Copy number variations of HLA-I and activation of NKp30 pathway determine the sensitivity of gastric cancer cells to the cytotoxicity of natural killer cells

Exploration of signature based on T cell-related genes in stomach adenocarcinoma by analysis of single cell sequencing data

BACKGROUND

Gastric cancer (GC) is a leading reason for the death of cancer around the world. The immune microenvironment counts a great deal in immunotherapy of advanced tumors, in which T cells exert an indispensable function.

METHODS

Single-cell RNA sequencing data were utilized to characterize the expression profile of T cells, followed by T cell-related genes (TCRGs) to construct signature and measure differences in survival time, enrichment pathways, somatic mutation status, immune status, and immunotherapy between groups.

RESULTS

The complex tumor microenvironment was analyzed by scRNA-seq data of GC patients. We screened for these T cell signature expression genes and the TCRGs-based signature was successfully constructed and relied on the riskscore grouping. In gene set enrichment analysis, it was shown that pro-tumor and suppressive immune pathways were more abundant in the higher risk group. We also found different infiltration of immune cells in two groups, and that the higher risk samples had a poorer response to immunotherapy.

CONCLUSION

Our study established a prognostic model, in which different groups had different prognosis, immune status, and enriched features. These results have provided additional insights into prognostic evaluation and the development of highly potent immunotherapies in GC.

Tumor microenvironment-mediated immune tolerance in development and treatment of gastric cancer

Tumor microenvironment is the general term for all non-cancer components and their metabolites in tumor tissue. These components include the extracellular matrix, fibroblasts, immune cells, and endothelial cells. In the early stages of tumors, the tumor microenvironment has a tumor suppressor function. As the tumor progresses, tumor immune tolerance is induced under the action of various factors, such that the tumor suppressor microenvironment is continuously transformed into a tumor-promoting microenvironment, which promotes tumor immune escape. Eventually, tumor cells manifest the characteristics of malignant proliferation, invasion, metastasis, and drug resistance. In recent years, stress effects of the extracellular matrix, metabolic and phenotypic changes of innate immune cells (such as neutrophils, mast cells), and adaptive immune cells in the tumor microenvironment have been revealed to mediate the emerging mechanisms of immune tolerance, providing us with a large number of emerging therapeutic targets to relieve tumor immune tolerance. Gastric cancer is one of the most common digestive tract malignancies worldwide, whose mortality rate remains high. According to latest guidelines, the first-line chemotherapy of advanced gastric cancer is the traditional platinum and fluorouracil therapy, while immunotherapy for gastric cancer is extremely limited, including only Human epidermal growth factor receptor 2 (HER-2) and programmed death ligand 1 (PD-L1) targeted drugs, whose benefits are limited. Clinical experiments confirmed that cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), vascular endothelial growth factor receptor (VEGFR) and other targeted drugs alone or in combination with other drugs have limited efficacy in patients with advanced gastric cancer, far less than in lung cancer, colon cancer, and other tumors. The failure of immunotherapy is mainly related to the induction of immune tolerance in the tumor microenvironment of gastric cancer. Therefore, solving the immune tolerance of tumors is key to the success of gastric cancer immunotherapy. In this study, we summarize the latest mechanisms of various components of the tumor microenvironment in gastric cancer for inducing immune tolerance and promoting the formation of the malignant phenotype of gastric cancer, as well as the research progress of targeting the tumor microenvironment to overcome immune tolerance in the treatment of gastric cancer.

Application progress of liquid biopsy in gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors globally. Guiding the individualized treatment of GC is the focus of research. Obtaining representative biological samples to study the biological characteristics of GC is the focus of diagnosis and treatment of GC. Liquid biopsy technology can use high-throughput sequencing technology to detect biological genetic information in blood. Compared with traditional tissue biopsy, liquid biopsy can determine the dynamic changes of tumor. As a noninvasive auxiliary diagnostic method, liquid biopsy can provide diagnostic and prognostic information concerning the progression of the disease. Liquid biopsy includes circulating tumor cells, circulating tumor DNA, circulating tumor RNA, tumor educated platelets, exosomes, and cytokines. This article describes the classification of liquid biopsy and its application value in the occurrence, development, and therapeutic efficacy of GC.

Therapeutic Potential of Natural Killer Cells in Gastric Cancer

Gastric cancer (GC) is one of the most common cancers, with a high incidence of cancer death. Despite various therapeutic approaches, the cures and prognosis of advanced GC remain poor. Natural killer (NK) cells, which are known as important lymphocytes in innate immunity, play vital roles in suppressing GC initiation, progression, and metastases. A wide range of clinical settings shows that increasing the number of NK cells or improving NK cell antitumor activity is promising in GC patients. NK cell adoptive therapy (especially expanded NK cells) is a safe and well-tolerated method, which can enhance NK cell cytotoxicity against GC. Meanwhile, cytokines, immunomodulatory drugs, immune checkpoint blockades, antibodies, vaccines, and gene therapy have been found to directly or indirectly activate NK cells to improve their killing activity toward GC. In this review, we summarize recent advancements in the relationship between NK cells and GC and point out all the innovative strategies that can enhance NK cells' function to inhibit the growth of GC.

Enah overexpression is correlated with poor survival and aggressive phenotype in gastric cancer

Enabled homolog (Enah), which is a member of the Ena/VASP family that also includes VASP (vasodilator-stimulated phosphoprotein) and Ena/VASP like, is a mammalian ortholog of Drosophila Enabled (Ena). An increasing number of studies demonstrated Enah overexpression is involved in human colorectal carcinomas, breast cancers and hepatocellular carcinoma. However, the significance of Enah expression in gastric cancer (GC) is poorly elucidated. Here, we demonstrate that Enah is upregulated in GC and associated with AJCC stage, depth of invasion and poor overall survival (OS). Knockdown of Enah inhibited GC cell proliferation and metastasis and vice versa. Further experiments suggested that p-Erk1/2, p-AKT, p-p65, Vimentin and Fibronectin were downregulated and E-cadherin was upregulated after Enah silencing, implicating altered functions in GC proliferation and metastasis. Thus, our study suggests that Enah is a harmful factor for GC and a novel target for GC treatment.

The role of MALAT-1 in the invasion and metastasis of gastric cancer

OBJECTIVES

The long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT-1) has been reported to be over-expressed in several cancer types. However, its role in gastric cancer (GC) remains unclear. In the present study, we examined the expression of MALAT-1 in GC cells and tissues and explored its role in GC cell migration and invasion.

MATERIALS AND METHODS

Real-time quantitative polymerase chain reaction (qRT-PCR) was used to analyze the expression level of MALAT-1 in six GC cell lines and 20 gastric tissues (20 GC and 20 adjacent normal mucosa). Functional characterization for the role of MALAT-1 in GC was performed by small interfering RNA (siRNA) knockdown, followed by series of in vitro and in vivo experiments.

RESULTS

MALAT-1 was upregulated in GC cell lines and tissues compared with the immortalized gastric epithelial cell line GES and adjacent normal tissues, respectively. Moreover, MALAT-1 expression was higher in the high-metastatic-potential GC cell line SGC7901M than in the low-metastatic-potential GC cell line SGC7901NM. In vitro and in vivo assays showed that siRNA-mediated silencing of MALAT-1 inhibited GC cell migration and invasion. In addition, suppressing MALAT-1 expression resulted in a decrease in the expression of the Epithelial-mesenchymal transition (EMT)-associated marker vimentin and an increase in the expression of E-cadherin at both the mRNA and protein levels.

CONCLUSIONS

MALAT-1 may promote the migration and invasion of GC cells in part by regulating EMT.