Molecular studies have identified a human homologue of the drosophila trithorax gene (designed HRX or MLL). MLL is a developmental regulator and is structurally altered in leukemia associated translocations that show an abnormality at band 11q23. The MLL gene on 11q23 is involved in a number of translocations with different partner chromosomes. The most common translocations observed in childhood AML are the t(9;11)(p21;q23) and the t(11;19)(q23;p13.1); other translocations of 11q23 involve at least 30 different partners chromosomes. Molecular studies have shown that MLL is rearranged more frequently than is revealed by conventional cytogenetic studies. A partial tandem duplication of MLL gene has also been reported in the majority of adult patients whose leukemic blast cells have a +11 and in some with normal karyotype. There is a strong association between AML M5/M4 and deletion and translocations involving 11q23. Sometimes cases of 11q23 M5B and M4, and occasionally M2 or M1 also show MLL rearrangement. Two clinical subgroups of patients have a high frequency of 11q23 aberration and M5 subtypes: one is AML in infants with MLL rearrangement in about 50% of cases; the other group is "secondary leukemia" (sAML) potentially after treatment with DNA topoisomerase II inhibitors. In general the translocations in these leukemia are the same as those occurring in "de novo" leukemia i.e. t(9;11), t(11;19) - Text and iconography Courtesy Georges Flandrin 2001.

MLL and partners - Editor, 06/2000, last update 09/2001. We implore researchers not to discover further MLL partners: there is no more room.