Infection and integration of high-risk human papillomavirus in HPV-associated cancer cells.

High-risk human papillomaviruses (HPV) have been associated with many human cancers in clinical studies. Integration of HPV into the human genome is a suspected etiological factor in the induction of some HPV-associated cancers. The characteristics of HPV integration in certain HPV-integrated cancer cells remain unclear. In this study, ten HPV-associated carcinoma cell lines were evaluated for the presence, genotype, and integration status of HPV by nested polymerase chain reaction. The HPV genome did not insert in the genome of a mammary cancer cell line (MCF7), adrenal neuroblastoma cell line (NH-6), or three esophageal carcinoma cell lines (KYSE150, KYSE450 and KYSE140). HPV type 18 DNA did infect cell lines of tongue cancer (Tca83), hepatocellular carcinoma (Hep G2), and lung carcinoma (A549), but the HPV type 18 genes were not transcribed into mRNA. However, HPV type 18 integrated into the genomes of the esophageal carcinoma cell lines EC9706 and EC109, and the integration sites for both cell lines were in loci 8q24, which is a gene desert area adjacent to fragile sites. We speculate that HPV transcripts are more likely to integrate near highly susceptible fragile sites. This study suggests that HPV integration is still a significant issue that needs to be fully examined and can possibly be used as individualized biomarkers for the early diagnosis of HPV-related cancers.