In vitro studies have reported that PBMC-derived NK cells following stimulation with IL-2, IL-15, and/or IL-21, and depletion for alloreactive CD3/CD19 T cells, expanded faster than cytokine-induced killer (CIK) cells, and NK cells showed higher in vitro cytotoxicity against NB cells than CIK [156]. The gene discussed is IL21; the disease is neuroblastoma.