Identification of short-form RON as a novel intrinsic resistance mechanism for anti-MET therapy in MET-positive gastric cancer.
ABSTRACT: Despite the promising results from initial studies, there are significant limitations in the application of MET-targeted therapy in gastric cancer. Intrinsic resistance is one of the major obstacles. The aim of this study is to identify the responsible receptor tyrosine kinases (RTKs) that determine the unresponsiveness of MET inhibitor in MET-positive gastric cancer. through an RNA-interference-based functional screen targeting most human RTKs, we identified that activation of the fibroblast growth factor receptor 2 (FGFR2) and recepteur d'origine nantais (RON) pathways attenuated MET inhibitor-induced suppression of cell proliferation and migration. Notably, in the two forms of RON pathway activation, only upregulation of short-form RON (sf-RON), but not stimulation of full length RON with macrophage stimulating protein, conferred MET inhibitor resistance in vitro and in vivo. Furthermore, the profile of the gastric cancer samples observed that sf-RON was frequently upregulated in MET-positive gastric cancer. Our findings indicate that activation of the sf-RON signaling pathway represents a novel mechanism underlying MET inhibitor unresponsiveness. A combination strategy with drugs targeting both RON and MET pathways is believed to improve the efficacy of MET-targeted therapy.
Project description:In the scenario of personalized medicine, targeted therapies are currently the focus of cancer drug development. These drugs can block the growth and spread of tumor cells by interfering with key molecules involved in malignancy, such as receptor tyrosine kinases (RTKs). MET and Recepteur d'Origine Nantais (RON), which are RTKs frequently overactivated in gastric cancer, are glycoprotein receptors whose activation have been shown to be modulated by the cellular glycosylation. In this work, we address the role of sialylation in gastric cancer therapy using an innovative 3D high-throughput cell culture methodology that mimics better the in vivo tumor features. We evaluate the response to targeted treatment of glycoengineered gastric cancer cell models overexpressing the sialyltransferases ST3GAL4 or ST3GAL6 by subjecting 3D spheroids to the tyrosine kinase inhibitor crizotinib. We show here that 3D spheroids of ST3GAL4 or ST3GAL6 overexpressing MKN45 gastric cancer cells are less affected by the inhibitor. In addition, we disclose a potential compensatory pathway via activation of the Insulin Receptor upon crizotinib treatment. Our results suggest that cell sialylation, in addition of being involved in tumor progression, could play a critical role in the response to tyrosine kinase inhibitors in gastric cancer.
Project description:Recepteur d'origine nantais (RON) has been implicated in cell proliferation, metastasis, and chemoresistance of various human malignancies. The short-form RON (sf-RON) encoded by RON transcripts was overexpressed in gastric cancer tissues, but its regulatory functions remain illustrated. Here, we found that sf-RON promoted gastric cancer cell proliferation by enhancing glucose metabolism. Furthermore, sf-RON was proved to induce the ?-catenin expression level through the AKT1/GSK3? signaling pathway. Meanwhile, the binding sites of ?-catenin were identified in the promoter region of SIX1 and it was also demonstrated that ?-catenin positively regulated SIX1 expression. SIX1 enhanced the promoter activity of key proteins in glucose metabolism, such as GLUT1 and LDHA. Results indicated that sf-RON regulated the cell proliferation and glucose metabolism of gastric cancer by participating in a sf-RON/?-catenin/SIX1 signaling axis and had significant implications for choosing the therapeutic target of gastric cancer.
Project description:RON (recepteur d'origine nantais) and MET (hepatocyte growth factor receptor) are tyrosine kinase receptors. Various cancers have aberrant RON and MET expression and activation, which contribute to cancer cell proliferation, invasiveness, and metastasis. Here, we explored RON and MET expression in pancreatic cancer and their relationship with overall survival (OS) time, and evaluated their significance as therapeutic targets of tyrosine kinase inhibitors in pancreatic cancer. We enrolled 227 patients with pancreatic cancer in the study. RON and MET expression was analyzed by immunohistochemical staining. Four human pancreatic cancer cell lines expressing variable levels of RON or MET and four MET superfamily inhibitors (BMS777607, PHA665752, INCB28060, Tivantinib) were used. The effect of the four tyrosine kinase inhibitors on cell viability, migration, and apoptosis were determined using cell viability, scratch wound healing, and Caspase-Glo 3/7 assays. Cellular signaling was analyzed by immunoprecipitation and western blotting. The therapeutic efficacy of the tyrosine kinase inhibitors was determined with mouse xenograft pancreatic cancer models in vivo. There was wide aberrant RON and MET expression in the cancer tissues. In 227 pancreatic cancer samples, 33% had RON overexpression, 41% had MET overexpression, and 15.4% had RON and MET co-overexpression. RON and MET expression were highly correlated. RON and MET expression levels were significantly related to OS. Patients with RON and MET co-overexpression had poorer OS. BMS777607 and PHA665752 inhibited pancreatic cancer cell viability and migration, and promoted apoptosis by inhibiting RON and MET phosphorylation and further inhibiting the downstream signaling pathways in vitro. They also inhibited tumor growth and further inhibited phosphorylated (phosphor)-RON and phospho-MET expression in the mouse xenograft models in vivo effectively. INCB28060, which inhibits the MET signaling pathway alone, was not effective. RON and MET can be important indicators of prognosis in pancreatic cancer. Tyrosine kinase inhibitors targeting RON and MET in pancreatic cancer are a novel and potential approach for pancreatic cancer therapy.
Project description:Constitutively active receptor tyrosine kinases (RTKs) are known oncogenic drivers and provide valuable therapeutic targets in many cancer types. However, clinical efficacy of RTK inhibitors is limited by intrinsic and acquired resistance. To identify genes conferring resistance to inhibition of the MET RTK, we conducted a forward genetics screen in the GTL-16 gastric cancer cell line, carrying MET amplification and exquisitely sensitive to MET inhibition. Cells were transduced with three different retroviral cDNA expression libraries and selected for growth in the presence of the MET inhibitor PHA-665752. Selected cells displayed robust and reproducible enrichment of library-derived cDNAs encoding truncated forms of RAF1 and BRAF proteins, whose silencing reversed the resistant phenotype. Transduction of naïve GTL-16 cells with truncated, but not full length, RAF1 and BRAF conferred in vitro and in vivo resistance to MET inhibitors, which could be reversed by MEK inhibition. Induction of resistance by truncated RAFs was confirmed in other MET-addicted cell lines, and further extended to EGFR-addicted cells. These data show that truncated RAF1 and BRAF proteins, recently described as products of genomic rearrangements in gastric cancer and other malignancies, have the ability to render neoplastic cells resistant to RTK-targeted therapy.
Project description:Lung cancer is a heterogeneous disease encompassing a wide array of genetic abnormalities. The MET receptor tyrosine kinase is altered in many lung cancers, especially non-small cell lung cancer (NSCLC), and clinical trials of MET inhibitors that are under way are documenting cases of acquired resistance. On the basis of the evidence that the RON tyrosine kinase receptor can also be overexpressed in NSCLC, we evaluated the potent MET/RON dual kinase inhibitor LY2801653 in this setting. LY2801653 was more efficacious than the MET/ALK/RON/ROS inhibitor crizotinib with a distinct pattern of downstream signaling effects. Using the PamGene platform, we found that inhibition of MET and RON was associated with decreased phosphorylation of CBL, PI3K, and STAT3. In classic and orthotopic mouse xenograft models of lung cancer, LY2801653 decreased tumor growth, dramatically inhibiting mitotic events and angiogenesis. Taken together, our results argued that specific targeting of the MET/RON kinases could provide robust inhibition of cell proliferation and tumor outgrowth in multiple in vitro and in vivo models of NSCLC. These findings offer a robust preclinical proof of concept for MET/RON targeting by LY2801653 as a promising small-molecule modality to treat NSCLC.
Project description:Strict regulation of signaling by receptor tyrosine kinases (RTKs) is essential for normal biological processes, and disruption of this regulation can lead to tumor initiation and progression. Signal duration by the Met RTK is mediated in part by the E3 ligase Cbl. Cbl is recruited to Met upon kinase activation and promotes ubiquitination, trafficking, and degradation of the receptor. The Met RTK has been demonstrated to play a role in various types of cancer. Here, we show that Met-dependent loss of Cbl protein in MET-amplified gastric cancer cell lines represents another mechanism contributing to signal dysregulation. Loss of Cbl protein is dependent on Met kinase activity and is partially rescued with a proteasome inhibitor, lactacystin. Moreover, Cbl loss not only uncouples Met from Cbl-mediated negative regulation but also releases other Cbl targets, such as the EGF receptor, from Cbl-mediated signal attenuation. Thus, Met-dependent Cbl loss may also promote cross-talk through indirect enhancement of EGF receptor signaling.
Project description:Pancreatic cancer is an aggressive disease with a poor prognosis for which current standard chemotherapeutic treatment options offer little survival benefit. In recent years, receptor tyrosine kinases (RTK)s have garnered interest as therapeutic targets to augment or replace standard chemotherapeutic therapies because of their high expression levels in various cancers and their ability to promote cell growth, migration, and survival. Met and Ron, which are homologous RTKs activated by the ligands hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP), respectively, are over-activated in many of the least treatable cancers. In pancreatic adenocarcinoma, Met expression is linked to poor patient survival and Ron expression is generally higher in tumor samples relative to normal tissue, although its prognostic significance in pancreatic cancer remains unclear. Despite the structural 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 pancreatic cancer cells in vitro. We found HGF and MSP both encouraged cell migration and activated the MAPK/Erk pathway both at the transcript and protein level. HGF uniquely increased proliferation in addition to regulating a wider variety of transcripts compared to MSP. Although HGF and MSP produced a differing breadth of responses, overlapping pro-cancer signaling, behavioral, and transcriptional effects suggest dual inhibition of the MSP/Ron and HGF/Met systems in pancreatic cancer may provide a more complete anti-cancer effect compared to individually targeting either system. Overall design: BxPC-3 cells were treated with vehicle control (PBS), HGF (80 ng/ml), or MSP (100 ng/ml) in triplicate. Total RNA was collected at 1 and 4 hours post-treatment. Libraries were prepped with a KAPA mRNA HyperPrep Kit. Libraries were sequenced on an Illumina HiSeq 4000. All samples were sequenced in duplicate across two lanes.
Project description:The recepteur d'origine nantais (RON) is a receptor tyrosine kinase (RTK) in the scatter factor family, which includes the c-Met receptor. RON exhibits increased expression in a significant number of human breast cancer tissues as well as in many established breast cancer cell lines. Recent studies have indicated that in addition to ligand-dependent signaling events, RON also promotes signals in the absence of its only known ligand, MSP, when expressed in epithelial cells. In this study, we found that when expressed in MCF-10A breast epithelial cells, RON exhibits both MSP-dependent and MSP-independent signaling, which lead to distinct biological outcomes. In the absence of MSP, RON signaling promotes cell survival, increased cell spreading and enhanced migration in response to other growth factors. However, both RON-mediated proliferation and migration require the addition of MSP in MCF-10A cells. Both MSP-dependent and MSP-independent signaling by RON are mediated in part by Src family kinases. These data suggest that RON has two alternative modes of signaling that can contribute to oncogenic behavior in normal breast epithelial cells.
Project description:In this study, the role of RON (receptor originated from nantes) in tumor progression was further investigated in context with MET expression and activity. RON and MET expressions were not detected in an immortalized normal human pancreas cell line (HPNE), but were co-expressed in five of seven pancreatic ductal adenocarcinoma (PDAC) cell lines (PANC-1, BxPC-3, Capan-2, CFPAC-1 and AsPC-1). RON expression was knocked down by an shRNA approach in two PDAC cell lines (BxPC-3 and CFPAC-1) that co-express MET. Knockdown of RON significantly inhibited cell growth, clonogenicity and macrophage stimulating protein (MSP), RON ligand induced invasion by in vitro assays and significantly inhibited tumor growth (P<0.001) and metastasis (P<0.009) in an orthotopic pancreatic cancer mouse model at week 7. However, by week 9, the mice implanted with RON knockdown cells had developed similar size primary tumors and metastases compared with that seen in the control group at week 7. Western blotting and immunohistochemistry analyses showed that MET remains highly expressed in cells and tumor tissues where RON was knocked down. Moreover, knockdown of RON did not prevent hepatocyte growth factor (HGF) stimulated invasion in in vitro Matrigel assays. Treating cells with MSP induced the transphosphorylation of MET, suggesting that signaling may be modulated by relative levels of RON and MET receptors and their corresponding ligands. To this point, HGF treatment of RON knockdown cells caused an increase in intensity and duration of MET signaling, suggesting that MET signaling may compensate for loss of RON signaling. Treatment of cells with an MET inhibitor, PHA-665752, had minimal effects on inhibiting cell growth but significantly inhibited cell invasion induce by ligands for either MET or RON. These results suggest that HGF/MET signaling may have a more important role in tumor cell invasion and metastasis rather than in tumor cell proliferation. This study indicates that specific inhibition of RON delays but does not prevent progression of PDAC. Moreover, specific signaling may be modulated by the interaction of RON and MET receptors. This dynamic interaction of RON and MET in pancreatic cancer cells suggests that dual targeting of both RON and MET will be preferable to inhibition of either target alone.
Project description: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.Direct cDNA sequencing was performed for the transcript between exons 1-10 of RON by Sanger sequencing in various lung cancer cell lines.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.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.