Aberrant alternative splicing of RHOA is associated with loss of its expression and activity in diffuse-type gastric carcinoma cells

RhoA is a member of Rho family small GTPases that regulates diverse cellular functions. Recent large-scale sequencing studies have identified recurrent somatic mutations of RHOA in diffuse-type gastric carcinoma (DGC), indicating that RHOA is a driver of DGC. In this study, we investigated the possible abnormalities of RHOA in a panel of gastric carcinoma (GC) cell lines. Pulldown assay and immunoblot analysis showed that the activity and expression of RhoA were detectable in all GC cell lines tested, except for two DGC cell lines, HSC-59 and GSU. RHOA coding region sequencing revealed that aberrant alternative splicing of RHOA occurred in these cell lines. Quantitative real-time PCR analysis showed that the expression of wild-type RHOA was nearly undetectable, whereas splicing variants were almost exclusively expressed in HSC-59 and GSU cell lines. However, the expression levels of RHOA splicing variants were very low and the corresponding proteins were not detected by immunoblotting. Moreover, the splicing isoforms of RhoA protein were neither efficiently expressed nor activated even if ectopically expressed in cells. These results indicate that aberrant alternative splicing of RHOA results in the loss of its activity and expression in DGC cells.