Transcriptional activation of the Axl and PDGFR-α by c-Met through a ras- and Src-independent mechanism in human bladder cancer

AXL signaling in cancer: from molecular insights to targeted therapies

AXL, a member of the TAM receptor family, has emerged as a potential target for advanced-stage human malignancies. It is frequently overexpressed in different cancers and plays a significant role in various tumor-promoting pathways, including cancer cell proliferation, invasion, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, DNA damage response, acquired therapeutic resistance, immunosuppression, and inflammatory responses. Beyond oncology, AXL also facilitates viral infections, including SARS-CoV-2 and Zika highlighting its importance in both cancer and virology. In preclinical models, small-molecule kinase inhibitors targeting AXL have shown promising anti-tumorigenic potential. This review primarily focuses on the induction, regulation and biological functions of AXL in mediating these tumor-promoting pathways. We discuss a range of therapeutic strategies, including recently developed small-molecule tyrosine kinase inhibitors (TKIs), monoclonal antibodies, and antibody-drug conjugates (ADCs), anti-AXL-CAR, and combination therapies. These interventions are being examined in both preclinical and clinical studies, offering the potential for improved drug sensitivity and therapeutic efficacy. We further discuss the mechanisms of acquired therapeutic resistance, particularly the crosstalk between AXL and other critical receptor tyrosine kinases (RTKs) such as c-MET, EGFR, HER2/HER3, VEGFR, PDGFR, and FLT3. Finally, we highlight key research areas that require further exploration to enhance AXL-mediated therapeutic approaches for improved clinical outcomes.

Clinicopathological significance of c-MET and HER2 altered expression in bladder cancer

BACKGROUND

Tumor recurrence or metastasis after surgery is a significant factor influencing bladder cancer (BC) prognosis. Novel molecular biomarkers are necessary to determine each patient's specific outcome because current biomarkers have limited power for predicting prognosis. The proto-oncogene MET encodes c-MET, a tyrosine kinase receptor. When c-MET attaches to its ligand, it triggers several steps in the signal transduction cascade that control cell survival, proliferation, and invasion. c-MET is overexpressed in several carcinomas. The HER2 gene encodes another receptor tyrosine kinase (RTK). HER2 overexpression is linked to altered proliferation and increased aggressiveness in several malignancies. Identifying crosstalk partners of RTKs implicated in bladder cancer development may have a unique role in predicting aggressiveness. This study explored the expression status of c-MET and HER2 in human BC and their clinical significance in disease outcomes.

METHODS

A quantitative real-time polymerase chain reaction was done on 40 BC patients who had undergone transurethral resection (TUR) or radical cystectomy and had a pathologically verified diagnosis of primary tumor without prior chemoradiotherapy as well as 20 patients with benign diseases who served as controls. The c-MET and HER2 expression levels were investigated, and their relationship with clinicopathological features was analyzed.

RESULTS

c-MET and HER2 gene expression were significantly higher, 6.1- and 4.5-fold, in the study group compared to the controls. The frequency of c-MET and HER2 overexpression in the study group was 80% (32/40) and 90% (36/40), respectively. c-MET overexpression was associated with pathological stage(P = 0.002), tumor grade (P = 0.019), muscle invasion (P = 0.008), and node involvement (P = 0.017), while HER2 overexpression was associated with pathological stage(P = 0.033), invasion to muscles (P = 0.003), and node involvement (P = 0.005). Based on the Log-rank test, patients expressing both c-MET and HER2 had the poorest disease-free survival rates among all studied patients (median = 10 m, 3.0-16.9 95%CI).

CONCLUSION

There is a possible correlation between c-MET and HER2 gene overexpression and poor clinical outcomes in patients with BC.

Curcumin in Cancer and Inflammation: An In-Depth Exploration of Molecular Interactions, Therapeutic Potentials, and the Role in Disease Management

This paper delves into the diverse and significant roles of curcumin, a polyphenolic compound from the Curcuma longa plant, in the context of cancer and inflammatory diseases. Distinguished by its unique molecular structure, curcumin exhibits potent biological activities including anti-inflammatory, antioxidant, and potential anticancer effects. The research comprehensively investigates curcumin's molecular interactions with key proteins involved in cancer progression and the inflammatory response, primarily through molecular docking studies. In cancer, curcumin's effectiveness is determined by examining its interaction with pivotal proteins like CDK2, CK2α, GSK3β, DYRK2, and EGFR, among others. These interactions suggest curcumin's potential role in impeding cancer cell proliferation and survival. Additionally, the paper highlights curcumin's impact on inflammation by examining its influence on proteins such as COX-2, CRP, PDE4, and MD-2, which are central to the inflammatory pathway. In vitro and clinical studies are extensively reviewed, shedding light on curcumin's binding mechanisms, pharmacological impacts, and therapeutic application in various cancers and inflammatory conditions. These studies are pivotal in understanding curcumin's functionality and its potential as a therapeutic agent. Conclusively, this review emphasizes the therapeutic promise of curcumin in treating a wide range of health issues, attributed to its complex chemistry and broad pharmacological properties. The research points towards curcumin's growing importance as a multi-faceted natural compound in the medical and scientific community.

The Role of c-MET as a Biomarker in Patients with Bladder Cancer Treated with Radical Chemo-Radiotherapy

BACKGROUND

Bladder cancer is a highly aggressive cancer, and muscle invasive urothelial carcinoma (MIUC) requires aggressive strategy. Concomitant chemo-radiotherapy (CRT) appears as a therapeutic option that allows bladder sparing. No biomarker is currently available to optimally select patients for CRT.

METHODS

We retrospectively enrolled patients with MIUC who were treated in a curative setting with CRT. Based on c-MET expression in pre-treatment tumor tissue, patients were stratified into two groups: no expression of c-MET (group A) and expression of c-MET (group B). We evaluated the outcome of these patients based on c-MET expression.

RESULTS

After a median follow-up of 40 months, 13 patients were enrolled in this analysis, 8 in group A and 5 in group B. The disease recurrence was 25% in group A and 100% in group B. Compared to group A, patients from group B experienced more frequent and more rapid recurrence in terms of metastases; the 3-year metastatic recurrence rate was 13% and 100%, respectively. The c-MET expression was also associated with a higher rate of cancer-related deaths.

CONCLUSIONS

In this retrospective analysis, c-MET expression was associated with worse disease-free survival and survival in patients treated radically with CRT.

βIII-tubulin suppression enhances the activity of Amuvatinib to inhibit cell proliferation in c-Met positive non-small cell lung cancer cells

Non-Small Cell Lung Carcinoma (NSCLC) remains a leading cause of cancer death. Resistance to therapy is a significant problem, highlighting the need to find new ways of sensitising tumour cells to therapeutic agents. βIII-tubulin is associated with aggressive tumours and chemotherapy resistance in a range of cancers including NSCLC. βIII-tubulin expression has been shown to impact kinase signalling in NSCLC cells. Here, we sought to exploit this interaction by identifying co-activity between βIII-tubulin suppression and small-molecule kinase inhibitors. To achieve this, a forced-genetics approach combined with a high-throughput drug screen was used. We show that activity of the multi-kinase inhibitor Amuvatinib (MP-470) is enhanced by βIII-tubulin suppression in independent NSCLC cell lines. We also show that this compound significantly inhibits cell proliferation among βIII-tubulin knockdown cells expressing the receptor tyrosine kinase c-Met. Together, our results highlight that βIII-tubulin suppression combined with targeting specific receptor tyrosine kinases may represent a novel therapeutic approach for otherwise difficult-to-treat lung carcinomas.

miRNAs role in bladder cancer pathogenesis and targeted therapy: Signaling pathways interplay - A review

Bladder cancer (BC) is the 11th most popular cancer in females and 4th in males. A lot of efforts have been exerted to improve BC patients' care. Besides, new approaches have been developed to enhance the efficiency of BC diagnosis, prognosis, therapeutics, and monitoring. MicroRNAs (miRNAs, miRs) are small chain nucleic acids that can regulate wide networks of cellular events. They can inhibit or degrade their target protein-encoding genes. The miRNAs are either downregulated or upregulated in BC due to epigenetic alterations or biogenesis machinery abnormalities. In BC, dysregulation of miRNAs is associated with cell cycle arrest, apoptosis, proliferation, metastasis, treatment resistance, and other activities. A variety of miRNAs have been related to tumor kind, stage, or patient survival. Besides, although new approaches for using miRNAs in the diagnosis, prognosis, and treatment of BC have been developed, it still needs further investigations. In the next words, we illustrate the recent advances in the role of miRNAs in BC aspects. They include the role of miRNAs in BC pathogenesis and therapy. Besides, the clinical applications of miRNAs in BC diagnosis, prognosis, and treatment are also discussed.

c-Met: A Promising Therapeutic Target in Bladder Cancer

Mesenchymal-epithelial transition factor (c-Met) belongs to the tyrosine kinase receptor family and is overexpressed in various human cancers. Its ligand is hepatocyte growth factor (HGF), and the HGF/c-Met signaling pathway is involved in a wide range of cellular processes, including cell proliferation, migration, and metastasis. Emerging studies have indicated that c-Met expression is strongly associated with bladder cancer (BCa) development and prognosis. Therefore, c-Met is a potential therapeutic target for BCa treatment. Recently, the aberrant expression of noncoding RNAs was found to play a significant role in tumour progression. There is a close connection between c-Met and noncoding RNA. Herein, we summarized the biological function and prognostic value of c-Met in BCa, as well as its potential role as a drug target. The relation of c-Met and ncRNA was also described in the paper.

Dissecting the Role of AXL in Cancer Immune Escape and Resistance to Immune Checkpoint Inhibition

The development and implementation of Immune Checkpoint Inhibitors (ICI) in clinical oncology have significantly improved the survival of a subset of cancer patients with metastatic disease previously considered uniformly lethal. However, the low response rates and the low number of patients with durable clinical responses remain major concerns and underscore the limited understanding of mechanisms regulating anti-tumor immunity and tumor immune resistance. There is an urgent unmet need for novel approaches to enhance the efficacy of ICI in the clinic, and for predictive tools that can accurately predict ICI responders based on the composition of their tumor microenvironment. The receptor tyrosine kinase (RTK) AXL has been associated with poor prognosis in numerous malignancies and the emergence of therapy resistance. AXL is a member of the TYRO3-AXL-MERTK (TAM) kinase family. Upon binding to its ligand GAS6, AXL regulates cell signaling cascades and cellular communication between various components of the tumor microenvironment, including cancer cells, endothelial cells, and immune cells. Converging evidence points to AXL as an attractive molecular target to overcome therapy resistance and immunosuppression, supported by the potential of AXL inhibitors to improve ICI efficacy. Here, we review the current literature on the prominent role of AXL in regulating cancer progression, with particular attention to its effects on anti-tumor immune response and resistance to ICI. We discuss future directions with the aim to understand better the complex role of AXL and TAM receptors in cancer and the potential value of this knowledge and targeted inhibition for the benefit of cancer patients.

KRAS and MET in non-small-cell lung cancer: two of the new kids on the 'drivers' block

Non-small-cell lung cancer (NSCLC) is a heterogeneous disease, and therapeutic management has advanced to identify various critical oncogenic mutations that promote lung cancer tumorigenesis. Subsequent studies have developed targeted therapies against these oncogenes in the hope of personalized treatment based on the tumor's molecular genomics. This review presents a comprehensive review of the biology, new therapeutic interventions, and resistance patterns of two well-defined subgroups, tumors with KRAS and MET alterations. We also discuss the status of molecular testing practices for these two key oncogenic drivers, considering the progressive introduction of next-generation sequencing (NGS) and RNA sequencing in regular clinical practice.

Mesangioproliferative Kidney Diseases and Platelet-Derived Growth Factor-Mediated AXL Phosphorylation

RATIONALE & OBJECTIVE

Immunoglobulin A nephropathy (IgAN) is a common glomerular disease, with mesangial cell proliferation as a major feature. There is no disease-specific treatment. Platelet-derived growth factor (PDGF) contributes to the pathogenesis of IgAN. To better understand its pathogenic mechanisms, we assessed PDGF-mediated AXL phosphorylation in human mesangial cells and kidney tissue biopsy specimens.

STUDY DESIGN

Immunostaining using human kidney biopsy specimens and in vitro studies using primary human mesangial cells.

SETTING & PARTICIPANTS

Phosphorylation of AXL was assessed in cultured mesangial cells and 10 kidney-biopsy specimens from 5 patients with IgAN, 3 with minimal change disease, 1 with membranous nephropathy, and 1 with mesangioproliferative glomerulonephritis (GN).

PREDICTOR

Glomerular staining for phospho-AXL in kidney biopsy specimens of patients with mesangioproliferative diseases.

OUTCOMES

Phosphorylated AXL detected in biopsy tissues of patients with IgAN and mesangioproliferative GN and in cultured mesangial cells stimulated with PDGF.

ANALYTIC APPROACH

t test, Mann-Whitney test, and analysis of variance were used to assess the significance of mesangial cell proliferative changes.

RESULTS

Immunohistochemical staining revealed enhanced phosphorylation of glomerular AXL in IgAN and mesangioproliferative GN, but not in minimal change disease and membranous nephropathy. Confocal-microscopy immunofluorescence analysis indicated that mesangial cells rather than endothelial cells or podocytes expressed phospho-AXL. Kinomic profiling of primary mesangial cells treated with PDGF revealed activation of several protein-tyrosine kinases, including AXL. Immunoprecipitation experiments indicated association of AXL and PDGF receptor proteins. An AXL-specific inhibitor (bemcentinib) partially blocked PDGF-induced cellular proliferation and reduced phosphorylation of AXL and PDGF receptor and the downstream signals (AKT1 and ERK1/2).

LIMITATIONS

Small number of kidney biopsy specimens to correlate the activation of AXL with disease severity.

CONCLUSIONS

PDGF-mediated signaling in mesangial cells involves transactivation of AXL. Finding appropriate inhibitors to block PDGF-mediated transactivation of AXL may provide new therapeutic options for mesangioproliferative kidney diseases such as IgAN.

Comparative Cancer Cell Signaling in Muscle-Invasive Urothelial Carcinoma of the Bladder in Dogs and Humans

Muscle-invasive urothelial carcinoma (MIUC) is the most common type of bladder malignancy in humans, but also in dogs that represent a naturally occurring model for this disease. Dogs are immunocompetent animals that share risk factors, pathophysiological features, clinical signs and response to chemotherapeutics with human cancer patients. This review summarizes the fundamental pathways for canine MIUC initiation, progression, and metastasis, emerging therapeutic targets and mechanisms of drug resistance, and proposes new opportunities for potential prognostic and diagnostic biomarkers and therapeutics. Identifying similarities and differences between cancer signaling in dogs and humans is of utmost importance for the efficient translation of in vitro research to successful clinical trials for both species.

Gas6 expression and Tyrosine kinase Axl Sky receptors: Their relation with tumor stage and grade in patients with bladder cancer

OBJECTIVES

It has been shown that the dysregulation of tyrosine kinase Axl receptor and its ligand growth arrest-specific gene (Gas6) are associated with poor prognosis in various types of tumors but there is not enough study about their importance in bladder cancer (BC). We evaluated the relation of Gas6 gene expression and tyrosine- kinase Axl and Sky (Tyro 3) receptors with tumor stage and grade in patients with BC.

MATERIAL AND METHODS

The study group consists of 55 patients whose transurethral resection of bladder (TUR-B) has been performed due to BC and the control group consists of 12 patients with normal bladder mucosa. In tissues mRNAs of Gas6, Axl, and Sky receptors were examined by quantitative (Real-Time) PCR (qPCR). Protein expression was measured by immunohistochemistry. Plasma Gas6 protein levels were compared with control group by ELISA method.

RESULTS

Patients with BC were grouped as Ta low (n=17), Ta high (n=5), T1 low (n=9), T1 high (n=8) and T2 (n=16) according to their TUR-B pathologies. The qPCR analysis showed that the expression of Gas6 gene and Axl receptor is higher in the tumor-positive group and the immune-histochemical showed that the bladder samples of the tumor-positive group stained significantly positive. When the patients are grouped according to the TUR-B pathologies, a statistical significant difference was observed among groups in the qPCR analysis ratios of Gas6 gene and Axl receptor by (p < 0.05) but no significance was found for Sky receptor (p > 0.05). When Gas6 protein levels in plasma samples were compared by ELISA method, a statistical significance was determined among groups (p = 0.001).

CONCLUSIONS

Our findings indicate that mRNAs of Gas6 and Axl receptor are closely related to tumor stage and grade in patients with BC. Further studies are needed for understanding the role of Gas6 and its receptors on the neoplastic transformation in terms of novel biomarkers and potential therapeutic targets.

Infantile fibrosarcoma-like tumor driven by novel RBPMS-MET fusion consolidated with cabozantinib

Infantile fibrosarcoma (IFS) is nearly universally driven by gene fusions involving the NTRK family. ETV6-NTRK3 fusions account for ∼85% of alterations; the remainder are attributed to NTRK-variant fusions. Rarely, other genomic aberrations have been described in association with tumors identified as IFS or IFS-like. We describe the utility of genomic characterization of an IFS-like tumor. We also describe the successful treatment combination of VAC (vincristine, actinomycin, cyclophosphamide) with tyrosine kinase inhibitor (TKI) maintenance in this entity. This patient presented at birth with a right facial mass, enlarging at 1 mo to 4.9 × 4.5 × 6.3 cm. Biopsy demonstrated hypercellular fascicles of spindle cells with patchy positivity for smooth muscle actin (SMA) and negativity for S100, desmin, myogenin, and MyoD1. Targeted RNA sequencing identified a novel RBPMS-MET fusion with confirmed absence of ETV6-NTRK3, and the patient was diagnosed with an IFS-like tumor. A positron emission tomography (PET) scan was negative for metastatic disease. VAC was given for a duration of 10 mo. Resection at 13 mo of age demonstrated positive margins. Cabozantinib, a MET-targeting TKI, was initiated. The patient tolerated cabozantinib well and has no evidence of disease at 24 mo of age. We describe a novel RBPMS-MET driver fusion in association with a locally aggressive IFS-like tumor. MET functions as an oncogene and, when associated with the RNA binding protein RBPMS, forms an in-frame fusion product that retains the MET kinase domain. This fusion is associated with aberrant cell signaling pathway expression and subsequent malignancy. We describe treatment with cabozantinib in a patient with an IFS-like neoplasm.

Molecular profiling of afatinib-resistant non-small cell lung cancer cells in vivo derived from mice

Non-small-cell lung cancer (NSCLC) is a leading cause of cancer-related death worldwide. NSCLC patients with overexpressed or mutated epidermal growth factor receptor (EGFR) related to disease progression are treated with EGFR-tyrosine kinase inhibitors (EGFR-TKIs). Acquired drug resistance after TKI treatments has been a major focus for development of NSCLC therapies. This study aimed to establish afatinib-resistant cell lines from which afatinib resistance-associated genes are identified and the underlying mechanisms of multiple-TKI resistance in NSCLC can be further investigated. Nude mice bearing subcutaneous NSCLC HCC827 tumors were administered with afatinib at different dose intensities (5-100 mg/kg). We established three HCC827 sublines resistant to afatinib (IC₅₀ > 1 μM) with cross-resistance to gefitinib (IC₅₀ > 5 μM). cDNA microarray revealed several of these sublines shared 27 up- and 13 down-regulated genes. The mRNA expression of selective novel genes - such as transmembrane 4 L six family member 19 (TM4SF19), suppressor of cytokine signaling 2 (SOCS2), and quinolinate phosphoribosyltransferase (QPRT) - are responsive to afatinib treatments only at high concentrations. Furthermore, c-MET amplification and activations of a subset of tyrosine kinase receptors were observed in all three resistant cells. PHA665752, a c-MET inhibitor, remarkably increased the sensitivity of these resistant cells to afatinib (IC₅₀ = 12-123 nM). We established afatinib-resistant lung cancer cell lines and here report genes associated with afatinib resistance in human NSCLC. These cell lines and the identified genes serve as useful investigational tools, prognostic biomarkers of TKI therapies, and promising molecule targets for development of human NSCLC therapeutics.

Role of tyrosine kinases in bladder cancer progression: an overview

Background

Bladder cancer (BCa) is a frequent urothelial malignancy with a high ratio of morbidity and mortality. Various genetic and environmental factors are involved in BCa progression. Since, majority of BCa cases are diagnosed after macroscopic clinical symptoms, it is required to find efficient markers for the early detection. Receptor tyrosine-kinases (RTKs) and non-receptor tyrosine-kinases (nRTKs) have pivotal roles in various cellular processes such as growth, migration, differentiation, and metabolism through different signaling pathways. Tyrosine-kinase deregulations are observed during tumor progressions via mutations, amplification, and chromosomal abnormalities which introduces these factors as important candidates of anti-cancer therapies.

Main body

For the first time in present review we have summarized all of the reported tyrosine-kinases which have been significantly associated with the clinicopathological features of BCa patients.

Conclusions

This review highlights the importance of tyrosine-kinases as critical markers in early detection and therapeutic purposes among BCa patients and clarifies the molecular biology of tyrosine-kinases during BCa progression and metastasis.

AXL receptor tyrosine kinase as a promising anti-cancer approach: functions, molecular mechanisms and clinical applications

Molecular targeted therapy for cancer has been a research hotspot for decades. AXL is a member of the TAM family with the high-affinity ligand growth arrest-specific protein 6 (GAS6). The Gas6/AXL signalling pathway is associated with tumour cell growth, metastasis, invasion, epithelial-mesenchymal transition (EMT), angiogenesis, drug resistance, immune regulation and stem cell maintenance. Different therapeutic agents targeting AXL have been developed, typically including small molecule inhibitors, monoclonal antibodies (mAbs), nucleotide aptamers, soluble receptors, and several natural compounds. In this review, we first provide a comprehensive discussion of the structure, function, regulation, and signalling pathways of AXL. Then, we highlight recent strategies for targeting AXL in the treatment of cancer.AXL-targeted drugs, either as single agents or in combination with conventional chemotherapy or other small molecule inhibitors, are likely to improve the survival of many patients. However, future investigations into AXL molecular signalling networks and robust predictive biomarkers are warranted to select patients who could receive clinical benefit and to avoid potential toxicities.

Characterization of mRNA Expression and Endogenous RNA Profiles in Bladder Cancer Based on The Cancer Genome Atlas (TCGA) Database

Background

Bladder cancer is a multifactorial disease with increasing incidence and mortality. Genetic alterations and altered expressions of mRNAs, long non-coding RNAs (lncRNAs), and miRNAs have been shown to play important roles in the tumorigenesis of bladder cancer. However, the functions of key RNAs and their regulatory network in bladder cancer are still to be elucidated.

Material/Methods

RNA profiles were downloaded from The Cancer Genome Atlas (TCGA) database. The differentially expressed mRNAs, lncRNAs, and miRNAs in bladder cancer were acquired through analyses of data from 414 bladder cancer tissues and 19 normal bladder tissues. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis was performed by using “DAVID6.8” and the R package “ClusterProfile”. Protein–protein interaction and competing endogenous RNA (ceRNA) networks were constructed by using “STRING” database and Cytoscape 3.6.2. Based on the clinical data and Cox regression, a prognosis model was established, and survival analysis was performed.

Results

A total of 1819 mRNAs, 659 lncRNAs, and 160 miRNAs were identified as significantly differentially expressed in bladder cancer of which 52 mRNAs, 58 lncRNAs, and 22 miRNAs were incorporated in the ceRNA network. CFL2 and TPM2 were found to be downregulated and showed significant correlation to each other in bladder cancer. HOXB5 and 6 lncRNAs (ADAMTS9-AS1, AC112721.1, LINC00460, AC110491.1, LINC00163, and HCG22) were strongly associated with high-grade, disease stages, and overall survival.

Conclusions

In this study, we have identified differentially expressed mRNAs, lncRNAs, and miRNAs in bladder cancer which were strongly associated with oncogenesis and prognosis. Further experimental studies are necessary to validate these results.

TYRO3: A potential therapeutic target in cancer

IMPACT STATEMENT

Cancer is among the leading causes of death worldwide. In 2016, 8.9 million people are estimated to have died from various forms of cancer. The current treatments, including surgery with chemotherapy and/or radiation therapy, are not effective enough to provide full protection from cancer, which highlights the need for developing novel therapy strategies. In this review, we summarize the molecular biology of a unique member of a subfamily of receptor tyrosine kinase, TYRO3 and discuss the new insights in TYRO3-targeted treatment for cancer therapy.

The Dual Role of TAM Receptors in Autoimmune Diseases and Cancer: An Overview

Receptor tyrosine kinases (RTKs) regulate cellular processes by converting signals from the extracellular environment to the cytoplasm and nucleus. Tyro3, Axl, and Mer (TAM) receptors form an RTK family that plays an intricate role in tissue maintenance, phagocytosis, and inflammation as well as cell proliferation, survival, migration, and development. Defects in TAM signaling are associated with numerous autoimmune diseases and different types of cancers. Here, we review the structure of TAM receptors, their ligands, and their biological functions. We discuss the role of TAM receptors and soluble circulating TAM receptors in the autoimmune diseases systemic lupus erythematosus (SLE) and multiple sclerosis (MS). Lastly, we discuss the effect of TAM receptor deregulation in cancer and explore the therapeutic potential of TAM receptors in the treatment of diseases.

Analysis of progress and challenges for various patterns of c-MET-targeted molecular imaging: a systematic review

BACKGROUND

Mesenchymal-epithelial transition factor also named c-MET is a receptor tyrosine kinase for the hepatocyte growth factor that plays a pivotal role in tumorigenesis. c-MET-targeted therapies have been tested in preclinical models and patients, with significant benefits for cancer treatment. In recent years, many studies have shown that the expression level and activation status of c-MET are closely correlated to c-MET-targeted therapy response and clinical prognosis, thus highlighting the importance of evaluating the c-MET status during and prior to targeted therapy. Molecular imaging allows the monitoring of abnormal alterations of c-MET in real time and in vivo.

RESULTS

In this review, we initially summarize the recent advances in c-MET-targeted molecular imaging, with a special focus on the development of imaging agents ranging in size from monoclonal antibody to small molecule. The aim of this review is to report the preclinical results and clinical application of all molecular imaging studies completed until now for in vivo detection of c-MET in cancer, in order to be beneficial to development of molecular probe and the combination of molecular imaging technologies for in vivo evaluation of c-MET. Various molecular probe targeted to c-MET possesses distinctive advantages and disadvantages. For example, antibody-based probes have high binding affinity but with long metabolic cycle as well as remarkable immunogenicity.

CONCLUSIONS

Although studies for c-MET-targeted molecular imaging have made many important advances, most of imaging agents specifically target to extracellular area of c-MET receptor; however, it is difficult to reflect entirely activation of c-MET. Therefore, small molecule probes based on tyrosine kinase inhibitors, which could target to intracellular area of c-MET without any immunogenicity, should be paid more attention.

Expression and role of TYRO3 and AXL as potential therapeutical targets in leiomyosarcoma

Background:

Leiomyosarcoma (LMS) are 15% of adult sarcomas and remain seldom curable in metastatic phase. The TAM receptors and their ligands are overexpressed or activated in multiple malignancies, including LMS.

Methods:

The TAM receptor and ligand expression was evaluated in LMS cell lines and 358 sarcoma samples by either gene expression or immunohistochemistry. TYRO3 and AXL were knocked down. Crizotinib and foretinib were investigated in vitro.

Results:

High expression of TYRO3 and AXL was detected in LMS cell lines. TYRO3 or AXL gene knockdown reduced cell proliferation/colony formation. Crizotinib and foretinib decreased TYRO3 and AXL phosphorylation, apoptosis, G2/arrest and reduced colony formation. Immunohistochemistry performed in 107 sarcomas showed higher expression of TYRO3 and GAS6 in LMS vs other sarcomas and nuclear TYRO3 only in LMS. Microarray gene expression performed in 251 sarcomas revealed significantly higher expression of TYRO3 and GAS6 in LMS than other sarcomas. Leiomyosarcoma patients with high expression of GAS6 or PROS1 present a significantly worse PFS.

Conclusions:

Leiomyosarcoma patients, especially those whom develop metastasis, express higher levels of TYRO3 and GAS6. Crizotinib and foretinib showed effective antitumour activity in LMS through TYRO3 and AXL deactivation indicating that clinical trials using TYRO3 and AXL inhibitors are warranted in advanced LMS.

Key Roles of AXL and MER Receptor Tyrosine Kinases in Resistance to Multiple Anticancer Therapies

A major challenge in anticancer treatment is the pre-existence or emergence of resistance to therapy. AXL and MER are two members of the TAM (TYRO3-AXL-MER) family of receptor tyrosine kinases, which, when activated, can regulate tumor cell survival, proliferation, migration and invasion, angiogenesis, and tumor-host interactions. An increasing body of evidence strongly suggests that these receptors play major roles in resistance to targeted therapies and conventional cytotoxic agents. Multiple resistance mechanisms exist, including the direct and indirect crosstalk of AXL and MER with other receptors and the activation of feedback loops regulating AXL and MER expression and activity. These mechanisms may be innate, adaptive, or acquired. A principal role of AXL appears to be in sustaining a mesenchymal phenotype, itself a major mechanism of resistance to diverse anticancer therapies. Both AXL and MER play a role in the repression of the innate immune response which may also limit response to treatment. Small molecule and antibody inhibitors of AXL and MER have recently been described, and some of these have already entered clinical trials. The optimal design of treatment strategies to maximize the clinical benefit of these AXL and MER targeting agents are discussed in relation to the different cancer types and the types of resistance encountered. One of the major challenges to successful development of these therapies will be the application of robust predictive biomarkers for clear-cut patient stratification.

The role of Lutheran/basal cell adhesion molecule in human bladder carcinogenesis

Background

Lutheran/basal cell adhesion molecule (Lu/BCAM) is a membrane bound glycoprotein. This study was performed to investigate the role and downstream signaling pathway of Lu/BCAM in human bladder tumorigenesis.

Methods

Five human bladder cancer (E6, RT4, TSGH8301, TCCSUP and J82), one stable mouse fibroblast cell line (NIH-Lu) expressing Lu/BCAM transgene and sixty human uroepithelial carcinoma specimens were analyzed by real-time PCR, immunohistochemistry (IHC), immunofluorescence (IFA) staining, Western blotting and promoter luciferase assay for Lu/BCAM, respectively. The tumorigenicity of Lu/BCAM was demonstrated by focus formation, colony-forming ability, tumour formation, cell adhesion and migration.

Results

H-ras^V12 was revealed to up-regulate Lu/BCAM at both transcriptional and translation levels. Lu/BCAM expression was detected on the membrane of primary human bladder cancer cells. Over-expression of Lu/BCAM in NIH-Lu stable cells increased focus number, colony formation and cell adhesion accompanied with F-actin rearrangement and decreased cell migration compared with parental NIH3T3 fibroblasts. In the presence of laminin ligand, Lu/BCAM overexpression further suppressed cell migration accompanied with increased cell adhesion. We further revealed that laminin-Lu/BCAM-induced cell adhesion and F-actin rearrangement were through increased Erk phosphorylation with an increase of RhoA and a decrease of Rac1 activity. Similarly, high Lu/BCAM expression was detected in the tumors of human renal pelvis, ureter and bladder, and was significantly associated with advanced tumor stage (p = 0.02). Patients with high Lu/BCAM expression showed a trend toward larger tumor size (p = 0.07) and lower disease-specific survival (p = 0.08), although not reaching statistical significance.

Conclusion

This is the first report showing that Lu/BCAM, in the presence of its ligand laminin, is oncogenic in human urothelial cancers and may have potential as a novel therapeutic target.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-017-0360-x) contains supplementary material, which is available to authorized users.

MET: roles in epithelial-mesenchymal transition and cancer stemness

In a number of cancers, deregulated MET pathway leads to aberrantly activated proliferative and invasive signaling programs that promote malignant transformation, cell motility and migration, angiogenesis, survival in hypoxia, and invasion. A better understanding of oncogenic MET signaling will help us to discover effective therapeutic approaches and to identify which tumors are likely to respond to MET-targeted cancer therapy. In this review, we will summarize the roles of MET signaling in cancer, with particular focus on epithelial-mesenchymal transition (EMT) and cancer stemness. Then, we will provide update on MET targeting agents and discuss the challenges that should be overcome for the development of an effective therapy.

Biomarker development in MET-targeted therapy

Activation of the MET receptor tyrosine kinase by its ligand, hepatocyte growth factor (HGF), has been implicated in a variety of cellular processes, including cell proliferation, survival, migration, motility and invasion, all of which may be enhanced in human cancers. Aberrantly activated MET/HGF signaling correlates with tumorigenesis and metastasis, and is regarded as a robust target for the development of novel anti-cancer treatments. Various clinical trials were conducted to evaluate the safety and efficacy of selective HGF/MET inhibitors in cancer patients. There is currently no optimal or standardized method for accurate and reliable assessment of MET levels, or other biomarkers that are predictive of the patient response to MET-targeted therapeutics. In this review, we discuss the importance of accurate HGF/MET signal detection as a predictive biomarker to guide patient selection for clinical trials of MET-targeted therapies in human cancers.

Targeting molecular aberrations in urothelial carcinoma: are we almost there?

Advances in tumor biology and cancer genetics have led to the development of effective targeted therapies in oncology over the past decade. However, targeted drug development for urothelial carcinoma has been slower than for some other malignancies. The path forward in drug development is through a better understanding of the aberrant pathways driving urothelial tumor development. Steady progress has been made in the characterization of genomic alterations in urothelial carcinoma. The Cancer Genome Atlas (TCGA) project is well underway in the analysis of a large set of urothelial cancer specimens using multiple approaches and technologies. In addition, there are already many well-established mutations and genetic alterations in urothelial carcinoma that likely contribute in an important way to tumor development. In addition, urothelial cancer genome-wide association studies have identified common variants associated with urothelial cancer risk and protein expression that can potentially be therapeutically targeted. Furthermore, the MET pathway has emerged as an exciting target in multiple tumors, including urothelial carcinoma. Our knowledge of how to clinically target many emerging molecular aberrations in urothelial cancer is still in the early stages of development. However, there is much promise in the ongoing research being conducted in urothelial cancer molecular pathogenesis.

HGF/Met and FOXM1 form a positive feedback loop and render pancreatic cancer cells resistance to Met inhibition and aggressive phenotypes

Purpose

Hepatocyte growth factor (HGF)/Met signaling plays critical roles in pancreatic ductal adenocarcinoma (PDA) development and progression and is considered a potential therapeutic target for this disease. However, the mechanism of aberrant activation of HGF/Met signaling and resistance to Met inhibition in PDA remains unclear.

Experimental Design

The mechanistic role of cross-talk between Forkhead box M1 (FOXM1) and HGF/Met signaling in promotion of PDA growth and resistance to Met inhibition was examined using cell culture, molecular biology and mouse models; and the relevance of our experimental and mechanistic findings were validated using human PDA tissues.

Results

Met was markedly overexpressed in both PDA cell lines and pancreatic tumor specimens, and the expression of Met correlated directly with that of FOXM1 in human tumor specimens. Mechanistically, FOXM1 bound to the promoter region of the Met gene and transcriptionally increased the expression of Met. Increased expression of FOXM1 enhanced the activation of HGF/Met signaling and its downstream pathways, including RAS/extracellular signal-regulated kinase 1/2, phosphoinositide 3-kinase/AKT, and signal transducer and activator of transcription 3. Furthermore, activation of HGF/Met signaling increased the expression and transcriptional activity of FOXM1, and the cross-talk between FOXM1 and HGF/Met signaling promoted PDA growth and resistance to Met inhibition.

Conclusions

Collectively, our findings identified a positive feedback loop formed by FOXM1 and HGF/Met and revealed that this loop is a potentially effective therapeutic target for PDA.

Relationship Between Increased Expression of the Axl/Gas6 Signal Cascade and Prognosis of Patients with Upper Tract Urothelial Carcinoma

PURPOSE

Axl, which is in the TAM family of receptor tyrosine kinases, and its ligand, growth arrest-specific gene 6 (Gas6), have been associated with worse prognoses after the surgical treatment of some types of cancers. We herein investigated the biological significance of the protein expression of Axl and Gas6 on the outcomes of patients with upper tract urothelial carcinoma (UTUC).

METHODS

The protein expression of Axl and Gas6 was evaluated by immunohistochemistry, and their relationships with clinicopathological features were investigated in surgical specimens obtained from 161 patients who had been surgically treated for UTUC.

RESULTS

Axl labeling was strong in 67 of 161 (42 %) cases, while Gas6 labeling was strong in 72 of 161 (45 %) cases. The strong expression of Axl correlated with that of Gas6. A high pathological stage (p = 0.009), strong expression of Gas6 (p = 0.038), and strong expression of Axl (p = 0.016) were independent factors for predicting worse cancer-specific survival (CSS). In a subgroup analysis of patients with pT < 2 (N = 53), no significant difference in CSS was observed between patients weakly and strongly expressing Axl/Gas6. In contrast, a subgroup analysis of patients with pT ≥ 2 (N = 108) revealed that the expression levels of Axl and Gas6 correlated with CSS.

CONCLUSION

The protein expression of Axl and its ligand Gas6 may be a useful indicator for a worse clinical outcome in UTUC patients, especially patients with pT ≥ 2, who underwent radical nephroureterectomy.

c-Met targeting in advanced gastric cancer: An open challenge

Despite significant improvements in systemic chemotherapy over the last two decades, the prognosis of patients with advanced gastric and gastroesophageal junction adenocarcinoma (GC) remains poor. Because of molecular heterogeneity, it is essential to classify tumors based on the underlying oncogenic pathways and to develop targeted therapies acting on individual tumors. High-quality research and advances in technology have contributed to the elucidation of molecular pathways underlying disease progression and have stimulated many clinical studies testing target therapies in an advanced disease setting. In particular, strong preclinical evidence for the aberrant activation of the HGF/c-Met signaling pathways in GC cancers exists. This review will cover the c-Met pathway, the mechanisms of c-Met activation and the different strategies of its inhibition. Next, we will focus on the current state of the art in the clinical evaluation of c-Met-targeted therapies and the description of ongoing randomized trials with the idea that in this disease, high quality translational research to identify and validate biomarkers is a priority task.

The c-MET Network as Novel Prognostic Marker for Predicting Bladder Cancer Patients with an Increased Risk of Developing Aggressive Disease

Previous studies have shown that c-MET is overexpressed in cases of aggressive bladder cancer (BCa). Identification of crosstalk between c-MET and other RTKs such as AXL and PDGFR suggest that c-MET network genes (c-MET-AXL-PDGFR) may be clinically relevant to BCa. Here, we examine whether expression of c-MET network genes can be used to identify BCa patients at increased risk of developing aggressive disease. In vitro analysis, c-MET knockdown suppressed cell proliferation, invasion, and migration, and increased sensitivity to cisplatin-induced apoptosis. In addition, c-MET network gene (c-MET, AXL, and PDGFR) expression allowed discrimination of BCa tissues from normal control tissues and appeared to predict poor disease progression in non-muscle invasive BCa patients and poor overall survival in muscle invasive BCa patients. These results suggest that c-MET network gene expression is a novel prognostic marker for predicting which BCa patients have an increased risk of developing aggressive disease. These genes might be a useful marker for co-targeting therapy, and are expected to play an important role in improving both response to treatment and survival of BCa patients.

Cutaneous adverse effects associated with the tyrosine-kinase inhibitor cabozantinib

IMPORTANCE

Cabozantinib S-malate is a vascular endothelial growth factor receptor 2, c-MET, and RET multitargeted tyrosine kinase inhibitor that has antiangiogenic and antitumorigenic properties with potential efficacy for the treatment of several cancers. Cutaneous reactions, one of the most frequently observed adverse effects associated with tyrosine kinase inhibitors, can significantly affect patients' quality of life and drug adherence and represent a major therapeutic challenge to maximizing the efficacy of targeted cancer therapy.

OBJECTIVE

To describe the frequency and spectrum of skin reactions in patients with urothelial carcinoma receiving cabozantinib as monotherapy.

DESIGN, SETTING, AND PARTICIPANTS

A single-institution study at the Clinical Research Center at the National Institutes of Health included 41 consecutive adults with metastatic, progressive urothelial carcinoma enrolled in a National Cancer Institute open-label, nonrandomized, phase 2 clinical trial. Patients receiving cabozantinib were evaluated for the development of skin reactions at each treatment visit from October 2012 to June 2014 by the primary oncology team and referred for dermatologic evaluation as appropriate.

MAIN OUTCOMES AND MEASURES

A detailed history, full-body physical examination, and clinical photographs of cutaneous lesions were obtained.

RESULTS

Of 41 consecutive patients who received cabozantinib, 30 (73%) developed 1 or more cutaneous toxic effects. Adverse events included hand-foot skin reaction (22 [54%]), generalized pigment dilution and/or hair depigmentation (18 [44%]), xerosis (8 [20%]), scrotal erythema/ulceration (6 [15%]), and nail splinter hemorrhages (5 [12%]). Eighteen patients (44%) had 2 or more cutaneous adverse events. Reactions developed in 17 of 30 patients (57%) during the first month of cabozantinib treatment and in 24 of 30 (80%) by the second month. Of patients with skin toxic effects, dose reduction was required for symptom management in 9 of 30 patients (30%), and treatment discontinuation was required in 4 of 30 (13%).

CONCLUSIONS AND RELEVANCE

Cabozantinib monotherapy is associated with 1 or more cutaneous adverse events in most patients. Early detection and prompt treatment may increase patients' adherence to tyrosine kinase inhibitor therapy.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01688999.

STAT3 and HIF1α Signaling Drives Oncogenic Cellular Phenotypes in Malignant Peripheral Nerve Sheath Tumors

Therapeutic options are limited for neurofibromatosis type 1 (NF1)-associated malignant peripheral nerve sheath tumors (MPNST) and clinical trials using drug agents have so far been unsuccessful. This lack of clinical success is likely attributed to high levels of intratumoral molecular heterogeneity and variations in signal transduction within MPNSTs. To better explore the variance of malignant signaling properties within heterogeneous MPNSTs, four MPNST cell lines (ST8814, S462, S1844.1, and S1507.2) were used. The data demonstrate that small-molecule inhibition of the MET proto-oncogene and mTOR had variable outcome when preventing wound healing, cell migration, and invasion, with the S462 cells being highly resistant to both. Of interest, targeted inhibition of the STAT3 transcription factor suppressed wound healing, cell migration, invasion, and tumor formation in all four MPNST lines, which demonstrates that unlike MET and mTOR, STAT3 functions as a common driver of tumorigenesis in NF1-MPNSTs. Of clinical importance, STAT3 knockdown was sufficient to block the expression of hypoxia-inducible factor (HIF)1α, HIF2α, and VEGF-A in all four MPNST lines. Finally, the data demonstrate that wound healing, cell migration, invasion, and tumor formation through STAT3 are highly dependent on HIF signaling, where knockdown of HIF1α ablated these oncogenic facets of STAT3.

IMPLICATIONS

This research reveals that aberrant STAT3 and HIF1a activity drives tumor progression in MPNSTs, indicating that inhibition of the STAT3/HIF1α/VEGF-A signaling axis is a viable treatment strategy.

Met in urological cancers

Met is a tyrosine kinase receptor that is considered to be a proto-oncogene. The hepatocyte growth factor (HGF)-Met signaling system plays an important role in tumor growth, invasion, and metastasis in many types of malignancies. Furthermore, Met expression has been reported to be a useful predictive biomarker for disease progression and patient survival in these malignancies. Many studies have focused on the clinical significance and prognostic role of Met in urological cancers, including prostate cancer (PCa), renal cell carcinoma (RCC), and urothelial cancer. Several preclinical studies and clinical trials are in progress. In this review, the current understanding of the pathological role of Met in cancer cell lines, its clinical significance in cancer tissues, and its predictive value in patients with urological cancers are summarized. In particular, Met-related malignant behavior in castration-resistant PCa and the different pathological roles Met plays in papillary RCC and other histological types of RCC are the subjects of focus. In addition, the pathological significance of phosphorylated Met in these cancers is shown. In recent years, Met has been recognized as a potential therapeutic target in various types of cancer; therapeutic strategies used by Met-targeted agents in urological cancers are summarized in this review.

Analysis of 1,115 patients tested for MET amplification and therapy response in the MD Anderson Phase I Clinic

PURPOSE

This study aimed to assess MET amplification among different cancers, association with clinical factors and genetic aberrations and targeted therapy response modifications.

EXPERIMENTAL DESIGN

From May 2010 to November 2012, samples from patients with advanced tumors referred to the MD Anderson Phase I Clinic were analyzed for MET gene amplification by FISH. Patient demographic, histologic characteristics, molecular characteristics, and outcomes in phase I protocols were compared per MET amplification status.

RESULTS

Of 1,115 patients, 29 (2.6%) had MET amplification. The highest prevalence was in adrenal (2 of 13; 15%) and renal (4 of 28; 14%) tumors, followed by gastroesophageal (6%), breast (5%), and ovarian cancers (4%). MET amplification was associated with adenocarcinomas (P = 0.007), high-grade tumors (P = 0.003), more sites of metastasis, higher BRAF mutation, and PTEN loss (all P < 0.05). Median overall survival was 7.23 and 8.62 months for patients with and without a MET amplification, respectively (HR = 1.12; 95% confidence intervals, 0.83-1.85; P = 0.29). Among the 20 patients with MET amplification treated on a phase I protocol, 4 (20%) achieved a partial response with greatest response rate on agents targeting angiogenesis (3 of 6, 50%). No patient treated with a c-MET inhibitor (0 of 7) achieved an objective response.

CONCLUSION

MET amplification was detected in 2.6% of patients with solid tumors and was associated with adenocarcinomas, high-grade histology, and higher metastatic burden. Concomitant alterations in additional pathways (BRAF mutation and PTEN loss) and variable responses on targeted therapies, including c-MET inhibitors, suggest that further studies are needed to target this population.

Redundant kinase activation and resistance of EGFR-tyrosine kinase inhibitors

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have shown dramatic effects against that tumors harboring EGFR activating mutations in the EGFR intracytoplasmic tyrosine kinase domain and resulted in cell apoptosis. Unfortunately, a number of patients ultimately developed resistance by multiple mechanisms. Thus, elucidation of the mechanism of resistance to EGFR-TKIs can provide strategies for blocking or reversing the situation. Recent studies suggested that redundant kinase activation plays pivotal roles in escaping from the effects of EGFR-TKIs. Herein, we aimed to characterize several molecular events involved in the resistance to EGFR-TKIs mediated by redundant kinase activation.

Combined inhibition of AXL, Lyn and p130Cas kinases block migration of triple negative breast cancer cells

Blocking the migration of metastatic cancer cells is a major goal in the therapy of cancer. The receptor tyrosine kinase AXL is one of the main triggers for cancer cell migration in neoplasia of breast, colon, skin, thyroid and prostate. In our study we analyzed the effect of AXL inhibition on cell motility and viability in triple negative breast cancer cell lines overexpressing AXL. Thereby we reveal that the compound BMS777607, exhibiting the lowest IC50 values for inhibition of AXL kinase activity in the studied cell lines, attenuates cell motility to a lower extent than the kinase inhibitors MPCD84111 and SKI606. By analyzing the target kinases of MPCD84111 and SKI606 with kinase profiling assays we identified Lyn, a Src family kinase, as a target of both compounds. Knockdown of Lyn and the migration-related CRK-associated substrate (p130Cas), had a significant inhibitory effect on cell migration. Taken together, our findings highlight the importance of combinatorial or multikinase inhibition of non-receptor tyrosine kinases and AXL receptor tyrosine kinase in the therapy of triple negative breast cancer.

microRNA alterations driving acute and late stages of radiation-induced fibrosis in a murine skin model

PURPOSE

Although ionizing radiation is critical in treating cancer, radiation-induced fibrosis (RIF) can have a devastating impact on patients' quality of life. The molecular changes leading to radiation-induced fibrosis must be elucidated so that novel treatments can be designed.

METHODS AND MATERIALS

To determine whether microRNAs (miRs) could be responsible for RIF, the fibrotic process was induced in the right hind legs of 9-week old CH3 mice by a single-fraction dose of irradiation to 35 Gy, and the left leg served as an unirradiated control. Fibrosis was quantified by measurements of leg length compared with control leg length. By 120 days after irradiation, the irradiated legs were 20% (P=.013) shorter on average than were the control legs.

RESULTS

Tissue analysis was done on muscle, skin, and subcutaneous tissue from irradiated and control legs. Fibrosis was noted on both gross and histologic examination by use of a pentachrome stain. Microarrays were performed at various times after irradiation, including 7 days, 14 days, 50 days, 90 days, and 120 days after irradiation. miR-15a, miR-21, miR-30a, and miR-34a were the miRs with the most significant alteration by array with miR-34a, proving most significant on confirmation by reverse transcriptase polymerase chain reaction, c-Met, a known effector of fibrosis and downstream molecule of miR-34a, was evaluated by use of 2 cell lines: HCT116 and 1522. The cell lines were exposed to various stressors to induce miR changes, specifically ionizing radiation. Additionally, in vitro transfections with pre-miRs and anti-miRs confirmed the relationship of miR-34a and c-Met.

CONCLUSIONS

Our data demonstrate an inverse relationship with miR-34a and c-Met; the upregulation of miR-34a in RIF causes inhibition of c-Met production. miRs may play a role in RIF; in particular, miR-34a should be investigated as a potential target to prevent or treat this devastating side effect of irradiation.

Animal model of naturally occurring bladder cancer: characterization of four new canine transitional cell carcinoma cell lines

Background

Development and further characterization of animal models for human cancers is important for the improvement of cancer detection and therapy. Canine bladder cancer closely resembles human bladder cancer in many aspects. In this study, we isolated and characterized four primary transitional cell carcinoma (K9TCC) cell lines to be used for future in vitro validation of novel therapeutic agents for bladder cancer.

Methods

Four K9TCC cell lines were established from naturally-occurring canine bladder cancers obtained from four dogs. Cell proliferation rates of K9TCC cells in vitro were characterized by doubling time. The expression profile of cell-cycle proteins, cytokeratin, E-cadherin, COX-2, PDGFR, VEGFR, and EGFR were evaluated by immunocytochemistry (ICC) and Western blotting (WB) analysis and compared with established human bladder TCC cell lines, T24 and UMUC-3. All tested K9TCC cell lines were assessed for tumorigenic behavior using athymic mice in vivo.

Results

Four established K9TCC cell lines: K9TCC#1Lillie, K9TCC#2Dakota, K9TCC#4Molly, and K9TCC#5Lilly were confirmed to have an epithelial-cell origin by morphology analysis, cytokeratin, and E-cadherin expressions. The tested K9TCC cells expressed UPIa (a specific marker of the urothelial cells), COX-2, PDGFR, and EGFR; however they lacked the expression of VEGFR. All tested K9TCC cell lines confirmed a tumorigenic behavior in athymic mice with 100% tumor incidence.

Conclusions

The established K9TCC cell lines (K9TCC#1Lillie, K9TCC#2Dakota, K9TCC#4Molly, and K9TCC#5Lilly) can be further utilized to assist in development of new target-specific imaging and therapeutic agents for canine and human bladder cancer.

Comparison of the gene expression profiles of human fetal cortical astrocytes with pluripotent stem cell derived neural stem cells identifies human astrocyte markers and signaling pathways and transcription factors active in human astrocytes

Astrocytes are the most abundant cell type in the central nervous system (CNS) and have a multitude of functions that include maintenance of CNS homeostasis, trophic support of neurons, detoxification, and immune surveillance. It has only recently been appreciated that astrocyte dysfunction is a primary cause of many neurological disorders. Despite their importance in disease very little is known about global gene expression for human astrocytes. We have performed a microarray expression analysis of human fetal astrocytes to identify genes and signaling pathways that are important for astrocyte development and maintenance. Our analysis confirmed that the fetal astrocytes express high levels of the core astrocyte marker GFAP and the transcription factors from the NFI family which have been shown to play important roles in astrocyte development. A group of novel markers were identified that distinguish fetal astrocytes from pluripotent stem cell-derived neural stem cells (NSCs) and NSC-derived neurons. As in murine astrocytes, the Notch signaling pathway appears to be particularly important for cell fate decisions between the astrocyte and neuronal lineages in human astrocytes. These findings unveil the repertoire of genes expressed in human astrocytes and serve as a basis for further studies to better understand astrocyte biology, especially as it relates to disease.

Reduced membranous MET expression is linked to bladder cancer progression

The MET protein is involved in the malignant progression of different tumors. This study aimed to analyze the relationship of MET expression with tumor phenotype and clinical outcome in bladder cancer and the role of gene amplification for MET overexpression. A bladder cancer tissue microarray containing 686 bladder cancers was analyzed by immunohistochemistry and by fluorescence in situ hybridization. MET immunostaining was seen in normal urothelium and was recorded in 459 of 560 analyzable urothelial carcinomas (82.0%). Low MET staining was associated with a more unfavorable tumor phenotype. MET staining was seen in 89.8% of 266 pTa, 81.1% of 132 pT1, and 69.4% of 160 pT2-4 cancers (P < 0.0001). MET staining was detectable in 92.4% of 66 grade 1, 85.6% of 257 grade 2, and 75.1% of 237 grade 3 cancers (P = 0.001). MET expression status was not associated with overall or tumor-specific survival in muscle-invasive cancers (pT2-4), tumor progression in pT1 cancers, or recurrences in pTa tumors. Only four of the analyzed tumors (0.8%) showed amplification of the MET gene. We conclude that MET is not overexpressed in urothelial cancer but rather downregulated in a fraction of cancers. Accordingly, rare amplification of the genomic area including the MET gene was not associated with MET protein overexpression.

Patient-derived xenografts reveal limits to PI3K/mTOR- and MEK-mediated inhibition of bladder cancer

BACKGROUND

Metastatic bladder cancer is a serious condition with a 5-year survival rate of approximately 14 %, a rate that has remained unchanged for almost three decades. Thus, there is a profound need to identify the driving mutations for these aggressive tumors to better determine appropriate treatments. Mutational analyses of clinical samples suggest that mutations in either the phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) or RAS/MEK/ERK pathways drive bladder cancer progression, although it remains to be tested whether the inhibition of either (or both) of these pathways can arrest PI3K/mTOR- or Ras-driven proliferation.

METHODS

Herein, we used several bladder cancer cell lines to determine drug sensitivity according to genetic background and also studied mouse models of engrafted UM-UC-3 cells and patient-derived xenografts (PDXs) to test PI3K/mTOR and MEK inhibition in vivo.

RESULTS

Inhibition of these pathways utilizing PF-04691502, a PI3K and mTOR inhibitor, and PD-0325901, a MEK inhibitor, slowed the tumor growth of PDX models of bladder cancer. The growth inhibitory effect of combination therapy was similar to that of the clinical maximum dose of cisplatin; mechanistically, this appeared to predominantly occur via drug-induced cytostatic growth inhibition as well as diminished vascular endothelial growth factor secretion in the tumor models. Kinase arrays of tumors harvested after treatment demonstrated activated p53 and Axl as well as STAT1 and STAT3.

CONCLUSION

Taken together, these results indicate that clinically relevant doses of PF-04691502 and PD-0325901 can suppress bladder tumor growth in PDX models, thus offering additional potential treatment options by a precision medicine approach.

Emerging drugs for urothelial carcinoma

INTRODUCTION

Advanced urothelial carcinoma is associated with a poor prognosis. In the metastatic setting, the response rate to first-line, cisplatin-containing chemotherapy is high, but survival is poor. Second-line treatment options are limited. Advanced age at diagnosis and the presence of comorbidities often preclude treatment with cisplatin-containing regimens.

AREAS COVERED

This review addresses the current therapy of urothelial carcinoma, the unmet needs in treatment and the status of drug development in this disease. The molecular targets identified and efforts to incorporate targeted agents into therapy will be addressed.

EXPERT OPINION

There have been no major advances in the treatment of urothelial carcinoma in three decades. Despite high response rates in the first-line setting, survival is limited. Major impediments to improved outcomes include poor durability of response to first-line chemotherapy and lack of second-line treatments. Better understanding in tumor biology has identified multiple targets in urothelial carcinoma; however, such discoveries have yet to lead to the incorporation of targeted agents into the routine treatment of urothelial carcinoma. Multiple ongoing clinical trials are investigating the use of targeted agents in urothelial carcinoma. Continued efforts are underway to better understand the molecular drivers of disease and such efforts are likely to identify additional therapeutic targets.

The receptor AXL diversifies EGFR signaling and limits the response to EGFR-targeted inhibitors in triple-negative breast cancer cells

The relationship between drug resistance, changes in signaling, and emergence of an invasive phenotype is well appreciated, but the underlying mechanisms are not well understood. Using machine learning analysis applied to the Cancer Cell Line Encyclopedia database, we identified expression of AXL, the gene that encodes the epithelial-to-mesenchymal transition (EMT)-associated receptor tyrosine kinase (RTK) AXL, as exceptionally predictive of lack of response to ErbB family receptor-targeted inhibitors. Activation of EGFR (epidermal growth factor receptor) transactivated AXL, and this ligand-independent AXL activity diversified EGFR-induced signaling into additional downstream pathways beyond those triggered by EGFR alone. AXL-mediated signaling diversification was required for EGF (epidermal growth factor)-elicited motility responses in AXL-positive TNBC (triple-negative breast cancer) cells. Using cross-linking coimmunoprecipitation assays, we determined that AXL associated with EGFR, other ErbB receptor family members, MET (hepatocyte growth factor receptor), and PDGFR (platelet-derived growth factor receptor) but not IGF1R (insulin-like growth factor 1 receptor) or INSR (insulin receptor). From these AXL interaction data, we predicted AXL-mediated signaling synergy for additional RTKs and validated these predictions in cells. This alternative mechanism of receptor activation limits the use of ligand-blocking therapies and indicates against therapy withdrawal after acquired resistance. Further, subadditive interaction between EGFR- and AXL-targeted inhibitors across all AXL-positive TNBC cell lines may indicate that increased abundance of EGFR is principally a means to transactivation-mediated signaling.