Growth factor production by a human megakaryocytic tumor cell line.

A recently described human megakaryocytic tumor cell line was analyzed for the presence of growth factor activity and was found to produce large quantities of transforming growth factor beta-like (TGF-beta) and basic fibroblast growth factor-like (bFGF) activities. Growth factor activities were identified using a radioreceptor assay for the TGF-beta-like activity, a heparin-binding assay for the b-FGF-like activity, and a demonstration of distinct biological activities for each type of factor. Tumor poly-A+ RNA revealed strong signals when probed with complementary DNA corresponding to bovine basic FGF and human TGF-beta and weak signals when probed with cDNA corresponding to epidermal growth factor (EGF) and TGF-alpha. The levels of EGF and TGF-alpha produced in the tumor line were too low to be detected by radioreceptor assays. Relative levels of messenger RNA encoding each of the growth factors reflected the relative levels of each of the respective factors tested. These data represent the first definitive identification of FGF-like activities in megakaryocytic-like cell lines. Interestingly, the line displayed little activity similar to platelet-derived growth factor (PDGF) when assayed either biochemically or by poly-A+ RNA analysis.