ABSTRACT
Acute megakaryoblastic leukemia (AMKL) is a form of acute myeloid leukemia (AML) associated with a poor prognosis. The genetics and pathophysiology of AMKL are not well understood. We generated a knockin mouse model of the one twenty-two-megakaryocytic acute leukemia (OTT-MAL) fusion oncogene that results from the t(1;22)(p13;q13) translocation specifically associated with a subtype of pediatric AMKL. We report here that OTT-MAL expression deregulated transcriptional activity of the canonical Notch signaling pathway transcription factor recombination signal binding protein for immunoglobulin kappa J region (RBPJ) and caused abnormal fetal megakaryopoiesis. Furthermore, cooperation between OTT-MAL and an activating mutation of the thrombopoietin receptor myeloproliferative leukemia virus oncogene (MPL) efficiently induced a short-latency AMKL that recapitulated all the features of human AMKL, including megakaryoblast hyperproliferation and maturation block, thrombocytopenia, organomegaly, and extensive fibrosis. Our results establish that concomitant activation of RBPJ (Notch signaling) and MPL (cytokine signaling) transforms cells of the megakaryocytic lineage and suggest that specific targeting of these pathways could be of therapeutic value for human AMKL.
Subject(s)
Immunoglobulin J Recombination Signal Sequence-Binding Protein/metabolism , Leukemia, Megakaryoblastic, Acute/genetics , Oncogene Fusion , Oncogene Proteins, Fusion/genetics , Animals , Disease Models, Animal , Hematopoiesis , Humans , Leukemia, Megakaryoblastic, Acute/etiology , Leukemia, Megakaryoblastic, Acute/metabolism , Leukemia, Megakaryoblastic, Acute/pathology , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mutation , Receptors, Notch/metabolism , Receptors, Thrombopoietin/genetics , Signal Transduction , Transcription, GeneticABSTRACT
The incidence of follicular lymphoma (FL) in industrialized countries has been increasing since the 1950s. Polymorphisms in genes encoding key enzymes controlling folate-methionine metabolism, including methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MS or MTR), serine hydroxymethyltransferase (SHMT), and thymidylate synthase (TS or TYMS), modify the risk of various cancers and possibly FL. This study specifically looks for an association between MTHFR, MTR, TYMS, and SHMT polymorphisms and the risk of FL. We carried out a case-control study with 172 patients diagnosed with FL and 206 control subjects. We report that the risk of FL was doubled by the association of one mutant allele at both MTHFR polymorphisms. Individuals with MTR 2756AA had 2-fold higher risk of FL, and subjects not having at least one TYMS 2R allele showed a 2-fold higher risk of FL. The MTR 2756AA genotype conferred a greater multivariate-adjusted relative risk of FL, and the risk was multiplied by almost 5 in the TYMS2R(-)/MTR 2756AA combination. In conclusion, common polymorphisms in key enzymes of the folate-methionine metabolism pathway result in an increased risk of FL and suggest that inadequate intake of dietary folate and other methyl donor nutrients may contribute to the development of this malignancy.
Subject(s)
Enzymes/genetics , Folic Acid/metabolism , Genetic Predisposition to Disease , Lymphoma, Follicular/enzymology , Lymphoma, Follicular/genetics , Methionine/metabolism , 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/genetics , 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/metabolism , Adult , Alleles , DNA/genetics , Female , Folic Acid/blood , Genotype , Glycine Hydroxymethyltransferase/genetics , Glycine Hydroxymethyltransferase/metabolism , Humans , Lymphoma, Follicular/diagnosis , Male , Methionine/blood , Methylenetetrahydrofolate Reductase (NADPH2)/genetics , Methylenetetrahydrofolate Reductase (NADPH2)/metabolism , Middle Aged , Mutation , Polymorphism, Genetic/genetics , Risk Factors , Thymidylate Synthase/genetics , Thymidylate Synthase/metabolismABSTRACT
Most chromosomal translocations observed in T-cell acute lymphoblastic leukemia (T-ALL) often produce transcriptional activation of transcription factor oncogenes. Ectopic expression of the TLX3 (also known as HOX11L2) gene has been shown to be associated with a cryptic t(5;14)(q35;q32) translocation specific for a subtype of T-ALL. Here we report several examples of variant and alternative translocations resulting in expression of TLX3 in T-ALL, and we describe three of these translocations in detail. In particular, the CDK6 gene was rearranged in two t(5;7)(q35;q21) translocations. In two additional instances, fusion of the BCL11B (also known as CTIP2) and RANBP17/TLX3 loci were shown to result from subtle genomic insertion/deletion within these loci. This study further underscores that TLX3 expression in T-ALL is strongly associated with the presence of genomic rearrangements.
