OCT4 Potentiates Radio-Resistance and Migration Activity of Rectal Cancer Cells by Improving Epithelial-Mesenchymal Transition in a ZEB1 Dependent Manner

Radiotherapy is an important strategy for rectal cancer patient treatment. However, the efficiency of radiation is usually poor, especially in patients with advanced stage rectal cancer due to the radio-resistance developed. At the present study, OCT4 was found to play a critical role in radio-resistance development in human rectal cancer cells by improving the epithelial-mesenchymal transition process (EMT). Endogenous OCT4 expression could confer resistant phonotype on human rectal cancer cells, which was supported by the data from clonogenic forming assay and cell cycle arrest recovering experiment. EMT related transcription factor ZEB1 might take part in the radio-resistance induced by OCT4, as its expression could be upregulated by OCT4 and its silence could reverse the OCT4 induced resistance to radiation in SW480 cells. More interestingly, CHK1 was also upregulated in OCT4/ZEB1 dependent manner conferring stronger DNA damage repair activity on cancer cells, which might explain the underlying mechanisms why OCT4/ZEB1 axis could promote the resistance of human rectal cancer cell to radiation. Taken together, our results provided a novel mechanism for radio-resistance development in human rectal cancer cells and a new target to overcome this resistance.