Abstract 1179: Macrophage conditioned media increases the expression of a metastasis-associated oncogene, RhoC, and the migration of inflammatory breast cancer cells

Abstract

Abstract Inflammatory breast cancer (IBC) is the most lethal form of breast cancer because it progresses rapidly and often presents with distant metastases at diagnosis. RhoC GTPases, known to play an important role in the movement of cells, are overexpressed in IBC tumor cells. The mechanism that causes this increase in RhoC expression is unknown. Tumor associated macrophages (TAMs) have been found to facilitate the movement and invasion of breast cancer. Therefore, as a component of the immune system attracted to sites of inflammation, we hypothesized that TAMs play a role in increasing RhoC expression in IBC cells, which consequently leads to IBC's severe migratory and metastatic capabilities. The expression of RhoC increased in two different IBC cell lines, SUM149 and SUM190, in the presence of conditioned media (CM) from macrophage-differentiated U937 cells. This increase was not observed in either the normal-like MCF-10A cell line or the non-IBC MDA-MB-231 breast cancer cell line. From this observation, a novel microfluidic device allowed the study of the migratory phenotype of individual cells of the two IBC cell lines in response to standard chemoattractants as well as the macrophage CM. As expected, the presence of a serum gradient promoted the chemotaxis of IBC cells versus serum-free control. A CM gradient also increased the migration of IBC cells to a moderate degree. However, in the overlapping presence of CM without a gradient and serum with a gradient, the cells exhibiting an extreme migratory phenotype migrated roughly twice the distance of the serum gradient control. We believe the CM acts to “prime” the IBC cells in order to manifest an ultra-response to the serum chemoattractant. In both IBC cell lines stably-transfected with shRNA targeted to RhoC, we observed decreased migration when exposed to the CM migration conditions. Therefore, RhoC expression is necessary for this increase in migration. Studies involving RhoC inhibitors are ongoing, but could yield promising therapies for the prevention of metastasis of IBC. Future studies will aim to identify which cytokines in the CM and which specific pathways are responsible for the increased RhoC expression and migration of IBC cells. By understanding the specific mechanism of TAMs' effects on IBC cells we hope to learn better how to control the lethal metastatic nature of inflammatory breast cancer. Citation Format: Chelsea L. Fournier, Steven G. Allen, Yu-Chih Chen, Euisik Yoon, Sofia D. Merajver. Macrophage conditioned media increases the expression of a metastasis-associated oncogene, RhoC, and the migration of inflammatory 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 1179. doi:10.1158/1538-7445.AM2014-1179