Abstract: Objective To study the effects of bone marrow derived mesenchymal stem cells on the growth and differentiation of the tumor formed by HT-29 cells. Methods In vivo, nude mice were divided into 3 groups— HT-29 group, BMSC group and HT-29+BMSC group, in which cell suspensions were subcutaneously injected into nude mice. Tumors were removed after 7 weeks .The volumes and weights of the tumors were measured and HE staining was performed. The expression of an epithelia marker —E-CADHERIN was detected using RT-PCR and immunohistochemistry staining. In vitro, HT-29 cells were co-cultured with BMSCs, the morphology of HT-29 cells was observed, and the expression of EMT related genes were detected using RT-PCR. Results In vivo, no tumor was observed in the BMSC group, and no significant difference was found in the volume and weight of tumors between the HT-29+BMSC group and the HT-29 group. But the tumor cells in the HT-29+BMSC group showed poorly differentiated and lower level expressed of E-CADHERIN compared with the HT-29 group. In vitro, after coculturing with BMSCs, morphological changes of HT-29 cells were observed and were consistent with the expression of EMT related genes. Conclusion The differentiation degree of HT-29 cells is correlated to EMT induced by BMSCs microenvironment.

Key words: bone marrow derived mesenchymal stem cell, HT-29 cell, tumor growth and differentiation, co-culture, EMT, microenvironment