Antitumor effect in cyclosporine A- or FK506-treated mice after syngeneic bone marrow transplantation.

We investigated the possibility for induction of graft-versus-tumor (GVT) effects in cyclosporine A (CsA)- or FK506 (FK)-treated DBA/2 mice after syngeneic bone marrow transplantation (BMT). For in vitro assays of spleen cells, the CsA-treated mice had more enhanced cytotoxic activity against YAC1 and P388, while the FK-treated animals had more against P815, YAC1, and P388. IL-4 mRNA expression was detected in spleen cells of the FK-treated mice and IL-6 mRNA expression was clearly detected in both the treated groups. Concerning GVT effects, FK had more pronounced immunostimulatory potential than CsA in this experimental setting using DBA/2 mice. In tumor-loading in vivo experiments, we could not show any antitumor effect on survival. However, this immunostimulation could be expected to eradicate the minimal residual disease after autologous BMT and autologous peripheral blood stem cell transplantation.