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

Epidermal growth factor receptor (EGFR) is a causal factor in carcinoma, yet many carcinoma patients are resistant to EGFR inhibitors. Potential insight into this resistance stems from prior work that showed EGFR in normal epithelial cells docks to the extracellular domain of the plasma membrane proteoglycan syndecan-4 (Sdc4) engaged with α3ß1 and α6ß4 integrins. We now report that this receptor complex is modified by the recruitment of syndecan-2 (Sdc2), the Recepteur d'Origine Nantais (RON) tyrosine kinase, and the cellular signaling mediator Abelson murine leukemia viral oncogene homolog 1 (ABL1) in triple-negative breast carcinoma and head and neck squamous cell carcinoma, where it contributes to EGFR kinase-independent proliferation. Treatment with a peptide mimetic of the EGFR docking site in the extracellular domain of Sdc4 (called SSTNEGFR) disrupts the entire complex and causes a rapid, global arrest of the cell cycle. Normal epithelial cells do not recruit these additional receptors to the adhesion mechanism and are not arrested by SSTNEGFR. Although EGFR docking with Sdc4 in the tumor cells is required, cell cycle progression does not depend on EGFR kinase. Instead, progression depends on RON kinase, activated by its incorporation into the complex. RON activates ABL1, which suppresses p38 mitogen-activated protein kinase and prevents a p38-mediated signal that would otherwise arrest the cell cycle. These findings add to the growing list of receptor tyrosine kinases that support tumorigenesis when activated by their association with syndecans at sites of matrix adhesion and identify new potential targets for cancer therapy.

Discovery of novel conjugates of quinoline and thiazolidinone urea as potential anti-colorectal cancer agent.

Based on the obtained SARs, further structural optimisation of compound BC2021-104511-15i was conducted in this investigation, and totally ten novel quinoline derivates were designed, synthesised and optimised for biological activity. Among them, compound 10a displayed significant in vitro anticancer activity against COLO 205 cells with an IC50 value of 0.11 µM which was over 90-fold more potent than that of Regorafenib (IC50>10.0 µM) and Fruquintinib (IC50>10.0 µM). Furthermore, compound 10a exhibited over 90-fold selectivity towards COLO 205 relative to human normal colorectal mucosa epithelial cell FHC cells. Flow cytometry study demonstrated that compound 10a could induce apoptosis in COLO 205 cells, however, it could not induce cell cycle arrest in COLO 205 cells. The results of preliminary kinase profile study showed that compound 10a was a potential HGFR and MST1R dual inhibitor, with IC50 values of 0.11 µM and 0.045 µM, respectively.

The Promoter Region of the Proto-Oncogene MST1R Contains the Main Features of G-Quadruplexes Formation.

MST1R (RON) is a receptor of the MET tyrosine kinase receptor family involved in several cancers such as pancreas, breast, ovary, colon, and stomach. Some studies have shown that overexpression of MST1R increases the migratory and invasive properties of cancer cells. The promoter region of the oncogene MST1R is enriched in guanine residues that can potentially form G-quadruplexes (G4s), as it was observed in other oncogenic promoters such as KRAS and c-MYC. There is abundant literature that links the presence of G4s in promoter regions of oncogenes to diverse gene regulation processes that are not well understood. In this work, we have studied the reverse and forward sequence of MST1R promoter region using the G4Hunter software and performed biophysical studies to characterize the best scored sequences.

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

PURPOSE: This study evaluates the prognostic significance of MST1R (RON) expression in breast cancer with respect to disease progression, long-term survival, subtype, and association with conventional prognostic factors. METHODS: The approach includes interrogation of survival and tumor staging with paired MST1R RNA expression from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets. Protein expression evaluation was performed using immunohistochemistry (IHC) staining of MST1R on breast cancer tissue samples from the Cancer Diagnosis Program Breast Cancer Progression tissue microarray and locally obtained breast tumor tissue samples analyzed with paired survival, metastasis, and subtype. RESULTS: Data from TCGA (n = 774) show poorer relapse-free survival (RFS) in patients with high MST1R expression (P = 0.32) and no difference in MST1R expression based on tumor stage (P = 0.77) or nodal status (P = 0.94). Patients in the GEO-derived Kaplan-Meier Plotter microarray dataset demonstrate the association of MST1R and poorer overall survival (n = 1402, P = 0.018) and RFS in patients receiving chemotherapy (n = 798, P = 0.041). Patients with high MST1R expression display worse overall survival (P = 0.01) and receiver operator characteristic (ROC) analysis demonstrate the predictive capacity of increased MST1R with early death (P = 0.0017) in IHC-stained samples. Paired IHC-stained breast tumor samples from the primary versus metastatic site show MST1R expression is associated with metastatic progression (P = 0.032), and ROC analysis supports the predictive capacity of MST1R in metastatic progression (P = 0.031). No associations of MST1R with estrogen receptor (ER), progesterone receptor (PR), both ER and PR, HER2 positivity, or triple-negativity were found (P = 0.386, P = 0.766, P = 0.746, P = 0.457, P = 0.947, respectively). CONCLUSIONS: MST1R expression has prognostic value in breast cancer with respect to survival and metastatic progression. MST1R expression is not associated with tumor stage, nodal status, or subtype.

Whole-exome sequencing identifies MST1R as a genetic susceptibility gene in nasopharyngeal carcinoma.

Multiple factors, including host genetics, environmental factors, and Epstein-Barr virus (EBV) infection, contribute to nasopharyngeal carcinoma (NPC) development. To identify genetic susceptibility genes for NPC, a whole-exome sequencing (WES) study was performed in 161 NPC cases and 895 controls of Southern Chinese descent. The gene-based burden test discovered an association between macrophage-stimulating 1 receptor (MST1R) and NPC. We identified 13 independent cases carrying the MST1R pathogenic heterozygous germ-line variants, and 53.8% of these cases were diagnosed with NPC aged at or even younger than 20 y, indicating that MST1R germline variants are relevant to disease early-age onset (EAO) (age of ≤20 y). In total, five MST1R missense variants were found in EAO cases but were rare in controls (EAO vs. control, 17.9% vs. 1.2%, P = 7.94 × 10(-12)). The validation study, including 2,160 cases and 2,433 controls, showed that the MST1R variant c.G917A:p.R306H is highly associated with NPC (odds ratio of 9.0). MST1R is predominantly expressed in the tissue-resident macrophages and is critical for innate immunity that protects organs from tissue damage and inflammation. Importantly, MST1R expression is detected in the ciliated epithelial cells in normal nasopharyngeal mucosa and plays a role in the cilia motility important for host defense. Although no somatic mutation of MST1R was identified in the sporadic NPC tumors, copy number alterations and promoter hypermethylation at MST1R were often observed. Our findings provide new insights into the pathogenesis of NPC by highlighting the involvement of the MST1R-mediated signaling pathways.

Identification of clear cell renal cell carcinoma and oncocytoma using a three-gene promoter methylation panel.

BACKGROUND: Promoter methylation has emerged as a promising class of epigenetic biomarkers for diagnosis and prognosis of renal cell tumors (RCTs). Although differential gene promoter methylation patterns have been reported for the major subtypes (clear cell, papillary and chromophobe renal cell carcinoma, and oncocytoma), validation of diagnostic performance in independent series have been seldom performed. Herein, we aimed at assessing the diagnostic performance of genes previously shown to be hypermethylated in RCTs in different clinical settings. METHODS: Promoter methylation levels of HOXA9 and OXR1 were assessed by quantitative methylation specific PCR. ROC curves were generated for OXR1, OXR1 combined with MST1R and HOXA9. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were computed, maximizing specificity. Methylation levels were also correlated with clinical and pathological relevant parameters. RESULTS: HOXA9 and OXR1 promoter methylation was disclosed in 73 and 87% of RCTs, respectively. A two-gene methylation panel comprising OXR1 and MST1R identified malignancy with 98% sensitivity and 100% specificity, and clear cell renal cell carcinoma with 90% sensitivity and 98% specificity. HOXA9 promoter methylation allowed for discrimination between oncocytoma and both papillary and chromophobe renal cell carcinoma but only with 77% sensitivity and 73% specificity. Significantly higher OXR1 promoter methylation levels (p = 0.005) were associated with high nuclear grade in ccRCC. CONCLUSIONS: A panel including OXR1 and MST1R promoter methylation allows specific and sensitive identification of renal cell tumors, and, especially, of clear cell renal cell carcinoma. Moreover, higher OXR1 promoter methylation levels associate with clear cell renal cell carcinoma nuclear grade, a surrogate for tumor aggressiveness. Thus, gene promoter methylation analysis might a useful ancillary tool in diagnostic management of renal masses.

The MET Family of Receptor Tyrosine Kinases Promotes a Shift to Pro-Tumor Metabolism.

The development and growth of cancer is fundamentally dependent on pro-tumor changes in metabolism. Cancer cells generally shift away from oxidative phosphorylation as the primary source of energy and rely more heavily on glycolysis. Receptor tyrosine kinases (RTKs) are a type of receptor that is implicated in this shift to pro-tumor metabolism. RTKs are important drivers of cancer growth and metastasis. One such family of RTKs is the MET family, which consists of MET and RON (MST1R). The overexpression of either MET or RON has been associated with worse cancer patient prognosis in a variety of tumor types. Both MET and RON signaling promote increased glycolysis by upregulating the expression of key glycolytic enzymes via increased MYC transcription factor activity. Additionally, both MET and RON signaling promote increased cholesterol biosynthesis downstream of glycolysis by upregulating the expression of SREBP2-induced cholesterol biosynthesis enzymes via CTTNB1. These changes in metabolism, driven by RTK activity, provide potential targets in limiting tumor growth and metastasis via pharmacological inhibition or modifications in diet. This review summarizes pro-tumor changes in metabolism driven by the MET family of RTKs. In doing so, we will offer our unique perspective on metabolic pathways that drive worse patient prognosis and provide suggestions for future study.

An Introduction and Overview of RON Receptor Tyrosine Kinase Signaling.

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.

The MST1R/RON Tyrosine Kinase in Cancer: Oncogenic Functions and Therapeutic Strategies.

The MST1R/RON receptor tyrosine kinase is a homologue of the more well-known MET receptor. Like MET, RON orchestrates cell signaling pathways that promote oncogenesis and enable cancer cell survival; however, it has a more unique role in the regulation of inflammation. RON was originally described as a transmembrane receptor expressed on tissue resident macrophages and various epithelial cells. RON is overexpressed in a variety of cancers and its activation modifies multiple signaling pathways with resultant changes in epithelial and immune cells which together modulate oncogenic phenotypes. While several RON isoforms have been identified with differences in structure, activation, and pathway regulation, increased RON expression and/or activation is consistently associated with worse outcomes. Tyrosine kinase inhibitors targeting RON have been developed, making RON an actionable therapeutic target.

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.

The MSP-RON axis stimulates cancer cell growth in models of triple negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor prognosis and high rates of relapse. The lack of actionable targets for TNBC has contributed to the high mortality rates of this disease, and new candidate molecules for potential manipulation are urgently required. Here, we show that macrophage-stimulating protein (MSP) and its tyrosine kinase receptor, Recepteur d'origine nantais (RON), are potent drivers of cancer cell growth and tumor progression in a mouse model of TNBC driven by the loss of Trp53 and Brca1. After comparison of two genetically engineered mouse models of TNBC, we found that mammary tumors from K14-Cre;Brca1F/F ;Trp53F/F (KB1P) mice exhibit high endogenous levels of MSP and RON expression. We show that MSP stimulates serine/threonine kinase 1 and extracellular regulated MAPK activation as well as cancer cell growth in cell lines derived from the two mouse models, while genetic and pharmacological inhibition of RON prevents these effects. Similarly, KB1P tumor progression in mice was robustly attenuated by treatment with a RON inhibitor with accompanied reduction in the proliferation marker, Ki-67. Analysis of human gene expression data confirmed that the genes encoding MSP and RON are robustly expressed in human TNBC as well as other subsets of breast cancer. Our findings uncover a mouse model where MSP expression and RON expression are naturally increased, and they provide evidence that this receptor and its ligand are viable candidate molecules for targeted treatment of breast cancer.

The Receptor Tyrosine Kinase RON and Its Isoforms as Therapeutic Targets in Ewing Sarcoma.

The receptor tyrosine kinase (RTK) RON is linked to an aggressive metastatic phenotype of carcinomas. While gaining interest as a therapeutic target, RON remains unstudied in sarcomas. In Ewing sarcoma, we identified RON among RTKs conferring resistance to insulin-like growth factor-1 receptor (IGF1R) targeting. Therefore, we explored RON in pediatric sarcoma cell lines and an embryonic Tg(kdrl:mCherry) zebrafish model, using an shRNA-based approach. To examine RON-IGF1R crosstalk, we employed the clinical-grade monoclonal antibody IMC-RON8, alone and together with the IGF1R-antibody IMC-A12. RON silencing demonstrated functions in vitro and in vivo, particularly within micrometastatic cellular capacities. Signaling studies revealed a unidirectional IGF1-mediated cross-activation of RON. Yet, IMC-A12 failed to sensitize cells to IMC-RON8, suggesting additional mechanisms of RON activation. Here, RT-PCR revealed that childhood sarcomas express short-form RON, an isoform resistant to antibody-mediated targeting. Interestingly, in contrast to carcinomas, treatment with DNA methyltransferase inhibitor did not diminish but increased short-form RON expression. Thus, this first report supports a role for RON in the metastatic progression of Ewing sarcoma. While principal molecular functions appear transferrable between carcinomas, Ewing sarcoma and possibly more common sarcoma subtypes, RON highlights that specific regulations of cellular networks and isoforms require better understanding to successfully transfer targeting strategies.

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

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

Identification of an iron-responsive subtype in two children diagnosed with relapsing-remitting multiple sclerosis using whole exome sequencing.

BACKGROUND: Multiple sclerosis is a disorder related to demyelination of axons. Iron is an essential cofactor in myelin synthesis. Previously, we described two children (males of mixed ancestry) with relapsing-remitting multiple sclerosis (RRMS) where long-term remission was achieved by regular iron supplementation. A genetic defect in iron metabolism was postulated, suggesting that more advanced genetic studies could shed new light on disease pathophysiology related to iron. METHODS: Whole exome sequencing (WES) was performed to identify causal pathways. Blood tests were performed over a 10 year period to monitor the long-term effect of a supplementation regimen. Clinical wellbeing was assessed quarterly by a pediatric neurologist and regular feedback was obtained from the schoolteachers. RESULTS: WES revealed gene variants involved in iron absorption and transport, in the transmembrane protease, serine 6 (TMPRSS6) and transferrin (TF) genes; multiple genetic variants in CUBN, which encodes cubilin (a receptor involved in the absorption of vitamin B12 as well as the reabsorption of transferrin-bound iron and vitamin D in the kidneys); SLC25A37 (involved in iron transport into mitochondria) and CD163 (a scavenger receptor involved in hemorrhage resolution). Variants were also found in COQ3, involved with synthesis of Coenzyme Q10 in mitochondria. Neither of the children had the HLA-DRB1*1501 allele associated with increased genetic risk for MS, suggesting that the genetic contribution of iron-related genetic variants may be instrumental in childhood MS. In both children the RRMS has remained stable without activity over the last 10 years since initiation of nutritional supplementation and maintenance of normal iron levels, confirming the role of iron deficiency in disease pathogenesis in these patients. CONCLUSION: Our findings highlight the potential value of WES to identify heritable risk factors that could affect the reabsorption of transferrin-bound iron in the kidneys causing sustained iron loss, together with inhibition of vitamin B12 absorption and vitamin D reabsorption (CUBN) and iron transport into mitochondria (SLC25A37) as the sole site of heme synthesis. This supports a model for RRMS in children with an apparent iron-deficient biochemical subtype of MS, with oligodendrocyte cell death and impaired myelination possibly caused by deficits of energy- and antioxidant capacity in mitochondria.

Identification of the splice variants of Recepteur d'Origine nantais (RON) in lung cancer cell lines.

RON receptor tyrosine kinase is a transmembrane protein directly involved in suppression of inflammation and its aberrant expression linked to cancers and metastasis. Efforts to block deregulated RON signaling in tumors using small molecule kinase inhibitors or antibodies have been complicated by the presence of unknown number/types of isoforms of RON, which, despite being structurally similar, localize differently and mediate varied functions. Current study was designed to identify the splice variants of RON transcripts formed by skipping of sequences between exons 9 and 14 for better understanding of isoform specific RON signaling in cancers. PCR amplification and bi-directional sequencing of a 901 bp cDNA sequence located between exons 9 to 14 of RON from lung cancer cell lines revealed the presence of two splicing variants formed by skipping of exons 11 and 11-13. Each of these transcripts was found in more than one cell line. Expressed sequence tag (EST) database search indicated that the splicing variant lacking exons 11-13 was a novel one. Here we conclude that the splice variants of RON lacking exon 11 and exons 11-13 were detected in several lung cancer cell lines. Novel variant formed by skipping exons 11-13, the sequence of which code for transmembrane region, is predicted to code for a truncated isoform that may be secreted out. Tumors may antagonize the ligand dependent anti-inflammatory function of wild-type RON by secreting out the ligand binding isoforms.

Prognostic significance of MST1R dysregulation in renal cell tumors.

Macrophage stimulating 1 receptor (MST1R) is a C-MET proto-oncogene family receptor tyrosine kinase. Promoter methylation patterns determine transcription of MST1R variants as hypermethylation of a region upstream of transcription start site (TSS) is associated with lack of MST1R long transcript (MST1R long) and expression of a short transcript with oncogenic potential. Thus, we aimed to investigate MST1R variant transcript regulation in renal cell tumors (RCT) and assess their prognostic potential. We found, in a series of 120 RCT comprising the four main subtypes (clear cell, papillary and chromophobe renal cell carcinoma, and oncocytoma), that higher methylation levels close to TSS were associated with total MST1R expression levels (MST1R total) in primary tumors (p=0.049) and renal cancer cell lines. After demethylating treatment, MST1R long/MST1R total ratio increased, as expected, in two renal cell carcinoma cell lines tested. However, in primary tumors with hypermethylation upstream of TSS, a decrease in MST1R long/MST1R total ratio was not detected, although higher expression ratio of nuclear factor-κB was apparent. Furthermore, survival analysis demonstrated that MST1R long/MST1R total ratio was independently associated with shorter disease-specific and disease-free survival, whereas MST1R total expression associated with shorter disease-specific survival. In conclusion, although promoter methylation patterns seem to determine MST1R global transcription regulation in renal cell carcinoma, other mechanisms might contribute to deregulate MST1R variant expression in RCT. Nevertheless, MST1R total expression and MST1R long/MST1R total ratio modulate the biological and clinical aggressiveness of renal cell carcinoma, as depicted by its prognostic significance, a finding that requires validation in a larger independent series.

Novel splicing variants of recepteur d'origine nantais (RON) tyrosine kinase involving exons 15-19 in lung cancer.

BACKGROUND: Altered expressions of receptor tyrosine kinases drive the growth and metastasis of several cancers. RON is a single pass transmembrane receptor tyrosine kinase (RTK) shown to be aberrantly expressed in various cancer types. However, target validation and successful therapeutic targeting of RON in cancers is hampered by the co-existence of unknown number/types of isoforms, which are structurally similar but functionally diverse. OBJECTIVE: The objective of this study was to identify differential splicing in the C-terminal region of RON transcripts to better understand RON signaling in cancers. mRNA transcript sequence between exons 14 and 20 of RON was PCR amplified and sequenced using cDNA from 10 SCLC and 13 NSCLC cell lines. Specific exon deletions were identified by aligning sequencing chromatograms with reference RON cDNA sequence. RESULTS: We identified the presence of four unique transcript sequence variants of RON formed through skipping of exons 15-19, 16-19, 16-17 and 16. The transcript variants, except the one lacking exons 15-19, were found in more than one cell line. Several cell lines contained two to four of these uniquely spliced transcript variants. dbEST (Expressed Sequence Tags database) or other DNA sequence databases did not contain RON cDNA sequences corresponding to any of the above exon deletions indicating that all these transcript sequence alterations are novel. CONCLUSIONS: Results of our study indicate common occurrence of different types of alternatively spliced transcripts of RON in lung cancer with potential to be translated into proteins lacking active kinase domain. Our findings suggest that tumors produce several dominant negative isoforms which probably inhibit ligand dependent RON signaling, and hence, raise important questions regarding the appropriateness of blocking wild type RON signaling for therapy. Further, presence of transcript variants and their isoform products may interfere with quantitative and functional analysis during target validation.

Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer.

Castrate-resistant prostate cancer (CRPC) is the fatal form of prostate cancer. Although reactivation of androgen receptor (AR) occurs following androgen deprivation, the precise mechanism involved is unclear. Here we show that the receptor tyrosine kinase, RON alters mechanical properties of cells to influence epithelial to mesenchymal transition and functions as a transcription factor to differentially regulate AR signaling. RON inhibits AR activation and subset of AR-regulated transcripts in androgen responsive LNCaP cells. However in C4-2B, a castrate-resistant sub-line of LNCaP and AR-negative androgen independent DU145 cells, RON activates subset of AR-regulated transcripts. Expression of AR in PC-3 cells leads to activation of RON under androgen deprivation but not under androgen proficient conditions implicating a role for RON in androgen independence. Consistently, RON expression is significantly elevated in castrate resistant prostate tumors. Taken together our results suggest that RON activation could aid in promoting androgen independence and that inhibition of RON in combination with AR antagonist(s) merits serious consideration as a therapeutic option during hormone deprivation therapy.

FOXC1 promotes melanoma by activating MST1R/PI3K/AKT.

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

Recepteur d'Origine nantais (RON) tyrosine kinase splicing variants lacking exons 18 and 19 occur ubiquitously in lung cancer.

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.