AbstractBackground and aims
The transcription factor Atoh1 plays crucial roles in the differentiation of the secretory intestinal epithelium cells. Although we have reported that Atoh1 protein was degraded in colon cancer, the Atoh1 expression and function in various cancers are still controversial. Moreover, it remains unknown whether Atoh1 contributes to cancer stemness. We therefore aim to investigate the Atoh1 function in colon cancer.Methods
Mutated Atoh1 protein combined with mcherry (5SA-Atoh1) was generated and stably expressed in colon cancer cells. 5SA-Atoh1 cells were analyzed for differentiation and cancer stem cell phenotype expression by RT–PCR, immunofluorescent staining and reporter assay. Cell proliferation and chemoresistance were analyzed by MTS assay, FUCCI system with timelapse live imaging and measurement of tumor size after inoculation of cells into mice.Results
Mutated Atoh1 protein was stably expressed in cancer cells, resulting in the acquisition of not only the differentiated form but also cancer stemness. Atoh1 protein stabilization induced the expression of Wnt target genes by enhancement of the Wnt signal. Moreover, cell cycle arrest in G0/G1 phase was induced by the Atoh1 protein stabilization, resulting in the acceleration of cell survival and chemoresistance. Furthermore, oxaliplatin was found to inactivate GSK3 kinase, resulting in the stabilization of Atoh1 protein in wild-type Atoh1 gene-positive cancer. Subsequently, Atoh1-positive cancer acquired chemoresistance in vivo.Conclusions
The Atoh1 protein regulates the cancer stemness rather than differentiation phenotype in colon cancer, suggesting the mechanism by which mucinous cancer resists chemotherapy. Moreover, measurement of Atoh1 gene/protein expression in colon cancer might be useful to predict the effect of chemotherapy.