VASCULAR ENDOTHELIAL GROWTH-FACTOR IS INDUCED IN RESPONSE TO TRANSFORMING GROWTH-FACTOR-BETA IN FIBROBLASTIC AND EPITHELIAL-CELLS

Transforming growth factor beta (TGF-beta) is a multifunctional polypeptide that regulates the proliferation and differentiation of various cells and has an angiogenic effect in vivo although it inhibits the growth of cultured endothelial cells. We report here that TGF-beta treatment of quiescent cultures of mouse embryo-derived AKR-2B cells, which are growth-stimulated by TGF-beta, and human lung adenocarcinoma A549 cells, which are growth-inhibited by TGF-beta, results in the induction of vascular endothelial growth factor (VEGF) mRNA and protein. Maximal VEGF mRNA levels occurred 4-8 h after stimulation with a decline to background levels in 24 h. In contrast, the related placenta growth factor mRNA was not induced by TGF-beta in these cells. No VEGF receptor mRNA was seen in AKR SB cells. Also, TGF-beta treatment of endothelial cells, which express the FLT1 and KDR/FLK-1 receptors for VEGF, did not cause VEGF induction. Because VEGF is known to be a strong angiogenic factor for endothelial cells, the results suggest that the angiogenic effect of TGF-beta on endothelial cells in blood vessels may be mediated at least partly by a paracrine induction of VEGF in other surrounding cell types.