A threshold effect in the induction of tumorigenicity of an established human cell line by v-mos.

The nontumorigenic immortal human cell line, SV80, was transfected with the v-mos gene to assess the gene's effect on tumorigenicity of cultured human cells. Two classes of cells, each containing functional v-mos, were obtained. The first class contained low levels of v-mos RNA, was morphologically transformed, but was nontumorigenic in nude mice. The second was also morphologically transformed, but contained high levels of v-mos RNA and was tumorigenic. The results indicate that SV80 cells behave similarly to murine fibroblasts in their response to v-mos in that they can be rendered tumorigenic by the viral oncogene. However, tumorigenicity was effected through a mechanism which involves different threshold doses for morphologic and tumorigenic transformation.