Where There’s Smoke, There’s Fire: Inflammation Drives MDS

Emerging Insights into Molecular Mechanisms of Inflammation in Myelodysplastic Syndromes

Inflammation impacts human hematopoiesis across physiologic and pathologic conditions, as signals derived from the bone marrow microenvironment, such as pro-inflammatory cytokines and chemokines, have been shown to alter hematopoietic stem cell (HSCs) homeostasis. Dysregulated inflammation can skew HSC fate-related decisions, leading to aberrant hematopoiesis and potentially contributing to the pathogenesis of hematological disorders such as myelodysplastic syndromes (MDS). Recently, emerging studies have used single-cell sequencing and muti-omic approaches to investigate HSC cellular heterogeneity and gene expression in normal hematopoiesis as well as in myeloid malignancies. This review summarizes recent reports mechanistically dissecting the role of inflammatory signaling and innate immune response activation due to MDS progression. Furthermore, we highlight the growing importance of using multi-omic techniques, such as single-cell profiling and deconvolution methods, to unravel MDSs' heterogeneity. These approaches have provided valuable insights into the patterns of clonal evolution that drive MDS progression and have elucidated the impact of inflammation on the composition of the bone marrow immune microenvironment in MDS.

Activation of distinct inflammatory pathways in subgroups of LR-MDS

Aberrant innate immune signaling has been identified as a potential key driver of the complex pathophysiology of myelodysplastic neoplasms (MDS). This study of a large, clinically and genetically well-characterized cohort of treatment-naïve MDS patients confirms intrinsic activation of inflammatory pathways in general mediated by caspase-1, interleukin (IL)-1β and IL-18 in low-risk (LR)-MDS bone marrow and reveals a previously unrecognized heterogeneity of inflammation between genetically defined LR-MDS subgroups. Principal component analysis resolved two LR-MDS phenotypes with low (cluster 1) and high (cluster 2) levels of IL1B gene expression, respectively. Cluster 1 contained 14/17 SF3B1-mutated cases, while cluster 2 contained 8/8 del(5q) cases. Targeted gene expression analysis of sorted cell populations showed that the majority of the inflammasome-related genes, including IL1B, were primarily expressed in the monocyte compartment, consistent with a dominant role in determining the inflammatory bone marrow environment. However, the highest levels of IL18 expression were found in hematopoietic stem and progenitor cells (HSPCs). The colony forming activity of healthy donor HSPCs exposed to monocytes from LR-MDS was increased by the IL-1β-neutralizing antibody canakinumab. This work reveals distinct inflammatory profiles in LR-MDS that are of likely relevance to the personalization of emerging anti-inflammatory therapies.

What Exactly Is Inflammation (and What Is It Not?)

In medicine, inflammation is a fuzzy, overused word first coined by the Romans, the intended meaning and precise definition of which varies according to the person and the clinical context. It tends to carry a negative connotation as a response gone awry, like a raging, out-of-control wildfire that requires immediate control and containment lest it destroy all in its path; however, frequently overlooked or lost in the shuffle is the primordial importance of inflammation to health and survival. The precise definition of inflammation matters for several reasons, not least because of the over-liberal use of anti-inflammatory drugs to inhibit inflammation, which may, contrary to prevailing dogma that all inflammation is harmful, act counterproductively to prevent restitutio ad integrum. Using fire as a central analogy, this overview attempts to define inflammation, the better to determine how to manage it, i.e., whether to fan its flames, let it burn out, or suppress it entirely.

Integrated analysis on mRNA microarray and microRNA microarray to screen immune-related biomarkers and pathways in myelodysplastic syndrome

BACKGROUND

Myelodysplastic syndrome (MDS) is a haematopoietic malignancy that is characterized by a heterogeneous clinical course and dysplastic maturation of blood lineages. Immune dysregulation has gained attention as one of the fundamental mechanisms responsible for the development of MDS. This study aimed to screen immune-related biomarkers and pathways in MDS.

METHODS

Differentially expressed mRNAs (DE-mRNAs) and differentially expressed microRNAs (DE-miRNAs) in different subtypes of MDS were sourced from the Gene Expression Omnibus (GEO) database. DE-mRNAs were intersected with immune-related gene sets to collect immune-related mRNAs, which were put into the Search Tool for the Retrieval of Interacting Genes (STRING) to construct protein-protein interaction (PPI) networks. Target mRNAs of DE-miRNAs were predicted using the miRDB database and intersected with screened immune-related mRNAs to construct miRNA-mRNA interaction networks. Topological analysis of constructed networks was applied to screen key molecules, which were assessed in independent datasets and previous literature. Enrichment analysis was applied to screen dysregulated pathways in MDS.

RESULTS

Screened key mRNAs were mainly from the Toll-like receptor (TLR) family, including TLR2, TLR4, TLR7, and from the chemokine family, including C-X-C motif chemokine ligand 10 (CXCL10) and CC chemokine ligand 4 (CCL4). Cytokine-cytokine receptor interactions were among the major pathways in the enrichment analysis results. Hsa-miR-30b, hsa-miR-30e and hsa-miR-221 were validated as key miRNAs and modulate cytokine-cytokine receptor interactions by targeting immune-related mRNAs.

CONCLUSION

Dysregulated cytokines reflect the immunization status in MDS. Immune-related miRNA-mRNA interactions not only provide a perspective to our understanding of immunologic derangement in the pathogenesis of MDS but also provide new therapeutic opportunities.