4915

NTRK2

Lung cancer is the leading cause of cancer-related mortality worldwide. Recent evidence indicates that tumors contain a subpopulation of cancer stem cells (CSCs) that are responsible for tumor maintenance and spread. CSCs have recently been linked to the occurrence of epithelial-to-mesenchymal transition (EMT). Neurotrophins (NTs) are growth factors that regulate the biology of embryonic stem cells and cancer cells, but still little is known about the role NTs in the progression of lung cancer. In this work, we investigated the role of the NTs and their receptors using as a study system primary cell cultures derived from malignant pleural effusions (MPEs) of patients with adenocarcinoma of the lung. We assessed the expression of NTs and their receptors in MPE-derived adherent cultures vs. spheroids enriched in CSC markers. We observed in spheroids a selectively enhanced expression of TrkB, both at the mRNA and protein levels. Both K252a, a known inhibitor of Trk activity, and a siRNA against TrkB strongly affected spheroid morphology, induced anoikis and decreased spheroid forming efficiency. Treatment with neurotrophins reversed the inhibitory effect of K252a. Importantly, TrkB inhibition caused loss of vimentin expression as well as that of a set of transcription factors known to be linked to EMT. These ex vivo results nicely correlated with an inverse relationship between TrkB and E-cadherin expression measured by immunohistochemistry in a panel of lung adenocarcinoma samples. We conclude that TrkB is involved in full acquisition of EMT in lung cancer, and that its inhibition results in a less aggressive phenotype.

Mechanisms governing the metastasis of endometrial carcinoma (EC) are poorly defined. Recent data support a role for the cell surface receptor tyrosine kinase TrkB in the progression of several human tumors. Here we present evidence for a direct role of TrkB in human EC. Immunohistochemical analysis revealed that TrkB and its secreted ligand, brain-derived neurotrophic factor (BDNF), are more highly expressed in EC than in normal endometrium. High TrkB levels correlated with lymph node metastasis (p<0.05) and lymphovascular space involvement (p<0.05) in EC. Depletion of TrkB by stable shRNA-mediated knockdown decreased the migratory and invasive capacity of cancer cell lines in vitro and resulted in anoikis in suspended cells. Conversely, exogenous expression of TrkB increased cell migration and invasion and promoted anoikis resistance in suspension culture. Furthermore, over-expression of TrkB or stimulation by BDNF resulted in altered the expression of molecular mediators of the epithelial-to-mesenchymal transition (EMT). RNA interference (RNAi)-mediated depletion of the downstream regulator, Twist, blocked TrkB-induced EMT-like transformation. The use of in vivo models revealed decreased peritoneal dissemination in TrkB-depleted EC cells. Additionally, TrkB-depleted EC cells underwent mesenchymal-to-epithelial transition and anoikis in vivo. Our data support a novel function for TrkB in promoting EMT and resistance to anoikis. Thus, TrkB may constitute a potential therapeutic target in human EC.

AIMS: tumour buds in colorectal cancer represent an aggressive subgroup of non-proliferating and non-apoptotic tumour cells. We hypothesize that the survival of tumour buds is dependent upon anoikis resistance. The role of tyrosine kinase receptor B (TrkB), a promoter of epithelial-mesenchymal transition and anoikis resistance, in facilitating budding was investigated. METHODS AND RESULTS: Tyrosine kinase receptor B immunohistochemistry was performed on a multiple-punch tissue microarray of 211 colorectal cancer resections. Membranous/cytoplasmic and nuclear expression was evaluated in tumour and buds. tumour budding was assessed on corresponding whole tissue slides. Relationship to Ki-67 and caspase-3 was investigated. Analysis of Kirsten Ras (KRAS), proto-oncogene B-RAF (BRAF) and cytosine-phosphate-guanosine island methylator phenotype (CIMP) was performed. Membranous/cytoplasmic and nuclear TrkB were strongly, inversely correlated (P < 0.0001; r = -0.41). Membranous/cytoplasmic TrkB was overexpressed in buds compared to the main tumour body (P < 0.0001), associated with larger tumours (P = 0.0236), high-grade budding (P = 0.0011) and KRAS mutation (P = 0.0008). Nuclear TrkB was absent in buds (P <0.0001) and in high-grade budding cancers (P =0.0073). Among patients with membranous/cytoplasmic TrkB-positive buds, high tumour membranous/cytoplasmic TrkB expression was a significant, independent adverse prognostic factor [P = 0.033; 1.79, 95% confidence interval (CI) 1.05-3.05]. Inverse correlations between membranous/cytoplasmic TrkB and Ki-67 (r = -0.41; P < 0.0001) and caspase-3 (r =-0.19; P < 0.05) were observed. CONCLUSIONS: Membranous/cytoplasmic TrkB may promote an epithelial-mesenchymal transition (EMT)-like phenotype with high-grade budding and maintain viability of buds themselves.CI - (c) 2014 John Wiley & Sons Ltd.

BACKGROUND: The aim of the present study was to investigate whether the expression of Brain-Derived Neurotrophic Factor (BDNF) and its receptor Tropomyosin-related kinase B (TrkB) is correlated with the clinical progression of salivary adenoid cystic carcinoma (SACC) and whether the BDNF/TrkB axis is associated with the induction of epithelial-mesenchymal transition (EMT) in SACC cells. METHOD: The expression of BDNF, TrkB, and E-cadherin (an EMT biomarker) in 76 primary SACC specimens and 20 normal salivary gland tissues was analyzed by immunohistochemistry. Additionally, the expression of BDNF, TrkB, and E-cadherin in SACC cell lines (SACC-83 and SACC-LM) was analyzed by RT-PCR and Western blotting. The biological role of the BDNF/TrkB axis in the EMT progression of SACC was evaluated after treatment with increased levels of BDNF and by inhibiting TrkB activity in SACC-83 cell line. The progression of SACC cells through EMT was assessed by RT-PCR, Western blotting, photography, migration and invasion assays. RESULTS: Elevated expression of TrkB (92.1%) and BDNF (89.5%), and downregulated expression of E-cadherin (47.4%) was found in SACC specimens, which was significantly correlated with the invasion and metastasis in SACC (P<0.05). The high expression of TrkB and the low expression of E-cadherin was significantly correlated with the poor prognosis of SACC patients (P<0.05). The expression of TrkB was inversely correlated with the expression of E-cadherin in both SACC cases and cell lines (P<0.05). Increasing BDNF levels after treatment with exogenous recombinant human BDNF (rhBDNF) at 100 ng/ml significantly promoted the activation of TrKB and the progression of EMT in SACC cells. While obstruction of TrkB by its inhibitor, k252a (100 nM), significantly inhibited the EMT progression of SACC cells. CONCLUSIONS: These results suggest that BDNF-mediated TrkB activation contributes to the EMT progression and the poor prognosis in SACC. The present study demonstrated that the BDNF/TrkB axis promotes the migration and invasion of SACC cells via EMT in vitro. Targeting the inactivation of the BDNF/TrkB axis may be a potential strategy for the treatment of SACC.CI - Copyright (c) 2014 Elsevier Ltd. All rights reserved.

BACKGROUND: Neurotrophins (NT) belongs to a family of growth factors which promotes neurons survival and differentiation. Increasing evidence show that NT and their receptor are expressed in lung tissues suggesting a possible role in lung health and disease. Here we investigated the expression and functional role of the TrkB/BDNF axis in idiopathic pulmonary fibrotic lung (myo)fibroblasts. METHODS: Lung fibroblast were isolated from IPF patients and characterized for the expression of mesenchymal markers in comparison to normal lung fibroblasts isolated from non-IPF controls. RESULTS: BDNF treatment promoted mesenchymal differentiation and this effect was counteracted by the TrkB inhibitor K252a. In this regard, we showed that K252a treatment was able to control the expression of transcription factors involved in epithelial to mesenchymal transition (EMT). Accordingly, K252a treatment reduced matrix metalloproteinase-9 enzyme activity and E-cadherin expression while increased cytoplasmic beta-catenin expression. CONCLUSIONS: Our results suggest that BDNF/TrkB axis plays a role in EMT promoting the acquisition of (myo)fibroblast cell phenotype in IPF. Targeting BDNF/TrkB seems to represent a viable approach in order to prevent EMT dependent lung fibrosis.

Brain-derived neurotrophic factor (BDNF) has previously been demonstrated to be associated with several types of cancer. In addition, its receptor, tropomyosin related kinase B (TrkB) is involved in tumor invasion and metastasis. epithelial-mesenchymal transition (EMT) is associated with metastasis in cancers. Thus, The aim of the present study was to examine whether BDNF/TrKB expression is linked to a poor survival and the acquisition of the EMT phenotype in cervical cancer. We found that a high positive expression of BDNF/TrKB was associated with poor survival in cervical cancer. Our results revealed that high expression levels of BDNF/TrKB were observed in cervical cancer compared to normal cells. Importantly, we demonstrated that the silencing of TrKB suppressed the activation of EMT via the downregulation of N-cadherin, vimentin, matrix metalloproteinase (MMP)2 and MMP9, and the upregulation of E-cadherin and tissue inhibitor of metalloproteinases (TIMP)2, which resulted in suppressed cell proliferation, migration and invasion. Furthermore, high phosphorylation levels of ERK and Akt were observed in the cervical cancer cells, while these levels were decreased in the cells in which TrKB was knocked down. On the whole, these findings suggest that the BDNF/TrKB pathway is a promising target for the prevention of tumor proliferation, invasion, metastasis and EMT in cervical cancer cells.