Tumor associated macrophages (TAMs) are increasingly recognized as major contributors to the metastatic progression of
breast cancer and enriched levels of TAMs often correlate with poor prognosis. Despite our current advances it remains unclear which subset of M2-like macrophages have the highest capacity to enhance the metastatic program and which mechanisms regulate this process. Effective targeting of macrophages that aid
cancer progression requires knowledge of the specific mechanisms underlying their pro-metastatic actions, as to avoid the anticipated toxicities from generalized targeting of macrophages. To this end, we set out to understand the relationship between the regulation of
tumor secretions by
Rho-GTPases, which were previously demonstrated to affect them, macrophage differentiation, and the converse influence of macrophages on
cancer cell phenotype. Our data show that IL-4/
IL-13 in vitro differentiated M2a macrophages significantly increase migratory and invasive potential of
breast cancer cells at a greater rate than M2b or M2c macrophages. Our previous work demonstrated that the
Rho-GTPases are potent regulators of macrophage-induced migratory responses; therefore, we examined M2a-mediated responses in RhoA or RhoC knockout
breast cancer cell models. We find that both RhoA and RhoC regulate migration and invasion in MDA-MB-231 and SUM-149 cells following stimulation with M2a
conditioned media. Secretome analysis of M2a
conditioned media reveals high levels of
vascular endothelial growth factor (
VEGF) and
chemokine (C-C motif)
ligand 18 (CCL-18). Results from our functional assays reveal that M2a TAMs synergistically utilize
VEGF and CCL-18 to promote migratory and invasive responses. Lastly, we show that pretreatment with ROCK inhibitors Y-276332 or GSK42986A attenuated
VEGF/CCL-18 and M2a-induced migration and invasion. These results support
Rho-GTPase signaling regulates downstream responses induced by TAMs, offering a novel approach for the prevention of
breast cancer metastasis by anti-RhoA/C
therapies.