Unusual antiproliferative effects of transforming growth factors-β 1 andβ 2 against primary cells from human tumors

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Abstract
Transforming growth factorsβ 1 andβ2 (TGF-β1 andβ2), tested in a clonogenic assay against primary cells from human tumors, suppress proliferation to different extents. In nineteen of twenty-six cell cultures, proliferation was < 50% of control with factor at 0.04 or 0.4 nM. Of these, TGF-β 2 was more active than TGF-β1 in fourteen; and TGF-β1 was more active than TGF-β2 in five. In seven of the nineteen, proliferation was 0% with one or the other factor. In contrast, cisplatin was much less effective in inhibiting proliferation of some of the same cells even at 1,000 or more times the molar concentration of the factors. Surprisingly, when TGF-β 1 and TGF-β2 were combined at equal concentrations, the antiproliferative effect of one was cancelled or markedly inhibited by the other.