A novel RON splice variant lacking exon 2 activates the PI3K/AKT pathway via PTEN phosphorylation in colorectal carcinoma cells

Regulation of Epithelial-Mesenchymal Transitions by Alternative Splicing: Potential New Area for Cancer Therapeutics

The epithelial-mesenchymal transition (EMT) is a complicated biological process in which cells with epithelial phenotype are transformed into mesenchymal cells with loss of cell polarity and cell-cell adhesion and gain of the ability to migrate. EMT and the reverse mesenchymal-epithelial transitions (METs) are present during cancer progression and metastasis. Using the dynamic switch between EMT and MET, tumour cells can migrate to neighbouring organs or metastasize in the distance and develop resistance to traditional chemotherapy and targeted drug treatments. Growing evidence shows that reversing or inhibiting EMT may be an advantageous approach for suppressing the migration of tumour cells or distant metastasis. Among different levels of modulation of EMT, alternative splicing (AS) plays an important role. An in-depth understanding of the role of AS and EMT in cancer is not only helpful to better understand the occurrence and regulation of EMT in cancer progression, but also may provide new therapeutic strategies. This review will present and discuss various splice variants and splicing factors that have been shown to play a crucial role in EMT.

Discovery of Novel, Thienopyridine-Based Tyrosine Kinase Inhibitors Targeting Tumorigenic RON Splice Variants

Herein, we report the identification, structural optimization, and biological efficacy of thieno[2,3-b]pyridines as potent inhibitors of splice variants of the tyrosine kinase recepteur d'origine nantais (RON). Among synthesized compounds, compound 15f exhibited excellent in vitro kinase inhibition and antiproliferative activity, as well as in vivo antineoplastic efficacy against RON splice variant-expressing tumors. Moreover, compound 15f with excellent pharmacokinetics demonstrated significant activity with greater tumor growth inhibition (74.9% at 10 mg/kg) than compounds 2 and 4 in a patient-derived xenograft model. Collectively, 15f represents a promising, novel anticancer agent targeting RON splice variants.

A network map of macrophage-stimulating protein (MSP) signaling

Macrophage-stimulating protein (MSP), a serum-derived growth factor belonging to the plasminogen-related kringle domain family, is mainly produced by the liver and released into the blood. MSP is the only known ligand for RON ("Recepteur d'Origine Nantais", also known as MST1R), which is a member of the receptor tyrosine kinase (RTK) family. MSP is associated with many pathological conditions, including cancer, inflammation, and fibrosis. Activation of the MSP/RON system regulates main downstream signaling pathways, including phosphatidylinositol 3-kinase/ AKT serine/threonine kinase/ (PI3-K/AKT), mitogen-activated protein kinases (MAPK), c-Jun N-terminal kinase (JNK) & Focal adhesion kinase (FAK). These pathways are mainly involved in cell proliferation, survival, migration, invasion, angiogenesis & chemoresistance. In this work, we created a pathway resource of signaling events mediated by MSP/RON considering its contribution to diseases. We provide an integrated pathway reaction map of MSP/RON that is composed of 113 proteins and 26 reactions based on the curation of data from the published literature. The consolidated pathway map of MSP/RON mediated signaling events contains seven molecular associations, 44 enzyme catalysis, 24 activation/inhibition, six translocation events, 38 gene regulation events, and forty-two protein expression events. The MSP/RON signaling pathway map can be freely accessible through the WikiPathways Database URL: https://classic.wikipathways.org/index.php/Pathway:WP5353 .

Targeted splicing therapy: new strategies for colorectal cancer

RNA splicing is the process of forming mature mRNA, which is an essential phase necessary for gene expression and controls many aspects of cell proliferation, survival, and differentiation. Abnormal gene-splicing events are closely related to the development of tumors, and the generation of oncogenic isoform in splicing can promote tumor progression. As a main process of tumor-specific splicing variants, alternative splicing (AS) can promote tumor progression by increasing the production of oncogenic splicing isoforms and/or reducing the production of normal splicing isoforms. This is the focus of current research on the regulation of aberrant tumor splicing. So far, AS has been found to be associated with various aspects of tumor biology, including cell proliferation and invasion, resistance to apoptosis, and sensitivity to different chemotherapeutic drugs. This article will review the abnormal splicing events in colorectal cancer (CRC), especially the tumor-associated splicing variants arising from AS, aiming to offer an insight into CRC-targeted splicing therapy.

The effect of splicing MST1R in gastric cancer was enhanced by lncRNA FENDRR

Gastric cancer (GC) poses a serious threat to human health worldwide. Serine/arginine rich splicing factor 1 (SRSF1) has been reported to serve regulatory roles during the tumorigenesis of GC. In addition, the macrophage stimulating 1 receptor (MST1R) signaling pathway was found to participate in the progression of GC. However, the association between MST1R and SRSF1 in the tumorigenesis of GC remains unclear. The expression levels of MST1R and the recepteur d'origine nantais (RON) Δ160 splicing variant were analyzed in cells using western blotting and immunofluorescence staining. Co-immunoprecipitation assays were used to investigate the interaction between SRSF1 and MST1R. A Cell Counting Kit-8 assay was performed to analyze cell viability. Flow cytometry and Transwell assays were used to determine cell apoptosis and invasiveness levels. The potential interaction between SFSR1 and long non-coding RNAs (lncRNAs) was investigated with an online bioinformatics tool. The findings of the present study revealed that the expression levels of MST1R and RON Δ160 were significantly upregulated in GC Kato III cells. SRSF1 was found to be regulated by the lncRNA FOXF1 adjacent non-coding developmental regulatory RNA (FENDRR). The knockdown of SRSF1 or FENDRR downregulated the expression levels of MST1R in Kato III cells. In addition, the expression levels of RON Δ160 were markedly downregulated in Kato III cells following the knockdown of FENDRR. Meanwhile, SRSF1 directly bound to MST1R, while this phenomenon was partially reversed by FENDRR short interfering RNA. FENDRR could interact with SRSF1 in Kato III cells and the knockdown of FENDRR also induced the apoptosis of GC cells. In conclusion, the findings of the present study suggested that the lncRNA FENDRR may function as an oncogene during the progression of GC by regulating alternative splicing of MST1R and SRSF1 expression levels. lncRNA FENDRR may serve as a potential marker for the diagnosis or target for the treatment of GC.

Nonsense-mediated RNA decay and its bipolar function in cancer

Nonsense-mediated decay (NMD) was first described as a quality-control mechanism that targets and rapidly degrades aberrant mRNAs carrying premature termination codons (PTCs). However, it was found that NMD also degrades a significant number of normal transcripts, thus arising as a mechanism of gene expression regulation. Based on these important functions, NMD regulates several biological processes and is involved in the pathophysiology of a plethora of human genetic diseases, including cancer. The present review aims to discuss the paradoxical, pro- and anti-tumorigenic roles of NMD, and how cancer cells have exploited both functions to potentiate the disease. Considering recent genetic and bioinformatic studies, we also provide a comprehensive overview of the present knowledge of the advantages and disadvantages of different NMD modulation-based approaches in cancer therapy, reflecting on the challenges imposed by the complexity of this disease. Furthermore, we discuss significant advances in the recent years providing new perspectives on the implications of aberrant NMD-escaping frameshifted transcripts in personalized immunotherapy design and predictive biomarker optimization. A better understanding of how NMD differentially impacts tumor cells according to their own genetic identity will certainly allow for the application of novel and more effective personalized treatments in the near future.

Epigenetic Mechanisms Are Involved in the Oncogenic Properties of ZNF518B in Colorectal Cancer

Simple Summary

The ZNF518B gene, which is up-regulated in colorectal cancer, plays a role in metastasis, but neither the mechanisms involved in this process nor the role of the different isoforms of the gene are known. Here we show that the ratio of these isoforms is related to the relapsing of the disease, and that the protein ZNF518B interacts with enzymes able to introduce epigenetic changes, which may affect the activity of many genes. We also report a list of genes affected in common by ZNF518B and by two of those related enzymes, namely, G9A and EZH2. An in-depth analysis of five of those genes revealed that ZNF518B is involved in the recruitment of the enzymes and in the deposition of the corresponding epigenetic marks. The results highlight the relevance of epigenetic changes in cancer development, and open the possibility of developing therapeutic approaches, as the introduction of epigenetic modifications is reversible.

Abstract

The ZNF518B gene, which is up-regulated in colorectal cancer, plays a role in cell dissemination and metastasis. It encodes a zinc-finger protein, which interacts with histone methyltransferases G9A and EZH2. The expression of the two major mRNA isoforms 1 (coding for the full protein) and 2 was quantified by RT-qPCR in a cohort of 66 patients. The effects of silencing ZNF518B on the transcriptome of DLD1 and HCT116 cells were analysed by Clariom-S assays and validated by RT-qPCR. The recruitment of methyltransferases and the presence of H3K27me3 were studied by chromatin immunoprecipitation (ChIP). The ratio (isoform 2)/(isoform 1) negatively correlated with the relapsing of disease. The study of the transcriptome of DLD1 and HCT116 cells revealed that many genes affected by silencing ZNF518B are related to cancer. After crossing these results with the list of genes affected by silencing the histone methyltransferases (retrieved in silico), five genes were selected. ChIP analysis revealed that the recruitment of EZH2 is ZNF518B-dependent in KAT2B, RGS4 and EFNA5; the level of H3K27me3 changes in accordance. G9A also binds RGS4 and PADI3 in a ZNF518B-dependent manner. The results highlight the importance of epigenetics in cancer and open a novel therapeutic possibility, as inhibition of histone methyltransferases may reverse the disease-linked histone marks.

Short-form RON (sf-RON) enhances glucose metabolism to promote cell proliferation via activating β-catenin/SIX1 signaling pathway in gastric cancer

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 β-catenin expression level through the AKT1/GSK3β signaling pathway. Meanwhile, the binding sites of β-catenin were identified in the promoter region of SIX1 and it was also demonstrated that β-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/β-catenin/SIX1 signaling axis and had significant implications for choosing the therapeutic target of gastric 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.

MET and RON receptor tyrosine kinases in colorectal adenocarcinoma: molecular features as drug targets and antibody-drug conjugates for therapy

Advanced colorectal adenocarcinoma (CRAC), featured by distinctive histopathological appearance, distant organ metastasis, acquired chemoresistance, and tumorigenic stemness is a group of heterogeneous cancers with unique genetic signatures and malignant phenotypes. Treatment of CRAC is a daunting task for oncologists. Currently, various strategies including molecular targeting using therapeutic monoclonal antibodies, small molecule kinase inhibitors and immunoregulatory checkpoint therapy have been applied to combat this deadly disease. However, these therapeutic modalities and approaches achieve only limited success. Thus, there is a pharmaceutical need to discover new targets and develop novel therapeutics for CRAC therapy. MET and RON receptor tyrosine kinases have been implicated in CRAC pathogenesis. Clinical studies have revealed that aberrant MET and/or RON expression and signaling are critical in regulating CRAC progression and malignant phenotypes. Increased MET and/or RON expression also has prognostic value for CRAC progression and patient survival. These features provide the rationale to target MET and RON for clinical CRAC intervention. At present, the use of small molecule kinase inhibitors targeting MET for CRAC treatment has achieved significant progress with several approvals for clinical application. Nevertheless, antibody-based biotherapeutics, although under clinical trials for more than 8 years, have made very little progress. In this review, we discuss the importance of MET and/or RON in CRAC tumorigenesis and development of anti-MET, anti-RON, and MET and RON-dual targeting antibody-drug conjugates for clinical application. The findings from both preclinical studies and clinical trials highlight the potential of this novel type of biotherapeutics for CRAC therapy in the future.

FOXD3 inhibits cell proliferation, migration, and invasion in nasopharyngeal carcinoma through regulation of the PI3K-Akt pathway

FOXD3 has been found previously to positively regulate miR-26b, a tumor inhibitor of nasopharyngeal carcinoma (NPC). However, FOXD3's precise function and associated mechanism of action in NPC have not yet been investigated. In this study, the expression of FOXD3 mRNA and protein was evaluated using RT-qPCR, western blotting, and immunohistochemistry. Protein levels involved in the phosphoinositide 3-kinase - protein kinase B (PI3K-Akt) pathway were assessed by western blot, and cell proliferation was determined by MTT and colony forming assays. Additionally, cell apoptosis was assessed by flow cytometric assay. Finally, the migration and invasion capabilities of the NPC cells were determined using wound healing and Transwell assays. We found that FOXD3 levels were relatively low in NPC tissue and cells, while an increase caused the inhibition of the PI3K-Akt pathway. Functional experiments found that overexpression of FOXD3 suppressed cell proliferation, migration, and invasion and enhanced cell apoptosis in NPC C6661 cells. IGF-1, an activator of the PI3K-Akt pathway, reversed the inhibitory effect of FOXD3. Furthermore, we found upregulation of the PI3K-Akt pathway and upregulation of the inhibitory effects of FOXD3 on C6661 cellular activities. In conclusion, FOXD3 negatively affected the PI3K-Akt pathway to restrain the processes involved in C6661 cell pathology. These findings further exposed the function and downstream axis of FOXD3 in NPC and displayed a promising new target for NPC therapy.

Targeting RON receptor tyrosine kinase for treatment of advanced solid cancers: antibody-drug conjugates as lead drug candidates for clinical trials

The recepteur d'origine nantais (RON) receptor tyrosine kinase, belonging to the mesenchymal-to-epithelial transition proto-oncogene family, has been implicated in the pathogenesis of cancers derived from the colon, lung, breast, and pancreas. These findings lay the foundation for targeting RON for cancer treatment. However, development of RON-targeted therapeutics has not gained sufficient attention for the last decade. Although therapeutic monoclonal antibodies (TMABs) targeting RON have been validated in preclinical studies, results from clinical trials have met with limited success. This outcome diminishes pharmaceutical enthusiasm for further development of RON-targeted therapeutics. Recently, antibody-drug conjugates (ADCs) targeting RON have drawn special attention owing to their increased therapeutic activity. The rationale for developing anti-RON ADCs is based on the observation that cancer cells are not sufficiently addicted to RON signaling for survival. Thus, TMAB-mediated inhibition of RON signaling is ineffective for clinical application. In contrast, anti-RON ADCs combine a target-specific antibody with potent cytotoxins for cancer cell killing. This approach not only overcomes the shortcomings in TMAB-targeted therapies but also holds the promise for advancing anti-RON ADCs into clinical trials. In this review, we discuss the latest advancements in the development of anti-RON ADCs for targeted cancer therapy including drug conjugation profile, pharmacokinetic properties, cytotoxic effect in vitro, efficacy in tumor models, and toxicological activities in primates.

RON receptor tyrosine kinase in pancreatic ductal adenocarcinoma: Pathogenic mechanism in malignancy and pharmaceutical target for therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with poor prognosis and high mortality. Molecular aberrations associated with PDAC pathogenesis and progression have been extensively investigated. Nevertheless, these findings have not been translated into clinical practice. Lack of therapeutics for PDAC treatment is another challenge. Recent application of molecularly targeted and immunoregulatory therapies appears to be disappointing. Thus, discovery of new targets and therapeutics is urgently needed to combat this malignant disease. The RON receptor tyrosine kinase is a tumorigenic determinant in PDAC malignancy, which provides the rationale to target RON for PDAC treatment. In this review, we summarize the latest evidence of RON in PDAC pathogenesis and the development of anti-RON antibody-drug conjugates for potential PDAC therapy. The finding that anti-RON antibody-drug conjugates show efficacy in preclinical animal models highlights the potential of this novel class of anti-cancer biotherapeutics in future clinical trials.

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.

Human cytomegalovirus ie2 affects the migration of glioblastoma by mediating the different splicing patterns of RON through hnRNP A2B1

Glioblastoma is the most aggressive intracranial tumor and diffuse migration is the leading cause of death. Recent evidence has indicated that heterogeneous nuclear ribonucleoprotein A2B1 (hnRNP A2B1) is overexpressed in human glioblastoma tissue and enhances glioblastoma invasion in vitro. We found by mass spectrometry that hnRNP A2B1 interacts with human cytomegalovirus (HCMV) immediate early 86 protein (IE86, ie2 gene-encoded) in malignant glioma cells (U87MG) infected with HCMV. However, the role of hnRNP A2 B1 in glioblastoma development remains poorly understood. Here, we report that hnRNP A2B1 is highly expressed in the HCMV·ie2 transgenic mice model. This phenomenon was confirmed in U87MG cell lines transfected with pEGFP-N3-ie2 plasmid. In addition, hnRNP A2B1 knockdown in U87MG cells inhibited tumor migration, and this effect might be mediated by hnRNP A2B1 through effects on splicing patterns of RON. Our data suggested that HCMV· ie2 promotes glioblastoma migration by regulating hnRNP A2B1 expression.

Receptor tyrosine kinase, RON, promotes tumor progression by regulating EMT and the MAPK signaling pathway in human oral squamous cell carcinoma

The receptor tyrosine kinase, recepteur d'origine nantais (RON), is known to be associated with the progression, metastasis, and prognosis of various types of cancers. Nevertheless, the role of RON in human oral squamous cell carcinoma (OSCC) is unclear. This study evaluated whether RON affects oncogenic behavior, oncogenic signaling pathways, and clinical outcomes, including survival, in human OSCC. Reverse transcription‑PCR, quantitative PCR, western blotting and immunohistochemical staining were used to determine mRNA and protein expression levels of RON. Cell invasion, migration and apoptosis assays were used to assess the functional effects of small interfering RNA‑mediated knockdown of RON or snail family transcriptional repressor 2 (SLUG). RON knockdown suppressed tumor cell invasion and migration and enhanced apoptosis in human OSCC cells. RON knockdown also decreased the phosphorylation of MAPK signaling proteins, such as ERK1/2, JNK and p38. In addition, RON knockdown suppressed the expression of the epithelial mesenchymal transition (EMT)‑related transcription factor, SLUG. SLUG knockdown blocked the enhancement of cell invasion and migration induced by macrophage‑stimulation protein (MSP)‑mediated RON activation in OSCC cells. The cell morphology was changed to spindle‑like shape under MSP‑mediated RON activation in OSCC cells. RON was overexpressed in both fresh and paraffin‑embedded human OSCC tissues. Taken together, these results indicate that RON contributed to tumor progression by regulating the EMT‑related factor, SLUG, and the MAPK pathway in OSCC. This study may provide a theoretical basis for the application of RON‑targeting agents, currently being studied in various cancer fields, for the treatment of OSCC.

Association study of frameshift and splice variant polymorphisms with risk of idiopathic recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is defined as ≥2 consecutive pregnancy losses, and can be caused by various factors, including genetics, chromosomal abnormalities, thrombophilia, immune disorders, nutritional factors, environmental factors, psychological stress or maternal infections; however, as many as 50% of RPL cases are idiopathic. In the present study, the role of genetic polymorphisms in RPL was investigated. Four gene polymorphisms were selected by whole exome sequencing, including membrane spanning 4‑domains A14 (MS4A14)D>I (rs3217518), solute carrier family 2 member 7 (SLC2A7)D>I (rs60746313), pregnancy specific β‑1‑glycoprotein 9 (PSG9)C>T (rs3746297) and ATP binding cassette subfamily B member 5 (ABCB5)C>G (rs17143187), and the aim was to investigate their association with RPL in Korean women. Genotyping was performed using polymerase chain reaction‑restriction fragment length polymorphism assay. Allele combination analysis revealed that the four‑allele combination I‑D‑T‑G, (MS4A14/SLC2A7/PSG9/ABCB5) was associated with a decreased risk for RPL. Interaction analysis demonstrated that the following genotypes: MS4A14 DI+II, SLC2A DI+II and ABCB 5 CG+GG, were associated with a prothrombin time ≥12 sec and with RPL risk. It may be concluded that the four gene polymorphisms do not affect RPL individually, but are associated with RPL when in combination with other genes or blood coagulation factors. Notably, the MS4A14 I allele, with a prothrombin time ≥12 sec, may be a potential biomarker for diagnosis, prevention and prognosis of RPL.

Splice variants of the extracellular region of RON receptor tyrosine kinase in lung cancer cell lines identified by PCR and sequencing

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.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3747-x) contains supplementary material, which is available to authorized users.