Immune suppression caused by PD-L2 expression on tumor cells in gastric cancer

Study of immunosenescence in the occurrence and immunotherapy of gastrointestinal malignancies

In human beings heterogenous, pervasive and lethal malignancies of different parts of the gastrointestinal (GI) tract viz., tumours of the oesophagus, stomach, small intestine, colon, and rectum, represent gastrointestinal malignancies. Primary treatment modality for gastric cancer includes chemotherapy, surgical interventions, radiotherapy, monoclonal antibodies and inhibitors of angiogenesis. However, there is a need to improve upon the existing treatment modality due to associated adverse events and the development of resistance towards treatment. Additionally, age has been found to contribute to increasing the incidence of tumours due to immunosenescence-associated immunosuppression. Immunosenescence is the natural process of ageing, wherein immune cells as well as organs begin to deteriorate resulting in a dysfunctional or malfunctioning immune system. Accretion of senescent cells in immunosenescence results in the creation of a persistent inflammatory environment or inflammaging, marked with elevated expression of pro-inflammatory and immunosuppressive cytokines and chemokines. Perturbation in the T-cell pools and persistent stimulation by the antigens facilitate premature senility of the immune cells, and senile immune cells exacerbate inflammaging conditions and the inefficiency of the immune system to identify the tumour antigen. Collectively, these conditions contribute positively towards tumour generation, growth and eventually proliferation. Thus, activating the immune cells to distinguish the tumour cells from normal cells and invade them seems to be a logical strategy for the treatment of cancer. Consequently, various approaches to immunotherapy, viz., programmed death ligand-1 (PD-1) inhibitors, Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors etc are being extensively evaluated for their efficiency in gastric cancer. In fact, PD-1 inhibitors have been sanctioned as late late-line therapy modality for gastric cancer. The present review will focus on deciphering the link between the immune system and gastric cancer, and the alterations in the immune system that incur during the development of gastrointestinal malignancies. Also, the mechanism of evasion by tumour cells and immune checkpoints involved along with different approaches of immunotherapy being evaluated in different clinical trials will be discussed.

Roles of plasma proteins in mediating the causal effect of the lipid species on gastric cancer: Insights from proteomic and two-step Mendelian randomization

The change of plasma lipid species has close contacts with gastric cancer (GC). However, the specific mechanism still needs to be explored further. We aim to utilize plasma proteins to decipher the association between lipid species and GC, and seek possible drug targets for GC. We performed a two-step Mendelian randomization (MR) analysis to investigate causal relationships among 179 lipid species, 4907 plasma proteins, and GC. Using summary-data-based MR and colocalization, we first examined protein-GC associations in discovery (N = 35,559) and validation (N = 54,219) cohorts. Subsequent MR analyses assessed lipid-GC and lipid-protein relationships, followed by mediation analysis using error propagation methods. Finally, macromolecular docking of prioritized proteins identified potential therapeutic ligands. Our MR analysis revealed causal relationships between 12 lipid species and GC, as well as 3 plasma proteins and GC. Importantly, mediation analysis demonstrated that CCDC80 protein mediates 2.90% (95% CI: 0.30-5.5%) of the protective effect of diacylglycerol (16:1_18:1) against GC. Based on these findings, we identified valproic acid as a promising therapeutic candidate targeting CCDC80 for GC treatment. Our study demonstrates that reduced CCDC80 expression mediates the tumor-promoting effects of diacylglycerol (16:1_18:1) in GC pathogenesis. Molecular docking confirms valproic acid binds stably to CCDC80, suggesting its therapeutic potential. These findings advance GC etiology understanding and provide a new drug development direction.

Modulation of N-glycosylation in the PD-1: PD-L1 axis as a strategy to enhance cancer immunotherapies

The modulation of the N-glycosylation status in immune checkpoints, particularly the PD-1/PD-L1 axis, has emerged as a promising approach to enhance cancer immunotherapies. While immune checkpoint inhibitors (ICIs) targeting PD-1 and PD-L1 have achieved significant clinical success, recent studies highlight the critical role of N-glycosylation in regulating their expression, stability, and function. Alterations in N-glycosylation might affect the efficacy of ICIs by modulating the interactions between immune checkpoints and antibodies used in therapy. This review focuses on the glycosylation of PD-1 and its ligands PD-L1 and PD-L2, examining how N-glycans influence immune responses and contribute to immune evasion by tumors. It explores innovative strategies to modulate glycosylation in tumor and immune cells, including the use of N-glycosylation inhibitors and novel genetic manipulation techniques. Understanding the interplay between N-glycosylation and immune checkpoint functions is essential for optimizing immunotherapy outcomes and overcoming therapeutic resistance in cancer patients.

PD-L2 of tumor-derived exosomes mediates the immune escape of cancer cells via the impaired T cell function

The function of PD-1/PD-L1 axis have been intensively studied for immune escape of various cancers. However, the underlying function of PD-L2 remains poorly understood. Here, we demonstrate that PD-L2 is majorly expressed in exosomes with surface localization by clear cell renal cell carcinoma (ccRCC) cells. Tumor cell-derived exosome PD-L2 (TDE-PD-L2) exhibits high expression compared with TDE-PD-L1 in various cancers. In the absence of adaptive immune, TDE-PD-L2 suppresses tumor growth and metastasis. Under immune competence condition, TDE-PD-L2 is hijacked by immune cells in a PD-1-dependent manner to systematically dampen function of T cells via the increased proportion of the regulatory T cells and the decreased proportion of cytotoxic CD8+ T cells in both tumor-infiltrating T cells and spleen. The effects of TDE-PD-L2 on tumor is restored by antibodies targeting PD-L2. Collectively, we demonstrate that PD-1/TDE-PD-L2 axis systematically suppresses T cell functions, representing a potentially therapeutic strategy for ccRCC treatment.

Identification of lncRNA dual targeting PD-L1 and PD-L2 as a novel prognostic predictor for gastric cancer

Background

Although breakthroughs have been achieved in gastric cancer (GC) therapy with immune checkpoint inhibitors (ICIs) targeting programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1), the acquisition of high response rate remains a huge challenge for clinicians. It is imperative to identify novel biomarkers for predicting response to immunotherapy and explore alternative therapeutic strategy for GC.

Methods

The transcriptomic profiles and clinical information of GC patients from The Cancer Genome Atlas (TCGA)-stomach adenocarcinoma (STAD) database was used to screen differentially expressed lncRNAs between the tumor specimens and the paracancerous tissues. The TargetScan, miRDB and miRcode database were then utilized to construct competing endogenous RNA (ceRNA) networks and identify pivotal lncRNAs. An independent dataset from GEO (GSE70880) and 23 pairs of GC specimens of our cohort were subsequently performed for external validity. The relationship between clinical variables and gene expression were evaluated by Kruskal-wallis test and Wilcoxon signed-rank. The prognostic value of the candidate genes was assessed using Kaplan-Meier analysis and Cox regression models. CIBERSORT and Gene set enrichment analysis (GSEA) were used to determine immune cell infiltration. Gastric adenocarcinoma AGS cells and human embryonic kidney 293T (HEK293T) cells with knockdown of LINC01094 were generated by siRNA transfection, followed by detecting the alteration of the target miRNA and PD-L1/PD-L2 by RT-qPCR. Besides, the interaction between lncRNA and the miRNA-PD-L1/PD-L2 axis were verified by dual luciferase reporter assay.

Results

Twenty-two intersecting lncRNAs were identified to be PD-L1/PD-L2-related lncRNAs and LINC01094-miR-17-5p-PD-L1/PD-L2 was constructed as a potential ceRNA network. LINC01094 was increased in tumor specimens than adjacent normal samples and was positively associated with advanced tumor stages and EBV and MSI status. Furthermore, LINC01094 expression was an independent risk factor for poor overall survival (OS) in GC patients. CD8+ T cell exhaustion-related genes were enriched in high-LINC01094 tissues and high-PD-L2 group. A strong positive association of LINC01094 expression was established with M2 macrophages, IL-10+ TAM, as well as PD-L1 and PD-L2 levels, therefore a LINC01094-miR-17-5p-IL-10 network was proposed in macrophages. Using the exoRBase database, LINC01094 was assumed in blood exosomes of GC patients The results of knockdown experiments and luciferase reporter assays revealed that LINC01094 interacted with miR-17-5p and served as a miRNA sponge to regulate the expression of PD-L1 and PD-L2.

Conclusion

LINC01094 dually regulates the expression of PD-L1 and PD-L2 and shapes the immunosuppressive tumor microenvironment via sponging miR-17-5p. LINC01094 may serve as a potential prognostic predictor and therapeutic target in GC.

Aberrant DNA polymerase beta expression is associated with dysregulated tumor immune microenvironment and its prognostic value in gastric cancer

BACKGROUND

Gastric cancer is caused by different exogenous risk factors. Polymerase beta (POLB) is critical to repair oxidative and alkylating-induced DNA damage in genome maintenance. It is unknown whether overexpression of POLB genes in GC modulates tumor immunogenicity and plays a role in its prognostic value.

METHODS

RNA-Seq of GC data retrieved from TCGA and GEO database and patient survival were compared using Kaplan-Meier statistical test. The TIMER algorithm was used to calculate the abundance of tumor-infiltrating immune cells. Furthermore, ROC analysis was applied to evaluate the prognostic value of POLB overexpression.

RESULTS

Our data analysis of TCGA and GEO gastric cancer genomics datasets reveals that POLB overexpression is significantly associated with intestinal subtypes of stomach cancer. In addition, POLB overexpression is associated with low expression of innate immune signaling genes. In contrast, POLB-overexpressed tumor harbors high mutation frequency and MSI score. Furthermore, POLB-overexpressed tumor with high immune score exhibits a better prognosis. Interestingly, our ROC analysis results suggested that POLB overexpression has a potential for prognostic markers for stomach cancer.

CONCLUSIONS

Our analysis suggests that aberrant POLB overexpression in stomach cancer impacts the diverse aspects of tumor immune microenvironment. In addition, POLB might be a potential prognosis marker and/or an attractive target for immune-based therapy in GC. However, our observation still requires further experimental-based scientific validation studies.

SPHK1 promotes bladder cancer metastasis via PD-L2/c-Src/FAK signaling cascade

SPHK1 (sphingosine kinase type 1) is characterized as a rate-limiting enzyme in sphingolipid metabolism to phosphorylate sphingosine into sphingosine-1-phosphate (S1P) that can bind to S1P receptors (S1PRs) to initiate several signal transductions leading to cell proliferation and survival of normal cell. Many studies have indicated that SPHK1 is involved in several types of cancer development, however, a little is known in bladder cancer. The TCGA database analysis was utilized for analyzing the clinical relevance of SPHK1 in bladder cancer. Through CRISPR/Cas9 knockout (KO) and constitutive activation (CA) strategies on SPHK1 in the bladder cancer cells, we demonstrated the potential downstream target could be programmed cell death 1 ligand 2 (PD-L2). On the other hand, we demonstrated that FDA-approved SPHK1 inhibitor Gilenya® (FTY720) can successfully suppress bladder cancer metastasis by in vitro and in vivo approaches. This finding indicated that SPHK1 as a potent therapeutic target for metastatic bladder cancer by dissecting the mechanism of action, SPHK1/S1P-elicited Akt/β-catenin activation promoted the induction of PD-L2 that is a downstream effector in facilitating bladder cancer invasion and migration. Notably, PD-L2 interacted with c-Src that further activates FAK. Here, we unveil the clinical relevance of SPHK1 in bladder cancer progression and the driver role in bladder cancer metastasis. Moreover, we demonstrated the inhibitory effect of FDA-approved SPHK1 inhibitor FTY720 on bladder cancer metastasis from both in vitro and in vivo models.

PD-L2 Expression in Breast Cancer Promotes Tumor Development and Progression

Background

This work focused on investigating the role of programmed death ligand 2 (PD-L2) in the progression of breast cancer by utilizing breast cancer specimens and cells.

Materials and Methods

The serum levels of soluble PD-L2 (sPD-L2) in breast cancer patients and healthy individuals were analyzed by means of the enzyme-linked immunosorbent assay, and the PD-L2 levels within 416 resected breast cancer specimens were assessed through immunohistochemistry. Concurrently, in vitro cell experiments and in vivo animal experiments were carried out to analyze the relationship between PD-L2 and the invasion and migration of breast cancer.

Results

The concentration of sPD-L2 in breast cancer patients significantly increased compared to that in the control groups. Additionally, breast cancer patients with high concentrations of sPD-L2 had higher Ki67 values (≥30%) and tumor grades. PD-L2 was expressed in 79.09% of the cancer samples, which exhibited a positive correlation with the progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2). Furthermore, we discovered that knockdown of PD-L2 inhibited the migratory and invasive abilities of both MCF-7 and MDA-MB231 cells.

Conclusion

Our findings demonstrated that knockdown of PD-L2 suppressed tumor growth, providing novel insights into important biological functions.

Biomarker-oriented chemo-immunotherapy for advanced gastric cancer

The biomarker-oriented chemo-immunotherapy is useful and promising in the development of new anticancer agents, since the responders can be enriched by selecting patients with biomarkers. Compared to colorectal and lung cancers, the development of biomarker-driven molecular-targeted therapeutics for gastric cancers has been straggled. However, several new biomarkers in gastric cancers have been discovered and clinical trials in enrichment design with certain biomarkers have been conducted. Therefore, there are currently several treatment options to treat gastric cancer patients based on individual biomarker-oriented strategies. In the present review, we describe the useful biomarkers in gastric cancer, with focusing on HER2, PD-L1, and Claudin18.2, in relation to their clinical significance and associated targeted agents.

Evaluation of soluble co-inhibitors and co-stimulators levels of the immune response in gastric cancer

BACKGROUND

Co-inhibitor and co-stimulator mediators trigger actions that result in immunological homeostasis and are being evaluated as potential therapeutic targets in gastric cancer (GC).

OBJECTIVE

To evaluate the soluble levels of sPD-1, sPD-L1, sPD-L2, sTIM-3, sGal9, sGITR, and sGITRL in GC patients.

METHODS

The cross-sectional study was carried out at the Hospital de Cancer de Pernambuco, Brazil between 2017 and 2018. A total of 74 GC patients and 30 healthy controls were included.

RESULTS

Low levels of sPD1 (p = 0.0179), sPDL2 (p = 0.0003), and sGal9 (p < 0.0001), and higher levels of sPDL1 (p = 0.004), sTIM-3 (p = 0.0072), sGITR (p = 0.0179), and sGITRL (p = 0.0055) compared to the control group. High sPD-1, sTIM-3, and sGal9 levels in stage IV compared I/II and III (p < 0.05). High sPDL1, sGal9, and sGITRL levels in esophagogastric junction compared to body and Pylorus/Antrum groups (p < 0.05). No significant differences were observed in sPD1, sPDL1, sPDL2, sTIM3, sGal9, sGITR, and sGITRL levels between the intestinal, diffuse, and mixed GC groups. Low sGITR levels in GC patients who died within the first 24 months compared to the who survived (p = 0.0332).

CONCLUSIONS

There is an association of sPD1, sTIM-3, and sGal9 with disease progression and sGITR with death, these mediators may be potential prognostic biomarkers in GC.

Programmed cell death-ligand 2: new insights in cancer

Immunotherapy has revolutionized cancer treatment, with the anti-PD-1/PD-L1 axis therapy demonstrating significant clinical efficacy across various tumor types. However, it should be noted that this therapy is not universally effective for all PD-L1-positive patients, highlighting the need to expedite research on the second ligand of PD-1, known as Programmed Cell Death Receptor Ligand 2 (PD-L2). As an immune checkpoint molecule, PD-L2 was reported to be associated with patient's prognosis and plays a pivotal role in cancer cell immune escape. An in-depth understanding of the regulatory process of PD-L2 expression may stratify patients to benefit from anti-PD-1 immunotherapy. Our review focuses on exploring PD-L2 expression in different tumors, its correlation with prognosis, regulatory factors, and the interplay between PD-L2 and tumor treatment, which may provide a notable avenue in developing immune combination therapy and improving the clinical efficacy of anti-PD-1 therapies.

Comparison of Clinical Trial Results of the Recently Approved Immunotherapeutic Drugs for Advanced Biliary Tract Cancers

The recently approved immunotherapeutic drugs are Keytruda (pembrolizumab) and Imfinzi (durvalumab) for advanced biliary tract cancers that inhibit PD-1 receptor and PD-L1 ligand, respectively. In this perspective, the results of the two clinical trials, i.e., TOPAZ-1 (NCT03875235) and KEYNOTE-966 (NCT04003636), are critically appraised, compared, and discussed to assess the benefits of these two drugs in the context of the treatment of advanced biliary tract cancers with a focus on PD-L1 status and MIS (microsatellite instability) status and therapy responsiveness in the subgroups. Analyzing the PD-L2 status in biliary tract cancer patients can aid in assessing the prognostic value of PD-L2 expression in determining the clinical response and this may aid in appropriate patient stratification.

Immunology and immunotherapy in gastric cancer

Gastric cancer is the fifth leading cause of cancer-related deaths worldwide. As the diagnosis of early gastric cancer is difficult, most patients are at a late stage of cancer progression when diagnosed. The current therapeutic approaches based on surgical or endoscopic resection and chemotherapy indeed improve patients' outcomes. Immunotherapy based on immune checkpoint inhibitors has opened a new era for cancer treatment, and the immune system of the host is reshaped to combat tumor cells and the strategy differs according to the patient's immune system. Thus, an in-depth understanding of the roles of various immune cells in the progression of gastric cancer is beneficial to application for immunotherapy and the discovery of new therapeutic targets. This review describes the functions of different immune cells in gastric cancer development, mainly focusing on T cells, B cells, macrophages, natural killer cells, dendritic cells, neutrophils as well as chemokines or cytokines secreted by tumor cells. And this review also discusses the latest advances in immune-related therapeutic approaches such as immune checkpoint inhibitors, CAR-T or vaccine, to reveal potential and promising strategies for gastric cancer treatment.

Integrated single-cell RNA sequencing analysis reveals a mesenchymal stem cell-associated signature for estimating prognosis and drug sensitivity in gastric cancer

BACKGROUND

Mesenchymal stem cells (MSCs) play an important role in regulating all stages of the immune response, angiogenesis, and transformation of matrix components in the tumor microenvironment. The aim of this study was to identify the prognostic value of MSC-related signatures in patients with gastric cancer (GC).

METHODS

MSC marker genes were identified by analyzing single-cell RNA sequencing (scRNA-seq) data for GC from the Gene Expression Omnibus (GEO) database. Using bulk sequencing data from the Cancer Genome Atlas-Stomach adenocarcinoma (TCGA-STAD), as a training cohort, and data from GEO, as a validation cohort, we developed a risk model consisting of MSC prognostic signature genes, and classified GC patients into high- and low-MSC risk subgroups. Multifactorial Cox regression was used to evaluate whether MSC prognostic signature was an independent prognostic factor. An MSC nomogram was constructed combining clinical information and risk grouping. Subsequently, we evaluated the effect of MSC prognostic signature on immune cell infiltration, antitumor drugs and immune checkpoints and verified the expression of MSC prognostic signature by in vitro cellular assays.

RESULTS

In this study, 174 MSC marker genes were identified by analyzing scRNA-seq data. We identified seven genes (POSTN, PLOD2, ITGAV, MMP11, SDC2, MARCKS, ANXA5) to construct MSC prognostic signature. MSC prognostic signature was an independent risk factor in the TCGA and GEO cohorts. GC patients in the high-MSC risk group had worse prognoses. In addition, the MSC nomogram has a high clinical application value. Notably, the MSC signature can induce the development of a poor immune microenvironment. GC patients in the high MSC-risk group were more sensitive to anticancer drugs and tended to have higher levels of immune checkpoint markers. In qRT-PCR assays, the MSC signature was more highly expressed in GC cell lines.

CONCLUSIONS

The MSC marker gene-based risk signature developed in this study can not only be used to predict the prognosis of GC patients, but also has the potential to reflect the efficacy of antitumor therapies.

Nivolumab versus irinotecan as third- or later-line treatment for advanced gastric cancer: a multi-center retrospective study

BACKGROUND

The present study aimed to compare the efficacy and safety of nivolumab (NIVO) and irinotecan (IRI) and to identify clinical factors that facilitate treatment selection.

METHODS

Patients with advanced gastric cancer (AGC) who underwent NIVO or IRI treatment between November 2016 and June 2018 at three institutions were retrospectively reviewed. The inclusion criteria were histologically confirmed gastric/gastroesophageal adenocarcinoma pretreated with fluoropyrimidines and taxanes, no previous NIVO or IRI treatment, and adequate organ function. Main outcome measures were objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and adverse events. Interaction between treatment groups and clinical factors regarding OS were tested using a multivariate Cox proportional hazards model adjusted for relevant variables.

RESULTS

Both NIVO (n = 71) and IRI (n = 61) groups had similar baseline characteristics, except for sex distribution. NIVO and IRI groups had ORR of 20% and 6%, median PFS of 1.6 and 1.8 months, and median OS of 6.4 and 6.4 months, respectively. Interaction analysis did not reveal any significant interaction between NIVO and IRI related to OS for various factors. NIVO group tended to have fewer ≥ grade 3 adverse events than IRI group, especially neutropenia (3% vs. 28%) and febrile neutropenia (1% vs. 8%). In the NIVO group, one patient developed pneumonitis, and four patients developed skin reactions.

CONCLUSIONS

Although no remarkable differences in efficacy were found between IRI and NIVO for AGC, NIVO had a better safety profile compared to IRI. We found no clinical markers that can assist treatment decisions.

Evolving landscape of PD-L2: bring new light to checkpoint immunotherapy

Immune checkpoint blockade therapy targeting programmed cell death protein 1 (PD-1) has revolutionized the landscape of multiple human cancer types, including head and neck squamous carcinoma (HNSCC). Programmed death ligand-2 (PD-L2), a PD-1 ligand, mediates cancer cell immune escape (or tolerance independent of PD-L1) and predicts poor prognosis of patients with HNSCC. Therefore, an in-depth understanding of the regulatory process of PD-L2 expression may stratify patients with HNSCC to benefit from anti-PD-1 immunotherapy. In this review, we summarised the PD-L2 expression and its immune-dependent and independent functions in HNSCC and other solid tumours. We focused on recent findings on the mechanisms that regulate PD-L2 at the genomic, transcriptional, post-transcriptional, translational, and post-translational levels, also in intercellular communication of tumour microenvironment (TME). We also discussed the prospects of using small molecular agents indirectly targeting PD-L2 in cancer therapy. These findings may provide a notable avenue in developing novel and effective PD-L2-targeted therapeutic strategies for immune combination therapy and uncovering biomarkers that improve the clinical efficacy of anti-PD-1 therapies.

Immune-Related LncRNAs to Construct a Prognosis Risk-Assessment Model for Gastric Cancer

Background: Gastric cancer is a prevalent cause of tumor death. Tumor immunotherapy aims to reshape the specific immunity to tumors in order to kill the tumor. LncRNAs play a pivotal role in regulating the tumor immune microenvironment. Herein, immune-related lncRNAs were used to establish a prognosis risk-assessment model for gastric cancer and provide personalized predictions while providing insights and targets for gastric cancer treatment to enhance patient prognosis. Methods: Gastric adenocarcinoma transcriptome and clinical data were acquired from the The Cancer Genome Atlas (TCGA) database to screen the immune-related lncRNAs. Then, LASSO COX regression was utilized to construct the prognosis risk-assessment model. Afterward, the reliability of the model was evaluated the relationship between immune infiltration, clinical characteristics, and the model was analyzed. Results: We identified 13 lncRNAs and constructed the prognosis assessment model. According to the median risk score of the training set, the patients were assigned to different risk groups. Overall survival time was shorter in the high-risk group. In the high-risk group, higher infiltration of mono-macrophages, dendritic cells, CD4+ T cells, and CD8+ T cells was observed. Moreover, the model was positively related to tumor metastasis. Conclusion: The prognosis risk-assessment model developed in this research can effectively predict the prognosis of gastric cancer patients. This tool is expected to be further applied to clinics in the future, thus providing a novel target for immunotherapy in gastric cancer patients.

PD-L2 Serves as a Potential Prognostic Biomarker That Correlates With Immune Infiltration and May Predict Therapeutic Sensitivity in Lower-Grade Gliomas

Although patients with lower-grade gliomas (LGGs; grades II and III) have a relatively favorable prognosis, patients frequently relapse and tend to progress to higher-grade gliomas, leading to treatment resistance, poor survival, and ultimately treatment failure. However, until now, thorough research has not yet been reported on the relationship between PD-L2 and immune infiltration and therapeutic sensitivity to immunotherapy and TMZ-based chemotherapy of LGGs. In this study, we found that the expression of PD-L2 is upregulated in glioma, with high PD-L2 expression predicting a worse prognosis. Univariate and multivariate Cox regression analysis both indicated that PD-L2 represented an independent prognostic factor with high accuracy in survival prediction for LGGs. A nomogram comprising of age, grade, IDH mutation, and PD-L2 was established for predicting OS. Additionally, PD-L2 was found to be remarkably correlated with immune infiltration and some anti-tumor immune functions. The degree of PD-L2 expression was also found to be strongly related to the prediction of therapeutic sensitivity to immunotherapy and TMZ-based chemotherapy. Furthermore, immunohistochemistry demonstrated that PD-L2 and the macrophage biomarker CD68 were both increased in glioma, with PD-L2 expression having a strong positive connection with CD68 expression. Taken together, PD-L2 is a prognostic biomarker for LGGs patients that may provide novel insights into glioma individualized therapeutic strategies and guide effective immunotherapy and chemotherapy.

FasL+ PD-L2+ Identifies a Novel Immunosuppressive Neutrophil Population in Human Gastric Cancer That Promotes Disease Progression

Neutrophils constitute abundant cellular components in human gastric cancer (GC) tissues, but their protumorigenic subset in pathogenesis of GC progression is unclear. Here, it is found that patients with GC show significantly higher neutrophil infiltration in tumors that is regulated by CXCL12-CXCR4 chemotaxis. These tumor-infiltrating neutrophils express high level immunosuppressive molecules FasL and PD-L2, and this FasL+ PD-L2+ neutrophil subset with a unique phenotype constitutes at least 20% of all neutrophils in advanced GC and predicts poor patient survival. Tumor induces neutrophils to express FasL and PD-L2 proteins with similar phenotype to those in GC tumors in both time-dependent and dose-dependent manners. Mechanistically, Th17 cell-derived IL-17A and tumor cell-derived G-CSF can significantly induce neutrophil FasL and PD-L2 expression via activating ERK-NF-κB and JAK-STAT3 signaling pathway, respectively. Importantly, upon over-expressing FasL and PD-L2, neutrophils acquire immunosuppressive functions on tumor-specific CD8+ T-cells and promote the growth and progression of human GC tumors in vitro and in vivo, which can be reversed by blocking FasL and PD-L2 on these neutrophils. Thus, the work identifies a novel protumorigenic FasL+ PD-L2+ neutrophil subset in GC and provides new insights for human cancer immunosuppression and anti-cancer therapies targeting these pathogenic cells.

The Positive and Negative Immunoregulatory Role of B7 Family: Promising Novel Targets in Gastric Cancer Treatment

Gastric cancer (GC), with a heterogeneous nature, is the third leading cause of death worldwide. Over the past few decades, stable reductions in the incidence of GC have been observed. However, due to the poor response to common treatments and late diagnosis, this cancer is still considered one of the lethal cancers. Emerging methods such as immunotherapy with immune checkpoint inhibitors (ICIs) have transformed the landscape of treatment for GC patients. There are presently eleven known members of the B7 family as immune checkpoint molecules: B7-1 (CD80), B7-2 (CD86), B7-H1 (PD-L1, CD274), B7-DC (PDCD1LG2, PD-L2, CD273), B7-H2 (B7RP1, ICOS-L, CD275), B7-H3 (CD276), B7-H4 (B7x, B7S1, Vtcn1), B7-H5 (VISTA, Gi24, DD1α, Dies1 SISP1), B7-H6 (NCR3LG1), B7-H7 (HHLA2), and Ig-like domain-containing receptor 2 (ILDR2). Interaction of the B7 family of immune-regulatory ligands with the corresponding receptors resulted in the induction and inhibition of T cell responses by sending co-stimulatory and co-inhibitory signals, respectively. Manipulation of the signals provided by the B7 family has significant potential in the management of GC.

HCP5 contributes to cisplatin resistance in gastric cancer through miR-128/HMGA2 axis

The long non-coding RNA HLA complex P5 (HCP5) is extensively related to cancer chemoresistance, while its function in gastric cancer (GC) has not been well elucidated yet. Here, the role and mechanism of HCP5 in regulating the chemoresistance of GC to cisplatin (DDP) was investigated. Our results revealed that HCP5 was increased in GC patients and indicated a poor prognosis. HCP5 knockdown weakens DDP resistance and reduced apoptosis of GC cells. miR-128 was decreased in GC patients and sponged by HCP5. HMGA2 was targeted by miR-128 and was increased in GC patients. HCP5 aggravated the resistance of GC cells to DDP in vitro by elevating HMGA2 expression via sponging miR-128. HCP5 silencing inhibited GC cells growth, resistance to DDP, and Ki-67 expression in vivo. In summary, HCP5 contributed to DDP resistance in GC cells through miR-128/HMGA2 axis, providing a promising therapeutic target for GC chemoresistance.

Bioinformatics and survival analysis of glia maturation factor-γ in pan-cancers

Background

Glia maturation factor-γ (GMFG) is reported to inhibit the actin nucleation through binding to the actin-related protein-2/3 complex (Arp2/3). Considering the main function of GMFG in actin remodeling, which is vital for immune response, angiogenesis, cell division and motility, GMFG is supposed to have important roles in tumor development, while up to now, only two studies described the role of GMFG in cancers. By investigating the clinical values of GMFG using The Cancer Genome Atlas (TCGA) data and the functional mechanisms of GMFG through analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments, this study was aimed to better understand the impact of GMFG in pan-cancers and to draw more attentions for the future research of GMFG.

Methods

RNA-seq and clinical data of cancer patients were collected from TCGA and analyzed by the Kaplan-Meier methods. GO and KEGG analyses were conducted using the online tools from the Database for Annotation, Visualization and Integrated Discovery (DAVID).

Results

Compared to the corresponding normal samples, GMFG was significantly upregulated in glioblastoma (GBM), kidney clear cell carcinoma (KIRC), lower grade glioma (LGG), acute myeloid leukemia (LAML), and pancreatic cancer (PAAD), testicular cancer (TGCT), but was downregulated in kidney chromophobe (KICH), lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) (P < 0.05 for all). High expression of GMFG predicted worse OS in GBM (HR = 1.5, P = 0.017), LGG (HR = 2.2, P < 0.001), LUSC (HR = 1.4, P = 0.022) and ocular melanomas (UVM) (HR = 7, P < 0.001), as well as worse DFS in LGG (HR = 1.8, P < 0.001) and prostate cancer (PRAD) (HR = 1.9, P = 0.004). In contrast, high expression of GMFG was associated with better OS in skin cutaneous melanoma (SKCM) (HR = 0.59, P < 0.001) and thymoma (THYM) (HR = 0.098, P = 0.031), as well as better DFS in bile duct cancer (CHOL) (HR = 0.2, P = 0.003). GMFG was mainly involved in the immune response, protein binding and cytokine-cytokine receptor interaction pathways, and was positively associated with multiple immunomodulators in most cancers.

Conclusion

Our study preliminarily identified that GMFG may cause different survivals for different cancers through modulating tumor progression, immune response status and tissue-specific tumor microenvironment (TME).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08163-2.

Therapeutic potential of anti-VEGF receptor 2 therapy targeting for M2-tumor-associated macrophages in colorectal cancer

BACKGROUND

Although immunotherapy with immune checkpoint inhibitors (ICIs) has become a standard therapeutic strategy in colorectal cancer (CRC) exhibiting microsatellite instability-high, limited patients benefit from this new approach. To increase the efficacy of ICIs in CRC patients, it is crucial to control the function of immunosuppressive cells in the tumor microenvironment. M2-tumor-associated macrophages (TAMs) are key immunosuppressive cells and promote tumor growth, angiogenesis, and epithelial-mesenchymal transition. In the present study, we focused on the VEGF signaling pathway in M2-TAMs to control their inhibitory function.

METHODS

We evaluated the population of M2-TAMs, the VEGF receptor 2 (VEGFR2) expression on M2-TAMs, and the correlation between HIF-1α-positive cells and VEGFR2 expression levels on M2-TAMs in CRC using the analysis of The Cancer Genome Atlas colorectal adenocarcinoma dataset (n = 592), the flow cytometry of freshly resected surgical specimens of CRC (n = 20), and the immunofluorescence staining of formalin-fixed paraffin-embedded whole tissue samples of CRC (n = 20). Furthermore, we performed a functional assay of M2 macrophages through the VEGF/VEGFR2 signaling pathway in vitro.

RESULTS

The population of M2-TAMs and their VEGFR2 expression significantly increased in the tumor compared to the normal mucosa in the CRC patients. HIF1-α-positive cells significantly correlated with the VEGFR2 expression level of M2-TAMs. M2 macrophages induced by cytokines in vitro produced TGF-β1 through the VEGF/VEGFR2 signaling pathway.

CONCLUSIONS

Our results suggest that anti-VEGFR2 therapy may have therapeutic potential to control the immune inhibitory functions of M2-TAMs in CRC, resulting in enhanced efficacy of immunotherapy with ICIs.

HCP5 Promotes Proliferation and Contributes to Cisplatin Resistance in Gastric Cancer Through miR-519d/HMGA1 Axis

Introduction

The long-non-coding RNA HCP5 (HLA complex P5) has been extensively linked to the ability of cancer cells to resist chemotherapeutic interventions. Here, we investigated the role of HCP5 in gastric cancer (GC) which to-date has been poorly characterized. Our results indicated that HCP5 expression was up-regulated in GC cells.

Methods

HCP5, miR-519d, and high mobility group A1 (HMGA1) expression levels in GC cells were measured using quantitative real-time PCR (qRT-PCR) and Western blot analysis. Drug sensitivity and apoptosis of tumor cells were assessed using cell counting kit-8, flow cytometry, and caspase activity assay. Bioinformatics and luciferase reporter assays were employed for analyzing the interactions between HCP5, miR-519d, and HMGA1.

Results

HCP5 knockdown suppressed proliferation and weakened the resistance to cisplatin (DDP) of GC cells. miR-519d was down-regulated in GC cells and sponged by HCP5. HMGA1 was directly inhibited by miR-519d and its expression was up-regulated in GC cells. HCP5 exacerbated the resistance to cisplatin of GC cells in vitro by enhancing HMGA1 expression via sponging miR-519d.

Conclusion

In summary, HCP5 promoted proliferation and contributed to DDP resistance in GC cells through miR-519d/HMGA1 axis.

PD-L1 overexpression in EBV-positive gastric cancer is caused by unique genomic or epigenomic mechanisms

Epstein-Barr virus-positive gastric cancer [EBV (+) GC] is a distinct GC subtype with unique genetic and epigenetic aberrations. Here, we examined resected GC samples and publicly available microarray data and The Cancer Genome Atlas (TCGA) database to identify the mechanism underlying overexpression of PD-L1 in EBV (+) GC. We found that high levels of PD-L1 overexpression in EBV (+) GC were caused by focal amplification of CD274. By contrast, relatively high expression of PD-L1 in tumor tissue and infiltrating immune cells correlated with CD8 lymphocyte infiltration and IFN-γ expression via IRF3 activation. Since we reported previously that PD-L1 expression is associated both with the presence of CD8 T cells in the tumor microenvironment and with IFN-γ expression in GC, we examined a database to see whether IFN-γ-associated overexpression of PD-L1 plays a significant role in EBV (+) GC. Immunohistochemical staining showed that expression of the IRF3 signature in clinical GC samples was higher in EBV (+) than in EBV (−) cases. The data presented herein reveal a unique dual mechanism underlying PD-L1 overexpression in EBV (+) GC: high focal amplification of CD274 or IFN-γ-mediated signaling via activation of IRF3.

Progress and prospects of immune checkpoint inhibitors in advanced gastric cancer

Gastric cancer, a digestive malignancy, is the sixth most frequent cancer and the second leading cause of tumor-related deaths worldwide. The emergence and advancement of immunotherapeutic agents has brought significant survival benefits for patients with gastric cancer and increasingly challenged the conventional therapy pattern involving chemotherapy and target drugs. Furthermore, these breakthroughs have paved the way for immunotherapy, especially with immune checkpoint inhibitors, which act by blocking specific signaling pathways, in particular the CTLA4 pathway and the PD-1/PD-L1 pathway. In this review, we summarize the current trials of immune checkpoint inhibitors in GC and their predictive biomarkers, and discuss their present limitations.

Combined inhibition of PD-1/PD-L1, Lag-3, and Tim-3 axes augments antitumor immunity in gastric cancer-T cell coculture models

BACKGROUND

Immunotherapy targeting PD-1 provides a limited survival benefit in patients with unresectable advanced or recurrent gastric cancer (GC). Beside PD-L1, the expression of inhibitory ligands such as CEACAM-1 and LSECtin on GC cells account for this limitation. Here we assessed their expression and immune suppressive effect in GC patients.

METHODS

Using multiplexed immunohistochemistry staining, we evaluated the distribution of different inhibitory ligands, including PD-L1, CEACAM-1, LSECtin, and MHC class II, in 365 GC patients. We analyzed their correlations and overall survival (OS) based on the expression of each inhibitory ligand and the independent prognostic factors that affect OS. Subsequently, we evaluated the additive effect of anti-PD-1 mAb or anti-PD-L1 mAb with/without anti-Lag-3 mAb with/without anti-Tim-3 mAb in cytotoxic assay using tumor-antigen specific CTL clones against GC cell lines.

RESULTS

Co-expression of the inhibitory ligands for PD-1, Tim-3, and Lag-3 was observed in the largest proportion (34.7%). CEACAM-1, LSECtin, and MHC class II expression showed significant correlation with PD-L1 expression and OS. Multivariable analysis demonstrated that CEACAM-1 low is an independent prognostic factor. Furthermore, combining dual and triple ICIs yielded additive effect on cytotoxicity of CTL clones against each immune inhibitory ligand positive GC cell lines.

CONCLUSIONS

Our findings suggested that the expression of inhibitory ligands for Tim-3 and Lag-3 on GC cells serve as potential biomarkers to predict the response to anti-PD-1 therapy and the combinatorial immunotherapy with ICIs targeting for PD-1, Tim-3, and Lag-3 has a therapeutic potential for GC patients.

Current status of immune checkpoint inhibitors for gastric cancer

Recent breakthrough results from immune checkpoint inhibitors (ICI) have paved the way to a new era of cancer immunotherapy. In particular, inhibition of programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) axis with ICI including nivolumab and pembrolizumab has been emerging as a novel treatment strategy for advanced gastric cancers (GC). In a meta-analysis for anti-PD-1/PD-L1 therapy in GC, the objective response rate was 12.0% and the disease control ratio was 34.7%. The ICI treatment in GC provided modest survival benefit and especially, anti-PD-1 treatment could improve the 12-month and 18-month overall survival rate and prolonged the duration of the response. Moreover, it is likely that anti-PD-1/PD-L1 therapy is more effective in subgroups with microsatellite instability-high, Epstein-Barr virus-positive or high mutation burden in advanced GC. The next steps for developing ICI in GC are mainly two challenges as follows. First is the identification of accurate biomarkers that can predict the response to ICI. The second challenge is the clinical development of combinatorial approaches to maximize the efficacy of ICI. In this review, recent advances in ICI for GC are discussed from a viewpoint of translational aspect including biomarkers and tumor microenvironment, and from a viewpoint of clinical aspects including combination therapies.

STAT3 Pathway in Gastric Cancer: Signaling, Therapeutic Targeting and Future Prospects

Molecular signaling pathways play a significant role in the regulation of biological mechanisms, and their abnormal expression can provide the conditions for cancer development. The signal transducer and activator of transcription 3 (STAT3) is a key member of the STAT proteins and its oncogene role in cancer has been shown. STAT3 is able to promote the proliferation and invasion of cancer cells and induces chemoresistance. Different downstream targets of STAT3 have been identified in cancer and it has also been shown that microRNA (miR), long non-coding RNA (lncRNA) and other molecular pathways are able to function as upstream mediators of STAT3 in cancer. In the present review, we focus on the role and regulation of STAT3 in gastric cancer (GC). miRs and lncRNAs are considered as potential upstream mediators of STAT3 and they are able to affect STAT3 expression in exerting their oncogene or onco-suppressor role in GC cells. Anti-tumor compounds suppress the STAT3 signaling pathway to restrict the proliferation and malignant behavior of GC cells. Other molecular pathways, such as sirtuin, stathmin and so on, can act as upstream mediators of STAT3 in GC. Notably, the components of the tumor microenvironment that are capable of targeting STAT3 in GC, such as fibroblasts and macrophages, are discussed in this review. Finally, we demonstrate that STAT3 can target oncogene factors to enhance the proliferation and metastasis of GC cells.

Exosomal PD-L1: New Insights Into Tumor Immune Escape Mechanisms and Therapeutic Strategies

As a classical immune checkpoint molecule, PD-L1 on the surface of tumor cells plays a pivotal role in tumor immunosuppression, primarily by inhibiting the antitumor activities of T cells by binding to its receptor PD-1. PD-1/PD-L1 inhibitors have demonstrated unprecedented promise in treating various human cancers with impressive efficacy. However, a significant portion of cancer patients remains less responsive. Therefore, a better understanding of PD-L1-mediated immune escape is imperative. PD-L1 can be expressed on the surface of tumor cells, but it is also found to exist in extracellular forms, such as on exosomes. Recent studies have revealed the importance of exosomal PD-L1 (ExoPD-L1). As an alternative to membrane-bound PD-L1, ExoPD-L1 produced by tumor cells also plays an important regulatory role in the antitumor immune response. We review the recent remarkable findings on the biological functions of ExoPD-L1, including the inhibition of lymphocyte activities, migration to PD-L1-negative tumor cells and immune cells, induction of both local and systemic immunosuppression, and promotion of tumor growth. We also discuss the potential implications of ExoPD-L1 as a predictor for disease progression and treatment response, sensitive methods for detection of circulating ExoPD-L1, and the novel therapeutic strategies combining the inhibition of exosome biogenesis with PD-L1 blockade in the clinic.