HBV Integration-mediated Cell Apoptosis In HepG2.2.15

Objective Hepatocellular carcinoma(HCC)is the most common type of primary liver cancer and the fourth leading cause of cancer deaths in the word.Hepatitis B virus(HBV)can integrate into host cells,affect gene transcription and protein translation,and change cell phenotype and function.HBV infection plays an important role in the development of HCC.However,the mechanisms by which HBV integration affects host cells remain poorly understood.This study is aiming to explore mechanisms of HBV integration and provide new sights into HBV-associated functional changes.Methods HepG2.2.15 cell line is derived from the human HCC cell line Hep G2 by stable transfection with HBV genotype D,thus it is a suitable model for the investigation of HBV integration.HBV capture sequencing was conducted in both genome and transcriptome level to detect HBV integration sites.Cell viability was measured using MTS assay.Flow cytometry was performed to detect cell cycle and cell apoptosis.Gene expression was detected through RT-PCR and Western blot.Results HepG2.2.15 cells showed decreased proliferation,G1 cell cycle arrest and increased apoptosis,when compared to Hep G2 cells.HBV capture sequencing was conducted in both genome and transcriptome level,followed by RNA expression sequencing in HepG2.2.15.Here,CAMSAP2/CCDC12/DPP7/OR4F3 were found to be targets for HBV integration in both genome and transcriptome level,accompanied by alteration in their expression when compared to Hep G2.Among these genes,DPP7 was the only gene with HBV integration into its exon,meanwhile DPP7 expression level was also downregulated in HepG2.2.15 as compared to Hep G2.Furthermore,DPP7 knockdown resulted in increased apoptosis with upregulation of the Bax/Bcl2 ratio in Hep G2 cells.Conclusion In brief,HBV integration affects gene transcription and protein translation with decreased proliferation,G1 cell cycle arrest and increased apoptosis in HepG2.2.15.Furthermore,HBV integration mediates cell apoptosis through regulating DPP7 in HepG2.2.15.