Targeting Tyro3, Axl and MerTK (TAM receptors): implications for macrophages in the tumor microenvironment

Mutual regulation of microglia and astrocytes after Gas6 inhibits spinal cord injury

JOURNAL/nrgr/04.03/01300535-202502000-00032/figure1/v/2024-05-28T214302Z/r/image-tiff Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury. Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction. However, the mechanisms involved remain unclear. In this study, we found that after spinal cord injury, resting microglia (M0) were polarized into pro-inflammatory phenotypes (MG1 and MG3), while resting astrocytes were polarized into reactive and scar-forming phenotypes. The expression of growth arrest-specific 6 (Gas6) and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury. In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia, and even inhibited the cross-regulation between them. We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway. This, in turn, inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways. In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord, thereby promoting tissue repair and motor function recovery. Overall, Gas6 may play a role in the treatment of spinal cord injury. It can inhibit the inflammatory pathway of microglia and polarization of astrocytes, attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment, and thereby alleviate local inflammation and reduce scar formation in the spinal cord.

Identification and validation of an immune-related miRNA signature for predicting prognosis of hepatocellular carcinoma

MicroRNAs play a significant role in the initiation and progression of hepatocellular carcinoma (HCC); however, their roles in immune regulation of HCC remain unclear. Our study aimed to identify an immune-related miRNA signature and explore its impact on the prognosis and tumor immune microenvironment HCC. Initially, we identified 48 differentially expressed immune-related miRNAs. Using the LASSO regression dimensionality reduction method, we constructed an immune-related miRNA signature from 12 of these miRNAs. This signature has emerged as an independent prognostic marker and is associated with the clinical stage of HCC. To elucidate the roles of the twelve-microRNA signature, we predicted their target genes. Enrichment analysis indicated that these target genes were involved in immune cell infiltration. Notably, the target genes regulated by hsa-miR-139-5p, hsa-miR-551a, and hsa-miR-7-5p showed a partial overlap. We further confirmed the differential expression of miR-7, miR-551a, miR-139-5p, and some of their overlapping target genes in tumor and non-tumor tissues derived from patients with HCC using RT-qPCR. Overall, we identified an immune-related miRNA signature that is strongly correlated with the prognosis and immune microenvironment of HCC; and confirmed the differential expression of the three most important microRNAs and their overlapping target genes in tumor and non-tumor tissues derived from HCC patients.

AXL: shapers of tumor progression and immunosuppressive microenvironments

As research progresses, our understanding of the tumor microenvironment (TME) has undergone profound changes. The TME evolves with the developmental stages of cancer and the implementation of therapeutic interventions, transitioning from an immune-promoting to an immunosuppressive microenvironment. Consequently, we focus intently on the significant role of the TME in tumor proliferation, metastasis, and the development of drug resistance. AXL is highly associated with tumor progression; however, previous studies on AXL have been limited to its impact on the biological behavior of cancer cells. An increasing body of research now demonstrates that AXL can influence the function and differentiation of immune cells, mediating immune suppression and thereby fostering tumor growth. A comprehensive analysis to identify and overcome the causes of immunosuppressive microenvironments represents a novel approach to conquering cancer. In this review, we focus on elucidating the role of AXL within the immunosuppressive microenvironments, discussing and analyzing the effects of AXL on tumor cells, T cells, macrophages, natural killer (NK) cells, fibroblasts, and other immune-stromal cells. We aim to clarify the contributions of AXL to the progression and drug resistance of cancer from its functional role in the immune microenvironment.

Phytochemicals Withanolide N and Dryobalanolide as Potential Bioactive Leads for Developing Anticancer Drugs Targeting Tyrosine-Protein Kinase Mer

There is a growing interest in harnessing natural compounds and bioactive phytochemicals to accelerate drug discovery and development, including in the treatment of human cancers. Receptor tyrosine kinases (RTKs) are critical regulators of many fundamental cellular processes and have been implicated in cancer pathogenesis as well as targets for anticancer drug development. The members of TAM, Tyro3, Axl, and MERTK subfamily RTKs, especially Mer, affect immune homeostasis in the tumor microenvironment. Hence, tyrosine-protein kinase Mer has emerged as one of the key factors in cancer susceptibility and metastasis and, by extension, as a potential target of relevance for cancer drug resistance. Here, we report, using an integrated virtual screening and simulation of phytochemicals from the IMPPAT 2.0 library, phytochemicals withanolide N and dryobalanolide as potential bioactive leads for developing anticancer drugs targeting tyrosine-protein kinase Mer. The study employed an integrated design, including physicochemical property analyses, binding affinity calculations, pan-assay interference compounds filtering, absorption, distribution, metabolism, excretion, and toxicity, and PASS analyses, in silico molecular dynamics simulations, followed by principal component analysis and free energy landscape. We call for further evaluation, validation, and translational medical research on these two phytochemicals in vitro and in vivo, with an eye to their putative therapeutic efficacy and safety in the field of oncology and anticancer drug discovery and development.

Exploring CAR-macrophages in non-tumor diseases: Therapeutic potential beyond cancer

BACKGROUND

After significant advancements in tumor treatment, personalized cell therapy based on chimeric antigen receptors (CAR) holds promise for transforming the management of various diseases. CAR-T therapy, the first approved CAR cell therapy product, has demonstrated therapeutic potential in treating infectious diseases, autoimmune disorders, and fibrosis. CAR-macrophages (CAR-Ms) are emerging as a promising approach in CAR immune cell therapy, particularly for solid tumor treatment, highlighting the feasibility of using macrophages to eliminate pathogens and abnormal cells.

AIM OF REVIEW

This review summarizes the progress of CAR-M therapy in non-tumor diseases and discusses various CAR intracellular activation domain designs and their potential to optimize therapeutic effects by modulating interactions between cellular components in the tissue microenvironment and CAR-M. Additionally, we discuss the characteristics and advantages of CAR-M therapy compared to traditional medicine and CAR-T/NK therapy, as well as the challenges and prospects for the clinical translation of CAR-M.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of CAR-M for the treatment of non-tumor diseases, analyzes the advantages and characteristics of CAR-M therapy, and highlights the important impact of CAR intracellular domain design on therapeutic efficacy. In addition, the challenges and clinical translation prospects of developing CAR-M as a new cell therapy are discussed.

Orderly Regulation of Macrophages and Fibroblasts by Axl in Bleomycin-Induced Pulmonary Fibrosis in Mice

Pulmonary fibrosis is a pathological manifestation that occurs upon lung injury and subsequence aberrant repair with poor prognosis. However, current treatment is limited and does not distinguish different disease stages. Here, we aimed to study the differential functions of Axl, a receptor tyrosine kinase expressing on both macrophages and fibroblasts, in the whole course of pulmonary fibrosis. We used mice with Axl total knockout, conditionally knockout in macrophages or fibroblasts, or treating with Axl inhibitors in inflammation or fibrosis stages to examine the effect of temporary dysfunction of Axl on bleomycin (BLM)-induced pulmonary fibrosis. Primary bone marrow-derived monocytes and primary fibroblasts from mice were used for cell-type-specific studies. Lung tissue and plasma samples were collected from idiopathic pulmonary fibrosis (IPF) patients and healthy controls to assess the Axl levels. We found that Axl inhibited the M1 polarisation of macrophages; inhibition of Axl during acute phase exacerbated inflammatory response and subsequent pulmonary fibrosis. On the other hand, Axl promoted the proliferation and invasion of the fibroblasts, partially by accelerating the focal adhesion turnover; inhibiting Axl during the fibrotic phase significantly alleviated pulmonary fibrosis. Consistently, phosphorylated Axl levels increased in fibrotic foci in the lung sample of IPF patients. In contrast, the soluble Axl (sAxl) level decreased in their plasma as compared to healthy controls. These results indicate that Axl may sequentially and differentially regulate macrophages and fibroblasts in acute and fibrosis phases, implying the necessity of a stage-specific treatment for pulmonary fibrosis. In addition, the activated Axl on fibroblasts may be reflected by the lowered plasma sAxl level, which may act as a biomarker for IPF. Trial Registration: ClinicalTrials.gov identifier: NCT03730337.

The power and the promise of CAR-mediated cell immunotherapy for clinical application in pancreatic cancer

BACKGROUND

Pancreatic cancer, referred to as the "monarch of malignancies," is a neoplastic growth mostly arising from the epithelial cells of the pancreatic duct and acinar cells. This particular neoplasm has a highly unfavorable prognosis due to its marked malignancy, inconspicuous initial manifestation, challenging early detection, rapid advancement, and limited survival duration. Cellular immunotherapy is the ex vivo culture and expansion of immune effector cells, granting them the capacity to selectively target malignant cells using specialized techniques. Subsequently, these modified cells are reintroduced into the patient's organism with the purpose of eradicating tumor cells and providing therapeutic intervention for cancer.

PRESENT SITUATION

Presently, the primary cellular therapeutic modalities employed in the treatment of pancreatic cancer encompass CAR T-cell therapy, TCR T-cell therapy, NK-cell therapy, and CAR NK-cell therapy.

AIM OF REVIEW

This review provides a concise overview of the mechanisms and primary targets associated with various cell therapies. Additionally, we will explore the prospective outlook of cell therapy in the context of treating pancreatic cancer.

The interplay between the tumor microenvironment and tumor-derived small extracellular vesicles in cancer development and therapeutic response

The tumor microenvironment (TME) plays an essential role in tumor cell survival by profoundly influencing their proliferation, metastasis, immune evasion, and resistance to treatment. Extracellular vesicles (EVs) are small particles released by all cell types and often reflect the state of their parental cells and modulate other cells' functions through the various cargo they transport. Tumor-derived small EVs (TDSEVs) can transport specific proteins, nucleic acids and lipids tailored to propagate tumor signals and establish a favorable TME. Thus, the TME's biological characteristics can affect TDSEV heterogeneity, and this interplay can amplify tumor growth, dissemination, and resistance to therapy. This review discusses the interplay between TME and TDSEVs based on their biological characteristics and summarizes strategies for targeting cancer cells. Additionally, it reviews the current issues and challenges in this field to offer fresh insights into comprehending tumor development mechanisms and exploring innovative clinical applications.

Single-cell Atlas reveals core function of CPVL/MSR1 expressing macrophages in the prognosis of triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, with the worst prognosis among all subtypes. The impact of distinct cell subpopulations within the tumor microenvironment (TME) on TNBC patient prognosis has yet to be clarified.

Methods

Utilizing single-cell RNA sequencing (scRNA-seq) integrated with bulk RNA sequencing (bulk RNA-seq), we applied Cox regression models to compute hazard ratios, and cross-validated prognostic scoring using a GLMNET-based Cox model. Cell communication analysis was used to elucidate the potential mechanisms of CPVL and MSR1. Ultimately, RNA interference-mediated gene knockdown was utilized to validate the impact of specific genes on the polarization of tumor-associated macrophages (TAMs).

Results

Our findings revealed that the function of immune cells is more pivotal in prognosis, with TAMs showing the strongest correlation with TNBC patient outcomes, compared with other immune cells. Additionally, we identified CPVL and MSR1 as critical prognostic genes within TAMs, with CPVL expression positively correlated with favorable outcomes and MSR1 expression associated with poorer prognosis. Mechanistically, CPVL may contribute to favorable prognosis by inhibiting the SPP1-CD44 ligand-receptor and promoting CXCL9-CXCR3, C3-C3AR1 ligand-receptor, through which TAMs interact with other cells such as monocytes, neutrophils, and T cells. Moreover, cytokines including IL-18, IFNγR1, CCL20, and CCL2, along with complement-related gene like TREM2 and complement component CFD, may participate in the process of CPVL or MSR1 regulating macrophage polarization. Furthermore, RT-PCR experiments confirmed that CPVL is positively associated with M1-like TAM polarization, while MSR1 is linked to M2-like TAM polarization. Finally, the prognostic significance of these two genes is also validated in HER2-positive breast cancer subtypes.

Conclusions

CPVL and MSR1 are potential biomarkers for macrophage-mediated TNBC prognosis, suggesting the therapeutic potential of macrophage targeting in TNBC.

Anti-inflammatory effects of MerTK by inducing M2 macrophage polarization via PI3K/Akt/GSK-3β pathway in gout

Mer tyrosine kinase (MerTK) has been found to regulate the secretion of inflammatory factors and exert immunosuppressive effects, but its role in gout remains unclear. In this study, we aimed to clarify the immnue effects of MerTK in gout. MerTK in synovium or serum of gout patients was determined by immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and real-time quantitative polymerase chain reaction (RT-qPCR). In monosodium urate (MSU)-induced gout mice, the effect of MerTK inhibitor (UNC2250) on inflammation and polarization was also assessed. After inhibition, knockdown or overexpression of MerTK, inflammatory response and polarization level in THP1-derived macrophages were evaluated by RT-qPCR and flow cytometry. Regulation of MerTK inhibitors on mitochondrial function and downstream pathway in THP1-derived macrophages were detected. MerTK in synovium and serum of gout patients were increased. MerTK inhibitor stimulated the inflammation and M1 polarization in MSU-induced gout mice. MerTK inhibition, knock-down, or overexpression affected inflammatory response, polarization and mitochondrial function in vitro in gout model. The PI3K/Akt/GSK-3β pathway was identified to reduce after MerTK inhibition and the relevant results were as expected, validated by knock-down or overexpressing MerTK. In conclusion, MerTK was detected to increase in both gout patients and model. MerTK influenced inflammatory response and polarization markers through PI3K/Akt/GSK-3β pathway. Interfering MerTK/PI3K/Akt/GSK-3β axis may provide a new therapeutic target for gout.

Phosphatidylserine externalization as immune checkpoint in cancer

Cancer is the second leading cause of mortality worldwide. Despite recent advances in cancer treatment including immunotherapy with immune checkpoint inhibitors, new unconventional biomarkers and targets for the detection, prognosis, and treatment of cancer are still in high demand. Tumor cells are characterized by mutations that allow their unlimited growth, program their local microenvironment to support tumor growth, and spread towards distant sites. While a major focus has been on altered tumor genomes and proteomes, crucial signaling molecules such as lipids have been underappreciated. One of these molecules is the membrane phospholipid phosphatidylserine (PS) that is usually found at cytosolic surfaces of cellular membranes but can be rapidly and massively shuttled to the extracellular leaflet of the plasma membrane during apoptosis to serve as a limiting factor for immune responses. These immunosuppressive interactions are exploited by tumor cells to evade the immune system. In this review, we describe mechanisms of immune regulation in tumors, discuss if PS may constitute an inhibitory immune checkpoint, and describe current and future strategies for targeting PS to reactivate the tumor-associated immune system.

Functions of TAM Receptors and Ligands Protein S and Gas6 in Atherosclerosis and Cardiovascular Disease

Atherosclerosis and cardiovascular disease are associated with high morbidity and mortality in industrialized nations. The Tyro3, Axl, and Mer (TAM) family of receptor tyrosine kinases is involved in the amplification or resolution of atherosclerosis pathology and other cardiovascular pathology. The ligands of these receptors, Protein S (PS) and growth arrest specific protein 6 (Gas6), are essential for TAM receptor functions in the amplification and resolution of atherosclerosis. The Axl-Gas6 interaction has various effects on cardiovascular disease. Mer and PS dampen inflammation, thereby protecting against atherosclerosis progression. Tyro3, the least studied TAM receptor in cardiovascular disease, appears to protect against fibrosis in post-myocardial infarction injury. Ultimately, PS, Gas6, and TAM receptors present an exciting avenue of potential therapeutic targets against inflammation associated with atherosclerosis and cardiovascular disease.

Mechanistic insights into the regression of atherosclerotic plaques

Atherosclerosis is a major contributor to cardiovascular diseases and mortality globally. The progression of atherosclerotic disease results in the expansion of plaques and the development of necrotic cores. Subsequent plaque rupture can lead to thrombosis, occluding blood vessels, and end-organ ischemia with consequential ischemic injury. Atherosclerotic plaques are formed by the accumulation of lipid particles overloaded in the subendothelial layer of blood vessels. Abnormally elevated blood lipid levels and impaired endothelial function are the initial factors leading to atherosclerosis. The atherosclerosis research has never been interrupted, and the previous view was that the pathogenesis of atherosclerosis is an irreversible and chronic process. However, recent studies have found that the progression of atherosclerosis can be halted when patients' blood lipid levels are reversed to normal or lower. A large number of studies indicates that it can inhibit the progression of atherosclerosis lesions and promote the regression of atherosclerotic plaques and necrotic cores by lowering blood lipid levels, improving the repair ability of vascular endothelial cells, promoting the reverse cholesterol transport in plaque foam cells and enhancing the ability of macrophages to phagocytize and clear the necrotic core of plaque. This article reviews the progress of research on the mechanism of atherosclerotic plaque regression. Our goal is to provide guidance for developing better therapeutic approaches to atherosclerosis by reviewing and analyzing the latest scientific findings.

Macrophage crosstalk and therapies: Between tumor cells and immune cells

In the tumor microenvironment, macrophages exhibit different phenotypes and functions in response to various signals, playing a crucial role in the initiation and progression of tumors. Several studies have indicated that intervention in the functions of different phenotypes of tumor-associated macrophages causes significant changes in the crosstalk between tumor cells and immune-related cells, such as T, NK, and B cells, markedly altering the course of tumor development. However, only a few specific therapeutic strategies targeting macrophages are yet available. This article comprehensively reviews the molecular biology mechanisms through which tumor-associated macrophages mediate the crosstalk between tumor cells and immune-related cells. Also, various treatment methods currently used in clinical practice and those in the clinical trial phase have been summarized, and the novel strategies for targeting tumor-associated macrophages have been categorized accordingly.

Preliminary Study of Radionuclide-Labeled MerTK-Targeting PET Imaging Agents for the Diagnosis of Melanoma

MerTK PET imaging holds potential as a promising approach for assessing tumor aggressiveness and monitoring treatment response. In this study, we synthesized a series of 18F- and 68Ga-labeled tracers derived from MerTK inhibitors for detection of MerTK expression. Among the synthesized agents, the dimeric compounds [68Ga]10 and [68Ga]12 demonstrated good in vivo and in vitro stability, high affinities to the MerTK receptor, and good MerTK-targeting specificity. Notably, [68Ga]10 exhibited a tumor uptake of 2.6 ± 0.2%ID/g at 1 h p. i. in B16F10 tumor-bearing mice, nearly tripling the uptake of its monomeric counterpart [68Ga]3. A similar enhancement was observed with [68Ga]12 compared to its monomeric analog [68Ga]6. Additionally, [18F]14 achieved a tumor uptake of 7.6 ± 0.5%ID/g at 2 h p. i., outperforming the previously reported [18F]15. Biodistribution analysis further validated the results, highlighting their potential for clinical investigation.

A Computational Approach to Characterize the Protein S-Mer Tyrosine Kinase (PROS1-MERTK) Protein-Protein Interaction Dynamics

Protein S (PROS1) has recently been identified as a ligand for the TAM receptor MERTK, influencing immune response and cell survival. The PROS1-MERTK interaction plays a role in cancer progression, promoting immune evasion and metastasis in multiple cancers by fostering a tumor-supportive microenvironment. Despite its importance, limited structural insights into this interaction underscore the need for computational studies to explore their binding dynamics, potentially guiding targeted therapies. In this study, we investigated the PROS1-MERTK interaction using advanced computational analyses to support immunotherapy research. High-resolution structural models from ColabFold, an AlphaFold2 adaptation, provided a baseline structure, allowing us to examine the PROS1-MERTK interface with ChimeraX and map residue interactions through Van der Waals criteria. Molecular dynamics (MD) simulations were conducted in GROMACS over 100 ns to assess stability and conformational changes using RMSD, RMSF, and radius of gyration (Rg). The PROS1-MERTK interface was predicted to contain a heterogeneous mix of amino acid contacts, with lysine and leucine as frequent participants. MD simulations demonstrated prominent early structural shifts, stabilizing after approximately 50 ns with small conformational shifts occurring as the simulation completed. In addition, there are various regions in each protein that are predicted to have greater conformational fluctuations as compared to others, which may represent attractive areas to target to halt the progression of the interaction. These insights deepen our understanding of the PROS1-MERTK interaction role in immune modulation and tumor progression, unveiling potential targets for cancer immunotherapy.

EDIL3/Del-1 prevents aortic dissection through enhancing internalization and degradation of apoptotic vascular smooth muscle cells

Thoracic aortic dissection (TAD) is a severe disease, characterized by numerous apoptotic vascular smooth muscle cells (VSMCs). EDIL3/Del-1 is a secreted protein involved in macrophage efferocytosis in acute inflammation. Here, we aimed to investigate whether EDIL3 promoted the internalization and degradation of apoptotic VSMCs during TAD. The levels of EDIL3 were decreased in the serum and aortic tissue from TAD mice. Global edil3 knockout (edil3-/-) mice and edil3-/- bone marrow chimeric mice exhibited a considerable exacerbation in β-aminopropionitrile monofumarate (BAPN)-induced TAD, accompanied with increased apoptotic VSMCs accumulating in the damaged aortic tissue. Two types of phagocytes, RAW264.7 cells and bone marrow-derived macrophages (BMDMs) were used for in vitro efferocytosis assay. edil3-deficient phagocytes exhibited inefficient internalization and degradation of apoptotic VSMCs. Instead, EDIL3 promoted the internalization phase through interacting with phosphatidylserine (PtdSer) on apoptotic VSMCs and binding to the macrophage ITGAV/αv-ITGB3/β3 integrin. In addition, EDIL3 accelerated the degradation phase through activating LC3-associated phagocytosis (LAP). Mechanically, following the engulfment, EDIL3 enhanced the activity of SMPD1/acid sphingomyelinase in the phagosome through blocking ITGAV-ITGB3 integrin, which facilitates phagosomal reactive oxygen species (ROS) production by NAPDH oxidase CYBB/NOX2. Furthermore, exogenous EDIL3 supplementation alleviated BAPN-induced TAD and promoted apoptotic cell clearance. EDIL3 may be a novel factor for the prevention and treatment of TAD.Abbreviations: BAPN: β-aminopropionitrile monofumarate; BMDM: bone marrow-derived macrophage; C12FDG: 5-dodecanoylaminofluorescein-di-β-D-galactopyranoside; CTRL: control; CYBB/NOX2: cytochrome b-245, beta polypeptide; DCFH-DA: 2',7'-dichlorofluorescin diacetate; EDIL3/Del-1: EGF-like repeats and discoidin I-like domains 3; EdU: 5-ethynyl-2'-deoxyuridine; EVG: elastic van Gieson; H&E: hematoxylin and eosin; IL: interleukin; LAP: LC3-associated phagocytosis; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NAC: N-acetylcysteine; PtdSer: phosphatidylserine; rEDIL3: recombinant EDIL3; ROS: reactive oxygen species; SMPD1: sphingomyelin phosphodiesterase 1; TAD: thoracic aortic dissection; TEM: transmission electron microscopy; VSMC: vascular smooth muscle cell; WT: wild-type.

Macrophage-mediated heart repair and remodeling: A promising therapeutic target for post-myocardial infarction heart failure

Heart failure (HF) remains prevalent in patients who survived myocardial infarction (MI). Despite the accessibility of the primary percutaneous coronary intervention and medications that alleviate ventricular remodeling with functional improvement, there is an urgent need for clinicians and basic scientists to further reveal the mechanisms behind post-MI HF as well as investigate earlier and more efficient treatment after MI. Growing numbers of studies have highlighted the crucial role of macrophages in cardiac repair and remodeling following MI, and timely intervention targeting the immune response via macrophages may represent a promising therapeutic avenue. Recently, technology such as single-cell sequencing has provided us with an updated and in-depth understanding of the role of macrophages in MI. Meanwhile, the development of biomaterials has made it possible for macrophage-targeted therapy. Thus, an overall and thorough understanding of the role of macrophages in post-MI HF and the current development status of macrophage-based therapy will assist in the further study and development of macrophage-targeted treatment for post-infarction cardiac remodeling. This review synthesizes the spatiotemporal dynamics, function, mechanism and signaling of macrophages in the process of HF after MI, as well as discusses the emerging bio-materials and possible therapeutic agents targeting macrophages for post-MI HF.

Single-Nuclei Transcriptome Profiling Reveals Intra-Tumoral Heterogeneity and Characterizes Tumor Microenvironment Architecture in a Murine Melanoma Model

Malignant melanoma is an aggressive cancer, with a high risk of metastasis and mortality rates, characterized by cancer cell heterogeneity and complex tumor microenvironment (TME). Single cell biology is an ideal and powerful tool to address these features at a molecular level. However, this approach requires enzymatic cell dissociation that can influence cellular coverage. By contrast, single nucleus RNA sequencing (snRNA-seq) has substantial advantages including compatibility with frozen samples and the elimination of a dissociation-induced, transcriptional stress response. To better profile and understand the functional diversity of different cellular components in melanoma progression, we performed snRNA-seq of 16,839 nuclei obtained from tumor samples along the growth of murine syngeneic melanoma model carrying a BRAFV600E mutation and collected 9 days or 23 days after subcutaneous cell injection. We defined 11 different subtypes of functional cell clusters among malignant cells and 5 different subsets of myeloid cells that display distinct global transcriptional program and different enrichment in early or advanced stage of tumor growth, confirming that this approach was useful to accurately identify intratumor heterogeneity and dynamics during tumor evolution. The current study offers a deep insight into the biology of melanoma highlighting TME reprogramming through tumor initiation and progression, underlying further discovery of new TME biomarkers which may be potentially druggable.

Myeloid Mir34a suppresses colitis-associated colon cancer: characterization of mediators by single-cell RNA sequencing

We have previously shown that general deletion of the gene encoding the p53-inducible Mir34a microRNA enhances the number and invasion of colitis-associated colorectal cancers (CACs) in mice. Since the p53-pathway has been implicated in tumor-suppression mediated by cells in the tumor microenvironment (TME) we deleted Mir34a in myeloid cells and characterized CACs in these with scRNA-Seq (single cell RNA sequencing). This revealed an increase in specific macrophage subtypes, such as Cdk8+ macrophages and Mrc1+, M2-like macrophages. The latter displayed elevated expression of 21 known Mir34a target mRNAs, including Csf1r, Axl, Foxp1, Ccr1, Nampt, and Tgfbr2, and 32 predicted Mir34a target mRNAs. Furthermore, Mir34a-deficient BMDMs showed enhanced migration, elevated expression of Csf1r and a shift towards M2-like polarization when compared to Mir34a-proficient BMDMs. Concomitant deletion of Csf1r or treatment with a Csf1r inhibitor reduced the CAC burden and invasion in these mice. Notably, loss of myeloid Mir34a function resulted in a prominent, inflammatory CAC cell subtype, which displayed epithelial and macrophage markers. These cells displayed high levels of the EMT transcription factor Zeb2 and may therefore enhance the invasiveness of CACs. Taken together, our results provide in vivo evidence for a tumor suppressive role of myeloid Mir34a in CACs which is, at least in part, mediated by maintaining macrophages in an M1-like state via repression of Mir34a targets, such as Csf1r. Collectively, these findings may serve to identify new therapeutic targets and approaches for treatment of CAC.

Discovery of Potent Azetidine-Benzoxazole MerTK Inhibitors with In Vivo Target Engagement

Inhibition of the receptor tyrosine kinase MerTK by small molecules has the potential to augment the immune response to tumors. Potent, selective inhibitors with high levels of in vivo target engagement are needed to fully evaluate the potential use of MerTK inhibitors as cancer therapeutics. We report the discovery and optimization of a series of pyrazinamide-based type 1.5 MerTK inhibitors bearing an azetidine-benzoxazole substituent. Compound 31 potently engages the target in vivo and demonstrates single agent activity in the immune-driven MC-38 murine syngeneic tumor model.

From Bench to Bedside: A Team's Approach to Multidisciplinary Strategies to Combat Therapeutic Resistance in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is diagnosed in more than 71,000 patients each year in the United States, with nearly 16,000 associated deaths. One significant hurdle in the treatment of HNSCC is acquired and intrinsic resistance to existing therapeutic agents. Over the past several decades, the University of Wisconsin has formed a multidisciplinary team to move basic scientific discovery along the translational spectrum to impact the lives of HNSCC patients. In this review, we outline key discoveries made throughout the years at the University of Wisconsin to deepen our understanding of therapeutic resistance in HNSCC and how a strong, interdisciplinary team can make significant advances toward improving the lives of these patients by combatting resistance to established therapeutic modalities. We are profoundly grateful to the many scientific teams worldwide whose groundbreaking discoveries, alongside evolving clinical paradigms in head and neck oncology, have been instrumental in making our work possible.

Discovery of A-910, a Highly Potent and Orally Bioavailable Dual MerTK/Axl-Selective Tyrosine Kinase Inhibitor

TAM receptor tyrosine kinases have emerged as promising therapeutic targets for cancer treatment due to their roles in both tumor intrinsic survival mechanisms and suppression of antitumor immunity within the tumor microenvironment. Inhibiting MerTK and Axl selectively is believed to hinder cancer cell survival, reverse the protumor myeloid phenotype, and suppress efferocytosis, thereby eliciting an antitumor immune response. In this study, we present the discovery of A-910, a highly potent and selective dual MerTK/Axl inhibitor, achieved through a structure-based medicinal chemistry campaign. The lead compound exhibits favorable oral bioavailability, exceptional kinome selectivity, and significantly improved in vivo target engagement. These findings support the use of A-910 as an orally bioavailable in vivo tool compound for investigating the immunotherapy potential of dual MerTK/Axl inhibition.

AXL as immune regulator and therapeutic target in Acute Myeloid Leukemia: from current progress to novel strategies

Until recently, treatment options for patients diagnosed with Acute Myeloid Leukemia (AML) were limited and predominantly relied on various combinations, dosages, or schedules of traditional chemotherapeutic agents. Patients with advanced age, relapsed/refractory disease or comorbidities were often left without effective treatment options. Novel advances in the understanding of leukemogenesis at the molecular and genetic levels, alongside recent progress in drug development, have resulted in the emergence of novel therapeutic agents and strategies for AML patients. Among these innovations, the receptor tyrosine kinase AXL has been established as a promising therapeutic target for AML. AXL is a key regulator of several cellular functions, including epithelial-to-mesenchymal transition in tumor cells, immune regulation, apoptosis, angiogenesis and the development of chemoresistance. Clinical studies of AXL inhibitors, as single agents and in combination therapy, have demonstrated promising efficacy in treating AML. Additionally, novel AXL-targeted therapies, such as AXL-specific antibodies or antibody fragments, present potential solutions to overcome the limitations associated with traditional small-molecule AXL inhibitors or multikinase inhibitors. This review provides a comprehensive overview of the structure and biological functions of AXL under normal physiological conditions, including its role in immune regulation. We also summarize AXL's involvement in cancer, with a specific emphasis on its role in the pathogenesis of AML, its contribution to immune evasion and drug resistance. Moreover, we discuss the AXL inhibitors currently undergoing (pre)clinical evaluation for the treatment of AML.

Targeting MERTK on tumour cells and macrophages: a potential intervention for sporadic and NF2-related meningioma and schwannoma tumours

Meningioma and schwannoma are common tumours of the nervous system. They occur sporadically or as part of the hereditary NF2-related schwannomatosis syndrome. There is an unmet need for new effective drug treatments for both tumour types. In this paper, we demonstrate overexpression/activation of TAM (TYRO3/AXL/MERTK) receptors (TAMs) and overexpression/release of ligand GAS6 in patient-derived meningioma tumour cells and tissue. For the first time, we reveal the formation of MERTK/TYRO3 heterocomplexes in meningioma and schwannoma tissue. We demonstrate the dependence of AXL and TYRO3 expression on MERTK in both tumour types, as well as interdependency of MERTK and AXL expression in meningioma. We show that MERTK and AXL contribute to increased proliferation and survival of meningioma and schwannoma cells, which we inhibited in vitro using the MERTK/FLT3 inhibitor UNC2025 and the AXL inhibitor BGB324. UNC2025 was effective in both tumour types with superior efficacy over BGB324. Finally, we found that TAMs are expressed by tumour-associated macrophages in meningioma and schwannoma tumours and that UNC2025 strongly depleted macrophages in both tumour types.

Tumor-associated macrophages: orchestrators of cholangiocarcinoma progression

Cholangiocarcinoma (CCA) is a rare but highly invasive cancer, with its incidence rising in recent years. Currently, surgery remains the most definitive therapeutic option for CCA. However, similar to other malignancies, most CCA patients are not eligible for surgical intervention at the time of diagnosis. The chemotherapeutic regimen of gemcitabine combined with cisplatin is the standard treatment for advanced CCA, but its effectiveness is often hampered by therapeutic resistance. Recent research highlights the remarkable plasticity of tumor-associated macrophages (TAMs) within the tumor microenvironment (TME). TAMs play a crucial dual role in either promoting or suppressing tumor development, depending on the factors that polarize them toward pro-tumorigenic or anti-tumorigenic phenotypes, as well as their interactions with cancer cells and other stromal components. In this review, we critically examine recent studies on TAMs in CCA, detailing the expression patterns and prognostic significance of different TAM subtypes in CCA, the mechanisms by which TAMs influence CCA progression and immune evasion, and the potential for reprogramming TAMs to enhance anticancer therapies. This review aims to provide a framework for deeper future research.

Study on the involvement of microglial S100A8 in neuroinflammation and microglia activation during migraine attacks

BACKGROUND

Microglia is the primary source of inflammatory factors during migraine attacks. This study aims to investigate the role of microglia related genes (MRGs) in migraine attacks.

METHODS

The RNA sequencing results of migraineurs and the panglaodb database were used to obtain differentially expressed genes (DEGs) in migraine related to microglia. A migraine rat model was established for validating and localizing of the MRGs, and subsequent screening for target genes was conducted. A shRNA was designed to interference the expression of target genes and administered into the trigeminal ganglion (TG) of rats. Pain sensitivity in rats was evaluated via the hot water tail-flick (HWTF) and formalin-induced pain (FIP) experiments. ELISA was used to quantify the levels of inflammatory cytokines and CGRP. WB and immunofluorescence assays were applied to detect the activation of microglia.

RESULTS

A total of five DEGs in migraine related to microglia were obtained from RNA sequencing and panglaodb database. Animal experiments showed that these genes expression were heightened in the TG and medulla oblongata (MO) of migraine rats. The gene S100A8 co-localized with microglia in both TG and MO. The HWTF and FIP experiments demonstrated that interference with S100A8 alleviated the sense of pain in migraine rats. Moreover, the levels of TNFα, IL-1β, IL-6, and CGRP in the TG and MO of rats in the model rats were increased, and the expression of microglia markers IBA-1, M1 polarization markers CD86 and iNOS was upregulated. Significantly, interference with S100A8 reversed these indicators.

CONCLUSION

Interference with S100A8 in microglia increased the pain threshold during migraine attacks, and inhibited neuroinflammation and microglia activation.

Zanzalintinib (XL092): a next-generation tyrosine kinase inhibitor-comprehensive review of early safety & efficacy data

INTRODUCTION

Zanzalintinib (XL092) is a next-generation anti-VEGFR-related multi-targeted TKI that exhibits immunomodulatory effects.

AREAS COVERED

This review explores preclinical and clinical data, along with the future directions associated with zanzalintinib and its combination with immune checkpoint inhibitors (ICIs).

EXPERT OPINION

In addition to its anti-VEGFR activity, zanzalintinib demonstrates potential synergistic effects with ICIs through its immunomodulatory impact, attributed to its inhibition of MET and TAM kinases. Recent preclinical studies provide compelling evidence supporting this synergistic potential. Furthermore, a recent phase 1 dose escalation study confirmed the tolerability of the zanzalintinib and anti-PDL1 combination without major safety concerns.Multiple ongoing clinical trials are investigating the combination of zanzalintinib and ICIs across various solid tumor types, including phase 3 studies for renal cell carcinoma, colorectal, and head and neck cancer. These trials aim to elucidate the therapeutic role of this new-generation TKI and ICI combination.However, the identification of reliable predictive biomarkers for the zanzalintinib and ICI combination presents significant challenges. Given the intricate nature of their mechanistic rationale and the difficulties in identifying reliable biomarkers for combined anti-angiogenesis and ICI therapies, addressing this challenge remains a priority for ongoing and future research.

Mertk Reduces Blood-Spinal Cord Barrier Permeability Through the Rhoa/Rock1/P-MLC Pathway After Spinal Cord Injury

Disruption of the blood-spinal cord barrier (BSCB) is a critical event in the secondary injury following spinal cord injury (SCI). Mertk has been reported to play an important role in regulating inflammation and cytoskeletal dynamics. However, the specific involvement of Mertk in BSCB remains elusive. Here, we demonstrated a distinct role of Mertk in the repair of BSCB. Mertk expression is decreased in endothelial cells following SCI. Overexpression of Mertk upregulated tight junction proteins (TJs), reducing BSCB permeability and subsequently inhibiting inflammation and apoptosis. Ultimately, this led to enhanced neural regeneration and functional recovery. Further experiments revealed that the RhoA/Rock1/P-MLC pathway plays a key role in the effects of Mertk. These findings highlight the role of Mertk in promoting SCI recovery through its ability to mitigate BSCB permeability and may provide potential targets for SCI repair.

Immunostimulatory CKb11 gene combined with immune checkpoint PD-1/PD-L1 blockade activates immune response and simultaneously overcomes the immunosuppression of cancer

Immunosuppression tumor microenvironment (TME) seriously impedes anti-tumor immune response, resulting in poor immunotherapy effect of cancer. This study develops a folate-modified delivery system to transport the plasmids encoding immune stimulatory chemokine CKb11 and PD-L1 inhibitors to tumor cells, resulting in high CKb11 secretion from tumor cells, successfully activating immune cells and increasing cytokine secretion to reshape the TME, and ultimately delaying tumor progression. The chemokine CKb11 enhances the effectiveness of tumor immunotherapy by increasing the infiltration of immune cells in TME. It can cause high expression of IFN-γ, which is a double-edged sword that inhibits tumor growth while causing an increase in the expression of PD-L1 on tumor cells. Therefore, combining CKb11 with PD-L1 inhibitors can counterbalance the suppressive impact of PD-L1 on anti-cancer defense, leading to a collaborative anti-tumor outcome. Thus, utilizing nanotechnology to achieve targeted delivery of immune stimulatory chemokines and immune checkpoint inhibitors to tumor sites, thereby reshaping immunosuppressive TME for cancer treatment, has great potential as an immunogene therapy in clinical applications.

Reshaping the tumor immune microenvironment to improve CAR-T cell-based cancer immunotherapy

In many hematologic malignancies, the adoptive transfer of chimeric antigen receptor (CAR) T cells has demonstrated notable success; nevertheless, further improvements are necessary to optimize treatment efficacy. Current CAR-T therapies are particularly discouraging for solid tumor treatment. The immunosuppressive microenvironment of tumors affects CAR-T cells, limiting the treatment's effectiveness and safety. Therefore, enhancing CAR-T cell infiltration capacity and resolving the immunosuppressive responses within the tumor microenvironment could boost the anti-tumor effect. Specific strategies include structurally altering CAR-T cells combined with targeted therapy, radiotherapy, or chemotherapy. Overall, monitoring the tumor microenvironment and the status of CAR-T cells is beneficial in further investigating the viability of such strategies and advancing CAR-T cell therapy.

Role of tumor-associated macrophages in hepatocellular carcinoma: impact, mechanism, and therapy

Hepatocellular carcinoma (HCC) is a highly frequent malignancy worldwide. The occurrence and progression of HCC is a complex process closely related to the polarization of tumor-associated macrophages (TAMs) in the tumor microenvironment (TME). The polarization of TAMs is affected by a variety of signaling pathways and surrounding cells. Evidence has shown that TAMs play a crucial role in HCC, through its interaction with other immune cells in the TME. This review summarizes the origin and phenotypic polarization of TAMs, their potential impacts on HCC, and their mechanisms and potential targets for HCC immunotherapy.

Gas6-Axl signal promotes indoor VOCs exposure-induced pulmonary fibrosis via pulmonary microvascular endothelial cells-fibroblasts cross-talk

Volatile organic compounds (VOCs) as environmental pollutants were associated with respiratory diseases. Pulmonary fibrosis (PF) was characterized by an increase of extracellular matrix, leading to deterioration of lung function. The adverse effects on lung and the potential mechanism underlying VOCs induced PF had not been elucidated clearly. In this study, the indoor VOCs exposure mouse model along with an ex vivo biosensor assay was established. Based on scRNA-seq analysis, the adverse effects on lung and potential molecular mechanism were studied. Herein, the results showed that VOCs exposure from indoor decoration contributed to decreased lung function and facilitated pulmonary fibrosis in mice. Then, the whole lung cell atlas after VOCs exposure and the heterogeneity of fibroblasts were revealed. We explored the molecular interactions among various pulmonary cells, suggesting that endothelial cells contributed to fibroblasts activation in response to VOCs exposure. Mechanistically, pulmonary microvascular endothelial cells (MPVECs) secreted Gas6 after VOCs-induced PANoptosis phenotype, bound to the Axl in fibroblasts, and then activated fibroblasts. Moreover, Atf3 as the key gene negatively regulated PANoptosis phenotype to ameliorate fibrosis induced by VOCs exposure. These novel findings provided a new perspective about MPVECs could serve as the initiating factor of PF induced by VOCs exposure.

Induction of osteoblast apoptosis stimulates macrophage efferocytosis and paradoxical bone formation

Apoptosis is crucial for tissue homeostasis and organ development. In bone, apoptosis is recognized to be a main fate of osteoblasts, yet the relevance of this process remains underexplored. Using our murine model with inducible Caspase 9, the enzyme that initiates intrinsic apoptosis, we triggered apoptosis in a proportion of mature osteocalcin (OCN+) osteoblasts and investigated the impact on postnatal bone development. Osteoblast apoptosis stimulated efferocytosis by osteal macrophages. A five-week stimulation of OCN+ osteoblast apoptosis in 3-week-old male and female mice significantly enhanced vertebral bone formation while increasing osteoblast precursors. A similar treatment regimen to stimulate osterix+ cell apoptosis had no impact on bone volume or density. The vertebral bone accrual following stimulation of OCN+ osteoblast apoptosis did not translate in improved mechanical strength due to disruption of the lacunocanalicular network. The observed bone phenotype was not influenced by changes in osteoclasts but was associated with stimulation of macrophage efferocytosis and vasculature formation. Phenotyping of efferocytic macrophages revealed a unique transcriptomic signature and expression of factors including VEGFA. To examine whether macrophages participated in the osteoblast precursor increase following osteoblast apoptosis, macrophage depletion models were employed. Depletion of macrophages via clodronate-liposomes and the CD169-diphtheria toxin receptor mouse model resulted in marked reduction in leptin receptor+ and osterix+ osteoblast precursors. Collectively, this work demonstrates the significance of osteoblast turnover via apoptosis and efferocytosis in postnatal bone formation. Importantly, it exposes the potential of targeting this mechanism to promote bone anabolism in the clinical setting.

Phenotypic and Functional Outcomes in Macrophages Exposed to an Environmentally Relevant Mixture of Organophosphate Esters in Vitro

BACKGROUND

Organophosphate esters (OPEs) are flame retardants and plasticizers used in consumer products. OPEs are found ubiquitously throughout the environment with high concentrations in indoor house dust. Exposure to individual OPEs is associated with immune dysfunction, particularly in macrophages. However, OPEs exist as complex mixtures and the effects of environmentally relevant mixtures on the immune system have not been investigated.

OBJECTIVES

The objectives of this study were to evaluate the toxicity of an environmentally relevant mixture of OPEs that models Canadian house dust on macrophages using phenotypic and functional assessments in vitro.

METHODS

High-content live-cell fluorescent imaging for phenotypic biomarkers of toxicity in THP-1 macrophages treated with the OPE mixture was undertaken. We used confocal microscopy and cholesterol analysis to validate and expand on the observed OPE-induced lipid phenotype. Then, we used flow cytometry and live-cell imaging to conduct functional tests and uncover mechanisms of OPE-induced phagocytic suppression. Finally, we validated our THP-1 findings in human primary peripheral blood mononuclear cells (hPBMC) derived macrophages.

RESULTS

Exposure to non-cytotoxic dilutions of the OPE mixture resulted in higher oxidative stress and disrupted lysosome and lipid homeostasis in THP-1 and primary macrophages. We further observed that phagocytosis of apoptotic cells in THP-1 and primary macrophages was lower in OPE-exposed cells vs. controls. In THP-1 macrophages, phagocytosis of both Gram-positive and Gram-negative bacteria was also lower in OPE-exposed cells vs. controls. Additionally, the OPE mixture altered the expression of phagocytic receptors linked to the recognition of phosphatidylserine and pathogen-associated molecular patterns.

DISCUSSION

The results of this in vitro study suggested that exposure to an environmentally relevant mixture of OPEs resulted in higher lipid retention in macrophages and poor efferocytic response. These effects could translate to enhanced foam cell generation resulting in higher cardiovascular mortality. Furthermore, bacterial phagocytosis was lower in OPE-exposed macrophages in an in vitro setting, which may indicate the potential for reduced bacterial clearance in models of infections. Taken together, our data provide strong evidence that mixtures of OPEs can influence the biology of macrophages and offer new mechanistic insights into the impact of OPE mixtures on the immune system. https://doi.org/10.1289/EHP13869.

Strategies for overcoming tumour resistance to immunotherapy: harnessing the power of radiation therapy

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; yet their efficacy remains variable across patients. This review delves into the intricate interplay of tumour characteristics contributing to resistance against ICI therapy and suggests that combining with radiotherapy holds promise. Radiation, known for its ability to trigger immunogenic cell death and foster an in situ vaccination effect, may counteract these resistance mechanisms, enhancing ICI response and patient outcomes. However, particularly when delivered at high-dose, it may trigger immunosuppressive mechanism and consequent side-effects. Notably, low-dose radiotherapy (LDRT), with its capacity for tumour reprogramming and reduced side effects, offers the potential for widespread application. Preclinical and clinical studies have shown encouraging results in this regard.

Unraveling cardiomyocyte responses and intercellular communication alterations in primary carnitine deficiency cardiomyopathy via single-nucleus RNA sequencing

Background

Primary Carnitine Deficiency (PCD) is a potentially life-threatening autosomal recessive monogenic disorder arising from mutations in the organic cation transporter 2 (OCTN2) gene. Dilated cardiomyopathy (DCM) is a prevalent symptom associated with this condition, and episodes of metabolic disturbance may lead to sudden death. However, the pathogenic mechanism remains unclear. Here, we sought to investigate the response of cardiomyocytes and alterations in the intercellular communication in individuals with PCD DCM.

Methods

The GSE211650 dataset was downloaded. Subsequently, modular analysis was performed using hdWGCNA. SCENIC was employed for transcription factor analysis. Monocle2 and SCP were applied to conduct trajectory inference and characterize dynamic features. CellChat was used to investigate intercellular interactions.

Results

OCTN2-deficient cardiomyocytes displayed transcriptomic alterations indicative of reduced contractility, developmental abnormalities, and fibrosis. The reduced expression of genes encoding troponin, myosin, and calcium ion transporters may underlie the observed decrease in contractility. Suppressed Wnt signaling and downregulated transcription factors associated with myocardial development suggest potential developmental disturbances in cardiomyocytes. Growth arrest-specific 6 (GAS6) secreted by TNNC1 high cardiomyocytes is implicated in myocardial inflammation and fibrosis. Macrophages-derived secreted phosphoprotein 1 (SPP1) promotes the activation of fibroblasts. Furthermore, there was a reduction in neuronal genes in the OCTN2-deficient group.

Conclusions

Our research has unveiled, for the first time, the responses of cardiomyocytes and alterations in the intercellular communication in PCD DCM, offering valuable insights for the precision treatment of this condition.

Could Gas6/TAM Axis Provide Valuable Insights into the Pathogenesis of Systemic Sclerosis?

Systemic sclerosis (SSc) is a connective tissue disorder characterized by microvascular injury, extracellular matrix deposition, autoimmunity, inflammation, and fibrosis. The clinical complexity and high heterogeneity of the disease make the discovery of potential therapeutic targets difficult. However, the recent progress in the comprehension of its pathogenesis is encouraging. Growth Arrest-Specific 6 (Gas6) and Tyro3, Axl, and MerTK (TAM) receptors are involved in multiple biological processes, including modulation of the immune response, phagocytosis, apoptosis, fibrosis, inflammation, cancer development, and autoimmune disorders. In the present manuscript, we review the current evidence regarding SSc pathogenesis and the role of the Gas6/TAM system in several human diseases, suggesting its likely contribution in SSc and highlighting areas where further research is necessary to fully comprehend the role of TAM receptors in this condition. Indeed, understanding the involvement of TAM receptors in SSc, which is currently unknown, could provide valuable insights for novel potential therapeutic targets.

Discovery of Dual MER/AXL Kinase Inhibitors as Bifunctional Small Molecules for Inhibiting Tumor Growth and Enhancing Tumor Immune Microenvironment

A series of bifunctional compounds have been discovered for their dual functionality as MER/AXL inhibitors and immune modulators. The furanopyrimidine scaffold, renowned for its suitability in kinase inhibitor discovery, offers at least three distinct pharmacophore access points. Insights from molecular modeling studies guided hit-to-lead optimization, which revealed that the 1,3-diketone side chain hybridized with furanopyrimidine scaffold that respectively combined amino-type substituent and 1H-pyrazol-4-yl substituent on the top and bottom of the aryl regions to produce 22 and 33, exhibiting potent antitumor activities in various syngeneic and xenograft models. More importantly, 33 demonstrated remarkable immune-modulating activity by upregulating the expression of total T-cells, cytotoxic CD8+ T-cells, and helper CD4+ T-cells in the spleen. These findings underscored the bifunctional capabilities of 33 (BPR5K230) with excellent oral bioavailability (F = 54.6%), inhibiting both MER and AXL while modulating the tumor microenvironment and highlighting its diverse applicability for further studies to advance its therapeutic potential.

"Find Me" and "Eat Me" signals: tools to drive phagocytic processes for modulating antitumor immunity

Phagocytosis, a vital defense mechanism, involves the recognition and elimination of foreign substances by cells. Phagocytes, such as neutrophils and macrophages, rapidly respond to invaders; macrophages are especially important in later stages of the immune response. They detect "find me" signals to locate apoptotic cells and migrate toward them. Apoptotic cells then send "eat me" signals that are recognized by phagocytes via specific receptors. "Find me" and "eat me" signals can be strategically harnessed to modulate antitumor immunity in support of cancer therapy. These signals, such as calreticulin and phosphatidylserine, mediate potent pro-phagocytic effects, thereby promoting the engulfment of dying cells or their remnants by macrophages, neutrophils, and dendritic cells and inducing tumor cell death. This review summarizes the phagocytic "find me" and "eat me" signals, including their concepts, signaling mechanisms, involved ligands, and functions. Furthermore, we delineate the relationships between "find me" and "eat me" signaling molecules and tumors, especially the roles of these molecules in tumor initiation, progression, diagnosis, and patient prognosis. The interplay of these signals with tumor biology is elucidated, and specific approaches to modulate "find me" and "eat me" signals and enhance antitumor immunity are explored. Additionally, novel therapeutic strategies that combine "find me" and "eat me" signals to better bridge innate and adaptive immunity in the treatment of cancer patients are discussed.

Dysregulated inflammatory response to urogynecologic meshes in women with diabetes and its implications

BACKGROUND

Diabetes is an independent risk factor for mesh complications in women undergoing mesh-augmented surgical repairs of stress urinary incontinence and/or pelvic organ prolapse. The underlying mechanism remains unclear.

OBJECTIVE

This study aimed to define the diabetes-associated alterations in the host inflammatory response to mesh and correlate them with perioperative glucose management.

STUDY DESIGN

Deidentified demographics and medical records of patients who underwent mesh removal and participated in a mesh biorepository study were reviewed (n=200). In patients with diagnosed diabetes (n=25), blood glucose management before initial mesh implantation and before and after mesh removal was assessed by blood glucose and hemoglobin A1c levels. Age- and body mass index-matched tissue samples excised from patients with and without diabetes were examined. Transcriptomic profiles of immune cell markers, immune mediators, key inflammatory regulators, cell senescence, and epigenetic enzymes were determined by multiplex transcriptomic assays (NanoString). Ratios of apoptotic cells to CD68+ macrophages were examined with immunofluorescence. Protein profiles of 12 molecules involved in apoptotic cell clearance were examined with a multiplex protein assay (Luminex).

RESULTS

Demographic and clinical characteristics, including duration between mesh implantation and removal, reason for removal, and type of mesh, etc., were comparable between patients with and without diabetes, except for 11.6% higher body mass index in the former (P=.005). In patients with diabetes, suboptimal management of blood glucose following mesh implantation was observed, with 59% of the patients having loosely or poorly controlled glucose before and after the mesh removal. Ongoing chronic inflammatory response was observed in the excised mesh-tissue complexes in both groups, whereas markers for M2 macrophages (Mrc1 [mannose receptor C-type 1]) and helper T cells (Cd4 [CD4 molecule]) were increasingly expressed in the diabetic vs nondiabetic group (P=.023 and .047, respectively). Furthermore, the gene expressions of proinflammatory Ccl24 (C-C motif chemokine ligand 24) and Ccl13 (C-C motif chemokine ligand 13) were upregulated by 1.5- and 1.8-fold (P=.035 and .027, respectively), whereas that of Il1a (interleukin 1 alpha) was paradoxically downregulated by 2.2-fold (P=.037) in the diabetic vs nondiabetic group. Interestingly, strong positive correlations were found between the expression of Ccl13, Setdb2 (SET domain bifurcated histone lysine methyltransferase 2), and M2 macrophage markers, and between the expression of Il1a, Fosl1 (activator protein-1 transcription factor subunit), and dendritic cell markers, suggesting the involvement of macrophages and dendritic cells in the diabetes-dysregulated proinflammatory response. Supportively, apoptotic cell clearance, which is an important function of macrophages, appeared to be impaired in the diabetic group, with a significantly increased protein level of CALR (calreticulin), an "eat-me" signal on the surface of apoptotic cells (P=.031), along with an increase of AXL (AXL receptor tyrosine kinase) (P=.030), which mediates apoptotic cell clearance.

CONCLUSION

Diabetes was associated with altered long-term inflammatory response in complicated mesh implantation, particularly involving innate immune cell dysfunction. Suboptimal blood glycemic control following mesh implantation may contribute to this immune dysregulation, necessitating further mechanistic studies.

Immunotherapies Targeting Tumor-Associated Macrophages (TAMs) in Cancer

Tumor-associated macrophages (TAMs) are one of the most plentiful immune compositions in the tumor microenvironment, which are further divided into anti-tumor M1 subtype and pro-tumor M2 subtype. Recent findings found that TAMs play a vital function in the regulation and progression of tumorigenesis. Moreover, TAMs promote tumor vascularization, and support the survival of tumor cells, causing an impact on tumor growth and patient prognosis. Numerous studies show that reducing the density of TAMs, or modulating the polarization of TAMs, can inhibit tumor growth, indicating that TAMs are a promising target for tumor immunotherapy. Recently, clinical trials have found that treatments targeting TAMs have achieved encouraging results, and the U.S. Food and Drug Administration has approved a number of drugs for use in cancer treatment. In this review, we summarize the origin, polarization, and function of TAMs, and emphasize the therapeutic strategies targeting TAMs in cancer treatment in clinical studies and scientific research, which demonstrate a broad prospect of TAMs-targeted therapies in tumor immunotherapy.

Co-targeting JAK1/STAT6/GAS6/TAM signaling improves chemotherapy efficacy in Ewing sarcoma

Ewing sarcoma is a pediatric bone and soft tissue tumor treated with chemotherapy, radiation, and surgery. Despite intensive multimodality therapy, ~50% patients eventually relapse and die of the disease due to chemoresistance. Here, using phospho-profiling, we find Ewing sarcoma cells treated with chemotherapeutic agents activate TAM (TYRO3, AXL, MERTK) kinases to augment Akt and ERK signaling facilitating chemoresistance. Mechanistically, chemotherapy-induced JAK1-SQ phosphorylation releases JAK1 pseudokinase domain inhibition allowing for JAK1 activation. This alternative JAK1 activation mechanism leads to STAT6 nuclear translocation triggering transcription and secretion of the TAM kinase ligand GAS6 with autocrine/paracrine consequences. Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

Multiomics integration-based immunological characterizations of adamantinomatous craniopharyngioma in relation to keratinization

Although adamantinomatous craniopharyngioma (ACP) is a tumour with low histological malignancy, there are very few therapeutic options other than surgery. ACP has high histological complexity, and the unique features of the immunological microenvironment within ACP remain elusive. Further elucidation of the tumour microenvironment is particularly important to expand our knowledge of potential therapeutic targets. Here, we performed integrative analysis of 58,081 nuclei through single-nucleus RNA sequencing and spatial transcriptomics on ACP specimens to characterize the features and intercellular network within the microenvironment. The ACP environment is highly immunosuppressive with low levels of T-cell infiltration/cytotoxicity. Moreover, tumour-associated macrophages (TAMs), which originate from distinct sources, highly infiltrate the microenvironment. Using spatial transcriptomic data, we observed one kind of non-microglial derived TAM that highly expressed GPNMB close to the terminally differentiated epithelial cell characterized by RHCG, and this colocalization was verified by asmFISH. We also found the positive correlation of infiltration between these two cell types in datasets with larger cohort. According to intercellular communication analysis, we report a regulatory network that could facilitate the keratinization of RHCG+ epithelial cells, eventually causing tumour progression. Our findings provide a comprehensive analysis of the ACP immune microenvironment and reveal a potential therapeutic strategy base on interfering with these two types of cells.

Targeting Tyro3, Axl, and MerTK Receptor Tyrosine Kinases Significantly Sensitizes Triple-Negative Breast Cancer to CDK4/6 Inhibition

Triple-negative breast cancer (TNBC) is the most aggressive subtype with high metastasis and mortality rates. Given the lack of actionable targets such as ER and HER2, TNBC still remains an unmet therapeutic challenge. Despite harboring high CDK4/6 expression levels, the efficacy of CDK4/6 inhibition in TNBC has been limited due to the emergence of resistance. The resistance to CDK4/6 inhibition is mainly mediated by RB1 inactivation. Since our aim is to overcome resistance to CDK4/6 inhibition, in this study, we primarily used the cell lines that do not express RB1. Following a screening for activated receptor tyrosine kinases (RTKs) upon CDK4/6 inhibition, we identified the TAM (Tyro3, Axl, and MerTK) RTKs as a crucial therapeutic vulnerability in TNBC. We show that targeting the TAM receptors with a novel inhibitor, sitravatinib, significantly sensitizes TNBC to CDK4/6 inhibitors. Upon prolonged HER2 inhibitor treatment, HER2+ breast cancers suppress HER2 expression, physiologically transforming into TNBC-like cells. We further show that the combined treatment is highly effective against drug-resistant HER2+ breast cancer as well. Following quantitative proteomics and RNA-seq data analysis, we extended our study into the immunophenotyping of TNBC. Given the roles of the TAM receptors in promoting the creation of an immunosuppressive tumor microenvironment (TME), we further demonstrate that the combination of CDK4/6 inhibitor abemaciclib and sitravatinib modifies the immune landscape of TNBC to favor immune checkpoint blockade. Overall, our study offers a novel and highly effective combination therapy against TNBC and potentially treatment-resistant HER2+ breast cancer that can be rapidly moved to the clinic.

Knocking down of Xkr8 enhances chemotherapy efficacy through modulating tumor immune microenvironment

Scramblase Xk-related protein 8 (Xkr8) regulates the externalization of phosphatidylserine (PS) during apoptosis and holds a pivotal role in fostering tumor immunosuppression. Targeting Xkr8 in conjunction with chemotherapy demonstrated a novel avenue for amplifying antitumor immune response and overcoming chemo-immune resistance. Here we further evaluated this strategy by using a clinically relevant orthotopic model and elucidated the mechanism through in-depth single-cell RNA sequencing (scRNA-seq). We found that Xkr8 knockdown exhibited the potential to lead to immunogenic cell death (ICD) by impeding the normal clearance of apoptotic cells. Co-delivery of Xkr8 small interference RNA (siRNA) and a prodrug conjugate of 5-fluorouracil (5-Fu) and oxoplatin (FuOXP) showed remarkable therapeutic efficacy in an orthotopic pancreatic tumor model with increased infiltration of proliferative NK cells and activated macrophages in the tumor microenvironment (TME). Single-cell trajectory analysis further unveiled that tumor infiltrating CD8+ T cells are differentiated favorably to cytotoxic over exhausted phenotype after combination treatment. Our study sheds new light on the impact of Xkr8 knockdown on TME and solidifies the rationale of combining Xkr8 knockdown with chemotherapy to treat various types of cancers.

Immunological role of Gas6/TAM signaling in hemostasis and thrombosis

The immune system is an emerging regulator of hemostasis and thrombosis. The concept of immunothrombosis redefines the relationship between coagulation and immunomodulation, and the Gas6/Tyro3-Axl-MerTK (TAM) signaling pathway builds the bridge across them. During coagulation, Gas6/TAM signaling pathway not only activates platelets, but also promotes thrombosis through endothelial cells and vascular smooth muscle cells involved in inflammatory responses. Thrombosis appears to be a common result of a Gas6/TAM signaling pathway-mediated immune dysregulation. TAM TK and its ligands have been found to be involved in coagulation through the PI3K/AKT or JAK/STAT pathway in various systemic diseases, providing new perspectives in the understanding of immunothrombosis. Gas6/TAM signaling pathway serves as a breakthrough target for novel therapeutic strategies to improve disease management. Many preclinical and clinical studies of TAM receptor inhibitors are in process, confirming the pivotal role of Gas6/TAM signaling pathway in immunothrombosis. Therapeutics targeting the TAM receptor show potential both in anticoagulation management and immunotherapy. Here, we review the immunological functions of the Gas6/TAM signaling pathway in coagulation and its multiple mechanisms in diseases identified to date, and discuss the new clinical strategies that may generated by these roles.

A novel insight into cancer therapy: Lipid metabolism in tumor-associated macrophages

The tumor immune microenvironment (TIME) can limit the effectiveness and often leads to significant side effects of conventional cancer therapies. Consequently, there is a growing interest in identifying novel targets to enhance the efficacy of targeted cancer therapy. More research indicates that tumor-associated macrophages (TAMs), originating from peripheral blood monocytes generated from bone marrow myeloid progenitor cells, play a crucial role in the tumor microenvironment (TME) and are closely associated with resistance to traditional cancer therapies. Lipid metabolism alterations have been widely recognized as having a significant impact on tumors and their immune microenvironment. Lipids, lipid derivatives, and key substances in their metabolic pathways can influence the carcinogenesis and progression of cancer cells by modulating the phenotype, function, and activity of TAMs. Therefore, this review focuses on the reprogramming of lipid metabolism in cancer cells and their immune microenvironment, in which the TAMs are especially concentrated. Such changes impact TAMs activation and polarization, thereby affecting the tumor cell response to treatment. Furthermore, the article explores the potential of targeting the lipid metabolism of TAMs as a supplementary approach to conventional cancer therapies. It reviews and evaluates current strategies for enhancing efficacy through TAMs' lipid metabolism and proposes new lipid metabolism targets as potential synergistic options for chemo-radiotherapy and immunotherapy. These efforts aim to stimulate further research in this area.

Efferocytosis in dendritic cells: an overlooked immunoregulatory process

Efferocytosis, the process of engulfing and removing apoptotic cells, plays an essential role in preserving tissue health and averting undue inflammation. While macrophages are primarily known for this task, dendritic cells (DCs) also play a significant role. This review delves into the unique contributions of various DC subsets to efferocytosis, highlighting the distinctions in how DCs and macrophages recognize and handle apoptotic cells. It further explores how efferocytosis influences DC maturation, thereby affecting immune tolerance. This underscores the pivotal role of DCs in orchestrating immune responses and sustaining immune equilibrium, providing new insights into their function in immune regulation.