The gene for BLK was expressed at a 6.77-fold higher level in infant KMT2A/MLL-R+ ALL cells, 4.38-fold higher level in pediatric KMT2A/MLL-R+ ALL cells, and 21.79-fold higher level in adult KMT2A/MLL-R+ ALL cells than in normal hematopoietic cells. This evidence concerns the gene BLK and acute lymphoblastic leukemia.