Using conditioned media from both tumor cells and CAFs, we determined the effects of secreted factors on proliferation of MDA-MB-435 cells with intact TGF-β1 expression or clonal derivatives of the parental MDA-MB-435 cell line, abrogated in TGF-β1 expression using stable shRNA transfection (MDA-MB-435TGFβsi; 31). The gene discussed is TGFB1; the disease is neoplasm.