Integration sites of human papillomavirus 18 in esophageal cancer samples

To investigate the association between human papillomavirus (HPV) infection and esophageal cancer, genomic DNA was isolated from 189 samples obtained from patients with esophageal carcinoma, and HPV DNA was identified using the polymerase chain reaction (PCR) with the following specific primers: My09/11 for HPV L1 and HPV18 E6 for HPV18. The HPV18 gene products were sequenced to identify the HPV genotype and the HPV18 integration site was verified using PCR amplification of papillomavirus oncogene transcripts. HPV18 oncogene transcript products were ligated into a pMD-18T plasmid vector and sequenced to confirm the physical location of HPV18 integration. Of the 189 samples, 168 were positive for HPV, of which 33 were positive for HPV18. The sequencing analysis identified two HPV18 E6-positive samples containing one mutation and two samples containing two mutations in the viral DNA. In total ~600 bp of the HPV18 oncogene transcript was detected in three esophageal cancer samples. Sequence analysis revealed that, in two patients, the HPV18 infection was integrated into human chromosome 5, whereas in the remaining sample the virus was integrated into human chromosome 2. The high prevalence of HPV18 infection suggested that HPV18 infection is a pathogenic factor in esophageal carcinoma progression. The integration of HPV18 DNA into the host cell genome suggests that persistent HPV infection has a role in esophageal epithelial cell malignant transformation and carcinogenesis.