Therefore, we elucidated the mechanism by which OCT4 exerts its tumour‐suppressive function, showing that OCT4 is dependent on ERα to suppress the proliferation of breast cancer cells through DNMT1/ISL1/ERK axis, and this axis will be a novel potential target for improving the diagnosis, therapy and prognosis of breast cancer patients. The gene discussed is POU5F1; the disease is neoplasm.