Abstract: Abstract Objective: To identify regulation of MCP-1 in osteoblasts by PTHrP in breast cancer cells. Method: Osteoblast-like UMR106 cells were treated with 10-8 M PTHrP (1–34) for different time intervals and expression of MCP-1 was studied by using semiquantitative RT-PCR. Recombinant shRNA plsmid PTH1R/pRNAT was constructed, transfected into UMR106 cells, and stable PTH1R/UMR106 cells were established in which PTH1R expression was knocked-down. Thereafter, the conditioned medium (CM) of breast cancer MDA-MB231 was added to UMR-106 and PTH1R/UMR106 cultures respectively. The mRNA of MCP-1 treated by PTHrP and CM of breast cancer was examined by RT-PCR. Result: PTHrP induced expression of MCP-1 in UMR106 cells and the induction began at 3 h and reached maximum at 6 h. Treatment of UMR106 cells with CM of MDA-MB231 also significantly induced mRNA of MCP-1, and this effect was blocked by the knockdown of PTH1R in UMR106 cells. Conclusion: Breast cancers upregulated MCP-1 level in osteoblasts through expression of PTHrP.

Key words: breast cancer, PTHrP, osteoblasts, MCP-1