中文摘要：

研究表明，间充质干细胞具有向肿瘤细胞定向迁移并且抑制肿瘤细胞的特性，然而其分子机理目前尚不清楚．为了探讨间充质干细胞抑制肿瘤细胞作用的分子机制，应用BMMS-03人间充质干细胞的条件培养液作用于MCF-7乳腺癌细胞，通过软琼脂克隆形成实验、MTT实验、免疫印迹和免疫荧光染色等技术观察细胞克隆形成、增殖和基因表达的变化．结果显示：在BMMS-03细胞条件培养液作用下，MCF-7细胞的克隆形成和增殖受到了明显的抑制，β-catenin及其下游靶蛋白c-Myc、Bcl-2、PCNA和survivin的表达被明显下调，MCF-7细胞浆和细胞核内β-catenin的表达被明显抑制．BMMS．03细胞中Dkk-1的表达水平与MCF-7细胞相比较高．利用抗Dkk．1的抗体中和BMMS-03细胞条件培养液中的Dkk-1后，可明显拮抗BMMS．03细胞条件培养液对MCF-7细胞中B．catenin及c-Myc表达的抑制作用，基因转染使MCF-7细胞过表达Dkk-1后，MCF-7细胞的β-catenin及c-Myc的表达明显下调．同样经基因转染使BMMS-03细胞过表达Dkk-1后，其条件培养液可进一步下调MCF-7细胞β-catenin及c-Myc的表达．上述结果表明，间充质干细胞BMMS-03对乳腺癌MCF-7细胞的恶性表型具有明显抑制作用，其分子机制与间充质干细胞释放Dkk-1抑制乳腺癌细胞Wnt/β-catenin信号途径有关．

英文摘要：

Growing evidences show that mesenchymal stem cells （MSCs） home to tumorgenesis and inhibit tumor cells, however, the molecular mechanisms underlying are unclear. The human mesenchymal stem cells （hMSCs） derived from human fetal bone marrow in 4 months were established without immortalization, designated BMMS-03 cells. In order to clarify the molecular mechanism underlying, the effect of conditioned media from hMSCs on human breast cancer MCF-7 cells was examined. The results showed that conditioned media from BMMS-03 cells were able to decrease the colony-forming units and proliferation of MCF-7 cells by colony-forming assay and MTT assay. Western blot analysis revealed that β-catenin and its target gene c-Myc, Bcl-2, PCNA and survivin were downregulated in MCF-7 cells treated with conditioned media from BMMS-03 cells. In addition, the treatment significantly reduced β-catenin nuclear assembly in MCF-7 cells by immunoflorescence staining. The finding demonstrated that the expression level of Dkk-I in hMSCs was much higher than that in MCF-7 cells. Moreover, treatment with the antibody of rabbit against Dkk-1 abolished the inhibitory effects of conditioned media from BMMS-03 on the tumor cells. Conditioned media from BMMS-03 cells transiently transfected with pcDNA3.1 （-）-Dkk- 1 produced stronger downregulation of β-catenin and c-Myc expression in MCF-7 cells. The transfection with pcDNA3.1 （-）-Dkk-1 in MCF-7 cells resulted in the downregulation of β-catenin and c-Myc as well. The data suggest that hMSCs are able to decrease the malignant phenotype of tumor cells in vitro. Taken together, hMSCs may suppress tumor growth via Wnt/β-catenin pathway, in which Dkk- 1 released from the hMSCs is responsible for the depression.