Dual role of human tooth germ derived mesenchymal stem cells on cancer cells

Mesencyhmal stem cells (MSCs), important components of the tumor microenvironment, could modulate tumor growth and development in many ways. MSCs have been used as targeted-delivery vehicles for cancer gene therapy because of their potential of tumor tropism. In this study, we investigated the effects of Human Tooth Germ (HTG) derived MSCs on MCF-7 (Human breast cancer cell line) and SH-SY5Y (Human metastatic neuroblastoma cell line) cells treated with doxorubicin and paclitaxel, anticancer drugs. We also investigated the in vitro effect of genetically modified MSCs secreting apoptosis inducers (Tumor necrosis factors related apoptosis inducing ligand (TRAIL), Dickkopf-related protein-1(Dkk-1)) on SH-SY5Y cells.In the first part, conditioned medium (CM) of hTGSCs was collected when the cells reached to 70% confluency. Effects of this CM on MCF-7 and SH-SY5Y treated doxorubicin and paclitaxel were measured by MTS (cell viability assay) assay and real time PCR analysis of apoptotic markers caspase3 and p53.In the second part, TRAIL and Dkk-1 genes tagged with pkh67 (Green Fluorescent Cell Linker Kit) were transferred into MSCs by electroporation either alone or in combination. A GFP gene transfected group was used as a control. Genetically modified MSCs were co-cultured with SH-SY5Y cells for 24 hours. Thereafter the cell survival of SH-SY5Y cells was determined by using flow cytometry. The expression of Bcl-2, Bax, Stat3 (proliferation genes), FADD, caspase3 (apoptotic genes) in SH-SY5Y cells were assessed by real time PCR.The results showed CM of hTGSCs increased the survival of MCF-7 and SH-SY5Y cells treated with doxorubicin and paclitaxel by 30% and also CM reduced doxorubicin and paclitaxel induced apoptosis. On the other side, genetically modified MSCs secreting TRAIL and Dkk-1 reduced the cell survival of cancer cells by inducing apoptosis and inhibiting the proliferation. Our findings demonstrated that MSCs play roles in growth of tumor cells by decreasing the effect of anti-cancer drugs on cancer cells. On the other hand genetically modified HTG derived MSCs expressing Trail and Dkk-1 might be a potential gene and cell therapy approach to treat certain types of cancer.