Disclosed are methods and pharmaceutical compositions for treating a cancer in a subject in need thereof, the cancer characterized by proteolytic cleavage by taspase1 of the mixed-lineage leukemia 1 gene product (MLL1), the method comprising administering to the subject a therapeutic agent that inhibits cleavage by taspase1 of MLL1. Suitable therapeutic agents may include agents that inhibit the kinase activity of casein kinase II (CKII). Cancer treated by the disclosed methods and pharmaceutical compositions may include leukemia such as Acute Lymphoblastic Leukemia (ALL) and/or Acute Myeloid Leukemia (AML) and in particular, leukemia characterized by rearrangements in MLL1.
