Suppressive effects of EB virus infection on HER2 expression in gastric cancer cells

Epstein–Barr virus (EBV) infection is present in 10% of gastric cancer cases and plays a role in carcinogenesis. HER2 expression has received increasing attention since the efficacy of an anti-HER2 antibody, trastuzumab, in gastric cancer with HER2 overexpression was shown. However, a significantly lower frequency of HER2 overexpression has been observed in EBV+ gastric cancers. The aim of this study was to analyze the association between EBV infection and HER2 expression ingastric cancer cell lines. We used a HER2-positive gastric cancer cell line named JRST. The cells were infected with EBV using the cell-cell contact method and were designated as JRST-EBV. Cell lines transfected with a neomycin resistance gene were also established; these were used as controls and were referred to as JRSTNeo. We analyzed the effects of EBV infection on JRST using real-time RT-PCR, western blots, MTT assays, scratch assays, and caspase 3 assays. HER2 mRNA expression levels were similar in JRST-EBV and JRST-Neo cells. In contrast, HER2 protein expression levels were lower in JRST-EBV cells than in JRST-Neo cells. Expression of phospho MAPK and phospho Akt, both of which are downstream signal molecules of HER2, was also reduced in JRST-EBV cells. MTT assays showed that proliferation activity was significantly lower in JRST-EBV cells than in JRST-Neo cells. Scratch assays showed that cell migration was significantly lower in JRST-EBV cells than in JRST-EBV cells. Caspase 3 assays showed that trastuzumab-induced apoptosis was lower in JRST-EBV cells than in JRST-Neo cells. Trastuzumab reduced migration of JRST-Neo cells but not that of JRST-EBV cells. These results suggest that EBV infection plays a suppressive role in HER2 expression in gastric cancer cells, which may explain the mutually exclusive relationship between EBV infection and HER2 expression in human gastric cancer.