Ras-Related Mutants Identified in Young-Onset Colorectal Cancer Display Divergent Phenotypes and Retain Their Pro-Angiogenic Effects

The <i>Ras-related</i> (<i>RRAS</i>) gene is a member of the Ras superfamily and remains largely uncharacterized compared to <i>KRAS</i>, <i>NRAS</i>, and <i>HRAS</i>. Its role in tumorigenesis remains poorly documented, as evidenced by its lack of canonical mutations in any cancer type. This study investigated the effects of the novel <i>RRAS</i> R78W and E63D mutants-identified in Filipino young-onset colorectal cancer (YO-CRC) patients-on cancer hallmarks. In silico analysis was performed to predict the effect of the mutations on RRAS structure. F-actin staining of transfected NIH3T3 cells displayed massive cytoskeletal remodeling and formation of migratory and invasive structures. RRAS R78W enhanced migration when compared to wild-type RRAS in NIH3T3 and HCT116 cells, whereas neither mutant affected invasive capacity. Both mutants did not abolish the pro-angiogenic ability of wild-type RRAS in endothelial tube formation assays. RRAS E63D conferred resistance to apoptosis in both cell lines. Both mutants had no effect on cellular proliferation in either cell line. Overexpression of both mutants did not increase Akt and Erk1/2 phosphorylation. In silico analysis further suggests that the mutations confer increased GEF-binding ability versus wild-type. Results of the study highlight the need to characterize Ras isoform- and mutation-specific phenotypic effects, which may have repercussions in CRC management.