Abstract
Basic fibroblast growth factor is an important mitogenic and angiogenic factor that stimulates endothelial cell growth and migration. This hormone is not secreted via the classical vesicular pathway, and the identification of intracellular proteins that facilitate its release remains lacking. Transfection and expression of the 27-kDa human heat shock protein in bovine arterial endothelial cells doubles the rate of estrogen-induced basic fibroblast growth factor secretion, preferentially inducing the release of high molecular weight forms of the hormone. The secreted basic fibroblast growth factor is mitogenic to breast adenocarcinoma cells cultured in the conditioned medium obtained from the transfected endothelial cells. In contrast, decreasing the level of the endogenous heat shock protein homolog with an antisense vector markedly decreases basic fibroblast growth factor release. Anti-heat shock protein or anti-basic fibroblast growth factor antibodies co-precipitate both proteins from endothelial cell extracts, demonstrating a direct association between the two proteins. This interaction is likely to be an important step in the mechanism of basic fibroblast growth factor secretion.
Highlights
Basic fibroblast growth factor is an important mitogenic and angiogenic factor that stimulates endothelial cell growth and migration
We consistently found that the culture of the HSP27 bovine arterial endothelial cells (BAECs) with the tumor cells resulted in increased tumor cell growth if -estradiol was included in the cultures
MCF-7 Growth Is Induced by bFGF in the Conditioned Media of -Estradiol-treated HSP27-expressing BAECs—To demonstrate a role for HSP27 in breast tumor angiogenesis, breast adenocarcinoma cells (MCF-7 cells) were cultured in Transwell inserts above growing BAECs
Summary
Basic fibroblast growth factor is an important mitogenic and angiogenic factor that stimulates endothelial cell growth and migration This hormone is not secreted via the classical vesicular pathway, and the identification of intracellular proteins that facilitate its release remains lacking. Transfection and expression of the 27kDa human heat shock protein in bovine arterial endothelial cells doubles the rate of estrogen-induced basic fibroblast growth factor secretion, preferentially inducing the release of high molecular weight forms of the hormone. We have demonstrated that expression of human HSP27 in bovine arterial endothelial cells (BAECs) via transfection results in a 2–3-fold enhancement in the rate of cell growth [14] These characteristics make HSP27 a likely control point in angiogenic processes where estrogens play key regulatory roles, e.g. breast tumor angiogenesis [2, 3].
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