부산대학교 도서관

Purified type β transforming growth factor from human platelets (TGFβ ) radioiodinated with 125 I-labeled Bolton and Hunter reagent was found to bind to a variety of cultured cells of both epithelial and mesenchymal origin, including normal human fibroblasts and keratinocytes. TGFβ binding sites have also been found on three mouse embryo-derived fibroblast-like cell lines with lower levels of TGFβ binding on the chemically transformed derivatives of these cell lines. A variety of human tumor cell lines was shown to have an inverse correlation between their level of TGFβ binding and their ability to form colonies in soft agar. The mouse embryo-derived AKR-2B (clone 84A) cells reached maximal binding of 125 I-labeled TGFβ after 2 hr at 22 degrees C. Scatchard analysis of the equilibrium binding of TGFβ to AKR-2B (clone 84A) cells gives a K d of 33 pM with ≈ 10,500 binding sites per cell. This K d for TGFβ binding to AKR-2B (clone 84A) cells agreed well with the ED 50 of 40 pM for stimulation of colony formation of these cells by TGFβ . The TGFβ binding sites on the AKR-2B cells were shown to be specific for TGFβ with no significant competition with epidermal growth factor, fibroblast growth factor, or insulin and only a small level of competition with high concentrations of platelet-derived growth factor. Partially purified preparations with TGFβ -like activity from mouse embryos and medium conditioned by mouse embryo-derived cells competed effectively for binding to the TGFβ receptor.