Genetic Assessment of the Strength of a Cancer Suppressor Gene in Hamster Cells1

Tetraploid and near-tetraploid chemically transformed derivatives of the pseudodiploid hamster line BHK 21/clone 13 were prepared in four different ways and their ability to be suppressed for anchorage independ ence by fusion to the anchorage-dependent parental line was tested. In all cases the presence of a single normal genome, thought on genetic grounds to contain a single suppressor gene, was able to prevent the anchorage-independent growth of transformed lines whether they con tained one or two complements of pseudodiploid chromosomes. Suppres sion of the single step in carcinogenesis that is registered by BHK cells as they transform to anchorage independence is thus unusually powerful and apparently independent of chromosome balance and of strict dosage effects.