Effects of human bone morphogenetic protein 9 on migration and apoptosis of human breast cancer cells in simulated bone microenvironment in vitro

Objective: To investigate the effects of human BMP9 (bone morphogenetic protein 9) on migration and apoptosis of human breast cancer MDA-MB-231 cells in simulated bone microenvironment, and to explore its mechanism. Methods: MDA-MB-231 cells were infected with recombinant adenovirus AdBMP9 or AdGFP, then the cells were co-cultured with HS-5 bone marrow stromal cells for 3 d. The expression level of BMP9 was detected by RT (reverse transcription)-PCR and Western blotting. Wound-healing test, Transwell migration test and FCM (flow cytometry) were used to determine the changes of migration ability and apoptosis of MDA-MB-231 cells. Metastasis-related factors, including SDF-1 (stromal cell-derived factor-1), IL-6 (interleukin-6) and MCP-1 (monocyte chemoattractant protein-1) in MDA-MB-231 and HS-5 cells, were screened by RT-PCR. Immunofluorescence method was used to detect the expression of CXCR4 in MDA-MB-231 cells. Western blotting was carried out to detect the key molecules of SDF-1/CXCR4-PI3K signaling pathway in MDA-MB-231 and HS-5 cells. Results: In simulated bone microenvironment of co-culture system, BMP9 over-expression could significantly inhibit the migration (P < 0.05) and promote apoptosis of MDA-MB-231 cells (P < 0.001). Compared with the control groups, BMP9 over-expression decreased the expession levels of IL-6 and MCP-1 in HS-5 and MDA-MB-231 cells (P < 0.05). However, the level of SDF-1 was decreased only in HS-5 cells, but not changed in MDA-MB-231 cells. The MDA-MB-231 cells expressed CXCR4 themselves, and BMP9 over-expression could not change the expression level of CXCR4. The levels of SDF-1 in HS-5 cells and p-Akt (phosphorylated Akt) in MDA-MB-231 cells were down-regulated after BMP9 over-expression (P < 0.05). Conclusion: BMP9 can inhibit the migration and promote the apoptosis of breast cancer MDA-MB-231 cells in simulated bone microenvironment by regulating the cross-talk between MDA-MB-231 cells and HS-5 bone marrow mesenchymal cells. SDF-1/CXCR4-PI3K pathway may be involved in this process. DOI:10.3781/j.issn.1000-7431.2013.08.001