Journal
CANCER RESEARCH
Volume 75, Issue 3, Pages 519-531Publisher
AMER ASSOC CANCER RESEARCH
DOI: 10.1158/0008-5472.CAN-14-2331
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Funding
- NIH [CA149669]
- Ovarian Cancer Research Foundation Funds [LT/UTHSC/01.2011]
- Northwestern University RHLCCC Flow Cytometry Facility, Cancer Center [NCI CA060553, CA054174]
- Owens Foundation
- Skinner Endowment the Holly Beach Public Library Association
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miR155 is a regulator of immune cell development and function that is generally thought to be immunostimulatory. However, we report here that genetic ablation of miR155 renders mice resistant to chemical carcinogenesis and the growth of several transplanted tumors, suggesting that miR155 functions in immunosuppression and tumor promotion. Host miR155 deficiency promoted overall antitumor immunity despite the finding of defective responses of miR155-deficient dendritic cells and antitumor T cells. Further analysis of immune cell compartments revealed that miR155 regulated the accumulation of functional myeloid-derived suppressive cells (MDSC) in the tumor micro-environment. Specifically, miR155 mediated MDSC suppressor activity through at least two mechanisms, including SOCS1 repression and a reduced ability to license the generation of CD4(-)Foxp3(+) regulatory T cells. Importantly, we demonstrated that miR155 expression was required for MDSC to facilitate tumor growth. Thus, our results revealed a contextual function for miR155 in antitumor immunity, with a role in MDSC support that appears to dominate in tumor-bearing hosts. Overall, the balance of these cellular effects appears to be a root determinant of whether miR155 promotes or inhibits tumor growth. (C) 2014 AACR.
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