Amplification of chromosome 5p correlates with increased expression of Skp2 in HPV-immortalized keratinocytes

The oncogenic HPVs immortalize primary genital keratinocytes in vitro and there is evidence that such lines represent suitable models to examine HPV-induced carcinogenesis. Early in vivo studies and more recent CGH analyses have revealed amplification of chromosome 5p in advanced stage carcinoma of the uterine cervix (CaCx). In the present study, a panel of established CaCx-derived cell lines were analysed by M-FISH to identify recurrent karyotypic abnormalities. Amplification of 5p was observed in 11 of 13 CaCx cell lines harbouring HR (high-risk) HPV. The region of 5p undergoing amplification was confirmed using human band-specific paints. The F-box protein Skp2 is present at 5p13 and its protein is present at increased levels in many cancers of an advanced stage. The HPV16-harbouring cell line W12 shows progressive morphological abnormality with in vitro passage, culminating in an invasive phenotype. The expression of Skp2 at different stages of this progression was investigated utilizing Western blot and TaqMan quantitative PCR. At medium to late passage, gain of 5p as an isochromosome was observed. Increased expression of Skp2 and a reduction in the expression of its target p27 correlated with increasing passage in this line.