Little Andrew C, Pathanjeli Pragathi, Wu Zhifen, Bao Liwei, Goo Laura E, Yates Joel A, Oliver C Ryan, Soellner Matthew B, Merajver Sofia D
Department of Internal Medicine, Hematology-Oncology, Rogel Cancer Center, University of Michigan, Ann Arbor, MI, United States.
Front Oncol. 2019 May 31;9:456. doi: 10.3389/fonc.2019.00456. eCollection 2019.
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 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.
肿瘤相关巨噬细胞（TAMs）越来越被认为是乳腺癌转移进展的主要促成因素，TAMs水平升高通常与预后不良相关。尽管我们目前取得了进展，但仍不清楚哪种子集的M2样巨噬细胞具有最高的促进转移程序的能力，以及哪些机制调节这一过程。有效靶向促进癌症进展的巨噬细胞需要了解其促转移作用的具体机制，以避免因巨噬细胞的广泛靶向而产生预期的毒性。为此，我们着手了解Rho-GTPases对肿瘤分泌的调节（先前已证明其会影响肿瘤分泌）、巨噬细胞分化以及巨噬细胞对癌细胞表型的反向影响之间的关系。我们的数据表明，IL-4/IL-13分化的M2a巨噬细胞比M2b或M2c巨噬细胞更显著地提高乳腺癌细胞的迁移和侵袭潜力。我们之前的研究表明，Rho-GTPases是巨噬细胞诱导的迁移反应的有效调节因子；因此，我们在RhoA或RhoC基因敲除的乳腺癌细胞模型中研究了M2a介导的反应。我们发现，在用M2a条件培养基刺激后，RhoA和RhoC均调节MDA-MB-231和SUM-149细胞的迁移和侵袭。对M2a条件培养基的分泌蛋白组分析显示血管内皮生长因子（VEGF）和趋化因子（C-C基序）配体18（CCL-18）水平很高。我们功能分析的结果表明，M2a TAMs协同利用VEGF和CCL-18来促进迁移和侵袭反应。最后，我们表明用ROCK抑制剂Y-276332或GSK42986A预处理可减弱VEGF/CCL-18和M2a诱导的迁移和侵袭。这些结果支持Rho-GTPase信号传导调节TAMs诱导的下游反应，为通过抗RhoA/C疗法预防乳腺癌转移提供了一种新方法。
