[Effect of JMJD3-IRF4 Signaling Pathway-Mediated Macrophage Polarization on the Malignant Biological Behavior of Multiple Myeloma Cells].

Objective: To investigate the effect of macrophage polarization mediated by Jumonji domain containing-3 (JMJD3)-interferon regulatory factor 4 (IRF4) signaling pathway on the malignant biological behavior of multiple myeloma (MM) cells.

Methods: THP-1 monocytes were induced to differentiate into macrophages by phorbol myristate acetate (PMA). THP-1 macrophages were divided into control group (normal culture), M2 induction group ［added recombinant human interleukin (IL) -4, IL-13 proteins］, M2+JMJD3 protein group (added recombinant human IL-4, IL-13 and JMJD3 proteins) and M2+JMJD3 inhibitor group (added recombinant human IL-4, IL-13 proteins and JMJD3 inhibitor), the proportion of CD206 cells was detected by flow cytometry, the levels of IL-10 and transforming growth factor-β (TGF-β) in the culture supernatant were detected by ELISA assay, the expression levels of arginase-1 and mRNA were detected by real-time quantitative PCR (qRT-PCR), and the expression levels of Arg-1, JMJD3 and IRF4 proteins were detected by Western blot. Correspondingly, human MM cells U266 were cultured with THP-1 macrophage culture supernatant of each group, Methyl thiazolyl tetrazolium (MTT) method and plate colony formation assay were used to detect cell proliferation, cell apoptosis was detected by flow cytometry, Western blot was used to detect the expression levels of apoptosis-promoting protein Bcl-2-associated X protein (Bax) and cleaved caspase-3 in cells, and Transwell assay was used to detect cell migration and invasion.

Results: Compared with the control group, the proportion of CD206 cells in THP-1 macrophages, the mRNA and protein expression levels of Arg-1, JMJD3 and IRF4, and the levels of IL-10 and TGF-β in the cell culture supernatant in M2 induction group were significantly increased ( <0.001), meanwhile, the proliferation activity and the number of clones of U266 cells were significantly increased ( <0.01), the apoptosis rate and the expression levels of apoptosis-promoting protein Bax and cleaved caspase-3 were significantly decreased ( <0.001), the numbers of migrated cells and invasive cells were increased ( <0.001). Compared with M2 induction group, the proportion of CD206 cells in THP-1 macrophages, the mRNA and protein expression levels of Arg-1, JMJD3 and IRF4, and the levels of IL-10 and TGF-β in the cell culture supernatant in M2+JMJD3 protein group were further increased ( <0.01), meanwhile, the proliferation activity and the number of clones of U266 cells were further increased ( <0.05), the apoptosis rate and the expression levels of apoptosis-promoting protein Bax and cleaved caspase-3 were further decreased ( <0.01), the numbers of migrated cells and invasive cells were further increased ( <0.001); However, the change trends of the above indexes in M2+JMJD3 inhibitor group were opposite to those in M2+JMJD3 protein group.

Conclusion: M2 polarization of macrophages mediated by JMJD3-IRF4 signaling pathway can promote the proliferation, migration and invasion of MM cells, and inhibit cell apoptosis.