TRANSFORMING GROWTH-FACTOR PRODUCTION BY CHEMICALLY TRANSFORMED-CELLS

Abstract

The chemically transformed AKR-MCA and C3H/MCA-58 murine cell lines produce transforming growth factor(s) capable of inducing a transformed morphology and the ability to grow in soft agar in nontransformed, anchorage-dependent indicator cells. Serum-free medium conditioned by exposure to the chemically transformed cells was chromatographed on a Bio-Gel P-60 column after dialysis and lyophilization. Using the nontransformed mouse AKR-2B cells as the indicator cells, a peak of soft agar growth-stimulating activity was detected in the MW range of 10,000-12,000. The soft agar growth-stimulating activity in pooled fractions from the AKR-MCA cells was trypsin and dithiothreitol sensitive and relatively heat stable; the activity was not destroyed by heating to 56.degree. C for 30 min or to 100.degree. C for 3 min. The pooled material stimulated growth in the soft agar of rat NRK cells and stimulated DNA synthesis in the AKR-2B cells. The quantity required to give significant competition for binding to the epidermal growth factor receptor was .apprx. 1 order of magnitude greater than that required for stimulation of soft agar growth. Further separation of these polypeptide(s) by carboxymethylcellulose chromatography revealed 3 apparent peaks of soft agar growth-stimulating activity. Epidermal growth factor receptor-competing activity cochromatographed with the early minor soft agar growth-stimulating peak; the 2 major peaks of soft agar growth-stimulating activity had no associated detectable competition for epidermal growth factor binding to its receptor. At least a major portion of the transforming growth factors produced by the chemically transformed cells is different from those described previously in murine sarcoma virus-transformed mouse cells and human tumor cells.