Synergistic therapeutic effects of cytokine-induced killer cells and temozolomide against glioblastoma

The presence of active immunity within the brain supports the possibility of effective immunotherapy for glioblastoma (GBM). To provide a clinically-relevant adoptive immunotherapy for GBM using ex vivo expanded cytokine-induced killer (CIK) cells, the treatment capability of CIK cells, either alone or in combination with temozolomide (TMZ) were evaluated. Human CIK (hCIK) cells were cultured from PBMC using activating anti-CD3 antibody and IL-2, which were 99% CD3(+), 91% CD3(+)CD8(+) and 29% CD3(+)CD56(+). In vitro, hCIK cells showed tumor-specific cytotoxicity against U-87MG human GBM cells. When hCIK cells were injected into tail veins of immune-compromised mice bearing U-87MG tumors in their brains, numerous CIK cells infiltrated into the brain tumors. CIK treatments (1x10(5), 1x10(6) or 1x10(7), once a week for four weeks) inhibited the tumor growth significantly in a dose-dependent manner; 44, 54 and 72% tumor volume reduction, respectively, compared with the control group (P<0.05). Moreover, hCIK cells (1x10(7), once a week for four weeks) and TMZ (2.5 mg/kg, daily for 5 days) combination treatment further increased tumor cell apoptosis and decreased tumor cell proliferation and vessel density (P<0.05), creating a more potent therapeutic effect (95% reduction in tumor volume) compared with either hCIK cells or TMZ single therapy (72% for both, P<0.05). Taken together, CIK cell-immunotherapy and TMZ chemotherapy have synergistic therapeutic effects and could be combined for a successful treatment of GBM.