Abstract 1580: Molecular mechanisms of OSM-induced VEGF in breast cancer

Abstract

Abstract Oncostatin M (OSM) is an interleukin-6 (IL-6) family cytokine that has been shown to induce expression of vascular endothelial growth factor (VEGF) in astroglioma and in hepatocellular and breast carcinoma. It is also known to induce VEGF in non-cancerous cells such as cardiac myocytes, hepatocytes, and smooth muscle cells. Under hypoxic conditions, VEGF expression is known to be dependent on the transcription factor hypoxia-inducible factor 1 alpha (HIF1α). Our current studies were designed to determine whether VEGF expression induced by OSM and other IL-6 family members, including IL-6 and leukemia inhibitory factor (LIF), is likewise dependent on HIF1α in human breast cancer cells. To analyze VEGF expression levels, MDA-MB-231 and T47D human breast cancer cells were cultured in the presence or absence of OSM, IL-6, and LIF, with or without a HIF1α siRNA, for 12 to 72 hrs. All three cytokines significantly induced HIF1α expression by Western blot analysis at each time point in both MDA-MD-231 and T47D cells. Conditioned media from these experiments was also analyzed using ELISA to determine HIF1α-induced VEGF expression. Treatment with OSM resulted in a two- to three-fold induction of secreted VEGF, while treatment with IL-6 and LIF showed no significant induction. In addition, OSM-induced VEGF expression was independent of HIF1α in MDA-MB-231 cells. This was indicated by unchanged secreted VEGF levels despite the reduction of HIF1α expression in siRNA treated groups. In T47D cells however, HIF1α siRNA-treatment for 72 hrs reduced VEGF levels by 40% suggesting that OSM-induced HIF1α may be partially responsible for VEGF expression in this cell line. To summarize, it is important to note that IL-6 and LIF did not induce VEGF expression in two commonly used human breast cancer cell lines, MDA-MB-231 and T47D. Furthermore, OSM-induced VEGF was not dependent on HIF1α in MDA-MB-231 cells, suggesting regulation of VEGF by an alternative molecular mechanism. Investigations are in progress to better understand mechanisms utilized by breast cancer cells for OSM-induced VEGF expression. Future results could lead to the potential design of OSM-targeted therapeutics. Funded by NIH R15CA137510, ACS RSG-09-276-01-CSM, Susan G. Komen for the Cure KG100513, and NIH/NCRR P20RR016454. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1580. doi:10.1158/1538-7445.AM2011-1580