Activation of NK cells induced death in NB cells in vitro, however, similar as for T cells, a low infiltration of NK cells was reported in tumors.163 In addition, increased MYCN levels using an inducible in vitro system led to downregulation of NK-activating ligands.164 In patients, immune escape mechanisms are responsible for impaired NK cell function. The gene discussed is MYCN; the disease is neuroblastoma.