The association of B7-H6 expression to the immune microenvironment in gastric cancer.

Abstract

4025 Background: B7-H6, also known as NCR3LG1, is a promising molecule in B7 family and a ligand of natural killer (NK) -cell-activating receptor NKp30. B7-H6 can bind NKp30 and induce NK activation and cytokine secretion to exert anti-tumor effects. Studies have reported that the B7-H6 expression is significantly correlated with post-operative prognosis and distant metastasis status in patients with cancer. In patients with gastric cancer, B7-H6 high expression is significantly associated with longer OS. However, the effects of B7-H6 on immunotherapy and immune microenvironment are unknown. Herein, we used the data from TCGA database of gastric cancer to analyze the influence of B7-H6 expression on immune microenvironment. Methods: The gene expression profile and clinical data in gastric cancer were extracted from TCGA database ( http://cancergenome.nih.gov ). According to the previous reported article, 15 was chosen as the cutoff value for the expression of B7-H6, and the expression of B7-H6 is divided into two groups, high group (B7-H6 expression＞15) and low group (B7-H6 expression≤15). Kaplan-Meier analysis was used to verify the influence of B7-H6 expression on OS prognosis. “Cell Type Identification by Estimating Relative Subsets of RNA Transcripts” (CIBERSORT) algorithm was used to analyze the proportion of immune-related cells in the two groups. “Estimation of STromal and Immune cells in Malignant Tumours using Expression data” (ESTIMATE) algorithm was used to analyze stromal and immune scores in the two groups. The differences of immune-related signatures between the two groups were calculated according to previous reports. Results: Kaplan-Meier survival analysis showed that high group was significantly associated with longer overall survival (p value = 0.016), which was consistent with previous reports. The result of CIBERSORT algorithm showed that the proportion of activation immune correlation CD8(+) T cells and NK active cells was significantly higher in low group than in high group (p＜0.05). Meanwhile, the proportion of immune suppressive correlation CD4 resting memory T cell was significantly lower in low group than in high group (p＜0.05). The result of ESTIMATE algorithm showed that the stromal score, immune score, and ESTIMATE score in low group were significantly higher than in high group (p＜0.01). The immune-related signatures, including immune signature, expanded immune signature, TLS signature, myeloid cell chemotaxis, tertiary lymphoid structure, were significantly higher in low group than in high group (p＜0.05). Conclusions: The low B7-H6 expression was correlated with better immune microenvironment. The effect of B7-H6 expression on immunotherapy needs to be further explored.