, malignant mesothelioma, and endometrial carcinoma tumors, a high expression of TTC9A was strongly correlated with better overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) (P < 0.05), but was correlated with worse OS, DSS, and PFI in lung adenocarcinoma, pancreatic adenocarcinoma, adrenal carcinoma, and rectal adenocarcinoma (P < 0.05). TTC9A hypermethylation was associated with a more favorable prognosis of glioblastoma multiforme, low- grade glioma, uveal melanoma, and ovarian plasmacytoid cystadenocarcinoma (P < 0.05) but with poor prognosis of squamous cell carcinoma of the uterine cervix and intracervical adenocarcinoma, squamous cell carcinoma of head and neck, squamous cell carcinoma of the lungs, adrenal carcinoma, and endometrial carcinoma (P < 0.05). In most of the cancer types, TTC9A was significantly correlated with the level of immune cell infiltration (P < 0.05).

CONCLUSION

TTC9A can be used as a prognostic marker for a variety of cancers and is strongly associated with TBM, MSI and immune cell infiltration.