Pharmacological and endogenous progestins induce vascular endothelial growth factor expression in human breast cancer cells

Tumor expansion is dependent on angiogenesis, which is regulated by peptide growth factors of which vascular endothelial growth factor (VEGF) is one o f the most selective and potent. VEGF expression is regulated by steroid ho rmones in a number of systems, including T47-D human breast cancer cells in which VEGF protein levels are elevated by progestins. In the present study , we investigated the effect of progestins on VEGF mRNA levels in human bre ast cancer cells. For these experiments, T47-D cells were exposed to proges tins, RNA was prepared for measurement of VEGF transcript levels by Norther n blot analysis and VEGF protein in the cell culture media was measured by enzyme-linked immunosorbent assay, Basal expression of VEGF mRNA is low in these cells, and is rapidly induced following exposure to progestins, reach ing a maximum induction of 2- to 5-fold between 3 and 6 hr after hormone ad dition, This induction was inhibited by the antiprogestin RU-486 indicating that it is progesterone receptor (PR) dependent. Transcripts for VEGF,,, a nd VEGF,,, were the two major spliced forms of VEGF mRNA that were detected by reverse transcription-polymerase chain reaction in basal and progestin stimulated T47-D cells. Maximum induction of VEGF mRNA was achieved with 10 (-8) M progesterone, and induction was hormone specific, as estrogens, gluc ocorticoids, and androgens were without effect, Actinomycin D completely ab olished the induction of VEGF transcript levels by progestins, suggesting t hat this response involves de novo mRNA synthesis, but puromycin did not in hibit induction, suggesting that this effect does not require protein synth esis, This report demonstrates that progestins stimulate VEGF mRNA levels a nd raises the possibility that anti-progestins may be useful to inhibit pro liferation and metastasis in some human breast cancers by blocking VEGF pro duction. (C) 2001 Wiley-Liss, Inc.