Early genetic events in HPV immortalised keratinocytes

Cancer of the uterine cervix (CaCx) is the second most common cancer in women worldwide. More than 99% of all cervical cancers contain high-risk human papillomaviruses (HPVs), with type 16 predominating. HPV infection alone is not sufficient for neoplastic progression; the HPV-infected cell must undergo additional genetic changes. Cytogenetic analysis of CaCx has been limited due to difficulties in obtaining good-quality banded chromosome preparations. Oncogenic HPVs immortalise primary genital keratinocytes in vitro, and evidence suggests that the molecular genetic and cytogenetic abnormalities observed in HPV immortalised cells reflect the in vivo changes. Therefore, these lines represent suitable models for HPV-induced carcinogenesis. We have used both spectral karyotyping (SKY) and multiplex-FISH (M-FISH) analysis to identify karyotypic changes in HPV-16 immortalised keratinocyte cell lines and established CaCx lines. SKY and M-FISH identified chromosomal abnormalities in all cell lines examined, with a translocation of chromosome 10 or i(10q) occurring in 9 of the 12 cell lines investigated. Further studies with chromosome 10 band-specific probes identified the translocation event as involving 10q with the breakpoint at 10p11.2 in some cell lines or 10q11.2 in others. The pericentric region of chromosome 10 is known to contain duplicated sequences flanking the centromeric satellites. The duplicated sequences contain many zinc finger transcription factor encoding genes and disruption of these in HPV immortalised cell lines may alter the transcription with consequences for both cellular and viral gene expression.