Loss of heterozygosity of chromosome 9p21 is associated with the immortal phenotype of neoplastic human head and neck keratinocytes.

Human chromosomes 1,4,6, and 9 harbor genes which induce cellular senescence in vitro but a role for their inactivation in human tumors is not established. To investigate this we searched for loss of heterozygosity (LOH) on these chromosomes in keratinocyte cultures obtained from different stages of human squamous cell carcinoma progression. There was consistent LOH between markers D9S171 and D9S157 in 9 of 9 (100%) informative immortal cultures and in one line which entered crisis, but 0 of 7 informative senescent cultures showed LOH. These results suggest that inactivation of a gene at 9p21 is important but insufficient for human squamous cell carcinoma keratinocyte immortalization.