Abstract 4981: Angiotensin-(1-7) targets c-Met signaling by up-regulating the phosphatase PTP1b to reduce triple negative breast cancer
Authors: Deng Guorui , Metheny-Barlow Linda , Gallagher Patricia E. , Tallant E. Ann 
Published: August 2015

Triple negative breast cancer (TNBC) is an aggressive form of breast cancer with no known targeted therapies, since the tumors cells lack expression of the estrogen receptor and do not overexpress the HER2/Neu oncoprotein. Our laboratory showed that angiotensin-(1-7) [Ang-(1-7)], an endogenous seven amino acid peptide hormone, specifically activates the G protein-coupled receptor mas to inhibit the growth of lung, breast and prostate cancer cells and tumors. Using the 4T1 syngeneic mouse TNBC model, we examined the molecular signaling involved in the anti-tumor effects of Ang-(1-7). Ang-(1-7) significantly reduced tumor volume when compared to the control group (a 46% reduction by day 18, n = 6-7, p&lt;0.05), with a concomitant decrease in tumor weight (2.0±0.3 g in untreated mice vs. 1.3±0.1 g in treated mice, p&lt;0.05). A significant reduction in the proliferation marker Ki67 was observed in tumors from Ang-(1-7)-treated mice compared to tumors from untreated mice (18.1±3.7 Ki67(+) cells vs 103.9±17.2, p&lt;0.005). Hepatocyte growth factor/scatter factor (HGF/SF) is a potent inducer of cell proliferation and cancer cell invasion by activating the receptor tyrosine kinase (RTK) c-Met and HGF/SF/c-Met signaling is elevated in TNBC. Ang-(1-7) attenuates c-Met RTK activation by HGF [phospho-c-Met(Y1234/1235)] in human MDA-MB-231 and mouse 4T1 TNBC cells by 30.3% (p&lt;0.001) and 32.1% (p&lt;0.005), respectively. The phosphatase PTP1b, a negative regulator of c-Met RTK activation, was significantly up-regulated by 75% in response to Ang-(1-7) treatment in the 4T1 cells (from 0.8±0.1 to 1.4±0.1, p&lt;0.05), suggesting that the heptapeptide hormone increases PTP1b to negatively regulate c-Met signaling. A significant decrease in immunoreactive phospho-c-Met(Y1234/1235) was also observed in 4T1 tumors treated with Ang-(1-7) as compared to untreated tumors (from 47.0 to 19.7% of field, n = 5, p&lt;0.05). The Ang-(1-7)-mediated suppression of HGF/SF-mediated c-Met activation was abrogated by D-alanine7-Ang-(1-7) [D-Ala], a mas receptor antagonist. In agreement with the Ang-(1-7)-mediated reduction of the tumor volume of 4T1 tumors, HGF-induced activation of the MAPKs ERK1 and ERK2 was reduced by the heptapeptide hormone in vitro (by 59.7 and 74.8%, respectively, n = 5). Further, Ang-(1-7) treatment significantly attenuated HGF/SF-stimulated cell invasion through Matrigel (by 53±2, n = 8, p&lt;0.05 compared to HGF/SF stimulation); this effect was abrogated by the mas receptor antagonist D-Ala. Collectively, our data suggest that Ang-(1-7) in part suppresses the progression of triple negative breast tumors by activating the mas receptor to upregulate the phosphatase PTP1b and attenuate HGF/SF-induced c-Met activation, resulting in decreased ERK1/2 signaling, reduced tumor growth and diminished cell invasion, providing support for the use of Ang-(1-7) as a novel therapeutic agent for patients with TNBC.

Citation Format: Guorui Deng, Linda Metheny-Barlow, Patricia E. Gallagher, E. Ann Tallant. Angiotensin-(1-7) targets c-Met signaling by up-regulating the phosphatase PTP1b to reduce triple negative breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4981. doi:10.1158/1538-7445.AM2015-4981