Prolonged survival in mice with advanced tumors treated with intra-bone marrow-BMT plus fetal thymus transplantation with restoration of T cell functions (P2177)

Abstract

Abstract Thymic function decreases in line with tumor progression in patients with cancer, resulting in immunodeficiency and a poor prognosis. In the present study, we attempted to restore thymic function by BALB/c (H-2d) syngeneic (Syn) or B6 (H-2b) allogeneic (Allo) bone marrow transplantation (BMT) using intra-bone marrow-bone marrow transplantation (IBM-BMT) plus Syn-, Allo- or C3H (H-2k) 3rd-party fetal thymus transplantation (TT). Although the BALB/c mice with advanced tumors (Meth-A sarcoma; H-2d, >4 cm2) treated with either Syn- or Allo-BMT alone showed a slight improvement in survival compared with non-treated controls, the mice treated with BMT + TT showed a longer survival. The mice treated with Allo-BMT + Allo-TT or 3rd-party TT showed the longest survival. Interestingly, although there was no difference in main tumor size among the BMT groups, lung metastasis was significantly inhibited by Allo-BMT + Allo-TT or 3rd-party TT. Although host thymus was still atrophied, transplanted thymus was well-engrafted. T cell functions increased significantly, whereas number of myeloid suppressor cells and regulatory T cells significantly decreased in these mice. These results suggest that BMT + TT, particularly Allo-BMT + Allo-TT or 3rd-party TT, is most effective in prolonging survival as a result of the restoration of T cell function in hosts with advanced tumors.