PCNA and squamous cell intraepithelial neoplasia: This study suggests that Lactobacillus crispatus can significantly inhibit the expression of potential oncogenes ABCG2, LIG1, PCNA, ATM, OGG1 and HMGB1 in Ect1/E6E7 cells, but up regulate the expression of tumor suppressor gene TDG, which may reverse the progress of SIL.