Myelodysplastic syndrome genetics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

## Overview

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Myelodysplastic syndrome is caused by the clonal proliferation of hematopoietic precursors. Inactivation or mutation of tumor supressor gene TP53 leads to leukemic progression of Myelodysplastic syndrome.

## Genetics

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Abnormality  | Frequency in MDS

|

-5/del(5q)  | 10-20%
+8  | 10%
-7/del(7q)  | 5-10%
-Y  | 10%
17p-  | 7%
del(20q)  | 5-6%
t(11q23)  | 5-6%
complex karyotype  | 10-20%

Overall, the mutations in the RUNX1/AML1 are the most common point mutations described in MDS to date but RUNX1/AML1 mutations have no distinct hematologic phenotype and are most commonly associated with previous radiation exposure and with a higher risk disease (especially with excess blasts).

Hypermethylation leading to silencing of the p151NK-4b gene is also common in MDS. This phenomenon occurs in up to 80% of the cases with advanced MDS. The silencing of this gene can be reversed by the uyse of demethylating agents such as 5-azacytidine. These agents are pyrimidine analogues that inhibit DNA methyltransferase activity and could improve MDS hematopoiesis by reversing aberrant gene methylation and permitting cellular differentiation.

A number of studies suggest that erythropoietin (EPO) signaling and STAT5 activation is abnormal in MDS. The SOCS1 gene is hypermethylated in 31% of MDS patients which is associated with increased activity of the JAK/STAT pathway.

Microsatellite instability involving defects in the DNA mismatch repair system has been identified in some MDS patients, especially those with therapy-related disease.

The TP53 tumor suppressor gene, which regulates cell cycle progression, DNA repair and apoptosis is mutated in 5-10% of MDS cases. Inactivation of the TP53 gene may contribute to the leukemic progression from MDS.

## References

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