Abstract 2273: Angiotensin-(1-7) reduces angiogenesis and fibrosis in orthotopic breast cancer

Abstract

Abstract Angiotensin-(1-7) [Ang-(1-7)] is an endogenous seven-amino acid peptide hormone of the renin-angiotensin system with anti-proliferative properties. We previously showed that Ang-(1-7) significantly inhibited the growth of non-small cell lung adenocarcinoma in a xenograft mouse model in association with a reduction in angiogenesis. In a recently completed Phase I clinical trial conducted in the Wake Forest University Comprehensive Cancer Center, we reported that Ang-(1-7) significantly reduced the pro-angiogenic factor placental growth factor (PlGF) in four patients who had stable disease for greater than 3 months, suggesting that Ang-(1-7) is a novel anti-angiogenic drug for the treatment of cancer. In this study, BT-474 human epidermal growth factor receptor 2 (HER2) over-expressed, estrogen receptor (ER) positive breast cancer cells or ZR-75-1 ER positive breast cancer cells were injected into mammary fat pads of athymic mice and treated with Ang-(1-7), to determine the effect of the drug on breast cancer. After the tumors grew to 100-200 mm3, mice were treated with either saline or 24 µg/kg/h Ang-(1-7) for 18 days. Treatment with Ang-(1-7) reduced tumor volume (68.2% in BT-474 tumors and 77.0% in ZR-75-1 tumors) and tumor weight (38.9% in BT-474 tumors and 50% in ZR-75-1 tumors), indicating that the heptapeptide inhibits breast tumor growth. Vessel density was also decreased 50% by the heptapeptide, demonstrating that Ang-(1-7) reduced angiogenesis in breast tumors. Tumoral fibrosis, measured by picrosirius red collagen staining, was attenuated in Ang-(1-7)-treated breast tumors. The heptapeptide reduced interstitial fibrosis from 4.91 ± 0.96%/field to 1.2 ± 0.2 in BT474 tumors and from 23.3 ± 2.4%/field to 8.3 ± 0.8 in ZR-75-1 tumors, in association with a 66% reduction in collagen I deposition. Treatment with Ang-(1-7) also reduced perivascular fibrosis in BT-474 tumors, from 49.3 ± 3.2% fibrosis/vessel to 13.4 ± 2.2% fibrosis/vessel. Ang-(1-7) markedly attenuated the in vitro growth of fibroblasts isolated from orthotopic breast tumors. Treatment of tumoral fibroblasts with Ang-(1-7) reduced fibronectin protein by 40%, in association with a 50% decrease in transforming growth factor-β (TGF-β). Ang-(1-7) also caused a 2-fold increase in the mitogen-activated protein (MAP) kinase phosphatase DUSP1, with an associated 50% decrease in MAP kinase ERK1 and ERK2 activities, suggesting that the heptapeptide increases DUSP1 to reduce MAP kinase signaling. This is the first report that Ang-(1-7) targets the tumor microenvironment, by inhibiting the growth of tumor-associated fibroblasts to reduce fibrosis. Collectively, these results suggest that Ang-(1-7) may serve as a first-in-class chemotherapeutic agent for breast cancer, targeting the tumor microenvironment through a reduction in angiogenesis and a decrease in tumor fibrosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2273.