KLF2 and neoplasm: On the one hand, KLF2 and KLF9 inhibit oncogenesis, with the former restraining the hypoxia-inducible factor 1 (HIF-1α)/NOTCH-1 signaling pathway that mediates cell biological processes, including cell growth and apoptosis in colorectal cancer (70), and the latter inhibiting NOTCH-1 expression and downstream signaling in tumor-initiating stem cells by binding to the NOTCH-1 promoter (71).