The t(7;21)(p22;q22) resulting in RUNX1-USP42 fusion, is a rare but recurrent cytogenetic abnormality associated with acute myeloid leukemia (AML) and myelodysplastic syndromes.
Genetic predispositions to myeloid malignancies can be classified into three categories: familial cancer syndromes associated with increased risk of various malignancies including myelodysplasia and acute myeloid leukemia such as Li-Fraumeni syndrome and constitutional mismatch repair deficiency (CMMRD); germline mutations conferring a specific increased risk of myelodysplastic syndrome and acute myeloid leukemia such as mutations in ANKRD26, CEBPA, DDX41, ETV6, GATA2, RUNX1, SRP72 genes; and finally primarily pediatric inherited bone marrow failure syndromes such as Fanconi anemia, dyskeratosis congenita, severe congenital neutropenia, Shwachman-Diamond syndrome and Diamond Blackfan anemia.
RUNX1 deficiency has a highly variable phenotype, and MDS can occur in childhood and later in adulthood within the same families, making annual surveillance with marrow examination burdensome; however, such strategies should be discussed with affected persons, allowing an informed choice.
Higher PLA2G4A expression is associated with mutations in NRAS (P < .001), RUNX1 (P = .012), ASXL1 (P = .007), and EZH2 (P = .038), all of which are known to contribute to MDS development.
RUNX1-PDCD6 fusion resulting from a novel t(5;21)(p15;q22) chromosome translocation in myelodysplastic syndrome secondary to chronic lymphocytic leukemia.
In this study, through a combinatorial molecular approach, we characterized a novel t(5;21)(q13;q22) translocation involving RUNX1 that was acquired during the progression of myelodysplastic syndrome to acute myeloid leukemia (AML) in a pediatric patient.
The t(3;21)(q26.2;q22) translocation is a rare chromosomal abnormality exhibited almost exclusively in therapy-related myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML) or in the blastic crisis phase of chronic myelogenous leukemia, which results in the fusion of the runt related transcription factor 1 (<i>RUNX1</i>, also called <i>AML1</i>) gene at 21q22 to the myelodysplasia syndrome 1 (<i>MDS1</i>)-ecotropic virus integration site 1 (<i>EVI1</i>) complex locus (<i>MECOM</i>) at 3q26.2, generating various fusion transcripts, including <i>AML1/MDS1/EVI1</i> (<i>AME</i>).
The final three sections of the chapter cover the spectrum and clinical significance of RUNX1 point mutations in AML and myelodysplastic syndromes, in familial platelet disorder with associated myeloid malignancy, and in acute lymphoblastic leukemia.
Thus both repressor and activator functions of Runx1 at multiple hematopoietic stages and lineages likely contribute to the tumor suppressor activity in MDS and AML.
Referral reasons included (1) bone marrow failure or myelodysplastic syndrome in patients ≤ 50 years, (2) evaluation for germ-line inheritance of identified RUNX1, GATA2, or CEBPA mutations on targeted next-generation sequencing panels, and (3) strong personal and/or family history of malignancy.
RUNX1 mutations were associated with older age (16-59 years: 8.5%; ⩾60 years: 15.1%), male gender, more immature morphology and secondary AML evolving from myelodysplastic syndrome.
While the majority of mutations were constitutional, a RUNX1 mutation present in the peripheral blood at a 51% variant allele fraction was confirmed to be somatically acquired in one myelodysplastic syndrome patient.
To elucidate the role of epigenetics in RUNX inactivation, we evaluated promoter DNA methylation of RUNX1, 2, and 3 in 23 leukaemia cell lines and samples from acute myeloid leukaemia (AML), acute lymphocytic leukaemia (ALL) and myelodysplatic syndromes (MDS) patients.
One is a complex t(15;21)(q24;q22), with both breakpoints mapped at the nucleotide level, joining RUNX1 to SIN3A and UBL7-AS1 in a patient with myelodysplasia.
Mutations of RUNX1 have been reported to be associated with familial platelet disorder and with a predisposition for myelodysplasia and/or acute myeloid leukemia.
Correlation of the activities of RUNX1 mutants with the clinical outcomes revealed that patients harboring lower activities of RUNX1 mutants had a higher risk and shorter time to secondary acute myeloid leukemia transformation in MDS and CMML.
In mouse models, class I mutations such as the Bcr-Abl fusion kinase induce MPN by themselves and some class II mutations such as Runx1 mutations induce MDS.
Thirty-two percent of genes in common between the two models (2/3 NHD13 mice and 2/3 RUNX1 mice) were also hypermethylated in at least two of 19 human MDS samples.
Recent studies are shedding light on the molecular basis of myelodysplasia and how mutations and epimutations can induce and promote this neoplastic process through aberrant transcription factor function (RUNX1, ETV6, TP53), kinase signalling (FLT3, NRAS, KIT, CBL) and epigenetic deregulation (TET2, IDH1/2, DNMT3A, EZH2, ASXL1, SF3B1, U2AF1, SRSF2, ZRSR2).