Do histone deacytelase inhibitors and azacitidine combination hold potential as an effective treatment for high/very-high risk myelodysplastic syndromes?

INTRODUCTION

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disorder, predominantly seen in elderly patients with variable clinical outcome and high tendency for leukemic transformation. Allogeneic hematopoietic stem cell transplantation (alloHCT) is the only potential curative option but limited to a selected group of patients, for the rest, disease control is the goal and enrollment in clinical trial is always encouraged. Mechanistically, azacitidine (AZA) and histone deacetylase inhibitors (HDACi) is a promising combination for patient with high-risk MDS to improve clinical outcome, but the combination has yet to demonstrate its efficacy in randomized clinical trials.

AREAS COVERED

In this review the authors discuss the salient features, pharmacokinetics, safety, and efficacy data of AZA and HDACi combination in patients with MDS. Future strategies on how to possibly improve clinical outcome of patients with MDS using AZA and HDACi combination are discussed.

EXPERT OPINION

Pre-clinical and clinical data demonstrated synergistic activity of AZA and HDACi in patients with MDS. So far, the efficacy of this combination is undermined by toxicity; mainly gastrointestinal. Careful patient selection and alternative dosing schedule is needed in future clinical trials to evaluate clinical outcome.

Severe hypoxia selects hematopoietic progenitors with stem cell potential from primary Myelodysplastic syndrome bone marrow cell cultures

Myelodysplastic Syndromes (MDS) are clonal neoplasms where stem/progenitor cells endowed with self-renewal and capable of perpetuating the disease have been demonstrated. It is known that oxygen tension plays a key role in driving normal hematopoiesis and that hematopoietic stem cells are maintained in hypoxic areas of the bone marrow (BM). Hypoxia could also regulate leukemic/dysplastic hematopoiesis. We evaluated the stem cell potential of MDS cells derived from the BM of 39 MDS patients and selected under severe hypoxia. MDS cells rescued from hypoxia-incubated cultures were subjected to stem and progenitor cell assays in vitro, as well as to hematopoietic reconstitution assay in NOD-SCID mice. Incubation in severe hypoxia of cells explanted from MDS patients selected a cell subset endowed with stem cell potential, as determined in vitro. This occurred only from the BM of patients classified as IPSS low/INT-1 risk. Transplantation into NOD-SCID mice confirmed using an in vivo model that severe hypoxia selects a cell subset endowed with stem cell potential from bone marrow mononuclear cells (BMMC). derived from patients belonging to the IPSS low/int-1 risk group. Data here reported show that cells endowed with stem cell potential and capable of adapting to hypoxia and escaping hypoxia-induced apoptosis exist within MDS cell populations.