Human papillomavirus type 18 E6 and E7 genes integrate into human hepatoma derived cell line Hep G2.
OBJECTIVE
Human papillomaviruses have been linked causally to some human cancers such as cervical carcinoma, but there is very little research addressing the effect of HPV infection on human liver cells. We chose the human hepatoma derived cell line Hep G2 to investigate whether HPV gene integration took place in liver cells as well.


METHODS
We applied PCR to detect the possible integration of HPV genes in Hep G2 cells. We also investigated the expression of the integrated E6 and E7 genes by using RT-PCR and Western blotting. Then, we silenced E6 and E7 expression and checked the cell proliferation and apoptosis in Hep G2 cells. Furthermore, we analyzed the potential genes involved in cell cycle and apoptosis regulatory pathways. Finally, we used in situ hybridization to detect HPV 16/18 in hepatocellular carcinoma samples.


RESULTS
Hep G2 cell line contains integrated HPV 18 DNA, leading to the expression of the E6 and E7 oncogenic proteins. Knockdown of the E7 and E6 genes expression reduced cell proliferation, caused the cell cycle arrest at the S phase, and increased apoptosis. The human cell cycle and apoptosis real-time PCR arrays analysis demonstrated E6 and E7-mediated regulation of some genes such as Cyclin H, UBA1, E2F4, p53, p107, FASLG, NOL3 and CASP14. HPV16/18 was found in only 9% (9/100) of patients with hepatocellular carcinoma.


CONCLUSIONS
Our investigations showed that HPV 18 E6 and E7 genes can be integrated into the Hep G2, and we observed a low prevalence of HPV 16/18 in hepatocellular carcinoma samples. However, the precise risk of HPV as causative agent of hepatocellular carcinoma needs further study.
Department of Histology and Embryology, Shantou University Medical College, Guangdong Province, China.
Tianzhong
T
Ma
Zhongjing
Z
Su
Ling
L
Chen
Shuyan
S
Liu
Ningxia
N
Zhu
Lifeng
L
Wen
Yan
Y
Yuan
Leili
L
Lv
Xiancai
X
Chen
Jianmin
J
Huang
Haibin
H
Chen
D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000821:virology*; D002453:Cell Cycle; D049109:Cell Proliferation; D004279:DNA, Viral / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D056945:Hep G2 Cells / Q000378:metabolism / Q000821:virology; D052162:Human papillomavirus 16; D052161:Human papillomavirus 18 / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism / Q000821:virology; D008113:Liver Neoplasms / Q000235:genetics* / Q000821:virology*; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D050725:Papillomavirus E7 Proteins / Q000235:genetics; D030361:Papillomavirus Infections / Q000821:virology; D016133:Polymerase Chain Reaction; D016662:Virus Integration
D004279:DNA, Viral; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins