Vascular endothelial growth factors are differentially regulated by steroid hormones and antiestrogens in breast cancer cells

Vascular endothelial growth factor (VEGF) is a major inducer of tumor angio genesis and an important prognostic factor in breast cancer. Hypoxia is an important inducer of VEGF expression but less is known of the role of hormo nes in VEGF regulation. We have studied the regulation of VEGF, VEGF-B, VEG F-C, and VEGF-D mRNAs in human MCF-7 and mouse S115 breast carcinoma cells stimulated by estrogens and androgens, respectively. VEGF, VEGF-B, and VEGF -C were expressed in both cell lines, whereas VEGF-D was expressed only in S115 cells. Addition of estradiol (E-2) caused a biphasic increase of VEGF mRNA in MCF-7 cells and led to accumulation of the VEGF protein in the cult ure medium. The VEGF-B mRNA was not affected, while a decrease occurred in VEGF-C mRNA. Similarly, testosterone upregulated the expression of VEGF mRN A in the S115 cells. Experiments with actinomycin D and cycloheximide sugge sted that estrogen induction of VEGF mRNA is dependent on the synthesis of new mRNA and increased mRNA half-life. The antiestrogen ICI 182.780 inhibit ed E-2 stimulation of VEGF, suggesting that the effect was mediated by the estrogen receptor. In contrast, the antiestrogens tamoxifen and toremifene which inhibit MCF-7 cell growth in vivo and in vitro did not inhibit estrog en effect but induced VEGF mRNA expression when used alone. The antiandroge n cyprosterone acetate inhibited T induction of VEGF mRNA in S115 cells, th us suggesting that activation of androgen receptor must be involved in the increase of VEGF mRNA. Our results suggest that both estrogen and androgen stimulate the expression of VEGF by, increasing gene transcription and mRNA stability. In addition, the antiestrogens tamoxifen and toremifene also in creased VEGF expression. Estrogen and androgen induction of VEGF expression and promotion of new vessel formation may be an important paracrine mechan ism by which these hormones contribute to the early phase of tumor growth o f hormonal cancer. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.