Abstract: Objective To investigate the effect of M2-type macrophage-derived exosomes on human multiple myeloma cell metastasis and its mechanism. Methods THP-1 cells were induced to differentiate into M0 and M2 macrophages in vitro. Real-time fluorescent quantitative polymerase reaction ( RT-qPCR) was used to detect the expression levels of hemoglobin scavenger receptor ( CD163 ), interleukin-10 ( IL-10 ), arginase-1 ( Arg-1 ) and transforming growth factor-β1 ( TGF-β1 ) in induced M2 macrophages. Exosomes derived from M2 macrophages were isolated. RPMI-8226 cells were divided into 3 groups: control group, M0-Exos group and M2-Exos group. Then the cell migration and invasion were detected by Transwell. The expression levels of Ncadherin, Vimentin, E-cadherin and the transcription factor Snail, and hepatocyte growth factor (HGF) / c-Met related proteins were detected by Western blotting. Moreover, RPMI-8226 cells were then divided into 4 groups: control group, M2-Exos group, SU11274 group and SU11274 + M2-Exos group, and cell migration and invasion were detected by Transwell, and the expressionlevels of N-cadherin, Vimentin, E-cadherin and Snail were detected by Western blotting. Results The mRNA expression levels of CD163, IL-10, Arg-1 and TGF-β1 in the M2 macrophages weresignificantly up-regulated when compared with those in the M0 macrophages (P< 0. 05). The particles isolated from the M2 macrophages showed protein expressions of CD9, CD63, TSG101 and ALIX, and were identified as exosomes. The numbers of cell migration and invasion in the M2-Exosgroup were significantly increased when compared with those in the control group (P < 0. 05), theprotein expression levels of N-cadherin, Vimentin and Snail, and the HGF protein expression andp-c-Met / c-Met ratio were significantly increased (P< 0. 05), and the protein expression level of Ecadherin was significantly decreased (P< 0. 05). The numbers of cell migration and invasion in theSU11274 + M2-Exos group were significantly decreased when compared with those in the M2-Exosgroup (P< 0. 05), the protein expression levels of N-cadherin, Vimentin and Snail were significantly decreased (P< 0. 05), and the protein expression level of E-cadherin was significantly increased (P< 0. 05). Conclusion M2-type macrophage-derived exosomes can promote the migration, invasion and EMT of human multiple myeloma cells, which exacerbate tumor cell metastasis, the mechanism may relate to the regulation of HGF / c-Met pathway.

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