Immunotherapies for malignant melanoma are challenged by the resistance developed in a significant proportion of patients. Myeloid-derived suppressor cells (MDSC), with their ability to inhibit antitumor T-cell responses, are a major contributor to immunosuppression and resistance to immune checkpoint therapies in melanoma. Damage-associated molecular patterns S100A8, S100A9, and HMGB1, acting as toll like receptor 4 (TLR4) and receptor for advanced glycation endproducts (RAGE) ligands, are highly expressed in the tumor microenvironment and drive MDSC activation. However, the role of TLR4 and RAGE signaling in the acquisition of MDSC immunosuppressive properties remains to be better defined. Our study investigates how the signaling via TLR4 and RAGE as well as their ligands S100A9 and HMGB1, shape MDSC-mediated immunosuppression in melanoma.
MDSC were isolated from the peripheral blood of patients with advanced melanoma or generated in vitro from healthy donor-derived monocytes. Monocytes were treated with S100A9 or HMGB1 for 72 hours. The immunosuppressive capacity of treated monocytes was assessed in the inhibition of T-cell proliferation assay in the presence or absence of TLR4 and RAGE inhibitors. Plasma levels of S100A8/9 and HMGB1 were quantified by ELISA. Single-cell RNA sequencing (scRNA-seq) was performed on monocytes from patients with melanoma and healthy donors.
We showed that exposure to S100A9 and HMGB1 converted healthy donor-derived monocytes into MDSC through TLR4 signaling. Our scRNA-seq data revealed in patient monocytes enriched inflammatory genes, including S100 and those involved in NF-κB and TLR4 signaling, and a reduced major histocompatibility complex II gene expression. Furthermore, elevated plasma S100A8/9 levels correlated with shorter progression-free survival in patients with melanoma.
These findings highlight the critical role of TLR4 and, to a lesser extent, RAGE signaling in the conversion of monocytes into MDSC-like cells, underscore the potential of targeting S100A9 to prevent this conversion, and highlight the prognostic value of S100A8/9 as a plasma biomarker in melanoma.
© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Pancreatic ductal adenocarcinoma (PDAC) still has a poor response to therapies, partly due to their cancer-associated fibroblasts (CAFs). Here, we investigate the synergistic impact of a combinatory approach between a known chemotherapy agent, such as gemcitabine (GEM), and gene-modified human mesenchymal stromal/stem cells (MSCs) secreting the pro-apoptotic soluble (s)TRAIL (sTRAIL MSCs) on both PDAC cells and CAFs. The combo significantly impacts on PDAC survival in 2D and 3D models. In orthotopic xenograft models, GEM and sTRAIL MSCs induce tumor architecture shredding with a reduction of CK7- and CK8/18-positive cancer cells and the abrogation of spleen metastases. A cytotoxic effect on primary human CAFs is also observed along with an alteration of their transcriptome and a reduction of the related desmoplasia. Collectively, we demonstrate a promising therapeutic profile of combining GEM and sTRAIL MSCs to target both tumoral and stromal compartments in PDAC.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the major regulators of low-density lipoprotein receptor (LDLR). Information on role and regulation of PCSK9 in lung is very limited. Our study focuses on understanding the role and regulation of PCSK9 in the lung. PCSK9 levels are higher in Bronchoalveolar lavage fluid (BALF) of smokers with or without chronic obstructive pulmonary diseases (COPD) compared to BALF of nonsmokers. PCSK9-stimulated cells induce proinflammatory cytokines and activation of MAPKp38. PCSK9 transcripts are highly expressed in healthy individuals compared to COPD, pulmonary fibrosis or pulmonary systemic sclerosis. Cigarette smoke extract reduce PCSK9 levels in undifferentiated pulmonary bronchial epithelial cells (PBEC) but induce in differentiated PBEC. PCSK9 inhibition affect biological pathways, induces lipid peroxidation, and higher level of apoptosis in response to staurosporine. Our results suggest that higher levels of PCSK9 in BALF acts as an inflammatory marker. Furthermore, extracellular and intracellular PCSK9 play different roles.
© 2024. The Author(s).

Fluoxetine is an antidepressant drug that is heavily preferred in the cure of depression, which is from the selective serotonin reuptake inhibitor (SSRI) group. There are many reports on the effect of fluoxetine on the immune system, and its effect on the macrophage cells has never been looked at before. We aimed to demonstrate the cytokine production potential of fluoxetine antidepressant, which is widely used in the clinic, in the J774.2 cell line and its effect on PI3K and P38 pathways. The use of fluoxetine alone in J774.2 macrophage cells showed immunostimulatory properties by inducing the production of tumor necrosis factor-α (TNF-α), interleukin (IL) IL-6, IL-12p40, and granulocyte-macrophage colony-stimulating factor (GM-CSF) cytokines. It showed anti-inflammatory properties by completely stopping the production of cytokines (IL-6, IL12p40, TNF-α, and GM-CSF) at all concentrations where LPS and fluoxetine were used together. While PI3K and P38 pathways were not effective in the immunostimulatory effect in the presence of the drug agent, we found that the PI3K and P38 pathways were influenced during their anti-inflammatory activity.
© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Hematopoietic stem cell (HSC) attrition is considered the key event underlying progressive BM failure (BMF) in Fanconi anemia (FA), the most frequent inherited BMF disorder in humans. However, despite major advances, how the cellular, biochemical, and molecular alterations reported in FA lead to HSC exhaustion remains poorly understood. Here, we demonstrated in human and mouse cells that loss-of-function of FANCA or FANCC, products of 2 genes affecting more than 80% of FA patients worldwide, is associated with constitutive expression of the transcription factor microphthalmia (MiTF) through the cooperative, unscheduled activation of several stress-signaling pathways, including the SMAD2/3, p38 MAPK, NF-κB, and AKT cascades. We validated the unrestrained Mitf expression downstream of p38 in Fanca-/- mice, which display hallmarks of hematopoietic stress, including loss of HSC quiescence, DNA damage accumulation in HSCs, and reduced HSC repopulation capacity. Importantly, we demonstrated that shRNA-mediated downregulation of Mitf expression or inhibition of p38 signaling rescued HSC quiescence and prevented DNA damage accumulation. Our data support the hypothesis that HSC attrition in FA is the consequence of defects in the DNA-damage response combined with chronic activation of otherwise transiently activated signaling pathways, which jointly prevent the recovery of HSC quiescence.