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 se nescence in vitro but a role for their inactivation in human tumors is not established. To investigate this we searched for loss of heterozy gosity (LOH) on these chromosomes in keratinocyte cultures obtained fr om different stages of human squamous cell carcinoma progression. Ther e 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 su ggest that inactivation of a gene at 9p21 is important but insufficien t for human squamous cell carcinoma keratinocyte immortalization.