The Role of TAM Family Receptors in Immune Cell Function: Implications for Cancer Therapy

Gas6/TAM system as potential biomarker for multiple sclerosis prognosis

Introduction

The protein growth arrest-specific 6 (Gas6) and its tyrosine kinase receptors Tyro-3, Axl, and Mer (TAM) are ubiquitous proteins involved in regulating inflammation and apoptotic body clearance. Multiple sclerosis (MS) is the most common inflammatory demyelinating disease of the central nervous system leading to progressive and irreversible disability if not diagnosed and treated promptly. Gas6 and TAM receptors have been associated with neuronal remyelination and stimulation of oligodendrocyte survival. However, few data are available regarding clinical correlation in MS patients. We aimed to evaluate soluble levels of these molecules in the cerebrospinal fluid (CSF) and serum at MS diagnosis and correlate them with short-term disease severity.

Methods

In a prospective cohort study, we enrolled 64 patients with a diagnosis of clinical isolated syndrome (CIS), radiological isolated syndrome (RIS) and relapsing-remitting (RR) MS according to the McDonald 2017 Criteria. Before any treatment initiation, we sampled the serum and CSF, and collected clinical data: disease course, presence of gadolinium-enhancing lesions, and expanded disability status score (EDSS). At the last clinical follow-up, we assessed EDSS and calculated MS severity score (MSSS) and age-related MS severity (ARMSS). Gas6 and TAM receptors were determined using an ELISA kit (R&D Systems) and compared to neurofilament (NFLs) levels evaluated with SimplePlex™ fluorescence-based immunoassay.

Results

At diagnosis, serum sAxl was higher in patients receiving none or low-efficacy disease-modifying treatments (DMTs) versus patients with high-efficacy DMTs (p = 0.04). Higher CSF Gas6 and serum sAXL were associated with an EDSS <3 at diagnosis (p = 0.04; p = 0.037). Serum Gas6 correlates to a lower MSSS (r2 = -0.32, p = 0.01). Serum and CSF NFLs were confirmed as disability biomarkers in our cohort according to EDSS (p = 0.005; p = 0.002) and MSSS (r2 = 0.27, p = 0.03; r2 = 0.39, p = 0.001). Results were corroborated using multivariate analysis.

Conclusions

Our data suggest a protective role of Gas6 and its receptors in patients with MS and suitable severity disease biomarkers.

Sitravatinib combined with PD-1 blockade enhances cytotoxic T-cell infiltration by M2 to M1 tumor macrophage repolarization in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) is a leading cause of cancer-related mortality. Sitravatinib is a novel multi-gene tyrosine kinase inhibitor (TKI) that targets tumor-associated macrophage (TAM) receptors, VEGF, PDGF and c-Kit. Currently, sitravatinib is actively being studied in clinical trials across solid tumors and other TKIs have shown efficacy in combination with immune checkpoint inhibitors (ICI) in cancer models. In this study, we investigated the anti-tumor activity of sitravatinib alone and in combination with PD-1 blockade in an EAC rat model. Treatment response was evaluated by mortality, pre- and post-treatment MRI, gene expression, immunofluorescence and immunohistochemistry. Our results demonstrated adequate safety and significant tumor shrinkage in animals treated with sitravatinib, and more profoundly, sitravatinib and PD-1 inhibitor, AUNP-12 (P < 0.01). Suppression of TAM receptors resulted in increased gene expression of pro-inflammatory cytokines and decreased expression of anti-inflammatory cytokines, enhanced infiltration of CD8+ T cells, and M2 to M1 macrophage phenotype repolarization in the tumor microenvironment of treated animals (P < 0.01). Moreover, endpoint immunohistochemistry staining corroborated the anti-tumor activity by downregulation of Ki67 and upregulation of Caspase-3 in the treated animals. Additionally, pretreatment gene expression of TAM receptors and PD-L1 were significantly higher in major responders compared with the non-responders, in animals that received sitravatinib and AUNP-12 (P < 0.02), confirming that TAM suppression enhances the efficacy of PD-1 blockade. In conclusion, this study proposes a promising immunomodulatory strategy using a multi-gene TKI to overcome developed resistance to an ICI in EAC, establishing rationale for future clinical development.

Chronic inflammation and cancer; the two sides of a coin

The correlation between chronic inflammation and cancer was initially identified in the 19th century. Biomolecules like interleukins, chemokines, tumor necrosis factors, growth factors, and adhesion molecules, which regulate inflammation, are recognized contributors to neoplastic transformation through various mechanisms, including oncogenic mutations, resistance to apoptosis, and adaptive responses like angiogenesis. This review aims to establish connections between the intricate and complex mechanisms of chronic inflammation and cancer. We illuminate implicit signaling mechanisms that drive the association between chronic inflammation and the initiation/progression of cancer, exploring potential impacts on other diseases. Additionally, we discuss the modalities of currently available therapeutic options for chronic inflammation and cancer, emphasizing the dual nature of such therapies. A thorough understanding of the molecular basis of chronic inflammation is crucial for developing novel approaches in the prevention and treatment of cancer.

GAS6/TAM Axis as Therapeutic Target in Liver Diseases

TAM (TYRO3, AXL, and MERTK) protein tyrosine kinase membrane receptors and their vitamin K-dependent ligands GAS6 and protein S (PROS) are well-known players in tumor biology and autoimmune diseases. In contrast, TAM regulation of fibrogenesis and the inflammation mechanisms underlying metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and, ultimately, liver cancer has recently been revealed. GAS6 and PROS binding to phosphatidylserine exposed in outer membranes of apoptotic cells links TAMs, particularly MERTK, with hepatocellular damage. In addition, AXL and MERTK regulate the development of liver fibrosis and inflammation in chronic liver diseases. Acute hepatic injury is also mediated by the TAM system, as recent data regarding acetaminophen toxicity and acute-on-chronic liver failure have uncovered. Soluble TAM-related proteins, mainly released from activated macrophages and hepatic stellate cells after hepatic deterioration, are proposed as early serum markers for disease progression. In conclusion, the TAM system is becoming an interesting pharmacological target in liver pathology and a focus of future biomedical research in this field.

From MASH to HCC: the role of Gas6/TAM receptors

Metabolic dysfunction-associated steatohepatitis (MASH) is the replacement term for what used to be called nonalcoholic steatohepatitis (NASH). It is characterized by inflammation and injury of the liver in the presence of cardiometabolic risk factors and may eventually result in the development of hepatocellular carcinoma (HCC), the most common form of primary liver cancer. Several pathogenic mechanisms are involved in the transition from MASH to HCC, encompassing metabolic injury, inflammation, immune dysregulation and fibrosis. In this context, Gas6 (Growth Arrest-Specific 6) and TAM (Tyro3, Axl, and MerTK) receptors may play important roles. The Gas6/TAM family is involved in the modulation of inflammation, lipid metabolism, fibrosis, tumor progression and metastasis, processes which play an important role in the pathophysiology of acute and chronic liver diseases. In this review, we discuss MASH-associated HCC and the potential involvement of the Gas6/TAM system in disease development and progression. In addition, since therapeutic strategies for MASH and HCC are limited, we also speculate regarding possible future treatments involving the targeting of Gas6 or TAM receptors.

A Phase 2 Study of Sitravatinib in Combination with Nivolumab in Patients with Advanced or Metastatic Urothelial Carcinoma

BACKGROUND AND OBJECTIVE

Checkpoint inhibitor therapy (CPI) has demonstrated survival benefits in urothelial carcinoma (UC); however, not all patients benefit from CPI due to resistance. Combining sitravatinib, a multitargeted receptor tyrosine kinase inhibitor of TYRO3, AXL, and MERTK (TAM) receptors and VEGFR2, with CPI may improve antitumor responses. Our objective was to assess the efficacy and safety of sitravatinib plus nivolumab in patients with advanced/metastatic UC.

METHODS

The 516-003 trial (NCT03606174) is an open-label, multicohort phase 2 study evaluating sitravatinib plus nivolumab in patients with advanced/metastatic UC enrolled in eight cohorts depending on prior treatment with CPI, platinum-based chemotherapy (PBC), or antibody-drug conjugate (ADC). Overall, 244 patients were enrolled and treated with sitravatinib plus nivolumab (median follow-up 14.1-38.2 mo). Sitravatinib (free-base capsules 120 mg once daily [QD] or malate capsule 100 mg QD) plus nivolumab (240 mg every 2 wk/480 mg every 4 wk intravenously).

KEY FINDINGS AND LIMITATIONS

The primary endpoint was objective response rate (ORR; RECIST v1.1). The secondary endpoints included progression-free survival (PFS) and safety. The Predictive probability design and confidence interval methods were used. Among patients previously treated with PBC, ORR, and median PFS were 32.1% and 3.9 mo in CPI-naïve patients (n = 53), 14.9% and 3.9 mo in CPI-refractory patients (n = 67), and 5.4% and 3.7 mo in CPI- and ADC-refractory patients (n = 56), respectively. Across all cohorts, grade 3 treatment-related adverse events (TRAEs) occurred in 51.2% patients and grade 4 in 3.3%, with one treatment-related death (cardiac failure). Immune-related adverse events occurred in 50.4% patients. TRAEs led to sitravatinib/nivolumab discontinuation in 6.1% patients.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Sitravatinib plus nivolumab demonstrated a manageable safety profile but did not result in clinically meaningful ORRs in patients with advanced/metastatic UC in the eight cohorts studied.

PATIENT SUMMARY

In this study, the combination of two anticancer drugs, sitravatinib and nivolumab, resulted in manageable side effects but no meaningful responses in patients with bladder cancer.

Targeting tumor-associated macrophage: an adjuvant strategy for lung cancer therapy

The emergence of immunotherapy has revolutionized the treatment landscape for various types of cancer. Nevertheless, lung cancer remains one of the leading causes of cancer-related mortality worldwide due to the development of resistance in most patients. As one of the most abundant groups of immune cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play crucial and complex roles in the development of lung cancer, including the regulation of immunosuppressive TME remodeling, metabolic reprogramming, neoangiogenesis, metastasis, and promotion of tumoral neurogenesis. Hence, relevant strategies for lung cancer therapy, such as inhibition of macrophage recruitment, TAM reprograming, depletion of TAMs, and engineering of TAMs for drug delivery, have been developed. Based on the satisfactory treatment effect of TAM-targeted therapy, recent studies also investigated its synergistic effect with current therapies for lung cancer, including immunotherapy, radiotherapy, chemotherapy, anti-epidermal growth factor receptor (anti-EGFR) treatment, or photodynamic therapy. Thus, in this article, we summarized the key mechanisms of TAMs contributing to lung cancer progression and elaborated on the novel therapeutic strategies against TAMs. We also discussed the therapeutic potential of TAM targeting as adjuvant therapy in the current treatment of lung cancer, particularly highlighting the TAM-centered strategies for improving the efficacy of anti-programmed cell death-1/programmed cell death-ligand 1 (anti-PD-1/PD-L1) treatment.

Investigation of target genes and potential mechanisms related to compound Xiao-ai-fei honey ointment based on network pharmacology and bioinformatics analysis

BACKGROUND

Compound Xiao-ai-fei honey ointment (CXHO) is an anticancer preparation with a long history in Uyghur folk medicine in China and has been used for the treatment of gastric cancer (GC) in Xinjiang, China. Nevertheless, the mechanism of its anticancer effect remains to be investigated.

METHODS

Bioactive ingredients of CXHO were retrieved from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform database. Target genes of ingredients were acquired via the PubChem and Swiss target prediction database. Gene expression profiling of GC was obtained from GSE54129 in the GEO database and analyzed using the limma package in R. The hub genes associated with CXHO in GC were validated using the TIMER2.0 database, GEPIA2 database and Auto Dock tools. The effect of CXHO on migration of GC cells was detected by Transwell chamber assay and Wound healing assay. The effect of CXHO on expression levels of MMP2/MMP9 and NF-κb, PI3K/AKT signaling pathway was detected by Western blot assay.

RESULTS

Forty-five bioactive ingredients and their 819 related genes were found. A total of 462 differentially expressed genes were identified between GC patients and healthy controls. Seventeen common target genes were identified as hub genes CXHO against GC. Among them, MMP2 and MMP9 were significantly associated with tumor immune infiltrates and had good binding affinity with effective ingredients. Moreover, we validated the mRNA and protein expression levels and prognostic value of MMP2 and MMP9 by different databases. In addition, Kyoto encyclopedia of genes and genomes and gene ontology analyses showed that the 17 common target genes were mainly involved in steroid hormone biosynthesis and cancer-related pathways. Experimental results showed that CXHO inhibited migration of GC cells and down regulated the expression levels of MMP2/MMP9, NF-κb. In addition, CXHO can inhibited PI3K/AKT signaling pathway.

CONCLUSION

We identified and experimental validated 2 pivotal target genes of CXHO against GC and preliminarily analyzed the potential mechanisms by which CXHO inhibits the development of GC. All these findings support CXHO as a promising drug for the treatment of GC.

Altered expression of AXL receptor tyrosine kinase in gastrointestinal cancers: a promising therapeutic target

Gastrointestinal (GI) cancers that include all cancers of the digestive tract organs are generally associated with obesity, lack of exercising, smoking, poor diet, and heavy alcohol consumption. Treatment of GI cancers typically involves surgery followed by chemotherapy and/or radiation. Unfortunately, intrinsic or acquired resistance to these therapies underscore the need for more effective targeted therapies that have been proven in other malignancies. The aggressive features of GI cancers share distinct signaling pathways that are connected to each other by the overexpression and activation of AXL receptor tyrosine kinase. Several preclinical and clinical studies involving anti-AXL antibodies and small molecule AXL kinase inhibitors to test their efficacy in solid tumors, including GI cancers, have been recently carried out. Therefore, AXL may be a promising therapeutic target for overcoming the shortcomings of standard therapies in GI cancers.

MRTX-500 Phase 2 Trial: Sitravatinib With Nivolumab in Patients With Nonsquamous NSCLC Progressing On or After Checkpoint Inhibitor Therapy or Chemotherapy

INTRODUCTION

Sitravatinib, a receptor tyrosine kinase inhibitor targeting TYRO3, AXL, MERTK receptors, and vascular epithelial growth factor receptor 2, can shift the tumor microenvironment toward an immunostimulatory state. Combining sitravatinib with checkpoint inhibitors (CPIs) may augment antitumor activity.

METHODS

The phase 2 MRTX-500 study evaluated sitravatinib (120 mg daily) with nivolumab (every 2 or 4 wk) in patients with advanced nonsquamous NSCLC who progressed on or after previous CPI (CPI-experienced) or chemotherapy (CPI-naive). CPI-experienced patients had a previous clinical benefit (PCB) (complete response, partial response, or stable disease for at least 12 weeks then disease progression) or no PCB (NPCB) from CPI. The primary end point was objective response rate (ORR); secondary objectives included safety and secondary efficacy end points.

RESULTS

Overall, 124 CPI-experienced (NPCB, n = 35; PCB, n = 89) and 32 CPI-naive patients were treated. Investigator-assessed ORR was 11.4% in patients with NPCB, 16.9% with PCB, and 25.0% in CPI-naive. The median progression-free survival was 3.7, 5.6, and 7.1 months with NPCB, PCB, and CPI-naive, respectively; the median overall survival was 7.9 and 13.6 months with NPCB and PCB, respectively (not reached in CPI-naive patients; median follow-up 20.4 mo). Overall, (N = 156), any grade treatment-related adverse events (TRAEs) occurred in 93.6%; grade 3/4 in 58.3%. One grade 5 TRAE occurred in a CPI-naive patient. TRAEs led to treatment discontinuation in 14.1% and dose reduction or interruption in 42.9%. Biomarker analyses supported an immunostimulatory mechanism of action.

CONCLUSIONS

Sitravatinib with nivolumab had a manageable safety profile. Although ORR was not met, this combination exhibited antitumor activity and encouraged survival in CPI-experienced patients with nonsquamous NSCLC.

Clinical and genetic characteristics in pancreatic cancer from Chinese patients revealed by whole exome sequencing

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal malignancies worldwide, mostly as a result of the absence of early detection and specific treatment solutions. Consequently, identifying mutational profiles and molecular biomarkers is essential for increasing the viability of precision therapy for pancreatic cancer.

Methods

We collected blood and tumor tissue samples from 47 Chinese pancreatic cancer patients and used whole-exome sequencing (WES) to evaluate the genetic landscape.

Results

Our results showed the most frequently somatic alteration genes were KRAS (74.5%), TP53(51.1%), SMAD4 (17%), ARID1A (12.8%), CDKN2A (12.8%), TENM4 (10.6%), TTN (8.5%), RNF43(8.5%), FLG (8.5%) and GAS6 (6.4%) in Chinese PDAC patients. We also found that three deleterious germline mutations (ATM c.4852C>T/p. R1618*, WRN c.1105C>T/p. R369*, PALB2 c.2760dupA/p. Q921Tfs*7) and two novel fusions (BRCA1-RPRML, MIR943 (intergenic)-FGFR3). When compared to the Cancer Genome Atlas (TCGA) database, there is a greater mutation frequency of TENM4 (10.6% vs. 1.6%, p = 0.01), GAS6(6.4% vs. 0.5%, p = 0.035), MMP17(6.4% vs. 0.5%, p = 0.035), ITM2B (6.4% vs. 0.5%, p = 0.035) and USP7 (6.4% vs. 0.5%, p= 0.035) as well as a reduced mutation frequency of SMAD4 (17.0% vs. 31.5%, p = 0.075) and CDKN2A (12.8% vs. 47.3%, p < 0.001) were observed in the Chinese cohort. Among the 41 individuals examined for programmed cell death ligand 1(PD-L1) expression, 15 (36.6%) had positive PD-L1 expression. The median tumor mutational burden (TMB) was found to be 12muts (range, 0124). The TMB index was higher in patients with mutant-type KRAS MUT/TP53 MUT (p < 0.001), CDKN2A (p = 0.547), or SMAD4 (p = 0.064) compared to patients with wild-type KRAS/TP53, CDKN2A, or SMAD4.

Conclusions

We exhibited real-world genetic traits and new alterations in Chinese individuals with cancer of the pancreas, which might have interesting implications for future individualized therapy and medication development.

Gas6/AXL pathway: immunological landscape and therapeutic potential

Cancer is a disease with ecological and evolutionary unity, which seriously affects the survival and quality of human beings. Currently, many reports have suggested Gas6 plays an important role in cancer. Binding of gas6 to TAM receptors is associated with the carcinogenetic mechanisms of multiple malignancies, such as in breast cancer, chronic lymphocytic leukemia, non-small cell lung cancer, melanoma, prostate cancer, etc., and shortened overall survival. It is accepted that the Gas6/TAM pathway can promote the malignant transformation of various types of cancer cells. Gas6 has the highest affinity for Axl, an important member of the TAM receptor family. Knockdown of the TAM receptors Axl significantly affects cell cycle progression in tumor cells. Interestingly, Gas6 also has an essential function in the tumor microenvironment. The Gas6/AXL pathway regulates angiogenesis, immune-related molecular markers and the secretion of certain cytokines in the tumor microenvironment, and also modulates the functions of a variety of immune cells. In addition, evidence suggests that the Gas6/AXL pathway is involved in tumor therapy resistance. Recently, multiple studies have begun to explore in depth the importance of the Gas6/AXL pathway as a potential tumor therapeutic target as well as its broad promise in immunotherapy; therefore, a timely review of the characteristics of the Gas6/AXL pathway and its value in tumor treatment strategies is warranted. This comprehensive review assessed the roles of Gas6 and AXL receptors and their associated pathways in carcinogenesis and cancer progression, summarized the impact of Gas6/AXL on the tumor microenvironment, and highlighted the recent research progress on the relationship between Gas6/AXL and cancer drug resistance.

TYRO3 promotes tumorigenesis and drug resistance in colorectal cancer by enhancing the epithelial-mesenchymal transition process

Colorectal cancer (CRC) is a leading cause of cancer mortality worldwide. Although considerable advances in CRC treatment have been achieved, effective treatment improvement has hit a bottleneck. This study demonstrated that TYRO3 expression was aberrantly increased in CRC tissues with prognosis association. The prediction model of prognosis for CRC patients was constructed based on TYRO3 expression. The model suggested that the TYRO3 level is crucial to the final prediction results. We observed that knockdown TYRO3 expression could inhibit the proliferation and migration ability and reverse the drug resistance by constructing drug-resistant CRC cell lines. In vivo experiments also confirmed this conclusion. Thus, targeting TYRO3 combined with 5-Fu treatment could provide a better therapeutic effect. Additionally, TYRO3 could inhibit the EMT process by down-regulating ENO1, which may be achieved by interfering with energy metabolism in cancer cells. Therefore, the current study provides a theoretical basis for TYRO3 in drug-resistance of CRC cells and highlights a new strategy for CRC-targeted therapy.

Axl alleviates DSS-induced colitis by preventing dysbiosis of gut microbiota

Axl is a tyrosine kinase receptor, a negative regulator for innate immune responses and inflammatory bowel disease (IBD). The gut microbiota regulates intestinal immune homeostasis, but the role of Axl in the pathogenesis of IBD through the regulation of gut microbiota composition remains unresolved. In this study, mice with DSS-induced colitis showed increased Axl expression, which was almost entirely suppressed by depleting the gut microbiota with antibiotics. Axl^-/- mice without DSS administration exhibited increased bacterial loads, especially the Proteobacteria abundant in patients with IBD, significantly consistent with DSS-induced colitis mice. Axl^-/- mice also had an inflammatory intestinal microenvironment with reduced antimicrobial peptides and overexpression of inflammatory cytokines. The onset of DSS-induced colitis occurred faster with an abnormal expansion of Proteobacteria in Axl^-/- mice than in WT mice. These findings suggest that a lack of Axl signaling exacerbates colitis by inducing aberrant compositions of the gut microbiota in conjunction with an inflammatory gut microenvironment. In conclusion, the data demonstrated that Axl signaling could ameliorate the pathogenesis of colitis by preventing dysbiosis of gut microbiota. Therefore, Axl may act as a potential novel biomarker for IBD and can be a potential candidate for the prophylactic or therapeutic target of diverse microbiota dysbiosis-related diseases.

Decreased Gas6 and sAxl Plasma Levels Are Associated with Hair Loss in COVID-19 Survivors

Post-acute conditions after coronavirus disease 2019 (COVID-19) are quite common, although the underlying pathogenetic mechanisms leading to these conditions are not yet completely understood. In this prospective observational study, we aimed to test the hypothesis that Growth Arrest-Specific 6 (Gas6) and its soluble receptors, Axl (sAxl) and MerTK (sMer), might be implicated. A total of 263 subjects underwent a structured clinical evaluation one year after their hospital discharge for COVID-19, and they consented to donate a blood sample to measure their circulating Gas6, sAxl, and sMer levels. A total of 98 (37.3%) post-COVID-19 subjects complained of at least one residual physical symptom one year after their hospital discharge. Univariate analysis revealed that sAxl was marginally associated with residual symptoms, but at the level of logistic regression analysis, only the diffusing capacity of the lungs for carbon monoxide (DLCO) (OR 0.98, CI 95%: 0.96–0.99; p = 0.007) and the female sex (OR 2.49, CI 95%: 1.45–4.28; p = 0.001) were independently associated with long-lasting symptoms. A total of 69 (26.2%) subjects had hair loss. At the level of univariate analysis, Gas6, sAxl, DLCO, and the female gender were associated with its development. In a logistic regression analysis model, Gas6 (OR 0.96, CI 95%: 0.92–0.99; p = 0.015) and sAxl (OR 0.98, CI 95%; 0.97–1.0; p = 0.014), along with the female sex (OR 6.58, CI 95%: 3.39–12.78; p = 0.0001), were independent predictors of hair loss. Decreased levels of Gas6 and sAxl were associated with a history of hair loss following COVID-19. This was resolved spontaneously in most patients, although 23.7% complained of persistent hair loss one year after hospital discharge.

Whole-Exome Sequencing in Family Trios Reveals De Novo Mutations Associated with Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease characterized by insulin deficiency and loss of pancreatic islet β-cells. The objective of this study is to identify de novo mutations in 13 trios from singleton families that contribute to the genetic basis of T1DM through the application of whole-exome sequencing (WES). Of the 13 families sampled for this project, 12 had de novo variants, with Family 7 having the highest number (nine) of variants linked to T1DM/autoimmune pathways, whilst Family 4 did not have any variants past the filtering steps. There were 10 variants of 7 genes reportedly associated with T1DM (MST1; TDG; TYRO3; IFIHI; GLIS3; VEGFA; TYK2). There were 20 variants of 13 genes that were linked to endocrine, metabolic, or autoimmune diseases. Our findings demonstrate that trio-based WES is a powerful approach for identifying new candidate genes for the pathogenesis of T1D. Genotyping and functional annotation of the discovered de novo variants in a large cohort is recommended to ascertain their association with disease pathogenesis.

The Gut Microbiome and Metastatic Renal Cell Carcinoma

The introduction of targeted therapy (TT) and immuno-oncology (IO) agents have revolutionized the treatment of metastatic renal cell carcinoma (mRCC). However, despite the significant improvements in survival and clinical response yielded by these agents, a significant percentage of patients still experience progressive disease. Evidence now suggests that microorganisms living in the gut (i.e., the gut microbiome) could be used as a biomarker for response and may also have utility in increasing response to these treatments. In this review, we present an overview of the role of the gut microbiome in cancer and its potential implications in the treatment of mRCC.

Preclinical Characterization of XL092, a Novel Receptor Tyrosine Kinase Inhibitor of MET, VEGFR2, AXL, and MER

The multi-receptor tyrosine kinase inhibitor XL092 has been developed to inhibit the activity of oncogenic targets, including MET, VEGFR2, and the TAM family of kinases TYRO3, AXL and MER. Presented here is a preclinical evaluation of XL092. XL092 causes a significant decrease in tumor MET and AXL phosphorylation (P < 0.01) in murine Hs 746T xenograft models relative to vehicle, and a 96% inhibition of VEGFR2 phosphorylation in murine lungs. Dose-dependent tumor growth inhibition with XL092 was observed in various murine xenograft models, with dose-dependent tumor regression seen in the NCI-H441 model. Tumor growth inhibition was enhanced with the combination of XL092 with anti-PD-1, anti-programmed death ligand-1 (PD-L1), or anti-CTLA-4 compared with any of these agents alone in the MC38 murine syngeneic model and with anti-PD-1 in the CT26 colorectal cancer survival model. In vivo, XL092 promoted a decrease in the tumor microvasculature and significant increases of peripheral CD4+ T cells and B cells and decreases in myeloid cells versus vehicle. Significant increases in CD8+ T cells were also observed with XL092 plus anti-PD-1 or anti-PD-L1 versus vehicle. In addition, XL092 promoted M2 to M1 repolarization of macrophages in vitro and inhibited primary human macrophage efferocytosis in a dose-dependent manner. In summary, XL092 was shown to have significant antitumor and immunomodulatory activity in animal models both alone and in combination with immune checkpoint inhibitors, supporting its evaluation in clinical trials.

Phosphatidylserine-mediated oral tolerance

Phosphatidylserine (PS) is an anionic phospholipid exposed on the surface of apoptotic cells. The exposure of PS typically recruits and signals phagocytes to engulf and silently clear these dying cells to maintain tolerance via immunological ignorance. However, recent and emerging evidence has demonstrated that PS converts an "immunogen" into a "tolerogen", and PS exposure on the surface of cells or vesicles actively promotes a tolerogenic environment. This tolerogenic property depends on the biophysical characteristics of PS-containing vesicles, including PS density on the particle surface to effectively engage tolerogenic receptors, such as TIM-4, which is exclusively expressed on the surface of antigen-presenting cells. We harnessed the cellular and molecular mechanistic insight of PS-mediated immune regulation to design an effective oral tolerance approach. This immunotherapy has been shown to prevent/reduce immune response against life-saving protein-based therapies, food allergens, autoantigens, and the antigenic viral capsid peptide commonly used in gene therapy, suggesting a broad spectrum of potential clinical applications. Given the good safety profile of PS together with the ease of administration, oral tolerance achieved with PS-based nanoparticles has a very promising therapeutic impact.

GAS6/TAM signaling pathway controls MICA expression in multiple myeloma cells

NKG2D ligands play a relevant role in Natural Killer (NK) cell -mediated immune surveillance of multiple myeloma (MM). Different levels of regulation control the expression of these molecules at cell surface. A number of oncogenic proteins and miRNAs act as negative regulators of NKG2D ligand transcription and translation, but the molecular mechanisms sustaining their basal expression in MM cells remain poorly understood. Here, we evaluated the role of the growth arrest specific 6 (GAS6)/TAM signaling pathway in the regulation of NKG2D ligand expression and MM recognition by NK cells. Our data showed that GAS6 as well as MERTK and AXL depletion in MM cells results in MICA downregulation and inhibition of NKG2D-mediated NK cell degranulation. Noteworthy, GAS6 derived from bone marrow stromal cells (BMSCs) also increases MICA expression at both protein and mRNA level in human MM cell lines and in primary malignant plasma cells. NF-kB activation is required for these regulatory mechanisms since deletion of a site responsive for this transcription factor compromises the induction of mica promoter by BMSCs. Accordingly, knockdown of GAS6 reduces the capability of BMSCs to activate NF-kB pathway as well as to enhance MICA expression in MM cells. Taken together, these results shed light on molecular mechanism underlying NKG2D ligand regulation and identify GAS6 protein as a novel autocrine and paracrine regulator of basal expression of MICA in human MM cells.

Addressing CPI resistance in NSCLC: targeting TAM receptors to modulate the tumor microenvironment and future prospects

Lung cancer remains a leading cause of cancer death worldwide, with non-small-cell lung cancer (NSCLC) accounting for the majority of cases. Immune checkpoint inhibitors (CPIs), including those targeting programmed cell death protein-1 and its ligand (PD-1/PD-L1), have revolutionized the treatment landscape for various cancers. Notably, PD-1/PD-L1 inhibitor-based regimens now form the standard first-line therapy for metastatic NSCLC, substantially improving patients' overall survival. Despite the progress made using CPI-based therapies in advanced NSCLC, most patients experience disease progression after an initial response due to resistance. Given the currently limited therapeutic options available for second-line and beyond settings in NSCLC, new treatment approaches are needed to improve long-term survival in these patients. Thus, CPI resistance is an emerging concept in cancer treatment and an active area of clinical research.Among the key mechanisms of CPI resistance is the immunosuppressive tumor microenvironment (TME). Effective CPI therapy is based on shifting immune responses against cancer cells, therefore, manipulating the immunosuppressive TME comprises an important strategy to combat CPI resistance. Several aspects of the TME can contribute to treatment resistance in NSCLC, including through the activation of Tyro3, Axl, MerTK (TAM) receptors which are essential pleiotropic regulators of immune homeostasis. Their roles include negatively modulating the immune response, therefore ectopic expression of TAM receptors in the context of cancer can contribute to the immunosuppressive, protumorigenic TME. Furthermore, TAM receptors represent important candidates to simultaneously target both tumor cells and immune cells in the TME. Clinical development of TAM receptor inhibitors (TAM RIs) is increasingly focused on their ability to rescue the antitumor immune response, thereby shifting the immunosuppressive TME to an immunostimulatory TME. There is a strong biological rationale for combining TAM RIs with a CPI to overcome resistance and improve long-term clinical responses in NSCLC. Combinatorial clinical trials of TAM RIs with CPIs are underway with encouraging preliminary results. This review outlines the key mechanisms of CPI resistance, including the role of the immunosuppressive TME, and discusses the rationale for targeting TAM receptors as a novel, promising therapeutic strategy to overcome CPI resistance in NSCLC.

Glioblastoma: Pitfalls and Opportunities of Immunotherapeutic Combinations

Glioblastoma multiforme (GBM) is the most common and aggressive primary central nervous system tumour in adults. It has extremely poor prognosis since the current standard of care, comprising of gross total resection and temozolomide (TMZ) chemoradiotherapy, prolongs survival, but does not provide a durable response. To a certain extent, this is due to GBM's heterogeneous, hostile and cold tumour microenvironment (TME) and the unique ability of GBM to overcome the host's immune responses. Therefore, there is an urgent need to develop more effective therapeutic approaches. This review provides critical insights from completed and ongoing clinical studies investigating novel immunotherapy strategies for GBM patients, ranging from the use of immune checkpoint inhibitors in different settings of GBM treatment to novel combinatorial therapies. In particular, we discuss how treatment regimens based on single antigen peptide vaccines evolved into fully personalised, polyvalent cell-based vaccines, CAR-T cell, and viral or gene therapies. Furthermore, the results of the most influential clinical trials and a selection of innovative preclinical studies aimed at activating the immunologically cold GBM microenvironment are reviewed.

Rational Combinations of Targeted Therapy and Immune Checkpoint Inhibitors in Head and Neck Cancers

Immunotherapy, especially the immune checkpoint inhibitors (ICIs) such as the pembrolizumab and nivolumab have contributed to significant improvements in treatment outcomes and survival of head and neck cancer (HNC) patients. Still, only a subset of patients benefits from ICIs and hence the race is on to identify combination therapies that could improve response rates. Increasingly, genetic alterations that occur within cancer cells have been shown to modulate the tumor microenvironment resulting in immune evasion, and these have led to the emergence of trials that rationalize a combination of targeted therapy with immunotherapy. In this review, we aim to provide an overview of the biological rationale and current strategies of combining targeted therapy with the approved ICIs in HNC. We summarize the ongoing combinatorial clinical trials and discuss emerging immunomodulatory targets. We also discuss the challenges and gaps that have yet to be addressed, as well as future perspectives in combining these different drug classes.

Circadian and Immunity Cycle Talk in Cancer Destination: From Biological Aspects to In Silico Analysis

Simple Summary

The circadian cycle is a natural cycle of the body repeated every 24 h, based on a day and night rhythm, and it affects many body processes. The present article reviews the importance and role of the circadian cycle in cancer and its association with the immune system and immunotherapy drugs at the cellular and molecular levels. It also examines the genes and cellular pathways involved in both circadian and immune systems. It offers possible computational solutions to increase the effectiveness of cancer treatment concerning the circadian cycle.

Abstract

Cancer is the leading cause of death and a major problem to increasing life expectancy worldwide. In recent years, various approaches such as surgery, chemotherapy, radiation, targeted therapies, and the newest pillar, immunotherapy, have been developed to treat cancer. Among key factors impacting the effectiveness of treatment, the administration of drugs based on the circadian rhythm in a person and within individuals can significantly elevate drug efficacy, reduce adverse effects, and prevent drug resistance. Circadian clocks also affect various physiological processes such as the sleep cycle, body temperature cycle, digestive and cardiovascular processes, and endocrine and immune systems. In recent years, to achieve precision patterns for drug administration using computational methods, the interaction of the effects of drugs and their cellular pathways has been considered more seriously. Integrated data-derived pathological images and genomics, transcriptomics, and proteomics analyses have provided an understanding of the molecular basis of cancer and dramatically revealed interactions between circadian and immunity cycles. Here, we describe crosstalk between the circadian cycle signaling pathway and immunity cycle in cancer and discuss how tumor microenvironment affects the influence on treatment process based on individuals’ genetic differences. Moreover, we highlight recent advances in computational modeling that pave the way for personalized immune chronotherapy.

A FBXO7/EYA2-SCFFBXW7 axis promotes AXL-mediated maintenance of mesenchymal and immune evasion phenotypes of cancer cells

A mesenchymal tumor phenotype associates with immunotherapy resistance, although the mechanism is unclear. Here, we identified FBXO7 as a maintenance regulator of mesenchymal and immune evasion phenotypes of cancer cells. FBXO7 bound and stabilized SIX1 co-transcriptional regulator EYA2, stimulating mesenchymal gene expression and suppressing IFNα/β, chemokines CXCL9/10, and antigen presentation machinery, driven by AXL extracellular ligand GAS6. Ubiquitin ligase SCFFBXW7 antagonized this pathway by promoting EYA2 degradation. Targeting EYA2 Tyr phosphatase activity decreased mesenchymal phenotypes and enhanced cancer cell immunogenicity, resulting in attenuated tumor growth and metastasis, increased infiltration of cytotoxic T and NK cells, and enhanced anti-PD-1 therapy response in mouse tumor models. FBXO7 expression correlated with mesenchymal and immune-suppressive signatures in patients with cancer. An FBXO7-immune gene signature predicted immunotherapy responses. Collectively, the FBXO7/EYA2-SCFFBXW7 axis maintains mesenchymal and immune evasion phenotypes of cancer cells, providing rationale to evaluate FBXO7/EYA2 inhibitors in combination with immune-based therapies to enhance onco-immunotherapy responses.

Homology Modelling, Docking-based Virtual Screening, ADME Properties, and Molecular Dynamics Simulation for Identification of Probable Type II Inhibitors of AXL Kinase

Background:

AXL kinase is an important member of the TAM family for kinases which is involved in most cancers. Considering its role in different cancers due to its pro-tumorigenic effects and its involvement in the resistance, it has gained importance recently. Majority of research carried out is on Type I inhibitors and limited studies have been carried out for Type II inhibitors. Taking this into consideration, we have attempted to build Homology models to identify the Type II inhibitors for the AXL kinase.

Methods:

Homology Models for DFG-out C-helix-in/out state were developed using SWISS Model, PRIMO, and Prime. These models were validated by different methods and further evaluated for stability by molecular dynamics simulation using Desmond software. Selected models PED1-EB and PEDI1-EB were used for the docking-based virtual screening of four compound libraries using Glide software. The hits identified were subjected to interaction analysis and shortlisted compounds were subjected to Prime MM-GBSA studies for energy calculation. These compounds were also docked in the DFG-in state to check for binding and elimination of any compounds that may not be Type II inhibitors. The Prime energies were calculated for these complexes as well and some compounds were eliminated. ADMET studies were carried out using Qikprop. Some selected compounds were subjected to molecular dynamics simulation using Desmond for evaluating the stability of the complexes.

Results:

Out of 78 models inclusive of both DFG-out C-helix-in and DFG-out C-helix-out, 5 models were identified after different types of evaluation as well as validation studies. 1 model representing each type (PED1-EB and PEDI1-EB) was selected for the screening studies. The screening studies resulted in the identification of 29 compounds from the screen on PED1-EB and 10 compounds from the screen on PEDI1-EB. Hydrogen bonding interactions with Pro621, Met623, and Asp690 were observed for these compounds primarily. In some compounds, hydrogen bonding with Leu542, Glu544, Lys567, and Asn677 as well as pi-pi stacking interactions with either Phe622 or Phe691 were also seen. 4 compounds identified from PED1-EB screen were subjected to molecular dynamics simulation and their interactions were found to be consistent during the simulation. 2 compounds identified from PEDI1-EB screen were also subjected to the simulation studies, however, their interactions with Asp690 were not observed for a significant time and in both cases differed from the docked pose.

Conclusion:

Multiple models of DFG-out conformations of AXL kinase were built, validated and used for virtual screening. Different compounds were identified in the virtual screening, which may possibly act as Type II inhibitors for AXL kinase. Some more experimental studies can be done to validate these findings in future. This study will play a guiding role in the further development of the newer Type II inhibitors of the AXL kinase for the probable treatment of cancer.

Up-regulated serum levels of TAM receptor tyrosine kinases in a group of Egyptian autistic children

TAM receptor family belongs to receptor tyrosine kinases (TAMRTKs). It includes three receptors; Tyro-3, Axl and Mer. TAMRTKs has a great role in resolution of inflammation due to their role in clearance of apoptotic cells by macrophages. Dysregulated TAM signaling pathways are associated with many autoimmune diseases and chronic inflammatory disorders. Autism may be an autoimmune disease in some patients. This work was the first study that investigated serum levels of the soluble ectodomain shed TAMRTKs in a group of autistic children. Serum levels of TAMRTKs were measured by ELISA in 30 autistic children aged between 3.5 and 11 years and 30 age and sex-matched healthy control children. Serum levels of TAMRTKs were significantly higher in autistic children than healthy control children (P < 0.001). Patients with severe autism had significantly higher serum levels of TAMRTKs than patients with mild to moderate autism (P < 0.01). In addition, there were significant positive correlations between scores of the Childhood Autism Rating Scale (CARS) and serum levels of TAMRTKs in autistic patients, (P < 0.01). In conclusions, serum levels of TAMRTKs were up-regulated in autistic children with significant positive correlations with the degree of the disease severity. This initial report requires further studies to investigate the relationship between TAMRTKs and autism.

Metabolic manipulation of the tumour immune microenvironment

In the past few years, the evolution of immunotherapy has resulted in a shift in cancer treatment models. However, with immunosuppressive effects of the tumour microenvironment continue to limit advances in tumour immunotherapy. The tumour microenvironment induces metabolic reprogramming in cancer cells, which results in competition for nutrients between tumour cells and host immunocytes. Metabolic and waste products originating in tumour cells can influence the activation and effector properties of immunocytes in numerous ways and ultimately promote the survival and propagation of tumour cells. In this paper, we discuss metabolic reprogramming in tumour cells and the influence of metabolite byproducts on the immune microenvironment, providing novel insights into tumour immunotherapy.

Barriers to Immunotherapy in Ovarian Cancer: Metabolic, Genomic, and Immune Perturbations in the Tumour Microenvironment

A lack of explicit early clinical signs and effective screening measures mean that ovarian cancer (OC) often presents as advanced, incurable disease. While conventional treatment combines maximal cytoreductive surgery and platinum-based chemotherapy, patients frequently develop chemoresistance and disease recurrence. The clinical application of immune checkpoint blockade (ICB) aims to restore anti-cancer T-cell function in the tumour microenvironment (TME). Disappointingly, even though tumour infiltrating lymphocytes are associated with superior survival in OC, ICB has offered limited therapeutic benefits. Herein, we discuss specific TME features that prevent ICB from reaching its full potential, focussing in particular on the challenges created by immune, genomic and metabolic alterations. We explore both recent and current therapeutic strategies aiming to overcome these hurdles, including the synergistic effect of combination treatments with immune-based strategies and review the status quo of current clinical trials aiming to maximise the success of immunotherapy in OC.

Immune Evasion Mechanism and AXL

Extensive interest in cancer immunotherapy is reported according to the clinical importance of CTLA-4 and (PD-1/PD-L1) [programmed death (PD) and programmed death-ligand (PD-L1)] in immune checkpoint therapies. AXL is a receptor tyrosine kinase expressed in different types of cancer and in relation to resistance against various anticancer therapeutics due to poor clinical prognosis. AXL and its ligand, i.e., growth arrest-specific 6 (GAS6) proteins, are expressed on many cancer cells, and the GAS6/AXL pathway is reported to promote cancer cell proliferation, survival, migration, invasion, angiogenesis, and immune evasion. AXL is an attractive and novel therapeutic target for impairing tumor progression from immune cell contracts in the tumor microenvironment. The GAS6/AXL pathway is also of interest immunologically because it targets fewer antitumor immune responses. In effect, several targeted therapies are selective and nonselective for AXL, which are in preclinical and clinical development in multiple cancer types. Therefore, this review focuses on the role of the GAS6/AXL signaling pathway in triggering the immunosuppressive tumor microenvironment as immune evasion. This includes regulating its composition and activating T-cell exclusion with the immune-suppressive activity of regulatory T cells, which is related to one of the hallmarks of cancer survival. Finally, this article discusses the GAS6/AXL signaling pathway in the context of several immune responses such as NK cell activation, apoptosis, and tumor-specific immunity, especially PD-1/PDL-1 signaling.

Cabozantinib plus immunotherapy combinations in metastatic renal cell and urothelial carcinoma

Treatment options for metastatic renal cell carcinoma (mRCC) and metastatic urothelial carcinoma (mUC) have increased dramatically over the past decade. However, even when novel approaches have proven to be effective as monotherapy, many patients still develop progressive disease, and different strategies are needed to increase clinical response and quality of life. Strategies combining targeted therapy (TT) and immunotherapy (IO) have emerged as a way to shorten the gap between responders and nonresponders to monotherapy and have reported promising results. In this review, we discuss the current role of cabozantinib in combination with IO agents in the treatment of metastatic RCC and UC and go over future directions in the field.

Targeting MERTK and AXL in EGFR Mutant Non-Small Cell Lung Cancer

MERTK and AXL are members of the TAM family of receptor tyrosine kinases and are abnormally expressed in 69% and 93% of non-small cell lung cancers (NSCLCs), respectively. Expression of MERTK and/or AXL provides a survival advantage for NSCLC cells and correlates with lymph node metastasis, drug resistance, and disease progression in patients with NSCLC. The TAM receptors on host tumor infiltrating cells also play important roles in the immunosuppressive tumor microenvironment. Thus, MERTK and AXL are attractive biologic targets for NSCLC treatment. Here, we will review physiologic and oncologic roles for MERTK and AXL with an emphasis on the potential to target these kinases in NSCLCs with activating EGFR mutations.

RIPK3 and AXL Expression Study in Primary Cutaneous Melanoma Unmasks AXL as Predictor of Sentinel Node Metastasis: A Pilot Study

Malignant melanoma (MM) is the most lethal skin cancer. AXL is a tyrosine kinase receptor involved in several oncogenic processes and might play a role in blocking necroptosis (a regulated cell death mechanism) in MM through the downregulation of the necroptotic-related driver RIPK3. The aim of this study was to evaluate the clinical impact of the expression of AXL and RIPK3 in 108 primary cutaneous MMs. Association between AXL and RIPK3 immunoreactivity and clinical-pathological variables, sentinel lymph node status, and tumor-infiltrating lymphocytes (TILs) was assessed. Immunoreaction in tumor cells was detected in 30 cases (28%; range, 5%-80%) and in 17 cases (16%; range, 5%-50%) for AXL and RIPK3, respectively. Metastases in the sentinel lymph nodes were detected in 14 out of 61 patients, and these were associated with AXL-positive immunoreactivity in the primary tumor (p < 0.0001). No association between AXL and TILs was found. RIPK3 immunoreactivity was not associated with any variables. A final logistic regression analysis showed Breslow and AXL-positive immunoreactivity as the stronger predictor for positive sentinel node status [area under the receiver operating characteristic curve (AUC) of 0.96]. AXL could be a potential new biomarker for MM risk assessment, and it deserves to be further investigated in larger studies.

Antitumor immune effects of preoperative sitravatinib and nivolumab in oral cavity cancer: SNOW window-of-opportunity study

BACKGROUND

Sitravatinib, a tyrosine kinase inhibitor that targets TYRO3, AXL, MERTK and the VEGF receptor family, is predicted to increase the M1 to M2-polarized tumor-associated macrophages ratio in the tumor microenvironment and have synergistic antitumor activity in combination with anti-programmed death-1/ligand-1 agents. SNOW is a window-of-opportunity study designed to evaluate the immune and molecular effects of preoperative sitravatinib and nivolumab in patients with oral cavity squamous cell carcinoma.

METHODS

Patients with newly-diagnosed untreated T2-4a, N0-2 or T1 >1 cm-N2 oral cavity carcinomas were eligible. All patients received sitravatinib 120 mg daily from day 1 up to 48 hours pre-surgery and one dose of nivolumab 240 mg on day 15. Surgery was planned between day 23 and 30. Standard of care adjuvant radiotherapy was given based on clinical stage. Tumor photographs, fresh tumor biopsies and blood samples were collected at baseline, at day 15 after sitravatinib alone, and at surgery after sitravatinib-nivolumab combination. Tumor flow cytometry, multiplex immunofluorescence staining and single-cell RNA sequencing (scRNAseq) were performed on tumor biopsies to study changes in immune-cell populations. Tumor whole-exome sequencing and circulating tumor DNA and cell-free DNA were evaluated at each time point.

RESULTS

Ten patients were included. Grade 3 toxicity occurred in one patient (hypertension); one patient required sitravatinib dose reduction, and one patient required discontinuation and surgery delay due to G2 thrombocytopenia. Nine patients had clinical-to-pathological downstaging, with one complete response. Independent pathological treatment response (PTR) assessment confirmed a complete PTR and two major PTRs. With a median follow-up of 21 months, all patients are alive with no recurrence. Circulating tumor DNA and cell-free DNA dynamics correlated with clinical and pathological response and distinguished two patient groups with different tumor biological behavior after sitravatinib alone (1A) versus sitravatinib-nivolumab (1B). Tumor immunophenotyping and scRNAseq analyses revealed differential changes in the expression of immune cell populations and sitravatinib-targeted and hypoxia-related genes in group 1A vs 1B patients.

CONCLUSIONS

The SNOW study shows sitravatinib plus nivolumab is safe and leads to deep clinical and pathological responses in oral cavity carcinomas. Multi-omic biomarker analyses dissect the differential molecular effects of sitravatinib versus the sitravatinib-nivolumab and revealed patients with distinct tumor biology behavior.

TRIAL REGISTRATION NUMBER

NCT03575598.

Antitumor effects of the multi-target tyrosine kinase inhibitor cabozantinib: a comprehensive review of the preclinical evidence

INTRODUCTION

Altered receptor tyrosine kinase (RTK) signaling contributes to tumorigenesis and suppression of immune-mediated destruction of cancer cells. Cabozantinib is an oral tyrosine kinase inhibitor that inhibits several RTKs involved in tumorigenesis, and is approved for the treatment of patients with progressive metastatic medullary thyroid cancer, advanced renal cell carcinoma, and hepatocellular carcinoma that has been previously treated with sorafenib.

AREAS COVERED

We present an up-to-date evaluation of preclinical evidence for RTK inhibition with cabozantinib, specifically VEGFR, MET, KIT, RET, AXL, FLT3, and associated antitumor effects. Preclinical investigations of cabozantinib in combination with other anticancer drugs are also reviewed.

EXPERT OPINION

Preclinical evidence shows that cabozantinib has antitumor activity against various cancer cells and exhibits synergy with other anticancer agents, including immune checkpoint inhibitors and hormone receptor or metabolic pathway inhibitors. Further optimization of cabozantinib treatment requires the identification of biomarkers of response and resistance, and exploration of complementary drug targets. Investigation of mechanisms of adaptive resistance, such as epithelial to mesenchymal transition (cancer intrinsic) and immunomodulation by the tumor microenvironment (cancer extrinsic), as well as identification of novel drug targets based on characterization of cancer stem cell metabolomic phenotypes, appear to be promising approaches.

Aberrant expression of PROS1 correlates with human papillary thyroid cancer progression

Background

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer (TC). Considering the important association between cellular immunity and PTC progression, it is worth exploring the biological significance of immune-related signaling in PTC.

Methods

Several bioinformatics tools, such as R software, WEB-based Gene SeT AnaLysis Toolkit (WebGestalt), Database for Annotation, Visualization and Integrated Discovery (DAVID), Search Tool for the Retrieval of Interacting Genes (STRING) and Cytoscape were used to identify the immune-related hub genes in PTC. Furthermore, in vitro experiments were adopted to identify the proliferation and migration ability of PROS1 knockdown groups and control groups in PTC cells.

Results

The differentially expressed genes (DEGs) of five datasets from Gene Expression Omnibus (GEO) contained 154 upregulated genes and 193 downregulated genes, with Protein S (PROS1) being the only immune-related hub gene. Quantitative real-time polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC) have been conducted to prove the high expression of PROS1 in PTC. Moreover, PROS1 expression was significantly correlated with lymph nodes classification. Furthermore, knockdown of PROS1 by shRNAs inhibited the cell proliferation and cell migration in PTC cells.

Conclusions

The findings unveiled the clinical relevance and significance of PROS1 in PTC and provided potential immune-related biomarkers for PTC development and prognosis.

Subcritical Water Extracts from Agaricus blazei Murrill's Mycelium Inhibit the Expression of Immune Checkpoint Molecules and Axl Receptor

Agaricus blazei Murrill or Himematsutake is an edible and medicinal mushroom. Agaricus blazei Murrill’s fruiting body extracts have anticancer properties, although the mechanism is unknown. Basic or organic solvents, which are hazardous for human health, are generally used to prepare Agaricus blazei Murrill’s extracts. The inhibition of immune checkpoint molecules and Axl receptor is an effective therapy in cancer. This study assessed whether subcritical water extracts of the Agaricus blazei Murrill’s fruiting body or mycelium affect the expression of Axl and immune checkpoint molecules in lung cancer cells. We used A549 cells and mouse bone marrow-derived dendritic cells in the experiments. We prepared subcritical water extracts from the Agaricus blazei Murrill’s fruiting body or mycelium. The subcritical water extracts from the Agaricus blazei Murrill’s fruiting body or mycelium significantly inhibited the expression of immune checkpoint molecules and Axl compared to saline-treated cells. Additionally, the hot water extract, subcritical water extract, and the hot water extraction residue subcritical water extract from the Agaricus blazei Murrill’s mycelium significantly enhanced the expression of maturation markers in dendritic cells. These observations suggest that the subcritical water extract from Agaricus blazei Murrill’s mycelium is a promising therapeutic tool for stimulating the immune response in cancer.

A structural perspective on the design of decoy immune modulators

Therapeutic mAbs have dominated the class of immunotherapeutics in general and immune checkpoint inhibitors in particular. The high specificity of mAbs to the target molecule as well as their extended half-life and (or) the effector functions raised by the Fc part are some of the important aspects that contribute to the success of this class of therapeutics. Equally potential candidates are decoys and their fusions that can address some of the inherent limitations of mAbs, like immunogenicity, resistance development, low bio-availability and so on, besides maintaining the advantages of mAbs. The decoys are molecules that trap the ligands and prevent them from interacting with the signaling receptors. Although a few FDA-approved decoy immune modulators are very successful, the potential of this class of drugs is yet to be fully realized. Here, we review various strategies employed in fusion protein therapeutics with a focus on the design of decoy immunomodulators from the structural perspective and discuss how the information on protein structure and function can strategically guide the development of next-generation immune modulators.

OVOL2 inhibits macrophage M2 polarization by regulating IL-10 transcription, and thus inhibits the tumor metastasis by modulating the tumor microenvironment

Invasion and metastasis of breast cancer cells is an important cause of death in breast cancer patients. In the tumor microenvironment, M2 polarization of macrophages can promote the invasion and metastasis of tumor cells. OVOL2 is an evolutionarily conserved transcription regulator, but its effect in macrophages has not been described previously. The aim of this study was to investigate the effects of OVOL2 on macrophage polarity and the role of these effects in the tumor metastasis. We found that overexpression of OVOL2 in macrophages significantly inhibited M2 polarization and thus inhibits breast cancer metastasis. We propose a novel mechanism in which OVOL2 inhibits M2 polarization of macrophages and thus reduces their ability to induce invasion and metastasis of breast cancer. By shedding new light on the regulation of metastasis in cancers, our study provides a new strategy for the targeted therapy of cancer.

Efferocytosis Modulates Arginase-1 and Tyrosine Kinase Mer Expression in GM-CSF-Differentiated Human Macrophages

We studied the expression of arginase-1 (Arg1) and tyrosine kinase Mer (MerTK) in GMCSF-differentiated human macrophage populations М0, М1(IFNγ), М2а(IL-4), and М2(low serum) generated under conditions of growth/serum factor deficiency. The maximum relative content of Arg1+ and MerTK+ cells was found in М2 macrophage populations: М2а(IL-4) and М2(low serum). As the uptake of apoptotic cells is the key mechanism of M2 polarization during M2(low serum) generation, we performed a special series of experiments and showed that incubation with allogeneic apoptotic neutrophils significantly increased the percentages of CD206+ macrophages co-expressing Arg1 and MerTK.

Clear cell renal cell carcinoma ontogeny and mechanisms of lethality

The molecular features that define clear cell renal cell carcinoma (ccRCC) initiation and progression are being increasingly defined. The TRACERx Renal studies and others that have described the interaction between tumour genomics and remodelling of the tumour microenvironment provide important new insights into the molecular drivers underlying ccRCC ontogeny and progression. Our understanding of common genomic and chromosomal copy number abnormalities in ccRCC, including chromosome 3p loss, provides a mechanistic framework with which to organize these abnormalities into those that drive tumour initiation events, those that drive tumour progression and those that confer lethality. Truncal mutations in ccRCC, including those in VHL, SET2, PBRM1 and BAP1, may engender genomic instability and promote defects in DNA repair pathways. The molecular features that arise from these defects enable categorization of ccRCC into clinically and therapeutically relevant subtypes. Consideration of the interaction of these subtypes with the tumour microenvironment reveals that specific mutations seem to modulate immune cell populations in ccRCC tumours. These findings present opportunities for disease prevention, early detection, prognostication and treatment.

A-loop interactions in Mer tyrosine kinase give rise to inhibitors with two-step mechanism and long residence time of binding

The activation loop (A-loop) plays a key role in regulating the catalytic activity of protein kinases. Phosphorylation in this region enhances the phosphoryl transfer rate of the kinase domain and increases its affinity for ATP. Furthermore, the A-loop possesses autoinhibitory functions in some kinases, where it collapses onto the protein surface and blocks substrate binding when unphosphorylated. Due to its flexible nature, the A-loop is usually disordered and untraceable in kinase domain crystal structures. The resulting lack of structural information is regrettable as it impedes the design of drug A-loop contacts, which have proven favourable in multiple cases. Here, we characterize the binding with A-loop engagement between type 1.5 kinase inhibitor ‘example 172’ (EX172) and Mer tyrosine kinase (MerTK). With the help of crystal structures and binding kinetics, we portray how the recruitment of the A-loop elicits a two-step binding mechanism which results in a drug-target complex characterized by high affinity and long residence time. In addition, the type 1.5 compound possesses excellent kinome selectivity and a remarkable preference for the phosphorylated over the dephosphorylated form of MerTK. We discuss these unique characteristics in the context of known type 1 and type 2 inhibitors and highlight opportunities for future kinase inhibitor design.

Prognostic significance and targeting tumor-associated macrophages in cancer: new insights and future perspectives

Macrophages are phagocytic sentinel cells of the immune system that are central to both innate and adaptive immune responses and serve as the first line of defense against pathogenic insults to tissues. In the tumor microenvironment, tumor-derived factors induce monocyte polarization towards a pro-tumor phenotype. The pro-tumor macrophages regulate key steps in tumorigenicity including tumor growth, angiogenesis, immune suppression, and metastasis. Macrophage infiltration in solid tumors correlates with poor prognosis and resistance to chemotherapy in most cancers. Here in this review, we will shed light on tumor-associated macrophages (TAMs) in regulating tumorigenicity and TAMs as a prognostic biomarker. Also, we will review the recent advances in targeting TAMs to increase the prognosis of cancer patients.

The potential role of nontyphoidal salmonellosis in gastric cancer: a nationwide matched cohort study

BACKGROUND

The research is to explore the association between nontyphoidal salmonellosis (NTS) and subsequent gastric cancer.

METHODS

We conducted a retrospective study by analyzing hospitalization dataset from the National Health Insurance Research Database in Taiwan. Patients aged 20 years and older with NTS (n = 9 097) admitted between January 1, 2000, and December 31, 2012, were enrolled and followed up until December 31, 2013. The primary outcome was the incidence of gastric cancer. Cox proportional hazards regression was used to estimate the risk of malignancy, accounting for the competing risk of death. In addition, we conducted a sensitivity analysis by propensity score matching and exclusion of malignancy within 1 year observation to minimize measurable confounding and protopathic bias. Negative controls were applied to examine the presence of possible unmeasured confounders in the study.

RESULTS

The study included 18 194 patients (9097 in each NTS and non-NTS group). The median follow-up time was 7 years. The incidence density rate of gastric cancer was 0.72 per 1000 person-years for the NTS group and 0.40 per 1000 person-years for the non-NTS group. The NTS group had a modestly higher risk of gastric cancer (aHR, 2.02; 95% CI 1.18-3.45) than the non-NTS group. The sensitivity analyses revealed consistent results.

CONCLUSIONS

Patients with NTS are associated with increased risk of subsequent gastric cancer compared with non-NTS patients. Future research is needed to examine whether NTS is parallel, reactive or causative to gastric cancer.

Combination of a T cell activating therapy and anti-phosphatidylserine enhances anti-tumour immune responses in a HPV16 E7-expressing C3 tumour model

DPX is a novel delivery platform that generates targeted CD8 + T cells and drives antigen-specific cytotoxic T cells into tumours. Cancer cells upregulate phosphatidylserine (PS) on the cell surface as a mechanism to induce an immunosuppressive microenvironment. Development of anti-PS targeting antibodies have highlighted the ability of a PS-blockade to enhance tumour control by T cells by releasing immunosuppression. Here, C57BL/6 mice were implanted with HPV16 E7 target-expressing C3 tumours and subjected to low dose intermittent cyclophosphamide (CPA) in combination with DPX-R9F treatment targeting an E7 antigen with and without anti-PS and/or anti-PD-1 targeting antibodies. Immune responses were assessed via IFN-γ ELISPOT assay and the tumour microenvironment was further analyzed using RT-qPCR. We show that the combination of DPX-R9F and PS-targeting antibodies with and without anti-PD-1 demonstrated increased efficacy compared to untreated controls. All treatments containing DPX-R9F led to T cell activation as assessed by IFN-γ ELISPOT. Furthermore, DPX-R9F/anti-PS treatment significantly elevated cytotoxic T cells, macrophages and dendritic cells based on RT-qPCR analysis. Overall, our data indicates that anti-tumour responses are driven through a variety of immune cells within this model and highlights the need to investigate combination therapies which increase tumour immune infiltration, such as anti-phosphotidylserine.

TAM kinase inhibition and immune checkpoint blockade- a winning combination in cancer treatment?

Introduction: Immune checkpoint inhibitors (ICI) have shown great promise in a wide spectrum of malignancies. However, responses are not always durable, and this mode of treatment is only effective in a subset of patients. As such, there exists an unmet need for novel approaches to bolster ICI efficacy.Areas covered: We review the role of the Tyro3, Axl, and Mer (TAM) receptor tyrosine kinases in promoting tumor-induced immune suppression and discuss the benefits that may be derived from combining ICI with TAM kinase-targeted tyrosine kinase inhibitors. We searched the MEDLINE Public Library of Medicine (PubMed) and EMBASE databases and referred to ClinicalTrials.gov for relevant ongoing studies.Expert opinion: Targeting of TAM kinases may improve the efficacy of immune checkpoint blockade. However, it remains to be determined whether this effect will be better achieved by the selective targeting of each TAM receptor, depending on the context, or by multi-receptor TAM inhibitors. Triple inhibition of all TAM receptors is more likely to be associated with an increased risk for adverse events. Clinical trial designs should use high-resolution clinical endpoints and proper control arms to determine the synergistic effects of combining TAM inhibition with immune checkpoint blockade.

Immuno-oncology: are TAM receptors in glioblastoma friends or foes?

Tyro3, Axl, and Mertk (TAM) receptors are a subfamily of receptor tyrosine kinases. TAM receptors have been implicated in mediating efferocytosis, regulation of immune cells, secretion of inflammatory factors, and epithelial-to-mesenchymal transition in the tumor microenvironment, thereby serving as a critical player in tumor development and progression. The pro-carcinogenic role of TAM receptors has been widely confirmed, overexpression of TAM receptors is tied to tumor cells growth, metastasis, invasion and treatment resistance. Nonetheless, it is surprising to detect that inhibiting TAM signaling is not all beneficial in the tumor immune microenvironment. The absence of TAM receptors also affects anti-tumor immunity under certain conditions by modulating different immune cells, as the functional diversification of TAM signaling is closely related to tumor immunotherapy. Glioblastoma is the most prevalent and lethal primary brain tumor in adults. Although research regarding the crosstalk between TAM receptors and glioblastoma remains scarce, it appears likely that TAM receptors possess potential anti-tumor effects rather than portraying a total cancer-driving role in the context of glioblastoma. Accordingly, we doubt whether TAM receptors play a double-sided role in glioblastoma, and propose the Janus-faced TAM Hypothesis as a conceptual framework for comprehending the precise underlying mechanisms of TAMs. In this study, we aim to cast a spotlight on the potential multidirectional effects of TAM receptors in glioblastoma and provide a better understanding for TAM receptor-related targeted intervention.

Immunotherapy and Immunotherapy Combinations in Metastatic Castration-Resistant Prostate Cancer

Although most prostate cancers are localized, and the majority are curable, recurrences occur in approximately 35% of men. Among patients with prostate-specific antigen (PSA) recurrence and PSA doubling time (PSADT) less than 15 months after radical prostatectomy, prostate cancer accounted for approximately 90% of the deaths by 15 years after recurrence. An immunosuppressive tumor microenvironment (TME) and impaired cellular immunity are likely largely responsible for the limited utility of checkpoint inhibitors (CPIs) in advanced prostate cancer compared with other tumor types. Thus, for immunologically "cold" malignancies such as prostate cancer, clinical trial development has pivoted towards novel approaches to enhance immune responses. Numerous clinical trials are currently evaluating combination immunomodulatory strategies incorporating vaccine-based therapies, checkpoint inhibitors, and chimeric antigen receptor (CAR) T cells. Other trials evaluate the efficacy and safety of these immunomodulatory agents' combinations with standard approaches such as androgen deprivation therapy (ADT), taxane-based chemotherapy, radiotherapy, and targeted therapies such as tyrosine kinase inhibitors (TKI) and poly ADP ribose polymerase (PARP) inhibitors. Here, we will review promising immunotherapies in development and ongoing trials for metastatic castration-resistant prostate cancer (mCRPC). These novel trials will build on past experiences and promise to usher a new era to treat patients with mCRPC.

Opposite trends of GAS6 and GAS6-AS expressions in breast cancer tissues

Growth arrest-specific gene 6 (GAS6) is a growth factor-like cytokine whose function is related with vitamin K. This protein interacts with receptor tyrosine kinase proteins such as Tyro3, Axl, and TAM Receptor family, therefore affecting the tumorigenic processes via different mechanisms. GAS6-antisense 1 (GAS6-AS1) is a long non-coding RNAs (lncRNAs) that is transcribed from a genomic regions nearby GAS6. This lncRNA is also implicated in the pathobiology of cancer. We intended to judge the role of GAS6 and GAS6-AS1 in the pathogenesis of breast cancer through appraisal of their expression levels in breast cancer tissues and their paired neighboring non-cancerous samples. Expression of GAS6 was up-regulated in breast cancer tissues compared with neighboring tissues (Ratio of Mean Expressions = 2.18, P value = 4.98E-02). On the other hand, expression of GAS6-AS1 was down-regulated in breast tumor tissues compared with controls (Ratio of Mean Expressions = 0.37, P value = 4.26E-03). There were substantial correlations between expression levels GAS6 and GAS6-AS1 in non-cancerous tissues (r = 0.74, P value = 1.47e-13) and cancer tissues (r = 0.85, P value = 2.28e-20). Expression of GAS6-AS was associated with progesterone receptor status (P value = 1.36E-02). However, expressions of this gene and the sense transcript were not linked with any other clinical or demographic variable. Taken together, GAS6 and GAS6-AS1 might partake in the development of breast cancer.