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

Quantification of the inputs and outputs of serine and glycine metabolism in cancer cells

BACKGROUND

The significance of serine and glycine metabolism in cancer cells is increasingly acknowledged, yet the quantification of their metabolic flux remains incomplete, impeding a comprehensive understanding. This study aimed to quantify the metabolic flux of serine and glycine in cancer cells, focusing on their inputs and outputs, by means of Combinations of C-13 Isotopes Tracing and mathematical delineation, alongside Isotopically Nonstationary Metabolic Flux Analysis.

RESULTS

In HeLa cells, serine uptake, the serine synthesis pathway (SSP), and other sources (e.g., protein degradation) contribute 71.2 %, 24.0 %, and 5.7 %, respectively, to serine inputs. Conversely, glycine inputs stem from uptake (45.6 %), conversion from serine (45.1 %), and other sources (9.4 %). Serine input flux surpasses glycine by 7.3-fold. Serine predominantly directs a major fraction (94.7 %) to phospholipid, sphingolipid, and protein synthesis, with only a minor fraction (5.3 %) directing towards one-carbon unit and glycine production. Glycine mainly supports protein and nucleotide synthesis (100 %), without conversion back to serine. Serine output rate exceeds glycine output rate by 7.3-fold. Serine deprivation mainly impairs output to synthesis of phospholipid and sphingolipid, crucial for cell growth, while other outputs unaffected. AGS cells exhibit comparable serine and glycine flux to HeLa cells, albeit lacking SSP activity. Serine deprivation in AGS cells halts output flux to phospholipid, sphingolipid, protein synthesis, completely inhibiting cell growth.

CONCLUSIONS

By providing quantitative insights into serine and glycine metabolism, this study delineates the association of serine flux to different metabolic pathway with cancer cell growth and offers potential targets for therapeutic intervention, highlighting the importance of serine flux to pathway for the synthesis of phospholipids and sphingolipids in cancer cells growth.

Reprogramming and targeting of cholesterol metabolism in tumor-associated macrophages

Cholesterol, as a major component of cell membranes, is closely related to the metabolic regulation of cells and organisms; tumor-associated macrophages play an important push role in tumor progression. We know that tumor-associated macrophages are polarized from macrophages, and the abnormalities of cholesterol metabolism that may be induced during their polarization are worth discussing. This manuscript focuses on metabolic abnormalities in tumor-associated macrophages, and first provides a basic summary of the regulatory mechanisms of abnormal macrophage polarization. Subsequently, it comprehensively describes the features of abnormal glucose, lipid and cholesterol metabolism in TAMs as well as the different regulatory pathways. Then, the paper also discusses the link between abnormal cholesterol metabolism in TAMs and tumors, chronic diseases and aging. Finally, the paper summarizes cancer therapeutic strategies targeting cholesterol metabolism that are already in clinical trials, as well as nanomaterials capable of targeting cholesterol metabolism that are in the research stage, in the hope of providing value for the design of targeting materials. Overall, elucidating metabolic abnormalities in tumor-associated macrophages, particularly cholesterol metabolism, could provide assistance in tumor therapy and the design of targeted drugs.

NETs activate the GAS6-AXL-NLRP3 axis in macrophages to drive morphine tolerance

BACKGROUND

The development of morphine tolerance presents a major clinical challenge in the effective management of severe pain. This study aims to explore the mechanisms underlying morphine tolerance from a novel perspective, with the ultimate goal of uncovering new insights and identifying promising therapeutic targets for its treatment.

METHODS

C57BL/6J mice were used in the tail-flick test to evaluate morphine tolerance. Neutrophils derived from mouse bone marrow were employed to investigate the mechanisms underlying morphine-induced NETs formation. Bone marrow-derived macrophages (BMDMs) were harvested from the femur and tibia to study the role of NETs-induced inflammation in analgesic tolerance. Proinflammatory cytokines were measured using Western blotting and real-time PCR. The levels of NETs and the TLR7/9-NLRP3-related signaling pathway were assessed through Western blotting, real-time PCR, and ELISA. Confocal laser scanning microscopy was utilized to visualize NETs in the dorsal root ganglion (DRG) and in cells.

RESULTS

Our experiments demonstrated that the levels of NETs in the plasma of patients using morphine for analgesia, as well as in morphine-tolerant animals, were significantly elevated. Genetic elimination of Pad4, neutrophil depletion, and treatment with DNase 1 and RNase A to disrupt NETs formation all effectively alleviated morphine tolerance. These findings indicate that NETs play a critical role in the development of morphine tolerance. Mechanistically, we discovered that morphine-induced NETs can be engulfed by macrophages through the GAS6-AXL axis, which subsequently triggers the activation of the TLR7/TLR9-mediated NLRP3 inflammasome, leading to significantly increased levels of IL-1β and IL-18, and ultimately contributing to tolerance. Deletion of Axl, Gas6, or Nlrp3 each significantly improved morphine tolerance. Furthermore, in the murine model, treatment with the IL-1 receptor antagonist anakinra and the IL-18 decoy receptor IL-18BP prevented the development of morphine tolerance.

CONCLUSIONS

This study identifies morphine-induced NETs as a key contributor to morphine tolerance, with the GAS6-AXL-TLR7/9 axis emerging as a potential therapeutic target. Strategies focused on disrupting NETs and modulating this axis may offer a promising approach to combat morphine tolerance.

An overview of BAP1 biological functions and current therapeutics

BRCA1-associated protein 1 (BAP1) is a tumor suppressor gene that was first identified in 1998. Germline loss-of-function variants in BAP1 are associated with a tumor predisposition syndrome with at least four cancers: uveal melanoma (UM), malignant mesothelioma (MMe), renal cell carcinoma (RCC), and cutaneous melanoma (CM). Furthermore, somatic BAP1 mutations are important drivers for several cancers most notably UM, MMe, RCC, intrahepatic cholangiocarcinoma (ICC) and hepatocellular carcinoma (HCC). Emerging evidence substantiates the fundamental role of BAP1 in suppressing cancer initiation and progression by tuning DNA damage repair, apoptosis, ferroptosis, immune response, Warburg phenomenon, and metastasis. Multiple treatment strategies such as poly (ADP-ribose) polymerase (PARP) inhibitors, EZH2 inhibitors, alkylating agents, and immunotherapy have been used as potential therapies for BAP1-mutated tumors. Although these agents showed promising results in BAP1-mutated tumors in preclinical studies, the results of most clinical trials are still dismal. The objectives of this review are to summarize the current state of knowledge regarding the biological functions of BAP1, the implications of these functions in tumorigenesis, and the current progress in BAP1-targeted therapy.

Methylglyoxal deteriorates macrophage efferocytosis in diabetic wounds through ROS-induced ubiquitination degradation of KLF4

Diabetic wounds are a leading cause of disability and mortality in patients with diabetes, and persistent low-grade inflammation plays a significant role in their pathogenesis. Methylglyoxal (MGO), an active product of glucose metabolism, often induces chronic inflammation and is considered a major risk factor in the healing of diabetic wounds. Efferocytosis, the process by which macrophages clear apoptotic cells, is crucial for terminating the inflammatory response and tissue repair. However, the role of MGO in macrophage efferocytosis remains unclear. This study aimed to investigate whether MGO regulates macrophage efferocytosis and the underlying mechanisms. In this study, we observed impaired efferocytosis in diabetic wounds, leading to the accumulation of apoptotic neutrophils and a relative deficiency of M2 macrophages, with MGO being a significant cause. MGO promotes the production of ROS, which not only activates the MAPK p38 pathway, but also upregulates the transcription of the E3 ubiquitin ligase FBXO32, catalyzing the ubiquitination of the transcription factor KLF4 and suppressing the transcription of MerTK mRNA, thereby affecting the phagocytic function of macrophages. Inhibition of the MAPK p38 pathway or knockdown of FBXO32 reduced the ubiquitination and degradation of KLF4, thus mitigating the impairment of efferocytosis caused by oxidative stress. This study reveals the mechanism by which MGO inhibits efferocytosis in diabetic wounds, providing a new target and theoretical basis for the treatment of chronic diabetic wounds.

Enhance Efferocytosis and Block the Macrophages-Platelets Feedback Loop for Targeted Treatment of Psoriasis

Efferocytosis of macrophages infiltrated in psoriatic lesions is mostly impaired, thus promoting the progression of psoriasis. Herein, we reveal that there exists a feedback loop between activated platelets and efferocytosis-impaired macrophages in psoriatic. Or rather, efferocytosis-impaired macrophages stimulate platelet activation, which in turn down-regulates the expression of the phagocytic receptor Mer on macrophages and polarizes macrophages to the M1-phenotype of weaker efferocytosis ability. Therefore, we construct a combined nanoplatform for more precise targeting to efferocytosis-impaired macrophages and activated platelets. The macrophage-targeting part of the nanoplatform efficiently orientates to efferocytosis-impaired macrophages through macrophage membrane encapsulation and targeting peptide modification. This increases the expression of Mer, simultaneously enhances the acidification and maturation of efferosomes, ultimately restores efferocytosis of macrophages, and promotes the phagocytosis and clearance of apoptotic cells. On the other hand, the activated platelet-targeting nanoparticles inhibit the activation of platelets, thus blocking the feedback loop and eventually preventing the down-regulation of Mer expression on macrophages. Furthermore, the combined nanoplatform suppresses the infiltration of macrophages and platelets in psoriatic lesions, reduces the release of pro-inflammatory factors such as IL-17A, and consequently improves the therapeutic effect of psoriasis and prevention of its recurrence in vivo. Collectively, this two-pronged strategy with multifunctionality in repairing efferocytosis, inhibiting platelet activation, and blocking the feedback loop may provide options available for the treatment of psoriasis.

Dys-regulated phosphatidylserine externalization as a cell intrinsic immune escape mechanism in cancer

The negatively charged aminophospholipid, phosphatidylserine (PS), is typically restricted to the inner leaflet of the plasma membrane under normal, healthy physiological conditions. PS is irreversibly externalized during apoptosis, where it serves as a signal for elimination by efferocytosis. PS is also reversibly and transiently externalized during cell activation such as platelet and immune cell activation. These events associated with physiological PS externalization are tightly controlled by the regulated activation of flippases and scramblases. Indeed, improper regulation of PS externalization results in thrombotic diseases such as Scott Syndrome, a defect in coagulation and thrombin production, and in the case of efferocytosis, can result in autoimmunity such as systemic lupus erythematosus (SLE) when PS-mediated apoptosis and efferocytosis fails. The physiological regulation of PS is also perturbed in cancer and during viral infection, whereby PS becomes persistently exposed on the surface of such stressed and diseased cells, which can lead to chronic thrombosis and chronic immune evasion. In this review, we summarize evidence for the dysregulation of PS with a main focus on cancer biology and the pathogenic mechanisms for immune evasion and signaling by PS, as well as the discussion of new therapeutic strategies aimed to target externalized PS. We posit that chronic PS externalization is a universal and agnostic marker for diseased tissues, and in cancer, likely reflects a cell intrinsic form of immune escape. The continued development of new therapeutic strategies for targeting PS also provides rationale for their co-utility as adjuvants and with immune checkpoint therapeutics.

Regulation of macrophage efferocytosis by the CLCF1/NF-κB pathway improves neurological and cognitive impairment following CO poisoning

Severe carbon monoxide (CO) poisoning can induce structural and functional damage to the nervous system, resulting in persistent cognitive impairments. Properly terminating inflammation caused by neuronal damage is essential for tissue repair. Macrophages clear cell corpses and fragments through efferocytosis and produce cytokines to coordinate the immune response, thus promoting neuronal repair and regeneration. However, within the microenvironment of the CO-affected nervous system, macrophage efferocytosis is disrupted. Our study found that macrophages regulate efferocytosis by releasing Cardiotrophin-like cytokine factor 1 (CLCF1), which modulates the NF-κB pathway in both macrophages and microglia, thereby controlling inflammation and promoting nervous system repair. Furthermore, efferocytosis regulates the secretion of cytokines such as TNF-α, IL-1β, and IL-10, promoting M2 polarization of macrophages, which aids in neuronal repair and regeneration. Regulating macrophage CLCF1 expression also leads to improvements in the memory, learning, and motor abilities of rats poisoned with CO.

Exploring MERTK inhibitor binding mechanisms: insights from adaptive steered molecular dynamics and free energy calculation

MERTK, a promising drug target for the treatment of human leukemia and solid tumors, and the development of its small molecule inhibitors holds significant clinical potential. However, the underlying reasons for the varying activities among these inhibitors and the specifics of their binding mechanism have not been systematically investigated. By combining conventional molecular dynamics simulations, adaptive steered molecular dynamics simulations and binding free energy calculations based on molecular mechanics Poisson-Boltzmann surface area, the interaction modes of four MERTK inhibitors and dissociation behavior are discussed in detail. The results reveal additional critical amino acids, beyond the well-known hot spot residues in the kinase hinge region, that play a pivotal role in inhibitor binding. Our findings further indicate that the binding of MERTK to its inhibitors relies not only on crucial hydrogen bonding interactions but also benefits from non-polar interactions. In addition, the analysis of hydrogen bonding within kinetic trajectories and potential of mean force explained the differences in activity between different inhibitors, providing insights for the design and optimization of subsequent MERTK-targeted small molecule inhibitors.

Harnessing myeloid cells in cancer

Cancer-associated myeloid cells due to their plasticity play dual roles in both promoting and inhibiting tumor progression. Myeloid cells with immunosuppressive properties play a critical role in anti-cancer immune regulation. Cells of different origin, such as tumor associated macrophages (TAMs), tumor associated neutrophils (TANs), myeloid derived suppressor cells (also called MDSCs) and eosinophils are often expanded in cancer patients and significantly influence their survival, but also the outcome of anti-cancer therapies. For this reason, the variety of preclinical and clinical studies to modulate the activity of these cells have been conducted, however without successful outcome to date. In this review, pro-tumor activity of myeloid cells, myeloid cell-specific therapeutic targets, in vivo studies on myeloid cell re-polarization and the impact of myeloid cells on immunotherapies/genetic engineering are addressed. This paper also summarizes ongoing clinical trials and the concept of chimeric antigen receptor macrophage (CAR-M) therapies, and suggests future research perspectives, offering new opportunities in the development of novel clinical treatment strategies.

Proteolysis of TAM receptors in autoimmune diseases and cancer: what does it say to us?

Proteolytic processing of Receptor Tyrosine Kinases (RTKs) leads to the release of ectodomains in the extracellular space. These soluble ectodomains often retain the ligand binding activity and dampen canonical pathways by acting as decoy receptors. On the other hand, shedding the ectodomains may initiate new molecular events and diversification of signalling. Members of the TAM (TYRO3, AXL, MER) family of RTKs undergo proteolytic cleavage, and their soluble forms are present in the extracellular space and biological fluids. TAM receptors are expressed in professional phagocytes, mediating apoptotic cell clearance, and suppressing innate immunity. Enhanced shedding of TAM ectodomains is documented in autoimmune and some inflammatory conditions. Also, soluble TAM receptors are present at high levels in the biological fluids of cancer patients and are associated with poor survival. We outline the biology of TAM receptors and discuss how their proteolytic processing impacts autoimmunity and tumorigenesis. In autoimmune diseases, proteolysis of TAM receptors likely reflects reduced canonical signalling in professional phagocytes. In cancer, TAM receptors are expressed in the immune cells of the tumour microenvironment, where they control pathways facilitating immune evasion. In tumour cells, ectodomain shedding activates non-canonical TAM pathways, leading to epithelial-mesenchymal transition, metastasis, and drug resistance.

Denfivontinib Activates Effector T Cells Through the NLRP3 Inflammasome, Yielding Potent Anticancer Effects by Combination with Pembrolizumab

Various combination therapies have been investigated to overcome the limitations of using immune checkpoint inhibitors. However, determining the optimal combination therapy remains challenging. To overcome the therapeutic limitation, we conducted a translational research to elucidate the mechanisms by which AXL inhibition enhances antitumor effects when combined with anti-PD-1 antibody therapy. Herein, we demonstrated improved antitumor effects through combination treatment with denfivontinib and pembrolizumab which resulted in enhanced differentiation into effector CD4+ and CD8+ memory T cells, accompanied by an increase in IFN-γ expression in the YHIM-2004 xenograft model derived from patients with non-small cell lung cancer. Concurrently, a reduction in the number of immunosuppressive M2 macrophages and myeloid-derived suppressor cells was observed. Mechanistically, denfivontinib potentiated the NOD-like receptor pathway, thereby facilitating NLRP3 inflammasome formation. This leads to macrophage activation via NF-κB signaling pathway activation. We have confirmed that the positive interaction between macrophages and T cells arises from the enhanced antigen-presenting machinery of activated macrophages. Furthermore, the observed tumor effects in AXL knockout mice confirmed that AXL inhibition by denfivontinib enhances the antitumor effects, thus opening new avenues for therapeutic interventions aimed at overcoming limitations in immunotherapy. To demonstrate the extent to which our findings reflect clinical results, we analyzed bulk RNA sequencing data from 21 patients with non-small cell lung cancer undergoing anti-PD-1 immunotherapy. The NLRP3 inflammasome score influenced enhanced immune responses in patient data undergoing anti-PD-1 immunotherapy, suggesting a role for the NLRP3 inflammasome in activating immune responses during treatment.

Cellular interactions within the immune microenvironment underpins resistance to cell cycle inhibition in breast cancers

Immune evasion by cancer cells involves reshaping the tumor microenvironment (TME) via communication with non-malignant cells. However, resistance-promoting interactions during treatment remain lesser known. Here we examine the composition, communication, and phenotypes of tumor-associated cells in serial biopsies from stage II and III high-risk estrogen receptor positive (ER+ ) breast cancers of patients receiving endocrine therapy (letrozole) as single agent or in combination with ribociclib, a CDK4/6-targeting cell cycle inhibitor. Single-cell RNA sequencing analyses on longitudinally collected samples show that in tumors overcoming the growth suppressive effects of ribociclib, first cancer cells upregulate cytokines and growth factors that stimulate immune-suppressive myeloid differentiation, resulting in reduced myeloid cell- CD8 + T-cell crosstalk via IL-15/18 signaling. Subsequently, tumors growing during treatment show diminished T-cell activation and recruitment. In vitro, ribociclib does not only inhibit cancer cell growth but also T cell proliferation and activation upon co-culturing. Exogenous IL-15 improves CDK4/6 inhibitor efficacy by augmenting T-cell proliferation and cancer cell killing by T cells. In summary, response to ribociclib in stage II and III high-risk ER +  breast cancer depends on the composition, activation phenotypes and communication network of immune cells.

Novel anti-inflammatory compounds that alleviate experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease primarily characterized by inflammatory demyelination. Despite significant research efforts, effective therapies for MS remain limited. Drug screening offers a promising approach to rapidly identifying potential therapeutic compounds.

PURPOSE

This study aimed to screen compounds that can exert anti-inflammatory effects and alleviate experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

STUDY DESIGN

A fundamental research in vitro and in vivo. A high-throughput screen was performed to screen drugs that can mitigate EAE and the molecular mechanism was explored.

METHODS

Based on our previous research highlighting the crucial role of AXL, a receptor tyrosine kinase, in microglial function, we constructed an AXL-GFP reporter gene in BV2 microglia cells. A high-throughput screen of an FDA-approved compound library was performed to identify potential AXL-targeting compounds. The effects of candidate compounds on cellular morphology, cell cycle, apoptosis, mitochondrial function, inflammatory cytokine production, polarization, and phagocytic activity of BV2 cells were assessed. To investigate the in vivo effects of AXL modulation, EAE mice were generated. AXL was either upregulated using recombinant Gas6 protein or knocked out using CRISPR/Cas9. The impact of AXL modulation on disease progression and underlying molecular mechanisms was explored.

RESULTS

Primary and secondary screenings identified three potential AXL-targeting compounds: Betulin, Clofibric acid, and Isosorbide. Molecular docking analysis revealed that Isosorbide exhibited poor binding affinity with AXL at the molecular level and was excluded from further studies. Betulin and Clofibric acid were found to promote M2 polarization, reduce inflammation, enhance phagocytosis, extend the S phase of the cell cycle, inhibit apoptosis, and improve mitochondrial structure in BV2 cells. In vivo studies demonstrated that Betulin (20 mg/kg) alleviated EAE, while AXL gene knockout reversed its protective effects.

CONCLUSION

This study elucidates the molecular mechanism underlying Betulin's therapeutic effects in MS, both in vitro and in vivo. Betulin exerts its beneficial effects by upregulating the AXL/SOCS3 pathway and inhibiting the JAK2/STAT1 signaling pathway. These findings suggest that Betulin holds significant promise as a potential therapeutic agent for multiple sclerosis.

The role of tumor-associated macrophages in lung cancer

Lung cancer remains a leading cause of cancer-related deaths worldwide, necessitating innovative treatments. Tumor-associated macrophages (TAMs) are primary immunosuppressive effectors that foster tumor proliferation, angiogenesis, metastasis, and resistance to therapy. They are broadly categorized into proinflammatory M1 and tumor-promoting M2 phenotypes, with elevated M2 infiltration correlating with poor prognosis. Strategies aimed at inhibiting TAM recruitment, depleting TAMs, or reprogramming M2 to M1 are therefore highly promising. Key signaling pathways, such as CSF-1/CSF-1R, IL-4/IL-13-STAT6, TLRs, and CD47-SIRPα, regulate TAM polarization. Additionally, macrophage-based drug delivery systems permit targeted agent transport to hypoxic regions, enhancing therapy. Preclinical studies combining TAM-targeted therapies with chemotherapy or immune checkpoint inhibitors have yielded improved responses and prolonged survival. Several clinical trials have also reported benefits in previously unresponsive patients. Future work should clarify the roles of macrophage-derived exosomes, cytokines, and additional mediators in shaping the immunosuppressive tumor microenvironment. These insights will inform the design of next-generation drug carriers and optimize combination immunotherapies within precision medicine frameworks. Elucidating TAM phenotypes and their regulatory molecules remains central to developing novel strategies that curb tumor progression and ultimately improve outcomes in lung cancer. Importantly, macrophage-based immunomodulation may offer expanded treatment avenues.

Hua Zheng San Ji Fang suppresses liver cancer progression by inhibiting TYRO3 expression via the ERK signaling pathway

BACKGROUND

Liver cancer poses a significant global health challenge owing to its increasing incidence and associated mortality rates. Traditional Chinese Medicine (TCM) has garnered attention for its potential in oncology, with formulations such as Hua Zheng San Ji Fang (HZSJF) exhibiting antineoplastic effects. HZSJF is clinically employed in China for cancer treatment; however, its molecular mechanisms in liver cancer remain elusive. TYRO3 plays a key role in tumor progression via the ERK signaling pathway, rendering it a potential therapeutic target. However, the effect of HZSJF on TYRO3 expression and its downstream signaling in liver cancer remains unexplored.

PURPOSE

This study aimed to investigate the molecular mechanisms through which HZSJF alleviates liver cancer progression, focusing on its regulation of TYRO3 and the ERK signaling pathway.

METHODS

TYRO3 expression in liver cancer and para-carcinoma tissues was analyzed using immunohistochemistry, reverse transcription-quantitative PCR, and western blotting. Liver cancer cells were used to investigate HZSJF-regulated pathways. Transcriptome sequencing was used to identify HZSJF-targeted genes. Cell proliferation, apoptosis, invasion, and migration were assessed using EdU, YO-PRO-1/PI staining, and transwell assays. ERK signaling involvement was examined using a specific inhibitor and validated in vivo using subcutaneous nude mouse tumor models.

RESULTS

HZSJF significantly inhibited TYRO3 expression and ERK pathway activation, reducing proliferation, invasion, and migration while promoting apoptosis. The ERK inhibitor corroborated the pathway's role in the antitumor effects of HZSJF. HZSJF suppressed tumor growth and TYRO3 expression in vivo.

CONCLUSION

HZSJF alleviated liver cancer progression through the ERK signaling pathway by inhibiting TYRO3 expression, presenting a potential therapeutic approach.

Bacterial-Mediated In Situ Engineering of Tumour-Associated Macrophages for Cancer Immunotherapy

BACKGROUND/OBJECTIVES

Tumour-associated macrophages (TAMs) are critical components of the tumour microenvironment (TME), significantly influencing cancer progression and treatment resistance. This review aims to explore the innovative use of engineered bacteria to reprogram TAMs, enhancing their anti-tumour functions and improving therapeutic outcomes.

METHODS

We conducted a systematic review following a predefined protocol. Multiple databases were searched to identify relevant studies on TAMs, their phenotypic plasticity, and the use of engineered bacteria for reprogramming. Inclusion and exclusion criteria were applied to select studies, and data were extracted using standardised forms. Data synthesis was performed to summarise the findings, focusing on the mechanisms and therapeutic benefits of using non-pathogenic bacteria to modify TAMs.

RESULTS

The review summarises the findings that engineered bacteria can selectively target TAMs, promoting a shift from the tumour-promoting M2 phenotype to the tumour-fighting M1 phenotype. This reprogramming enhances pro-inflammatory responses and anti-tumour activity within the TME. Evidence from various studies indicates significant tumour regression and improved immune responses following bacterial therapy.

CONCLUSIONS

Reprogramming TAMs using engineered bacteria presents a promising strategy for cancer therapy. This approach leverages the natural targeting abilities of bacteria to modify TAMs directly within the tumour, potentially improving patient outcomes and offering new insights into immune-based cancer treatments. Further research is needed to optimise these methods and assess their clinical applicability.

AXL signaling in cancer: from molecular insights to targeted therapies

AXL, a member of the TAM receptor family, has emerged as a potential target for advanced-stage human malignancies. It is frequently overexpressed in different cancers and plays a significant role in various tumor-promoting pathways, including cancer cell proliferation, invasion, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, DNA damage response, acquired therapeutic resistance, immunosuppression, and inflammatory responses. Beyond oncology, AXL also facilitates viral infections, including SARS-CoV-2 and Zika highlighting its importance in both cancer and virology. In preclinical models, small-molecule kinase inhibitors targeting AXL have shown promising anti-tumorigenic potential. This review primarily focuses on the induction, regulation and biological functions of AXL in mediating these tumor-promoting pathways. We discuss a range of therapeutic strategies, including recently developed small-molecule tyrosine kinase inhibitors (TKIs), monoclonal antibodies, and antibody-drug conjugates (ADCs), anti-AXL-CAR, and combination therapies. These interventions are being examined in both preclinical and clinical studies, offering the potential for improved drug sensitivity and therapeutic efficacy. We further discuss the mechanisms of acquired therapeutic resistance, particularly the crosstalk between AXL and other critical receptor tyrosine kinases (RTKs) such as c-MET, EGFR, HER2/HER3, VEGFR, PDGFR, and FLT3. Finally, we highlight key research areas that require further exploration to enhance AXL-mediated therapeutic approaches for improved clinical outcomes.

Cancer stem cells and tumor-associated macrophages as mates in tumor progression: mechanisms of crosstalk and advanced bioinformatic tools to dissect their phenotypes and interaction

Cancer stem cells (CSCs) are a small subset within the tumor mass significantly contributing to cancer progression through dysregulation of various oncogenic pathways, driving tumor growth, chemoresistance and metastasis formation. The aggressive behavior of CSCs is guided by several intracellular signaling pathways such as WNT, NF-kappa-B, NOTCH, Hedgehog, JAK-STAT, PI3K/AKT1/MTOR, TGF/SMAD, PPAR and MAPK kinases, as well as extracellular vesicles such as exosomes, and extracellular signaling molecules such as cytokines, chemokines, pro-angiogenetic and growth factors, which finely regulate CSC phenotype. In this scenario, tumor microenvironment (TME) is a key player in the establishment of a permissive tumor niche, where CSCs engage in intricate communications with diverse immune cells. The "oncogenic" immune cells are mainly represented by B and T lymphocytes, NK cells, and dendritic cells. Among immune cells, macrophages exhibit a more plastic and adaptable phenotype due to their different subpopulations, which are characterized by both immunosuppressive and inflammatory phenotypes. Specifically, tumor-associated macrophages (TAMs) create an immunosuppressive milieu through the production of a plethora of paracrine factors (IL-6, IL-12, TNF-alpha, TGF-beta, CCL1, CCL18) promoting the acquisition by CSCs of a stem-like, invasive and metastatic phenotype. TAMs have demonstrated the ability to communicate with CSCs via direct ligand/receptor (such as CD90/CD11b, LSECtin/BTN3A3, EPHA4/Ephrin) interaction. On the other hand, CSCs exhibited their capacity to influence immune cells, creating a favorable microenvironment for cancer progression. Interestingly, the bidirectional influence of CSCs and TME leads to an epigenetic reprogramming which sustains malignant transformation. Nowadays, the integration of biological and computational data obtained by cutting-edge technologies (single-cell RNA sequencing, spatial transcriptomics, trajectory analysis) has significantly improved the comprehension of the biunivocal multicellular dialogue, providing a comprehensive view of the heterogeneity and dynamics of CSCs, and uncovering alternative mechanisms of immune evasion and therapeutic resistance. Moreover, the combination of biology and computational data will lead to the development of innovative target therapies dampening CSC-TME interaction. Here, we aim to elucidate the most recent insights on CSCs biology and their complex interactions with TME immune cells, specifically TAMs, tracing an exhaustive scenario from the primary tumor to metastasis formation.

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.

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.

Cholesterol mobilization regulates dendritic cell maturation and the immunogenic response to cancer

Maturation of conventional dendritic cells (cDCs) is crucial for maintaining tolerogenic safeguards against auto-immunity and for promoting immunogenic responses to pathogens and cancer. The subcellular mechanism for cDC maturation remains poorly defined. We show that cDCs mature by leveraging an internal reservoir of cholesterol (harnessed from extracellular cell debris and generated by de novo synthesis) to assemble lipid nanodomains on cell surfaces of maturing cDCs, enhance expression of maturation markers and stabilize immune receptor signaling. This process is dependent on cholesterol transport through Niemann-Pick disease type C1 (NPC1) and mediates homeostatic and Toll-like receptor (TLR)-induced maturation. Importantly, we identified the receptor tyrosine kinase AXL as a regulator of the NPC1-dependent construction of lipid nanodomains. Deleting AXL from cDCs enhances their maturation, thus improving anti-tumor immunity. Altogether, our study presents new insights into cholesterol mobilization as a fundamental basis for cDC maturation and highlights AXL as a therapeutic target for modulating cDCs.

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.

Lymphatic-derived oxysterols promote anti-tumor immunity and response to immunotherapy in melanoma

In melanoma, lymphangiogenesis correlates with metastasis and poor prognosis and promotes immunosuppression. However, it also potentiates immunotherapy by supporting immune cell trafficking. We show in a lymphangiogenic murine melanoma that lymphatic endothelial cells (LECs) upregulate the enzyme Ch25h, which catalyzes the formation of 25-hydroxycholesterol (25-HC) from cholesterol and plays important roles in lipid metabolism, gene regulation, and immune activation. We identify a role for LECs as a source of extracellular 25-HC in tumors inhibiting PPAR-γ in intra-tumoral macrophages and monocytes, preventing their immunosuppressive function and instead promoting their conversion into proinflammatory myeloid cells that support effector T cell functions. In human melanoma, LECs also upregulate Ch25h, and its expression correlates with the lymphatic vessel signature, infiltration of pro-inflammatory macrophages, better patient survival, and better response to immunotherapy. We identify here in mechanistic detail an important LEC function that supports anti-tumor immunity, which can be therapeutically exploited in combination with immunotherapy.

Role of the AKT signaling pathway in regulating tumor-associated macrophage polarization and in the tumor microenvironment: A review

Tumor-associated macrophages (TAMs) are present in and are important components of the tumor microenvironment (TME). TAMs differentiate into 2 functionally distinct morphologies, classically activated (M1)-type TAMs and alternatively activated (M2)-type TAMs, when stimulated by different cytokines. The 2 types of TAMs exhibit distinct properties and functions. M1 TAMs secrete high levels of pro-inflammatory and chemotactic factors, exerting proinflammatory, antitumor effects. Conversely, M2 TAMs alter the extracellular matrix, facilitate cellular immune escape, and stimulate tumor angiogenesis, thereby promoting anti-inflammatory responses and tumor growth. The ratio of M1 TAMs to M2 TAMs in the TME is closely related to the prognosis of the tumor. Tumor cells and other cells in the TME can regulate the polarization of TAMs and thus promote tumor progression through the secretion of various substances; however, polarized TAMs can also act on various cells in the TME through the secretion of exosomes, thus forming a positive feedback loop. Therefore, modulating the phenotype of TAMs in the TME or blocking the polarization of M2 TAMs might be a new approach for cancer treatment. However, the intracellular signaling pathways involved in the polarization of TAMs are poorly understood. The AKT signaling pathway is an important signaling pathway involved in the polarization, growth, proliferation, recruitment, and apoptosis of TAMs, as well as the action of TAMs on other cells within the TME. This paper reviews the AKT signaling pathway in the polarization of TAMs and the regulation of the TME and provides new ideas for tumor immunotherapy.

Second-generation anti-amyloid monoclonal antibodies for Alzheimer's disease: current landscape and future perspectives

Alzheimer's disease (AD) is the most common type of dementia. Monoclonal antibodies (MABs) serve as a promising therapeutic approach for AD by selectively targeting key pathogenic factors, such as amyloid-β (Aβ) peptide, tau protein, and neuroinflammation. Specifically, based on their efficacy in removing Aβ plaques from the brains of patients with AD, the U.S. Food and Drug Administration has approved three anti-amyloid MABs, aducanumab (Aduhelm®), lecanemab (Leqembi®), and donanemab (Kisunla™). Notably, lecanemab received traditional approval after demonstrating clinical benefit, supporting the Aβ cascade hypothesis. These MABs targeting Aβ are categorized based on their affinity to diverse conformational features of Aβ, including monomer, fibril, protofibril, and plaque forms of Aβ as well as pyroglutamate Aβ. First-generation MABs targeting the non-toxic monomeric Aβ, such as solanezumab, bapineuzumab, and crenezumab, failed to demonstrate clinical benefit for AD in clinical trials. In contrast, second-generation MABs, including aducanumab, lecanemab, donanemab, and gantenerumab directed against pathogenic Aβ species and aggregates have shown that reducing Aβ deposition can be an effective strategy to slow cognitive impairment in AD. In this review, we provide a comprehensive overview of the current status, mechanisms, outcomes, and limitations of second-generation MABs for the clinical treatment of AD. Moreover, we discuss the perspectives and future directions of anti-amyloid MABs in the treatment of AD.

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.

Immunomodulatory effect of efferocytosis at the maternal-fetal interface

Efferocytosis is a mechanism by which phagocytes efficiently clear apoptotic cells, averting their secondary necrosis and the subsequent release of potentially immunogenic or cytotoxic substances that can trigger strong immune and inflammatory responses. During efferocytosis, the metabolic pathways of phagocytes are transformed, which, along with the catabolism of apoptotic cargo, can affect their function and inflammatory state. Extensive apoptosis occurs during placental development, and some studies reported the immunomodulatory effects of efferocytosis at the maternal-fetal interface. The dysregulation of efferocytosis is strongly linked to pregnancy complications such as preeclampsia and recurrent spontaneous abortion. In this review, we discuss the mechanisms of efferocytosis and its relationships with metabolism and inflammation. We also highlight the roles of professional and non-professional phagocytes in efferocytosis at the maternal-fetal interface and their impact on pregnancy outcomes and explore relevant regulatory factors. These insights are expected to guide future basic research and clinical strategies for identifying efferocytosis-related molecules as potential predictors or therapeutic targets in obstetric diseases.

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.

Staphylococcus aureus vesicles impair cutaneous wound healing through p38 MAPK-MerTK cleavage-mediated inhibition of macrophage efferocytosis

BACKGROUND

Staphylococcus aureus, a known contributor to non-healing wounds, releases vesicles (SAVs) that influence the delicate balance of host-pathogen interactions. Efferocytosis, a process by which macrophages clear apoptotic cells, plays a key role in successful wound healing. However, the precise impact of SAVs on wound repair and efferocytosis remains unknown.

METHODS

Filtration, ultracentrifugation, and iodixanol density gradient centrifugation were used to purify the bacterial vesicles. Transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot (WB) were used to characterize the vesicles. Macrophage efferocytosis efficiency was assessed using flow cytometry and confocal microscopy, while efferocytosis at wound sites was analyzed through WB, FACS, and TUNEL staining. Hematoxylin and eosin (H&E) staining and wound size measurements were used to evaluate the wound healing process. Phosphorylation of signaling pathways was detected by WB, and efferocytosis receptor expression was measured using RNA sequencing, qPCR, and flow cytometry. siRNA and pathway inhibitors were used to investigate the roles of key receptors and signaling pathways in efferocytosis.

RESULTS

We identified SAVs at infected wound sites, linking them to delayed healing of wounds. SAVs inhibit efferocytosis by activating the TLR2-MyD88-p38 MAPK signaling pathway, which regulates efferocytosis receptor genes. This activation promoted cleavage and shedding of MerTK, a crucial receptor for macrophage-driven efferocytosis. Notably, selective inhibition of p38 MAPK prevented MerTK shedding, restored efferocytosis and accelerated wound healing significantly, offering a promising therapeutic approach for chronic, non-healing wounds.

CONCLUSION

These findings uncover a novel mechanism in S. aureus-infected wounds, highlighting how the disruption of efferocytosis via the TLR2-MyD88-p38 MAPK-MerTK axis becomes a key force behind impaired healing of wounds. Targeting this pathway could open up a new therapeutic avenue facilitating the treatment of chronic, non-healing skin injuries.

Tumor-initiating cells escape tumor immunity via CCL8 from tumor-associated macrophages in mice

Tumor-initiating cells (TICs) play a key role in cancer progression and immune escape. However, how TICs evade immune elimination remains poorly characterized. Combining single-cell RNA-Seq (scRNA-Seq), dual-recombinase-based lineage tracing, and other approaches, we identified a WNT-activated subpopulation of malignant cells that act as TICs in vivo. We found intensive reciprocal interactions between TICs and immune-regulatory tumor-associated macrophages (Reg-TAMs) via growth arrest-specific 6/AXL receptor tyrosine kinase/MER proto-oncogene, tyrosine kinase (GAS6/AXL/MERTK) signaling pathways, which facilitated the immune escape of TICs. In this study, we used chemical inhibitors and Axl/Mertk conditional double-KO (cDKO) mice to demonstrate that inhibiting the interaction between TIC-derived GAS6 and AXL/MERTK in Reg-TAMs reactivated antitumor immune responses. We identified CCL8 as a critical mediator of the GAS6/AXL/MERTK pathway, primarily by inhibiting Treg infiltration into the tumor. Furthermore, the AXL/MERTK signaling blockade sensitized tumor cells to anti-programmed cell death 1 (anti-PD-1) treatment. Thus, we elucidated a detailed mechanism by which TICs evade tumor immunity, providing insights into strategies to eradicate TICs that escape conventional immunotherapy.

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.

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 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.

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.