TRANSFORMATION OF RAT FIBROBLASTS BY TGF-BETA - RESTRICTION TO A MINOR SUBPOPULATION, RATHER THAN A RARE EVENT

TGF-beta has the ability to transform rat fibroblasts, but it also ind uces neigbouring normal cells to eliminate newly arizing transformed c ells. Therefore, the transforming effect of TGF-beta can only be demon strated when it is added to rat fibroblasts sparsely seeded in soft ag ar. Combination of monolayer and soft agar cultures revealed the unexp ected result that transformation of rat fibroblasts by TGF-beta acts o n a distinct subpopulation rather than reaching the total population. As a consequence, the comparison of transformed cells with the parenta l untransformed random cell population is not adequate to define alter ations acquired during the transformation process.