To investigate whether an inhibitor could be used to treat infant MLL-AF4+ ALL, we exposed SEM cells (a cell line derived from a pediatric individual with MLL-AF4 ALL) to 50 nM of the PLK1 inhibitor volasertib, a concentration that did not have cytotoxic effects in healthy natural killer (NK) cells (Gopalakrishnan et al., 2018). The gene discussed is AFF1; the disease is acute lymphoblastic leukemia.