Immunological detection and quantitation of alpha transforming growth factors in human breast carcinoma cells

Summary Alpha transforming growth factors (TGFs) were immunologically detected in the concentrated conditioned medium (CM) prepared from four human breast cancer cell lines and from primary cultures of human mammary epithelial cells, and in the tissue extracts prepared from normal, benign, and malignant breast biopsies. Immunoreactive TGFs were quantitated by a competitive radioimmunoassay (RIA) using affinity-purified polyclonal sheep anti-rat TGF antibodies which react with human TGF but not with human epidermal growth factor (EGF). The relative level of RIA-detectable TGFs in the CM from the breast cancer cell lines MCF-7, ZR-75-1, T47-D, and MDA-MB-231, and from the CM of primary cultures of human mammary epithelial cells, ranged from 0.02 to 0.85 ng/ml. MCF-7 or ZR-75-1 cells grown in the presence of 17-estradiol (10^–8 M) for 48 h were found to release two- to three-fold more TGFs into their CM than the same cells grown in the absence of estrogen. In detergent extracts prepared from normal breast tissue, a benign fibrocystic lesion, fibroadenomas and primary breast carcinomas, the relative TGF concentrations were found to range from 1.5 to 6 ng/mg cell protein. No significant correlations were found between the TGF levels and the pathological state of the tissues, the estrogen receptor status of the tumors, or the relative amounts of theras gene protein p21ras in the tissues as determined by Western immunoblot analysis. The question of biological relevancy of TGF for human mammary tumors will require further studies on (a) synthesis and turnover of TGF, (b) the relationship between immunoreactivity and biological activity of TGF, and (c) differences in biological responsiveness of mammary tumor cells.