Miristen

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.

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.

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.

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

Acute myeloid leukemia (AML) is a hematologic malignancy originating in the bone marrow and often progressing to extramedullary sites. Despite advances in molecularly targeted therapies and hematopoietic stem cell transplantation, clinical outcomes remain poor. Tyrosine kinase inhibitors (TKIs) provide benefit to a subset of AML patients harboring FLT3-ITD mutations; however, relapse and resistance remain common. These therapeutic failures are driven by both intrinsic properties of leukemic stem cells (LSCs)-a quiescent, self-renewing population-and extrinsic cues from the tumor microenvironment. We previously demonstrated that arteriolar endothelial cells (ECs) produce miR-126, which is transferred to LSCs, promoting quiescence, treatment resistance, and niche retention. During disease progression, TNF-α secreted by expanding blasts suppresses EC miR-126 production. Following TKI administration, blast reduction lowers TNF-ɑ levels, restoring EC miR-126 production, and this miR-126 expression enables LSCs to re-enter quiescence-thereby escaping therapy and facilitating relapse. To explore this dynamic, we developed an agent-based computational model of the AML bone marrow microenvironment, parameterized with in vitro and in vivo data. The model captures vascular niche remodeling and feedback between leukemic populations and endothelial signaling. Simulations reveal that LSC protection mediated by miR-126 can be disrupted by combining TKIs with miRisten, a miR-126 inhibitor. When administered on a defined schedule, this combination dismantles the protective niche and enhances LSC eradication. These findings underscore the therapeutic potential of targeting microenvironmental feedback to overcome resistance and prevent AML relapse.