Bcl-2 overexpression and hypoxia synergistically act to modulate vascular endothelial growth factor expression and in vivo angiogenesis in a breast carcinoma line

We have previously demonstrated that bcl-2 overexpression enhances the meta static potential of the MCF7 ADIR human breast cancer cell line resistant t o adriamycin by inducing metastasis-associated properties. To further eluci date the relationship between bcl-2 expression and the metastatic potential of the MCF7 ADR line, we evaluated whether bcl-2 could be also involved in the modulation of the angiogenic phenotype. Four bcl-2-overexpressing clon es, a control transfectant clone, and the MCF7 ADR parental Line were used for in vitro and in vivo experiments. Bcl-2 overexpression enhanced the syn thesis of the hypoxia-stimulated VEGF protein and mRNA. Northern blot analy sis demonstrated an increased VEGF mRNA expression in bcl-2-overexpressing clones, and reverse transcription-polymerase chain reaction showed higher l evels of the VEGF(121) and VEGF(165) mRNA isoforms, which are the most acti ve in eliciting angiogenesis. When incorporated into matrigel, supernatants of bcl-2-transfected cells cultured under hypoxic conditions induced an in creased angiogenic response in C57BL/6 mice compared with that of control c lone. Tumors from bcl-2 transfectants demonstrated increased VEGF expressio n and neovascularization as compared to the parental line, whereas the apop tosis in in vivo xenografts was similar in control and bcl-2 transfectants. The effect of bcl-2 on angiogenesis was not mediated by p53 protein. These results demonstrate that bcl-2 and hypoxia can act synergistically to modu late VEGF expression and the in vivo angiogenic response in the MCF7 ADR li ne-Biroccio, A., Candiloro, A., Mottolese, M., Sapora, O., Albini, A., Zupi , G., Del Bufalo, D. Bcl-2 overexpression and hypoxia synergistically act t o modulate vascular endothelial growth factor expression and in vivo angiog enesis in a breast carcinoma line.