Secretion of phosphoproteins associated with neoplastic transformation and with the action of transforming growth factors.

Incubation of conditioned media derived from mammary epithelial cells and from fibroblasts with [gamma-32P]ATP revealed much higher intensities of labeled polypeptides in transformed cells compared to normal cells. Conditioned media from human mammary carcinoma cells have in common the presence of characteristic phosphoproteins with molecular masses of about 37,22 and 19.5 kDa. Ehrlich Ascites Mammary Carcinoma Cells secrete a dominant 32 kDa phosphoprotein. Normal fibroblasts secrete elevated levels of phosphoproteins after treatment with transforming growth factors. A phosphoprotein with molecular mass of about 37 kDa becomes secreted preferentially if cell-conditioned media were labeled in vivo. The results indicate that the phosphoproteins comprise a family of secretory polypeptides associated with early steps of transformation.