Expression Of Recepteur D'origine Nantais Research Articles

Pathological significance of abnormal recepteur d'origine nantais and programmed death ligand 1 expression in colorectal cancer.

BACKGROUNDProgrammed death ligand 1 (PD-L1) immunotherapy remains poorly efficacious in colorectal cancer (CRC). The recepteur d’origine nantais (RON) receptor tyrosine kinase plays an important role in regulating tumor immunity.AIMTo identify the patterns of RON and PD-L1 expression and explore their clinical significance in CRC.METHODSGene expression data from the Gene Expression Omnibus database (GEO; n = 290) and patients at the First Affiliated Hospital, Zhejiang University School of Medicine (FAHZUSM; n = 381) were analyzed to determine the prognostic value of RON and PD-L1 expression within the tumor microenvironment of CRC. HT29 cell line was treated with BMS-777607 to explore the relationship between RON activity and PD-L1 expression. Signaling pathways and protein expression perturbed by RON inhibition were evaluated by cellular immunofluorescence and Western blot.RESULTSIn the GEO patient cohort, cut-off values for RON and PD-L1 expression were determined to be 7.70 and 4.3, respectively. Stratification of patients based on these cutoffs demonstrated that high expression of RON and PD-L1 was associated with a poor prognosis. In the FAHZUSM cohort, rates of high expression of RON in tumor cells, high PD-L1 expression in tumor cells and tumor infiltrating monocytes, and both high RON and high PD-L1 expression in the tumor microenvironment were 121 (32%), 43 (11%), 91 (24%), and 51 (13.4%), respectively. High expression of RON was significantly correlated with high expression of PD-L1 in the tumor cell compartment (P < 0.001). High expression of RON and that of PD-L1 were independent prognostic factors for poorer overall survival. Concurrent high expression of both RON and PD-L1 in the tumor microenvironment was significantly associated with a poor prognosis. In vitro, BMS-777607 inhibited the phosphorylation of RON, inhibited PD-L1 expression, and attenuated activation of the ERK1/2 and AKT signaling pathways in CRC cells.CONCLUSIONRON, PD-L1, and their crosstalk are significant in predicting the prognostic value of CRC. Moreover, phosphorylation of RON upregulates PD-L1 expression, which provides a novel approach to immunotherapy in CRC.

Prognostic role of the recepteur d'origine nantais (RON) expression in primary high-grade osteosarcoma

BackgroundOsteosarcoma is a common primary malignant bone tumor susceptible to distant metastasis. The clinical outcome for patients remains poor due to the resistance to chemotherapy and lacking effective therapeutic targets. Recepteur d'origine nantais (RON), a transmembrane protein of the c-MET proto-oncogene family, has been reported to contribute to the malignant progression and bone metastasis in several tumors. The present study aimed to explore the prognostic significance of RON in primary high-grade osteosarcoma. MethodsImmunohistochemistry (IHC) and western blotting (WB) were used to investigate the protein expression of RON in 80 surgically resected specimens (50 high-grade osteosarcoma specimens and 30 non-neoplastic bone tissues) and 6 cell lines. The χ2 test or independent-sample Student's t-test was used to assess the significance of RON difference between osteosarcoma and non-neoplastic bone tissues. The χ2 test and Fisher's exact test were used to analyze the association of RON with the clinicopathological features of osteosarcoma patients. Kaplan–Meier method and Cox proportional hazards model were used to assess the significance of RON for the survival of osteosarcoma patients. ResultsThe results of IHC and WB observed significant overexpression of RON in osteosarcoma specimens (P < 0.001) and osteosarcoma cell lines. Moreover, immunohistochemical high expression of RON was associated with a poor response to chemotherapy (P = 0.032) as well as worse progression-free (P = 0.003) and overall (P < 0.001) survival of osteosarcoma patients. Multivariate analysis revealed that high expression of RON was independently associated with reduced progression-free (P = 0.027, HR = 2.31) and overall survival (P = 0.004, HR = 5.06) time of osteosarcoma patients. ConclusionsThe present study demonstrated that high expression of RON held independent value for unfavorable survival in primary high-grade osteosarcoma. Its potential role as a therapeutic target for osteosarcoma treatment deserves further research.

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

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

Role of Recepteur D'origine Nantais on Gastric Cancer Development and Progression.

Recepteur d'origine nantais (RON) is a receptor tyrosine kinase belonging to the subfamily of which c-MET is the prototype. Large epidemiologic studies have confirmed the strong association between RON and gastric cancer development. Constitutive activation of RON signaling directly correlates with tumorigenic phenotypes of gastric cancer and a poor survival rate in advanced gastric cancer patients. In this review, we focus on recent evidence of the aberrant expression and activation of RON in gastric cancer tumors and provide insights into the mechanism of RON signaling associated with gastric cancer progression and metastasis. Current therapeutics against RON in gastric cancer are summarized.

The Complete Loss of Tyrosine Kinase Receptors MET and RON Is a Poor Prognostic Factor in Patients with Extrahepatic Cholangiocarcinoma.

Although the survival of patients with cholangiocarcinoma has improved, the prognosis remains unfavorable. The overexpression of mesenchymal-epithelial transition factor (MET) and recepteur d'origine nantais (RON) has been considered to be indicative of a poor prognosis in some types of cancer. On the other hand, some studies have shown that the expression of MET and RON is a favorable prognostic factor in certain types of tumors. Based on the immunohistochemical analysis of MET and RON, 290 patients who underwent resection for extrahepatic cholangiocarcinoma were divided into three groups: MET/RON-negative, -intermediate, and -positive. The associations between MET/RON expression and clinicopathological features, including prognosis, were analyzed. MET/RON-negativity was associated with nodal metastasis and advanced pathological stage. The overall 5-year survival rates were significantly lower in the MET/RON-negative and MET/RON-positive groups than in the MET/RON-intermediate group (28.3%, 32.4% and 48.5%, respectively; p=0.01). The complete loss of one or both MET and RON, as well as their overexpression, is a poor prognostic factor in patients with extrahepatic cholangiocarcinoma, probably due to the high rate of lymph-node metastasis.

Elevated RON protein expression in endometriosis and disease-associated ovarian cancers.

Recepteur d'origine nantais (RON) protein expression has been demonstrated to correlate with tumor progression, metastasis, and prognosis, and its mRNA expression increases in deeply infiltrating endometriotic lesions. However, it remains unclear whether RON protein expression also increases in endometriotic lesions, and may be a risk factor of malignant transformation in endometriotic lesions. The protein expression of RON in control (n=19), eutopic (n=16), and ectopic (n=51) endometria, as well as in endometriosis-associated ovarian cancers (EAOC, n=16) was determined by immunohistochemical (IHC) staining. Endometriotic lesions expressed low levels of RON protein, but no RON protein expression appeared in matched eutopic or control endometrium. EAOC exhibited high levels of RON protein. The frequency and IHC score of RON protein expression were both significantly higher in EAOC [100.0% (14/14), 5.37±0.74] than those in endometriotic lesions [51.0% (26/51), 2.15±1.12; P=0.002, 0.001]. Multivariate analysis of covariance only revealed a correlation of RON protein expression and EAOC (P=0.006), but no correlations of RON protein expression and clinical parameters (P>0.05). These obtained results suggest that increased RON expression might be involved in the pathogenesis of endometriosis and disease-associated ovarian cancers.

MicroRNA-375 Functions as a Tumor-Suppressor Gene in Gastric Cancer by Targeting Recepteur d'Origine Nantais.

Emerging evidence supports a fundamental role for microRNAs (miRNA) in regulating cancer metastasis. Recently, microRNA-375 (miR-375) was reported to be downregulated in many types of cancers, including gastric cancer. Increase in the expression of Recepteur d’Origine Nantais (RON), a receptor tyrosine kinase, has been reported in tumors. However, the function of miR-375 and RON expression in gastric cancer metastasis has not been sufficiently studied. In silico analysis identified miR-375 binding sites in the 3′-untranslated regions (3′-UTR) of the RON-encoding gene. Expression of miR-375 resulted in reduced activity of a luciferase reporter containing the 3′-UTR fragments of RON-encoding mRNA, confirming that miR-375 directly targets the 3′-UTR of RON mRNA. Moreover, we found that overexpression of miR-375 inhibited mRNA and protein expression of RON, which was accompanied by the suppression of cell proliferation, migration, and invasion in gastric cancer AGS and MKN-28 cells. Ectopic miR-375 expression also induced G1 cell cycle arrest through a decrease in the expression of cyclin D1, cyclin D3, and in the phosphorylation of retinoblastoma (Rb). Knockdown of RON by RNAi, similar to miR-375 overexpression, suppressed tumorigenic properties and induced G1 arrest through a decrease in the expression of cyclin D1, cyclin D3, and in the phosphorylation of Rb. Thus, our study provides evidence that miR-375 acts as a suppressor of metastasis in gastric cancer by targeting RON, and might represent a new potential therapeutic target for gastric cancer.

HIV‑1 downregulates the expression and phosphorylation of receptor tyrosine kinase by targeting the NF‑κB pathway.

Macrophages are major targets of human immunodeficiency virus (HIV) and can act as long-term reservoirs of the virus. Chronic HIV-1 infection is associated with dysregulated inflammation. Recepteur d'origine nantais (RON) is expressed in tissue resident macrophages and functions to maintain inflammatory homeostasis. The present study aimed to compare the expression of RON on HIV-positive and -negative participants, and to investigate the mechanism by which HIV-1 influences the expression and function of RON in the JLTRG T cell line. The levels of RON and the RON ligand, macrophage-stimulating protein (MSP), in the peripheral blood of HIV-1-positive patients that were receiving (n=22) or not receiving highly active anti-retroviral therapy (HAART) (n=82) and 37 healthy control participants were determined by enzyme-linked immunosorbent assay. Expression of RON and MSP in the JLTRG T cell line was assessed by western blotting and the subcellular location was analyzed by fluorescence microscopy. JLTRG cells were co-cultured with a cell line that stably expresses HIV, H9/HTLV-IIIB, and alterations in the levels of RON and nuclear factor-κB (NF-κB) in JLTRG cells were assessed by western blotting. The expression of RON and MSP were significantly different in the serum of HIV-1- positive patients that were receiving HAART compared with those not receiving HAART (P<0.05) and healthy control patients (P<0.01). RON was detected in JLTRG cells, and was shown to be downregulated by HIV-1 infection. HIV-1 infection of JLTRG cells also reduced NF-κB phosphorylation. Thus, HIV-1 was shown to downregulate the expression and phosphorylation of RON by targeting the NF-κB pathway.

Effect of Recepteur d'Origine Nantais expression on chemosensitivity and tumor cell behavior in colorectal cancer.

Recepteur d'Origine Nantais (RON) expression is known to induce oncogenic properties including tumor cell growth, survival, motility, angiogenesis and chemoresistance. In the present study, we evaluated whether RON affects chemosensitivity and oncogenic behavior of colorectal cancer cells and investigated its prognostic value in colorectal cancer. To evaluate the impact of RON on chemosensitivity and tumor cell behavior, we treated colorectal cancer cells with small interfering RNAs specific to RON. This was followed by flow cytometric analyses and migration, Matrigel invasion and endothelial tube formation assays. The expression of RON was investigated by immunohistochemistry in colorectal cancer tissues. TUNEL assay and immunohistochemical staining for CD34 and D2-40 were deployed to determine apoptosis, angiogenesis and lymphangiogenesis. RON knockdown enhanced 5-fluorouracil (FU)-induced apoptosis by upregulating the activities of caspases and expression of proapoptotic genes. Moreover, it enhanced 5-FU-induced cell cycle arrest by decreasing the expression of cyclins and cyclin‑dependent kinases and inducing that of p21. Furthermore, RON knockdown augmented the 5-FU-induced inhibition of invasion and migration of colorectal cancer cells. The β-catenin signaling cascade was blocked by RON knockdown upon 5-FU treatment. RON knockdown also decreased endothelial tube formation and expression of VEGF-A and HIF-1α and increased angiostatin expression. Furthermore, it inhibited lymphatic endothelial cell tube formation and the expression of VEGF-C and COX-2. RON expression was observed to be associated with age, tumor size, lymphovascular and perineural invasion, tumor stage, lymph node and distant metastasis, and poor survival rate. The mean microvessel density value of RON-positive tumors was significantly higher than that of RON-negative ones. These results indicate that RON is associated with tumor progression by inhibiting chemosensitivity and enhancing angiogenesis in colorectal cancer.

Expression of Hepatocyte Growth Factor-Like Protein in Human Wound Tissue and Its Biological Functionality in Human Keratinocytes.

Hepatocyte growth factor-like protein (HGFl) and its receptor, Recepteur d'Origine Nantais (RON), have been implicated in the development of wound chronicity. HGFl and RON expression was detected in acute wound tissue, chronic wound tissue and in normal skin using quantitative polymerase chain reaction (Q-PCR). HGFl and RON expression was also assessed in chronic healing and chronic non-healing wound tissues using Q-PCR and immunohistochemical staining. Expression was similarly detected in the HaCaT immortalized human keratinocyte cell line using reverse transcription polymerase chain reaction (RT-PCR). rhHGFl was used to assess the impact of this molecule on HaCaT cell functionality using in vitro growth assays and electric cell-substrate impendence sensing (ECIS) migration assays. HGFl and RON transcript expression were significantly increased in acute wound tissue compared to chronic wound tissue and were also elevated, though non-significantly, in comparison to normal skin. Minimal expression was seen in both healing and non-healing chronic wounds. Treatment of HaCaT cells with rhHGFl had no effect on growth rates but did enhance cell migration. This effect was abolished by the addition of a phospholipase C gamma (PLCγ) small molecule inhibitor. The increased expression of HGFl and RON in acute, healing wounds and the pro-migratory effect of HGFl in an in vitro human keratinocyte model, may indicate a role for HGFl in active wound healing.

Prognostic Value of Hepatocyte Growth Factor Receptor Expression in Patients with Perihilar Cholangiocarcinoma

Although an aggressive surgical approach to perihilar cholangiocarcinoma (PHC) has improved survival, a prognosis of advanced PHC remains unsatisfactory. The overexpression of mesenchymal-epithelial transition factor (MET) and recepteur d'origine nantais (RON) has been shown to be associated with poor prognosis in some types of cancer. One hundred sixty-nine patients who underwent histologically curative resection for PHC were subjected to immunohistochemical analysis for MET and RON. The association between a positive expression of MET or RON and clinicopathologic features as well as the patients' prognosis were analyzed. There were 27 patients (16 %) who had a positive expression for both MET and RON. Although clinicopathologic features in the either MET- or RON-negative group were not significantly different compared to the both MET- and RON-positive group, the prognosis tended to be worse in the patients with both MET and RON positivity. When the analysis was limited to patients with advanced-stage disease (stage III and IVa), a multivariate analysis revealed that both MET and RON positivity and lymph node metastasis were identified as independent poor prognostic factors. The overall survival rate for patients with both MET and RON positivity was worse than that with either MET or RON negativity in patients with advanced PHC. The poor prognosis in these patients was not associated with unfavorable clinicopathologic features. The examination of MET and RON expression in PHC may enable a tailored method for patient classification that could not otherwise be achieved using the conventional pathologic classification system.

RON (recepteur d’origine nantais) expression and its association with tumor progression in laryngeal squamous cell carcinoma

Several human tumor tissues show an aberrant expression and activation of recepteur d'origine nantais (RON). In this paper, we investigate the expression of RON in human laryngeal squamous cell carcinoma (SCC) and evaluate whether RON affects the tumor cell progression in human laryngeal SCC cell line. Immunohistochemistry was used to assess RON expression in human laryngeal SCC. To evaluate the impact of RON knockdown, the cell invasion assay and cell migration assay using small-interfering RNA were performed. The expression of RON protein was dominantly observed in laryngeal SCC tissues relative to adjacent normal mucosa in all cases. Knockdown of RON resulted in significantly reduced cell invasion in human laryngeal SCC cells. Cell migration showed a marked decrease in RON knockdown laryngeal SCC cells compared to the negative control laryngeal SCC cells. Laryngeal SCC cell migration was enhanced by incubation with macrophage stimulating protein (MSP). RON is highly expressed in human laryngeal SCC. We suggest that RON plays an important role in invasion, and metastasis of laryngeal SCC.

Integrative genomic analyses of recepteur d’origine nantais and its prognostic value in cancer

Recepteur d'origine nantais (RON) is a receptor tyrosine kinase (RTK) normally expressed at low levels in epithelial cells. RON is a 180-kDa heterodimeric protein composed of a 40-kDa α-chain and a 150-kDa transmembrane β-chain with intrinsic tyrosine kinase activity. The extracellular sequences of RON contain several domains including an N-terminal semaphorin (sema) domain, followed by the plexin, semaphorin, integrin (PSI) domain, and four immunoglobulin, plexin, transcription factor (IPT) domains. Here, we identified RON genes from 14 vertebrate genomes and found that RON exists in all types of vertebrates including fish, amphibians, birds and mammals. We found that the human RON gene showed predominant expression in the liver, lymph node, thymus, intestine, lung, mammary gland, bone marrow, brain, heart, placenta, bladder, cortex, cervix, skin, kidney and prostate. When searched in the PrognoScan database, human RON was also found to be expressed in bladder, blood, breast, glioma, esophageal, colorectal, head and neck, ovarian, lung and skin cancer. The relationship between the expression of RON and prognosis was found to vary in different cancer types, even in the same cancer from different databases. This suggests that the function of RON in these tumors may be multidimensional, not just as a tumor suppressor or oncogene. Six available single-nucleotide polymorphisms (SNPs) disrupting existing exonic splicing enhancers were identified in RON. This may contribute to the generation of active RON variants by alternative splicing, which is frequently observed in primary tumors.

Involvement of Recepteur d'Origine Nantais Receptor Tyrosine Kinase in Epstein-Barr Virus-Associated Nasopharyngeal Carcinoma and Its Metastasis

Nasopharyngeal carcinoma (NPC) is characteristic for its strong association with Epstein-Barr virus (EBV) and high metastatic rate. Recently, overexpressed recepteur d'origine nantais (RON) (MST1R), receptor tyrosine kinase has been reported in human cancers and tumor metastasis. Therefore, the role of RON in EBV-associated NPC and its metastasis was investigated. Here we show that RON was found in NPC but not in control tissues. A significant correlation of latent membrane protein 1 (LMP1) and RON expression was found in NPC (Pearson's χ(2) test; P = 0.0023). At the molecular level, LMP1 stimulates nuclear factor-κB binding to the RON promoter through its carboxyl-terminal activation region 1 to induce expression of RON. Knockdown of RON in cells expressing LMP1 significantly reverses LMP1-induced epithelial-mesenchymal transition and suppresses LMP1-induced cell migration and invasion. These results suggest an important role of RON in the tumorigenesis and metastasis of NPC and RON may be a novel therapeutic target for EBV-associated NPC.

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

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

RON Is Associated with Tumor Progression in Head and Neck Squamous Cell Cancer

Objective: To investigate that the recepteur d’origine nantais (RON) expression is expressed in human head and neck squamous cell cancer (HNSCC) cells and to evaluate whether RON affects tumor cell behavior in head and neck cancer cell lines, thus serving as a target for molecular therapy in a preclinical model. Method: The protein expression of RON by immunohistochemistry and western blot analysis was investigated in human head-neck cancer tissues. To evaluate the impact of RON knock down on behavior of human head-neck cancer cell lines, invasion and migration assays using small-interfering RNA were performed. Western blot analysis was used to assess alteration in protein expression. Results: RON positive immunoreactions were observed relative to adjacent mucosal tissue in all 28 cases, while 15 cases (53.6%) were over-expressed. RON over-expression was significantly associated with lymph node metastasis. RON protein expression was increased in cervical metastatic lymph node tissue by western blot analysis. Treatment of RON ligand, macrophage stimulating proetin (MSP) increased cell migration and invasion in human head-neck cancer cell lines (SNU 1041, PCI 50). The knockdown of RON significantly suppressed tumor cell migration, invasion. The Erk, p38 phosphorylation was reduced by knockdown of RON in PCI 50. Conclusion: RON expression might play an important role in the progression, especially lymphatic metastasis of head and neck squamous cell cancer. Further investigations are needed to assess the potential of RON-directed molecular therapy in head and neck squamous cell cancer.

Abstract 351: 2-Methoxyestradiol targets RON kinase and FLIP to inhibit epithelial-mesenchymal transition in prostate cancer

Abstract Prostate Cancer (PCA) is the second leading cause of cancer-related deaths among men in the United States. Despite significant progress in our understanding of prostate biology, early detection and treatment, the five-year survival for hormone refractory metastatic prostate cancer (HRPCA) patients is less than 30%. Current therapies targeting PCA are not effective against the metastatic stage. 2-Methoxyestradiol (2-ME2) is a metabolic product of 17-β-estradiol and is found in trace amounts in the body; it has shown anti-tumorigenic properties in multiple cancer models. Previous studies from our lab have shown that 2-ME2 can induce apoptosis in PCA cells by blocking cell cycle progression, and also inhibits PCA growth and progression in TRAMP mice. However, the precise mechanism of action of 2-ME2 has not yet been elucidated. In order to classify the mechanism behind PCA inhibition by 2-ME2, we tested its effectiveness on an array containing genes associated with epithelial-mesenchymal transition (EMT). We identified Recepteur d'Origine Nantais (RON) as one of the most significantly downregulated genes in response to 2-ME2 treatment. RON has been shown to promote cell invasiveness, migration, survivability, and proliferation in many cancers such as breast, colon, lung, and pancreatic. However, very little is known about RON's signaling mechanism in PCA. We've found RON to be highly increased in advanced stage PCA cell lines. RON knockdown shows a concomitant decrease in the expression of FLICE-like inhibitory protein (FLIP). FLIP is an anti-apoptotic protein which prevents death receptor-induced apoptotic signaling. FLIP has been found to promote EMT as well as androgen-independent PCA growth. Stimulation with the RON ligand HGF yielded elevated expression of RON and FLIP in PCA cell lines while treatment with 2-ME2 caused downregulation. Immunoprecipitation experiments showed RON to be associated with the androgen-induced proliferation inhibitor (APRIN) in PCA cells. Our data suggest that RON/FLIP crosstalk plays a role in prostate cancer. Therefore, targeting RON/FLIP signaling could have potential therapeutic benefit for metastatic PCA. Supported by NIH CA 135451 (APK). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 351. doi:1538-7445.AM2012-351

Expression and mutational status of RON in neoplastic lesions of the breast: analysis of MSP/RON signaling in ductal carcinoma in situ and invasive ductal carcinoma

Recepteur d'origine nantais (RON) is a receptor tyrosine kinase closely related to MET and involved in tumorigenesis. We investigated the roles of aberrations in RON and its ligand, macrophage-stimulating protein (MSP), in invasive ductal carcinoma (IDC, n = 81), ductal carcinoma in situ (DCIS, n = 26), and in benign lesions (n = 20) of mammary gland. Expression of RON and MSP was evaluated by immunohistochemistry and the mutational status of a region containing the proteolytic cleavage site in exon 1 and each exon of the kinase domain (exon 14-20) of RON was screened by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis. The proportion of cases positive for RON expression was significantly different between malignant [86% (92/107)] and benign [40% (8/20)] lesions. RON expression was positive in both IDC and DCIS [90% (73/81) and 73% (19/26), respectively], whereas MSP expression was present in 54% (44/81) of IDC and absent in DCIS. RON expression correlated significantly with the histological grade of DCIS. No mutations were detected in the examined regions of RON in breast cancer samples as confirmed by PCR-SSCP. The findings suggest the involvement of RON expression in the development of breast cancer, and that an autocrine/paracrine loop of RON seems to affect tumor invasiveness.

RON is associated with tumor progression via the inhibition of apoptosis and cell cycle arrest in human gastric cancer

The recepteur d'origine nantais (RON) receptor tyrosine kinase is overexpressed in epithelial cancers, including gastric cancer. The aims of the present study were to evaluate whether RON affects tumor cell behaviors and oncogenic signaling pathways, and to document the relationship of its expression with various clinicopathological parameters in gastric cancer. The biological role of RON in tumor cell behaviors and oncogenic signaling pathways was investigated by using small interfering RNA in gastric cancer cell lines including AGS and MKN28. The expression of RON in gastric cancer tissues was investigated by using reverse transcription polymerase chain reaction and immunohistochemistry. Knockdown of RON suppressed tumor cell migration and invasion in AGS and MKN28, induced apoptosis through modulation of anti-apoptotic and pre-apoptotic genes and induced cell cycle arrest by decreasing cyclin D1, cyclin D3 and CDK4, and by inducing p21 and p27 expression. Signaling cascades, including Akt and mitogen-activated protein kinase (MAPK), were significantly blocked by knockdown of RON. Expression of RON was significantly associated with tumor size, depth of invasion, lymph node metastasis, tumor stage and poor survival. These results indicate that RON is associated with tumor progression via the inhibition of apoptosis and cell cycle arrest in human gastric cancer.

Human immunodeficiency virus (HIV)-1 Tat downregulates the phosphorylation of recepteur d'origine nantais (RON) receptor tyrosine kinase induced by macrophage-stimulating protein

The aim of this study is to examine the effects of the human immunodeficiency virus (HIV)-1 Tat protein on the expression and phosphorylation of recepteur d'origine nantais (RON) receptor tyrosine kinase and the mechanisms involved. We first determined the expression levels of RON and macrophagestimulating protein (MSP) were determined in the peripheral blood of HIV-positive patients and control subjects. The 293T cells were transfected with the pDR2-RON plasmid to establish the 293T-RON cell line. The pcDNA3.1 (+)-Tat-His plasmid was constructed to obtain recombinant Tat protein. The 293TRON cells pretreated with MSP were co-cultured with the H9/HTLV-IIIB cells or were stimulated with the Tat protein; then, the change of RON expression was determined. This study revealed higher expression of RON and relatively lower expression of MSP in HIV-infected patients than in the uninfected patients. We demonstrated that HIV-1 Tat down-regulated the expression and phosphorylation of RON in 293T-RON cells. Flow cytometry analysis of 293T-RON cells revealed that RON was expressed in 293T-RON cells. The 293T-RON cells co-cultured with the H9/HTLV-IIIB cells RON expression did not change significantly, while stimulation with 500 ng/ml Tat considerably decreased RON expression in 293T-RON cells. These findings imply that Tat may play a role in modulating the function of RON, which is activated by MSP; this may provide a permissive environment for both HIV and other opportunistic microbes.