eradication of established murine skin tumors by cyclic chemoimmunotherapy with cyclophosphamide and effector t cells

background : nonmyeloablative chemotherapy followed by adoptive immunotherapy is an attractive strategy for depleting regulatory t cells in the host. however, its efficacy is transient. here, we aim to investigate whether cyclic chemoim- munotherapy has therapeutic efficacy against cancer. methods :we examined the efficacy of cyclic chemoimmunotherapy with cyclophos- phamide and adoptively transferred effector t cells against 5-day, established mca205 murine skin sarcomas. results : cyclophosphamide administration followed by adoptive immunotherapy augmented the trafficking of effector t cells into established tumors. further, multiple cyclophosphamide administrations helped effector t cells to persist at the sites. chemoimmunotherapy achieved complete tumor regression even with the transfer of a limited number of effector t cells (5×106). conclusion : cyclic chemoimmunotherapy, which maintains adoptively transferred t cells by impairing regulatory t cells, is a potentially suitable treatment for established tumors.