Abstract 4048: GFRα1 is required for GDNF-induced viability, migration, and signaling through RET in breast cancer cells

Abstract

Abstract Hormone resistance is a major challenge in treating breast cancer patients. Although anti-estrogens, such as tamoxifen, are initially successful controlling disease in estrogen receptor alpha positive (ERα+) tumors, patients with metastatic disease and as many as 40 % of patients receiving adjuvant tamoxifen acquire resistance to treatment, relapse, and die. The receptor tyrosine kinase, RET, its co-receptor, GFRα1, and their ligand, GDNF, are proteins that are emerging as potential contributors to hormone resistance in breast cancer. RET and GFRα1 were recently shown to be overexpressed in a subset of ERα+ breast cancer tumors, and GFRα1 expression was associated with lymphovascular invasion. In vitro, silencing RET with siRNA increased MCF7 cells' sensitivity to tamoxifen and, in the absence of estrogens, treatment of MCF7 cells with GDNF induced upregulation of ERα target genes. Additionally, GDNF stimulation of MCF7 cells enhanced proliferation, survival, and cell scattering. Together, clinical and preclinical data suggest that this pathway plays an important role in driving breast cancer invasion, metastasis, and hormone resistance. However, the role of GFRα1 has not been examined in tumor cell invasion and metastasis. In this study we tested the functional consequences of silencing GFRα1 in ERα + MCF7 cells on tumor cell migration, invasion, and RET signaling. We showed that targeted reduction of GFRα1 significantly inhibited GDNF-induced migration in both a transwell (p=<0.001) and scratch wound assay (p=<0.001 at 24 hours). In addition, GDNF-induced increases in viability were significantly decreased when MCF7 cells were treated with neutralizing antibodies against GFRα1 (p=<0.001). Silencing GFRα1 in GDNF-treated MCF7 cells led to reduced invasion through collagen I, although this difference was not significant. Lastly, siRNA targeted reduction of GFRα1 in MCF7 cells inhibited GDNF-induced phosphorylation of RET. Together the data demonstrate that GFRα1 is important in migration and cell viability as well as RET signaling in breast cancer cells. Citation Format: Catherine A. Ferrante, Nikki DeAngelis, Raluca Verona. GFRα1 is required for GDNF-induced viability, migration, and signaling through RET in breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4048. doi:10.1158/1538-7445.AM2014-4048