Hepatocyte growth factor and Met in drug discovery

Met receptor is essential for MAVS-mediated antiviral innate immunity in epithelial cells independent of its kinase activity

Epithelial tissue is at the forefront of innate immunity, playing a crucial role in the recognition and elimination of pathogens. Met is a receptor tyrosine kinase that is necessary for epithelial cell survival, proliferation, and regeneration. Here, we showed that Met is essential for the induction of cytokine production by cytosolic nonself double-stranded RNA through retinoic acid-inducible gene-I-like receptors (RLRs) in epithelial cells. Surprisingly, the tyrosine kinase activity of Met was dispensable for promoting cytokine production. Rather, the intracellular carboxy terminus of Met interacted with mitochondrial antiviral-signaling protein (MAVS) in RLR-mediated signaling to directly promote MAVS signalosome formation. These studies revealed a kinase activity-independent function of Met in the promotion of antiviral innate immune responses, defining dual roles of Met in both regeneration and immune responses in the epithelium.

MET-Activating Ubiquitin Multimers

Receptor tyrosine kinases (RTKs) are generally activated through their dimerization and/or oligomerization induced by their cognate ligands, and one such RTK hepatocyte growth factor (HGF) receptor, known as MET, plays an important role in tissue regeneration. Here we show the development of ubiquitin (Ub)-based protein ligand multimers, referred to as U-bodies, which act as surrogate agonists for MET and are derived from MET-binding macrocyclic peptides. Monomeric Ub constructs (U-body) were first generated by genetic implantation of a macrocyclic peptide pharmacophore into a structural loop of Ub (lasso-grafting) and subsequent optimization of its flanking spacer sequences via mRNA display. Such U-body constructs exhibit potent binding affinity to MET, thermal stability, and proteolytic stability. The U-body constructs also partially/fully inhibited or enhanced HGF-induced MET-phosphorylation. Their multimerization to dimeric, tetrameric, and octameric U-bodies linked by an appropriate peptide linker yielded potent MET activation activity and downstream cell proliferation-promoting activity. This work suggests that lasso-grafting of macrocycles to Ub is an effective approach to devising protein-based artificial RTK agonists and it can be useful in the development of a new class of biologics for various therapeutic applications.

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.

Designing receptor agonists with enhanced pharmacokinetics by grafting macrocyclic peptides into fragment crystallizable regions

Short half-lives in circulation and poor transport across the blood-brain barrier limit the utility of cytokines and growth factors acting as receptor agonists. Here we show that surrogate receptor agonists with longer half-lives in circulation and enhanced transport rates across the blood-brain barrier can be generated by genetically inserting macrocyclic peptide pharmacophores into the structural loops of the fragment crystallizable (Fc) region of a human immunoglobulin. We used such 'lasso-grafting' approach, which preserves the expression levels of the Fc region and its affinity for the neonatal Fc receptor, to generate Fc-based protein scaffolds with macrocyclic peptides binding to the receptor tyrosine protein kinase Met. The Met agonists dimerized Met, inducing biological responses that were similar to those induced by its natural ligand. Moreover, lasso-grafting of the Fc region of the mouse anti-transferrin-receptor antibody with Met-binding macrocyclic peptides enhanced the accumulation of the resulting Met agonists in brain parenchyma in mice. Lasso-grafting may allow for designer protein therapeutics with enhanced stability and pharmacokinetics.

Growth factors and molecular-driven plasticity in neurological systems

It has been almost 70 years since the discovery of nerve growth factor (NGF), a period of a dramatic evolution in our understanding of dynamic growth, regeneration, and rewiring of the nervous system. In 1953, the extraordinary finding that a protein found in mouse submandibular glands generated a halo of outgrowing axons has now redefined our concept of the nervous system connectome. Central and peripheral neurons and their axons or dendrites are no longer considered fixed or static "wiring." Exploiting this molecular-driven plasticity as a therapeutic approach has arrived in the clinic with a slate of new trials and ideas. Neural growth factors (GFs), soluble proteins that alter the behavior of neurons, have expanded in numbers and our understanding of the complexity of their signaling and interactions with other proteins has intensified. However, beyond these "extrinsic" determinants of neuron growth and function are the downstream pathways that impact neurons, ripe for translational development and potentially more important than individual growth factors that may trigger them. Persistent and ongoing nuances in clinical trial design in some of the most intractable and irreversible neurological conditions give hope for connecting new biological ideas with clinical benefits. This review is a targeted update on neural GFs, their signals, and new therapeutic ideas, selected from an expansive literature.

Review on kidney diseases: types, treatment and potential of stem cell therapy

Renal disorders are an emerging global public health issue with a higher growth rate despite progress in supportive therapies. In order to find more promising treatments to stimulate renal repair, stem cell-based technology has been proposed as a potentially therapeutic option. The self-renewal and proliferative nature of stem cells raised the hope to fight against various diseases. Similarly, it opens a new path for the treatment and repair of damaged renal cells. This review focuses on the types of renal diseases; acute and chronic kidney disease-their statistical data, and the conventional drugs used for treatment. It includes the possible stem cell therapy mechanisms involved and outcomes recorded so far, the limitations of using these regenerative medicines, and the progressive improvement in stem cell therapy by adopting approaches like PiggyBac, Sleeping Beauty, and the Sendai virus. Specifically, about the paracrine activities of amniotic fluid stem cells, renal stem cells, embryonic stem cells, mesenchymal stem cell, induced pluripotent stem cells as well as other stem cells.

CircPRKCH modulates extracellular matrix formation and metabolism by regulating the miR-145/HGF axis in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative joint disease. Extracellular matrix (ECM) degradation is essential for OA progression. Previous studies have shown that circular RNAs (circRNAs) are involved in the pathological process of OA. CircPRKCH has been shown to be upregulated in OA chondrocytes. The present study was aimed to explore the roles of circPRKCH in vivo and in vitro models of OA and its underlying molecular mechanisms.

METHODS

IL-1β-induced chondrocytes and mice injected with monosodium iodoacetate were used as OA models in vitro and in vivo, respectively. RT-qPCR was performed to measure the expression of circPRKCH, miR-145, and HGF in cartilage tissues and chondrocytes. The interaction between miR-145 and circPRKCH or HGF was verified by a dual-luciferase reporter assay. Chondrocyte apoptosis, viability, and ECM-related proteins were examined by flow cytometry, MTT assay, and Western blotting, respectively. Histopathological changes were detected by HE and Safranin O-fast green staining.

RESULTS

The expression of circPRKCH and HGF was increased in OA cartilage tissues and IL-1β-treated chondrocytes, while miR-145 expression was decreased. IL-1β induced chondrocyte apoptosis and ECM degradation in chondrocytes. Moreover, circPRKCH promoted HGF expression and activated HGF/c-MET by directly binding to miR-145. miR-145 knockdown or HGF overexpression significantly reversed circPRKCH knockdown-mediated inhibition of apoptosis and ECM degradation in IL-1β-induced chondrocytes. Besides, miR-145 overexpression alleviated IL-1β-induced chondrocyte apoptosis and ECM degradation by inhibiting HGF/c-MET. Finally, circPRKCH knockdown reduced ECM degradation by regulating the miR-145/HGF axis in an experimental OA model in mice.

CONCLUSION

Our study demonstrated that circPRKCH promoted chondrocyte apoptosis and ECM degradation via the miR-145/HGF axis in OA, which may provide a novel target for OA treatment.

HGF/c-Met: A Key Promoter in Liver Regeneration

Hepatocyte growth factor (HGF) is a peptide-containing multifunctional cytokine that acts on various epithelial cells to regulate cell growth, movement and morphogenesis, and tissue regeneration of injured organs. HGF is sequestered by heparin-like protein in its inactive form and is widespread in the extracellular matrix of most tissues. When the liver loses its average mass, volume, or physiological and biochemical functions due to various reasons, HGF binds to its specific receptor c-Met (cellular mesenchymal-epithelial transition) and transmits the signals into the cells, and triggers the intrinsic kinase activity of c-Met. The downstream cascades of HGF/c-Met include JAK/STAT3, PI3K/Akt/NF-κB, and Ras/Raf pathways, affecting cell proliferation, growth, and survival. HGF has important clinical significance for liver fibrosis, hepatocyte regeneration after inflammation, and liver regeneration after transplantation. And the development of HGF as a biological drug for regenerative therapy of diseases, that is, using recombinant human HGF protein to treat disorders in clinical trials, is underway. This review summarizes the recent findings of the HGF/c-Met signaling functions in liver regeneration.

Role of Interleukin-1 in the pathogenesis of colorectal cancer: A brief look at anakinra therapy

Colorectal cancer (CRC) is known as one of the deadliest and most common cancers globally and causes nearly one million cancer deaths yearly. Like many malignancies, the immune system and its components play a crucial role in the pathogenesis of CRC. As multifunction mediators of the immune system, cytokines are involved in several inflammatory and anti-inflammatory responses. Interleukin-1 (IL-1) belongs to a family of 11 members and is involved in inflammatory responses. Beyond its biological role as a mediator of innate immune responses, it is also seen in chronic stress and inflammation and numerous pathological states. The role of IL-1 in malignancies can also be very significant because it has recently been shown that this cytokine can also be secreted from tumor cells and induce the recruitment of myeloid-derived immunosuppressive cells. As a result, the tumor microenvironment (TME) is affected and, despite being inflammatory, causes the onset and progression of tumor cells. Since surgery and chemotherapy are the first choices to treat patients with cancer, especially CRC, it is usually not well-prognosed, particularly in patients with metastatic lesions CRC. Therefore, targeted therapy may prolong the overall survival of CRC patients. Furthermore, evidence shows that anakinra has had satisfactory results in treating CRC. Therefore, this review summarized the role of IL-1 in the pathogenesis of CRC as well as immunotherapy based on inhibition of this cytokine in this type of cancer.

Engineering, Characterization, and Biological Evaluation of an Antibody Targeting the HGF Receptor

The Hepatocyte growth factor (HGF) and its receptor (MET) promote several physiological activities such as tissue regeneration and protection from cell injury of epithelial, endothelial, neuronal and muscle cells. The therapeutic potential of MET activation has been scrutinized in the treatment of acute tissue injury, chronic inflammation, such as renal fibrosis and multiple sclerosis (MS), cardiovascular and neurodegenerative diseases. On the other hand, the HGF-MET signaling pathway may be caught by cancer cells and turned to work for invasion, metastasis, and drug resistance in the tumor microenvironment. Here, we engineered a recombinant antibody (RDO24) and two derived fragments, binding the extracellular domain (ECD) of the MET protein. The antibody binds with high affinity (8 nM) to MET ECD and does not cross-react with the closely related receptors RON nor with Semaphorin 4D. Deletion mapping studies and computational modeling show that RDO24 binds to the structure bent on the Plexin-Semaphorin-Integrin (PSI) domain, implicating the PSI domain in its binding to MET. The intact RDO24 antibody and the bivalent Fab2, but not the monovalent Fab induce MET auto-phosphorylation, mimicking the mechanism of action of HGF that activates the receptor by dimerization. Accordingly, the bivalent recombinant molecules induce HGF biological responses, such as cell migration and wound healing, behaving as MET agonists of therapeutic interest in regenerative medicine. In vivo administration of RDO24 in the murine model of MS, represented by experimental autoimmune encephalomyelitis (EAE), delays the EAE onset, mitigates the early clinical symptoms, and reduces inflammatory infiltrates. Altogether, these results suggest that engineered RDO24 antibody may be beneficial in multiple sclerosis and possibly other types of inflammatory disorders.

c-Met-targeted chimeric antigen receptor T cells inhibit hepatocellular carcinoma cells in vitro and in vivo

c-Met is a hepatocyte growth factor receptor overexpressed in many tumors such as hepatocellular carcinoma (HCC). Therefore, c-Met may serve as a promising target for HCC immunotherapy. Modifying T cells to express c-Met-specific chimeric antigen receptor (CAR) is an attractive strategy in treating c-Met-positive HCC. This study aimed to systematically evaluate the inhibitory effects of 2^nd- and 3^rd-generation c-Met CAR-T cells on hepatocellular carcinoma (HCC) cells. Here, 2^nd- and 3^rd-generation c-Met CARs containing an anti-c-Met single-chain variable fragment (scFv) as well as the CD28 signaling domain and CD3ζ (c-Met-28-3ζ), the CD137 signaling domain and CD3ζ (c-Met-137-3ζ), or the CD28 and CD137 signaling domains and CD3ζ (c-Met-28-137-3ζ) were constructed, and their abilities to target c-Met-positive HCC cells were evaluated in vitro and in vivo. All c-Met CARs were stably expressed on T cell membrane, and c-Met CAR-T cells aggregated around c-Met-positive HCC cells and specifically killed them in vitro. c-Met-28-137-3ζ CAR-T cells secreted more interferon-gamma (IFN-γ) and interleukin 2 (IL-2) than c-Met-28-3ζ CAR-T cells and c-Met-137-3ζ CAR-T cells. Compared with c-Met low-expressed cells, c-Met CAR-T cells secreted more cytokines when co-cultured with c-Met high-expressed cells. Moreover, c-Met-28-137-3ζ CAR-T cells eradicated HCC more effectively in xenograft tumor models compared with the control groups. This study suggests that 3^rd-generation c-Met CAR-T cells are more effective in inhibiting c-Met-positive HCC cells than 2^nd-generation c-Met CAR-T cells, thereby providing a promising therapeutic intervention for c-Met-positive HCC.

Combination Therapy with a JNK Inhibitor and Hepatocyte Growth Factor for Restoration of Erectile Function in a Rat Model of Cavernosal Nerve Injury: Comparison with a JNK Inhibitor Alone or Hepatocyte Growth Factor Alone

We determined if combined administration of JNK-inhibitors and HGF (hepatocyte-growth-factor) would restore erectile-function through both antiapoptotic and regenerative effects in a rat model of cavernous-nerve-crush-injury (CNCI), and compared the results with administration of JNK-inhibitor alone or HGF alone. We randomized 70 rats into 5 groups: sham-surgery-group (S), CNCI (I) group, a group treated with once-daily intraperitoneal-administration of 10.0-mg/kg of JNK-inhibitors (J), a twice-weekly intracavernosal-administration of 4.2-μg HGF group (H), and a combined-treatment with 10.0-mg/kg JNK-inhibitors and 4.2-μg HGF group (J+H). We investigated erectile-responses to electrostimulation, histological-staining, caspase-3-activity-assay, and immunoblotting at two-weeks postoperatively. The three treatment groups showed improvements in erectile-responses (ICP/MAP and AUC/MAP ratios) compared to Group-I. The erectile-responses in Group-J+H were greater than those in Group-J or Group-H. The erectile-responses in Group-J+H were generally normalized. Caspase-3-activity and cJun-phosphorylation in Group-J and Group-J+H improved compared to Group-I, whereas caspase-3-activity in Group-H partially improved. Protein-expression of PECAM-1, eNOS-phosphorylation, and smooth-muscle content in Group-J+H were normalized, although those in Group-J or Group-H were partially restored. Combination therapy with JNK-inhibitors and HGF can generally normalize erectile-function through anti-apoptosis and preservation of endothelium or SM in rat CNCI model. The combined treatment appears to be superior to the respective agent alone in terms of therapeutic effects.

Pro-angiogenic activity and vasculogenic mimicry in the tumor microenvironment by leptin in cancer

The acquired ability to induce the formation of a functional vasculature is a hallmark of cancer. Blood vessels in tumors are formed through various mechanisms, among the most important in cancer biology, angiogenesis, and vasculogenic mimicry have been described. Leptin is one of the main adipokines secreted by adipocytes in normal breast tissue and the tumor microenvironment. Here, we provide information on the relationship between leptin and the development of angiogenesis and vasculogenic mimicry in different types of cancer. Here, we report that leptin activates different pathways such as JAK-STAT3, MAPK/ERK, PKC, JNK, p38, and PI3K-Akt to induce the expression of various angiogenic factors and vasculogenic mimicry. In vivo models, leptin induces blood vessel formation through the PI3K-Akt-mTOR pathway. Interestingly, the relationship between leptin and vasculogenic mimicry was more significant in breast cancer. The information obtained suggests that leptin could be playing an essential role in tumor survival and metastasis through the induction of vascular mechanisms such as angiogenesis and vasculogenic mimicry; thus, leptin-induced pathways could be suggested as a promising therapeutic target.

Overexpression of Hepatocyte growth factor and its soluble receptor (s-cMet) in the serum of patients with different grades of meningioma

OBJECTIVES

Meningiomas are the most common primary intracranial tumor. Hepatocyte growth factor (HGF) and its receptor, cMet, were shown to be involved in meningioma. This study was aimed to determine the concentration of HGF and soluble cMet (s-cMet) in the serum of patients with different grades of meningioma.

METHODS

Ninety serum samples from different grades of meningioma patients (42 cases of grade I, 28 grade II, 20 grade III) and 51 controls were included in this study. The serum total protein concentration (TPC) was measured by a Bio-Rad protein assay and serum concentration of HGF and s-cMet by enzyme linked immunosorbent assay (ELISA).

RESULTS

No significant change in the serum TPC of patients was seen as compared to controls. We also showed that serum HGF and s-cMet concentration in meningioma patients was higher than in controls. The results showed that starting from grades I to III meningioma, a significant increase in HGF and s-cMet serum concentration was observed (HGF; 380 ± 57.69, 430.27 ± 48.72, 596.36 ± 104.49 pg/ml, respectively, as compared to controls which was 327.72 ± 49.68 pg/ml and for s-cMet was 274.45 ± 45.05, 314.81 ± 38.71, 433.54 ± 51.81 ng/ml, respectively, as compared to controls which was 213.72 ± 29.13 ng/ml). The results showed that a high concentration of HGF and s-cMet is associated with advanced grades of meningioma.

CONCLUSION

It is concluded that HGF and s-cMet serum levels increased in meningioma patients and their concentration was significantly higher in more advanced grades of the disease. It is also suggested that HGF/s-cMet might be involved in the progression of meningioma.

HGF/c-MET pathway contributes to cisplatin-mediated PD-L1 expression in hepatocellular carcinoma

Cisplatin has been reported to promote the expression of programmed cell death ligand-1 (PD-L1) in some cancer cells. However, the underlying mechanism through which PD-L1 is transcriptionally regulated by cisplatin in hepatocellular carcinoma (HCC) cells remains largely unknown. In the present study, we found that the expression of hepatocyte growth factor (HGF), p-Akt, p-ERK, and PD-L1 was increased in cisplatin-treated SNU-368 and SNU-739 cells. HGF stimulation also increased PD-L1 expression in these cells. Moreover, Inhibition of HGF/c-MET, PI3K/Akt, and MEK/ERK signaling pathways can dramatically block cisplatin or HGF-induced PD-L1 expression in SNU-368 and SNU-739 cells. In vivo, combination PHA665752 with cisplatin significantly reduced tumor weight with increased infiltration of CD8⁺  T cells in the tumor. Taken together, our study suggested that HGF/c-Met axis-induced the activation of PI3K/Akt and MEK/ERK pathways contributes to cisplatin-mediated PD-L1 expression. These findings may provide an alternative avenue for the treatment of HCC.

Dimer Interface in Natural Variant NK1 Is Dispensable for HGF-Dependent Met Receptor Activation

NK1, a splicing variant of hepatocyte growth factor (HGF), binds to and activates Met receptor by forming an NK1 dimer and 2:2 complex with Met. Although the structural mechanism underlying Met activation by HGF remains incompletely resolved, it has been proposed that the NK1 dimer structure participates in this activation. We investigated the NK1 dimer interface’s role in Met activation by HGF. Because N127, V140, and K144 are closely involved in the head-to-tail NK1 dimer formation, mutant NK1 proteins with replacement of these residues by alanine were prepared. In Met tyrosine phosphorylation assays, N127-NK1, V140-NK1, and K144-NK1 showed 8.3%, 23.8%, and 52.2% activity, respectively, compared with wild-type NK1. Although wild-type NK1 promoted cell migration and scattering, N127-NK1, V140-NK1, and K144-NK1 hardly or marginally promoted them, indicating loss of activity of these mutant NK1 proteins to activate Met. In contrast, mutant HGFs (N127-HGF, V140-HGF, and K144-HGF) with the same amino acid replacements as in NK1 induced Met tyrosine phosphorylation and biological responses at levels comparable to those of wild-type HGF. These results indicate that the structural basis responsible for NK1-dependent Met dimer formation and activation differs from, or is at least distinguishable from, the structural basis responsible for HGF-dependent Met activation.

Association between the HGF/c‑MET signaling pathway and tumorigenesis, progression and prognosis of hepatocellular carcinoma (Review)

Hepatocellular carcinoma (HCC) is one of the most aggressive and lethal malignancies with a rising incidence, and is characterized by rapid progression, frequent metastasis, late diagnosis, high postoperative recurrence and poor prognosis. Therefore, novel treatment strategies for HCC, particularly advanced HCC, are urgently required. The hepatocyte growth factor (HGF)/c‑mesenchymal‑epithelial transition receptor (c‑MET) axis is a key signaling pathway in HCC and is strongly associated with its highly malignant features. Available treatments based on HGF/c‑MET inhibition may prolong the lifespan of patients with HCC; however, they do not achieve the desired therapeutic effects. The aim of the present article was to review the basic knowledge regarding the role of the HGF/c‑MET signaling pathway in HCC, and examine the association between the HGF/c‑MET signaling pathway and the tumorigenesis, progression and prognosis of HCC.

Targeting of extracellular protein-protein interactions with macrocyclic peptides

Targeting of extracellular protein-protein interactions (PPI) is emerging as a major application for de novo discovered macrocyclic peptides. Modern discovery platforms can routinely identify macrocyclic peptide ligands capable of highly selective modulation of extracellular signaling pathways; amenability to chemical synthesis and natural modularity of peptides additionally provides an avenue for their further structural elaboration, while the challenge of cell internalization can be minimized. Here, we discuss the recent progress in targeting extracellular PPIs with macrocyclic peptides by focusing on a number of recent case studies. We analyze the scope and potential limitations of the discovery systems in identifying functional macrocyclic ligands. We also highlight the recent technical advancements allowing for a more streamlined discovery pipeline and our brief perspective in this field.

Bispecific c-Met/PD-L1 CAR-T Cells Have Enhanced Therapeutic Effects on Hepatocellular Carcinoma

T cells expressing chimeric antigen receptors, especially CD19 CAR-T cells have exhibited effective antitumor activities in B cell malignancies, but due to several factors such as antigen escape effects and tumor microenvironment, their curative potential in hepatocellular carcinoma has not been encouraging. To reduce the antigen escape risk of hepatocellular carcinoma, this study was to design and construct a bispecific CAR targeting c-Met and PD-L1. c-Met/PD-L1 CAR-T cells were obtained by lentiviral transfection, and the transfection efficiency was monitored by flow cytometry analysis. LDH release assays were used to elucidate the efficacy of c-Met/PD-L1 CAR-T cells on hepatocellular carcinoma cells. In addition, xenograft models bearing human hepatocellular carcinoma were constructed to detect the antitumor effect of c-Met/PD-L1 CAR-T cells in vivo. The results shown that this bispecific CAR was manufactured successfully, T cells modified with this bispecific CAR demonstrated improved antitumor activities against c-Met and PD-L1 positive hepatocellular carcinoma cells when compared with those of monovalent c-Met CAR-T cells or PD-L1 CAR-T cells but shown no distinct cytotoxicity on hepatocytes in vitro. In vivo experiments shown that c-Met/PD-L1 CAR-T cells significantly inhibited tumor growth and improve survival persistence compared with other groups. These results suggested that the design of single-chain, bi-specific c-Met/PD-L1 CAR-T is more effective than that of monovalent c-Met CAR-T for the treatment of hepatocellular carcinoma., and this bi-specific c-Met/PD-L1 CAR is rational and implementable with current T-cell engineering technology.

Anti-tumor efficacy of human anti-c-met CAR-T cells against papillary renal cell carcinoma in an orthotopic model

Chimeric antigen receptor (CAR)‐T cell therapy has shown salient efficacy in cancer immunotherapy, particularly in the treatment of B cell malignancies. However, the efficacy of CAR‐T for solid tumors remains inadequate. In this study, we displayed that c‐met is an appropriate therapeutic target for papillary renal cell carcinoma (PRCC) using clinical samples, developed an anti‐human c‐met CAR‐T cells, and investigated the anti‐tumor efficacy of the CAR‐T cells using an orthotopic mouse model as pre‐clinical research. Administration of the anti‐c‐met CAR‐T cells induced marked infiltration of the CAR‐T cells into the tumor tissue and unambiguous suppression of tumor growth. Furthermore, in combination with axitinib, the anti‐tumor efficacy of the CAR‐T cells was synergistically augmented. Taken together, our current study demonstrated the potential for clinical application of anti‐c‐met CAR‐T cells in the treatment of patients with PRCC.

Chinese herbal formula QHF inhibits hepatocellular carcinoma metastasis via HGF/c-Met signaling pathway

Hepatocellular Carcinoma (HCC) is one of the most common malignant tumors, and high recurrence and metastasis are the major obstacles to successful treatment of HCC. Traditional Chinese medicine has little known and unique advantages in the treatment of HCC. Previous studies have confirmed that Chinese herbal formula Qingrejiedu (clears away heat and toxins), Huoxuehuayu (promotes blood flow to remove stasis) and Fuzhengguben (strengthens healthy qi and root) (QHF) has a significant effect on patients with advanced HCC, improves the quality of life and prolongs the survival time of patients significantly. In this study, we investigated the effect of QHF on proliferation, migration and invasion of human high metastatic hepatocellular carcinoma cell line HCCLM3 and its underlying mechanism. The results from our in vitro experiments showed that QHF has the ability to inhibit the proliferation by inducing G2/M phase cell cycle arrest and induce apoptosis. Moreover, QHF can also inhibit migration and invasion of HCCLM3 cells and the expression of the p-c-Met protein in HCCLM3 cells was down-regulated. c-Met is closely related to the metastasis of HCC, then we constructed a stable transfected cell line HepG2-met with high expression of c-Met by transfection. Further study in vivo revealed that c-Met gene will promote the growth of tumors and lung metastases in nude mice, and QHF intervention can reduce tumor lung metastases by inhibiting the HGF/c-Met signaling pathway. In conclusion, our study reveals that QHF can inhibit the proliferation, migration and invasion of HCCLM3, and this effect may be related to inhibiting HGF/c-Met signaling pathway.

Structural and Functional Insight Into the Glycosylation Impact Upon the HGF/c-Met Signaling Pathway

Upon interactions with its specific ligand hepatocyte growth factor (HGF), the c-Met signal is relayed to series of downstream pathways, exerting essential biological roles. Dysregulation of the HGF-c-Met signaling pathway has been implicated in the onset, progression and metastasis of various cancers, making the HGF-c-Met axis a promising therapeutic target. Both c-Met and HGF undergo glycosylation, which appears to be biologically relevant to their function and structural integrity. Different types of glycoconjugates in the local cellular environment can also regulate HGF/c-Met signaling by distinct mechanisms. However, detailed knowledge pertaining to the glycosylation machinery of the HGF-c-Met axis as well as its potential applications in oncology research is yet to be established. This mini review highlights the significance of the HGF-c-Met signaling pathway in physiological and pathological context, and discusses the molecular mechanisms by which affect the glycosylation of the HGF-c-Met axis. Owing to the crucial role played by glycosylation in the regulation of HGF/c-Met activity, better understanding of this less exploited field may contribute to the development of novel therapeutics targeting glycoepitopes.

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.

The constitutive high-affinity Met-binding site in the kringle domain is dispensable for the signalling activity of hepatocyte growth factor

Activation of a tyrosine kinase receptor Met by hepatocyte growth factor (HGF) requires binding of proteolytically activated, two-chain (tc) HGF, but the biochemical detail of this ligand–receptor interaction specificity remains elusive because biologically inactive single chain (sc) HGF can also bind to Met with high affinity. We found that this proteolysis-independent Met binding can be eliminated by mutagenesis introduced in the kringle domain without losing the ability to bind and activate cellular Met receptor after proteolytic activation, arguing against this site’s involvement in the physiological signalling. This non-signal producing Met–HGF interaction can also be eliminated by addition of a heparin mimetic sucrose octasulphate (SOS). By including SOS in the running buffer, we succeeded in detecting cleavage-dependent tcHGF–Met complex formation by size exclusion chromatography.

Piperidine carbamate peptidomimetic inhibitors of the serine proteases HGFA, matriptase and hepsin

Matriptase and hepsin are type II transmembrane serine proteases (TTSPs). Along with related S1 trypsin like serine protease HGFA (hepatocyte growth factor activator), their unregulated proteolytic activity has been associated with cancer including tumor progression and metastasis. These three proteases have two substrates in common, hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP), the ligands for MET and recepteur d'origine nantais (RON) receptor tyrosine kinases. Mechanism-based tetrapeptide and benzamidine inhibitors of these proteases have been shown to block HGF/MET and MSP/RON cancer cell signaling. Herein, we have rationally designed a new class of peptidomimetic hybrid small molecule piperidine carbamate dipeptide inhibitors comparable in potency to much larger tetrapeptides. We have identified multiple compounds which have potent activity against matriptase and hepsin and with excellent selectivity over the off-target serine proteases factor Xa and thrombin.

The "-OMICS" facet of melanoma: Heterogeneity of genomic, proteomic and metabolomic biomarkers

In the recent decade, cutting edge molecular and proteomic analysis platforms revolutionized biomarkers discovery in cancers. Melanoma is the prototype with over 51,100 biomarkers discovered and investigated thus far. These biomarkers include tissue based tumor cell and tumor microenvironment biomarkers and circulating biomarkers including tumor DNA (cf-DNA), mir-RNA, proteins and metabolites. These biomarkers provide invaluable information for diagnosis, prognosis and play an important role in prediction of treatment response. In this review, we summarize the most recent discoveries in each of these biomarker categories. We will discuss the challenges in their implementation and standardization and conclude with some perspectives in melanoma biomarker research.

Distinct Localization of Mature HGF from its Precursor Form in Developing and Repairing the Stomach

Hepatocyte growth factor (HGF) is secreted as an inactive single-chain HGF (scHGF); however, only proteolytically processed two-chain HGF (tcHGF) can activate the MET receptor. We investigated the localization of tcHGF and activated/phosphorylated MET (pMET) using a tcHGF-specific antibody. In day 16.5 mouse embryos, total HGF (scHGF + tcHGF) was mainly localized in smooth muscle cells close to, but separate from, MET-positive epithelial cells in endodermal organs, including the stomach. In the adult stomach, total HGF was localized in smooth muscle cells, and tcHGF was mainly localized in the glandular base region. Immunostaining for pMET and Lgr5-driven green fluorescent protein (GFP) indicated that pMET localization overlapped with Lgr5⁺ gastric stem cells. HGF promoted organoid formation similar to EGF, indicating the potential for HGF to promote the survival and growth of gastric stem cells. pMET and tcHGF localizations changed during regeneration following gastric injury. These results indicate that MET is constantly activated in gastric stem cells and that the localization of pMET differs from the primary localization of precursor HGF but has a close relationship to tcHGF. Our results suggest the importance of the microenvironmental generation of tcHGF in the regulation of development, regeneration, and stem cell behavior.

3-Cl-AHPC inhibits pro-HGF maturation by inducing matriptase/HAI-1 complex formation

Matriptase is an epithelia-specific membrane-anchored serine protease, and its dysregulation is highly related to the progression of a variety of cancers. Hepatocyte growth factor activator inhibitor-1 (HAI-1) inhibits matriptase activity through forming complex with activated matriptase. The balance of matriptase activation and matriptase/HAI-1 complex formation determines the intensity and duration of matriptase activity. 3-Cl-AHPC, 4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid, is an adamantly substituted retinoid-related molecule and a ligand of retinoic acid receptor γ (RARγ). 3-Cl-AHPC is of strong anti-cancer effect but with elusive mechanisms. In our current study, we show that 3-Cl-AHPC time- and dose- dependently induces matriptase/HAI-1 complex formation, leading to the suppression of activated matriptase in cancer cells and tissues. Furthermore, 3-Cl-AHPC promotes matriptase shedding but without increasing the activity of shed matriptase. Moreover, 3-Cl-AHPC inhibits matriptase-mediated cleavage of pro-HGF through matriptase/HAI-1 complex induction, resulting in the suppression of pro-HGF-stimulated signalling and cell scattering. Although 3-Cl-AHPC binds to RARγ, its induction of matriptase/HAI-1 complex is not RARγ dependent. Together, our data demonstrates that 3-Cl-AHPC down-regulates matriptase activity through induction of matriptase/HAI-1 complex formation in a RARγ-independent manner, providing a mechanism of 3-Cl-AHPC anti-cancer activity and a new strategy to inhibit abnormal matriptase activity via matriptase/HAI-1 complex induction using small molecules.

Endothelial cells from pulmonary endarterectomy specimens possess a high angiogenic potential and express high levels of hepatocyte growth factor

BACKGROUND

Impaired angiogenesis is assumed to be an important factor in the development of chronic thromboembolic pulmonary hypertension (CTEPH). However, the role of endothelial cells (ECs) in CTEPH remains unclear. The aim of this study was to investigate the angiogenic potential of ECs from pulmonary endarterectomy (PEA) specimens.

METHODS

We isolated ECs from PEA specimens (CTEPH-ECs) and control EC lines from the intact pulmonary arteries of patients with peripheral lung cancers, using a MACS system. These cells were analyzed in vitro including PCR-array analysis, and the PEA specimens were analyzed with immunohistochemistry. Additionally, the serum HGF levels were determined in CTEPH patients.

RESULTS

A three-dimensional culture assay revealed that CTEPH-ECs were highly angiogenic. An angiogenesis-focused gene PCR array revealed a high expression of hepatocyte growth factor (HGF) in CTEPH-ECs. The high expression of HGF was also confirmed in the supernatant extracted from PEA specimens. The immunohistochemical analysis showed expression of HGF on the surface of the thrombus vessels. The serum HGF levels in CTEPH patients were higher than those in pulmonary thromboembolism survivors.

CONCLUSION

Our study suggests that there are ECs with pro-angiogenetic character and high expression of HGF in PEA specimens. It remains unknown how these results are attributable to the etiology. However, further investigation focused on the HGF pathway may provide novel diagnostic and therapeutic tools for patients with CTEPH.

The Role of Interleukin-1 in the Pathogenesis of Cancer and its Potential as a Therapeutic Target in Clinical Practice

Interleukin-1 (IL-1) has long been known to be a key mediator of immunity and inflammation. Its dysregulation has been implicated in recent years in tumorigenesis and tumor progression, and its upregulation is thought to be associated with many tumors. Overexpression of the IL-1 agonists IL-1α and IL-1β has been shown to promote tumor invasiveness and metastasis by inducing the expression of angiogenic genes and growth factors. IL-1 blockers such as anakinra and canakinumab are already approved and widely used for the treatment of some autoimmune and autoinflammatory diseases and are currently being tested in preclinical and human clinical trials for cancer therapy. In this paper we review the most recent discoveries regarding the association between IL-1 dysregulation and cancer and present the novel IL-1 blockers currently being tested in cancer therapy and their corresponding clinical trials.

Cellular signaling and gene expression profiles evoked by a bivalent macrocyclic peptide that serves as an artificial MET receptor agonist

Non-native ligands for growth factor receptors that are generated by chemical synthesis are applicable to therapeutics. However, non-native ligands often regulate cellular signaling and biological responses in a different manner than native ligands. Generation of surrogate ligands comparable to native ligands is a challenging need. Here we investigated changes in signal transduction and gene expression evoked by a bivalent macrocyclic peptide (aMD5-PEG11) capable of high-affinity binding to the MET/hepatocyte growth factor (HGF) receptor. Binding of aMD5-PEG11 to the MET extracellular region was abolished by deletion of the IPT3−IPT4 domain, indicating the involvement of IPT3−IPT4 in the binding of aMD5-PEG11 to the MET receptor. aMD5-PEG11 induced dimerization and activation of the MET receptor and promoted cell migration that was comparable to induction of these activities by HGF. Signal activation profiles indicated that aMD5-PEG11 induced phosphorylation of intracellular signaling molecules, with a similar intensity and time dependency as HGF. In 3-D culture, aMD5-PEG11 as well as HGF induced epithelial tubulogenesis and up-regulated the same sets of functionally classified genes involved in multicellular organism development. Thus, a non-native surrogate ligand that consisted of a bivalent macrocyclic peptide can serve as an artificial MET receptor agonist that functionally substitutes for the native ligand, HGF.

A PRDX1-p38α heterodimer amplifies MET-driven invasion of IDH-wildtype and IDH-mutant gliomas

The Peroxiredoxin 1 (PRDX1) gene maps to chromosome arm 1p and is hemizygously deleted and epigenetically silenced in isocitrate dehydrogenase 1 or 2 (IDH)-mutant and 1p/19q-codeleted oligodendroglial tumors. In contrast, IDH-wildtype astrocytic gliomas including glioblastomas mostly lack epigenetic silencing and express PRDX1 protein. In our study, we investigated how PRDX1 contributes to the infiltrative growth of IDH-wildtype gliomas. Focusing on p38α-dependent pathways, we analyzed clinical data from 133 patients of the NOA-04 trial cohort to look for differences in the gene expression profiles of gliomas with wildtype or mutant IDH. Biochemical interaction studies as well as in vitro and ex vivo migration studies were used to establish a biological role of PRDX1 in maintaining pathway activity. Whole-brain high-resolution ultramicroscopy and survival analyses of pre-clinical mouse models for IDH-wildtype gliomas were then used for in vivo confirmation. Based on clinical data, we found that the absence of PRDX1 is associated with changes in the expression of MET/HGF signaling components. PRDX1 forms a heterodimer with p38α mitogen-activated protein kinase 14 (MAPK14), stabilizing phospho-p38α in glioma cells. This process amplifies hepatocyte growth factor (HGF)-mediated signaling and stimulates actin cytoskeleton dynamics that promote glioma cell migration. Whole-brain high-resolution ultramicroscopy confirms these findings, indicating that PRDX1 promotes glioma brain invasion in vivo. Finally, reduced expression of PRDX1 increased survival in mouse glioma models. Thus, our preclinical findings suggest that PRDX1 expression levels may serve as a molecular marker for patients who could benefit from targeted inhibition of MET/HGF signaling.

The Impact of the Epithelial-Mesenchymal Transition Regulator Hepatocyte Growth Factor Receptor/Met on Skin Immunity by Modulating Langerhans Cell Migration

Langerhans cells (LCs), the epidermal dendritic cell (DC) subset, express the transmembrane tyrosine kinase receptor Met also known as hepatocyte growth factor (HGF) receptor. HGF is the exclusive ligand of Met and upon binding executes mitogenic, morphogenic, and motogenic activities to various cells. HGF exerts anti-inflammatory activities via Met signaling and was found to regulate various functions of immune cells, including differentiation and maturation, cytokine production, cellular migration and adhesion, and T cell effector function. It has only recently become evident that a number of HGF-regulated functions in inflammatory processes and immune responses are imparted via DCs. However, the mechanisms by which Met signaling in DCs conveys its immunoregulatory effects have not yet been fully understood. In this review, we focus on the current knowledge of Met signaling in DCs with particular attention on the morphogenic and motogenic activities. Met signaling was shown to promote DC mobility by regulating matrix metalloproteinase activities and adhesion. This is a striking resemblance to the role of Met in regulating a cell fate program during embryonic development, wound healing, and in tumor invasion known as epithelial–mesenchymal transition (EMT). Hence, we propose the concept that an EMT program is executed by Met signaling in LCs.

Different growth and metastatic phenotypes associated with a cell-intrinsic change of Met in metastatic melanoma

A dynamic phenotypic change contributes to the metastatic progression and drug resistance in malignant melanoma. Nevertheless, mechanisms for a phenotypic change have remained to be addressed. Here, we show that Met receptor expression changes in a cell-autonomous manner and can distinguish phenotypical differences in growth, as well as in metastatic and drug-resistant characteristics. In metastatic melanoma, the cells are composed of Met-low and Met-high populations. Met-low populations have stem-like gene expression profiles, are resistant to chemotherapeutic agents, and have shown abundant angiogenesis and rapid tumor growth in subcutaneous inoculation. Met-high populations have a differentiated phenotype, are relatively resistant to B-RAF inhibitor, and are highly metastatic to the lungs. Met plays a definitive role in lung metastasis because the lung metastasis of Met-high cells requires Met, and treatment of mice with the Met-containing exosomes from Met-high cells facilitates lung metastasis by Met-low cells. Clonal cell fate analysis showed the hierarchical phenotypical changes from Met-low to Met-high populations. Met-low cells either showed self-renewal or changed into Met-high cells, whereas Met-high cells remained Met-high. Clonal transition from Met-low to Met-high cells accompanied changes in the gene expression profile, in tumor growth, and in metastasis that were similar to those in Met-high cells. These findings indicate that malignant melanoma has the ability to undergo phenotypic change by a cell-intrinsic/autonomous mechanism that can be characterized by Met expression.

MicroRNA-7-5p mediates the signaling of hepatocyte growth factor to suppress oncogenes in the MCF-10A mammary epithelial cell

MicroRNA-7 (miR-7) is a non-coding RNA of 23-nucleotides that has been shown to act as a tumor suppressor in various cancers including breast cancer. Although there have been copious studies on the action mechanisms of miR-7, little is known about how the miR is controlled in the mammary cell. In this study, we performed a genome-wide expression analysis in miR-7-transfected MCF-10A breast cell line to explore the upstream regulators of miR-7. Analysis of the dysregulated target gene pool predicted hepatocyte growth factor (HGF) as the most plausible upstream regulator of miR-7. MiR-7 was upregulated in MCF-10A cells by HGF, and subsequently downregulated upon treatment with siRNA against HGF. However, the expression of HGF did not significantly change through either an upregulation or downregulation of miR-7 expression, suggesting that HGF acts upstream of miR-7. In addition, the target genes of miR-7, such as EGFR, KLF4, FAK, PAK1 and SET8, which are all known oncogenes, were downregulated in HGF-treated MCF-10A; in contrast, knocking down HGF recovered their expression. These results indicate that miR-7 mediates the activity of HGF to suppress oncogenic proteins, which inhibits the development of normal cells, at least MCF-10A, into cancerous cells.

Interleukin-1 receptor antagonist inhibits angiogenesis via blockage IL-1α/PI3K/NF-κβ pathway in human colon cancer cell

PURPOSE

This article investigates the relationship between cancer cells and stromal cells in carcinoma cell living microenvironment and elucidates the mechanism that interleukin-1 receptor antagonist (IL-1RA) blocks metastatic potential in colon cancer.

METHODS

Western blot and RT-PCR assay were used to determine the expression of hepatocyte growth factor (HGF) and IL-1α in colon carcinoma cells and stromal cells. Effect of IL-1RA and HGF on metastatic potential of colon cancer cells were examined by proliferation, invasion, and angiogenesis assays. The interactional role of IL-1RA and HGF were detected by ELISA assay, invasion, and angiogenesis assay making up a co-culture system consisting of stromal and colon cancer cells in cells living microenvironment.

RESULTS

IL-1α was expressed in human umbilical vein endothelial cells (HUVECs) and HT-29 and WiDr (colon cancer cell lines with higher liver metastatic potential). HGF was expressed only in fibroblast. HGF secretion from fibroblasts was significantly inhibited by IL-1RA (P<0.01). Furthermore, IL-1RA could significantly inhibit migration, proliferation, and angiogenesis of HUVECs (P<0.01). In the double co-culture system, there is a high liver metastatic potential of colon cancer cell line (HT-29) because it can secrete autocrine IL-1α, significantly enhanced angiogenesis compared with low liver metastatic cell line (CaCo-2) (P<0.01), which does not secrete IL-1α. On the contrary, blockage of autocrine IL-1α by IL-1RA might significantly decrease metastatic potential of colon carcinoma cells through downregulation of IL-1α/PI3K/NF-κB pathway.

CONCLUSION

IL-1 receptor antagonist (IL-1RA) is an important inhibitor in metastatic process of colon carcinoma cell. Based on the above results, we suggest that IL-1RA may be a promising new therapeutic approach in inhibiting colon cancer with IL-1-producing patients.

KLK14 interactions with HAI-1 and HAI-2 serine protease inhibitors: A molecular dynamics and relative free-energy calculations study

Kallikrein 14 (KLK14) is a serine protease linked to several pathologies including prostate cancer and positively correlates with Gleason score. Though KLK14 functioning in cancer is poorly understood, it has been implicated in HGF/Met signaling, given that KLK14 proteolytically inhibits HGF activator-inhibitor 1 (HAI-1), which strongly inhibits pro-HGF activators, thereby contributing to tumor progression. In this work, KLK14 binding to either hepatocyte growth factor activator inhibitor type-1 (HAI-1) or type-2 (HAI-2) was essayed using homology modeling, molecular dynamic simulations and free-energy calculations through MM/PBSA and MM/GBSA. KLK14 was successfully modeled. Calculated free energies suggested higher binding affinity for the KLK14/HAI-1 interaction than for KLK14/HAI-2. This difference in binding affinity is largely explained by the higher stability of the hydrogen-bond networks in KLK14/HAI-1 along the simulation trajectory. A key arginine residue in both HAI-1 and HAI-2 is responsible for their interaction with the S1 pocket in KLK14. Additionally, MM/GBSA free-energy decomposition postulates that KLK14 Asp174 and Trp196 are hotspots for binding HAI-1 and HAI-2.

Targeting the hepatocyte growth factor/Met pathway in cancer

Hepatocyte growth factor (HGF)-induced activation of its cell surface receptor, the Met tyrosine kinase, drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Typical paracrine HGF/Met signaling is regulated by HGF activation at target cell surfaces, HGF binding-induced receptor activation, internalization and degradation. Despite these controls, HGF/Met signaling contributes to oncogenesis, tumor angiogenesis and invasiveness, and tumor metastasis in many types of cancer, leading to the rapid growth of pathway-targeted anticancer drug development programs. We review here HGF and Met structure and function, basic properties of HGF/Met pathway antagonists now in clinical development, and recent clinical trial results. Presently, the main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment include optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of effective therapy combinations. The wealth of basic information, analytical reagents and model systems available regarding normal and oncogenic HGF/Met signaling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective cancer treatment.

Hepatocyte growth factor/MET in cancer progression and biomarker discovery

Signaling driven by hepatocyte growth factor (HGF) and MET receptor facilitates conspicuous biological responses such as epithelial cell migration, 3‐D morphogenesis, and survival. The dynamic migration and promotion of cell survival induced by MET activation are bases for invasion–metastasis and resistance, respectively, against targeted drugs in cancers. Recent studies indicated that MET in tumor‐derived exosomes facilitates metastatic niche formation and metastasis in malignant melanoma. In lung cancer, gene amplification‐induced MET activation and ligand‐dependent MET activation in an autocrine/paracrine manner are causes for resistance to epidermal growth factor receptor tyrosine kinase inhibitors and anaplastic lymphoma kinase inhibitors. Hepatocyte growth factor secreted in the tumor microenvironment contributes to the innate and acquired resistance to RAF inhibitors. Changes in serum/plasma HGF, soluble MET (sMET), and phospho‐MET have been confirmed to be associated with disease progression, metastasis, therapy response, and survival. Higher serum/plasma HGF levels are associated with therapy resistance and/or metastasis, while lower HGF levels are associated with progression‐free survival and overall survival after treatment with targeted drugs in lung cancer, gastric cancer, colon cancer, and malignant melanoma. Urinary sMET levels in patients with bladder cancer are higher than those in patients without bladder cancer and associated with disease progression. Some of the multi‐kinase inhibitors that target MET have received regulatory approval, whereas none of the selective HGF‐MET inhibitors have shown efficacy in phase III clinical trials. Validation of the HGF‐MET pathway as a critical driver in cancer development/progression and utilization of appropriate biomarkers are key to development and approval of HGF‐MET inhibitors for clinical use.

Effects of HGF gene polymorphisms and protein expression on transhepatic arterial chemotherapeutic embolism efficacy and prognosis in patients with primary liver cancer

Objective

To investigate the correlations of two hepatocyte growth factor (HGF) gene polymorphisms (rs5745652 and rs2074725) and their protein expression levels with the efficacy of transhepatic arterial chemotherapeutic embolism (TACE) and prognosis in patients with primary liver cancer (PLC).

Methods

From March 2011 to June 2012, 109 PLC patients (the case group) who chose TACE as primary treatment and 80 healthy people (the control group) who had undergone physical examination in The First Affiliated Hospital, Zhejiang University were selected during the same period. Gene polymorphisms of HGF rs5745652 and HGF rs2074725 were detected. Serum HGF level, treating efficacy, survival quality, and 3-year survival rate for PLC patients who received TACE were observed.

Results

There were significant differences in genotype and allele frequencies of HGF rs5745652 and HGF rs2074725, between the case and control groups (all P<0.05). Compared with CT+TT genotype of HGF rs5745652, patients carrying CC genotype had lower serum HGF levels, higher efficacy, better survival quality, and prolonged 3-year survival rate (all P<0.05). In rs2074725, patients carrying CA+AA genotype had lower serum HGF levels, higher efficacy, better survival quality, and prolonged 3-year survival rate compared with patients carrying rs2074725 CC genotype (all P<0.05). Gene polymorphisms of HGF rs5745652 and HGF rs2074725, tumor size, and Barcelona Clinic Liver Cancer stage were independent prognostic factors for PLC (P<0.05).

Conclusion

Our results indicated that HGF gene polymorphisms affect TACE efficacy and survival quality of PLC patients. Patients with HGF CC genotype of rs5745652 and CA+AA genotype of rs2074725 had decreased HGF level, better curative effect, high survival quality, and a good prognosis after TACE treatment.

Quantification of growth factor signaling and pathway cross talk by live-cell imaging

Peptide growth factors stimulate cellular responses through activation of their transmembrane receptors. Multiple intracellular signaling cascades are engaged following growth factor-receptor binding, leading to short- and long-term biological effects. Each receptor-activated signaling pathway does not act in isolation but rather interacts at different levels with other pathways to shape signaling networks that are distinctive for each growth factor. To gain insights into the specifics of growth factor-regulated interactions among different signaling cascades, we developed a HeLa cell line stably expressing fluorescent live-cell imaging reporters that are readouts for two major growth factor-stimulated pathways, Ras-Raf-Mek-ERK and phosphatidylinositol (PI) 3-kinase-Akt. Incubation of cells with epidermal growth factor (EGF) resulted in rapid, robust, and sustained ERK signaling but shorter-term activation of Akt. In contrast, hepatocyte growth factor induced sustained Akt signaling but weak and short-lived ERK activity, and insulin-like growth factor-I stimulated strong long-term Akt responses but negligible ERK signaling. To address potential interactions between signaling pathways, we employed specific small-molecule inhibitors. In cells incubated with EGF or platelet-derived growth factor-AA, Raf activation and the subsequent stimulation of ERK reduced Akt signaling, whereas Mek inhibition, which blocked ERK activation, enhanced Akt and turned transient effects into sustained responses. Our results reveal that individual growth factors initiate signaling cascades that vary markedly in strength and duration and demonstrate in living cells the dramatic effects of cross talk from Raf and Mek to PI 3-kinase and Akt. Our data further indicate how specific growth factors can encode distinct cellular behaviors by promoting complex interactions among signaling pathways.

Hepatocyte growth factor in physiology and infectious diseases

Hepatocyte growth factor (HGF) is a pleiotropic cytokine composed of an α-chain and a β-chain, and these chains contain four kringle domains and a serine protease-like structure, respectively. The receptor for HGF was identified as the c-met proto-oncogene product of transmembrane receptor tyrosine kinase. HGF-induced signaling through the receptor Met provokes dynamic biological responses that support morphogenesis, regeneration, and the survival of various cells and tissues, which includes hepatocytes, renal tubular cells, and neurons. Characterization of tissue-specific Met knockout mice has further indicated that the HGF-Met system modulates immune cell functions and also plays an inhibitory role in the progression of chronic inflammation and fibrosis. However, the biological actions that are driven by the HGF-Met pathway all play a role in the acquisition of the malignant characteristics in tumor cells, such as invasion, metastasis, and drug resistance in the tumor microenvironment. Even though oncogenic Met signaling remains the major research focus, the HGF-Met axis has also been implicated in infectious diseases. Many pathogens try to utilize host HGF-Met system to establish comfortable environment for infection. Their strategies are not only simply change the expression level of HGF or Met, but also actively hijack HGF-Met system and deregulating Met signaling using their pathogenic factors. Consequently, the monitoring of HGF and Met expression, along with real-time detection of Met activation, can be a beneficial biomarker of these infectious diseases. Preclinical studies designed to address the therapeutic significance of HGF have been performed on injury/disease models, including acute tissue injury, chronic fibrosis, and cardiovascular and neurodegenerative diseases. Likewise, manipulating the HGF-Met system with complete control will lead to a tailor made treatment for those infectious diseases.

Functional and therapeutic relevance of hepatocyte growth factor/c-MET signaling in synovial sarcoma

Synovial sarcoma (SS) is an aggressive soft tissue sarcoma with a poor prognosis and, thus, novel therapeutic strategies for SS are urgently required. In the present study, we investigated the functional and therapeutic relevance of hepatocyte growth factor (HGF)/c‐MET signaling in SS. Both HGF and c‐MET were highly expressed in Yamato‐SS cells, resulting in activation of c‐MET and its downstream AKT and extracellular signal‐regulated kinase signaling pathways, whereas c‐MET was expressed but not activated in SYO‐1 or HS‐SY‐II cells. c‐MET‐activated Yamato‐SS cells showed higher anchorage‐independent growth ability and less sensitivity to chemotherapeutic agents than did c‐MET‐inactivated SYO‐1 or HS‐SY‐II cells. INC280, a selective c‐MET inhibitor, inhibited growth of Yamato‐SS cells both in vitro and in vivo but not that of SYO‐1 or HS‐SY‐II cells. INC280 induced cell cycle arrest and apoptosis, and blocked phosphorylation of c‐MET and its downstream effectors in Yamato‐SS cells. Co‐expression of HGF and c‐MET in SS clinical samples correlated with a poor prognosis in patients with SS. Taken together, activation of HGF/c‐MET signaling in an autocrine fashion leads to an aggressive phenotype in SS and targeting of this signaling exerts superior antitumor effects on c‐MET‐activated SS. HGF/c‐MET expression status is a potential biomarker for identification of SS patients with a worse prognosis who can benefit from c‐MET inhibitors.

Integrin-FAK signaling rapidly and potently promotes mitochondrial function through STAT3

Background

STAT3 is increasingly becoming known for its non-transcriptional regulation of mitochondrial bioenergetic function upon activation of its S727 residue (S727-STAT3). Lengthy mitochondrial dysfunction can lead to cell death. We tested whether an integrin-FAK-STAT3 signaling pathway we recently discovered regulates mitochondrial function and cell survival, and treatments thereof.

Methods

Cultured mouse brain bEnd5 endothelial cells were treated with integrin, FAK or STAT3 inhibitors, FAK siRNA, as well as integrin and STAT3 activators. STAT3 null cells were transfected with mutant STAT3 plasmids. Outcome measures included oxygen consumption rate for mitochondrial bioenergetics, Western blotting for protein phosphorylation, mitochondrial membrane potential for mitochondrial integrity, ROS production, and cell counts.

Results

Vitronectin-dependent mitochondrial basal respiration, ATP production, and maximum reserve and respiratory capacities were suppressed within 4 h by RGD and αvβ3 integrin antagonist peptides. Conversely, integrin ligands vitronectin, laminin and fibronectin stimulated mitochondrial function. Pharmacological inhibition of FAK completely abolished mitochondrial function within 4 h while FAK siRNA treatments confirmed the specificity of FAK signaling. WT, but not S727A functionally dead mutant STAT3, rescued bioenergetics in cells made null for STAT3 using CRISPR-Cas9. STAT3 inhibition with stattic in whole cells rapidly reduced mitochondrial function and mitochondrial pS727-STAT3. Stattic treatment of isolated mitochondria did not reduce pS727 whereas more was detected upon phosphatase inhibition. This suggests that S727-STAT3 is activated in the cytoplasm and is short-lived upon translocation to the mitochondria. FAK inhibition reduced pS727-STAT3 within mitochondria and reduced mitochondrial function in a non-transcriptional manner, as shown by co-treatment with actinomycin. Treatment with the small molecule bryostatin-1 or hepatocyte growth factor (HGF), which indirectly activate S727-STAT3, preserved mitochondrial function during FAK inhibition, but failed in the presence of the STAT3 inhibitor. FAK inhibition induced loss of mitochondrial membrane potential, which was counteracted by bryostatin, and increased superoxide and hydrogen peroxide production. Bryostatin and HGF reduced the substantial cell death caused by FAK inhibition over a 24 h period.

Conclusion

These data suggest that extracellular matrix molecules promote STAT3-dependent mitochondrial function and cell survival through integrin-FAK signaling. We furthermore show a new treatment strategy for cell survival using S727-STAT3 activators.

The regulatory role of heparin on c-Met signaling in hepatocellular carcinoma cells

The role of heparin as an anticoagulant is well defined; however, its role in tumorigenesis and tumor progression is not clear yet. Some studies have shown that anticoagulant treatment in cancer patients improve overall survival, however, recent clinical trials have not shown a survival benefit in cancer patients receiving heparin treatment. In our previous studies we have shown the inhibitory effects of heparin on Hepatocyte Growth Factor (HGF)-induced invasion and migration in hepatocellular carcinoma (HCC) cells. In this study, we showed the differential effects of heparin on the behaviors of HCC cells based on the presence or absence of HGF. In the absence of HGF, heparin activated HGF/c-Met signaling and promoted motility and invasion in HCC cells. Heparin treatment led to c-Met receptor dimerization and activated c-Met signaling in an HGF independent manner. Heparin-induced c-Met activation increased migration and invasion through ERK1/2, early growth response factor 1 (EGR1) and Matrix Metalloproteinases (MMP) axis. Interestingly, heparin modestly decreased the proliferation of HCC cells by inhibiting activatory phosphorylation of Akt. The inhibition of c-Met signaling reversed heparin-induced increase in motility and invasion and, proliferation inhibition. Our study provides a new perspective into the role of heparin on c-Met signaling in HCC.

Probing conformational and functional states of human hepatocyte growth factor by a panel of monoclonal antibodies

HGF-Met signaling contributes to various biological events by controlling cell migration. Since the abnormal activation of Met receptor causes cancer progression, inhibitors such as neutralizing antibodies are regarded as promising therapeutics. HGF is secreted as a single-chain (sc) precursor and is processed by extracellular proteases to generate disulfide-bonded two-chain (tc) HGF. Although this proteolytic processing of HGF is necessary for its biological activity, exactly how the proteolysis leads to the conversion of HGF to the active form is still unclar due to the lack of structural information. In order to gain insights about this point, we generated 6 antibodies against HGF. All antibodies recognized different epitopes on the native HGF protein and showed distinct effects when tested in a cell-based HGF-Met signaling assay. They included one antibody (t1E4) that strongly blocks Met activation by tcHGF, as well as one antibody (t8E4) exclusively recognizing the active tcHGF but not inactive scHGF. Thus, a panel of anti-HGF antibodies suitable for probing the structural mechanism of HGF activation were obtained.