Rearrangement of the same chromosome regions in different SV40 transformed human skin keratinocyte lines is associated with tumourigenicity.

Twelve different human keratinocyte strains were transformed with recombinant plasmid pSV6-1 which contained an origin defective SV40 genome. When injected into athymic nude mice lines produced either squamous cell carcinomas (SCC) in all animals, SCC in some animals and epidermal cysts in others, or epidermal cysts only in all the animals. The tumourigenic capacity of the lines could be correlated with the chromosomal changes present initially in the transformed cells. Lines which produced SCC in all the animals within a short period of time all showed simultaneous loss of part of chromosomes 3p, 8p and 11p in one homologue. Lines which were not tumourigenic did not show these simultaneously appearing rearrangements. These specific rearrangements are acquired in vitro and the time taken for a recognisable tumour to appear is related to the proportion of such cells in the line. The rearrangement of the same chromosome regions in different tumourigenic cell lines suggests that genes in these regions are important in the development of squamous cell carcinoma, possibly by loss of heterozygosity, at particular loci.