Genetic abnormalities and pathophysiology of MDS

Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid malignancies characterized by peripheral blood cytopenia and dishematopoiesis and frequently progress to acute myeloid leukemia. Genetic defects play a major role in pathogenesis of MDS, including cytogenetic abnormalities, gene mutations, and abnormal gene expression. Chromosomal abnormalities have been detected in approximately 50-60% of MDS patients, including the deletions of chromosome 5q and 7q, trisomy 8, and complex karyotypes. Newer genomic technologies, such as single-nucleotide polymorphism array and next-generation sequencing, revealed the heterozygous deletions resulting in haploinsufficient gene expression (e.g., CSNK1A1, DDX41 on chromosome 5, CUX1, LUC7L2, EZH2 on chromosome 7) involved in the pathogenesis of MDS. In addition, recurrent somatic mutations in more than 50 genes have been identified in 80-90% of MDS. The most recurrent genetic mutations are involved in the RNA splicing (e.g., SF3B1, SRSF2, U2AF1, ZRSR2, LUC7L2, DDX41) and epigenetic modifications, such as histone modification (e.g., ASXL1, EZH2) and DNA methylation (e.g., TET2, DNMT3A, IDH1/IDH2). TP53 mutation is associated with aggressive disease and frequently coincides with deletion of chromosome 5q. This review summarizes the recent progress in molecular pathogenesis of MDS. A better understanding of the specific subgroups of MDS patients will also aid in the development of new therapeutic approach for MDS.