MLL-rearranged (MLLr) B-ALL (MLLr-B-ALL) has, however, an unfavorable prognosis with common therapy refractoriness and early relapse, and therefore new therapeutic targets are needed for relapsed/refractory MLLr-B-ALL.
Allogeneic stem cell transplantation improves the outcome of adults with t(1;19)/E2A-PBX1 and t(4;11)/MLL-AF4 positive B-cell acute lymphoblastic leukemia: results of the prospective multicenter LALA-94 study.
Besides age, MLL gene rearrangements showed significant association with hyperleukocytosis, peripheral blood blast percentage and early Pre-B phenotype.
Despite the small cohort size, it could be postulated that B lineage ALL with MLL abnormalities and mature phenotype is a distinct entity that differs both from the typical Pro B ALL observed in infants and mature B-ALL with high MYC expression.
Furthermore, the clinical features of this patient with the MLL-AF5q31 fusion transcript, characterized by the early pre-B phenotype (CD10(-)/CD19(+)) and poor outcome, were similar to those of patients having MLL-AF4 chimeric transcripts.
However, based on currently available data, we propose that consolidative HCT post-CART therapy be considered for all HCT-eligible patients and especially for pediatric patients with KMT2A-rearranged B-cell acute lymphoblastic leukemia.
However, rare cases of mature B-ALL with non-L3 morphology and MLL-AF9 fusion have been reported, and such cases are characterized by a rapid and aggressive clinical course.
Our data identify CD10- cytoplasmic immunoglobulin-positive pre-B ALL as a rare (2.2%) but distinct immuno-subtype of adult ALL that is characterized by a high MLL rearrangement rate and a worse outcome.
Poor prognosis BCR-ABL and MLL-AF4 was detected in two-thirds of pediatric B-ALL and is likely to be the reason for the already reported poor survival of childhood ALL in South-East Asia.
The LAF4 protein was homologous to AF4 and AF5q31 proteins that are fused to MLL in infant early pre-B ALL and the breakpoint of LAF4 was located within the region homologous to the transactivation domain of AF4 and AF5q31.
The partial nontandem duplication of the MLL (ALL1) gene is a novel rearrangement that generates three distinct fusion transcripts in B-cell acute lymphoblastic leukemia.
The pathogenesis of t(4;11)/KMT2A-AFF1<sup>+</sup> (MLL-AF4<sup>+</sup>) infant B-cell acute lymphoblastic leukemia remains difficult to model, and the pathogenic contribution in cancer of the reciprocal fusions resulting from derivative translocated-chromosomes remains obscure.