Mechanistically, RAC1B conferred resistance to TGFβ-induced cell death through downregulation of core TGFβ pathway genes and the pro-apoptotic target gene Bim. Moreover, we observed an association between mutations in the TGFβ signalling pathway and RAC1B expression in human tumours samples from the TCGA database, suggesting that RAC1B might act as a non-mutational mechanism for attenuating the anti-tumorigenic functions of the TGFβ pathway in tumour initiating cells. Here, TGFB1 is linked to neoplasm.