Combinations of tumor-specific CD8+ CTLs and anti-CD25 mAb provide improved immunotherapy

One new approach to cancer therapy is based on the adoptive transfer of tumor-specific cytotoxic T cells and anti-CD25 antibodies. In the present study, CD8+ and IFN-gamma secreting T lymphocytes (CTLs) were enriched as tumor-specific cytotoxic T cells from spleen lymphocytes of mice bearing the Renca tumor (a murine renal carcinoma line originating from a BALB/c mouse) after stimulation with tumor cells. An anti-CD25 IL-2Ralpha(anti-CD25) mAb from hybridoma PC61 was used for depletion for CD4(+)CD25(+) regulatory T (Treg) cells. Treatment-efficacy for tumor-bearing mice was compared using 4 systems: 1, whole spleen lymphocytes stimulated with tumor cells in vitro from tumor-bearing mice; 2, CTLs; 3, anti-CD25 mAbs; 4, CTLs and anti-CD25 mAbs. At the 50th day after tumor inoculation, in the group which received anti-CD25 mAb for depletion of T cells and inoculation of CTLs, tumors had disappeared and no re-growth was observed. In contrast, all mice of the non-treated and other three groups, treated with whole spleen cells alone, CTLs alone and anti-CD25 mAb alone, had died. These results showed that a combination of Treg cell-depletion using anti-CD25 mAbs and CTL administration is a feasible approach for treatment of cancers which warrants further exploration in the clinical setting.