POU5F1 and cancer: 75). The four Yamanaka transcription factors (Oct4, Sox2, Klf4 and c-Myc) that are used in iPSC induction contribute to the carcinogenesis of iPSCs. Overexpression of Oct4 can induce miR-125b expression to prevent tumour cell apoptosis and maintain the stemness of many types of cancer cells (Refs. 76, 77). Sox2 can form a heterodimer with Oct4 and downregulate the expression of CDX2 to help maintain the stem-like state of tumour cells (Ref. 78). Klf4 can also help convert cancer cells into a stem-like state through increasing the expression of E-cadherin (Ref. 79).