Met receptor tyrosine kinase: enhanced signaling through adapter proteins

Spatiotemporal regulation of the hepatocyte growth factor receptor MET activity by sorting nexins 1/2 in HCT116 colorectal cancer cells

Cumulative research findings support the idea that endocytic trafficking is crucial in regulating receptor signaling and associated diseases. Specifically, strong evidence points to the involvement of sorting nexins (SNXs), particularly SNX1 and SNX2, in the signaling and trafficking of the receptor tyrosine kinase (RTK) MET in colorectal cancer (CRC). Activation of hepatocyte growth factor (HGF) receptor MET is a key driver of CRC progression. In the present study, we utilized human HCT116 CRC cells with SNX1 and SNX2 genes knocked out to demonstrate that their absence leads to a delay in MET entering early endosomes. This delay results in increased phosphorylation of both MET and AKT upon HGF stimulation, while ERK1/2 (extracellular signal-regulated kinases 1 and 2) phosphorylation remains unaffected. Despite these changes, HGF-induced cell proliferation, scattering, and migration remain similar between the parental and the SNX1/2 knockout cells. However, in the absence of SNX1 and SNX2, these cells exhibit increased resistance to TRAIL-induced apoptosis. This research underscores the intricate relationship between intracellular trafficking, receptor signaling, and cellular responses and demonstrates for the first time that the modulation of MET trafficking by SNX1 and SNX2 is critical for receptor signaling that may exacerbate the disease.

Expression of genes potentially involved in loss of response in patients with chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a hematological malignancy characterized by the presence of the BCR::ABL1 fusion gene, which leads to uncontrolled cell growth and survival. Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of CML, but a significant proportion of patients develop resistance or lose response to these drugs. Understanding the molecular mechanisms underlying treatment response and resistance is crucial for improving patient outcomes. This study aimed to analyze the expression patterns of genes involved in treatment response and resistance in CML patients receiving TKI therapy. The expression levels of MET, FOXO3, p15, p16, HCK, and FYN genes were examined in CML patients and compared to healthy donors. Gene expression levels were compared between optimal responders (OR) and resistant patients (R) vs. healthy donors (HD). The MET and FOXO3 OR group showed significant differences compared with the HD, (p < 0.0001) and (p = 0.0003), respectively. p15 expression showed significant differences between OR and HD groups (p = 0.0078), while no significant differences were found in p16 expression between the HD groups. FYN showed a statistically significant difference between R vs. HD (p = 0.0157). The results of HCK expression analysis revealed significant differences between OR and HD (p = 0.0041) and between R and HD (p = 0.0026). When we analyzed OR patients with undetectable BCR::ABL1 transcripts, a greater expression of HCK was observed in the R group. These findings suggest that monitoring the expression levels of MET and FOXO3 genes could be valuable in predicting treatment response and relapse in CML patients. Our study provides important insights into the potential use of gene expression analysis as a tool for predicting treatment response and guiding treatment decisions in CML patients. This knowledge may ultimately contribute to the development of personalized treatment strategies to improve patient outcomes in CML.

Thrombin Priming Promotes the Neuroprotective Effects of Human Wharton's Jelly-Derived Mesenchymal Stem Cells Via the HGF/AKT/STAT3 Signaling Pathway

Mesenchymal stem cells (MSCs) directly differentiate into neurons and endothelial cells after transplantation, and their secretome has considerable potential for treating brain injuries. Previous studies have suggested that the effects of MSCs priming with exposure to hypoxia, cytokines, growth factors, or chemical agents could optimize the paracrine potency and therapeutic potential of MSCs. Studies have suggested that thrombin-primed Wharton's Jelly-derived mesenchymal stem cells (Th.WJ-MSCs) significantly enhance the neuroprotective beneficial effects of naive MSCs in brain injury such as hypoxic-ischemic brain injury (HIE) and intraventricular hemorrhage (IVH). This study aimed to characterize WJ-MSCs in terms of stem cell markers, differentiation, cell proliferation, and paracrine factors by comparing naive and Th.WJ-MSCs. We demonstrated that compared with naive MSCs, Th.MSCs significantly enhanced the neuroprotective effects in vitro. Moreover, we identified differentially expressed proteins in the conditioned media of naive and Th.WJ-MSCs by liquid chromatography-tandem mass spectrometry analysis. Secretome analysis of the conditioned medium of WJ-MSCs revealed that such neuroprotective effects were mediated by paracrine effects with secretomes of Th.WJ-MSCs, and hepatocyte growth factor was identified as a key paracrine mediator. These results can be applied further in the preclinical and clinical development of effective and safe cell therapeutics for brain injuries such as HIE and IVH.

Targeting MET: Discovery of Small Molecule Inhibitors as Non-Small Cell Lung Cancer Therapy

MET has been considered as a promising drug target for the treatment of MET-dependent diseases, particularly non-small cell lung cancer (NSCLC). Small molecule MET inhibitors with mainly three types of binding modes (Ia/Ib, II, and III) have been developed. In this Review, we provide an overview of the structural features, activation mechanism, and dysregulation pathway of MET and summarize progress on the development and discovery strategies utilized for MET inhibitors as well as mechanisms of acquired resistance to current approved inhibitors. The insights will accelerate discovery of new generation MET inhibitors to overcome clinical acquired resistance.

Impact of the flame retardant 2,2'4,4'-tetrabromodiphenyl ether (PBDE-47) in THP-1 macrophage-like cell function via small extracellular vesicles

2,2'4,4'-tetrabromodiphenyl ether (PBDE-47) is one of the most widespread environmental brominated flame-retardant congeners which has also been detected in animal and human tissues. Several studies have reported the effects of PBDEs on different health issues, including neurobehavioral and developmental disorders, reproductive health, and alterations of thyroid function. Much less is known about its immunotoxicity. The aim of our study was to investigate the effects that treatment of THP-1 macrophage-like cells with PBDE-47 could have on the content of small extracellular vesicles' (sEVs) microRNA (miRNA) cargo and their downstream effects on bystander macrophages. To achieve this, we purified sEVs from PBDE-47 treated M(LPS) THP-1 macrophage-like cells (sEVs^PBDE+LPS) by means of ultra-centrifugation and characterized their miRNA cargo by microarray analysis detecting the modulation of 18 miRNAs. Furthermore, resting THP-1 derived M(0) macrophage-like cells were cultured with sEVs^PBDE+LPS, showing that the treatment reshaped the miRNA profiles of 12 intracellular miRNAs. This dataset was studied in silico, identifying the biological pathways affected by these target genes. This analysis identified 12 pathways all involved in the maturation and polarization of macrophages. Therefore, to evaluate whether sEVs^PBDE+LPS can have some immunomodulatory activity, naïve M(0) THP-1 macrophage-like cells cultured with purified sEVs^PBDE+LPS were studied for IL-6, TNF-α and TGF-β mRNAs expression and immune stained with the HLA-DR, CD80, CCR7, CD38 and CD209 antigens and analyzed by flow cytometry. This analysis showed that the PBDE-47 treatment does not induce the expression of specific M1 and M2 cytokine markers of differentiation and may have impaired the ability to make immunological synapses and present antigens, down-regulating the expression of HLA-DR and CD209 antigens. Overall, our study supports the model that perturbation of miRNA cargo by PBDE-47 treatment contributes to the rewiring of cellular regulatory pathways capable of inducing perturbation of differentiation markers on naïve resting M(0) THP-1 macrophage-like cells.

Hepatocyte Growth Factor Enhances Antineoplastic Effect of 5-Fluorouracil by Increasing UPP1 Expression in HepG2 Cells

Aberrant activation of hepatocyte growth factor (HGF) and its receptor c-Met axis promotes tumor growth. Therefore, many clinical trials have been conducted. A phase 3 trial investigating a monoclonal antibody targeting HGF in combination with fluoropyrimidine-based chemotherapy had to be terminated prematurely; however, the reason behind the failure remains poorly defined. In this study, we investigated the influence of HGF on the antineoplastic effects of 5-fluorouracil (5-FU), a fluoropyrimidine, in HepG2 cells. HGF suppressed the proliferative activity of cells concomitantly treated with 5-FU more robustly as compared to that of cells treated with 5-FU alone, and markedly increased the expression of uridine phosphorylase 1 (UPP1). Intracellular concentration of 5-fluorouridine, an initial anabolite of 5-FU catalyzed by UPP1, was increased by HGF. Interestingly, erlotinib enhanced HGF-induced increase in UPP1 mRNA; in contrast, gefitinib suppressed it. Furthermore, erlotinib suppressed HGF-increased phosphorylation of the epidermal growth factor receptor at the Tyr1173 site involved in downregulation of extracellular signal-regulated kinase (Erk) activation, and enhanced the HGF-increased phosphorylation of Erk. Collectively, these findings suggest that inhibition of the HGF/c-Met axis diminishes the effects of fluoropyrimidine through downregulation of UPP1 expression. Therefore, extreme caution must be exercised in terms of patient safety while offering chemotherapy comprising fluoropyrimidine concomitantly with inhibitors of the HGF/c-Met axis.

Opportunities and challenges of targeting c-Met in the treatment of digestive tumors

At present, a large number of studies have demonstrated that c-Met generally exerts a crucial function of promoting tumor cells proliferation and differentiation in digestive system tumors. c-Met also mediates tumor progression and drug resistance by signaling interactions with other oncogenic molecules and then activating downstream pathways. Therefore, c-Met is a promising target for the treatment of digestive system tumors. Many anti-tumor therapies targeting c-Met (tyrosine kinase inhibitors, monoclonal antibodies, and adoptive immunotherapy) have been developed in treating digestive system tumors. Some drugs have been successfully applied to clinic, but most of them are defective due to their efficacy and complications. In order to promote the clinical application of targeting c-Met drugs in digestive system tumors, it is necessary to further explore the mechanism of c-Met action in digestive system tumors and optimize the anti-tumor treatment of targeting c-Met drugs. Through reading a large number of literatures, the author systematically reviewed the biological functions and molecular mechanisms of c-Met associated with tumor and summarized the current status of targeting c-Met in the treatment of digestive system tumors so as to provide new ideas for the treatment of digestive system tumors.

3D Ultrasound-Guided Photoacoustic Imaging to Monitor the Effects of Suboptimal Tyrosine Kinase Inhibitor Therapy in Pancreatic Tumors

Pancreatic cancer is a disease with an incredibly poor survival rate. As only about 20% of patients are eligible for surgical resection, neoadjuvant treatments that can relieve symptoms and shrink tumors for surgical resection become critical. Many forms of treatments rely on increased vulnerability of cancerous cells, but tumors or regions within the tumors that may be hypoxic could be drug resistant. Particularly for neoadjuvant therapies such as the tyrosine kinase inhibitors utilized to shrink tumors, it is critical to monitor changes in vascular function and hypoxia to predict treatment efficacy. Current clinical imaging modalities used to obtain structural and functional information regarding hypoxia or oxygen saturation (StO2) do not provide sufficient depth penetration or require the use of exogenous contrast agents. Recently, ultrasound-guided photoacoustic imaging (US-PAI) has garnered significant popularity, as it can noninvasively provide multiparametric information on tumor vasculature and function without the need for contrast agents. Here, we built upon existing literature on US-PAI and demonstrate the importance of changes in StO2 values to predict treatment response, particularly tumor growth rate, when the outcomes are suboptimal. Specifically, we image xenograft mouse models of pancreatic adenocarcinoma treated with suboptimal doses of a tyrosine kinase inhibitor cabozantinib. We utilize the US-PAI data to develop a multivariate regression model that demonstrates that a therapy-induced reduction in tumor growth rate can be predicted with 100% positive predictive power and a moderate (58.33%) negative predictive power when a combination of pretreatment tumor volume and changes in StO2 values pretreatment and immediately posttreatment was employed. Overall, our study indicates that US-PAI has the potential to provide label-free surrogate imaging biomarkers that can predict tumor growth rate in suboptimal therapy.

Design, Synthesis, and Biological Evaluation of [1,2,4]triazolo[4,3-a] Pyrazine Derivatives as Novel Dual c-Met/VEGFR-2 Inhibitors

In this study, we designed and synthesized a series of novel [1,2,4]triazolo [4,3-a]pyrazine derivatives, and evaluated them for their inhibitory activities toward c-Met/VEGFR-2 kinases and antiproliferative activities against tested three cell lines in vitro. Most of the compounds showed satisfactory activity compared with lead compound foretinib. Among them, the most promising compound 17l exhibited excellent antiproliferative activities against A549, MCF-7, and Hela cancer cell lines with IC₅₀ values of 0.98 ± 0.08, 1.05 ± 0.17, and 1.28 ± 0.25 µM, respectively, as well as excellent kinase inhibitory activities (c-Met IC₅₀ = 26.00 nM and VEGFR-2 IC₅₀ = 2.6 µM). Moreover, compound 17l inhibited the growth of A549 cells in G0/G1 phase in a dose-dependent manner, and induced the late apoptosis of A549 cells. Its intervention on intracellular c-Met signaling of A549 was verified by the result of Western blot. Fluorescence quantitative PCR showed that compound 17l inhibited the growth of A549 cells by inhibiting the expression of c-Met and VEGFR-2, and its hemolytic toxicity was low. Molecular docking and molecular dynamics simulation indicated that compound 17l could bind to c-Met and VEGFR-2 protein, which was similar to that of foretinib.

Growth factor dependence of the proliferation and survival of cultured lacrimal gland epithelial cells isolated from late-embryonic mice

Epidermal growth factor (EGF) and hepatocyte growth factor (HGF) regulate the growth and morphogenesis of various exocrine glands with branched morphologies. Their roles in lacrimal gland (LG) development remain unknown, but fibroblast growth factor (FGF) 10 is crucial for early LG organogenesis. To clarify the roles of EGF, HGF, and FGF10 in LG development, LG epithelial cells were isolated from late-embryonic and neonatal mice; cultured; and treated with EGF, HGF, or FGF10 and their respective receptor tyrosine kinase (RTK) inhibitors AG1478, PHA665752, or SU5402. EGF and HGF increased the number of viable cells by enhancing DNA synthesis, FGF10 and SU5402 showed no such effect, and RTK inhibitors exhibited the opposite effect. EGF and HGF receptors were immunostained in cultured late-embryonic LG epithelial cells and terminal LG acini from late embryos and adult mice. HGF was detected in neonatal LG epithelial cell culture supernatants by western blotting. In the absence of EGF and HGF RTK inhibitors, growth factor addition increased the number of viable cells and suppressed cell death. However, when one RTK was inhibited and a growth factor targeting an intact RTK was added, the number of dead cells increased as the number of viable cells increased. No cells survived when both RTKs were inhibited. In explant cultures of LGs from embryos, AG1478 or PHA665752 decreased the number of Ki67-positive proliferating epithelial cells in terminal acini. Thus, EGF and HGF may function in a cooperative autocrine manner, supporting cell proliferation and survival during LG development in late-embryonic and neonatal mice.

Receptor tyrosine kinase MET ligand-interaction classified via machine learning from single-particle tracking data

Internalin B–mediated activation of the membrane-bound receptor tyrosine kinase MET is accompanied by a change in receptor mobility. Conversely, it should be possible to infer from receptor mobility whether a cell has been treated with internalin B. Here, we propose a method based on hidden Markov modeling and explainable artificial intelligence that machine-learns the key differences in MET mobility between internalin B–treated and –untreated cells from single-particle tracking data. Our method assigns receptor mobility to three diffusion modes (immobile, slow, and fast). It discriminates between internalin B–treated and –untreated cells with a balanced accuracy of >99% and identifies three parameters that are most affected by internalin B treatment: a decrease in the mobility of slow molecules (1) and a depopulation of the fast mode (2) caused by an increased transition of fast molecules to the slow mode (3). Our approach is based entirely on free software and is readily applicable to the analysis of other membrane receptors.

Roles of MET in human cancer

The MET proto-oncogene was first identified in osteosarcoma cells exposed to carcinogens. Although expressed in many normal cells, MET is overexpressed in many human cancers. MET is involved in the initiation and development of various human cancers and mediates proliferation, migration and invasion. Accordingly, MET has been successfully used as a biomarker for diagnosis and prognosis, survival, post-operative recurrence, risk assessment and pathologic grading, as well as a therapeutic target. In addition, recent work indicates that inhibition of MET expression and function has potential clinical benefit. This review summarizes the role, mechanism, and clinical significance of MET in the formation and development of human cancer.

Magnetofection In Vivo by Nanomagnetic Carriers Systemically Administered into the Bloodstream

Nanoparticle-based technologies are rapidly expanding into many areas of biomedicine and molecular science. The unique ability of magnetic nanoparticles to respond to the magnetic field makes them especially attractive for a number of in vivo applications including magnetofection. The magnetofection principle consists of the accumulation and retention of magnetic nanoparticles carrying nucleic acids in the area of magnetic field application. The method is highly promising as a clinically efficient tool for gene delivery in vivo. However, the data on in vivo magnetofection are often only descriptive or poorly studied, insufficiently systematized, and sometimes even contradictory. Therefore, the aim of the review was to systematize and analyze the data that influence the in vivo magnetofection processes after the systemic injection of magnetic nanostructures. The main emphasis is placed on the structure and coating of the nanomagnetic vectors. The present problems and future trends of the method development are also considered.

3-phosphoinositide-dependent protein kinase 1 (PDK1) mediates crosstalk between Src and Akt pathways in MET receptor signaling

The high-affinity tyrosine kinase receptor MET plays a pivotal role in several facets of cell regulation. Although its mitogenic effect is well documented, some aspects of connection patterns between signaling pathways involved in cell cycle progression remain to be deciphered. We have used a tractable heterologous expression system, the Xenopus oocyte, to detect connections between distinct MET signaling cascades involved in G2/M progression. Our results reveal that Src acts as an adapter via its SH2 domain to recruit 3-phosphoinositide-dependent protein kinase 1 (PDK1) to the MET signaling complex leading to Akt phosphorylation. These data define an original crosstalk between Src and Akt signaling pathways that contributes to MET-induced entry into the M phase, and deserves further investigation in pathologies harboring deregulation of this receptor.

Evolution of MET and NRAS gene amplification as acquired resistance mechanisms in EGFR mutant NSCLC

EGFR mutant non-small cell lung cancer patients' disease demonstrates remarkable responses to EGFR-targeted therapy, but inevitably they succumb to acquired resistance, which can be complex and difficult to treat. Analyzing acquired resistance through broad molecular testing is crucial to understanding the resistance mechanisms and developing new treatment options. We performed diverse clinical testing on a patient with successive stages of acquired resistance, first to an EGFR inhibitor with MET gene amplification and then subsequently to a combination EGFR and MET targeted therapies. A patient-derived cell line obtained at the time of disease progression was used to identify NRAS gene amplification as an additional driver of drug resistance to combination EGFR/MET therapies. Analysis of downstream signaling revealed extracellular signal-related kinase activation that could only be eliminated by trametinib treatment, while Akt activation could be modulated by various combinations of MET, EGFR, and PI3K inhibitors. The combination of an EGFR inhibitor with a MEK inhibitor was identified as a possible treatment option to overcome drug resistance related to NRAS gene amplification.

Molecular insight into the affinity, specificity and cross-reactivity of systematic hepatocellular carcinoma RALT interaction profile with human receptor tyrosine kinases

The ErbB family of receptor tyrosine kinases (RTKs) contains four members: EGFR, ErbB2, ErbB3 and ErbB4; they are involved in the tumorigenesis of diverse cancers and can be inhibited natively by receptor-associated late transducer (RALT), a negative feedback regulator of ErbB signaling in human hepatocytes and hepatocellular carcinoma. Although the biological effects of RALT on EGFR kinase have been widely documented previously, the binding behavior of RALT to other ErbB/RTK kinases still remains largely unexplored. Here, the intermolecular interactions of RALT ErbB-binding region (EBR) as well as its functional sections and peptide segments with ErbBs and other human RTKs were systematically investigated at molecular and structural levels, from which we were able to identify those potential kinase targets of RALT protein, and to profile the affinity, specificity and cross-reactivity of RALT EBR domain and its sub-regions against various RTKs. It is revealed that RALT can target all the four ErbB kinases with high affinity for EGFR/ErbB2/ErbB4 and moderate affinity for ErbB3, but generally exhibits modest affinity to other RTKs, albeit few kinases such as LTK, EPHB6, MET and MUSK were also top-ranked as the unexpected targets of RALT. Peptide segments covering the key binding regions of RALT EBR domain were identified with computational alanine scanning, which were then optimized to obtain a number of designed peptide mutants with improved selectivity between different top-ranked RTKs.

Phosphorylation of slit diaphragm proteins NEPHRIN and NEPH1 upon binding of HGF promotes podocyte repair

Phosphorylation (activation) and dephosphorylation (deactivation) of the slit diaphragm proteins NEPHRIN and NEPH1 are critical for maintaining the kidney epithelial podocyte actin cytoskeleton and, therefore, proper glomerular filtration. However, the mechanisms underlying these events remain largely unknown. Here we show that NEPHRIN and NEPH1 are novel receptor proteins for hepatocyte growth factor (HGF) and can be phosphorylated independently of the mesenchymal epithelial transition receptor in a ligand-dependent fashion through engagement of their extracellular domains by HGF. Furthermore, we demonstrate SH2 domain–containing protein tyrosine phosphatase-2–dependent dephosphorylation of these proteins. To establish HGF as a ligand, purified baculovirus-expressed NEPHRIN and NEPH1 recombinant proteins were used in surface plasma resonance binding experiments. We report high-affinity interactions of NEPHRIN and NEPH1 with HGF, although NEPHRIN binding was 20-fold higher than that of NEPH1. In addition, using molecular modeling we constructed peptides that were used to map specific HGF-binding regions in the extracellular domains of NEPHRIN and NEPH1. Finally, using an in vitro model of cultured podocytes and an ex vivo model of Drosophila nephrocytes, as well as chemically induced injury models, we demonstrated that HGF-induced phosphorylation of NEPHRIN and NEPH1 is centrally involved in podocyte repair. Taken together, this is the first study demonstrating a receptor-based function for NEPHRIN and NEPH1. This has important biological and clinical implications for the repair of injured podocytes and the maintenance of podocyte integrity.

Molecular mechanism study of HGF/c-MET pathway activation and immune regulation for a tumor diagnosis model

Background

Hepatocyte growth factor (HGF) binds to the c-mesenchymal-epithelial transition (C-MET) receptor and activates downstream signaling pathways, playing an essential role in the development of various cancers. Given the role of this signaling pathway, the primary therapeutic direction focuses on identifying and designing HGF inhibitors, antagonists and other molecules to block the binding of HGF to C-MET, thereby limiting the abnormal state of other downstream genes.

Methods

This study focuses on the analysis of immune-related genes and corresponding immune functions that are significantly associated with the HGF/c-MET pathway using transcriptome data from 11 solid tumors.

Results

We systematically analyzed 11 different cancers, including expression correlation, immune infiltration, tumor diagnosis and survival prognosis from HGF/c-MET pathway and immune regulation, two biological mechanisms having received extensive attention in cancer analysis.

Conclusion

We found that the HGF/c-MET pathway affected the tumor microenvironment mainly by interfering with expression levels of other genes. Immune infiltration is another critical factor involved in changes to the tumor microenvironment. The downstream immune-related genes activated by the HGF/c-MET pathway regulate immune-related pathways, which in turn affect the degree of infiltration of immune cells. Immune infiltration is significantly associated with cancer development and prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02051-2.

MET alterations and their impact on the future of non-small cell lung cancer (NSCLC) targeted therapies

Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.

Cellular plasticity balances the metabolic and proliferation dynamics of a regenerating liver

The adult liver has an exceptional ability to regenerate, but how it maintains its specialized functions during regeneration is unclear. Here, we used partial hepatectomy (PHx) in tandem with single-cell transcriptomics to track cellular transitions and heterogeneities of ∼22,000 liver cells through the initiation, progression, and termination phases of mouse liver regeneration. Our results uncovered that, following PHx, a subset of hepatocytes transiently reactivates an early-postnatal-like gene expression program to proliferate, while a distinct population of metabolically hyperactive cells appears to compensate for any temporary deficits in liver function. Cumulative EdU labeling and immunostaining of metabolic, portal, and central vein-specific markers revealed that hepatocyte proliferation after PHx initiates in the midlobular region before proceeding toward the periportal and pericentral areas. We further demonstrate that portal and central vein proximal hepatocytes retain their metabolically active state to preserve essential liver functions while midlobular cells proliferate nearby. Through combined analysis of gene regulatory networks and cell-cell interaction maps, we found that regenerating hepatocytes redeploy key developmental regulons, which are guided by extensive ligand-receptor-mediated signaling events between hepatocytes and nonparenchymal cells. Altogether, our study offers a detailed blueprint of the intercellular crosstalk and cellular reprogramming that balances the metabolic and proliferative requirements of a regenerating liver.

Prognostic relevance of longitudinal HGF levels in serum of patients with ovarian cancer

The pleiotropic protein hepatocyte growth factor (HGF) is the only known ligand of the tyrosine kinase mesenchymal–epithelial transition (cMET) receptor. The HGF/cMET pathway mediates invasion and migration of ovarian cancer cells, and upregulation of HGF/cMET pathway components has been associated with poor prognosis. This study investigated the clinical relevance of circulating HGF in serum of patients with ovarian cancer. Serum HGF (sHGF) was determined by enzyme‐linked immunosorbent assay in a total of 471 serum samples from 82 healthy controls and 113 patients with ovarian cancer (88.5% with ≥ FIGO III). Patient samples were collected at primary diagnosis and at four follow‐up time points throughout treatment and at disease recurrence. Patients with ovarian cancer showed elevated median sHGF levels at primary diagnosis, and sHGF levels transiently increased after surgery and normalized in the course of chemotherapy, even dropping below initial baseline. Higher levels of sHGF were an independent predictor for shorter overall survival (OS) (a) at primary diagnosis (HR = 0.41, 95% CI: 0.22–0.78, P = 0.006), (b) at longitudinal follow‐up time points (after surgery and before/during/after chemotherapy), (c) along the patients’ individual dynamics (HR = 0.21, 95% CI: 0.07–0.63, P = 0.005), and (d) among a subgroup analysis of patients with BRCA1/2 wild‐type ovarian cancer. This is the first study proposing sHGF as an independent prognostic biomarker for ovarian cancer at primary diagnosis and in the course of platinum‐based chemotherapy, irrespective of the postoperative residual disease after surgical debulking. sHGF could be implemented into clinical diagnostics as a CA125 auxiliary tumor marker for individualized prognosis stratification and sHGF‐guided therapy monitoring.

Recent Advances in Monoclonal Antibody Therapy for Colorectal Cancers

Colorectal cancer (CRC) is one of the leading causes of cancer deaths worldwide. Recent advances in recombinant DNA technology have led to the development of numerous therapeutic antibodies as major sources of blockbuster drugs for CRC therapy. Simultaneously, increasing numbers of therapeutic targets in CRC have been identified. In this review, we first highlight the physiological and pathophysiological roles and signaling mechanisms of currently known and emerging therapeutic targets, including growth factors and their receptors as well as immune checkpoint proteins, in CRC. Additionally, we discuss the current status of monoclonal antibodies in clinical development and approved by US Food and Drug Administration for CRC therapy.

Tyrosine phosphorylation of the scaffold protein IQGAP1 in the MET pathway alters function

IQGAP1 is a key scaffold protein that regulates numerous cellular processes and signaling pathways. Analogous to many other cellular proteins, IQGAP1 undergoes post-translational modifications, including phosphorylation. Nevertheless, very little is known about the specific sites of phosphorylation or the effects on IQGAP1 function. Here, using several approaches, including MS, site-directed mutagenesis, siRNA-mediated gene silencing, and chemical inhibitors, we identified the specific tyrosine residues that are phosphorylated on IQGAP1 and evaluated the effect on function. Tyr-172, Tyr-654, Tyr-855, and Tyr-1510 were phosphorylated on IQGAP1 when phosphotyrosine phosphatase activity was inhibited in cells. IQGAP1 was phosphorylated exclusively on Tyr-1510 under conditions with enhanced MET or c-Src signaling, including in human lung cancer cell lines. This phosphorylation was significantly reduced by chemical inhibitors of MET or c-Src or by siRNA-mediated knockdown of MET. To investigate the biological sequelae of phosphorylation, we generated a nonphosphorylatable IQGAP1 construct by replacing Tyr-1510 with alanine. The ability of hepatocyte growth factor, the ligand for MET, to promote AKT activation and cell migration was significantly greater when IQGAP1-null cells were reconstituted with IQGAP1 Y1510A than when cells were reconstituted with WT IQGAP1. Collectively, our data suggest that phosphorylation of Tyr-1510 of IQGAP1 alters cell function. Because increased MET signaling is implicated in the development and progression of several types of carcinoma, IQGAP1 may be a potential therapeutic target in selected malignancies.

Genotype Driven Therapy for Non-Small Cell Lung Cancer: Resistance, Pan Inhibitors and Immunotherapy

Eighty-five percent of patients with lung cancer present with Non-small Cell Lung Cancer (NSCLC). Targeted therapy approaches are promising treatments for lung cancer. However, despite the development of targeted therapies using Tyrosine Kinase Inhibitors (TKI) as well as monoclonal antibodies, the five-year relative survival rate for lung cancer patients is still only 18%, and patients inevitably become resistant to therapy. Mutations in Kirsten Ras Sarcoma viral homolog (KRAS) and epidermal growth factor receptor (EGFR) are the two most common genetic events in lung adenocarcinoma; they account for 25% and 20% of cases, respectively. Anaplastic Lymphoma Kinase (ALK) is a transmembrane receptor tyrosine kinase, and ALK rearrangements are responsible for 3-7% of NSCLC, predominantly of the adenocarcinoma subtype, and occur in a mutually exclusive manner with KRAS and EGFR mutations. Among drug-resistant NSCLC patients, nearly half exhibit the T790M mutation in exon 20 of EGFR. This review focuses on some basic aspects of molecules involved in NSCLC, the development of resistance to treatments in NSCLC, and advances in lung cancer therapy in the past ten years. Some recent developments such as PD-1-PD-L1 checkpoint-based immunotherapy for NSCLC are also covered.

Targeting hepatocyte growth factor/c-mesenchymal-epithelial transition factor axis in hepatocellular carcinoma: Rationale and therapeutic strategies

Hepatocellular carcinoma (HCC) is a leading cause of cancer mortality worldwide. The outcome of current standard treatments, as well as targeted therapies in advanced stages, are still unsatisfactory. Attention has been drawn to novel strategies for better treatment efficacy. Hepatocyte growth factor/c-mesenchymal-epithelial transition factor (HGF/c-Met) axis has been known as an essential element in the regulation of liver diseases and as an oncogenic factor in HCC. In this review, we collected the evidence of HGF/c-Met as a tumor progression and prognostic marker, discussed the anti-c-Met therapy in vitro, summarized the outcome of c-Met inhibitors in clinical trials, and identified potential impetus for future anti-c-Met treatments. We also analyzed the inconsistency of HGF/c-Met from various publications and offered reasonable explanations based on the current understanding in this area. In conclusion, HGF/c-Met plays a crucial role in the progression and growth of HCC, and the strategies to inhibit this pathway may facilitate the development of new and effective treatments for HCC patients.

Hepatocyte growth factor and matrix metalloprotease 2 levels in synovial fluid of the knee joint are correlated with clinical outcome of meniscal repair

BACKGROUND

The reoperation rate after primary meniscal repair is about 20%. Thus far, it has remained unclear whether there are distinct individual preconditions that may be associated with a better or worse outcome of this procedure. We therefore analysed typical biochemical mediators in the synovial fluid (SF) of patients with meniscus tear before arthroscopic meniscal refixation and correlated their concentrations to the occurrence of re-rupture after meniscus repair.

METHODS

In this study, 48 patients with meniscus ruptures were included. SF samples were taken intraoperatively prior to arthroscopy. Multiplex enzyme-linked immunosorbent assay (ELISA)-based methods were used to measure hepatocyte growth factor (HGF), interleukin-18 (IL-18), matrix metalloproteinases (MMP) MMP-1, MMP-2, MMP-9 and MMP-13 in the SF. At follow-up, the patients were classified into two groups: surgical success and surgical failure.

RESULTS

Ten out of 48 patients (20.8%) had to undergo revision surgery after meniscal repair (surgical failure). The median HGF in the surgical failure group was 2.4-times higher than in the surgical success group (P = .006), and the median MMP-2 was 1.8 times higher (P = .017). Concentration levels of the other tested proteins were not correlated with the success or failure of the meniscus surgery. There was weak evidence that both markers are indicators of an unsatisfactory healing process for meniscal refixation.

CONCLUSION

These results suggest that HGF and MMP-2 could serve as molecular markers to estimate the chances of healing success of meniscus repair and possibly to individualise therapy in meniscal surgery.

MET receptor in oncology: From biomarker to therapeutic target

First discovered in the 1984, the MET receptor tyrosine kinase (RTK) and its ligand hepatocyte growth factor or HGF (also known as scatter factor or SF) are implicated as key players in tumor cell migration, proliferation, and invasion in a variety of cancers. This pathway also plays a key role during embryogenesis in the development of muscular and nervous structures. High expression of the MET receptor has been shown to correlate with poor prognosis and resistance to therapy. MET exon 14 splicing variants, initially identified by us in lung cancer, is actionable through various tyrosine kinase inhibitors (TKIs). For this reason, this pathway is of interest as a therapeutic target. In this chapter we will be discussing the history of MET, the genetics of this RTK, and give some background on the receptor biology. Furthermore, we will discuss directed therapeutics, mechanisms of resistance, and the future of MET as a therapeutic target.

Targeting the HGF/MET Axis in Cancer Therapy: Challenges in Resistance and Opportunities for Improvement

Among hundreds of thousands of signal receptors contributing to oncogenic activation, tumorigenesis, and metastasis, the hepatocyte growth factor (HGF) receptor - also called tyrosine kinase MET - is a promising target in cancer therapy as its axis is involved in several different cancer types. It is also associated with poor outcomes and is involved in the development of therapeutic resistance. Several HGF/MET-neutralizing antibodies and MET kinase-specific small molecule inhibitors have been developed, resulting in some context-dependent progress in multiple cancer treatments. Nevertheless, the concomitant therapeutic resistance largely inhibits the translation of such targeted drug candidates into clinical application. Until now, numerous studies have been performed to understand the molecular, cellular, and upstream mechanisms that regulate HGF/MET-targeted drug resistance, further explore novel strategies to reduce the occurrence of resistance, and improve therapeutic efficacy after resistance. Intriguingly, emerging evidence has revealed that, in addition to its conventional function as an oncogene, the HGF/MET axis stands at the crossroads of tumor autophagy, immunity, and microenvironment. Based on current progress, this review summarizes the current challenges and simultaneously proposes future opportunities for HGF/MET targeting for therapeutic cancer interventions.

Tumour angiogenesis and c-Met pathway activation - implications in breast cancer

Breast cancer is a heterogeneous disease with wide range of clinical behaviour. Tumour angiogenesis and metastasis have been considered as prognostic markers of the breast carcinoma, and c-Met, a transmembrane receptor tyrosine kinase has been implicated in both these processes of tumour progression. This study was conducted to elucidate c-Met and downstream signalling pathways in breast cancer and correlate with angiogenesis as assessed by microvessel density (MVD) and other prognostic parameters including lymph node metastases. Microvessel density (MVD) was assessed by endothelial cell (CD34) marker in breast cancers. c-Met was evaluated by immunohistochemistry for protein expression and by copy number assay for amplification at gene level. PCR array for gene expression related to c-Met, RAS-MAPK, PI3K-AKT and angiogenesis pathway was performed by real-time PCR. c-Met protein, copy number and mRNA expression did not differ significantly with the lymph node status or MVD. However, Her-2 overexpressing group showed c-Met protein overexpression and amplification. c-Met protein overexpression was also noted in the Luminal B subtype though no amplification was noted. Thus, the c-Met immunohistochemistry score and the c-MET copy numbers did not correlate with each other. c-Met downstream pathway genes (RAS-MAPK, PI3K-AKT and angiogenesis pathway) showed significant upregulation in Luminal B molecular subtype, lymph node-positive cases and cases with high MVD. The downstream signalling pathways (angiogenesis, RAS-MAPK and PI3K-AKT) were associated high MVD, lymph node metastases, and Her-2 and Luminal B subtype. Since inhibitors of these pathways are commercially available, these can be of therapeutic significance.

A Phase I Study of Safety, Pharmacokinetics, and Pharmacodynamics of Concurrent Everolimus and Buparlisib Treatment in Advanced Solid Tumors

PURPOSE

Concurrent inhibition of mTOR and PI3K led to improved efficacy in preclinical models and provided the rationale for this phase I study of everolimus and buparlisib (BKM120) in patients with advanced solid tumor.

PATIENTS AND METHODS

We used the Bayesian Escalation with Overdose Control design to test escalating doses of everolimus (5 or 10 mg) and buparlisib (20, 40, 60, 80, and 100 mg) in eligible patients. Pharmacokinetic assessment was conducted using blood samples collected on cycle 1, days 8 and 15. Pharmacodynamic impact on mTOR/PI3K pathway modulation evaluated in paired skin biopsies collected at baseline and end of cycle 1.

RESULTS

We enrolled 43 patients, median age of 63 (range, 39-78) years; 25 (58.1%) females, 35 (81.4%) Caucasians, and 8 (18.6%) Blacks. The most frequent toxicities were hyperglycemia, diarrhea, nausea, fatigue, and aspartate aminotransferase elevation. Dose-limiting toxicities observed in 7 patients were fatigue (3), hyperglycemia (2), mucositis (1), acute kidney injury (1), and urinary tract infection (1). The recommended phase II dose (RP2D) for the combination was established as everolimus (5 mg) and buparlisib (60 mg). The best response in 27 evaluable patients was progressive disease and stable disease in 3 (11%) and 24 (89%), respectively. The median progression-free survival and overall survival were 2.7 (1.8-4.2) and 9 (6.4-13.2) months. Steady-state pharmacokinetic analysis showed dose-normalized maximum concentrations and AUC values for everolimus and buparlisib in combination to be comparable with single-agent pharmacokinetic.

CONCLUSIONS

The combination of everolimus and buparlisib is safe and well-tolerated at the RP2D of 5 and 60 mg on a continuous daily schedule.

Crosstalk Mechanisms Between HGF/c-Met Axis and ncRNAs in Malignancy

Several lines of evidence have confirmed the magnitude of crosstalk between HGF/c-Met axis (hepatocyte growth factor and its high-affinity receptor c-mesenchymal-epithelial transition factor) and non-coding RNAs (ncRNAs) in tumorigenesis. Through activating canonical or non-canonical signaling pathways, the HGF/c-Met axis mediates a range of oncogenic processes such as cell proliferation, invasion, apoptosis, and angiogenesis and is increasingly becoming a promising target for cancer therapy. Meanwhile, ncRNAs are a cluster of functional RNA molecules that perform their biological roles at the RNA level and are essential regulators of gene expression. The expression of ncRNAs is cell/tissue/tumor-specific, which makes them excellent candidates for cancer research. Many studies have revealed that ncRNAs play a crucial role in cancer initiation and progression by regulating different downstream genes or signal transduction pathways, including HGF/c-Met axis. In this review, we discuss the regulatory association between ncRNAs and the HGF/c-Met axis by providing a comprehensive understanding of their potential mechanisms and roles in cancer development. These findings could reveal their possible clinical applications as biomarkers for therapeutic interventions.

Control of cortical synapse development and plasticity by MET receptor tyrosine kinase, a genetic risk factor for autism

The key developmental milestone events of the human brain, such as neurogenesis, synapse formation, maturation, and plasticity, are determined by a myriad of molecular signaling events, including those mediated by a number of receptor tyrosine kinases (RTKs) and their cognate ligands. Aberrant or mistimed brain development and plasticity can lead to maladaptive changes, such as dysregulated synaptic connectivity and breakdown of circuit functions necessary for cognition and adaptive behaviors, which are hypothesized pathophysiologies of many neurodevelopmental and neuropsychiatric disorders. Here we review recent literature that supports autism spectrum disorder as a likely result of aberrant synapse development due to mistimed maturation and plasticity. We focus on MET RTK, a prominent genetic risk factor for autism, and discuss how a pleiotropic molecular signaling system engaged by MET exemplifies a genetic program that controls cortical circuit development and plasticity by modulating the anatomical and functional connectivity of cortical circuits, thus conferring genetic risk for neurodevelopmental disorders.

Prevalence and Clinicopathological Significance of MET Overexpression and Gene Amplification in Patients with Gallbladder Carcinoma

PURPOSE

Mesenchymal epithelial transition (MET) is a proto-oncogene that encodes a heterodimeric transmembrane receptor tyrosine kinase for the hepatocyte growth factor. Aberrant MET signaling has been described in several solid tumors-especially non-small cell lung cancer- and is associated with tumor progression and adverse prognosis. As MET is a potential therapeutic target, information regarding its prevalence and clinicopathological relevance is crucial.

MATERIALS AND METHODS

We investigated MET expression and gene amplification in 113 gallbladder cancers using tissue microarray. Immunohistochemistry was used to evaluate MET overexpression, and silver/fluorescence in situ hybridization (ISH) was used to assess gene copy number.

RESULTS

MET overexpression was found in 37 cases of gallbladder carcinoma (39.8%), and gene amplification was present in 17 cases (18.3%). MET protein expression did not correlate with MET amplification. MET amplification was significantly associated with aggressive clinicopathological features, including high histological grade, advanced pT category, lymph node metastasis, and advanced American Joint Committee on Cancer stage. There was no significant correlation between any clinicopathological factors and MET overexpression. No difference in survival was found with respect to MET overexpression and amplification status.

CONCLUSION

Our data suggested that MET might be a potential therapeutic target for targeted therapy in gallbladder cancer, because MET amplification was found in a subset of tumors associated with adverse prognostic factors. Detection of MET amplification by ISH might be a useful predictive biomarker test for anti-MET therapy.

Tyrosine Kinases in Helicobacter pylori Infections and Gastric Cancer

Helicobacter pylori (H. pylori) has been identified as a leading cause of gastric cancer, which is one of the most frequent and malignant types of tumor. It is characterized by its rapid progression, distant metastases, and resistance to conventional chemotherapy. A number of receptor tyrosine kinases and non-receptor tyrosine kinases have been implicated in H. pylori-mediated pathogenesis and tumorigenesis. In this review, recent findings of deregulated EGFR, c-Met, JAK, FAK, Src, and c-Abl and their functions in H. pylori pathogenesis are summarized.

Mechanistically detailed systems biology modeling of the HGF/Met pathway in hepatocellular carcinoma

Hepatocyte growth factor (HGF) signaling through its receptor Met has been implicated in hepatocellular carcinoma tumorigenesis and progression. Met interaction with integrins is shown to modulate the downstream signaling to Akt and ERK (extracellular-regulated kinase). In this study, we developed a mechanistically detailed systems biology model of HGF/Met signaling pathway that incorporated specific interactions with integrins to investigate the efficacy of integrin-binding peptide, AXT050, as monotherapy and in combination with other therapeutics targeting this pathway. Here we report that the modeled dynamics of the response to AXT050 revealed that receptor trafficking is sufficient to explain the effect of Met-integrin interactions on HGF signaling. Furthermore, the model predicted patient-specific synergy and antagonism of efficacy and potency for combination of AXT050 with sorafenib, cabozantinib, and rilotumumab. Overall, the model provides a valuable framework for studying the efficacy of drugs targeting receptor tyrosine kinase interaction with integrins, and identification of synergistic drug combinations for the patients.

Understanding the Mechanisms of Resistance in EGFR-Positive NSCLC: From Tissue to Liquid Biopsy to Guide Treatment Strategy

Liquid biopsy has emerged as an alternative source of nucleic acids for the management of Epidermal Growth Factor Receptor (EGFR)-mutant non-Small Cell Lung Cancer (NSCLC). The use of circulating cell-free DNA (cfDNA) has been recently introduced in clinical practice, resulting in the improvement of the identification of druggable EGFR mutations for the diagnosis and monitoring of response to targeted therapy. EGFR-dependent (T790M and C797S mutations) and independent (Mesenchymal Epithelial Transition [MET] gene amplification, Kirsten Rat Sarcoma [KRAS], Phosphatidyl-Inositol 4,5-bisphosphate 3-Kinase Catalytic subunit Alpha isoform [PI3KCA], and RAF murine sarcoma viral oncogene homolog B1 [BRAF] gene mutations) mechanisms of resistance to EGFR tyrosine kinase inhibitors (TKIs) have been evaluated in plasma samples from NSCLC patients using highly sensitive methods (i.e., digital droplet PCR, Next Generation Sequencing), allowing for the switch to other therapies. Therefore, liquid biopsy is a non-invasive method able to detect the molecular dynamic changes that occur under the pressure of treatment, and to capture tumor heterogeneity more efficiently than is allowed by tissue biopsy. This review addresses how liquid biopsy may be used to guide the choice of treatment strategy in EGFR-mutant NSCLC.

Development of c‑MET‑specific chimeric antigen receptor‑engineered natural killer cells with cytotoxic effects on human liver cancer HepG2 cells

In recent years, cellular immunotherapy has served an important role in the combined treatment of hepatocellular carcinoma. The possibility of specific cell therapies for the treatment of solid tumours has been further explored following the success of chimeric antigen receptor (CAR)-T cell therapy in the treatment of haematological tumours. The present study aimed to evaluate the specificity and efficiency of c-MET-targeted CAR-NK cell immunotherapy on human liver cancer in vitro. A CAR structure that targeted and recognised a c-MET antigen was constructed. c-MET-CAR was transferred into primary NK cells using lentiviral infection. c-MET-positive HepG2 cells were used as an in vitro study model. The cytotoxicity assay results revealed that c-MET-CAR-NK cells exhibited more specific cytotoxicity for HepG2 cells with high c-MET expression compared with the lung cancer cell line H1299, which has low levels of c-MET expression. The results of the present study demonstrated that c-MET may be a specific and effective target for human liver cancer cell CAR-NK immunotherapy. Based on these results, CAR-NK cell-based immunotherapy may provide a potential biotherapeutic approach for liver cancer treatment in the future.

Synthesis of novel 6,7-dimethoxy-4-anilinoquinolines as potent c-Met inhibitors

HGF/c-Met signalling pathway plays an important role in the development of cancers. A series of 6,7-dimethoxy-4-anilinoquinolines possessing benzimidazole moiety were synthesised and identified as potent inhibitors of the tyrosine kinase c-Met. Their in vitro biological activities against three cancer cell lines (A549, MCF-7, and MKN-45) were also evaluated. Most of these compounds exhibited moderate to remarkable potency. Among them, compound 12n showed the most potent inhibitory activity against c-Met with IC₅₀ value of 0.030 ± 0.008 µM and it also showed excellent anticancer activity against the tested cancer cell lines at low micromolar concentration. Molecular docking verified the results and revealed the possible binding mode of the most promising compound 12n into the ATP-binding site of c-Met kinase.

HGF/c-MET Signaling in Melanocytes and Melanoma

Hepatocyte growth factor (HGF)/ mesenchymal-epithelial transition factor (c-MET) signaling is involved in complex cellular programs that are important for embryonic development and tissue regeneration, but its activity is also utilized by cancer cells during tumor progression. HGF and c-MET usually mediate heterotypic cell–cell interactions, such as epithelial–mesenchymal, including tumor–stroma interactions. In the skin, dermal fibroblasts are the main source of HGF. The presence of c-MET on keratinocytes is crucial for wound healing in the skin. HGF is not released by normal melanocytes, but as melanocytes express c-MET, they are receptive to HGF, which protects them from apoptosis and stimulates their proliferation and motility. Dissimilar to melanocytes, melanoma cells not only express c-MET, but also release HGF, thus activating c-MET in an autocrine manner. Stimulation of the HGF/c-MET pathways contributes to several processes that are crucial for melanoma development, such as proliferation, survival, motility, and invasiveness, including distant metastatic niche formation. HGF might be a factor in the innate and acquired resistance of melanoma to oncoprotein-targeted drugs. It is not entirely clear whether elevated serum HGF level is associated with low progression-free survival and overall survival after treatment with targeted therapies. This review focuses on the role of HGF/c-MET signaling in melanoma with some introductory information on its function in skin and melanocytes.

The Role of PI3K in Met Driven Cancer: A Recap

The Receptor Tyrosine Kinase (RTK) Met, overexpressed or mutated in cancer, plays a major role in cancer progression and represents an attractive target for cancer therapy. However RTK inhibitors can lead to drug resistance, explaining the necessity to develop therapies that target downstream signaling. Phosphatidylinositide 3-kinase (PI3K) is one of the most deregulated pathways in cancer and implicated in various types of cancer. PI3K signaling is also a major signaling pathway downstream of RTK, including Met. PI3K major effectors include Akt and "mechanistic Target of Rapamycin" (mTOR), which each play key roles in numerous and various cell functions. Advancements made due to the development of molecular and pharmaceutical tools now allow us to delve into the roles of each independently. In this review, we summarize the current understanding we possess of the activation and role of PI3K/Akt/mTOR, downstream of Met, in cancer.

HGF/c-MET: A Promising Therapeutic Target in the Digestive System Cancers

The HGF/c-MET pathway is active in the development of digestive system cancers, indicating that inhibition of HGF/c-MET signaling may have therapeutic potential. Various HGF/c-MET signaling inhibitors, mainly c-MET inhibitors, have been tested in clinical trials. The observed efficacy and adverse events of some c-MET inhibitors were not very suitable for treating digestive system cancers. The development of new HGF/c-MET inhibitors in preclinical studies may bring promising treatments and synergistic combination (traditional anticancer drugs and c-MET inhibitors) strategies provided anacceptable safety and tolerability. Insights into miRNA biology and miRNA therapeutics have made miRNAs attractive tools to inhibit HGF/c-MET signaling. Recent reports show that several microRNAs participate in inhibiting HGF/c-MET signaling networks through antagonizing c-MET or HGF in digestive system cancers, and the miRNAs-HGF/c-MET axis plays crucial and novel roles for cancer treatment. In the current review, we will discuss recent findings about inhibitors of HGF/c-MET signaling in treating digestive system cancers, and how miRNAs regulate digestive system cancers via mediating HGF/c-MET pathway.

Boswellia frereana suppresses HGF-mediated breast cancer cell invasion and migration through inhibition of c-Met signalling

BACKGROUND

Hepatocyte growth factor (HGF) plays a pivotal role in breast cancer cell motility, invasion and angiogenesis. These pro-metastatic events are triggered through HGF coupling and activation of the c-Met receptor. Reports have demonstrated that HGF/c-Met signalling plays an important part in breast cancer progression and that their expression is linked to poor patient outcome. In the present study, we investigated the anti-metastatic potential of an extract from traditional Somalian frankincense, Boswellia frereana, on human breast cancer cells. In addition, we also examined the effect of this Boswellia frereana extract (BFE) upon HGF-mediated stimulation of the c-Met receptor.

METHODS

Two triple negative human breast cancer cell lines, BT549 and MDA-MB-231, were utilised in the study to examine the effect of BFE on tumour cell proliferation, migration, matrix-adhesion, angiogenesis and invasion. Cell migration was investigated using a Cell IQ time-lapsed motion analysis system; while tumour cell-matrix adhesion, angiogenesis and invasion were assessed through Matrigel-based in vitro assays. Breast cancer cell growth and spheroid formation was examined through proliferation assay and 3D non-scaffold cell culture techniques. Western Blotting was employed to determine the phosphorylation status of the c-Met receptor tyrosine kinase following BFE treatment and subsequent HGF stimulation.

RESULTS

Following HGF treatment, the breast cancer cells displayed a significant increase in migration, matrix adhesion, vessel/tubule formation, invasion and c-Met activation. HGF did not appear to have any bearing on the proliferation rate or spheroid formation of these breast cancer cells. The addition of the BFE extract quenched the HGF-enhanced migratory, angiogenic and invasive potential of these cells. Further study revealed that BFE inhibited c-Met receptor tyrosine kinase phosphorylation within these breast cancer cells.

CONCLUSIONS

Our findings reveal that BFE was able to significantly suppress the influence of HGF in breast cancer cell motility and invasion in vitro, through the ability of BFE to reduce HGF/c-Met signalling events. Therefore, these results indicate that BFE could play a novel role in the treatment of breast cancer.

Prognostic impact of high c-Met expression in ovarian cancer: a meta-analysis

High c-Met expression has been observed in epithelial ovarian cancer (EOC). However, its clinicopathological impacts remain controversial. We conducted this meta-analysis to evaluate the pathologic and prognostic significance of c-Met overexpression in patients with EOC. A systematic computerized search of the electronic databases PubMed, PMC, EMBASE, and Google scholar (up to April 2018) was carried out. From seven studies, 568 patients with EOC were included in the meta-analysis. Although there was no statistical significance, EOCs with c-Met overexpression tended to show higher FIGO stage (III-IV) (odds ratio = 2.18, 95% confidence interval: 0.86-5.53, p = 0.10) and higher rate of lymph node metastasis (odds ratio = 3.05, 95% confidence interval: 0.85-10.98, p = 0.09), compared with tumors with low c-Met expression. In terms of prognosis, patients with c-Met-high EOC showed significantly worse survival than those with c-Met-low tumor (hazard ratio = 2.11, 95% confidence interval: 1.51-2.94, p < 0.0001). In conclusion, this meta-analysis indicates that high c-Met expression represents an adverse prognostic marker for patients with EOC.

HER2 Amplification in Tumors Activates PI3K/Akt Signaling Independent of HER3

Current evidence suggests that HER2-driven tumorigenesis requires HER3. This is likely due to the unique ability of HER3 to activate PI3K/Akt pathway signaling, which is not directly accessible to HER2. By genetic elimination of HER3 or shRNA knockdown of HER3 in HER2-amplified cancer cells, we find residual HER2-driven activation of PI3K/Akt pathway signaling that is driven by HER2 through direct and indirect mechanisms. Indirect mechanisms involved second messenger pathways, including Ras or Grb2. Direct binding of HER2 to PI3K occurred through p-Tyr1139, which has a weak affinity for PI3K but becomes significant at very high expression and phosphorylation. Mutation of Y1139 impaired the tumorigenic competency of HER2. Total elimination of HER3 expression in HCC1569 HER2-amplified cancer cells significantly impaired tumorigenicity only transiently, overcome by subsequent increases in HER2 expression and phosphorylation with binding and activation of PI3K. In contrast to activation of oncogenes by mutation, activation by overexpression was quantitative in nature: weak intrinsic activities were strengthened by overexpression, with additional gains observed through further increases in expression. Collectively, these data show that progressive functional gains by HER2 can increase its repertoire of activities such as the activation of PI3K and overcome its dependency on HER3.Significance: The intrinsic ability of HER2 to activate PI3K correlates with increased HER2 expression and can supplant the dependency upon HER3 for growth in HER2-amplified cancers. Cancer Res; 78(13); 3645-58. ©2018 AACR.

Prognostic value of MET copy number gain in non-small-cell lung cancer: an updated meta-analysis

The alterations of MET have been detected in non-small-cell lung cancer (NSCLC). However, the prognostic impact of MET gene copy number gain (CNG) has not been consistent among studies. We performed this meta-analysis to evaluate the prognostic value of high MET CNG in patients with NSCLC. A systematic computerized search of the electronic databases including PubMed, EMBASE, Google scholar, and Cochrane Library (up to November 2017) was carried out. From twenty-one studies, 7,647 patients were included in the pooled analysis of hazard ratios (HRs) with 95% confidence intervals (CIs) for disease-free survival or overall survival. Compared with patients with NSCLC showing low MET CNG, those with tumors harboring high MET CNG showed significantly worse survival (HR = 1.45, 95% CI: 1.16-1.80, p = 0.001). Subgroup analyses showed that high MET CNG significantly correlated with a poor prognosis especially in patients with adenocarcinoma (HR = 1.41, 95% CI: 1.11-1.79, p = 0.005) and Asian populations (HR = 1.58, 95% CI: 1.32-1.88, p < 0.00001).

In conclusion, this meta-analysis indicates that high MET CNG is an adverse prognostic factor in patients with NSCLC. Subgroup analyses suggest that high MET CNG is associated with a worse prognosis, especially in patients with adenocarcinoma and Asian populations. However, large prospective studies using standardized methods based on the homogeneous populations are warranted to validate the prognostic value of MET amplification in patients with NSCLC.

Superparamagnetic iron oxide nanoparticles modified with polyethylenimine and galactose for siRNA targeted delivery in hepatocellular carcinoma therapy

Introduction

A safe and effective in vivo siRNA delivery system is a prerequisite for liver tumor treatment based on siRNA cancer therapeutics. Nanoparticles based on superparamagnetic iron oxide (SPIO) provide a promising delivery system. In this study, we aimed to explore a novel nanoparticle, which is composed of SPIO.

Materials and methods

The particles have a core of iron oxide that is modified by galactose (Gal) and polyethylenimine (PEI), which act as shells, providing targeted delivery of therapeutic siRNA to the liver cancer. Gal-PEI-SPIO nanoparticles were synthesized, and the characteristics of the Gal-PEI-SPIO encapsulated with siRNA were analyzed.

Results

The particles remained nanoparticles and displayed negligible cytotoxicity when loaded with siRNA. In a serum stability assay, the Gal-PEI-SPIO nanoparticles could shield the siRNA from serum degradation and prolong the half-life of the siRNA in the system. Simultaneously, we found that the mixture could be efficiently taken up by Hepa1–6 cells in a flow cytometry assay. To study the anticancer effect, quantitative polymerase chain reaction and Western blotting were used to validate the silencing efficacy of the complexes in vitro. Subsequently, the nanoparticle mixtures were administered intravenously to tumor-bearing mice to explore the tissue distribution and the effect of the siRNA against cancer. We found that the nanoparticles could provide targeted siRNA delivery, accumulate easily in orthotopic tumors, enhance siRNA accumulation in the tumor tissues for 24 h and protect the siRNA from serum nuclease degradation in comparison with the control group. After these study procedures, the mice were sacrificed, and the tumors were removed to compare the tumor size and analyze the therapeutic effect on tumor growth. The tumor volume and the liver/body weight ratio were significantly reduced in the si-c-Met therapy groups. Additionally, the mRNA levels were also lower than those observed in the controls.

Conclusion

Based on these results, we concluded that Gal-PEI-SPIO represents a promising and efficient platform for siRNA delivery in tumor therapy.