Abstract
Myelodysplastic syndromes (MDS) traditionally have been grouped together as a disease entity based on clinical phenomena seen in association. Despite the similarities, there is great heterogeneity among the syndromes. Recent insights have shown, however, that there exists a biologically cohesive theme that unifies and thereby validates the conceptual interconnectedness. The first suggestion that such a relationship existed where biology could directly explain the observed cytopenias was the finding of excessive premature apoptosis of hematopoietic cells in MDS marrows. This apoptosis was mediated by paracrine as well as autocrine factors implicating both the seed and the soil in the pathology of the disease. Pro-inflammatory cytokines in the marrow microenvironment were mainly the paracrine mediators of apoptosis, but how the clonal cells committed suicide because of autocrine stimulation had remained a mystery for more than a decade. It has been shown now that deregulation of ribosome biogenesis can initiate a stress response in the cell through the p53 signaling pathway. Congenital anemias had been associated with mutations in ribosomal protein genes. The surprise came with the investigation of 5q- syndrome patients where haplo-insufficiency of the ribosomal protein gene RPS14 was found to be the cause of this MDS subtype. Similar ribosomal deregulation was shown to be present in all varieties of MDS patients, serving as another unifying characteristic. In addition to these findings, there are other DNA-related abnormalities such as uniparental disomy, mutations in the TET2 gene, and epigenetic phenomena that are associated with and occur across all types of MDS. This paper summarizes the themes unifying this heterogeneous group of diseases.
Highlights
Myelodysplastic syndromes (MDS) tradition- difficult to explain initially
The surn prise came with the investigation of 5q- syno drome patients where haplo-insufficiency of the N ribosomal protein gene RPS14 was found to be cytopenias in MDS, which turned out to be caused by a premature intramedullary apoptotic death of hematopoietic cells
Cell cycle studies using in vivo infusions of the thymidine analogues bromodeoxyuridine and iododeoxyuridine further demonstrated the highly expanded nature of the clone to be the result of excessive proliferation of hematopoicytokine mediated with a number of proinflammatory cytokines being over-expressed in the marrows of these patients; such as tumor necrosis factor alpha (TNFa), transforming growth factor beta (TGFb), and interleukin 1 beta (IL1b).[6,7,8,9]
Summary
Myelodysplastic syndromes (MDS) tradition- difficult to explain initially. This paper ally have been grouped together as a disease summarizes the mechanism of the underlying entity based on clinical phenomena seen in association.
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