Suppression of Mll1-Complex by Stat3/Cebp β-Induced miR-21a/21b/181b Maintains the Accumulation, Homeostasis, and Immunosuppressive Function of Polymorphonuclear Myeloid-Derived Suppressor Cells.

In this study, microarray analysis revealed that the core components of the Mll1-complex, Wdr5, Ash2l, and Mll1, were concurrently downregulated by tumor-secreted factors as well as GM-CSF + IL-6 during the accumulation and activation of murine myeloid-derived suppressor cells (MDSCs). These changes were further validated by quantitative RT-PCR and Western blotting both in vitro and in vivo. The expression levels of WDR5 and ASH2L were also significantly decreased in bone marrow MDSCs of lung cancer patients compared with that of healthy controls. Functionally, ectopic expression of Wdr5, Ash2l, and Mll1 (C terminus) reversed the accumulation and function of GM-CSF + IL-6-induced as well as tumor-cocultured polymorphonuclear MDSCs (PMN-MDSCs) by promoting them to differentiate into mature neutrophil-like cells. Mechanistically, GM-CSF + IL-6-activated Stat3 and Cebpβ synergistically induced the expression of miR-21a, miR-21b, and miR-181b, and thus inhibited the expression of Wdr5, Ash2l, and Mll1 by targeting to their 3' untranslated regions, respectively. Furthermore, knockdown of these microRNAs also suppressed the expansion and function of GM-CSF + IL-6-induced PMN-MDSCs. Taken together, our findings indicate that the Stat3/Cebpβ-miR-21a/b/181b-Mll1-complex axis may play a critical role in PMN-MDSC expansion, activation, and differentiation, and this axis may provide an effectively immunological therapeutic approach for patients with cancer or other immunological diseas...
Source: Journal of Immunology - Category: Allergy & Immunology Authors: Tags: J Immunol Source Type: research