Characterization of estrogen responsive transforming activity in human breast cancer cell lines

We have characterized the production of transforming growth factor (TGF) activities by five human breast cancer cell lines in culture. The presence of TGF-alpha and -beta activity in medium conditioned by these cells was detected by induction of anchorage-independent colony formation of normal rat kidney cells in soft agar and by epidermal growth factor and TGF-beta receptor competition studies. In MCF-7, an estrogen-receptor positive cell line which requires estrogen for tumorigenesis in vivo, 17 beta-estradiol induced a 2-5-fold increase in a TGF-alpha-like activity (apparent molecular weight, 68,000 and 30,000 by column chromatography). An estrogen induction of lower magnitude (1.5-2.5-fold) was also seen in two other estrogen responsive cell lines, ZR-75-B and T47D. TGF-beta was not induced by 17 beta-estradiol in any of the three cell lines and was decreased by up to 50% of control in the MCF-7 and T47D cell lines. TGF-beta was not detectable by radioreceptor assay in the ZR-75-B cell line. Two hormone-independent and highly tumorigenic cell lines were studied. The MDA-MB-231 cell line produced large amounts of both TGF-alpha-like (Mr 30,000) and TGF-beta activities. In the HS578T cell line, little TGF-alpha was detectable, while large amounts of TGF-beta were produced. No simple correlations between the tumorigenicity of the cell lines in nude mice and production of either TGF activity could be demonstrated.