Abstract: Objective To study the effect of human bone marrow derived MSCs (hBM-MSCs) on the migration and invasion capacity of breast cancer cells in co-culture system. Methods Cytokines secreted by BM-MSCs were detected using ELISA assay. Tumor microenvironments were mimicked by co-culturing of BM-MSCs with breast cancer cell lines (MCF-7 and MDB-MA-231) separately. Capacity of migration and invasion were compared after co-culture using Transwell system．Activation of signal transducer and activator of transcription 3 (STAT3) was detected by Western blot. Experession of metastasis-associated gene matrix metalloproteinases (MMP2 and MMP9) were detected by realtime RT-PCR. Result HGF, IL6, VEGF and TGF β 1 were detected in the medium of BM-MSCs. Co-culturing with BM-MSCs can significantly enhance the migration and invasion capacity of breast cancer cells (the migration and invasion of MCF-7: P<0.01; the migration of MDA-231: P<0. 05; the invasion of MDA-231: P<0. 05)．Signaling pathway of p-STAT3 and p-ERK were activated dramatically(P<0.01), and the expression of MMP2 and MMP9 were increased markedly(P<0.01). Conclusions BM-MSCs may promote the migration and invasion capacity of breast cancer cells by indirect co-culture of the two cell lines．

Key words: mesenchymal stem cell, signal transducer and activator of transcription 3 (STAT3), MMPs (Matrix metalloproteinases), breast cancer metastasis