Exploration Of The Role Of FEN1 In Cervical Squamous Intraepithelial Lesions And Cervical Cancer

Objective: Cervical cancer is the fourth most common cancer in female worldwide.Cervical squamous intraepithelial lesion is the pre-malignancy of cervical cancer.FEN1 participates in many important pathways of DNA metabolic,and its role in tumorigenesis has been widely studied.The main purpose of this study is to explore the role of FEN1 in cervical squamous intraepithelial lesions and cervical cancer.Methods: First of all,the gene expression profile data of GSE63514,GSE27678 and GSE7803 were downloaded from GEO database to analyze whether FEN1 and p16 were differentially expressed genes in the progression of cervical lesions,and the relationship between the expression levels of FEN1 and p16 and the degree of cervical lesions.The co-expression of FEN1 and p16 was also analyzed.In order to verify the results,a total of156 cervical tissue samples(21 normal samples,24 CIN1,18 CIN2,22 CIN3 and 71 cervical cancer samples)were included for immunohistochemistry.According to the results of immunohistochemistry,the positive rates of FEN1 and p16 in each group were counted.The sensitivity,specificity,PPV,NPV and ROC curve were calculated to evaluate the effect of single or combined use of FEN1 and p16 in the diagnosis of CIN2 and above lesions(Different group exploration based on whether cancer samples are included or not).In addition,GEPIA was used to verify the expression level of FEN1 in cervical cancer and normal samples.From the TCGA database,the clinical information and expression data of304 cervical cancer patients were downloaded.Based on the median value of FEN1 expression,the patients were divided into two groups(High-/Low-FEN1 expression group).The relationship between FEN1 expression and prognosis of cervical cancer patients was analyzed.At the same time,we also analyzed whether there was any difference in the expression of FEN1 among the groups of clinical factors.In order to explore the possible pathways affected by FEN1,GSEA analysis was performed in this study.Besides,61 of the71 cervical cancer samples included in this study had survival information.According to the immunohistochemical score,the relationship between the FEN1 expression and the prognosis of patients was analyzed.Results: The results of differential gene analysis suggested that FEN1 and p16 were not differentially expressed genes in LSIL vs.Normal group.While in both HSIL vs.Normal and Cancer vs.Normal groups,FEN1 and p16 were up-regulated genes.In the three data sets,the expression level of FEN1 and p16 was positively correlated with cervical lesions’ degree,and there was a high co-expression correlation between FEN1 and p16.The statistical results showed that the sensitivity,specificity,PPV and NPV of FEN1 for the diagnosis of CIN2 and CIN3 lesions were 87.50%,93.33%,92.11%,89.36%,respectively,and the sensitivity,specificity,PPV and NPV for the diagnosis of CIN2,CIN3 and cervical cancer were 84.49%,93.33%,96.97%,73.68%,respectively.The sensitivity,specificity,PPV and NPV of p16 for the diagnosis of CIN2 and CIN3 lesions were 100%,57.58%,67.80%,100%,respectively,and the sensitivity,specificity,PPV and NPV for the diagnosis of CIN2,CIN3 and cervical cancer were 99.10%,57.58%,85.27%,96.30%,respectively.When FEN1 and p16 were combined used,the sensitivity,specificity,PPV and NPV for the diagnosis of CIN2 and CIN3 lesions were 87.50%,95.56%,94.59%,91.49%,respectively and for the diagnosis of CIN2,CIN3 and cervical cancer,the sensitivity,specificity,PPV and NPV were 85.59%,94.59%,97.94%,72.88%,respectively.For CIN2 and CIN3,the areas under the ROC curve of FEN1,p16 and FEN1 combined with p16 were 0.9,0.79 and0.92,respectively,and for CIN2,CIN3,and cervical cancer,the areas under the ROC curve of FEN1,p16 and FEN1 combined with p16 were 0.9,0.78 and 0.91,respectively.The results of GEPIA showed that FEN1 was overexpressed in cervical cancer.Both the TCGA database and samples included in this study indicated FEN1 was not related to prognosis of cervical cancer patients.Also,there was no significant difference in FEN1 expression among different clinical factors such as FIGO stage and differentiation.The results of GSEA suggested that FEN1 was related to base excision repair pathway,DNA replication pathway,nucleotide excision repair pathway and other pathways.Conclusions: The combination use of FEN1 and classical marker p16 can significantly improve the effect of diagnosis of patients with CIN2+ lesions.FEN1 expression level was not correlated with important clinical factors such as FIGO stage and prognosis of patients with cervical cancer.In addition,FEN1 may affect some important DNA metabolic pathways,such as base excision repair pathway and DNA replication pathway.