Stimulation by insulin-like growth factors is required for cellular transformation by type beta transforming growth factor.

摘要: Medium conditioned by BRL-3A cells, a known source of insulin-like growth factor II (IGF-II), induced phenotypic transformation (anchorage-independent proliferation) mouse BALB/c 3T3 fibroblasts but not rat NRK-49F fibroblasts, in the presence 10% calf serum. A specific radioreceptor assay and bioassay indicated that medium contained 0.5-1 ng/ml type beta transforming (beta TGF). Purified IGF-II TGF acting together reconstituted activity on cells. Insulin was 5-10% as potent supporting action cells were phenotypically transformed EGF serum sole IGFs. However, under these conditions inhibited addition purified IGF-binding protein. Addition an excess prevented inhibitory The different sensitivity two cell lines to IGFs correlated with lower levels I IGF receptor higher compared results suggest cellular stimulation is prerequisite for rodent TGF. We propose requires concomitant set factors support normal proliferation.