MDA-MB-231 breast cancer cells overexpressing single VEGF isoforms display distinct colonisation characteristics.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a multifunctional cytokine that has important roles in angiogenesis. Our knowledge of the significance of VEGF isoforms in human cancer remains incomplete. METHODS: Bioluminescence imaging and transcriptomic analysis were used to study the colonisation capacity of the human breast cancer cells MDA-MB-231 controlling or overexpressing the VEGF165 or VEGF189 isoform (named cV-B, V165-B and V189-B, respectively) in nude mice. RESULTS: When injected into the bloodstream, V189-B cells induced less metastasis in the lungs and bone than V165-B and cV-B control cells, consistent with longer survival of these mice and delay in tumour uptake in the mice injected with a V189-B clone. Histological analysis confirmed that there were less αSMA-positive cells in the lungs of the mice injected with V189-B. In vitro V189-B cells decreased both cell invasion and survival. Using transcriptomic analysis, we identified a subset of 18 genes expressed differentially between V189 and V165 cell lines and in 120 human breast tumours. V165 was associated with poor prognosis, whereas V189 was not, suggesting a complex regulation by VEGF isoforms. Our results showed a negative correlation between the expression pattern of VEGF189 and the levels of expression of seven genes that influence metastasis. CONCLUSION: Our findings provide the first evidence that VEGF isoforms have different effects on breast cancer cell line colonisation in vivo.

Overexpression of VEGF189 in breast cancer cells induces apoptosis via NRP1 under stress conditions.

The existence of multiple VEGF-A isoforms raised the possibility that they may have distinct functions in tumor growth. We have previously published that VEGF189 and VEGF165 contribute to breast cancer progression and angiogenesis, but VEGF165 induced the most rapid tumor uptake. Since VEGF165 has been described as a survival factor for breast tumor cells, we questioned here the effects of VEGF189 on the survival/apoptosis of MDA-MB-231 cells. We used clones which overexpress VEGF189 (V189) or VEGF165 (V165) isoforms and compared them to a control one (cV). Overexpression of VEGF189 resulted in increased cell apoptosis, as determined by Annexin-V apoptosis assay, under serum starvation and doxorubicin treatment, while VEGF 165 was confirmed to be a survival factor. Since MDA-MB-231 highly express NRP1 (a co-receptor for VEGF-A), we used short hairpin RNA (shRNA) to knockdown NRP1 expression. V189shNRP1 clones were characterized by reduced apoptosis and higher necrosis, as compared to V189shCtl, under stress conditions. Unexpectedly, NRP1 knock-down had no effect on the survival or apoptosis of V165 cells. VEGF189 showed greater affinity towards NRP1 than VEGF165 using a BIAcore binding assay. Finally, since endogenously produced urokinase-type plasminogen (uPA) has been found to prevent apoptosis in breast cancers, we analyzed the level of uPA activity in our clones. An inhibition of uPA activity was observed in V189shNRP1 clones. Altogether, these results suggest a major role of NRP1 in apoptosis induced by VEGF189 in stress conditions and confirm VEGF165 as a survival factor.

Vascular endothelial growth factor is a target gene for estrogen receptor and contributes to breast cancer progression.

Tumor growth requires the development and remodeling of the vascular system, involving paracrine signaling between various growth factors and endothelial receptors. Vascular endothelial growth factor (VEGF) is a key regulator of developmental, physiological and pathological neovascularization, especially involved in tumor growth. Recent studies indicate that 17beta-estradiol (E2) modulates VEGF expression in breast cancer cells through transcriptional activation. We have investigated both the molecular mechanisms of E2-induction of VEGF expression and of VEGF control of breast cancer angiogenesis. In transient transfection assays using the VEGF promoter-luciferase construct, E2 increased VEGF transcriptional activity in MCF-7 cells and in MDA-MB-231 cotransfected with estrogen receptor (ERalpha or ERbeta). The positive effect was abolished when MCF-7 cells were treated with the pure antiestrogen ICI 182,780 or the agonist/antagonist tamoxifen. We further identified an imperfect estrogen responsive element (ERE1520) in the VEGF promoter, which formed a complex with ERalpha or ERbeta proteins in gel shift assay using MCF-7 or MDA-MB-231 nuclear extracts; the ERE sequence is involved in the transcriptional regulation of VEGF in our experimental conditions. These results demonstrate that in breast cancer (BC) cells VEGF is a target gene for ERalpha or ERbeta. To determine the role of VEGF in the progression of human breast carcinoma, we generated stable human breast carcinoma cells (MCF-7) overexpressing VEGF165 (V165 clones). Cells or control vector clones were implanted subcutaneously in athymic mice. Our in vivo findings show that overexpression of VEGF significantly decreased tumor uptake and increased tumor growth and angiogenesis in a murine model of BC.

Xenoestrogens modulate vascular endothelial growth factor secretion in breast cancer cells through an estrogen receptor-dependent mechanism.

Environmental chemicals may affect human health by disrupting endocrine function. Their possible role in the mammary gland and breast tumors is still unknown. Previous studies have demonstrated that vascular endothelial growth factor (VEGF), a key factor in angiogenesis and tumor progression, is an estrogen-regulated gene. We analyzed whether VEGF expression is regulated by different xenoestrogens in several breast cancer cells, MELN (derived from MCF-7) and MELP (derived from MDA-MB-231) and stably expressing estrogen receptor alpha (ERalpha); these cell lines stably express estrogen response element (beta-globin)-luciferase. Genistein, bisphenol A (BPA), 4-(tert-octyl)phenol (OP), dieldrin, and several phthalates, including benzyl butyl phthalate (BBP) and di-ethyl-2-hexyle phthalate (DEHP), were first shown to be estrogenic. These compounds induced a dose-dependent increase of VEGF secretion in MELN and MCF-7 cells; maximal effect was observed at 1-10 microM non-cytotoxic concentrations and was inhibited by the antiestrogen ICI 182 780. VEGF increase was not observed in ERalpha-negative MDA-MB-231 cells. Most substances increased VEGF transcript levels in MELN cells. In contrast, gamma-hexachlorocyclohexane, vinclozolin, and the phthalates (mono-n-butyl ester phthalic acid, di-isononyle phthalate, and di-isodecyle phthalate) were ineffective on both VEGF secretion and estrogenic luciferase induction in these cell lines. Specific kinase inhibitors PD98059, SB203580, or LY294002 suppressed the xenoestrogen-induced VEGF response, suggesting activation of MEK, p38 kinase, and phosphatidylinositol-3-kinase pathways. Our in vitro results show for the first time that genistein and xenoestrogens (BPA, OP, dieldrin, BBP, and DEHP at high concentrations) up-regulate VEGF expression in MELN cells by an ER-dependent mechanism. Since VEGF increases capillary permeability and breast tumor angiogenesis in vivo, the physiological relevance of these findings is discussed.

Overexpression of vascular endothelial growth factor 189 in breast cancer cells leads to delayed tumor uptake with dilated intratumoral vessels.

Vascular endothelial growth factor (VEGF) is essential for breast cancer progression and is a relevant target in anti-angiogenesis. Although VEGF121 and VEGF165, the fully or partially secreted isoforms, respectively, have been the focus of intense studies, the role of the cell-associated VEGF189 isoform is not understood. To clarify the contribution of VEGF189 to human mammary carcinogenesis, we established several clones of MDA-MB-231 cells stably overexpressing VEGF189 (V189) and VEGF165 (V165). V189 and V165 clones increased tumor growth and angiogenesis in vivo. Remarkably, V165 induced the most rapid tumor uptake, whereas V189 increased vasodilation. In vitro overexpression of VEGF165 and VEGF189 increases the proliferation and chemokinesis of these cancer cells. Interestingly, overexpression of VEGF189 increased cell adhesion on fibronectin (1.9-fold) and vitronectin (1.6-fold), as compared to VEGF165, through alpha5beta1 and alphavbeta5 integrins. Using the BIACore system we demonstrated for the first time that VEGF189 binds directly to neuropilin-1, which is strongly expressed in MDA-MB-231 cells. In contrast, VEGF-R2 was not significantly expressed and VEGF-R1 was expressed at low level. Our in vitro results suggest an autocrine effect of VEGF189 on breast cancer cells, probably through neuropilin-1. In conclusion, our data indicate that VEGF189 participates in mammary tumor growth through both angiogenesis and nonangiogenic functions. Whether VEGF189 overexpression is correlated to prognosis in human breast tumors remains to be established.

VEGF189 stimulates endothelial cells proliferation and migration in vitro and up-regulates the expression of Flk-1/KDR mRNA.

The vascular endothelial growth factor (VEGF) is a critical factor for development of the vascular system in physiological and pathological angiogenesis. This growth factor exists under at least three isoforms, VEGF120/121, VEGF164/165 and VEGF188/189 which are generated by alternative splicing. VEGF isoforms have different affinities for heparan sulphate as well as for VEGF receptors, and may play distinct roles in vascular development. The role of VEGF189 as an endothelial mitogen, however, remains controversial. VEGF189 is almost entirely bound to the cell surface or extracellular matrix, and is considered active after its cleavage and release from its extracellular binding site. In the present study, we demonstrate that VEGF189 induces endothelial cell proliferation and migration in vitro. The 30-60% increase observed with VEGF189 (10 ng/ml) in HUVEC proliferation was similar to that observed with VEGF165. However, the proliferative effect observed with VEGF189 appeared dependent on the origin of the endothelial cell, since the proliferation was clearly observed with HUVEC but not with BAEC or capillary endothelial cells from dermis (HMEC). The effect of VEGF189 on endothelial cell migration was also analyzed using the wound healing and the Boyden chamber assays. The migration effect was observed with BAEC which do not proliferate with VEGF189, suggesting that different mechanisms are involved in proliferation and migration. In addition, VEGF189 as well as VEGF165 induced a 2-fold increase of Flk-1/KDR expression in HUVEC, the receptor involved in proliferation and migration of endothelial cells. In the Matrigel plug assay in vivo, both VEGF189 and 165 (100 ng/ml) increased the infiltration of endothelial cells. These data suggest that VEGF189 induced endothelial cell migration and proliferation under certain circumstances.

Transcriptional regulation of vascular endothelial growth factor by estradiol and tamoxifen in breast cancer cells: a complex interplay between estrogen receptors alpha and beta.

Vascular endothelial growth factor (VEGF) is a potent angiogenic and prognostic factor for many tumors, including those of endocrine-responsive tissues such as the breast and uterus. Recent studies indicate that 17beta-estradiol (E(2)) modulates VEGF expression in breast and uterine cells, involving transcriptional activation through estrogen receptor (ER) alpha. However, molecular mechanisms of VEGF regulation mediated by the two ER subtypes and the potential role of ERbeta in the control of breast cancer angiogenesis have not yet been investigated. In transient transfection assays using the VEGF(-2275/+54) promoter-luciferase construct, E(2) (1 nM) increased transcription activity in MCF-7 cells (either untransfected or cotransfected with ERalpha) and it increased transcription activity in MDA-MB-231 cells cotransfected with ERalpha or ERbeta (1.8- and 2-fold induction, respectively). The positive effect was abolished when MCF-7 cells were treated with pure antiestrogen ICI 182,780 or the agonist/antagonist tamoxifen (1 micro M). To identify response elements involved in this transcriptional regulation, MCF-7 or MDA-MB-231 cells were transfected with several deletion constructs of the VEGF promoter. Deletion of 1.2-2.3 kb upstream to the transcription start in the VEGF promoter abrogated E(2)-dependent transcription in these cells. This region contains an imperfect estrogen-responsive element (ERE), ERE1520, and one activator protein 1 site. Transfection of MCF-7 cells (ERalpha) with the ERE1520-luciferase construct conferred transcriptional activity with 1 nM E(2) (1.9-fold induction). Also, the imperfect ERE formed a complex with ERalpha or ERbeta proteins in gel shift assay using MCF-7 or MDA-MB-231 nuclear extracts. In contrast to ERalpha, ERbeta could transactivate VEGF reporter construct in MDA-MB-231 cells, in the presence of E(2) or tamoxifen, suggesting different transactivational mechanisms between ERalpha and ERbeta in the presence of tamoxifen. Interestingly, E(2) inhibited VEGF transcription in MCF-7 cells transfected with ERbeta or MDA-MB-231 cells cotransfected with ERalpha and ERbeta, suggesting that heterodimerization of ERalpha/ERbeta has the ability to inhibit E(2)-induced VEGF expression in breast cancer cells. These results demonstrate that VEGF is a target gene for ERalpha and ERbeta in breast cancer cells; it remains to be determined whether ERalpha and ERbeta expression in breast biopsies correlates with VEGF expression and vascular density.

A dynamic shift of VEGF isoforms with a transient and selective progesterone-induced expression of VEGF189 regulates angiogenesis and vascular permeability in human uterus.

A key mechanism underlying physiological angiogenesis of the human endometrium is its ability to regenerate the vascular capillary network and to perform vascular remodeling (i.e., development of spiral arteries). Vascular endothelial growth factor (VEGF) is associated with angiogenesis and capillary permeability in this tissue. VEGF is expressed as several spliced variants, its main human isoforms contain 121 and 165 aa; 17beta-estradiol (E(2)) increases endometrial VEGF, possibly in all isoforms. Here we show that progesterone (P) selectively increases the expression of the VEGF(189) (V(189)) isoform in the human uterus. V(189) is identified in the conditioned medium of stromal cells treated with E(2) + P; its presence in this in vitro model of decidual stromal cells is detected after 6-8 days, using ELISA, and after 8-10 days, using Western blot analysis with different antibodies, including one specific for V(189). The secretion pattern of V(189) parallels that of the decidual protein IGFBP-1. V(189) is secreted as a native isoform, as compared with the migration of recombinant V(189) by SDS/PAGE. In situ hybridization and immunocytochemistry(,) performed on the same biopsies, suggest that decidual cells express V(189) during the mid-late secretory phase of the menstrual cycle and early gestation. Finally, using an in vivo permeability assay, we show that native V(189) increases capillary permeability. These observations demonstrate that P regulates V(189) expression in decidual cells, which could have important implications for understanding uterine vascular remodeling and implantation, and may be relevant in a range of disease states such as edema and irregular bleeding.