Abstract 4017: Matrix manipulation affects attachment and growth of breast cancer cells in a bone-like microenvironment in vitro
Authors: Foster Shelby J. , Sosnoski Donna M. , Mastro Andrea M. 
Published: August 2015

Abstract
Breast cancer notoriously metastasizes to the bone, but it is unknown why breast cancer cells colonize there. Breast cancer cells may become dormant in the skeleton until a stimulated to grow. The aim of this project is to better understand the role of the bone matrix in determining dormancy or growth. Breast cancer cells were co-cultured with MC3T3-E1 mouse osteoblasts that formed a collagenous matrix. The matrix was manipulated by fixation, decellularization, and by varying the medium estrogen levels as the osteoblasts grew. MDA-MB-231-BRMS1GFP (BRMS), a metastatic suppressed variant of the human MDA-MB-231 breast cancer cell line, was used because these cells do not grow in the bone, allowing for observation of growth or dormancy. BRMS were added to a matrix produced by differentiated MC3T3-E1 cells.
BRMS proliferated more on a culture of osteoblasts and their matrix when fixed with 1% paraformaldehyde than on a live osteoblasts matrix. Why do the cells proliferate more on the fixed matrix? We ruled out the possibility that live osteoblasts and cancer cells competed for growth medium. Another possibility was that BRMS attach differently to the matrices with live or fixed osteoblasts. We compared attachment of BRMS to live, fixed, and decellularized matrices and to tissue culture plastic, and after 60 minutes it was seen that more BRMS cells attached to a fixed matrix compared to the other conditions. Fluorescent microscopy revealed that BRMS had many attachment points on a fixed matrix. On the live osteoblasts matrix, the cancer cells remained attached to one another instead of attaching to the matrix. Experiments will determine if the attachment explains the effect on proliferation by testing for attachment factors such as β-actin and focal adhesion kinase.
Breast cancer is more prevalent in post-menopausal women. Estrogen production decreases with menopause, leading to the hypothesis that the effects of estrogen deprivation on bone cause metastasis. Osteoblasts were grown in the presence of ICI, an estrogen inhibitor preventing estrogen from binding. Osteoblasts grown with and without ICI were assayed for alkaline phosphatase (AP), stained with von Kossa (mineralization), and with ChondrexTM (collagenous and noncollagenous proteins). While AP and mineralization levels were unaffected by the estrogen inhibition, collagenous proteins production decreased. We will study breast cancer cell attachment to matrices grown without estrogen. It is hypothesized that proliferation will increase on a matrix with less collagen, similar to the increased proliferation seen on a fixed matrix.
Work was supported by the U.S. Army Medical Research & Materiel Command under W81XWH-12-1-0127, the Metavivor Research Foundation, Undergraduate Research Funds from the Eberly College of Science & the Biochemistry & Molecular Biology Summer Undergraduate Research Program.
Citation Format: Shelby J. Foster, Donna M. Sosnoski, Andrea M. Mastro. Matrix manipulation affects attachment and growth of breast cancer cells in a bone-like microenvironment in vitro. [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 4017. doi:10.1158/1538-7445.AM2015-4017