Sirt1 Expression Related with Sarcoma Growth after Stem Cell Transplantation Combined with Depletion of Myeloid-Derived Suppressor Cells

Sirtuins (Sirt) play a number of roles in various aging-related diseases such as obesity, diabetes and cancer, and Sirt1 plays a double role in cancer. The combination of bone marrow transplantation (BMT) and thymus transplantation (TT) has been shown to prevent the growth of malignant tumors. Myeloid-derived suppressor cells (MDSCs) can differentiate from bone marrow stem cells under pathological conditions such as cancer, and prevent the potent action of T cells and NK cells, thereby promoting tumor growth. Thus, depleting MDSCs is important when treating cancer. We therefore investigated the relationship between Sirt1 expression and sarcoma growth in sarcoma-bearing mice treated with BMT+TT and the depletion of MDSCs using Gr-1 Ab. Our results showed that only granulocytic MDSCs (G-MDSCs) were depleted by the Gr-1 Ab in these mice. Moreover, the sarcomas decreased significantly in size in the Gr-1 antibody group when compared with the BMT group. This was due to the increase in the percentage of T cells and decrease in the percentage of G-MDSCs. Furthermore, Sirt1 expression decreased significantly in the sarcoma. These findings suggest that inactive Sirt1 may prevent sarcoma growth in sarcoma-bearing mice that receive stem cell transplants and depletion of MDSCs.