Analyzing acute leukemia patients with complex MLL rearrangements by a sequential LDI-PCR approach

Translocations involving MLL gene are common among children with acute leukemias. Most importantly, the presence of a given MLL fusion partner dictates the outcome of patients. Patients with complex MLL rearrangements, e.g. three-way translocations could be related to a poor clinical outcome. For this purpose, we characterize 5 childhood patients with three-way translocations involving MLL gene. By LDI-PCR we identified 15 out of 17 fusion alleles and determined the localization of these breakpoints. In all cases at least one functional MLL fusion allele was present. In addition, patients displayed a remaining 3'-MLL allele that allow in principle the expression of the MLL* protein variant.