To this scope, we decided to silence the kctd15 gene in SEM cells, a B-cell precursor cell line established from the peripheral blood of a 5-year-old girl at B-ALL relapse and featured by the t(4;11) KMT2A-AFF1 (MLL-AFF1; MLL-AF4) translocation27. The gene discussed is AFF1; the disease is acute lymphoblastic leukemia.