KLF4 and neoplasm: For example, the transient in vivo expression of reprogramming factors required for iPSC generation, octamer-binding transcription factor 3/4 (OCT3/4), Krüppel-like factor 4 (KLF4), SRY-box 2 (SOX2), and MYC, results in tumour development in various tissues containing undifferentiated cells with global changes in DNA methylation patterns5.