Enhanced O-GlcNAc modification induced by the RAS/MAPK/CDK1 pathway is required for SOX2 protein expression and generation of cancer stem cells

Cancer stem cells (CSCs) have tumour initiation, self-renewal, and long-term tumour repopulation properties, and it is postulated that differentiated somatic cells can be reprogrammed to CSCs by oncogenic signals. We previously showed that oncogenic HRAS(V12) conferred tumour initiation capacity in tumour suppressor p53-deficient (p53(−/−)) primary mouse embryonic fibroblasts (MEFs) through transcription factor NF-κB-mediated enhancement of glucose uptake; however, the underlying mechanisms of RAS oncogene-induced CSC reprogramming have not been elucidated. Here, we found that the expression of the reprogramming factor SOX2 was induced by HRAS(V12) in p53(−/−) MEFs. Moreover, gene knockout studies revealed that SOX2 is an essential factor for the generation of CSCs by HRAS(V12) in mouse and human fibroblasts. We demonstrated that HRAS(V12)-induced cyclin-dependent kinase 1 (CDK1) activity and subsequent enhancement of protein O-GlcNAcylation were required for SOX2 induction and CSC generation in these fibroblasts and cancer cell lines containing RAS mutations. Moreover, the CDK inhibitor dinaciclib and O-GlcNAcylation inhibitor OSMI1 reduced the number of CSCs derived from these cells. Taken together, our results reveal a signalling pathway and mechanism for CSC generation by oncogenic RAS and suggest the possibility that this signalling pathway is a therapeutic target for CSCs.