Increasing the Clinical Efficacy of NK and Antibody-Mediated Cancer Immunotherapy: Potential Predictors of Successful Clinical Outcome Based on Observations in High-Risk Neuroblastoma

Disease recurrence is frequent in high-risk neuroblastoma (NBL) patients even after multi-modality aggressive treatment [a combination of chemotherapy, surgical resection, local radiation therapy, autologous stem cell transplantation, and cis-retinoic acid (CRA)]. Recent clinical studies have explored the use of monoclonal antibodies (mAbs) that bind to disialoganglioside (GD2), highly expressed in NBL, as a means to enable immune effector cells to destroy NBL cells via antibody-dependent cell-mediated cytotoxicity (ADCC). Preclinical data indicate that ADCC can be more effective when appropriate effector cells are activated by cytokines. Clinical studies have pursued this by administering anti-GD2 mAb in combination with ADCC-enhancing cytokines (IL2 and GM-CSF), a regimen that has demonstrated improved cancer-free survival. More recently, early clinical studies have used a fusion protein that consists of the anti-GD2 mAb directly linked to IL2, and anti-tumor responses were seen in the Phase II setting. Analyses of genes that code for receptors that influence ADCC activity and natural killer (NK) cell function [Fc receptor (FcR), killer immunoglublin-like receptor (KIR), and KIR-ligand (KIR-L)] suggest patients with anti-tumor activity are more likely to have certain genotype profiles. Further analyses will need to be conducted to determine whether these genotypes can be used as predictive markers for favorable therapeutic outcome. In this review, we discuss factors that affect response to mAb-based tumor therapies such as hu14.18-IL2. Many of our observations have been made in the context of NBL; however, we will also include some observations made with mAbs targeting other tumor types that are consistent with results in NBL. Therefore, we hypothesize that the NBL observations discussed here may also be relevant to mAb therapy for other cancers, in which ADCC is known to play a role