FEN1 and cancer: Specially, contrary to FEN1's role as a tumor suppressor in some types of cancer [22], our chi-square test suggests that the over-expression of FEN1 in atypical hyperplasia and ESCC tumor tissues was statistically significant (P < 0.001), account for 53% of ESCCs (Figure 2F), indicating that FEN1 may be required to support the growth and progression of ESCC.