Activation of mesenchymal stem cells by macrophages promotes tumor progression through immune suppressive effects
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Xiao-hua Jia1, Guo-wei Feng2,4,5, Zhong-liang Wang3, Yang Du1, Chen Shen1, Hui Hui1, Dong Peng1,3, Zong-jin Li4, De-ling Kong5, Jie Tian1,6
1Key Laboratory of Molecular Imaging of the Chinese Academy of Sciences, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
2Department of Genitourinary Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
3School of Life Science and Technology, Xidian University, Shaanxi, Xi’an 710071, China
4Department of Pathophysiology, Nankai University School of Medicine, Tianjin 300071, China
5State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials, Ministry of Education, College of Life Sciences, Nankai University, Tianjin 300071, China
6Beijing Key Laboratory of Molecular Imaging, Beijing 100190, China
Jie Tian, e-mail: Jie.email@example.com
Keywords: mesenchymal stem cells, macrophages, inflammation, cancer, MCP1
Received: October 02, 2015 Accepted: January 23, 2016 Published: March 14, 2016
Cancer development and progression is linked to tumor-associated macrophages (TAMs). Distinct TAMs subsets perform either protective or pathogenic effects in cancer. A protective role in carcinogenesis has been described for M1 macrophages, which activate antitumor mechanisms. By comparison, TAMs isolated from solid and metastatic tumors have a suppressive M2-like phenotype, which could support multiple aspects of tumor progression. Currently, it has not been clearly understood how macrophages in tumor-associated stroma could be hijacked to support tumor growth. Mesenchymal stem cells (MSCs) actively interact with components of the innate immune system and display both anti-inflammatory and pro-inflammatory effects. Here, we tested whether MSCs could favor the tumor to escape from immunologic surveillance in the presence of M1 macrophages. We found that MSCs educated by M1 condition medium (cMSCs) possessed a greatly enhanced ability in promoting tumor growth in vivo. Examination of cytokines/chemokines showed that the cMSCs acquired a regulatory profile, which expressed high levels of iNOS and MCP1. Consistent with an elevated MCP1 expression in cMSCs, the tumor-promoting effect of the cMSCs depended on MCP1 mediated macrophage recruitment to tumor sites. Furthermore, IL-6 secreted by the cMSCs could polarize infiltrated TAMs into M2-like macrophages. Therefore, when macrophages changed into M1 pro-inflammation type in tumor microenvironment, the MSCs would act as poor sensors and switchers to accelerate tumor growth.
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