Comparative metabolism of benzo[a]pyrene by human keratinocytes infected with high-risk human papillomavirus types 16 and 18 as episomal or integrated genomes

Neil Trushin1, Samina Alam2, Karam El-Bayoumy3, Jacek Krzeminski1, Shantu G Amin1, Jenny Gullett2, Craig Meyers2, Bogdan Prokopczyk1
1Department of Pharmacology, Penn State University, Hershey, PA 17033, USA.
2Department of Microbiology and Immunology, Penn State University, Hershey, PA 17033, USA.
3Department of Biochemistry and Molecular Biology, Penn State University, Hershey, PA 17033, USA.
DOI: 10.4103/1477-3163.92309

ABSTRACT

Background: Infection with human papillomavirus (HPV) is a critical factor in the development of cervical cancer. Smoking is an additional risk factor. Tobacco smoke carcinogens, such as benzo[a]pyrene (B[a]P), and their cytochrome P450-related metabolites are present in significantly higher levels in the cervical mucus of women smokers than in nonsmokers. We determined the metabolism and P450 expression of B[a]P-treated human keratinocytes infected with HPV-16 or -18. Materials and Methods: Monolayer cultures of uninfected primary human foreskin keratinocytes, human vaginal and cervical keratinocytes carrying episomal genomes of HPV-16 and -18, respectively, and invasive cervical carcinoma cell lines carrying either HPV-16 or -18 genomes integrated into the host DNA, were incubated with 0.1 μM [3H]B[a]P. The resulting oxidative metabolites were analyzed and quantified by radioflow high-performance liquid chromatography. Additionally, all cell lines were incubated with unlabeled 0.1 μM B[a]P for Western blot analysis of cytochrome P450 1A1 and 1B1. Results: Significant enhancement in levels of both detoxification and activation metabolites was found in incubations with all types of HPV-infected cells compared with control incubations (P < 0.05). The highest capacity to metabolize B[a]P was observed with cells containing integrated HPV-18 genomes. Induction of cytochrome 1B1 was observed in HPV-16 and -18 integrated, and in HPV-16 episomal cell types. Conclusions: Both viral genotype and genomic status in the host cell affect B[a]P metabolism and cytochrome P450 1B1 expression. An increase of DNA-damaging metabolites might result from exposure of HPV-infected women to cigarette smoke carcinogens.

Keywords: Benzo[a]pyrene metabolism, benzo[a]pyrene, cervical cancer, cigarette smoke carcinogen, cytochrome P450 1A1, cytochrome P450 1B1, human papillomavirus