ABL1 and acute lymphoblastic leukemia: The NUP214 gene was most frequently fused to exon 2 of ABL1, but rarely to exon 3 of ABL1. In addition, the fusion gene was observed in four cell lines (31), ALL-SIL and TALL-1024 (exon 32 of NUP214 fused to exon 2 of ABL1) and PEER and BE-13 (exon 34 of NUP214 fused to exon 2 of ABL1).