Explore the vast range of titles available.

Macrophages are immune cells that originate from embryogenesis or from the differentiation of monocytes. They can adopt numerous phenotypes depending on their origin, tissue distribution and in response to different stimuli and tissue environment. Thus, in vivo , macrophages are endowed with a continuum of phenotypes that are rarely strictly pro-inflammatory or anti-inflammatory and exhibit a broad expression profile that sweeps over the whole polarization spectrum. Schematically, three main macrophage subpopulations coexist in human tissues: naïve macrophages also called M0, pro-inflammatory macrophages referred as M1 macrophages, and anti-inflammatory macrophages also known as M2 macrophages. Naïve macrophages display phagocytic functions, recognize pathogenic agents, and rapidly undergo polarization towards pro or anti-inflammatory macrophages to acquire their full panel of functions. Pro-inflammatory macrophages are widely involved in inflammatory response, during which they exert anti-microbial and anti-tumoral functions. By contrast, anti-inflammatory macrophages are implicated in the resolution of inflammation, the phagocytosis of cell debris and tissue reparation following injuries. Macrophages also play important deleterious or beneficial roles in the initiation and progression of different pathophysiological settings including solid and hematopoietic cancers. A better understanding of the molecular mechanisms involved in the generation, activation and polarization of macrophages is a prerequisite for the development of new therapeutic strategies to modulate macrophages functions in pathological situations.

CSF-1 and IL-34 share the CSF-1 receptor and no differences have been reported in the signaling pathways triggered by both ligands in human monocytes. IL-34 promotes the differentiation and survival of monocytes, macrophages and osteoclasts, as CSF-1 does. However, IL-34 binds other receptors, suggesting that differences exist in the effect of both cytokines. In the present study, we compared the differentiation and polarization abilities of human primary monocytes in response to CSF-1 or IL-34. CSF-1R engagement by one or the other ligands leads to AKT and caspase activation and autophagy induction through expression and activation of AMPK and ULK1. As no differences were detected on monocyte differentiation, we investigated the effect of CSF-1 and IL-34 on macrophage polarization into the M1 or M2 phenotype. We highlighted a striking increase in IL-10 and CCL17 secretion in M1 and M2 macrophages derived from IL-34 stimulated monocytes, respectively, compared to CSF-1 stimulated monocytes. Variations in the secretome induced by CSF-1 or IL-34 may account for their different ability to polarize naïve T cells into Th1 cells. In conclusion, our findings indicate that CSF-1 and IL-34 exhibit the same ability to induce human monocyte differentiation but may have a different ability to polarize macrophages.

Phospholipid Hydroperoxide Gluthatione Peroxidase also called Glutathione Peroxidase 4 is one of the 25 described human selenoproteins. It plays an essential role in eliminating toxic lipid hydroxy peroxides, thus inhibiting ferroptosis and favoring cell survival. GPX4 is differentially expressed according to myeloid differentiation stage, exhibiting lower expression in hematopoietic stem cells and polymorphonuclear leucocytes, while harboring higher level of expression in common myeloid progenitors and monocytes. In addition, GPX4 is highly expressed in most of acute myeloid leukemia (AML) subtypes compared to normal hematopoietic stem cells. High GPX4 expression is consistently correlated to poor prognosis in patients suffering AML. However, the role of GPX4 in the development of the myeloid lineage and in the initiation and progression of myeloid leukemia remains poorly explored. Given its essential role in the detoxification of lipid hydroperoxides, and its overexpression in most of myeloid malignancies, GPX4 inhibition has emerged as a promising therapeutic strategy to specifically trigger ferroptosis and eradicate myeloid leukemia cells. In this review, we describe the most recent advances concerning the role of GPX4 and, more generally ferroptosis in the myeloid lineage and in the emergence of AML. We also discuss the therapeutic interest and limitations of GPX4 inhibition alone or in combination with other drugs as innovative therapies to treat AML patients.

Our study explores the complex dynamics of the integrated stress response (ISR) axis, highlighting PIM2 kinase’s critical role and its interaction with the BCL2 protein family, uncovering key mechanisms of cell survival and tumor progression. Elevated PIM2 expression, a marker of various cancers, often correlates with disease aggressiveness. Using a model of normal and malignant plasma cells, we show that inhibiting PIM2 kinase inhibits phosphorylated BAD production and activates ISR-mediated NOXA expression. This shift towards MCL1 dependence underscores the synergy achieved through combined PIM/MCL1 inhibition, driven largely by ISR-mediated NOXA expression. In mouse xenograft models, dual targeting of PIM2 and MCL1 effectively controls tumor growth—a response reversed by ISR-specific inhibition and upregulation of genes linked to tumor cell dissemination. This work elucidates the molecular intricacies of PIM2 inhibition and its implications for cancer therapy, especially in tumors with elevated PIM2 expression. The integrated stress response (ISR) allows cells to restore cellular homeostasis upon a wide range of stress stimuli. Here, the authors show that PIM2 inhibition activates the ISR and promotes NOXA expression, in turn making tumour cells vulnerable to MCL1 inhibition.

Vacuolization of hematopoietic precursors cells is a common future of several otherwise non-related clinical settings such as VEXAS, Chediak–Higashi syndrome and Danon disease. Although these disorders have a priori nothing to do with one other from a clinical point of view, all share abnormal vacuolization in different cell types including cells of the erythroid/myeloid lineage that is likely the consequence of moderate to drastic dysfunctions in the ubiquitin proteasome system and/or the endo-lysosomal pathway. Indeed, the genes affected in these three diseases UBA1, LYST or LAMP2 are known to be direct or indirect regulators of lysosome trafficking and function and/or of different modes of autophagy. Furthermore, all three genes are highly expressed in the more mature myeloid cells pointing out their likely important function in these cells. LAMP2 deficiency for instance is known to be associated with alterations of lysosome architecture and function. It is thus well established that different cell types from Danon disease patients that harbor invalidating mutations in LAMP2 exhibit giant lysosomes containing undigested materials characteristic of defects in the fusion of lysosomes with autophagosomes, a feature also found in VEXAS and CHS. Other similarities regarding these three diseases include granulocyte and monocyte dysfunctions and a recurrent inflammatory climate. In the present review we discuss the possibility that some common clinical manifestations of these diseases, notably the hematopoietic ones are consecutive to a dysfunction of the endo-lysosomal pathway in myeloid/erythroid progenitors and in mature myeloid cells including neutrophiles, monocytes and macrophages. Finally, we propose reacidification as a way of reinducing lysosome functionalities and autophagy as a potential approach for a better management of these diseases.

Chaperone-mediated autophagy (CMA) ensures the selective degradation of cellular proteins endowed with a KFERQ-like motif by lysosomes. It is estimated that 30% of all cellular proteins can be directed to the lysosome for CMA degradation, but only a few substrates have been formally identified so far. Mechanistically, the KFERQ-like motifs present in substrate proteins are recognized by the molecular chaperone Hsc70c (Heat shock cognate 71 kDa protein cytosolic), also known as HSPA8, and directed to LAMP2A, which acts as the CMA receptor at the lysosomal surface. Following linearization, the protein substrate is next transported to the lumen of the lysosomes, where it is degraded by resident proteases, mainly cathepsins and eventually recycled to sustain cellular homeostasis. CMA is induced by different stress conditions, including energy deprivation that also activates macro-autophagy (MA), that may make it difficult to decipher the relative impact of both pathways on cellular homeostasis. Besides common inducing triggers, CMA and MA might be induced as compensatory mechanisms when either mechanism is altered, as it is the often the case in different pathological settings. Therefore, CMA activation can compensate for alterations of MA and vice versa. In this context, these compensatory mechanisms, when occurring, may be targeted for therapeutic purposes. Both processes have received particular attention from scientists and clinicians, since modulation of MA and CMA may have a profound impact on cellular proteostasis, metabolism, death, differentiation, and survival and, as such, could be targeted for therapeutic intervention in degenerative and immune diseases, as well as in cancer, including hematopoietic malignancies. The role of MA in cancer initiation and progression is now well established, but whether and how CMA is involved in tumorigenesis has been only sparsely explored. In the present review, we encompass the description of the mechanisms involved in CMA, its function in the physiology and pathogenesis of hematopoietic cells, its emerging role in cancer initiation and development, and, finally, the potential therapeutic opportunity to target CMA or CMA-mediated compensatory mechanisms in hematological malignancies.

Transcriptomic and metabolic profiling reveals that the creatine kinase pathway is essential for growth of acute myeloid leukemias expressing the transcription factor EVI1. Expression of the MECOM (also known as EVI1 ) proto-oncogene is deregulated by chromosomal translocations in some cases of acute myeloid leukemia (AML) and is associated with poor clinical outcome. Here, through transcriptomic and metabolomic profiling of hematopoietic cells, we reveal that EVI1 overexpression alters cellular metabolism. A screen using pooled short hairpin RNAs (shRNAs) identified the ATP-buffering, mitochondrial creatine kinase CKMT1 as necessary for survival of EVI1-expressing cells in subjects with EVI1-positive AML. EVI1 promotes CKMT1 expression by repressing the myeloid differentiation regulator RUNX1. Suppression of arginine–creatine metabolism by CKMT1 -directed shRNAs or by the small molecule cyclocreatine selectively decreased the viability, promoted the cell cycle arrest and apoptosis of human EVI1-positive cell lines, and prolonged survival in both orthotopic xenograft models and mouse models of primary AML. CKMT1 inhibition altered mitochondrial respiration and ATP production, an effect that was abrogated by phosphocreatine-mediated reactivation of the arginine–creatine pathway. Targeting CKMT1 is thus a promising therapeutic strategy for this EVI1-driven AML subtype that is highly resistant to current treatment regimens.

Targeted therapies have revolutionized cancer care. Unfortunately, most patients develop refractory, multifocal resistance to these therapies within a matter of months. Here, we demonstrate that the evolution of resistance to EGFR inhibitors in EGFR-mutant non-small cell lung cancer endows cells with hypersensitivity to a PAINS-like small molecule, MCB-613. Systematic proteomic, functional genomic, and biochemical studies revealed that MCB-613 binds KEAP1 in a covalent, cysteine-independent fashion, acting as a divalent molecular bridge that relies upon lysine residues in the KEAP1 dimerization domain to join monomers of KEAP1 together. Oligomerization of KEAP1 by MCB-613 sets into motion a fatal cascade of KEAP1 dysfunction, ROS accumulation, and ATF4/CHOP-dependent cell death. Together, these findings demonstrate that diverse models of EGFR inhibitor-resistant NSCLC share the common feature of elevated integrated stress response activity, and that a covalent molecular bridge which activates non-canonical KEAP1-ATF4 signaling can exploit this feature to select against resistance evolution. EGFR inhibitors are standard of care in patients with EGFR-mutant non-small cell lung cancer (NSCLC) but resistance often develops. Here the authors report that the evolution of EGFR inhibitor resistance in EGFR-mutant NSCLC results in a sensitivity to the compound, MCB-613, and investigate the underlying mechanism of action.

Background In clear cell renal cell carcinoma (ccRCC), first-line treatment combines nivolumab (anti-PD-1) and ipilimumab (anti-CTLA4), yielding long-term remissions but with only a 40% success rate. Our study explored the potential of enhancing ccRCC treatment by concurrently using CXCR2 inhibitors alongside immunotherapies. Methods We analyzed ELR + CXCL levels and their correlation with patient survival during immunotherapy. RCT001, a unique CXCR2 inhibitor, was examined for its mechanism of action, particularly its effects on human primary macrophages. We tested the synergistic impact of RCT001 in combination with immunotherapies in both mouse models of ccRCC and human ccRCC in the presence of human PBMC. Resuts Elevated ELR + CXCL cytokine levels were found to correlate with reduced overall survival during immunotherapy. RCT001, our optimized compound, acted as an inverse agonist, effectively inhibiting angiogenesis and reducing viability of primary ccRCC cells. It redirected M2-like macrophages without affecting M1-like macrophage polarization directed against the tumor. In mouse models, RCT001 enhanced the efficacy of anti-CTLA4 + anti-PD1 by inhibiting tumor-associated M2 macrophages and tumor-associated neutrophils. It also impacted the activation of CD4 T lymphocytes, reducing immune-tolerant lymphocytes while increasing activated natural killer and dendritic cells. Similar effectiveness was observed in human RCC tumors when RCT001 was combined with anti-PD-1 treatment. Conclusions RCT001, by inhibiting CXCR2 through its unique mechanism, effectively suppresses ccRCC cell proliferation, angiogenesis, and M2 macrophage polarization. This optimization potentiates the efficacy of immunotherapy and holds promise for significantly improving the survival prospects of metastatic ccRCC patients.

Bim is a proapoptotic member of the Bcl-2 family that shares only the BH3 domain with this family. Three Bim proteins Bim-EL, Bim-L and Bim-S are synthesized from the same transcript. We report here that Bim-EL when phosphorylated by Erk1/2 is rapidly degraded via the proteasome pathway. Using different cellular models we evidence that serine 69 is both necessary and sufficient for Erk1/2-mediated phosphorylation and degradation of Bim-EL. In K562 cells, Phorbol 12-myristate 13-acetate activates Erk1/2 and consequently increases Bim-EL phosphorylation and degradation by the proteasome, resulting in cell survival, while the Bcr-Abl inhibitor imatinib abrogates Bim-EL phosphorylation and degradation and induces caspase activation and apoptosis. We also show that Bim-EL(S69G) promotes apoptosis more efficiently than Bim-EL-WT in K562 cells. Altogether, our findings demonstrate that phosphorylation of Bim-EL by Erk1/2 on serine 69 selectively leads to its proteasomal degradation and therefore represents a new and important mechanism of Bim regulation.