Met-related receptor tyrosine kinase Ron in tumor growth and metastasis

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

Molecular Mechanisms of Colorectal Liver Metastases

The liver is the most frequently target for metastasis among patients with colorectal cancer mainly because of the portal vein circulation that directly connects the colon and rectum with the liver. The liver tumor microenvironment consists of different cell types each with unique characteristics and functions that modulate the antigen recognition and immune system activation. Primary tumors from other sites "prime" the liver prior to the seeding of cancer cells, creating a pre-metastatic niche. Following invasion into the liver, four different phases are key to the development of liver metastases: a microvascular phase in which cancer cells infiltrate and become trapped in sinusoidal vessels; an extravascular, pre-angiogenic phase; an angiogenic phase that supplies oxygen and nutrients to cancer cells; and a growth phase in which metastatic cells multiply and enlarge to form detectable tumors. Exosomes carry proteins, lipids, as well as genetic information that can create a pre-metastatic niche in distant sites, including the liver. The complexity of angiogenic mechanisms and the exploitation of the vasculature in situ by cancer cells have limited the efficacy of currently available anti-angiogenic therapies. Delineating the molecular mechanisms implicated in colorectal liver metastases is crucial to understand and predict tumor progression; the development of distant metastases; and resistance to chemotherapy, immunotherapy, and targeted treatment.

Genetic Influences in Cancer-Associated Myositis

Idiopathic inflammatory myopathies (IIMs) comprise a heterogeneous group of rare immune-mediated disorders that primarily affect muscles but also lead to dysfunction in other organs. Five different clinical subphenotypes of IIM have been distinguished: dermatomyositis, polymyositis, inclusion body myositis, antisynthetase syndrome, and immune-mediated necrotizing myopathy. Excess mortality and morbidity associated with IIM are largely attributed to comorbidities, particularly cancer. The risk of malignancy is not equally distributed among IIM groups and is particularly high among patients with dermatomyositis. The cancer risk peaks around 3 years on either side of the IIM diagnosis and remains elevated even 10 years after the onset of the disease. Lung, colorectal, and ovarian neoplasms typically arise before the onset of IIM, whereas melanoma, cervical, oropharyngeal, and nonmelanoma skin cancers usually develop after IIM diagnosis. Given the close temporal proximity between IIM diagnosis and the emergence of malignancy, it has been proposed that IIM could be a consequence rather than a cause of cancer, a process known as a paramalignant phenomenon. Thus, a separate group of IIMs related to paramalignant phenomenon has been distinguished, known as cancer-associated myositis (CAM). Although the relationship between IIM and cancer is widely recognized, the pathophysiology of CAM remains elusive. Given that genetic factors play a role in the development of IIM, dissection of the molecular mechanisms shared between IIM and cancer presents an opportunity to examine the role of autoimmunity in cancer development and progression. In this review, the evidence supporting the contribution of genetics to CAM will be discussed.

Type I and II interferon signaling in colorectal cancer liver metastasis

Metastatic colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Traditional chemotherapy extended the lifespan of cancer patients by only a few months, but targeted therapies and immunotherapy prolonged survival and led to long-term remissions in some cases. Type I and II interferons have direct pro-apoptotic and anti-proliferative effects on cancer cells and stimulate anti-cancer immunity. As a result, interferon production by cells in the tumor microenvironment is in the spotlight of immunotherapies as it affects the responses of anti-cancer immune cells. However, promoting effects of interferons on colorectal cancer metastasis have also been reported. Here we summarize our knowledge about pro- and anti-metastatic effects of type I and II interferons in colorectal cancer liver metastasis and discuss possible therapeutic implications.

The Roles of Tumor-Associated Macrophages in Prostate Cancer

The morbidity of prostate cancer (PCa) is rising year by year, and it has become the primary cause of tumor-related mortality in males. It is widely accepted that macrophages account for 50% of the tumor mass in solid tumors and have emerged as a crucial participator in multiple stages of PCa, with the huge potential for further treatment. Oftentimes, tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) behave like M2-like phenotypes that modulate malignant hallmarks of tumor lesions, ranging from tumorigenesis to metastasis. Several clinical studies indicated that mean TAM density was higher in human PCa cores versus benign prostatic hyperplasia (BPH), and increased biopsy TAM density potentially predicts worse clinicopathological characteristics as well. Therefore, TAM represents a promising target for therapeutic intervention either alone or in combination with other strategies to halt the “vicious cycle,” thus improving oncological outcomes. Herein, we mainly focus on the fundamental aspects of TAMs in prostate adenocarcinoma, while reviewing the mechanisms responsible for macrophage recruitment and polarization, which has clinical translational implications for the exploitation of potentially effective therapies against TAMs.

NMR-based metabolomic analysis identifies RON-DEK-β-catenin dependent metabolic pathways and a gene signature that stratifies breast cancer patient survival

BACKGROUND

Advances in detection techniques and treatment have increased the diagnosis of breast cancer at early stages; however, recurrence occurs in all breast cancer subtypes, and both recurrent and de novo metastasis are typically treatment resistant. A growing body of evidence supports the notion that metabolic plasticity drives cancer recurrence. RON and DEK are proteins that promote cancer metastasis and synergize mechanistically to activate β-catenin, but the metabolic consequences are unknown.

METHODS

To ascertain RON-DEK-β-catenin dependent metabolic pathways, we utilized an NMR-based metabolomics approach to determine steady state levels of metabolites. We also interrogated altered metabolic pathway gene expression for prognostic capacity in breast cancer patient relapse-free and distant metastasis-free survival and discover a metabolic signature that is likely associated with recurrence.

RESULTS

RON-DEK-β-catenin loss showed a consistent metabolite regulation of succinate and phosphocreatine. Consistent metabolite alterations between RON and DEK loss (but not β-catenin) were found in media glucose consumption, lactate secretion, acetate secretion, and intracellular glutamine and glutathione levels. Consistent metabolite alterations between RON and β-catenin loss (and not DEK) were found only in intracellular lactate levels. Further pathway hits include β-catenin include glycolysis, glycosylation, TCA cycle/anaplerosis, NAD+ production, and creatine dynamics. Genes in these pathways epistatic to RON-DEK-β-catenin were used to define a gene signature that prognosticates breast cancer patient survival and response to chemotherapy.

CONCLUSIONS

The RON-DEK-β-catenin axis regulates the numerous metabolic pathways with significant associations to breast cancer patient outcomes.

Identification of (S)-1-(2-(2,4-difluorophenyl)-4-oxothiazolidin-3-yl)-3-(4-((7-(3-(4-ethylpiperazin-1-yl)propoxy)-6-methoxyquinolin-4-yl)oxy)-3,5-difluorophenyl)urea as a potential anti-colorectal cancer agent

In our previous study, 1-(2-(2,6-difluorophenyl)-4-oxothiazolidin-3-yl)-3-(4-((7-(3-(4-ethylpiperazin-1-yl)propoxy)-6-methoxyquinolin-4-yl)oxy)-3,5-difluorophenyl)urea (1) was obtained as a potent tyrosine kinase inhibitor. Further structural optimization was performed in this investigation, and a series of novel quinoline derivates were designed, synthesized and evaluated for their biological activity. Among them, compound 8m possessed nanomolar c-Met and Ron inhibitory activity, with IC₅₀ values of 4.32 nM and 2.39 nM, respectively. Kinase profile study demonstrated that it could also inhibit ABL, PDGFRβ, AXL, RET, and FLT3 with submicromolar potency. It also exhibited moderate to excellent cytotoxic activity against different types of human cancer cell lines, especially against COLO 205 cells (IC₅₀ = 0.035 μM) which was remarkably superior to that of Cabozantinib (IC₅₀ = 6.6 μM) and Fruquintinib (IC₅₀ > 10.0 μM). Compared to ( ± )-8m, isomer (S)-8m and (R)-8m showed similar kinase inhibitory activity against c-Met/RON and in vitro anticancer activity against COLO 205 cells. Differently, compound (S)-8m showed an over 238-fold selectivity toward COLO 205 (IC₅₀ = 0.042 μM) cells to FHC cells (IC₅₀ > 10.0 μM), which indicated its low cytotoxicity against human normal tissue cells. Flow cytometry study demonstrated that compound (S)-8m could significantly induce apoptosis in COLO 205 cells in a dose-dependent manner. Cell cycle arrest assays showed that compound (S)-8m could not arrest the cell-cycle progression due to the massive dead cells.

Plasma membrane proteoglycans syndecan-2 and syndecan-4 engage with EGFR and RON kinase to sustain carcinoma cell cycle progression

Epidermal growth factor receptor (EGFR) is a causal factor in carcinoma, yet many carcinoma patients are resistant to EGFR inhibitors. Potential insight into this resistance stems from prior work that showed EGFR in normal epithelial cells docks to the extracellular domain of the plasma membrane proteoglycan syndecan-4 (Sdc4) engaged with α3β1 and α6β4 integrins. We now report that this receptor complex is modified by the recruitment of syndecan-2 (Sdc2), the Recepteur d'Origine Nantais (RON) tyrosine kinase, and the cellular signaling mediator Abelson murine leukemia viral oncogene homolog 1 (ABL1) in triple-negative breast carcinoma and head and neck squamous cell carcinoma, where it contributes to EGFR kinase-independent proliferation. Treatment with a peptide mimetic of the EGFR docking site in the extracellular domain of Sdc4 (called SSTNEGFR) disrupts the entire complex and causes a rapid, global arrest of the cell cycle. Normal epithelial cells do not recruit these additional receptors to the adhesion mechanism and are not arrested by SSTNEGFR. Although EGFR docking with Sdc4 in the tumor cells is required, cell cycle progression does not depend on EGFR kinase. Instead, progression depends on RON kinase, activated by its incorporation into the complex. RON activates ABL1, which suppresses p38 mitogen-activated protein kinase and prevents a p38-mediated signal that would otherwise arrest the cell cycle. These findings add to the growing list of receptor tyrosine kinases that support tumorigenesis when activated by their association with syndecans at sites of matrix adhesion and identify new potential targets for cancer therapy.

RON (MST1R) and HGFL (MST1) Co-Overexpression Supports Breast Tumorigenesis through Autocrine and Paracrine Cellular Crosstalk

BACKGROUND

Aberrant RON signaling is present in numerous cancers including breast cancer. Evidence suggests that the ligand, hepatocyte growth factor-like (HGFL), is also overexpressed in breast cancer. RON (MST1R) and HGFL (MST1) genes are located on human chromosome 3 and mouse chromosome 9 respectively and are found near each other in both species. Based on co-expression patterns, we posited that RON and HGFL are co-regulated and that coordinate upregulation drives aggressive tumorigenesis.

METHODS

Mouse models were used to establish the functional significance of RON and HGFL co-overexpression on the activation of tumor cells and tumor-associated macrophages in breast cancer. TCGA and METABRIC gene expression and alteration data were used to query the relationships between MST1R and MST1 in breast cancer.

RESULTS

In tumor models, physiologic sources of HGFL modestly improve Arginase-1+ (M2) macrophage recruitment to the tumor proper. Tumor-cell produced HGFL functions in autocrine to sustain tumor cell RON activation and MAPK-dependent secretion of chemotactic factors and in paracrine to activate RON on macrophages and to promote breast cancer stem cell self-renewal. In silico analyses support that RON and HGFL are co-expressed across virtually all cancer types including breast cancer and that common genomic alterations do not appear to be drivers of RON/HGFL co-overexpression.

CONCLUSIONS

Co-overexpression of RON and HGFL in breast cancer cells (augmented by physiologic sources of HGFL) promotes tumorigenesis through autocrine-mediated RON activation/RON-dependent secretome changes and paracrine activation of macrophage RON to promote breast cancer stem cell self-renewal.

Macrophage-mediated RON signaling supports breast cancer growth and progression through modulation of IL-35

Tumor associated macrophages (TAMs) play a major role in regulating mammary tumor growth and in directing the responses of tumor infiltrating leukocytes in the microenvironment. However, macrophage-specific mechanisms regulating the interactions of macrophages with tumor cells and other leukocytes that support tumor progression have not been extensively studied. In this study, we show that the activation of the RON receptor tyrosine kinase signaling pathway specifically in macrophages supports breast cancer growth and metastasis. Using clinically relevant murine models of breast cancer, we demonstrate that loss of macrophage RON expression results in decreases in mammary tumor cell proliferation, survival, cancer stem cell self-renewal, and metastasis. Macrophage RON signaling modulates these phenotypes via direct effects on the tumor proper and indirectly by regulating leukocyte recruitment including macrophages, T-cells, and B-cells in the mammary tumor microenvironment. We further show that macrophage RON expression regulates the macrophage secretome including IL-35 and other immunosuppressive factors. Overall, our studies implicate activation of RON signaling in macrophages as a key player in supporting a thriving mammary pro-tumor microenvironment through novel mechanisms including the augmentation of tumor cell properties through IL-35.

Receptor Tyrosine Kinases and Their Signaling Pathways as Therapeutic Targets of Curcumin in Cancer

Receptor tyrosine kinases (RTKs) are transmembrane cell-surface proteins that act as signal transducers. They regulate essential cellular processes like proliferation, apoptosis, differentiation and metabolism. RTK alteration occurs in a broad spectrum of cancers, emphasising its crucial role in cancer progression and as a suitable therapeutic target. The use of small molecule RTK inhibitors however, has been crippled by the emergence of resistance, highlighting the need for a pleiotropic anti-cancer agent that can replace or be used in combination with existing pharmacological agents to enhance treatment efficacy. Curcumin is an attractive therapeutic agent mainly due to its potent anti-cancer effects, extensive range of targets and minimal toxicity. Out of the numerous documented targets of curcumin, RTKs appear to be one of the main nodes of curcumin-mediated inhibition. Many studies have found that curcumin influences RTK activation and their downstream signaling pathways resulting in increased apoptosis, decreased proliferation and decreased migration in cancer both in vitro and in vivo. This review focused on how curcumin exhibits anti-cancer effects through inhibition of RTKs and downstream signaling pathways like the MAPK, PI3K/Akt, JAK/STAT, and NF-κB pathways. Combination studies of curcumin and RTK inhibitors were also analysed with emphasis on their common molecular targets.

CCL20 induces colorectal cancer neoplastic epithelial cell proliferation, migration, and further CCL20 production through autocrine HGF-c-Met and MSP-MSPR signaling pathways

CCL20-CCR6 interactions promote colorectal cancer through direct effects on neoplastic epithelial cells and through modulating the tumor microenvironment. The mechanism of these effects on neoplastic epithelial cells is poorly understood. This study demonstrates that CCL20 induces secretion of hepatocyte growth factor (HGF) and phosphorylation of HGF’s cognate receptor c-Met in HT29 and HCT116 colorectal cancer cell lines both in concentration- and time-dependent manners. Similar to CCL20, HGF induces migration, autofeedback CCL20 secretion, and ERK1/2 phosphorylation in the colon cancer cells. CCL20-dependent ERK1/2 phosphorylation is blocked by HGF inhibition, and CCL20-dependent migration and CCL20 secretion are blocked by inhibition of HGF or ERK. Interestingly, unlike CCL20, HGF does not induce proliferation of colon cancer cells, and CCL20-dependent cell proliferation is not blocked by direct HGF inhibition. CCL20-dependent proliferation, however, is blocked by the multi-tyrosine kinase inhibitor crizotinib. Exploring this effect, it was found that CCL20 also induces production of MSP and phosphorylation of MSP’s receptor MSPR by the colorectal cancer cells. CCL20-dependent cell proliferation is inhibited by directly blocking MSP-MSPR interactions. Thus, CCL20-mediated migration and CCL20 secretion are regulated through a pathway involving HGF, c-Met, and ERK, while CCL20-mediated proliferation is instead regulated through MSP and its receptor MSPR.

RON Mediates Tumor-Promoting Effects in Endometrial Adenocarcinoma

Endometrial adenocarcinoma is one of the most prevalent female reproductive tract cancers in the world, and the development of effective treatment is still the main goal of its current research. Epithelial-mesenchymal transition (EMT) plays a significant part in the occurrence and development of epithelial carcinoma, including endometrial adenocarcinoma. Recepteur d'origine nantais (RON) induces EMT and promotes proliferation, migration, and invasion in various epithelial-derived cancers, but its role in endometrial adenocarcinoma is still poorly studied. The purpose of this study is to verify the overexpression of RON in endometrial adenocarcinoma and to explore its specific roles. RON expression in tumor lesions was verified by immunohistochemical staining, HEC-1B cells were used to construct stable cell lines with RON overexpression or knockdown to investigate the effects of RON on the function of endometrial adenocarcinoma cells, and xenotransplantation experiment was carried out in nude mice to explore the effect of RON on the growth of endometrial adenocarcinoma in vivo. This study revealed that RON could promote the proliferation, migration, and invasion of HEC-1B cells and induce EMT, and these effects were regulated through the Smad pathway. RON overexpression could promote growth of endometrial adenocarcinoma cells in nude mice, while its inhibitor BMS777607 could restrict this role. RON played an important role in endometrial adenocarcinoma and had a potential to become a new therapeutic target for endometrial adenocarcinoma.

Pondering the mechanism of receptor tyrosine kinase activation: The case for ligand-specific dimer microstate ensembles

Receptor tyrosine kinases (RTKs) are single-pass membrane proteins that regulate cell growth, differentiation, motility, and metabolism. Here, we review recent advancements in RTK structure determination and in the understanding of RTK activation. We argue that further progress in the field will necessitate new ways of thinking, and we introduce the concept that RTK dimers explore ensembles of microstates, each characterized by different kinase domain dimer conformations, but the same extracellular domain dimer structure. Many microstates are phosphorylation-competent and ensure the phosphorylation of one specific tyrosine. The prevalence of each microstate correlates with its stability. A switch in ligand will lead to a switch in the extracellular domain configuration and to a subsequent switch in the ensemble of microstates. This model can explain how different ligands produce specific phosphorylation patterns, how receptor overexpression leads to enhanced signaling even in the absence of activating ligands, and why RTK kinase domain structures have remained unresolved in cryogenic electron microscopy studies.

RON in hepatobiliary and pancreatic cancers: Pathogenesis and potential therapeutic targets

The receptor protein tyrosine kinase RON belongs to the c-MET proto-oncogene family. Research has shown that RON has a role in cancer pathogenesis, which places RON on the frontline of the development of novel cancer therapeutic strategies. Hepatobiliary and pancreatic (HBP) cancers have a poor prognosis, being reported as having higher rates of cancer-related death. Therefore, to combat these malignant diseases, the mechanism underlying the aberrant expression and signaling of RON in HBP cancer pathogenesis, and the development of RON as a drug target for therapeutic intervention should be investigated. Abnormal RON expression and signaling have been identified in HBP cancers, and also act as tumorigenic determinants for HBP cancer malignant behaviors. In addition, RON is emerging as an important mediator of the clinical prognosis of HBP cancers. Thus, not only is RON significant in HBP cancers, but also RON-targeted therapeutics could be developed to treat these cancers, for example, therapeutic monoclonal antibodies and small-molecule inhibitors. Among them, antibody-drug conjugates have become increasingly popular in current research and their potential as novel anti-cancer biotherapeutics will be determined in future clinical trials.

Liver Immune Microenvironment and Metastasis from Colorectal Cancer-Pathogenesis and Therapeutic Perspectives

A drastic difference exists between the 5-year survival rates of colorectal cancer patients with localized cancer and distal organ metastasis. The liver is the most favorable organ for cancer metastases from the colorectum. Beyond the liver-colon anatomic relationship, emerging evidence highlights the impact of liver immune microenvironment on colorectal liver metastasis. Prior to cancer cell dissemination, hepatocytes secrete multiple factors to recruit or activate immune cells and stromal cells in the liver to form a favorable premetastatic niche. The liver-resident cells including Kupffer cells, hepatic stellate cells, and liver-sinusoidal endothelial cells are co-opted by the recruited cells, such as myeloid-derived suppressor cells and tumor-associated macrophages, to establish an immunosuppressive liver microenvironment suitable for tumor cell colonization and outgrowth. Current treatments including radical surgery, systemic therapy, and localized therapy have only achieved good clinical outcomes in a minority of colorectal cancer patients with liver metastasis, which is further hampered by high recurrence rate. Better understanding of the mechanisms governing the metastasis-prone liver immune microenvironment should open new immuno-oncology avenues for liver metastasis intervention.

Tumor cell intrinsic RON signaling suppresses innate immune responses in breast cancer through inhibition of IRAK4 signaling

Increasing evidence suggests that cancer cells require both alterations in intrinsic cellular processes and the tumor microenvironment for tumor establishment, growth, and progression to metastatic disease. Despite this, knowledge of tumor-cell intrinsic molecular mechanisms controlling both tumor cell processes as well as the tumor microenvironment is limited. In this study, we provide evidence demonstrating the novel role of RON signaling in regulating breast cancer initiation, progression, and metastasis through modulation of tumor cell intrinsic processes and the tumor microenvironment. Using clinically relevant models of breast cancer, we show that RON signaling in the mammary epithelial tumor cells promotes tumor cell survival and proliferation as well as an immunopermissive microenvironment associated with decreased M1 macrophage, natural killer (NK) cell, and CD8+ T cell recruitment. Moreover, we demonstrate that RON signaling supports these phenotypes through novel mechanisms involving suppression of IRAK4 signaling and inhibition of type I Interferons. Our studies indicate that activation of RON signaling within breast cancer cells promotes tumor cell intrinsic growth and immune evasion which support breast cancer progression and highlight the role of targeting RON signaling as a potential therapeutic strategy against breast cancer.

Perspective in Alternative Splicing Coupled to Nonsense-Mediated mRNA Decay

Alternative splicing (AS) of precursor mRNA (pre-mRNA) is a cellular post-transcriptional process that generates protein isoform diversity. Nonsense-mediated RNA decay (NMD) is an mRNA surveillance pathway that recognizes and selectively degrades transcripts containing premature translation-termination codons (PTCs), thereby preventing the production of truncated proteins. Nevertheless, NMD also fine-tunes the gene expression of physiological mRNAs encoding full-length proteins. Interestingly, around one third of all AS events results in PTC-containing transcripts that undergo NMD. Numerous studies have reported a coordinated action between AS and NMD, in order to regulate the expression of several genes, especially those coding for RNA-binding proteins (RBPs). This coupling of AS to NMD (AS-NMD) is considered a gene expression tool that controls the ratio of productive to unproductive mRNA isoforms, ultimately degrading PTC-containing non-functional mRNAs. In this review, we focus on the mechanisms underlying AS-NMD, and how this regulatory process is able to control the homeostatic expression of numerous RBPs, including splicing factors, through auto- and cross-regulatory feedback loops. Furthermore, we discuss the importance of AS-NMD in the regulation of biological processes, such as cell differentiation. Finally, we analyze interesting recent data on the relevance of AS-NMD to human health, covering its potential roles in cancer and other disorders.

Small Molecular Gemcitabine Prodrugs for Cancer Therapy

Gemcitabine as a pyrimidine nucleoside analog anticancer drug has high efficacy for a broad spectrum of solid tumors. Gemcitabine is activated within tumor cells by sequential phosphorylation carried out by deoxycytidine kinase to mono-, di-, and triphosphate nucleotides with the last one as the active form. But the instability, drug resistance and toxicity severely limited its utilization in clinics. In the field of medicinal chemistry, prodrugs have proven to be a very effective means for elevating drug stability and decrease undesirable side effects including the nucleoside anticancer drug such as gemcitabine. Many works have been accomplished in design and synthesis of gemcitabine prodrugs, majority of which were summarized in this review.

Hepatocyte Growth Factor and Macrophage-stimulating Protein "Hinge" Analogs to Treat Pancreatic Cancer

Pancreatic cancer (PC) ranks twelfth in frequency of diagnosis but is the fourth leading cause of cancer related deaths with a 5 year survival rate of less than 7 percent. This poor prognosis occurs because the early stages of PC are often asymptomatic. Over-expression of several growth factors, most notably vascular endothelial growth factor (VEGF), has been implicated in PC resulting in dysfunctional signal transduction pathways and the facilitation of tumor growth, invasion and metastasis. Hepatocyte growth factor (HGF) acts via the Met receptor and has also received research attention with ongoing efforts to develop treatments to block the Met receptor and its signal transduction pathways. Macrophage-stimulating protein (MSP), and its receptor Ron, is also recognized as important in the etiology of PC but is less well studied. Although the angiotensin II (AngII)/AT1 receptor system is best known for mediating blood pressure and body water/electrolyte balance, it also facilitates tumor vascularization and growth by stimulating the expression of VEGF. A metabolite of AngII, angiotensin IV (AngIV) has sequence homology with the "hinge regions" of HGF and MSP, key structures in the growth factor dimerization processes necessary for Met and Ron receptor activation. We have developed AngIV-based analogs designed to block dimerization of HGF and MSP and thus receptor activation. Norleual has shown promise as tested utilizing PC cell cultures. Results indicate that cell migration, invasion, and pro-survival functions were suppressed by this analog and tumor growth was significantly inhibited in an orthotopic PC mouse model.

Prostate Epithelial RON Signaling Promotes M2 Macrophage Activation to Drive Prostate Tumor Growth and Progression

Effective treatment of advanced prostate cancer persists as a significant clinical need as only 30% of patients with distant disease survive to 5 years after diagnosis. Targeting signaling and tumor cell-immune cell interactions in the tumor microenvironment has led to the development of powerful immunotherapeutic agents, however, the prostate tumor milieu remains impermeable to these strategies highlighting the need for novel therapeutic targets. In this study, we provide compelling evidence to support the role of the RON receptor tyrosine kinase as a major regulator of macrophages in the prostate tumor microenvironment. We show that loss of RON selectively in prostate epithelial cells leads to significantly reduced prostate tumor growth and metastasis and is associated with increased intratumor infiltration of macrophages. We further demonstrate that prostate epithelial RON loss induces transcriptional reprogramming of macrophages to support expression of classical M1 markers and suppress expression of alternative M2 markers. Interestingly, our results show epithelial RON activation drives upregulation of RON expression in macrophages as a positive feed-forward mechanism to support prostate tumor growth. Using 3D coculture assays, we provide additional evidence that epithelial RON expression coordinates interactions between prostate tumor cells and macrophages to promote macrophage-mediated tumor cell growth. Taken together, our results suggest that RON receptor signaling in prostate tumor cells directs the functions of macrophages in the prostate tumor microenvironment to promote prostate cancer. IMPLICATIONS: Epithelial RON is a novel immunotherapeutic target that is responsible for directing the macrophage antitumor immune response to support prostate tumor growth and progression.

MST1R (RON) expression is a novel prognostic biomarker for metastatic progression in breast cancer patients

PURPOSE

This study evaluates the prognostic significance of MST1R (RON) expression in breast cancer with respect to disease progression, long-term survival, subtype, and association with conventional prognostic factors.

METHODS

The approach includes interrogation of survival and tumor staging with paired MST1R RNA expression from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets. Protein expression evaluation was performed using immunohistochemistry (IHC) staining of MST1R on breast cancer tissue samples from the Cancer Diagnosis Program Breast Cancer Progression tissue microarray and locally obtained breast tumor tissue samples analyzed with paired survival, metastasis, and subtype.

RESULTS

Data from TCGA (n = 774) show poorer relapse-free survival (RFS) in patients with high MST1R expression (P = 0.32) and no difference in MST1R expression based on tumor stage (P = 0.77) or nodal status (P = 0.94). Patients in the GEO-derived Kaplan-Meier Plotter microarray dataset demonstrate the association of MST1R and poorer overall survival (n = 1402, P = 0.018) and RFS in patients receiving chemotherapy (n = 798, P = 0.041). Patients with high MST1R expression display worse overall survival (P = 0.01) and receiver operator characteristic (ROC) analysis demonstrate the predictive capacity of increased MST1R with early death (P = 0.0017) in IHC-stained samples. Paired IHC-stained breast tumor samples from the primary versus metastatic site show MST1R expression is associated with metastatic progression (P = 0.032), and ROC analysis supports the predictive capacity of MST1R in metastatic progression (P = 0.031). No associations of MST1R with estrogen receptor (ER), progesterone receptor (PR), both ER and PR, HER2 positivity, or triple-negativity were found (P = 0.386, P = 0.766, P = 0.746, P = 0.457, P = 0.947, respectively).

CONCLUSIONS

MST1R expression has prognostic value in breast cancer with respect to survival and metastatic progression. MST1R expression is not associated with tumor stage, nodal status, or subtype.

Liver Tropism in Cancer: The Hepatic Metastatic Niche

The liver is the largest organ in the human body and is prone for cancer metastasis. Although the metastatic pattern can differ depending on the cancer type, the liver is the organ to which cancer cells most frequently metastasize for the majority of prevalent malignancies. The liver is unique in several aspects: the vascular structure is highly permeable and has unparalleled dual blood connectivity, and the hepatic tissue microenvironment presents a natural soil for the seeding of disseminated tumor cells. Although 70% of the liver is composed of the parenchymal hepatocytes, the remaining 30% is composed of nonparenchymal cells including Kupffer cells, liver sinusoidal endothelial cells, and hepatic stellate cells. Recent discoveries show that both the parenchymal and the nonparenchymal cells can modulate each step of the hepatic metastatic cascade, including the initial seeding and colonization as well as the decision to undergo dormancy versus outgrowth. Thus, a better understanding of the molecular mechanisms orchestrating the formation of a hospitable hepatic metastatic niche and the identification of the drivers supporting this process is critical for the development of better therapies to stop or at least decrease liver metastasis. The focus of this perspective is on the bidirectional interactions between the disseminated cancer cells and the unique hepatic metastatic niche.

The transition model of RTK activation: A quantitative framework for understanding RTK signaling and RTK modulator activity

Here, we discuss the transition model of receptor tyrosine kinase (RTK) activation, which is derived from biophysical investigations of RTK interactions and signaling. The model postulates that (1) RTKs can interact laterally to form dimers even in the absence of ligand, (2) different unliganded RTK dimers have different stabilities, (3) ligand binding stabilizes the RTK dimers, and (4) ligand binding causes structural changes in the RTK dimer. The model is grounded in the principles of physical chemistry and provides a framework to understand RTK activity and to make predictions in quantitative terms. It can guide basic research aimed at uncovering the mechanism of RTK activation and, in the long run, can empower the search for modulators of RTK function.

Comparative characterization of the HGF/Met and MSP/Ron systems in primary pancreatic adenocarcinoma

Pancreatic cancer is an aggressive disease with a poor prognosis for which current standard chemotherapeutic treatments offer little survival benefit. Receptor tyrosine kinases (RTK)s have garnered interest as therapeutic targets to augment or replace standard chemotherapeutic treatments because of their ability to promote cell growth, migration, and survival in various cancers. Met and Ron, which are homologous RTKs activated by the ligands hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP), respectively, are over-activated and display synergistic malignant effects in several cancers. Despite the homology between Met and Ron, studies that have directly compared the functional outcomes of these systems in any context are limited. To address this, we sought to determine if the HGF/Met and MSP/Ron systems produce overlapping or divergent contributions towards a malignant phenotype by performing a characterization of MSP and HGF driven signaling, behavioral, and transcriptomic responses in a primary pancreatic adenocarcinoma (PAAD) cell line in vitro. The impact of dual Met and Ron expression signatures on the overall survival of PAAD patients was also assessed. We found HGF and MSP both encouraged PAAD cell migration, but only HGF increased proliferation. RNA sequencing revealed that the transcriptomic effects of MSP mimicked a narrow subset of the responses induced by HGF. Analysis of clinical data indicated that the strong prognostic value of Met expression in primary PAAD does not appear to be modulated by Ron expression. The relatively reduced magnitude of MSP-dependent effects on primary PAAD cells are consistent with the limited prognostic value of Ron expression in this cancer when compared to Met. Although HGF and MSP produced a differing breadth of responses in vitro, overlapping pro-cancer signaling, behavioral, and transcriptional effects still point to a potential role for the MSP/Ron system in pancreatic cancer.

Therapeutic efficacy of a novel humanized antibody-drug conjugate recognizing plexin-semaphorin-integrin domain in the RON receptor for targeted cancer therapy

Background

Antibody-drug conjugates (ADCs) targeting the RON receptor, a tumorigenic factor contributing to cancer malignancy, has been considered as a novel strategy for cancer therapy. Here we describe a humanized antibody recognizing the RON plexin-semaphorin-integrin (PSI) domain with increased drug delivery capability for potential clinical application.

Method

Monoclonal antibody PCM5B14 specific to the human and monkey RON PSI domain was generated and characterized by various immunological methods. Humanized antibody H5B14 was created by grafting PCM5B14 complementarity-determining regions into human IgG1/κ acceptor frameworks and conjugated with monomethyl auristatin E and duocarmycin to form two H5B14-based ADCs. Stability of H5B14-based ADCs in human plasma was measured using hydrophobic interaction chromatography. Various biochemical and biological assays were used to determine ADC- regulated RON internalization, cell viability, spheroid formation, and death of cancer stem-like cells. Efficacies of H5B14-based ADCs in vivo were validated using tumor xenograft models. Maximal tolerated doses of H5B14-based ADCs were established in mice.

Results

H5B14 was highly specific to the human RON PSI domain and superior over other anti-RON ADCs in induction of RON internalization in various cancer cell lines tested. H5B14-based ADCS had a drug to antibody ratio of ~ 3.70:1 and were stable in human plasma with a minimal dissociation within a 10-day period. Functionally, H5B14-mediated drug delivery decreased cell viability at early stages with an average IC₅₀ at ~ 20 nM in multiple cancer cell lines examined. H5B14-based ADCs also inhibited spheroid formation and caused death of cancer stem-like cells with RON⁺/CD44⁺/ESA⁺ phenotypes. In vivo, H5B14-based ADCs in a single injection inhibited tumor xenograft growth mediated by multiple cancer cell lines. Tumoristatic concentrations calculated from xenograft tumor models were in the range of 0.63 to 2.0 mg/kg bodyweight. Significantly, H5B14-based ADCs were capable of eradicating tumors at variable levels across multiple xenograft models regardless their malignant statuses. Toxicologically, H5B14-based ADCs were well tolerated in mice up to 60 mg/kg.

Conclusion

H5B14-based ADCs targeting the RON PSI domain are superior in inducing RON internalization, leading to robust drug delivery and overall inhibition and eradication of tumors in multiple xenograft models. These findings warrant H5B14-based ADCs for clinical trials in the future.

Therapeutic anti-cancer activity of antibodies targeting sulfhydryl bond constrained epitopes on unglycosylated RON receptor tyrosine kinase

Recepteur d'origine nantais (RON) receptor tyrosine kinase (RTK) and its ligand, serum macrophage-stimulating protein (MSP), are well-established oncogenic drivers for tumorigenesis and metastasis. RON is often found to be alternatively spliced resulting in various isoforms that are constitutively active. RON is therefore an attractive target for cancer therapeutics, including small molecular inhibitors and monoclonal antibodies. While small molecule inhibitors of RON may inhibit other protein kinases including the highly similar MET kinase, monoclonal antibodies targeting RON are more specific, potentially inducing fewer side effects. Although anti-RON monoclonal antibody therapies have been developed and tested in clinical trials, they were met with limited success. Cancer cells have been associated with aberrant glycosylation mechanisms. Notably for RON, the loss of N-bisected glycosylation is a direct cause for tumorigenesis and poorer prognosis in cancer patients. Particularly in gastric cancer, aberrant RON glycosylation augments RON activation. Here, we present a novel panel of monoclonal antibodies which potentially widens the specific targeting of not only the glycosylated RON, but also unglycosylated and aberrantly glycosylated RON. Our antibodies can bind strongly to deglycosylated RON from tunicamycin treated cells, recognise RON in IHC/IF and possess superior therapeutic efficacy in RON expressing xenograft tumours. Our most potent antibody in xenograft assays, is directed to the RON alpha chain and targets a sulfhydryl bond constrained epitope that appears to be cryptic in the crystal structure. This establishes the paradigm that such constrained and cryptic epitopes represent good targets for therapeutic antibodies.

The RTK Interactome: Overview and Perspective on RTK Heterointeractions

Receptor tyrosine kinases (RTKs) play important roles in cell growth, motility, differentiation, and survival. These single-pass membrane proteins are grouped into subfamilies based on the similarity of their extracellular domains. They are generally thought to be activated by ligand binding, which promotes homodimerization and then autophosphorylation in trans. However, RTK interactions are more complicated, as RTKs can interact in the absence of ligand and heterodimerize within and across subfamilies. Here, we review the known cross-subfamily RTK heterointeractions and their possible biological implications, as well as the methodologies which have been used to study them. Moreover, we demonstrate how thermodynamic models can be used to study RTKs and to explain many of the complicated biological effects which have been described in the literature. Finally, we discuss the concept of the RTK interactome: a putative, extensive network of interactions between the RTKs. This RTK interactome can produce unique signaling outputs; can amplify, inhibit, and modify signaling; and can allow for signaling backups. The existence of the RTK interactome could provide an explanation for the irreproducibility of experimental data from different studies and for the failure of some RTK inhibitors to produce the desired therapeutic effects. We argue that a deeper knowledge of RTK interactome thermodynamics can lead to a better understanding of fundamental RTK signaling processes in health and disease. We further argue that there is a need for quantitative, thermodynamic studies that probe the strengths of the interactions between RTKs and their ligands and between different RTKs.

Norleual, a hepatocyte growth factor and macrophage stimulating protein dual antagonist, increases pancreatic cancer sensitivity to gemcitabine

Pancreatic cancer is a leading cause of cancer deaths in the USA and is characterized by an exceptionally poor long-term survival rate compared with other major cancers. The hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP) growth factor systems are frequently over-activated in pancreatic cancer and significantly contribute to cancer progression, metastasis, and chemotherapeutic resistance. Small molecules homologous to the 'hinge' region of HGF, which participates in its dimerization and activation, had been developed and shown to bind HGF with high affinity, antagonize HGF's actions, and possess anticancer activity. Encouraged by sequence homology between HGF's hinge region and a similar sequence in MSP, our laboratory previously investigated and determined that these same antagonists could also block MSP-dependent cellular responses. Thus, the purpose of this study was to establish that the dual HGF/MSP antagonist Norleual could inhibit the prosurvival activity imparted by both HGF and MSP to pancreatic cancer cells in vitro, and to determine whether this effect translated into an improved chemotherapeutic impact for gemcitabine when delivered in combination in a human pancreatic cancer xenograft model. Our results demonstrate that Norleual does indeed suppress HGF's and MSP's prosurvival effects as well as sensitizing pancreatic cancer cells to gemcitabine in vitro. Most importantly, treatment with Norleual in combination with gemcitabine markedly inhibited in-vivo tumor growth beyond the suppression observed with gemcitabine alone. These results suggest that dual functional HGF/MSP antagonists like Norleual warrant further development and may offer an improved therapeutic outcome for pancreatic cancer patients.

Recent progress on inhibitors of the type II transmembrane serine proteases, hepsin, matriptase and matriptase-2

Members of the type II transmembrane serine proteases (TTSP) family play a vital role in cell growth and development but many are also implicated in disease. Two of the well-studied TTSPs, matriptase and hepsin proteolytically process multiple protein substrates such as the inactive single-chain zymogens pro-HGF and pro-macrophage stimulating protein into the active heterodimeric forms, HGF and macrophage stimulating protein. These two proteases also have many other substrates which are associated with cancer and tumor progression. Another related TTSP, matriptase-2 is expressed in the liver and functions by regulating iron homoeostasis through the cleavage of hemojuvelin and thus is implicated in iron overload diseases. In the present review, we will discuss inhibitor design strategy and Structure activity relationships of TTSP inhibitors, which have been reported in the literature.

MSP-RON Signaling Is Activated in the Transition From Pancreatic Intraepithelial Neoplasia (PanIN) to Pancreatic Ductal Adenocarcinoma (PDAC)

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest epithelial malignancies and remains difficult to treat. Pancreatic intraepithelial neoplasias (PanINs) represent the majority of the pre-cancer lesions in the pancreas. The PDAC microenvironment consists of activated pancreatic stellate cells (PSCs) and immune cells, which are thought to contribute to neoplastic transformation. However, the signaling events involved in driving the transition from the neoplastic precursor to the more advanced and aggressive forms in the pancreas are not well understood. Recepteur d’Origine Nantais (RON) is a c-MET family receptor tyrosine kinase that is implicated in playing a role in cell proliferation, migration and other aspects of tumorigenesis. Macrophage stimulating protein (MSP) is the ligand for RON and becomes activated upon proteolytic cleavage by matriptase (also known as ST14), a type II transmembrane serine protease. In the current study, by immunohistochemistry (IHC) analysis of human pancreatic tissues, we found that the expression levels MSP and matriptase are drastically increased during the transition from the preneoplastic PanIN stages to the more advanced and aggressive PDAC. Moreover, RON is highly expressed in both PDAC and in cancer-associated stellate cells. In contrast, MSP, RON, and matriptase are expressed at low levels, if any, in normal pancreas. Our study underscores an emerging role of MSP-RON autocrine and paracrine signaling events in driving malignant progression in the pancreas.

Expression of the Short Form of RON/STK in Feline Mammary Carcinoma

RON is a tyrosine kinase receptor activated by the macrophage-stimulating protein (MSP) ligand that is overexpressed in human breast cancer. In humans, RON protein can be present in different isoforms, and the most studied isoform is represented by the short form of RON ( sf-RON), which is generated by an alternative promoter located in intron 10 of the RON complementary DNA (cDNA). It plays an important role in breast cancer progression. Considering the many similarities between feline mammary carcinoma (FMC) and human breast cancer, the aim of this study was to investigate the expression of both RON and MSP in FMCs and to identify the presence of the sf-RON transcript. Tissue samples of spontaneous mammary tumors were collected from 60 queens (10 benign lesions, 50 carcinomas). All of the samples were tested for RON and MSP expression by immunohistochemistry; moreover, RNA was extracted from paraffin-embedded tissue samples, and the cDNA was tested by reverse transcription-polymerase chain reaction (RT-PCR) to identify the presence of sf-RON. Immunohistochemistry detected the expression of RON and MSP in 34 of 50 (68%) and 29 of 50 (58%) FMCs, respectively. RT-PCR revealed the presence of the short-form in 18 of 47 (38%) FMCs. This form originates, as in humans, from an alternative promoter (P2), and it codes for the proper feline short form ( sf-RON). sf-RON expression was associated with poorly differentiated tumors and with a shorter disease-free ( P < .05; hazard ratio [HR], 2.2) period and a shorter survival ( P < .05; HR, 2.2). These results support FMC as a suitable model in comparative oncology and identify sf-RON expression as potential predictor of outcomes for this disease.

Therapeutic Considerations for Ron Receptor Expression in Prostate Cancer

INTRODUCTION

The Ron receptor tyrosine kinase was initially discovered as a protein which played a critical role in regulating inflammatory responses. This effect was primarily determined through studies in various macrophage populations. Since its initial discovery, a role has emerged for Ron as a driver of cancer within epithelial cells. After numerous publications have detailed a role for Ron in promoting tumor initiation, growth, and metastasis, Ron has been designated as an emerging therapeutic option in a variety of cancers.

AREAS COVERED

This review discusses the current literature regarding the role of Ron in prostate cancer and places special emphasis on the role of Ron in both epithelial cells and macrophages. Whole body loss of Ron signaling initially exposed a variety of prostate cancer growth mechanisms regulated by Ron. With the knowledge that Ron plays an integral part in regulating the function of epithelial cells and macrophages, studies commenced to discern the cell type specific functions for Ron in prostate cancer. A novel role for Ron in promoting Castration Resistant Prostate Cancer has recently been uncovered, and the results of these studies are summarized herein. Furthermore, this review gives a summary of several currently available compounds which show promise at targeting Ron in both epithelial and macrophage populations.

OUTLOOK

Sufficient evidence has been provided for the initiation of clinical trials focused on targeting Ron in both macrophage and epithelial compartments for the treatment of prostate cancer. A number of therapeutic avenues for targeting Ron in prostate cancer are currently available; however, special consideration will need to take place knowing that Ron signaling impacts multiple cell types. Further understanding of the cell type specific functions of Ron in prostate cancer will help inform and shape future clinical research and therapeutic strategies.

Inhibition of RON kinase potentiates anti-CTLA-4 immunotherapy to shrink breast tumors and prevent metastatic outgrowth

The advent of immune checkpoint blockade as a new strategy for immunotherapy has changed the outlook for many aggressive cancers. Although complete tumor eradication is attainable in some cases, durable clinical responses are observed only in a small fraction of patients, underlining urgent need for improvement. We previously showed that RON, a receptor tyrosine kinase expressed in macrophages, suppresses antitumor immune responses, and facilitates progression and metastasis of breast cancer. Here, we investigated the molecular changes that occur downstream of RON activation in macrophages, and whether inhibition of RON can cooperate with checkpoint immunotherapy to eradicate tumors. Activation of RON by its ligand, MSP, altered the gene expression profile of macrophages drastically and upregulated surface levels of CD80 and PD-L1, ligands for T-cell checkpoint receptors CTLA-4 and PD-1. Genetic deletion or pharmacological inhibition of RON in combination with anti-CTLA-4, but not with anti-PD-1, resulted in improved clinical responses against orthotopically transplanted tumors compared to single-agent treatment groups, resulting in complete tumor eradication in 46% of the animals. Positive responses to therapy were associated with higher levels of T-cell activation markers and tumor-infiltrating lymphocytes. Importantly, co-inhibition of RON and anti-CTLA-4 was also effective in clearing metastatic breast cancer cells in lungs, resulting in clinical responses in nearly 60% of the mice. These findings suggest that RON inhibition can be a novel approach to potentiate responses to checkpoint immunotherapy in breast cancer.

Interactions between NRP1 and VEGFR2 molecules in the plasma membrane

Here we use a quantitative FRET approach, specifically developed to probe membrane protein interactions, to study the homo-association of neuropilin 1 (NRP1) in the plasma membrane, as well as its hetero-interactions with vascular endothelial growth factor receptor 2 (VEGFR2). Experiments are performed both in the absence and presence of the soluble ligand vascular endothelial growth factor A (VEGFA), which binds to both VEGFR2 and NRP1. We demonstrate the presence of homo-interactions between NRP1 molecules, as well as hetero-interactions between NRP1 and VEGFR2 molecules, in the plasma membrane. Our results underscore the complex nature of the interactions between self-associating receptors, co-receptors, and their ligands in the plasma membrane. They also highlight the need for new methodologies that capture this complexity, and the need for precise physiological measurements of local receptor surface densities in the membrane of cells. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.

RON kinase inhibition reduces renal endothelial injury in sickle cell disease mice

Sickle cell disease patients are at increased risk of developing a chronic kidney disease. Endothelial dysfunction and inflammation associated with hemolysis lead to vasculopathy and contribute to the development of renal disease. Here we used a Townes sickle cell disease mouse model to examine renal endothelial injury. Renal disease in Townes mice was associated with glomerular hypertrophy, capillary dilation and congestion, and significant endothelial injury. We also detected substantial renal macrophage infiltration, and accumulation of macrophage stimulating protein 1 in glomerular capillary. Treatment of human cultured macrophages with hemin or red blood cell lysates significantly increased expression of macrophage membrane-associated protease that might cleave and activate circulating macrophage stimulating protein 1 precursor. Macrophage stimulating protein 1 binds to and activates RON kinase, a cell surface receptor tyrosine kinase. In cultured human renal glomerular endothelial cells, macrophage stimulating protein 1 induced RON downstream signaling, resulting in increased phosphorylation of ERK and AKT kinases, expression of Von Willebrand factor, increased cell motility, and re-organization of F-actin. Specificity of macrophage stimulating protein 1 function was confirmed by treatment with RON kinase inhibitor BMS-777607 that significantly reduced downstream signaling. Moreover, treatment of sickle cell mice with BMS-777607 significantly reduced glomerular hypertrophy, capillary dilation and congestion, and endothelial injury. Taken together, our findings demonstrated that RON kinase is involved in the induction of renal endothelial injury in sickle cell mice. Inhibition of RON kinase activation may provide a novel approach for prevention of the development of renal disease in sickle cell disease.

FOXC1 promotes melanoma by activating MST1R/PI3K/AKT

FOXC1 is a member of Forkhead box family transcription factors. We showed that FOXC1 level was increased in melanoma cells and tissues and correlated with hypomethylation of the FOXC1 gene. Overexpression of FOXC1 promoted proliferation, migration, invasion, colony formation and growth in 3D Matrigel of melanoma cells. FOXC1 increased MST1R and activated the PI3K/AKT pathway. Also, FOXC1 expression was associated with disease progression and poor prognosis of melanoma. We suggest that FOXC1 is a potential prognostic biomarker for treating melanoma and predicting outcome of patients.

RON is overexpressed in bladder cancer and contributes to tumorigenic phenotypes in 5637 cells

Tyrosine kinase receptor macrophage stimulating 1 receptor (MST1R, also known as RON) contributes to the transformation and malignant progression observed in epithelial cells. The purpose of the present study is to assess the value of RON as a potential target in bladder cancer (BC) therapeutics. The expression profile of RON in BC tissues and adjacent noncancerous tissues was detected via immunohistochemistry. The rate of positive RON expression differed significantly between bladder urothelial cancer tissues (54.7%) and paraneoplastic tissues (29.4%) (P<0.05). RON expression was positively associated with the number of tumors per patient, histological grading, pathological stage and distant metastasis (all P<0.05). Downregulation of RON expression using small interfering RNAs inhibited cell growth, cell migration and promoted cell apoptosis in the 5637 cell line. RON inhibition induced cell cycle arrest at the G₁/S boundary following an increase of cyclin-dependent kinase inhibitor 1B and cyclin-dependent kinase inhibitor 1A, and a decrease of cyclin D1, cyclin D3 and cyclin-dependent kinase 4 expression. Furthermore, knockdown of RON significantly blocked signal transduction, including downstream protein kinase B and mitogen-activated protein kinase pathways. These results indicated that RON serves a notable role in BC and is a potential target of therapeutic intervention.

Expression of RON in colorectal cancer and its relationships with tumor cell behavior and prognosis

Aims and background

The aims of the current study were to evaluate whether recepteur d'origine nantais (RON) affects tumor cell behavior and oncogenic signaling pathways in colorectal cancer, and to examine the relationship of its expression with various clinicopathological parameters and patient survival.

Methods

Immunohistochemistry, Western blot and RT-PCR were used to detect the expression of the RON gene in human colorectal cancer tissue. To study the biological role of RON in tumor cell behavior and cellular signaling pathways, we used small interfering RNA (siRNA) to knock down RON gene expression in human colorectal cancer cell lines.

Results

Knockdown of RON inhibited the induction of the invasive growth phenotype and the activation of oncogenic signaling pathways including Akt, MAPK and β-catenin. RON overexpression was associated with tumor size, lymphovascular invasion, depth of invasion, lymph node metastasis, distant metastasis, tumor stage and poor survival.

Conclusions

These results suggest that RON overexpression may help in predicting poor clinical outcomes in colorectal cancer.

Analogs of the hepatocyte growth factor and macrophage-stimulating protein hinge regions act as Met and Ron dual inhibitors in pancreatic cancer cells

Pancreatic cancer is among the leading causes of cancer death in the USA, with limited effective treatment options. A major contributor toward the formation and persistence of pancreatic cancer is the dysregulation of the hepatocyte growth factor (HGF)/Met (HGF receptor) and the macrophage-stimulating protein (MSP)/Ron (MSP receptor) systems. These systems normally mediate a variety of cellular behaviors including proliferation, survival, and migration, but are often overactivated in pancreatic cancer and contribute toward cancer progression. Previous studies have shown that HGF must dimerize to activate Met. Small-molecule antagonists with homology to a 'hinge' region within the putative dimerization domain of HGF have been developed that bind to HGF and block dimerization, therefore inhibiting Met signaling. Because of the structural and sequence homology between MSP and HGF, we hypothesized that the inhibition of HGF by the hinge analogs may extend to MSP. The primary aim of this 'proof-of-concept' study was to determine whether hinge analogs could inhibit cellular responses to both HGF and MSP in pancreatic cancer cells. Our results showed that these compounds inhibited HGF and MSP activity. Hinge analog treatment resulted in decreased Met and Ron activation, and suppressed malignant cell behaviors including proliferation, migration, and invasion in pancreatic cancer cells in vitro. These results suggest that the hinge analogs represent a novel group of molecules that may offer a therapeutic approach for the treatment of pancreatic cancer and warrant further development and optimization.

Qingchang Wenzhong Decoction Attenuates DSS-Induced Colitis in Rats by Reducing Inflammation and Improving Intestinal Barrier Function via Upregulating the MSP/RON Signalling Pathway

Ulcerative colitis (UC) is a chronic, nonspecific, inflammatory disease for which an effective treatment is lacking. Our previous study found that Qingchang Wenzhong Decoction (QCWZD) can significantly improve the clinical symptoms of UC and ameliorate dextran sulphate sodium- (DSS-) induced ulcerative colitis in rats by downregulating the IP10/CXCR3 axis-mediated inflammatory response. The purpose of the present study was to further explore the mechanism of QCWZD for UC in rats models, which were established by 7-day administration of 4.5% dextran sulphate sodium solution. QCWZD was administered daily for 7 days; then we determined the serum macrophage-stimulating protein concentration (MSP) and recepteur d'origine nantais (RON) expression and its downstream proteins (protein kinase B [Akt], phosphorylated [p] Akt, occludin, zona occluden- [ZO-] 1, and claudin-2) in colon tissue using Western blotting and quantitative polymerase chain reaction. In DSS-induced UC, QCWZD significantly alleviated colitis-associated inflammation, upregulated serum MSP expression and RON expression in the colon, reduced the pAkt levels, promoted colonic occluding and ZO-1 expression, and depressed claudin-2 expression. In conclusion, the MSP/RON signalling pathway plays an important role in the pathogenesis of UC by involving the inflammatory response and improving intestinal barrier function. QCWZD appears to attenuate DSS-induced UC in rats by upregulating the MSP/RON signalling pathway.

Tumor Inhibitory Effect of IRCR201, a Novel Cross-Reactive c-Met Antibody Targeting the PSI Domain

Hepatocyte growth factor receptor (HGFR, c-Met) is an essential member of the receptor tyrosine kinase (RTK) family that is often dysregulated during tumor progression, driving a malignant phenotypic state and modulating important cellular functions including tumor growth, invasion, metastasis, and angiogenesis, providing a strong rationale for targeting HGF/c-Met signaling axis in cancer therapy. Based on its protumorigenic potentials, we developed IRCR201, a potent antagonistic antibody targeting the plexin-semaphorin-integrin (PSI) domain of c-Met, using synthetic human antibody phage libraries. We characterized and evaluated the biochemical properties and tumor inhibitory effect of IRCR201 in vitro and in vivo. IRCR201 is a novel fully-human bivalent therapeutic antibody that exhibits cross-reactivity against both human and mouse c-Met proteins with high affinity and specificity. IRCR201 displayed low agonist activity and rapidly depleted total c-Met protein via the lysosomal degradation pathway, inhibiting c-Met-dependent downstream activation and attenuating cellular proliferation in various c-Met-expressing cancer cells. In vivo tumor xenograft models also demonstrated the superior tumor inhibitory responsiveness of IRCR201. Taken together, IRCR201 provides a promising therapeutic agent for c-Met-positive cancer patients through suppressing the c-Met signaling pathway and tumor growth.

HGFL-mediated RON signaling supports breast cancer stem cell phenotypes via activation of non-canonical β-catenin signaling

Breast cancer stem cells (BCSCs), which drive tumor progression, recurrence, and metastasis, are considered a major challenge for breast cancer treatments, thus the discovery of novel pathways regulating BCSC maintenance remains essential to develop new strategies to effectively target this population and combat disease mortality. The HGFL-RON signaling is overexpressed in human breast cancers and is associated with increased breast cancer progression, metastasis, and poor prognosis. Here, we report that overexpression of RON/MST1R and HGFL/MST1 in cell lines and primary tumors increases BCSC self-renewal, numbers, and tumorigenic potential after syngeneic transplantation. Transcriptome analyses also reveal that the HGFL-RON signaling pathway regulates additional BCSC functions and supports an immunosuppressive microenvironment to stimulate tumor formation and progression. Moreover, we show that genetic and chemical downregulation of HGFL-RON signaling disrupts BCSC phenotypes and tumor growth by suppressing the RON-mediated phosphorylation/activation of β-CATENIN/CTNNB1 and its effector NF-κB/RELA. These studies indicate that HGFL-RON signaling regulates BCSC phenotypes and the tumor microenvironment to drive tumorigenesis and present HGFL/RON as novel therapeutic targets to effectively eradicate BCSCs in patients.

Phase 1 study of narnatumab, an anti-RON receptor monoclonal antibody, in patients with advanced solid tumors

Purpose Macrophage-stimulating 1-receptor (RON) is expressed on macrophages, epithelial cells, and a variety of tumors. Narnatumab (IMC-RON8; LY3012219) is a neutralizing monoclonal antibody that blocks RON binding to its ligand, macrophage-stimulating protein (MSP). This study assessed safety, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and efficacy of narnatumab in patients with advanced solid tumors. Methods Narnatumab was administered intravenously weekly at 5, 10, 15, or 20 mg/kg or every 2 weeks at 15, 20, 30, or 40 mg/kg in 4-week cycles. Results Thirty-nine patients were treated, and 1 dose-limiting toxicity (DLT) (grade 3 hyponatremia, 5 mg/kg) was reported. The most common narnatumab-related adverse events (AEs) were fatigue (20.5%) and decreased appetite, diarrhea, nausea, and vomiting (10.3% each). Except for 2 treatment-related grade 3 AEs (hyponatremia, hypokalemia), all treatment-related AEs were grade 1 or 2. Narnatumab had a short half-life (<7 days). After Cycle 2, no patients had concentrations above 140 μg/mL (concentration that demonstrated antitumor activity in animal models), except for 1 patient receiving 30 mg/kg biweekly. Eleven patients had a best response of stable disease, ranging from 6 weeks to 11 months. Despite only 1 DLT, due to suboptimal drug exposure, the dose was not escalated beyond 40 mg/kg biweekly. This decision was based on published data reporting that mRNA splice variants of RON are highly prevalent in tumors, accumulate in cytoplasm, and are not accessible by large-molecule monoclonal antibodies. Conclusions Narnatumab was well tolerated and showed limited antitumor activity with this dosing regimen.

Monoclonal antibody Zt/g4 targeting RON receptor tyrosine kinase enhances chemosensitivity of bladder cancer cells to Epirubicin by promoting G1/S arrest and apoptosis

Epirubicin (EPI) is one of the most used intravesical chemotherapy agents after transurethral resection to non-muscle invasive bladder tumors (NMIBC) to prevent cancer recurrence and progression. However, even after resection of bladder tumors and intravesical chemotherapy, half of them will recur and progress. RON is a membrane tyrosine kinase receptor usually overexpressed in bladder cancer cells and associated with poor pathological features. This study aims to investigate the effects of anti-RON monoclonal antibody Zt/g4 on the chemosensitivity of bladder cells to EPI. After Zt/g4 treatment, cell cytotoxicity was significantly increased and cell invasion was markedly suppressed in EPI-treated bladder cancer cells. Further investigation indicated that combing Zt/g4 with EPI promoted cell G1/S-phase arrest and apoptosis, which are the potential mechanisms that RON signaling inhibition enhances chemosensitivity of EPI. Thus, combing antibody-based RON targeted therapy enhances the therapeutic effects of intravesical chemotherapy, which provides new strategy for further improvement of NMIBC patient outcomes.

Role of the Microenvironment in Liver Metastasis: From Pre- to Prometastatic Niches

Liver metastases remain a major barrier to successful management of malignant disease, particularly for cancers of the gastrointestinal tract but also for other malignancies, such as breast carcinoma and melanoma. The ability of metastatic cells to survive and proliferate in the liver is determined by the outcome of complex, reciprocal interactions between tumor cells and different local resident subpopulations, including the sinusoidal endothelium, stellate, Kupffer, and inflammatory cells that are mediated through cell-cell and cell-extracellular matrix adhesion and the release of soluble factors. Cross-communication between different hepatic resident cells in response to local tissue damage and inflammation and the recruitment of bone marrow cells further enhance this intercellular communication network. Both resident and recruited cells can play opposing roles in the progression of metastasis, and the balance of these divergent effects determines whether the tumor cells will die, proliferate, and colonize the new site or enter a state of dormancy. Moreover, this delicate balance can be tilted in favor of metastasis, if factors produced by the primary tumor precondition the microenvironment to form niches of activated resident cells that promote tumor expansion. This review aims to summarize current knowledge on these diverse interactions and the impact they can have on the clinical management of hepatic metastases. Clin Cancer Res; 22(24); 5971-82. ©2016 AACR.

Short-form Ron is a novel determinant of ovarian cancer initiation and progression

Short-form Ron (sfRon) is an understudied, alternative isoform of the full-length Ron receptor tyrosine kinase. In contrast to Ron, which has been shown to be an important player in many cancers, little is known about the role of sfRon in cancer pathogenesis. Here we report the striking discovery that sfRon expression is required for development of carcinogen-induced malignant ovarian tumors in mice. We also show that sfRon is expressed in several subtypes of human ovarian cancer including high-grade serous carcinomas, which is in contrast to no detectable expression in healthy ovaries. In addition, we report that introduction of sfRon into OVCAR3 cells resulted in epithelial-to-mesenchymal transition, activation of the PI3K and PDK1 pathway, and inhibition of the MAPK pathway. We demonstrated that sfRon confers an aggressive cancer phenotype in vitro characterized by increased proliferation and migration, and decreased adhesion of ovarian cancer cells. Moreover, the in vivo studies show that OVCAR3 tumors expressing sfRon exhibit significantly more robust growth and spreading to the abdominal cavity when compared with the parental sfRon negative OVCAR3 cells. These data suggest that sfRon plays a significant role in ovarian cancer initiation and progression, and may represent a promising therapeutic target for ovarian cancer treatment.