Search

RON is a receptor tyrosine kinase (RTK) of the MET receptor family that is canonically involved in mediating growth and inflammatory signaling. RON is expressed at low levels in a variety of tissues, but its overexpression and activation have been associated with malignancies in multiple tissue types and worse patient outcomes. RON and its ligand HGFL demonstrate cross-talk with other growth receptors and, consequentially, positions RON at the intersection of numerous tumorigenic signaling programs. For this reason, RON is an attractive therapeutic target in cancer research. A better understanding of homeostatic and oncogenic RON activity serves to enhance clinical insights in treating RON-expressing cancers. [ABSTRACT FROM AUTHOR]

Macrophage stimulating protein (MSP) is a multifunctional serum protein produced in the liver, belonging to the plasminogen-related kringle protein family. It exerts diverse biological functions by activating a transmembrane receptor protein-tyrosine kinase known as RON in humans and SKT in mice. MSP plays a pivotal role in innate immunity and is involved in various activities such as cell survival, migration, and phagocytosis. Elucidating the regulatory mechanisms governing MSP gene expression is of great importance. In this study, we comprehensively elucidate the molecular mechanism underlying hepatic MSP gene expression in response to alcoholism. Exposure to ethanol specifically upregulated the expression of ERRγ and MSP in the liver, while not in other organs. Liver-specific knockout of the cannabinoid receptor type 1 (CB1R), an upstream regulator of ERRγ, inhibited the alcohol-induced upregulation of MSP expression. Overexpression of ERRγ alone was sufficient to enhance MSP expression in hepatic cell lines and in mice. Conversely, knockdown of ERRγ in cell lines or liver-specific knockout of ERRγ in mice reversed ethanol-induced MSP gene expression. Promoter studies revealed the direct binding of ERRγ to the MSP gene promoter at the ERR response element (ERRE), resulting in the positive regulation of MSP gene expression in response to alcohol. This finding was further supported by ERRE-mutated MSP-luciferase reporter assays. Notably, treatment with GSK5182, an ERRγ-specific inverse agonist, significantly suppressed alcohol-induced hepatic MSP expression. Collectively, we exposed a novel mechanistic understanding of how alcohol-induced ERRγ controls the transcriptional regulation of MSP gene expression in the liver. • ERRγ is a novel transcriptional regulator of MSP. • ERRγ binds to the MSP gene promoter, thereby enhancing its transcription. • The loss of ERRγ or inhibition of ERRγ transactivation prevents alcohol-induced MSP gene expression. [ABSTRACT FROM AUTHOR]

RON is a receptor tyrosine kinase (RTK) of the MET receptor family that is canonically involved in mediating growth and inflammatory signaling. RON is expressed at low levels in a variety of tissues, but its overexpression and activation have been associated with malignancies in multiple tissue types and worse patient outcomes. RON and its ligand HGFL demonstrate cross-talk with other growth receptors and, consequentially, positions RON at the intersection of numerous tumorigenic signaling programs. For this reason, RON is an attractive therapeutic target in cancer research. A better understanding of homeostatic and oncogenic RON activity serves to enhance clinical insights in treating RON-expressing cancers.

Objective: To investigate the relationship between serum vascular adhesion protein-1 (VAP-1), macrophage stimulating protein (MSP), stromal cellderived factor-1 (SDF-1) levels and pulmonary function, inflammatory factors and quality of life in patients with stable chronic obstructive pulmonary disease (COPD). Methods: 116 patients with stable COPD in our hospital from September 2018 to September 2020 were selected as the COPD group, and 100 healthy volunteers who had physical examination in our hospital during the same period were selected as the control group. The serum VAP-1, MSP, SDF-1 levels, pulmonary function indexes [Forced expiratory volume at 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC, peak expiratory flow (PEF)], inflammatory factors [interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-22 (IL-22), tumor necrosis factor-α (TNF-α)] levels were compared between the two groups. According to the severity of patients with stable COPD, they were divided into mild group (n=53), moderate group (n=34) and severe group (n=29). The above indexes were compared among the three groups. The quality of life of the three groups was evaluated and compared by COPD assessment test (CAT), Pearson linear correlation analysis was used to analyze the correlation between serum VAP-1, MSP, SDF-1 levels and pulmonary function, inflammatory factors and CAT score. Results: The serum VAP-1, MSP, SDF-1, IL-6, IL-17, IL-22 and TNF-αlevels in COPD group were higher than those in control group, while FEV1, FVC, FEV1/FVC and PEF were lower than those in control group (P<0.05). Serum VAP-1, MSP, SDF-1, IL-6, IL-17, IL-22, TNF-α levels and CAT score in the mild group were significantly lower than those in the moderate group and severe group, and the moderate group was lower than the severe group, while FEV1, FVC, FEV1/FVC, PEF in the mild group were higher than those in the moderate group and severe group, and the moderate group was higher than the severe group (P<0.05). Pearson linear correlation analysis indicated that serum VAP-1, MSP, SDF-1 levels were negatively correlated with FEV1, FVC, FEV1/FVC, PEF, and the three were negatively correlated with serum IL-6, IL-17, IL-22, TNF-α level and CAT score were positively correlated (P<0.05). Conclusion: The serum VAP-1, MSP and SDF-1 level in patients with stable COPD are significantly up-regulated, and the three are closely related to the patient's pulmonary function, inflammatory factors and quality of life. Clinically, it is expected that the determination of serum VAP-1, MSP and SDF-1 levels, so as to assess the progress of patients with stable COPD. [ABSTRACT FROM AUTHOR]

In recent years, the application of chimeric antigen receptor T-cell (CAR-T) therapy based on gamma delta T (γδT) cells in hepatocellular carcinoma (HCC) immunotherapy has attracted more and more attention. However, specific antigens recognized by γδT cells are rarely identified, which has become the main restriction on such therapeutic application of γδT cells. In this report, we identified a new peptide and protein antigen recognized by γδT cells in HCC using our previous established strategy. First, we investigated the diversity of the γ9/δ2 T-cell immunorepertoire by sequence analyses of the expressed complementarity-determining region 3 (CDR3) in HCC patients. Then, we constructed γ9/δ2 T-cell receptor (TCR)-transfected cell lines expressing significant HCC CDR3 sequence and identified a series of peptides capable of binding to γδT cells specifically. Next, we identified, further tested and verified the biological functions of these peptides and their matched protein by bioinformatics analysis. We identified that the new protein hepatocyte growth factor-like protein, also called as macrophage-stimulating protein (MSP), and peptide HP1, not only bound to HCC-predominant γδTCR but also effectively activated γδT cells isolated from HCC patients. Moreover, they could stimulate γδT cells in peripheral blood from HCC patients to produce cytokines, which contributed to inhibiting HCC and played an important role in mediating cytotoxicity to HCC cell lines. In conclusion, we identified MSP and HP1, which showed potential as candidates for antigens recognized by γδT cells in HCC. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Background Altered expression of receptor tyrosine kinases (RTKs) is a major driver of growth and metastasis of cancers. Recepteur d’origine nantais (RON) receptor is a single-pass transmembrane RTK aberrantly expressed in a number of cancers. Efforts to block deregulated RON signaling in tumors using small molecule kinase inhibitors or antibodies are complicated by the presence of unknown number/types of isoforms of RON, which, despite having similar sequences, are localized differently and mediate varied functions. The objective of this study was to identify splice variants of RON transcripts between exons 1 and 10 that code for the extracellular region. Methods Direct cDNA sequencing was performed for the transcript between exons 1–10 of RON by Sanger sequencing in various lung cancer cell lines. Results PCR amplification and bi-directional sequencing of cDNA for section between exons 1 and 10 from lung cancer cell lines revealed the presence of several splice variants of RON transcripts; the variants were formed by skipping of exons 2, 2–3, 5–6, 6 and 8–9. Each of these transcript variants were found in one or more cell lines. While the variants formed by skipping of exons 2, 2–3 and 5–6 resulted in loss of 63, 106 and 109 amino acids, respectively, and didn’t cause reading-frameshift, the transcripts formed by skipping of exons 6 and 8–9 caused reading-frameshift. Splice variant lacking exons 8–9 was found in 13 out of 23 cell lines tested. Conclusion Lung cancer cell lines contain several splice variants of RON which involve skipping of exons coding for extracellular region. Some of the splicing changes result in reading-frameshift and the N-terminally truncated isoforms are expected to be secreted out. The ubiquitous nature of alternative splicing events in RON suggests the need for isoform specific approaches to functional analysis and therapeutic targeting of RON.

Blood brain barrier (BBB) disruption is an important contributor to brain edema and neurological deficits following intracerebral hemorrhage (ICH). Macrophage stimulating protein (MSP) is a hepatocyte growth factor-like protein that mediates its functions via activating receptor tyrosine kinase recepteur d'origine nantais (RON). Grb2-associated binder 1 (GAB1) is a docking protein that mediates downstream receptor signal transduction pathways. This study aimed to evaluate the role of MSP and RON activated signaling pathway in preserving BBB integrity after collagenase-induced ICH. ICH mice received recombinant human MSP (rhMSP) or rhMSP combined with siRNA knockdown of RON or GAB1. rhMSP was administered by intranasal route 1 h after ICH. Brain edema, neurobehavior, BBB tight junction protein expression, and BBB permeability were evaluated. The expression of endogenous MSP and p-RON was decreased after ICH. Exogenous rhMSP administration reduced brain edema, neurological deficits, BBB permeability, and increased the expression of tight junction proteins in ICH mice. rhMSP administration increased the expression of p-RON, p-GAB1, p-Src, nuclear b-catenin, and tight junction proteins after ICH. These effects were reversed with RON and GAB1 siRNA. We conclude that MSP activation of RON preserved BBB integrity via GAB-1/Src/b-catenin pathway, thereby reducing brain edema and neurological deficits after ICH in mice. [ABSTRACT FROM AUTHOR]

Background In former studies we showed in a rat model of renal transplantation that Mesenchymal Stromal Cells (MSC) prevent acute rejection in an independent way of their endowing in the graft. In this study we investigated whether MSC operate by resetting cytokine network and Scatter Factor systems, i.e. Hepatocyte Growth Factor (HGF), Macrophage Stimulating Protein (MSP) and their receptors Met and RON, respectively. Methods MSC were injected into the renal artery soon after reperfusion. Controls were grafted untreated and normal rats. Rats were sacrificed 7 days after grafting. Serum and renal tissue levels of IFN-γ, IL-1, IL-2, IL-4, IL-6, IL-10, MSP/RON, HGF/Met systems, Treg lymphocytes were investigated. Results In grafted untreated rats IFN-γ increased in serum and renal tissue and IL-6 rose in serum. MSC prevented both the phenomena, increased IL-10 serum levels and Treg number in the graft. Furthermore MSC increased serum and tissue HGF levels, Met tubular expression and prevented the suppression of tubular MSP/RON expression. Conclusions Our results demonstrate that MSC modify cytokine network to a tolerogenic setting, they suppress Th1 cells, inactivate monocytes/macrophage, recruit Tregs. In addition, MSC sustain the expression of the Scatter Factor systems expression, i.e. systems that are committed to defend survival and stimulate regeneration of tubular cells. [ABSTRACT FROM AUTHOR]

The organ microenvironment significantly affects the processes of cancer metastasis. Elucidating the molecular mechanisms of interaction between tumor cells and the organ microenvironment is crucial for the development of effective therapeutic strategies to eradicate cancer metastases. Macrophage stimulating protein (MSP), an activator of macrophages, regulates a pleiotropic array of effects, including proliferation, cellular motility, invasiveness, angiogenesis, and resistance to anoikis. However, the role of MSP in cancer metastasis is still largely unknown. In this study, the action of MSP on the production of metastases was determined in a multiple-organ metastasis model. The murine MSP gene was transfected into two human SCLC cell lines, SBC-5 and H1048, to establish transfectants secreting biologically active MSP. MSP gene transduction did not affect cell proliferation and motility in vitro. Intravenously inoculated MSP transfectants produced significantly larger numbers of liver metastases than parental cells or vector control clones, while there were no significant differences in bone or lung metastases among them. Immunohistochemical analyses of liver metastases revealed that tumor-associated microvessel density and tumor-infiltrating macrophages were significantly increased in lesions produced by MSP transfectants. MSP could stimulate the migration of murine macrophages and endothelial cells in vitro. Consequently, MSP may be one of the major determinants that affects the properties of tumor stroma and that produces a permissive microenvironment to promote cancer metastasis. [ABSTRACT FROM AUTHOR]

Heterogeneous receptor-receptor interactions may play a role in intracellular signaling. Accordingly, the interaction of two dissimilar tyrosine kinase receptors, Ron and epidermal growth factor receptor (EGFR) was investigated. The functional interaction of Ron and EGFR in cell scatter and oncogenic transformation was investigated in vivo. Transfection of a dominant negative form of EGFR into human embryonic kidney cells stably expressing Ron (293-Ron) dramatically reduced the scatter response induced by the Ron ligand hepatocyte growth factor-like protein/macrophage stimulating protein (HGFL). The scatter response of the 293-Ron cells was also attenuated by treatment of the cells with the specific EGFR inhibitor AG 1478. Co-transfection of Ron and dominant-negative EGFR, or co-transfection of EGFR and a dominant-negative form of Ron reduced focus formation in NIH/3T3 cells. Western analysis of NIH/3T3 cells overexpressing murine Ron and expressing endogenous levels of EGFR was used to demonstrate that Ron and EGFR co-immunoprecipitate. Stimulation of the cells in vitro with the Ron ligand HGFL or with the EGFR ligand epidermal growth factor (EGF) appeared to induce phosphorylation of both receptors. Co-immunoprecipitation and phosphorylation of phosphatidyl inositol 3-kinase (PI3-K) was also observed. This novel finding of a functional and biochemical interaction between Ron and EGFR suggests that heterologous tyrosine kinase receptor interactions may play a role in cellular processes such as scatter and transformation. [Copyright &y& Elsevier]

RON is a member of the receptor tyrosine kinase gene family that includes the MET oncogene, whose germline mutations have been causally related to human tumorigenesis. In vitro, RON and MET receptors cross-talk, synergize in intracellular signaling, and cooperate in inducing morphogenic responses. Here we show that the RON and MET oncogenes were expressed in 55% and 56% of human ovarian carcinomas, respectively, and were significantly coexpressed in 42% (P < 0.001). In ovarian carcinoma samples and cell lines we did not find mutations in RON and MET gene kinase domain, nor coexpression of RON and MET receptor ligands (MSP and HGF, respectively). We show that motility and invasiveness of ovarian cancer cells coexpressing MET and RON receptors were elicited by HGF and, to a lesser extent, by MSP. More interestingly, invasion of both reconstituted basement membrane and collagen gel was greatly enhanced by the simultaneous addition of the two ligands. These data suggest that coexpression of the MET and RON receptors confer a selective advantage to ovarian cancer cells and might promote ovarian cancer progression. [Copyright &y& Elsevier]

Background: Macrophage-stimulating protein (MSP; also known as macrophage stimulating 1 and hepatocyte growth factor-like protein) has been shown to play a crucial role in calcium homeostasis and skeletal mineralization in zebrafish. However, the precise role of MSP in osteoblasts has not been elucidated. In this study, we investigated the effect of MSP on osteoblast differentiation of pre-osteoblast cells., Methods: Osteoblast differentiation upon MSP treatment was evaluated by analyzing the osteogenic gene expression, alkaline phosphatase (ALP) activity, and mineralized nodule formation. To assess changes in the MSP-RON signaling pathway, knockdown of Ron gene was performed using siRNA and pharmacological inhibitor treatment., Results: Expression of the tyrosine kinase receptor RON, a receptor of MSP, was found to be significantly increased during osteoblast differentiation. MSP treatment significantly upregulated the expression of osteogenic marker genes and remarkably increased ALP activity and mineralized nodule formation. Conversely, knockdown of Ron significantly attenuated the expression of osteogenic marker genes and ALP activity that were induced upon MSP treatment. Mechanistically, MSP treatment significantly enhanced the phosphorylation of extracellular signal-regulated kinase (ERK); however, additional treatment with the selective ERK inhibitor PD98059 attenuated the effect of MSP on osteoblast differentiation., Conclusions: Altogether, these results indicate that the MSP-RON axis is involved in promoting osteoblast differentiation via activation of the ERK signaling pathway.

Blood brain barrier (BBB) disruption is an important contributor to brain edema and neurological deficits following intracerebral hemorrhage (ICH). Macrophage stimulating protein (MSP) is a hepatocyte growth factor-like protein that mediates its functions via activating receptor tyrosine kinase recepteur d'origine nantais (RON). Grb2-associated binder 1 (GAB1) is a docking protein that mediates downstream receptor signal transduction pathways. This study aimed to evaluate the role of MSP and RON activated signaling pathway in preserving BBB integrity after collagenase-induced ICH. ICH mice received recombinant human MSP (rhMSP) or rhMSP combined with siRNA knockdown of RON or GAB1. rhMSP was administered by intranasal route 1 h after ICH. Brain edema, neurobehavior, BBB tight junction protein expression, and BBB permeability were evaluated. The expression of endogenous MSP and p-RON was decreased after ICH. Exogenous rhMSP administration reduced brain edema, neurological deficits, BBB permeability, and increased the expression of tight junction proteins in ICH mice. rhMSP administration increased the expression of p-RON, p-GAB1, p-Src, nuclear β-catenin, and tight junction proteins after ICH. These effects were reversed with RON and GAB1 siRNA. We conclude that MSP activation of RON preserved BBB integrity via GAB-1/Src/β-catenin pathway, thereby reducing brain edema and neurological deficits after ICH in mice., (© 2018 International Society for Neurochemistry.)

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., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Objective: To study the effect of macrophage stimulating protein (MSP) on the cell cycle of non-small cell lung cancer PC14 cells without expression of recepteur d'originenanta (RON) and MSP,and analyse its effect on PC14's epithelial mesenchymal transition (EMT) capacity., Methods: Vitro culture PC14 (blank control),PC14-Mst1-pEGFP-N1 (stablely expressed MSP) and PC14-pEGFP-N1. Cell cycles were detected by flow cytometry and the gaps between cells during growth were measured by transmission electron microscope (TEM); RT-PCR and Western blot were used to figure out the shifts of EMT related gene expression in PC14-Mst1-pEGFP-N1 cells., Results: Compared with the PC14 group and PC14-pEGFP-N1 group,PC14-Mst1-pEGFP-N1 population of G1/G0 phase were significantly increased while S and G2/M phase were significantly reduced;The gaps between PC14-Mst1-pEGFP-N1 cells decreased; RT-PCR and Western blot showed that mRNA and protein levels of E-cadherin of PC14-Mst1-pEGFP-N1 were significantly higher than that of PC14,but mRNA and protein levels of Vimentin were significantly lower., Conclusion: MSP may affect the cell cycle of PC14 and inhibit its EMT procedure by regulating the expression of related proteins including E-cadherin and Vimentin when RON was not expressed., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Science Edition).)

Background: Altered expression of receptor tyrosine kinases (RTKs) is a major driver of growth and metastasis of cancers. Recepteur d'origine nantais (RON) receptor is a single-pass transmembrane RTK aberrantly expressed in a number of cancers. Efforts to block deregulated RON signaling in tumors using small molecule kinase inhibitors or antibodies are complicated by the presence of unknown number/types of isoforms of RON, which, despite having similar sequences, are localized differently and mediate varied functions. The objective of this study was to identify splice variants of RON transcripts between exons 1 and 10 that code for the extracellular region., Methods: Direct cDNA sequencing was performed for the transcript between exons 1-10 of RON by Sanger sequencing in various lung cancer cell lines., Results: PCR amplification and bi-directional sequencing of cDNA for section between exons 1 and 10 from lung cancer cell lines revealed the presence of several splice variants of RON transcripts; the variants were formed by skipping of exons 2, 2-3, 5-6, 6 and 8-9. Each of these transcript variants were found in one or more cell lines. While the variants formed by skipping of exons 2, 2-3 and 5-6 resulted in loss of 63, 106 and 109 amino acids, respectively, and didn't cause reading-frameshift, the transcripts formed by skipping of exons 6 and 8-9 caused reading-frameshift. Splice variant lacking exons 8-9 was found in 13 out of 23 cell lines tested., Conclusion: Lung cancer cell lines contain several splice variants of RON which involve skipping of exons coding for extracellular region. Some of the splicing changes result in reading-frameshift and the N-terminally truncated isoforms are expected to be secreted out. The ubiquitous nature of alternative splicing events in RON suggests the need for isoform specific approaches to functional analysis and therapeutic targeting of RON.

Objectives: To determine the effects of macrophage stimulating protein (Msp) on the proliferation, migration and invasion of human non-small cell lung cancer cells PC14., Methods: The eukaryotic expression vector for st1 was constructed and transfected into Msp(-)and RON(-)human non-small cell lung cancer cells PC14. The expression of st1 mRNA in PC14 cells was observed by RT-PCR. The expression levels of Msp protein in PC14, PC14- st1 -pEGFP-N1 and PC14-pEGFP-N1 groups as well as the expression of RON in PC14 and SKBR-3 cells were detected by Western blot. RAW264.7 (mouse monocyte macrophage) and SKBR-3 cells were cultured in the supernatant of cells(PC14, PC14- st1 -pEGFP-N1and PC14-pEGFP-N1 groups)and tested with Transwell microporous membrane, through which the biologic activity of Msp was evaluated by calculating the cell number migrated. The proliferation of PC14 was measured by MTT assay. The capabilities of PC14 to migrate and invade were measured by Transwell chamber and Matrigel invasion tests, respectively., Results: The expressions of mRNA and protein of Mst1 in PC14 were stable after transfection with Mst1. Msp (PC14- st1 -pEGFP-N1 group) promoted the migration of RON (+) cells (SKBR-3 and RAW264.7). Compared with PC14 and PC14-pEGFP-N1 groups, the proliferation, migration and invasion of PC14 cells in PC14- st1 -pEGFP-N1 group were inhibited significantly., Conclusions: Msp can promote the migration of RON (+) cancer cells in paracrine secretion manner and inhibit the proliferation, migration and invasion of human non-small cell lung cancer cells PC14 in an unknown way.

Background: Aberrant expression of RON, a MET family receptor tyrosine kinase, has been correlated to tumor growth and metastasis. Intense research efforts are on to target RON using small molecule tyrosine kinase inhibitors or specific antibodies. However, progress towards specific targeting of RON is hampered by a lack of understanding of the nature and number of isoforms of RON expressed by tumors. We hypothesize that formation of different isoforms via alternative splicing may be fundamental to the tumor promoting functions associated with aberrantly expressed RON in cancers., Methods: In this study, we analyzed the transcript sequence variations caused by alternative splicing in the C-terminal region of RON cDNA by PCR amplification and sequencing of five small cell lung carcinoma (SCLC) and seven non-small cell lung carcinoma (NSCLC) cell lines., Results: Results revealed the presence of two alternatively spliced variants, each caused by unique exon(s) deletion: a previously known transcript variant lacking exon 19 and a novel one lacking exons 18+19. The two alternatively spliced variants together with the wild-type transcript were detected in each of the 12 lung cancer cell lines analyzed. Combined loss of exons 18+19 results in an in-frame deletion of 303 nucleotides corresponding to 101 amino acids of the tyrosine kinase domain. Translation products of transcript variants lacking exons 18 and 19 are expected to dominant negatively inhibit ligand stimulated RON signaling., Conclusions: The ubiquitous presence of alternatively spliced transcripts and their translation products may affect quantitative expression analysis, either by immunological or PCR methods, by interfering with estimation of normal RON, leading to exaggerated values. Besides, RON isoforms with dominant negative activities may interfere with siRNA based functional analysis of wild-type RON.

Objective: To investigate the roles of macrophage stimulating protein (MSP) and its tyrosine kinase receptor RON in smoke-induced airway inflammation of rats., Methods: Inhalation of combustion smoke was administered in rats to induce airway inflammation. Alveolar macrophages (AM) of healthy and smoking rats were isolated at different time points, cultured and then treated with different concentrations of MSP for 24 h., Results: When compared with healthy rats, MSP increased in the serum and bronchoalveolar lavage fluid (BALF) of smoking rats in a time dependent manner. In smoking rats, the RON expression in the lung and AM was higher than in healthy rats, and these increases were time dependent. MSP stimulated the production of malondialdehyde (MDA) and reduced superoxide dismutase (SOD) activity in rat AM cells in a dose dependent manner. MSP also stimulated the release of inflammatory factors TNF-α, IL-8, IL-1β and IL-10 in rat AM in a dose-dependent manner. Moreover, at the same MSP concentration, the contents of MDA, TNF-α, IL-8 and IL-1β in the AM of smoking rates were higher than in healthy rats, while the IL-10 content and SOD activity were lower than in healthy rats., Conclusion: MSP and its receptor RON are involved in the smoke-induced airway inflammation in rats via promoting AM to release inflammatory cytokines and inducing the increase of oxygen free radical.