In vitro effects of bone- and platelet-derived transforming growth factor-β on the growth of Walker 256 carcinosarcoma cells

Conditioned media from fetal rat calvarial cultures has previously been shown to stimulate the growth of the bone-metastasizing Walker 256 carcinosarcoma cell line. In the current investigation we looked at the possibility that transforming growth factor-β (TGF-β), present in conditioned media, and positively correlated with resorption in vitro, may be responsible for the enhanced proliferation of Walker cells cultured in these conditioned media. Purified platelet-derived TGF-β produced a dose-dependent growth response in Walker cells with an ED50 equal to 0·05 ng/ml. Bone-derived TGF-β activity in conditioned media, measured by NRK fibroblast colony formation, correlated well with percentage resorption in bone cultures, and growth activity in Walker cell culture. In addition to this, the growth response normally seen with conditioned media cultures of Walker cells was significantly inhibited by the addition of anti-TGF-β1 neutralizing antibody. We conclude that TGF-β is an important growth stimulatory component from fetal rat calvaria.