Functional, microarray and bioinformatics analyses of human papillomavirus E7-specific pathways in cervical carcinogenesis

Background: Human papillomavirus (HPV) vaccines are still ineffective for already infected patients. The development of new prophylactics and therapeutics for cervical cancer is hence urgently required particularly for contries and regions where medical resources are lacking. The mRNAs encoding the HPV oncogenes E6 and E7 are bicistronic and generated from the same pre-mRNA. Alternative splicing produces different mRNA variants, with the resultant balance of E6/E7 levels impacting downstream functions. Accumulating evidence suggests that E7 may contribute more closely to cervical carcinogenesis than E6. The aim of this study was to explore the E7-specific carcinogenic pathways. Methods: Small interfering RNAs knocking down either E6 or E6/E7 were transfected into CaSki and HeLa cells, and the analyses of cellular effects, microarray and bioinformatics were conducted. The survival of patients with cervical cancer based on gene expressions was analyzed utilizing a web database tool. Results: E7 knockdown induced G1 cell cycle arrest and inhibited cellular proliferation, clonogenicity and transformation. Microarray analyses identified 15 E7-specific differentially expressed genes (DEGs), and their functional annotations included “epithelial-to-mesenchymal transition”, “chromatin remodeling”, “focal adhesion: phosphatidylinositol 3-kinase (PI3K)-AKT serine/threonine kinase (Akt)-mammalian target of rapamycin (mTOR)-signaling pathway” and “DNA-binding transcription factor activity”. Pathway interaction analysis revealed that G1 cell cycle arrest was the most significant and pivotal pathway. Among the E7-specific DEGs, aldo-keto reductase family 1 member B10 (AKR1B10), family with sequence similarity 78 member A (FAM78A) and AHNAK nucleoprotein 2 (AHNAK2) exhibited tumor-suppressive effects, whereas forkhead box A1 (FOXA1), SMAD family member 9 (SMAD9) and plastin 1 (PLS1) showed oncogenic effects in survival analysis, being consistent with the expression fold differences by the microarray. Conclusions: The identified DEGs were suggested to be involved in E7-specific cervical carcinogenesis by cooperating via multiple mechanisms, providing potential novel targets and biomarkers for the more efficient prevention and treatment of cervical cancer.