FEN1 and neoplasm: Inhibition of FEN1 expression not only suppressed the proliferation of cancer cells but promotes apoptosis and reduced the drug resistance of cancer cells.16,25,29–32 Similarly, in the present study, we showed that the tumor volume was limited by FEN1 downregulation and that FEN1 knockdown significantly attenuated the proliferation and migration of Cal-27 cells, promoted apoptosis and caused cell cycle arrest in the G0/G1 phase.