Immunotherapy in gliomas: limitations and potential of natural killer (NK) cell therapy

Malignant gliomas (MGs) are deadly brain tumors with a median survival after resection, radiotherapy and chemotherapy of only 12 months. The natural immunosuppressive state of MG patients and the locally restricted growth of MGs render this neoplasm an excellent target for immunotherapy. Consequently, several failed attempts were made to treat MGs with immune cells. Recent preclinical experimental studies, however, demonstrate that natural killer (NK) cells can kill MGs and therefore hold promise in immunotherapy of MGs. This review describes the experimental and clinical evidence that support the potential of NK cells in therapy of MGs as well as the limitations to NK therapy. Finally, we propose strategies that could circumvent mitigating factors and enhance NK cell therapy for MG patients.