Dynamics of Axl Receptor Shedding in Hepatocellular Carcinoma and Its Implication for Theranostics

Nano-revolution in hepatocellular carcinoma: A multidisciplinary odyssey - Are we there yet?

In this editorial we comment on the review by Zhou et al reviewing the landscape of nanomedicine in the treatment of hepatocellular carcinoma (HCC). We focus on the immense potential of nanotechnology, particularly ligand-receptor mediated nanotherapy, in revolutionizing the treatment landscape of HCC. Despite advancements in multidisciplinary treatment, HCC remains a significant global health challenge. Ligand-mediated nanotherapy offers the opportunity for precise drug delivery to tumor sites, targeting specific receptors overexpressed in HCC cells, thereby enhancing efficacy and minimizing side effects. Overcoming drug resistance and aggressive tumor biology is facilitated by nanomedicine, bypassing traditional hurdles encountered in chemotherapy. Examples include targeting glypican-3, asialoglycoprotein, transferrin receptor or folic acid receptors, capitalizing on their over-expression in tumor cells. The ability for multi-receptor targeting through dual-ligand nanoparticle modification holds the prospect of further enhancement in specificity and efficacy of directed therapy. However, challenges including immune responses, reproducibility in nanoparticle synthesis, and production scalability remain. Future directions involve refining targeting strategies, improving drug release mechanisms, and streamlining production processes to enable personalized and multifunctional nanotherapies. Overall, the integration of nanotherapy in HCC treatment holds immense promise, but continued partnership and effort are needed in offering hope for more effective, precise, and accessible clinical care in the management of HCC.

Corylin Attenuates CCl4-Induced Liver Fibrosis in Mice by Regulating the GAS6/AXL Signaling Pathway in Hepatic Stellate Cells

Liver fibrosis is reversible when treated in its early stages and when liver inflammatory factors are inhibited. Limited studies have investigated the therapeutic effects of corylin, a flavonoid extracted from Psoralea corylifolia L. (Fabaceae), on liver fibrosis. Therefore, we evaluated the anti-inflammatory activity of corylin and investigated its efficacy and mechanism of action in ameliorating liver fibrosis. Corylin significantly inhibited inflammatory responses by inhibiting the activation of mitogen-activated protein kinase signaling pathways and the expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha in human THP-1 and mouse RAW264.7 macrophages. Furthermore, corylin inhibited the expression of growth arrest-specific gene 6 in human hepatic stellate cells (HSCs) and the activation of the downstream phosphoinositide 3-kinase/protein kinase B pathway. This inhibited the activation of HSCs and the expression of extracellular matrix proteins, including α-smooth muscle actin and type I collagen. Additionally, corylin induced caspase 9 and caspase 3 activation, which promoted apoptosis in HSCs. Moreover, in vivo experiments confirmed the regulatory effects of corylin on these proteins, and corylin alleviated the symptoms of carbon tetrachloride-induced liver fibrosis in mice. These findings revealed that corylin has anti-inflammatory activity and inhibits HSC activation; thus, it presents as a potential adjuvant in the treatment of liver fibrosis.

The role and mechanism of action of microRNA-122 in cancer: Focusing on the liver

microRNA-122 (miR-122) is a highly conserved microRNA that is predominantly expressed in the liver and plays a critical role in the regulation of liver metabolism. Recent studies have shown that miR-122 is involved in the pathogenesis of various types of cancer, particularly liver cancer. In this sense, The current findings highlighted the potential role of miR-122 in regulating many vital processes in cancer pathophysiology, including apoptosis, signaling pathway, cell metabolism, immune system response, migration, and invasion. These results imply that miR-122, which has been extensively studied for its biological functions and potential therapeutic applications, acts as a tumor suppressor or oncogene in cancer development. We first provide an overview and summary of the physiological function and mode of action of miR-122 in liver cancer. We will examine the various signaling pathways and molecular mechanisms through which miR-122 exerts its effects on cancer cells, including the regulation of oncogenic and tumor suppressor genes, the modulation of cell proliferation and apoptosis, and the regulation of metastasis. Most importantly, we will also discuss the potential diagnostic and therapeutic applications of miR-122 in cancer, including the development of miRNA-based biomarkers for cancer diagnosis and prognosis, and the potential use of miR-122 as a therapeutic target for cancer treatment.

Gas6 in chronic liver disease-a novel blood-based biomarker for liver fibrosis

The expression of the receptor tyrosine kinase Axl and its cleavage product soluble Axl (sAxl) is increased in liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). In this multicenter study, we evaluated the diagnostic value of Gas6, the high-affinity ligand of Axl, in patients with chronic liver disease. Levels of sAxl and Gas6, and their albumin (alb) ratios were analyzed in serum samples of patients with biopsy-proven liver fibrosis, end-stage liver disease, HCC, and healthy controls, and were compared to Fibrosis-4 (FIB-4), enhanced liver fibrosis (ELF™) test, Child-Pugh score (CPS), model of end-stage liver disease (MELD) score, hepatic venous pressure gradient, and α-fetoprotein, respectively. A total of 1111 patients (median age 57.8 y, 67.3% male) was analyzed. Gas6/alb showed high diagnostic accuracy for the detection of significant (≥F2: AUC 0.805) to advanced fibrosis (≥F3: AUC 0.818), and was superior to Fib-4 for the detection of cirrhosis (F4: AUC 0.897 vs. 0.878). In addition, Gas6/alb was highly predictive of liver disease severity (Odds ratios for CPS B/C, MELD ≥ 15, and clinically significant portal hypertension (CSPH) were 16.534, 10.258, and 12.115), and was associated with transplant-free survival (Hazard ratio 1.031). Although Gas6 and Gas6/alb showed high diagnostic accuracy for the detection of HCC in comparison to chronic liver disease patients without cirrhosis (AUC 0.852, 0.868), they failed to discriminate between HCC in cirrhosis versus cirrhosis only. In conclusion, Gas6/alb shows a high accuracy to detect significant to advanced fibrosis and cirrhosis, and predicts severity of liver disease including CSPH.

Molecular Targets and Signaling Pathways of microRNA-122 in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading global causes of cancer mortality. MicroRNAs (miRNAs) are small interfering RNAs that alleviate the levels of protein expression by suppressing translation, inducing mRNA cleavage, and promoting mRNA degradation. miR-122 is the most abundant miRNA in the liver and is responsible for several liver-specific functions, including metabolism, cellular growth and differentiation, and hepatitis virus replication. Recent studies have shown that aberrant regulation of miR-122 is a key factor contributing to the development of HCC. In this review, the signaling pathways and the molecular targets of miR-122 involved in the progression of HCC have been summarized, and the importance of miR-122 in therapy has been discussed.

Dissecting the Role of AXL in Cancer Immune Escape and Resistance to Immune Checkpoint Inhibition

The development and implementation of Immune Checkpoint Inhibitors (ICI) in clinical oncology have significantly improved the survival of a subset of cancer patients with metastatic disease previously considered uniformly lethal. However, the low response rates and the low number of patients with durable clinical responses remain major concerns and underscore the limited understanding of mechanisms regulating anti-tumor immunity and tumor immune resistance. There is an urgent unmet need for novel approaches to enhance the efficacy of ICI in the clinic, and for predictive tools that can accurately predict ICI responders based on the composition of their tumor microenvironment. The receptor tyrosine kinase (RTK) AXL has been associated with poor prognosis in numerous malignancies and the emergence of therapy resistance. AXL is a member of the TYRO3-AXL-MERTK (TAM) kinase family. Upon binding to its ligand GAS6, AXL regulates cell signaling cascades and cellular communication between various components of the tumor microenvironment, including cancer cells, endothelial cells, and immune cells. Converging evidence points to AXL as an attractive molecular target to overcome therapy resistance and immunosuppression, supported by the potential of AXL inhibitors to improve ICI efficacy. Here, we review the current literature on the prominent role of AXL in regulating cancer progression, with particular attention to its effects on anti-tumor immune response and resistance to ICI. We discuss future directions with the aim to understand better the complex role of AXL and TAM receptors in cancer and the potential value of this knowledge and targeted inhibition for the benefit of cancer patients.

Bioluminescent RAPPID Sensors for the Single-Step Detection of Soluble Axl and Multiplex Analysis of Cell Surface Cancer Biomarkers

Early diagnosis of cancer is essential for the efficacy of treatment. Our group recently developed RAPPID, a bioluminescent immunoassay platform capable of measuring a wide panel of biomarkers directly in solution. Here, we developed and systematically screened different RAPPID sensors for sensitive detection of the soluble fraction of Axl (sAxl), a cell surface receptor that is overexpressed in several types of cancer. The best-performing RAPPID sensor, with a limit of detection of 8 pM and a >9-fold maximal change in emission ratio, was applied to measure Axl in three different contexts: clinically relevant sAxl levels (∼0.5 and ∼1 nM) in diluted blood plasma, proteolytically cleaved Axl in the cell culture medium of A431 and HeLa cancer cells, and Axl on the membrane of A431 cells. We further extended the sensor toolbox by developing dual-color RAPPID for simultaneous detection of Axl and EGFR on A431 and HeLa cells, as well as an AND-gate RAPPID that measures the concurrent presence of these two cell surface receptors on the same cell. These new RAPPID sensors provide attractive alternatives for more laborious protein detection and quantification methods such as FACS and immunostainings, due to their simple practical implantation and low intrinsic background signal.

Diagnosis and staging of HCV associated fibrosis, cirrhosis and hepatocellular carcinoma with target identification for miR-650, 552-3p, 676-3p, 512-5p and 147b

BACKGROUND: Chronic HCV infection progresses to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The latter represents the third most common cause for cancer mortality. Currently, there is no reliable non-invasive biomarker for diagnosis of HCV mediated disorders. OBJECTIVE: Profiling expression signature for circulatory miRNAs in the plasma of 167 Egyptian patients (40 healthy, 48 HCV fibrotic, 39 HCV cirrhotic and 40 HCV-HCC cases). METHODS: QRTPCR was used to quantify expression signature for circulatory miRNAs. RESULTS: MiR-676 and miR-650 were powerful in discriminating cirrhotic and late fibrosis from HCC. MiR-650 could distinguish mild (f0-f1) and advanced (f2-f3) fibrosis from HCC cases. MiR-650 and miR-147b could distinguish early fibrosis from healthy controls meanwhile miR-676 and miR-147b could effectively distinguish between mild chronic and (f1-f3) cases from healthy individuals. All studied miRNAs, except miR-512, can differentiate between (f0-f3) cases and healthy controls. Multivariate logistic regression revealed three potential miRNA panels for effective differentiation of HCC, cirrhotic and chronic liver cases. MiR-676-3p and miR-512-5p were significantly correlated in (f1-f3) fibrosis meanwhile miR-676 and miR-512 could differentiate between cirrhosis and (f0-f3) cases. Both miR-650 and miR-512-5p were positively correlated in the cirrhotic group and in (f0-f4) group. Putative targets for investigated miRNAs were also determined. CONCLUSIONS: Investigated miRNAs could assist in staging and diagnosis of HCV associated disorders.

Regulation of the Receptor Tyrosine Kinase AXL in Response to Therapy and Its Role in Therapy Resistance in Glioblastoma

The receptor tyrosine kinase AXL (RTK-AXL) is implicated in therapy resistance and tumor progression in glioblastoma multiforme (GBM). Here, we investigated therapy-induced receptor modifications and how endogenous RTK-AXL expression and RTK-AXL inhibition contribute to therapy resistance in GBM. GBM cell lines U118MG and SF126 were exposed to temozolomide (TMZ) and radiation (RTX). Receptor modifications in response to therapy were investigated on protein and mRNA levels. TMZ-resistant and RTK-AXL overexpressing cell lines were exposed to increasing doses of TMZ and RTX, with and without RTK-AXL tyrosine kinase inhibitor (TKI). Colorimetric microtiter (MTT) assay and colony formation assay (CFA) were used to assess cell viability. Results showed that the RTK-AXL shedding product, C-terminal AXL (CT-AXL), rises in response to repeated TMZ doses and under hypoxia, acts as a surrogate marker for radio-resistance. Endogenous RTX-AXL overexpression leads to therapy resistance, whereas combination therapy of TZM and RTX with TKI R428 significantly increases therapeutic effects. This data proves the role of RTK-AXL in acquired and intrinsic therapy resistance. By demonstrating that therapy resistance may be overcome by combining AXL TKI with standard treatments, we have provided a rationale for future study designs investigating AXL TKIs in GBM.

TAM Receptors in the Pathophysiology of Liver Disease

TAM receptors (Tyro3, Axl and MerTK) are a family of tyrosine kinase receptors that are expressed in a variety of cell populations, including liver parenchymal and non-parenchymal cells. These receptors are vital for immune homeostasis, as they regulate the innate immune response by suppressing inflammation via toll-like receptor inhibition and by promoting tissue resolution through efferocytosis. However, there is increasing evidence indicating that aberrant TAM receptor signaling may play a role in pathophysiological processes in the context of liver disease. This review will explore the roles of TAM receptors and their ligands in liver homeostasis as well as a variety of disease settings, including acute liver injury, steatosis, fibrosis, cirrhosis-associated immune dysfunction and hepatocellular carcinoma. A better understanding of our current knowledge of TAM receptors in liver disease may identify new opportunities for disease monitoring as well as novel therapeutic targets. Nonetheless, this review also aims to highlight areas where further research on TAM receptor biology in liver disease is required.

Soluble TAM receptors sAXL and sTyro3 predict structural and functional protection in Alzheimer's disease

There is an urgent need to improve the understanding of neuroinflammation in Alzheimer's disease (AD). We analyzed cerebrospinal fluid inflammatory biomarker correlations to brain structural volume and longitudinal cognitive outcomes in the DELCODE study and in a validation cohort of the F.ACE Alzheimer Center Barcelona. We investigated whether respective biomarker changes are evident before onset of cognitive impairment. YKL-40; sTREM2; sAXL; sTyro3; MIF; complement factors C1q, C4, and H; ferritin; and ApoE protein were elevated in pre-dementia subjects with pathological levels of tau or other neurodegeneration markers, demonstrating tight interactions between inflammation and accumulating neurodegeneration even before onset of symptoms. Intriguingly, higher levels of ApoE and soluble TAM receptors sAXL and sTyro3 were related to larger brain structure and stable cognitive outcome at follow-up. Our findings indicate a protective mechanism relevant for intervention strategies aiming to regulate neuroinflammation in subjects with no or subjective symptoms but underlying AD pathology profile.

Exploring the Gamut of Receptor Tyrosine Kinases for Their Promise in the Management of Non-Alcoholic Fatty Liver Disease

Recently, non-alcoholic fatty liver disease (NAFLD) has emerged as a predominant health concern affecting approximately a quarter of the world’s population. NAFLD is a spectrum of liver ailments arising from nascent lipid accumulation and leading to inflammation, fibrosis or even carcinogenesis. Despite its prevalence and severity, no targeted pharmacological intervention is approved to date. Thus, it is imperative to identify suitable drug targets critical to the development and progression of NAFLD. In this quest, a ray of hope is nestled within a group of proteins, receptor tyrosine kinases (RTKs), as targets to contain or even reverse NAFLD. RTKs control numerous vital biological processes and their selective expression and activity in specific diseases have rendered them useful as drug targets. In this review, we discuss the recent advancements in characterizing the role of RTKs in NAFLD progression and qualify their suitability as pharmacological targets. Available data suggests inhibition of Epidermal Growth Factor Receptor, AXL, Fibroblast Growth Factor Receptor 4 and Vascular Endothelial Growth Factor Receptor, and activation of cellular mesenchymal-epithelial transition factor and Fibroblast Growth Factor Receptor 1 could pave the way for novel NAFLD therapeutics. Thus, it is important to characterize these RTKs for target validation and proof-of-concept through clinical trials.

Intrinsic and Extrinsic Control of Hepatocellular Carcinoma by TAM Receptors

Simple Summary

Tyro3, Axl, and MerTK are receptor tyrosine kinases of the TAM family, which are activated by their ligands Gas6 and Protein S. TAM receptors have large physiological implications, including the removal of dead cells, activation of immune cells, and prevention of bleeding. In the last decade, TAM receptors have been suggested to play a relevant role in liver fibrogenesis and the development of hepatocellular carcinoma. The understanding of TAM receptor functions in tumor cells and their cellular microenvironment is of utmost importance to advances in novel therapeutic strategies that conquer chronic liver disease including hepatocellular carcinoma.

Abstract

Hepatocellular carcinoma (HCC) is the major subtype of liver cancer, showing high mortality of patients due to limited therapeutic options at advanced stages of disease. The receptor tyrosine kinases Tyro3, Axl and MerTK—belonging to the TAM family—exert a large impact on various aspects of cancer biology. Binding of the ligands Gas6 or Protein S activates TAM receptors causing homophilic dimerization and heterophilic interactions with other receptors to modulate effector functions. In this context, TAM receptors are major regulators of anti-inflammatory responses and vessel integrity, including platelet aggregation as well as resistance to chemotherapy. In this review, we discuss the relevance of TAM receptors in the intrinsic control of HCC progression by modulating epithelial cell plasticity and by promoting metastatic traits of neoplastic hepatocytes. Depending on different etiologies of HCC, we further describe the overt role of TAM receptors in the extrinsic control of HCC progression by focusing on immune cell infiltration and fibrogenesis. Additionally, we assess TAM receptor functions in the chemoresistance against clinically used tyrosine kinase inhibitors and immune checkpoint blockade in HCC progression. We finally address the question of whether inhibition of TAM receptors can be envisaged for novel therapeutic strategies in HCC.

Possible Association of Elevated Plasma Levels of Growth Arrest-Specific Protein 6 and the Soluble Form of Tyrosine Kinase Receptor Axl with Low Hepatitis C Viral Load in Patients with Type 2 Diabetes Mellitus

This study aimed to investigate the plasma levels of Gas6 and soluble Axl (sAxl) in patients with chronic hepatitis C virus (HCV) infection with and without type 2 diabetes mellitus (T2DM). The study involved four groups; 50 patients with chronic HCV, 50 patients with T2DM, 50 patients with chronic HCV and T2DM, and 31 age- and sex-matched healthy controls. T2DM was diagnosed according to American Diabetes Association criteria, HCV antibodies were detected by enzyme-linked immunosorbent assays (ELISA) and confirmed by real-time-polymerase chain reaction. Plasma Gas6 and sAxl levels were assayed in all groups by ELISA. Significant low levels of GAS 6 in HCV/T2DM group versus HCV group were detected (7.92 ± 5.18 vs. 16.09 ± 7.36, respectively, p = 0.000), but higher than T2DM and control groups (p ≥ 0.05), although nonsignificant. HCV load was higher in the HCV group than the HCV/T2DM group (1,888,300 ± 5,595,070 vs. 1,417,900 ± 4,066,460 copies/mL, respectively, p = 0.632). Among HCV group, significant positive correlations were detected between Gas6 and sAxl levels with HCV viral load (r = 0.48, p = 0.000 and r = 0.43, p = 0.002, respectively), while among HCV/T2DM group, significant negative correlations were detected (r = -0.29, p = 0.04 and r = -0.34, p = 0.014, respectively). Significant negative correlations were detected between Gas6/sAxl levels and glycated hemoglobin (r = -0.36, p = 0.01 and r = -0.4, p = 0.003, respectively) in T2DM despite the positive correlations detected in HCV/T2DM (r = 0.27, p = 0.053 and r = 0.55, p = 0.000, respectively). In conclusion, Gas6/Axl system in combined HCV/T2DM diseases may affect the pathogenesis and can alter the biomarkers and complications of both diseases in a manner that differs from a solitary disease.

AXL as a Target in Breast Cancer Therapy

AXL is a receptor tyrosine kinase (RTK) that has been implicated in diverse tumor-promoting processes such as proliferation, migration, invasion, survival, and apoptosis. AXL therefore plays a role in cancer progression, and AXL has been implicated in a wide variety of malignancies from solid tumors to hematopoietic cancers where it is often associated with poor prognosis. In cancer, AXL has been shown to promote epithelial to mesenchymal transition (EMT), metastasis formation, drug resistance, and a role for AXL in modulation of the tumor microenvironment and immune response has been identified. In light of these activities multiple AXL inhibitors have been developed, and several of these have entered clinical trials in the U.S. In breast cancer, high levels of AXL expression have been observed. The role of AXL in cancer with a focus on therapeutic implications for breast cancer is discussed.

Gas6/TAM System: A Key Modulator of the Interplay between Inflammation and Fibrosis

Fibrosis is the result of an overly abundant deposition of extracellular matrix (ECM) due to the fact of repetitive tissue injuries and/or dysregulation of the repair process. Fibrogenesis is a pathogenetic phenomenon which is involved in different chronic human diseases, accounting for a high burden of morbidity and mortality. Despite being triggered by different causative factors, fibrogenesis follows common pathways, the knowledge of which is, however, still unsatisfactory. This represents a significant limit for the development of effective antifibrotic drugs. In the present paper, we aimed to review the current evidence regarding the potential role played in fibrogenesis by growth arrest-specific 6 (Gas6) and its receptors Tyro3 protein tyrosine kinase (Tyro3), Axl receptor tyrosine kinase (Axl), and Mer tyrosine kinase protooncogene (MerTK) (TAM). Moreover, we aimed to review data about the pathogenetic role of this system in the development of different human diseases characterized by fibrosis. Finally, we aimed to explore the potential implications of these findings in diagnosis and treatment.

Gas6/TAM Signaling Components as Novel Biomarkers of Liver Fibrosis

Liver fibrosis consists in the accumulation of extracellular matrix components mainly derived from activated hepatic stellate cells. This is commonly the result of chronic liver injury repair and represents an important health concern. As liver biopsy is burdened with many drawbacks, not surprisingly there is great interest to find new reliable noninvasive methods. Among the many are new potential fibrosis biomarkers under study, some of the most promising represented by the growth arrest-specific gene 6 (Gas6) serum protein and its family of tyrosine kinase receptors, namely, Tyro3, Axl, and MERTK (TAM). Gas6/TAM system (mainly, Axl and MERTK) has in fact recently emerged as an important player in the progression of liver fibrosis. This review is aimed at giving an overall perspective of the roles played by these molecules in major chronic liver diseases. The most promising findings up to date acknowledge that both Gas6 and its receptor serum levels (such as sAxl and, probably, sMERTK) have been shown to potentially allow for easy and accurate measurement of hepatic fibrosis progression, also providing indicative parameters of hepatic dysfunction. Although most of the current scientific evidence is still preliminary and there are no in vivo validation studies on large patient series, it still looks very promising to imagine a possible future prognostic role for these biomarkers in the multidimensional assessment of a liver patient. One may also speculate on a potential role for this system targeting (e.g., with small molecule inhibitors against Axl) as a therapeutic strategy for liver fibrosis management, always bearing in mind that any such therapeutic approach might face toxicity.

High Risk of Hepatocellular Carcinoma Development in Fibrotic Liver: Role of the Hippo-YAP/TAZ Signaling Pathway

Liver cancer is the fourth leading cause of cancer-related death globally, accounting for approximately 800,000 deaths annually. Hepatocellular carcinoma (HCC) is the most common type of liver cancer, making up about 80% of cases. Liver fibrosis and its end-stage disease, cirrhosis, are major risk factors for HCC. A fibrotic liver typically shows persistent hepatocyte death and compensatory regeneration, chronic inflammation, and an increase in reactive oxygen species, which collaboratively create a tumor-promoting microenvironment via inducing genetic alterations and chromosomal instability, and activating various oncogenic molecular signaling pathways. In this article, we review recent advances in fields of liver fibrosis and carcinogenesis, and consider several molecular signaling pathways that promote hepato-carcinogenesis under the microenvironment of liver fibrosis. In particular, we pay attention to emerging roles of the Hippo-YAP/TAZ signaling pathway in stromal activation, hepatic fibrosis, and liver cancer.