Abstract 4891: Dormancy and growth of metastatic breast cancer cells in a bone-like microenvironment
Authors: Chen Yu-Chi , Mastro Andrea M. , Sosnoski Donna M. , Norgard Robert J. , Grove Cassidy D. , Vogler Erwin A. 
Published: May 2015

Abstract
We have developed a three dimensional cell culture model (bioreactor) in which cancer cells are cultured in a bone-like microenvironment. When co-cultured with MC3T3-E1 osteoblasts and the resulting bone-like matrix, MDA-MB-231 (231) human metastatic breast cancer cells attach, form “single cell files”, develop invadapodia, infiltrate and partially degrade the thick matrix. Eventually, the cells form large colonies. By contrast, the metastasis-suppressed variant, MDA-MB-231BRMS1, (231BRMS1) demonstrates a dormant phenotype in the same system. They loosely attach, and are slow to proliferate. This pattern of growth is also observed in femurs of mice inoculated with these cells. We hypothesized that changes in the cytokine microenvironment or the matrix structure would either cause the 231 cells to become dormant or the 231BRMS1 cells to proliferate. Because of anecdotal evidence that bone trauma or breakage is associated with latent metastasis, we added either a cocktail of inflammatory cytokines (IL-6, IL-8, MCP-1, VEGF, GROα ) or bone remodeling cytokines (IL-6, TNFα, IL-1β, PGE-2 ). The inflammatory cytokines had little effect on the morphology or proliferation of either cell type. In contrast, bone remodeling cytokines stimulated the 231BRMS1 cells to grow vigorously. Of the remodeling cytokines, we determined that TNFα and IL-1β were sufficient to cause the change in growth. However, we were able to block the response of the 231BRMS1 cells with indomethecin, a cyclooxygenase inhibitor or with an inhibitor to the receptor for PGE2. These data suggest that the additional cytokines lead to prostaglandin production.
We also modulated the matrix by growing the osteoblasts with charcoal-stripped serum to reduced estradiol. The osteoblasts differentiated under these conditions (alkaline phosphatase positive) but did not fully mineralize the matrix (minimal von Kossa staining ). In the presence of the modified matrix, both the 231(ER-) and the 231BRMS1(ER-) cells showed increased proliferation. In contrast, MCF-7 cells (ER+) maintained a dormant phenotype and did not grow. In conclusion, our data highlight the importance of a bone-like microenvironment in maintaining breast cancer dormancy. Disrupting the microenvironment could result in dormant cells re-entering the cell cycle. We are currently determining the role of the cytokine microenvironment and the matrix alteration in the modulation of the cancer cells dormancy or growth in the bone.
This work was supported by the U.S. Army Medical Research and Materiel Command under W81XWH-12-1-0127, and by the Metavivor Research Foundation.
Citation Format: Yu-Chi Chen, Andrea M. Mastro, Donna M. Sosnoski, Robert J. Norgard, Cassidy D. Grove, Erwin A. Vogler. Dormancy and growth of metastatic breast cancer cells in a bone-like microenvironment. [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 4891. doi:10.1158/1538-7445.AM2014-4891