PCNA and cervical squamous cell carcinoma: Firstly, the expression of differential gene proteins in the SiHa cells and Ect1/E6E7 cells was found that compared with cervical squamous cell carcinoma SiHa cells, the expression of differential proteins PCNA, ATM, LIG1 and HMGB1 in Ect1/E6E7 cells decreased significantly, while the expression of TDG and OGG1 proteins increased significantly, indicating that PCNA, ATM, LIG1 and HMGB1 may be oncogenes or play a role in promoting cancer, while TDG and OGG1 may be tumor suppressor genes or play a role in inhibiting cancer.