We included infant ALL samples with a KMT2A::AFF1 fusion at diagnosis (SJINF013), or at relapse (SJINF002) and AML samples with PICALM::MLLT10 (SJAML030459), NUP98::NSD1 (SJAML001441), or RUNX1::RUNX1T1 (SJAML030471) fusions. Here, AFF1 is linked to acute lymphoblastic leukemia.