Distinct Epigenetic Subtypes Are Linked to Disease Progression in Low-Risk MDS

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal disorders characterized variably by the presence of peripheral cytopenias, bone marrow hypercellularity and dysplastic changes in the bone marrow. While MDS patients have an increased risk of progression to acute myeloid leukemia (AML), most MDS patients actually succumb to progressive bone marrow failure. Amongst patients classified as low-risk MDS, different clinical evolutions have been observed, with some patients remaining relatively stable for long periods of time (herein, stable MDS), while others show more progressive disease, with worsening cytopenias, and often increased transfusion requirements (herein, progressive MDS). Current risk stratification strategies fail to distinguish these two groups at diagnosis. We report here that these distinct behaviors are encoded at the epigenetic level and that examining DNA methylation profiles of low-risk MDS patients captures underlying differences between the two different groups. In this study, we identified 356 differentially methylated regions (DMRs) between stable and progressive low-risk MDS at the time of diagnosis. The number of DMRs was almost doubled at the time of progression (681 follow-up DMRs), and this was accompanied by an increase in the local variability at specific methylation regions, and an increase in heterogeneity over time. These findings reveal previously unrecognized epigenetic heterogeneity in low-risk MDS patients and opens the possibility for using epigenetic differences to help improve risk-stratification at diagnosis. Overall design: DNA methylation profiling in peripheral blood (PB) cells from 20 low-risk MDS patients (13 stable vs. 7 progressive low-risk MDS at the time of diagnosis and follow-up; 40 specimens in total), as well as from 4 age-matched healthy donors.