PCNA and squamous cell intraepithelial neoplasia: The results of co-culture suggest that Lactobacillus crispatus can significantly inhibit the expression of ABCG2, PCNA, ATM, LIG1, OGG1 and HMGB1 proteins but promote the expression of TDG protein in Ect1/E6E7 cells, which may reverse the progress of SIL.