20Q GAIN ASSOCIATES WITH IMMORTALIZATION - 20Q13.2 AMPLIFICATION CORRELATES WITH GENOME INSTABILITY IN HUMAN PAPILLOMAVIRUS 16 E7 TRANSFORMED HUMAN UROEPITHELIAL CELLS

Breast, bladder, colon, and ovarian carcinomas show frequent low level 20q gain and less frequently high level 20q13.2 amplification, but th e significance of these 20q amplifications in transformation has not b een defined, Using karyotypic and comparative genomic hybridization (C GH) analyses, chromosome losses and gains were analysed in six newly i mmortalized human uroepithelial cell (HUC) lines transformed by Human Papillomavirus 16 (HPV16) E7. Results showed clonal chromosomes with 2 0q11->qter gain in all six lines. CGH revealed a peak of 20q13.2 ampli fication in two cell lines. FISH with whole chromosome 20 paint showed expanded chromosome regions (ECRs) and double minute chromosomes (DMs ) that contained chromosome 20 material in cell lines with 20q13.2 amp lification. FISH with probes from the center of the 20q13.2 human brea st cancer amplicon showed as many as 24 signals in cells with 20q13.2 amplification. The acquisition of genome instability in these E7-HUCs did not correlate with TP53 mutation, as all E7-HUCs contained only wi ldtype TP53. These results suggest that low level 20q gain is associat ed with overcoming cellular senescence in E7 transformed cells (P-valu e=2x10(-7)), but does not confer genome instability, while high level 20q13.2 amplification is associated with chromosome instability. Loss of 10p (P-value=3x10(-5) was also important in immortalization of E7-t ransformed HUCs. Thus, these results have profound implications for in terpreting the significance of high versus low level 20q gains in huma n cancers.