Hematopoietic stem cells (HSCs) maintain an organism’s immune system for a lifetime, and derangements in HSC proliferation and differentiation result in hematologic malignancies. Chronic inflammation plays a contributory if not causal role in HSC dysfunction. Inflammation induces HSC exhaustion, which promotes the emergence of mutant clones that may be resistant to an inflammatory microenvironment; this likely promotes the onset of a myeloid hematologic malignancy. Inflammatory cytokines are characteristically high in patients with myeloid malignancies and are linked to disease initiation, symptom burden, disease progression, and worsened prognostic survival. This review will cover our current understanding of the role of inflammation in the initiation, progression, and complications of myeloid hematologic malignancies, drawing from clinical studies as well as murine models. We will also highlight inflammation as a therapeutic target in hematologic malignancies.

Philadelphia-negative myeloproliferative neoplasms (MPNs) occur when there is over-production of myeloid cells stemming from hematopoietic stem cells with constitutive activation of JAK/STAT signaling, with JAK2^V617F being the most commonly occurring somatic driver mutation. Chronic inflammation is a hallmark feature of MPNs and it is now evident that inflammation is not only a symptom of MPN but can also provoke development and precipitate progression of disease. Herein we have considered major MPN driver mutation independent host, lifestyle, and environmental factors in the pathogenesis of MPN based upon epidemiological and experimental data. In addition to the traditional risk factors such as advanced age, there is evidence to indicate that inflammatory stimuli such as smoking can promote and drive MPN clone emergence and expansion. Diet induced inflammation could also play a role in MPN clonal expansion. Recognition of factors associated with MPN development support lifestyle modifications as an emerging therapeutic tool to restrain inflammation and diminish MPN progression.

Electronic cigarettes (E-cigs) generate nicotine containing aerosols for inhalation and have emerged as a popular tobacco product among adolescents and young adults, yet little is known about their health effects due to their relatively recent introduction. Few studies have assessed the long-term effects of inhaling E-cigarette smoke or vapor. Here, we show that two months of E-cigarette exposure causes suppression of bone marrow hematopoietic stem and progenitor cells (HSPCs). Specifically, the common myeloid progenitors and granulocyte-macrophage progenitors were decreased in E-cig exposed animals compared to air exposed mice. Competitive reconstitution in bone marrow transplants was not affected by two months of E-cig exposure. When air and E-cig exposed mice were challenged with an inflammatory stimulus using lipopolysaccharide (LPS), competitive fitness between the two groups was not significantly different. However, mice transplanted with bone marrow from E-cigarette plus LPS exposed mice had elevated monocytes in their peripheral blood at five months post-transplant indicating a myeloid bias similar to responses of aged hematopoietic stem cells (HSC) to an acute inflammatory challenge. We also investigated whether E-cigarette exposure enhances the selective advantage of hematopoietic cells with myeloid malignancy associated mutations. E-cigarette exposure for one month slightly increased JAK2^V617F mutant cells in peripheral blood but did not have an impact on TET2^−/− cells. Altogether, our findings reveal that chronic E-cigarette exposure for two months alters the bone marrow HSPC populations but does not affect HSC reconstitution in primary transplants.

Hematopoietic stem cells require tight regulation to rapidly initiate emergency hematopoiesis in response to pathogens, but chronic activation leads to proliferation induced exhaustion. Timely reentry into quiescence after inflammatory stimuli is essential for long term sustained HSC maintenance. We identify IL-10R signaling, an established negative feedback regulator in mature myeloid cells, as critical for returning HSCs to quiescence. IL-10R blockade prolongs HSC cycling and sustains activated transcriptional programs after acute inflammation. With chronic exposure, blockade increases cumulative divisions and accelerates aging hallmarks, including myeloid bias, loss of polarity, and functional defects, under conditions that do not otherwise exhaust HSCs when IL-10R signaling is intact. Jak2 ^V617F mutant HSCs resist the aging acceleration induced by blockade. Consistent with this resistance, IL-10R blocking antibody promotes Jak2 ^V617F clonal expansion and augments the myeloproliferative neoplasm phenotype. Together, these findings identify IL-10R signaling as a key coordinator of post inflammatory return to quiescence and suggest that modulating this axis could preserve HSCs and shape clonal hematopoiesis. Summary: Wadley et al. show that IL-10 receptor signaling restrains inflammation-induced hematopoietic stem cell cycling and exhaustion; its blockade prolongs cycling, accelerates aging-related decline, and selectively favors Jak2 ^V617F mutant HSCs, establishing IL-10 signaling as a critical regulator of inflammatory HSC exhaustion and malignant clonal evolution.