Characterization of acute myeloid leukemia with MLL rearrangements - no increase in the incidence of coexpression of lymphoid-associated antigens on leukemic blasts

MLL gene rearrangements are associated with coexpression of myeloid- and ly mphoid-associated antigens on leukemic blasts and a dismal outcome in acute lymphoblastic leukemia (ALL). Whether the same conditions can apply to acu te myeloid leukemia (AML) is not quite clear. Rearrangements of the MLL gen e were analyzed on 113 patients with newly diagnosed de novo AML in a singl e institution. Sixteen (14%) of them showed rearranged bands by Southern bl ot analysis, including three (50%) of six Infants, three (14%) of 21 childr en between 1 and 15 years and 10(12%) of 86 adults. MLL rearrangements were not only detected in M5 (four of 12 patients, 33%) and M4 (six of 31, 19%) subtypes but also in other non-M4-M5 AML (six of 70, 9%), including M1, M2 and M7, but not M3 subtype. Seven patients had chromosomal abnormalities i nvolving 11q23, but nine did not. The latter comprised three (6%) of 48 pat ients with normal karyotype, one with t(8;21), none with t(15;17), inv(16) or t(9;22), and four (15%) of 27 with cytogenetic aberrations other than th ose specific structural abnormalities. In contrast to ALL, AML patients wit h MLL rearrangements did not tend to coexpress lymphoid- and myeloid-associ ated antigens simultaneously on leukemic blasts and have similar outcome as those without the gene rearrangements.