First-line Therapeutic Strategies for Myelodysplastic Syndromes

Targeting miR-126 disrupts maintenance of myelodysplastic syndrome stem and progenitor cells

BACKGROUND

Myelodysplastic syndrome (MDS) arises from a rare population of aberrant hematopoietic stem and progenitor cells (HSPCs). These cells are relatively quiescent and therefore treatment resistant. Understanding mechanisms underlying their maintenance is critical for effective MDS treatment.

METHODS

We evaluated microRNA-126 (miR-126) levels in MDS patients' sample and in a NUP98-HOXD13 (NHD13) murine MDS model along with their normal controls and defined its role in MDS HSPCs' maintenance by inhibiting miR-126 expression in vitro and in vivo. Identification of miR-126 effectors was conducted using biotinylated miR-126 pulldown coupled with transcriptome analysis. We also tested the therapeutic activity of our anti-miR-126 oligodeoxynucleotide (miRisten) in human MDS xenografts and murine MDS models.

RESULTS

miR-126 levels were higher in bone marrow mononuclear cells from MDS patients and NHD13 mice relative to their respective normal controls (P < 0.001). Genetic deletion of miR-126 in NHD13 mice decreased quiescence and self-renewal capacity of MDS HSPCs, and alleviated MDS symptoms of NHD13 mice. Ex vivo exposure to miRisten increased cell cycling, reduced colony-forming capacity, and enhanced apoptosis in human MDS HSPCs, but spared normal human HSPCs. In vivo miRisten administration partially reversed pancytopenia in NHD13 mice and blocked the leukemic transformation (combination group vs DAC group, P < 0.0001). Mechanistically, we identified the non-coding RNA PTTG3P as a novel miR-126 target. Lower PTTG3P levels were associated with a shorter overall survival in MDS patients.

CONCLUSIONS

MiR-126 plays crucial roles in MDS HSPC maintenance. Therapeutic targeting of miR-126 is a potentially novel approach in MDS.

Mannuronic Acid in Low-Risk and Intermediate-1-Risk Myelodysplastic Syndromes

The discovery of hematologic improvement and bone marrow modification by the drug β-D mannuronic acid (M2000) during treatment of rheumatoid arthritis in phase 1/2/3 clinical trials prompted us to design a new trial to target hematologic deficits in myelodysplastic syndromes (MDS). In this open-label, randomized phase 2 clinical trial, the potential effect and tolerability of drug M2000 was assessed in patients with low- and intermediate-1-risk MDS. The primary efficacy end point was hematologic improvement after 12 weeks of β-D-mannuronic acid therapy. Among 34 enrolled patients, half received their conventional therapy plus β-D-mannuronic acid, and the other half received only conventional drugs. In the conventional + β-D mannuronic acid treatment group, hematologic improvement and development of transfusion independence and/or reduction in transfusion requirements were seen in 12 patients (92.3%) and 1 patient (7.7%), respectively. Moreover, 5 patients (38.5%), 2 patients (15.4%), and 1 patient (7.7%) in the β-D-mannuronic acid-treated group showed hematologic improvement of the major parameters of erythroid, neutrophil, and platelet responses, respectively, based on the International Working Group criteria), whereas in the conventional treatment group as control, no hematologic improvements including erythroid, neutrophil, and platelet response was seen. In this trial, the addition of β-D mannuronic acid to conventional treatment showed promising results in MDS patients with low and intermediate-1 risk with effects on hematologic improvements without significant adverse effect.

The impact of anaemia, transfusion dependency, comorbidities and polypharmacy in elderly patients with low-risk myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are heterogeneous clonal disorders ranging from indolent conditions with a near-normal life expectancy to forms approaching acute myeloid leukaemia. Comorbid conditions have rarely been systematically studied among patients with MDS. Older age per se has a negative impact on survival of MDS patients, in particular of those with lower risk. However, age indirectly affects also the survival of higher-risk patients by limiting their eligibility to intensive treatments. In addition, ageing is associated with an increasingly high risk of developing comorbidity, and a high prevalence of comorbid diseases has indeed been reported in MDS patients. The impact of multi-morbidities/comorbidities and polypharmacy in patients with low-risk MDS patients is a poorly explored topic. We focused on medications, multi-morbidities and comorbidities of 155 low-risk MDS patients followed in the haematological outpatients clinics or in medical/oncology wards of our University Hospital. One or more comorbidities were present at diagnosis in 24 younger patients with MDS syndromes (31%), whereas 56 older patients with MDS (75%) presented 1 or more comorbidities (P < 0.001).The most frequent comorbidity was cardiac comorbidity 18% in younger patients and 25% in older patients. With no statistical significance between older and younger patients, congestive heart failure was the most frequent observed disease. Our study has shown a statistical correlation between transfusion dependency and polypathology (P = 0.0014). These data were also confirmed in a subanalysis of the younger group of patients. Our study has shown that comorbidity is very common among patients with MDS, potentially affecting the clinical course and outcome of MDS patients.

Splicing factor mutations in the myelodysplastic syndromes: target genes and therapeutic approaches

Mutations in splicing factor genes (SF3B1, SRSF2, U2AF1 and ZRSR2) are frequently found in patients with myelodysplastic syndromes (MDS), suggesting that aberrant spliceosome function plays a key role in the pathogenesis of MDS. Splicing factor mutations have been shown to result in aberrant splicing of many downstream target genes. Recent functional studies have begun to characterize the splicing dysfunction in MDS, identifying some key aberrantly spliced genes that are implicated in disease pathophysiology. These findings have led to the development of therapeutic strategies using splicing-modulating agents and rapid progress is being made in this field. Splicing inhibitors are promising agents that exploit the preferential sensitivity of splicing factor-mutant cells to these compounds. Here, we review the known target genes associated with splicing factor mutations in MDS, and discuss the potential of splicing-modulating therapies for these disorders.