Abstract 5068: Carcinoma-associated fibroblast-derived CXCL12 enhances MDA-MB-231 tumor cell migration though mDia2 formin suppression

Abstract

Abstract The tumor microenvironment (TME) is a heterogeneous region comprised of tumor cells, stromal cells, and secreted factors that make the environment favorable for cancer formation and progression. An important step in the shift to a pro-cancerous environment is the transformation of normal stromal fibroblasts to carcinoma-associated fibroblasts (CAFs). CAFs are a critical cell type to understand. They are present in a majority of solid tumors and can have a direct effect to enhance adjacent tumor cell motility via their innate ability to secret cytokines, chemokine and growth factors into the TME. We sought to understand how CAF-derived chemokines impact breast tumor cell motility through modification of the F-actin cytoskeleton. We collected cultured media (CM) from WS19T fibroblasts, a patient-derived breast tumor CAF cell line. CAF-CM dramatically enhanced wound-closure in MDA-MB-231 monolayers, relative to normal fibroblast cultured media. The chemokine CXCL12 (SDF1 alpha) has been identified as a potential secreted CAF-directed signal driving tumor cell migration. To determine if CXCL12 was the soluble factor in CAF-CM promoting tumor cell migration, MDA-MB-231 cells were preincubated with AMD3100, an inhibitor of the CXCL12 receptor, CXCR4 prior to CAF-CM application and wounding. AMD3100 effectively blocked CAF-CM-induced MDA-MB-231 migration. CXCL12 incubation with MDA-MB-231 cells equally promoted MDA-MB-231 wound closure, supporting the notion that CXCL12 is secreted by CAFs to promote MDA-MB-231 motility. We previously showed a link between CXCL12 directed CXCR4 signaling and a critical regulator of the dynamic F-actin cytoskeleton, mammalian Diaphanous-related formin (mDia2). This formin regulates the assembly and bundling of unbranched actin filaments and plays a role in tumor cell migration and invasion programs. Western blotting CAF-CM-treated MDA-MB-231 cells revealed a near complete loss of mDia2 protein. mDia1 and ROCK expression were unaffected with CAF-CM treatment. These data were consistent with treatment with a functional mDia FH2-domain inhibitor SMIFH2, which likewise suppresses mDia2 protein levels in MDA-MB-231 cells. It remains unclear if CAF-derived CXCL12 first suppresses mDia2 FH2 activity, leading to loss of mDia2 protein, thus promoting tumor cell motility. Current experiments are designed to address this gap in the knowledge, potentially indicating a role for CAF-derived soluble factors in modulating mDia2 protein function and expression in migrating tumor cells. Citation Format: Kaitlyn Dvorak, Kathryn M. Eisenmann. Carcinoma-associated fibroblast-derived CXCL12 enhances MDA-MB-231 tumor cell migration though mDia2 formin suppression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5068.