TRANSFORMATION OF MURINE FIBROBLASTS BY UV-LIGHT AND TGF-BETA - ESTABLISHMENT OF AN AUTOCRINE TGF-BETA LOOP

Murine fibroblasts stably transformed by initiation with UV light and tumor promotion with TGF-beta form colonies in soft agar, exhibit a di ffuse actin pattern and induce angiogenesis. They differ from their pa rental cells by their ability to release active TGF and to react to TG F-beta by increased colony formation. Antibodies directed against TGF- beta abrogate the transformed phenotype, indicating the action of an a utocrine TGF-beta loop for the maintenance of the transformed state. H owever, TGF-beta which is responsible for the maintenance of the trans formed state, proves to be a severe obstacle for the survival of trans formed cells which are cocultivated with normal cells.