Myelodysplastic syndromes: a review of therapeutic progress over the past 10 years

Bone Marrow Niches and Tumour Cells: Lights and Shadows of a Mutual Relationship

The bone marrow (BM) niche is the spatial structure within the intra-trabecular spaces of spongious bones and of the cavity of long bones where adult haematopoietic stem cells (HSCs) maintain their undifferentiated and cellular self-renewal state through the intervention of vascular and nervous networks, metabolic pathways, transcriptional and epigenetic regulators, and humoral signals. Within the niche, HSCs interact with various cell types such as osteoblasts, endothelial cells, macrophages, and mesenchymal stromal cells (MSCs), which maintain HSCs in a quiescent state or sustain their proliferation, differentiation, and trafficking, depending on body needs. In physiological conditions, the BM niche permits the daily production of all the blood and immune cells and their admittance/ingress/progression into the bloodstream. However, disruption of this delicate microenvironment promotes the initiation and progression of malignancies such as those included in the spectrum of myeloid neoplasms, also favouring resistance to pharmacological therapies. Alterations in the MSC population and in the crosstalk with HSCs owing to tumour-derived factors contribute to the formation of a malignant niche. On the other hand, cells of the BM microenvironment cooperate in creating a unique milieu favouring metastasization of distant tumours into the bone. In this framework, the pro-tumorigenic role of MSCs is well-documented, and few evidence suggest also an anti-tumorigenic effect. Here we will review recent advances regarding the BM niche composition and functionality in normal and in malignant conditions, as well as the therapeutic implications of the interplay between its diverse cellular components and malignant cells.

Identification of RIOK2 as a master regulator of human blood cell development

Anemia is a major comorbidity in aging, chronic kidney and inflammatory diseases, and hematologic malignancies. However, the transcriptomic networks governing hematopoietic differentiation in blood cell development remain incompletely defined. Here we report that the atypical kinase RIOK2 (right open reading frame kinase 2) is a master transcription factor (TF) that not only drives erythroid differentiation, but also simultaneously suppresses megakaryopoiesis and myelopoiesis in primary human stem and progenitor cells. Our study reveals the previously uncharacterized winged helix-turn-helix DNA-binding domain and two transactivation domains of RIOK2 that are critical to regulate key hematopoietic TFs GATA1, GATA2, SPI1, RUNX3 and KLF1. This establishes RIOK2 as an integral component of the transcriptional regulatory network governing human hematopoietic differentiation. Importantly, RIOK2 mRNA expression significantly correlates with these TFs and other hematopoietic genes in myelodysplastic syndromes, acute myeloid leukemia and chronic kidney disease. Further investigation of RIOK2-mediated transcriptional pathways should yield therapeutic approaches to correct defective hematopoiesis in hematologic disorders.

Transposable elements and Piwi‑interacting RNAs in hemato‑oncology with a focus on myelodysplastic syndrome (Review)

Our current understanding of hematopoietic stem cell differentiation and the abnormalities that lead to leukemogenesis originates from the accumulation of knowledge regarding protein‑coding genes. However, the possible impact of transposable element (TE) mobilization and the expression of P‑element‑induced WImpy testis‑interacting RNAs (piRNAs) on leukemogenesis has been beyond the scope of scientific interest to date. The expression profiles of these molecules and their importance for human health have only been characterized recently due to the rapid progress of high‑throughput sequencing technology development. In the present review, current knowledge on the expression profile and function of TEs and piRNAs was summarized, with specific focus on their reported involvement in leukemogenesis and pathogenesis of myelodysplastic syndrome.

The use of luspatercept for thalassemia in adults

Luspatercept is an activin receptor ligand trap that has been shown to enhance late-stage erythropoiesis in animal models of β-thalassemia. A multicenter, international, phase 2 dose-finding study was initiated in adult patients with β-thalassemia, either non-transfusion-dependent thalassemia (NTDT) or transfusion-dependent thalassemia (TDT). Positive results of the phase 2 study paved the way to a randomized phase 3 clinical trial (BELIEVE) to assess the efficacy and safety of luspatercept. The BELIEVE trial is a randomized, double-blind, placebo-controlled phase 3 trial. Three hundred thirty-six patients aged ≥18 years with TDT (regularly transfused, 6-20 red blood cell units within 24 weeks before randomization) were included in the trial. Patients received luspatercept or placebo subcutaneously every 21 days for ≥48 weeks and best supportive care. Forty-eight of 224 patients (21.4%) in the luspatercept group achieved the primary end points (≥33% reduction in transfusion burden) compared with those in the placebo group (4.5%; P < .001). Moreover, more patients had a ≥33% reduction in transfusion burden during any rolling 12-week interval (70.5% vs 29.5%) or any 24-week interval (41.1% vs 2.7%) with luspatercept than with the placebo. Transfusion independence was achieved by 11% of patients in the luspatercept group. Transient adverse events were more frequent with luspatercept than with placebo, but were manageable. Luspatercept was approved by the US Food and Drug Administration in 2019 and by the European Medicines Agency in 2020. The luspatercept trial is registered on www.clinicaltrials.gov at #NCT01749540 and the BELIEVE trial at #NCT02604433.