Comparison of immune-related gene expression between primary and metastatic site in advanced gastric cancer patients with peritoneal dissemination.

Abstract

423 Background: Immune checkpoints inhibitor (ICI) is effective and approved in some solid tumors including advanced gastric cancer (GC). Peritoneal dissemination is known as a poor prognostic factor and was reported to be associated with the resistance to ICI according to the previous reports. The aim of our study is to compare the immune-related gene expression between primary site and peritoneal lesion in advanced GC patients. Methods: Among advanced GC patients, we selected those who underwent surgical resection for both primary and peritoneal lesions simultaneously. Formalin-fixed paraffin-embedded (FFPE) tumor tissues of primary and peritoneal lesions were prepared and RNA was extracted by Maxwell RSC RNA FFPE kit (Promega). Immune-related gene expression was evaluated by using nCounter Max Analysis System (NanoString). We used nCounter PanCancer Immune Profiling Panel Kit which includes 770 immune-related genes. Results: Immune-related gene expression was evaluated by using twenty-four FFPE tumor tissues in twelve GC patients. Scatter plot and hierarchical clustering analyses showed that the pattern of immune-related gene expression was not much different between primary and peritoneal lesions beyond the individual differences. Regarding the T cell function, high expression of Immune-related genes was widely detected in patients with EB virus-positive (n = 2) and HER2-positive (n = 1). Gene expressions such as CD70, FAS, MAF and IL-3 were higher in peritoneal lesion compared with primary lesion (p < 0.05). Whereas, expressions of F2RL1 and IL-11 were lower in peritoneal lesion compared with primary lesion (p < 0.05). Conclusions: Our study indicated that there was not much difference of Immune-related gene expression between primary and peritoneal lesion in advanced GC patients. Positive status of EB virus and HER2 may be associated with high expression of immune-related genes. Further analysis to evaluate immune-related gene expression between primary and metastatic site may contribute the further understanding of cancer immunity in advanced GC.