Immunotherapy for Gastric Cancer: A Focus on Immune Checkpoints

TIM3+ cells in gastric cancer: clinical correlates and association with immune context

BACKGROUND

T cell immunoglobulin and mucin domain-containing protein 3 (TIM3) is a crucial immune checkpoint and is considered as an emerging target for cancer treatment. However, the clinical significance and immune-related role of TIM3⁺ cells in gastric cancer remain unknown. This study aimed to investigate the clinical significance of tumour-infiltrating TIM3⁺ cells and their association with immune contexture in gastric cancer.

METHODS

This study enrolled three cohorts, including 436 tumour tissue microarray specimens and 58 fresh tumour tissues of gastric cancer patients from Zhongshan Hospital, and 330 transcriptional data from The Cancer Genome Atlas. TIM3⁺ cells and their association with CD8⁺ T cells were evaluated by immunohistochemistry and flow cytometry analyses. Kaplan-Meier curves, Cox model and interaction test were performed to assess clinical outcomes.

RESULTS

Tumour-infiltrating TIM3⁺ cells' high subgroups experienced poorer overall survival and disease-free survival and predicted inferior therapeutic responsiveness to fluorouracil-based adjuvant chemotherapy. TIM3 indicated CD8⁺ T cell dysfunction, which impeded chemotherapeutic responsiveness. Besides, HAVCR2 messenger RNA expression was associated with specific molecular characteristics.

CONCLUSIONS

The abundance of tumour-infiltrating TIM3⁺ cells could identify an immunoevasive subtype gastric cancer with CD8⁺ T cell dysfunction, suggesting that TIM3 might serve as a promising target for immunotherapy in gastric cancer.

Gastrin Vaccine Alone and in Combination With an Immune Checkpoint Antibody Inhibits Growth and Metastases of Gastric Cancer

Gastric cancer is a leading cause of cancer-related deaths worldwide. Recently, clinical studies have demonstrated that many of those with advanced gastric cancer are responsive to immune checkpoint antibody therapy, although the median survival even with these new agents is less than 12 months for advanced disease. The gastrointestinal peptide gastrin has been shown to stimulate growth of gastric cancer in a paracrine and autocrine fashion through the cholecystokinin-B receptor (CCK-BR), a receptor that is expressed in at least 56.6% of human gastric cancers. In the current investigation, we studied the role of the gastrin-CCK-BR pathway in vitro and in vivo as well as the expression of the CCK-BR in a human gastric cancer tissue array. CCK-BR and PD-L1 receptor expression and gastrin peptide was found in two murine gastric cancer cells (NCC-S1 and YTN-16) by qRT-PCR and immunocytochemistry. Treatment of NCC-S1 cells with gastrin resulted in increased growth. In vivo, the effects of a cancer vaccine that targets gastrin peptide (polyclonal antibody stimulator-PAS) alone or in combination with a Programed Death-1 antibody (PD-1 Ab) was evaluated in immune competent mice (N = 40) bearing YTN-16 gastric tumors. Mice were treated with PBS, PD-1 Ab (50 µg), PAS (250 µg), or the combination of PD-1 Ab with PAS. Tumor growth was significantly slower than controls in PAS-treated mice, and tumor growth was decreased even more in combination-treated mice. There were no metastases in any of the mice treated with PAS either alone or in combination with PD-1 Ab. Tumor proliferation by the Ki67 staining was significantly decreased in mice treated with PAS monotherapy or the combination therapy. PAS monotherapy or combined with PD-1 Ab increased tumor CD8+ T-lymphocytes and decreased the number of immunosuppressive M2-polarized tumor-associated macrophages. CCK-BR expression was identified in samples from a human tissue array by immunohistochemistry confirming the clinical relevance of this study. These results confirm the significance of the gastrin-CCK-BR signaling pathway in gastric cancer and suggest that the addition of a gastrin vaccine, PAS, to therapy with an immune checkpoint antibody may decrease growth and metastases of gastric cancer by altering the tumor microenvironment.

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.

Chemoradiation induces upregulation of immunogenic cell death-related molecules together with increased expression of PD-L1 and galectin-9 in gastric cancer

Surgery alone or combined with chemo- and/or radiation therapy remains the primary treatment for gastric cancer (GC) to date and immunotherapeutic tools such as monoclonal antibodies are only slowly being implemented. This is partly due to the fact that the immune microenvironment in GC during chemoradiation and other treatment modalities is still poorly understood. 7 gastric cancer (GC) cell lines were tested for their response to chemoradiation using 5-FU in combination with X-ray irradiation. We conducted flow cytometric analysis to determine the cells’ ability to undergo immunogenic cell death (ICD) and their expression of the two immunosuppressive proteins programmed death-ligand 1 (PD-L1) and galectin-9 (Gal-9). We evaluated the overall immunogenicity of two cell lines (MKN7, MKN74) in co-culture experiments with human monocyte-derived dendritic cells (Mo-DCs). Chemoradiation induces distinct responses in different GC cell lines. We observe ICD in vitro in all tested GC cell lines in the form of calreticulin (CRT) translocation to the plasma membrane. As a resistance mechanism, these cells also upregulated Gal-9 and PD-L1. Mo-DC maturation experiments showed that GCs provoked the maturation of Mo-DCs after chemoradiation in vitro. The addition of α-PD-L1 blocking antibody further enhanced the immunogenicity of these cells while improving DC viability. Blocking Tim-3, as the main receptor for Gal-9, had no such effect. Our findings suggest that the benefits of chemoradiation can substantially depend on tumor subtype and these benefits can be offset by induced immune evasion in GC. Combination treatment using checkpoint inhibitors could potentially lead to enhanced immune responses and yield better patient outcomes.

KMT2D promotes proliferation of gastric cancer cells: evidence from ctDNA sequencing

BACKGROUND

ctDNA sequencing could be used for early cancer screening, prognosis prediction, and medication guidance. However, data of its application in gastric cancer are still lacking. In this study, using ctDNA sequencing, we aimed to screen the mutant genes closely associated with gastric cancer and to explore the impact of these genes on gastric cancer development.

METHODS

ctDNA for high-throughput sequencing was obtained from gastric cancer patients, and the high-frequency mutant gene KMT2D was identified. Immunohistochemical examination was conducted to assess the expression of KMT2D in gastric cancer tissues. KMT2D knockdown was performed to establish the stably transfected gastric cancer cells. Then, CCK8, plate clone formation assay, and Transwell assay were conducted, and a subcutaneous tumor-bearing model was induced in nude mice to investigate the changes in cell proliferation and invasion capability. Transcriptome sequencing was also performed to investigate the differences in cellular gene expression.

RESULTS

Detection of ctDNA found 113 gastric cancer-related mutations, 11 of which are the top 20 high-frequency mutations of gastric cancer recorded by COSMIC (Catalogue of Somatic Mutations in Cancer, COSMIC). They are TP53, ARID1A, CDH1, PIK3CA, KMT2C, KMT2D, APC, SPEN, CTNNB1, SETBP1, and KMT2A. The gene closely related to the clinical characteristics of the patient is KMT2D. The high-frequency mutant gene KMT2D was identified in gastric cancer tissues. The positive rate of KMT2D expression in cancer tissues was 74.3%, which was higher than that in para-carcinoma tissues (56.8%). The knockdown of KMT2D inhibited the proliferation, invasion, and tumor formation capacity of the gastric cancer cells, causing differences in the gene expression profiles, and the expression of different functional gene clusters was up- or downregulated.

CONCLUSION

The findings of this study revealed that KMT2D could be an oncogene capable of promoting gastric cancer proliferation.

Prediction of overall survival and response to immune checkpoint inhibitors: An immune-related signature for gastric cancer

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As is known to us, this is the first immune-gene-related signature of gastric cancer which was validated in various ways.

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This signature was linked to the mutation status, and we found the difference of mutation between two risk groups.

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The signature has similar function with TMB.

Gastric cancer (GC) is common in East Asia and South and Central America. Most GC patients miss the opportunities for surgery. Despite their therapeutic potential, immune checkpoint inhibitors (ICIs) only work in part of patients with GC. Thus, this study was aimed at constructing a signature for diagnosis, prognosis, and prediction of response to ICIs. A multivariate analysis showed that the 8-immune-related-gene (IRG) signature was an independent prognostic factor of overall survival among GC patients. In the high-risk group of 8IRG signature risk score, the fractions of CD4 T cells, macrophage M2 and monocyte, which is associated with the progression of cancers, were higher. The low-risk group had a higher immunophenoscore, which meant a better response to ICIs.

Phase III Trial of Avelumab Maintenance After First-Line Induction Chemotherapy Versus Continuation of Chemotherapy in Patients With Gastric Cancers: Results From JAVELIN Gastric 100

PURPOSE

The role of maintenance therapy for gastric (GC) or gastroesophageal junction cancer (GEJC) is unclear. We investigated avelumab (anti-programmed death ligand-1 [PD-L1]) maintenance after first-line induction chemotherapy for GC/GEJC.

PATIENTS AND METHODS

JAVELIN Gastric 100 was a global, open-label, phase III trial. Eligible patients had untreated, unresectable, human epidermal growth factor receptor 2-negative, locally advanced or metastatic GC or GEJC. Patients without progressive disease after 12 weeks of first-line chemotherapy with oxaliplatin plus a fluoropyrimidine were randomly assigned 1:1 to avelumab 10 mg/kg every 2 weeks or continued chemotherapy, stratified by region (Asia v non-Asia). The primary end point was overall survival (OS) after induction chemotherapy in all randomly assigned patients or the PD-L1-positive randomly assigned population (≥ 1% of tumor cells; 73-10 assay).

RESULTS

A total of 805 patients received induction; 499 were randomly assigned to avelumab (n = 249) or continued chemotherapy (n = 250). Median OS was 10.4 months (95% CI, 9.1 to 12.0 months) versus 10.9 months (95% CI, 9.6 to 12.4 months) and 24-month OS rate was 22.1% versus 15.5% with avelumab versus chemotherapy, respectively (hazard ratio [HR], 0.91; 95% CI, 0.74 to 1.11; P = .1779). In the PD-L1-positive population (n = 54), the HR for OS was 1.13 (95% CI, 0.57 to 2.23; P = .6352). In an exploratory analysis of the PD-L1-positive population, defined as combined positive score ≥ 1 (22C3 assay; n = 137), median OS was 14.9 months (95% CI, 8.7 to 17.3 months) with avelumab versus 11.6 months (95% CI, 8.4 to 12.6 months) with chemotherapy (unstratified HR, 0.72; 95% CI, 0.49 to 1.05). With avelumab and chemotherapy, treatment-related adverse events (TRAEs) occurred in 149 (61.3%) and 184 (77.3%) patients, including grade ≥ 3 TRAEs in 31 (12.8%) and 78 (32.8%) patients, respectively.

CONCLUSION

JAVELIN Gastric 100 did not demonstrate superior OS with avelumab maintenance versus continued chemotherapy in patients with advanced GC or GEJC overall or in a prespecified PD-L1-positive population.

Immunotherapy of gastric cancer: Past, future perspective and challenges

Gastric cancer is considered as the third leading cause of deaths and the fifth most common cancers worldwide. Common treatment approaches include chemotherapy, radiation, gastric resection and targeted therapies. The emergence of gastric cancer immunotherapy has already shown some promising results and have altered the therapeutic procedures. Now, different combination therapies as well as novel immunotherapies targeting new molecules have been proposed. Despite ongoing investigations on the therapeutic options and significant advancements in this regard, the disease is poorly prognosed. In fact, limited therapeutic options and delayed diagnosis lead to the progression, dissemination and metastasis of the disease. Current immunotherapies are mostly based on cytotoxic immunocytes, monoclonal antibodies and gene transferred vaccines. The use of Immune checkpoint inhibitors (ICIs) have grown rapidly. In this review, we aimed to explore perspective and progression of different approaches of immunotherapy in the treatment of GC and the clinical outcomes reported so far. We also summarized the tumor immunosurveillance and tumor immunoescape.

Silencing lncRNA XIST exhibits antiproliferative and proapoptotic effects on gastric cancer cells by up-regulating microRNA-132 and down-regulating PXN

The present study aims to elucidate the potential therapeutic role of lncRNA XIST in gastric cancer through regulation of microRNA-132 (miR-132) and paxillin (PXN) expression. The study employed 65 gastric cancer tissue specimens and SGC7901 cell lines. Our results demonstrated that expression of lncRNA XIST and PXN was significantly elevated while the expression of miR-132 was significantly reduced in gastric cancer tissues. Dual-luciferase, RNA pull-down and RIP assays demonstrated that lncRNA XIST up-regulated the PXN expression by competitively binding to miR-132. Moreover, silencing of lncRNA XIST and up-regulation of miR-132 could suppress tumor formation ability, cell proliferation and migration, but enhanced apoptosis in gastric cancer. However, the overexpression of PXN achieved the opposite tumor-promotive effect. Meanwhile, rescue experiments suggested that silencing of lncRNA XIST could reverse the tumor-promotive effect exerted by either miR-132 inhibitor or PXN. Taken together, the present study demonstrates lncRNA XIST as a novel oncogenic lncRNA in gastric cancer, highlighting its therapeutic role in this disease.

LncRNA NUTM2A-AS1 positively modulates TET1 and HIF-1A to enhance gastric cancer tumorigenesis and drug resistance by sponging miR-376a

Long noncoding RNA NUTM2A‐AS1 has been shown to be dysregulated in non‐small cell lung carcinoma. To date, it is unclear whether NUTM2A‐AS1 plays a role in gastric cancer progression. The purpose of this study is to elucidate the molecular mechanism of the role of NUTM2A‐AS1 in gastric cancer. mRNA and protein levels were measured by RT‐qPCR and western blot methods. Invasion ability was examined by transwell assay. Cell viability was determined by MTT assay. Dual‐luciferase assay, RNA pull down, and RNA immunoprecipitation were used to confirm direct binding of between miR‐376a and NUTM2A‐AS1 or TET1. Xenografting tumor assay and TCGA analysis showed the contributory role of NUTM2A‐AS1 in vivo and human clinical setting. Our results suggested that NUTM2A‐AS1 promoted cell viability, invasion, and drug resistance of gastric cancer cells, which was largely rescued by miR‐376a. More interestingly, TET1 and HIF‐1A were negatively regulated by miR‐376a. TET1 could interact with HIF‐1A to modulate PD‐L1. Finally, we revealed that PD‐L1 was key to NUTM2A‐AS1‐ and miR‐376a‐mediated tumorigenesis and drug resistance. In summary, our conclusions facilitate us understand the underlying mechanism and develop novel treatment strategy for gastric cancer.

An update on colorectal cancer microenvironment, epigenetic and immunotherapy

Colorectal cancer (CRC) is considered as the second most common cancer worldwide. For the past few years, the role of immunotherapy has been extensively studied and it has been demonstrated that its related approaches, such as programmed death-1 (PD-1) inhibitors, are promising. In addition to identifying molecular characteristics of tumor cells, recent studies are mainly focused on the profiling of tumor microenvironment. Dissecting immune status of a tumor is interesting, since development of a tumor is associated with deficiencies relate to immune defense, immune surveillance and immune hemostasis. In this review, we discuss main obstacles of immunotherapy including immunosuppressive niche and low immunogenicity of CRC as well as reviewing current achievements in immunotherapy.

Research progress of PD-1/PD-L1 immunotherapy in gastrointestinal tumors

Gastrointestinal tumor (GIT) is a common malignant tumor of the digestive system, which seriously threatens people's health and life. With the deepening of the study on the mechanism of tumor immune escape, programmed death receptor ligand 1 (PD-L1) has been proved to interact with the tumor microenvironment to mediate tumor immune escape. PD-L1 inhibitor is a hot spot in tumor immunotherapy in recent years, which can restore the activity of T cells, enhance the body's ability of immune response, and ultimately enable the immune system to effectively identify and kill gastric cancer cells, then achieve long-term tumor remission in patients with GITs. At present, variety of PD-L1 inhibitors such as pembrolizumab, nivolumab and avelumab have been approved for the market, and they have achieved good results in clinical studies on the GIT. This paper reviews the progress of PD-1/PD-L1 immunotherapy in GITs which include gastric cancer, colon cancer and rectal cancer.

Influence of microbiota on immunity and immunotherapy for gastric and esophageal cancers

Gastric and esophageal cancers are multifactorial and multistage-involved malignancy. While the impact of gut microbiota on overall human health and diseases has been well documented, the influence of gastric and esophageal microbiota on gastric and esophageal cancers remains unclear. This review will discuss the reported alteration in the composition of gastric and esophageal microbiota in normal and disease conditions, and the potential role of dysbiosis in carcinogenesis and tumorigenesis. This review will also discuss how dysbiosis stimulates local and systemic immunity, which may impact on the immunotherapy for cancer.

Current Molecular Targeted Agents for Advanced Gastric Cancer

Gastric cancer is the third leading cause of malignant tumor-related mortality worldwide. Traditional cytotoxic agents prolong the overall survival and progression-free survival of patients with advanced gastric cancer (AGC) compared to that with best supportive care. Due to the occurrence of serious adverse drug reactions that result in discontinued treatment, the survival benefit in AGC remains unsatisfactory. Systemic chemotherapy regimens have changed greatly, especially since the introduction of trastuzumab. Nevertheless, HER2 positivity is present in only approximately 20% of tumors. Due to the genetic heterogeneity and complexity of patients, there are many studies in progress that are exploring novel targeted drugs as an alternative to chemotherapy or adjuvant treatment in early-stage, progressive, and advanced gastric cancer. On the basis of the differences in gene expression profiles among patients, searching for specific and sensitive predictive biomarkers is important for identifying patients who will benefit from a specific targeted drug. With the development of targeted therapies and available chemotherapeutic drugs, there is no doubt that, over time, more patients will achieve better survival outcomes. Recently, immune checkpoint blockade has been well developed as a promising anticancer strategy. This review outlines the currently available information on clinically tested molecular targeted drugs and immune checkpoint inhibitors for AGC to provide support for decision-making in clinical practice.

Third- and later-line treatment in advanced or metastatic gastric cancer: a systematic review and meta-analysis

Aim: We performed a systematic review and meta-analysis to investigate the efficacy and safety of third-line (TLT) and salvage treatment (ST) in advanced or metastatic gastric cancer. Materials & methods: Eligible studies included randomized clinical trials assessing TLT and ST versus placebo or best supportive care. Outcomes of interest included: overall survival, objective response rate and disease control rate in TLT; progression-free survival in ST; grade 3-4 adverse events in ST. Results: The use of TLT and ST was superior to placebo or best supportive care in terms of prolonging overall survival and progression-free survival. Hematological toxicities were more frequent in ST. Conclusion: TLT and ST are considerable and tolerable treatment options for patients with advanced or metastatic gastric cancer. Given the substantial heterogeneities affecting the efficacy analyses, these results have to be interpreted cautiously.

Avelumab (anti-PD-L1) as first-line switch-maintenance or second-line therapy in patients with advanced gastric or gastroesophageal junction cancer: phase 1b results from the JAVELIN Solid Tumor trial

Background

We evaluated the antitumor activity and safety of avelumab, a human anti–PD-L1 IgG1 antibody, as first-line switch-maintenance (1 L-mn) or second-line (2 L) treatment in patients with advanced gastric/gastroesophageal cancer (GC/GEJC) previously treated with chemotherapy.

Methods

In a phase 1b expansion cohort, patients without (1 L-mn) or with (2 L) disease progression following first-line chemotherapy for advanced GC/GEJC received avelumab 10 mg/kg intravenously every 2 weeks. Endpoints included best overall response, progression-free survival (PFS), overall survival (OS), and safety.

Results

Overall, 150 patients were enrolled (1 L-mn, n = 90; 2 L, n = 60) and median follow-up in the 1 L-mn and 2 L subgroups was 36.0 and 33.7 months, respectively. The confirmed objective response rate was 6.7% in both subgroups (95% CI, 2.5–13.9% and 1.8–16.2%, respectively), including complete responses in 2.2% of the 1 L-mn subgroup (n = 2). In the 1 L-mn and 2 L subgroups, median duration of response was 21.4 months (95% CI, 4.0–not estimable) and 3.5 months (95% CI, 2.8–8.3) and disease control rates were 56.7 and 28.3%, respectively. Median PFS in the 1 L-mn and 2 L subgroups was 2.8 months (95% CI, 2.3–4.1) and 1.4 months (95% CI, 1.3–1.5), with 6-month PFS rates of 23.0% (95% CI, 14.7–32.4%) and 7.9% (95% CI, 2.6–17.2%), and median OS was 11.1 months (95% CI, 8.9–13.7) and 6.6 months (95% CI, 5.4–9.4), respectively. In the 1 L-mn subgroup, median OS measured from start of 1 L chemotherapy was 18.7 months (95% CI, 15.4–20.6). Across both subgroups, 20.7% had an infusion-related reaction of any grade. Other common treatment-related adverse events (TRAEs) of any grade included fatigue (10.0%) and nausea (6.7%). Treatment-related serious adverse events occurred in 4.0% of patients. Overall, 8.7% had a grade ≥3 TRAE, including 1 treatment-related death.

Conclusion

Avelumab showed clinical activity and an acceptable safety profile in patients with GC/GEJC.

Trial registration

ClinicalTrials.govNCT01772004; registered 21 January 2013.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0508-1) contains supplementary material, which is available to authorized users.

Maintenance avelumab versus continuation of first-line chemotherapy in gastric cancer: JAVELIN Gastric 100 study design

Avelumab is a human anti-PD-L1 IgG1 monoclonal antibody that has shown antitumor activity in early phase studies in advanced/metastatic gastric/gastroesophageal junction cancer, including as first-line maintenance therapy. Here, we describe the design of JAVELIN Gastric 100 (NCT02625610), an open-label, Phase III trial. A total of 499 patients with locally advanced/metastatic HER2- gastric/gastroesophageal junction cancer adenocarcinoma, who had achieved at least stable disease following 12 weeks of first-line oxaliplatin/fluoropyrimidine chemotherapy, have been randomized 1:1 to receive avelumab maintenance therapy or continue chemotherapy. The primary objective is to demonstrate superior overall survival in all randomized patients or in the PD-L1+ population. Secondary objectives are to demonstrate superiority for progression-free survival and objective response rate, compare quality of life measures, and determine safety.

MiR-6991-3p is identified as a novel suppressor in the expansion and activation of myeloid-derived suppressor cells in hepatoma-bearing mice

Objective

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of cells derived from bone marrow, which has a significant ability in inhibition of immune cell response. In this study, the role of miR-6991-3p in regulating function of MDSCs was investigated.

Methods

MDSCs were isolated from different tissues of the control and hepatoma-bearing mice, and then expression of miR-6991-3p was detected with qPCR. Then, the miR-6991-3p mimic and inhibitor were respectively transfected into MDSCs, and behaviors of MDSCs were evaluated, including expansion, apoptosis, and production of inflammatory factors. Furthermore, we explored the underlying mechanism from which miR-6991-3p regulated MDSC functions.

Results

Expression miR-6991-3p was markedly decreased in the MDSCs derived from spleen and further decreased in the MDSCs derived from the tumor tissue. MiR-6991-3p mimic transfection suppressed expansion and promoted apoptosis of MDSCs, accompanied by a significant decrease in the production of IL-6 and GM-CSF that are identified as stimulators in MDSC expansion. In contrast, miR-6991-3p inhibitor transfection displayed the opposite effect. miR-6991-3p bound with and negatively regulated expression of LGALS9, a newly identified immune checkpoint gene and activator of STAT3, suppressing production of multiple factors that were customarily used to characterize the activation of MDSCs. MiR-6991-3p-accommodated MDSCs displayed less suppression on T cells, while miR-6991-3p inhibitor enhanced the suppression of MDSCs on T cells.

Conclusion

MiR-6991-3p is identified as a novel suppressor in the expansion and activation of myeloid-derived suppressor cells, which may be regarded as a promising target for modulating the function of MDSCs.

Outlook: Immunotherapy in Gastrointestinal Carcinoma - Innovative Strategies

Immune checkpoint inhibitors are emerging as a therapeutic approach for patients with advanced or metastatic gastrointestinal malignancies following the recent Food and Drug Administration and Asian approvals for colorectal, gastric, and hepatocellular carcinoma. As discussed in earlier articles, phase I-II trials demonstrate quite positive clinical activity, particularly in patients with immunogenic cancer subtypes. This outreach paper discusses some of the next innovative immunotherapy strategies under development. Here, tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells are increasingly coming into focus as new targets. Besides the well described use of checkpoint inhibitors, blockade of 'Wnt' or Csf1R signaling pathways as well as combinatorial treatment strategies offer promising examples for overcoming immune silencing within the resistant tumor microenvironment.

PD-L1 is an independent prognostic predictor in gastric cancer of Western patients

Targeting the PD-1/PD-L1 immune checkpoint signaling is a novel promising treatment strategy in several tumor entities, and it is suggested that PD-L1/PD-1 expression is predictive for a PD-1/PD-L1 checkpoint inhibitor treatment response. We investigated the expression of PD-L1 and PD-1 by immunohistochemistry in a large and well characterized gastric cancer (GC) cohort of Caucasian patients, consisting of 465 GC samples and 15 corresponding liver metastases. Staining results were correlated with clinico-pathological characteristics and survival. PD-L1 expression was found in tumor cells of 140 GCs (30.1%) and 9 liver metastases (60%) respectively in immune cells of 411 GCs (88.4%) and 11 liver metastases (73.3%). PD-1 was expressed in tumor infiltrating lymphocytes in 250 GCs (53.8%) and in 11 liver metastases (73.3%). PD-L1 expression was significantly more prevalent in men, GCs of the proximal stomach, unclassified, papillary, Her2/neu-positive, Epstein-Barr-virus-positive, microsatellite instable, and PIK3CA-mutated GCs. A high PD-L1/PD-1 expression was associated with a significantly better patient outcome, and PD-L1 turned out to be an independent survival prognosticator. The correlation of PD-L1/PD-1 expression with distinct clinico-pathological patient characteristics may serve as a surrogate marker of PD-L1-positive GCs and may direct the use of immune checkpoint treatment strategies.

Medical management of gastric cancer: a 2017 update

Gastric cancer remains a considerable health burden throughout the world. The Cancer Genome Atlas (TCGA) analysis has recently unveiled 4 genotypes of gastric cancer with data not ready to change treatment strategy yet. A multimodality approach to therapy is the cornerstone of screening, diagnosing, staging, treating and supporting patients with gastric cancer. The evidence-based approach to localized gastric cancer (>cT1b) is to use an either preoperative or postoperative strategy to maximize the benefit of surgery. The focus of future research is to optimize chemotherapy regimens, determine the role of radiation therapy and investigate the effect of treatment timing. In metastatic gastric cancer, biologic therapies have been introduced targeting markers shown to be prognostic. The results of ongoing randomized controlled phase 3 trials using targeted and immunotherapy agents, either in combination or alone, have the potential to alter the current treatment landscape of advanced gastric cancer.

PD-1 and PD-L1 co-expression predicts favorable prognosis in gastric cancer

While the prognosis of gastric cancer (GC) remains poor, PD-1 and PD-L1/L2 are promising prognostic biomarkers. We evaluated PD-1 and PD-L1/L2 expression in tumor cells (TCs) and tumor-infiltrating immune cells (TIICs). We determined the Helicobacter pylori (Hp) and Epstein-Barr virus (EBV) infection status in a GC cohort (n=340), then analyzed the relationship between the expression of PD-1, PD-L1/L2 and GC prognosis. We found that PD-1, PD-L1, and PD-L2 mRNA levels were up-regulated in GC tissues, and were positively correlated with one another (P=0.043, P=0.008 and P=0.035). PD-1 protein expression in TIICs was observed in 22.6% of GC patients. The PD-L1 and PD-L2 positivity rates were 40.3% and 53.8% in TCs, respectively, and 60.0% and 60.9% in TIICs, respectively. PD-L1 was up-regulated in EBV-infected GC patients in both TCs (P=0.009) and TIICs (P=0.003). Hp status was not associated with PD-1 or PD-L1/PD-L2 expression. In TIICs, PD-L1 expression was independently associated with better GC prognosis (HR=0.72, 95%CI: 0.53-0.99). Co-expression of PD-1 and PD-L1, but not PD-L2, was a favorable prognostic marker that indicated a dose effect on the mortality risk of GC patients (P-value for trend=0.005). Comprehensive evaluation of PD-1 and PD-L1 in TCs and TIICs could help predict the prognosis of gastric cancers, as well as reveal patients who might benefit from targeted treatment.

Association between PD-L1 Expression on Tumour-Infiltrating Lymphocytes and Overall Survival in Patients with Gastric Cancer

Purpose Targeting of the PD-1/PD-L1 signalling pathway is a promising treatment strategy in several cancers. The aim of this study was to assess the expression of PD-L1 on tumour cells and tumour-infiltrating lymphocytes (TILs) in gastric cancer (GC) and its prognostic impact.

Materials and Methods A total of 240 patients who were diagnosed with GC at Sun Yat-sen University Cancer Centre (SYSUCC) from May 2008 to December 2013 were included in this study. PD-L1 expression was detected by immunohistochemistry (IHC) in all GC tumour specimens. The Cox proportional hazard regression model was used to assess the association between PD-L1 expression and overall survival (OS).

Results The positive rates of PD-L1 expression on tumour cells and TILs were 74.8% and 65.8%, respectively. Patients with poor tumour differentiation had higher positive rates of PD-L1 expression on tumour cells (p=0.023). There was no significant association between PD-L1 expression on tumour cells and other clinicopathological data. In TILs, PD-L1 expression was significantly higher in patients who underwent surgery (p=0.031) and were in the late stage (p=0.021) than those without surgery and in the early stage. Patients with positive PD-L1 expression on TILs had a significantly shorter five-year OS than those with negative PD-L1 expression (14.2 vs 18.3; p=0.001); therefore, PD-L1 expression on TILs is an independent prognostic factor. However, PD-L1 expression on tumour cells is not associated with OS (p=0.945).

Conclusion Our findings suggest that PD-L1 expression on TILs may be a predictive factor for immunotherapy of PD-1/PD-L1 pathway inhibitors.

Predictive and prognostic biomarkers in personalized gastrointestinal cancer treatment

Biomarkers play an important role in the detection and management of cancer patients. In gastrointestinal cancer, there is increasing interest in their development and validation according to specific tumor type. Prognostic biomarkers enable identification of patients with a more aggressive tumor evolution, while predictive biomarkers permit the identification of patients with a higher probability of responding or not to a specific treatment. Several biomarkers are currently widely employed in gastrointestinal cancers. These include rat sarcoma-2 virus (RAS) which is used to identify colorectal cancer (CRC) patients who will not respond to anti-epidermal growth factor receptor (EGFR) agents, while in gastric cancer, anti-human epidermal growth factor receptor 2 (HER2) therapy has been shown to only be active in HER2-positive patients. In pancreatic cancer, BRCA is a tool used to differentiate patients who are likely to respond to platinum-based combination therapies and to benefit from poly (ADP-ribose) polymerase (PARP) inhibitors. This review provides an update of the main biomarkers currently used in colorectal, gastric and pancreatic cancers, and reviews those that are being developed.

The prognostic value and pathobiological significance of Glasgow microenvironment score in gastric cancer

PURPOSE

To evaluate the prognostic value and pathobiological significance of Glasgow microenvironment score (GMS), a parameter based on tumor stroma percentage and inflammatory cell infiltration, in gastric cancer.

METHODS

A total of 225 cases of gastric cancer were histologically reviewed, and GMS was evaluated for each case. The association between GMS and patients' survival was investigated. Then the relationship between GMS and mismatch repair (MMR) status, Epstein-Barr virus (EBV) infection were determined using immunohistochemistry (IHC) and in situ hybridization, and the expression of PD1/PD-L1 was examined. Furthermore, the amount of cancer-associated fibroblasts (CAFs), the content and maturity of collagen components were detected using IHC, Picrosirius Red staining and second harmonic generation imaging.

RESULTS

GMS was significantly associated with clinical outcomes of gastric cancer, and multivariate analysis indicated that GMS was an independent factor (HR 1.725, P = 0.002). Low GMS was a manifestation of better prognosis and inflammatory tumor microenvironment, which was related to MMR deficiency (P = 0.042) and EBV infection (P = 0.032), and within this microenvironment, expression of PD-L1 in carcinoma cells (P = 0.030) or in inflammatory cells (P = 0.029) was significantly higher. In contrast, high GMS linked to a poorer survival and desmoplastic stroma, in which there existed markedly increased CAFs and collagen deposition.

CONCLUSION

GMS can serve as a useful prognostic factor for gastric cancer, and according to GMS, the tumor microenvironment in this cancer type may be partially classified as inflammatory or desmoplastic microenvironment that possesses different pathobiological features.

Immunotherapy for gastric cancers: emerging role and future perspectives

INTRODUCTION

The broad use of immunotherapy is revolutionizing the treatment paradigms of many solid tumors. Although chemotherapy remains the treatment backbone for advanced gastric cancer, improvements in its molecular characterization and progresses in understanding its underpinning biology have supported clinical development of novel immunotherapies. However, the results of recent trials testing these new agents raise the question on how to identify the patients that could greatly benefit. Areas covered: This article summarizes the current understanding on the biology and the mechanisms underlying different clinical features of gastric cancers. Particularly, after a comprehensive literature search, we speculate whether specific molecular subsets of patients could derive more benefit from immunotherapy. Expert commentary: Most cancers may evade the immune response, which is normally regulated by a delicate balance between activating and inhibitory signals. For example, both CTLA-4 and PD-1, once linked to PD-L1/2, may inhibit T-cell signaling. The use of agent to harness the power of the immune system appears to be the ultimate frontier in gastric cancer treatment. While anti-CTLA-4 antibodies are minimally active, there is growing evidence for the efficacy of PD1/-L1 inhibitors. The search of predictive factors for immunotherapy will provide key hints towards the optimal use of these agents.

Immunological battlefield in gastric cancer and role of immunotherapies

Like the wars predating the First World War where human foot soldiers were deemed tools in the battlefield against an enemy, so too are the host immune cells of a patient battling a malignant gastric cancer. Indeed, the tumour microenvironment resembles a battlefield, where the patient’s immune cells are the defence against invading tumour cells. However, the relationship between different immune components of the host response to cancer is more complex than an “us against them” model. Components of the immune system inadvertently work against the interests of the host and become pro-tumourigenic while other components soldier on against the common enemy – the tumour cell.