Abstract 503: Mammary fibroblasts induce hormone-independent growth in estrogen receptor-positive breast cancer cells via an epithelial-to-mesenchymal transition in a 3D cell culture model.

Abstract

Abstract The majority of breast cancers diagnosed in the United States are estrogen receptor positive (ER+). These patients may respond to targeted endocrine therapies, but up to 30% of patients experience a cancer recurrence. We hypothesized that the molecular interaction of ER+ breast cancer cells with mammary fibroblasts might lead to endocrine resistance and, eventually, breast cancer relapse. We developed a three-dimensional (3D) co-culture model representing cancer cell-fibroblast interactions during early tumor invasion. We show that the proliferation of MCF7 ER+ cells switches from hormone-dependent to growth factor-dependent in the presence of human mammary fibroblasts. Further, we determine that this transition is associated with gene and protein hallmarks of the epithelial-mesenchymal transition (EMT) in tumor cells, in particular upregulation of SNAIL and SLUG mRNA and loss of E-Cadherin protein. We identified the secreted proteins that arise from epithelial-fibroblast interactions in this system using an antibody-based array. The proteins secreted into the conditioned medium are sufficient to induce EMT markers in primary normal human mammary epithelial cells (HMECs). Our report demonstrates that estrogen receptor activity is dynamic and therefore is not best assessed with immunohistochemical techniques alone. For the facile and rapid determination of ER activity in a clinical setting, we propose the use of an emerging imaging method, highly sensitive label-free Fourier Transform infrared (FT-IR) spectroscopic imaging. We validate this technology in predicting endocrine sensitivity in breast cancer here, by detecting significant changes in spectroscopic peaks correlated with proliferation and metabolism of MCF7 cells grown in 3D culture. (Supported by grants from The Breast Cancer Research Foundation to BSK, DOD postdoctoral fellowship W81XWH-09-1-0398 to AB, NIH NCI Alliance for Nanotechnology in Cancer ‘Midwest Cancer Nanotechnology Training Center R25 CA154015A to SEH, and National Institutes of Health RO1CA138882 to RB.) Citation Format: Sarah E. Holton, Anna Bergamaschi, Benita S. Katzenellenbogen, Rohit Bhargava. Mammary fibroblasts induce hormone-independent growth in estrogen receptor-positive breast cancer cells via an epithelial-to-mesenchymal transition in a 3D cell culture model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 503. doi:10.1158/1538-7445.AM2013-503