The integration of HPV-18 DNA in cervical carcinoma

Aims-Little information is available on the patterns of integration into th e host chromosomal DNA of cervical carcinomas of human papillomavirus type 18 (HPV-18) DNA, which is associated with up to 20% of these carcinomas. Be cause integration of the viral genome may be extremely important in the pat hogenesis of cervical carcinoma, the aim of this study was to investigate w hich regions of HPV-18 DNA are integrated into the cellular DNA of cervical carcinomas. Methods-Southern analysis using four subgenomic probes covering the entire HPV-18 genome was used to map viral DNA integrated within cellular DNA. The polymerase chain reaction (PCR) was used to confirm the presence of specif ic regions of the viral genome. Results-In all 11 carcinomas there was a single major HPV-18 DNA integrant, retaining similar to 4000 bp of HPV-18 DNA, indicating that approximately half of the virus genome had been lost upon integration. Southern analysis suggested strongly that the viral breakpoint was within the E1/E2 gene boun dary, with concomitant loss of part or all of the E2 ORF (open reading fram e), all of the E4, E5, and L2 ORFs and part of the L1 ORF. These data were supported by the PCR results, which confirmed that the region of integrated HPV-18 DNA from nucleotides 6558 to 162 was present in all the carcinoma s amples studied. Assuming that no genomic rearrangements, deletions, or inse rtions had occurred, 4131 bp of integrated HPV-18 DNA could be accounted fo r in eight cervical carcinoma samples. The results of Southern analysis als o suggested that integration of HPV-18 DNA may have occurred at a specific host chromosomal site. Conclusions-Broadly, the viral sequences retained upon HPV-18 integration r esemble those found when HPV-16 is integrated. However, it appears that the HFV-18 E2 region is more consistently deleted.