The Trk tyrosine kinase inhibitor K252a regulates growth of lung adenocarcinomas

Adenocarcinomas of the Lung and Neurotrophin System: A Review

Neurotrophins (NTs) represent a group of growth factors with pleiotropic activities at the central nervous system level. The prototype of these molecules is represented by the nerve growth factor (NGF), but other factors with similar functions have been identified, including the brain derived-growth factor (BDNF), the neurotrophin 3 (NT-3), and NT-4/5. These growth factors act by binding specific low (p75) and high-affinity tyrosine kinase (TrkA, TrkB, and TrkC) receptors. More recently, these growth factors have shown effects outside the nervous system in different organs, particularly in the lungs. These molecules are involved in the natural development of the lungs, and their homeostasis. However, they are also important in different pathological conditions, including lung cancer. The involvement of neurotrophins in lung cancer has been detailed most for non-small cell lung cancer (NSCLC), in particular adenocarcinoma. This review aimed to extensively analyze the current knowledge of NTs and lung cancer and clarify novel molecular mechanisms for diagnostic and therapeutic purposes. Several clinical trials on humans are ongoing using NT receptor antagonists in different cancer cell types for further therapeutic applications. The pharmacological intervention against NT signaling may be essential to directly counteract cancer cell biology, and also indirectly modulate it in an inhibitory way by affecting neurogenesis and/or angiogenesis with potential impacts on tumor growth and progression.

Multiplex coherent anti-Stokes Raman scattering microspectroscopy detection of lipid droplets in cancer cells expressing TrkB

For many years, scientists have been looking for specific biomarkers associated with cancer cells for diagnosis purposes. These biomarkers mainly consist of proteins located at the cell surface (e.g. the TrkB receptor) whose activation is associated with specific metabolic modifications. Identification of these metabolic changes usually requires cell fixation and specific dye staining. MCARS microspectroscopy is a label-free, non-toxic, and minimally invasive method allowing to perform analyses of live cells and tissues. We used this method to follow the formation of lipid droplets in three colorectal cancer cell lines expressing TrkB. MCARS images of cells generated from signal integration of CH₂ stretching modes allow to discriminate between lipid accumulation in the endoplasmic reticulum and the formation of cytoplasmic lipid droplets. We found that the number of the latter was related to the TrkB expression level. This result was confirmed thanks to the creation of a HEK cell line which over-expresses TrkB. We demonstrated that BDNF-induced TrkB activation leads to the formation of cytoplasmic lipid droplets, which can be abolished by K252a, an inhibitor of TrkB. So, MCARS microspectroscopy proved useful in characterizing cancer cells displaying an aberrant lipid metabolism.

Role of Tropomyosin-related kinase B receptor and brain-derived neurotrophic factor in cancer

The tropomyosin-related kinase B (TrkB) receptor is a member of the neurotrophic tyrosine kinase receptors family and, together with the brain-derived neurotrophic factor (BDNF), plays an important role in the development of breast cancer, lung cancer, neuroblastoma, colorectal cancer, leukemia, cervical cancer, gallbladder cancer, gastric cancer, kidney cancer, Ewing's sarcoma, esophageal cancer, and head and neck cancer. Overexpression of these two factors has been associated with increased processes involved in carcinogenesis, such as invasion, migration, epithelial-mesenchymal transition (EMT), angiogenesis, metastasis, cell proliferation, resistance to apoptosis, resistance to cell death due to loss of adhesion (anoikis), activation of cell proliferation pathways, regulation of tumor suppressor genes, and drug resistance, and is related to advanced clinical stage. Inhibition of the TrkB/BDNF axis using drugs in phase 1 studies, approved drugs, and small interfering RNA (siRNA) are promising strategies for the treatment of various malignant tumors in addition to increasing the sensitivity of cells resistant to chemotherapy, improving the effectiveness of drugs without increasing toxicity. Another factor related to poor cancer prognosis is the presence of cancer stem cells, having effects similar to the high expression of the TrkB/BDNF axis, on cancer. This review aimed to show the role of the TrkB/BDNF axis in several types of cancer, its possible use as a prognostic biomarker, the effects of inhibiting this axis, and its role in the cancer stem cells.

Angiogenesis in Gynecological Cancers: Role of Neurotrophins

Angiogenesis, or generation of new blood vessels from other pre-existing, is a key process to maintain the supply of nutrients and oxygen in tissues. Unfortunately, this process is exacerbated in pathologies such as retinopathies and cancers with high angiogenesis as ovarian cancer. Angiogenesis is regulated by multiple systems including growth factors and neurotrophins. One of the most studied angiogenic growth factors is the vascular endothelial growth factor (VEGF), which is overexpressed in several cancers. It has been recently described that neurotrophins could regulate angiogenesis through direct and indirect mechanisms. Neurotrophins are a family of proteins that include nerve growth factor (NGF), brain-derived growth factor (BDNF), and neurotrophins 3 and 4/5 (NT 3, NT 4/5). These molecules and their high affinity receptors (TRKs) regulate the development, maintenance, and plasticity of the nervous system. Furthermore, it was recently described that they display essential functions in non-neuronal tissues, such as reproductive organs among others. Studies have shown that several types of cancer overexpress neurotrophins such as NGF and BDNF, which might contribute to tumor progression and angiogenesis. Besides, in recent years the FDA has approved the use of pharmacologic inhibitors of pan-TRK receptors in patients with TRKs fusion-positive cancers. In this review, we discuss the mechanisms by which neurotrophins stimulate tumor progression and angiogenesis, with emphasis on gynecological cancers.

ProNGF siRNA inhibits cell proliferation and invasion of pancreatic cancer cells and promotes anoikis

BACKGROUND

Precursor of nerve growth factor (proNGF) was previously considered biologically inactive; however, it has recently been identified as having important roles in the pathology of cancer development.

AIM

This study aimed to explore the therapeutic effects of proNGF siRNA on the proliferation, invasion, and anoikis of pancreatic cancer cells and determine the functions of proNGF.

METHODS

Pancreatic ductal adenocarcinoma (PDAC) and paired paracancerous tissue samples were collected from 60 patients for evaluation of proNGF expression by immunohistochemistry staining, qPCR, and western blotting. PDAC cell proliferation, migration, apoptosis, and anoikis following proNGF siRNA knockdown were investigated in two pancreatic cancer cell lines, Panc-1 and Bxpc-3, using BrdU incorporation assays, EdU staining, Ki-67 immunofluorescence (IF) staining, wound-healing assays, transwell invasion assays, and EthD-1 IF staining. Autophagy-related proteins were also measured by western blotting.

RESULTS

Levels of proNGF protein were higher in pancreatic cancer tissues and cells lines than those in paracancerous tissues and normal pancreatic duct epithelial cells, respectively. In vitro, ProNGF knockdown by siRNA led to significantly reduced cell proliferation, remarkably inhibited wound-healing, and reduced the number of invaded PDAC cells in migration and transwell assays. Treatment with proNGF siRNA also downregulated ATG5 and Beclin 1 protein levels, increased those of P62, and increased EthD-1 staining in PDAC cells.

CONCLUSION

ProNGF expression is elevated in PDAC tissues and cell lines, and proNGF siRNA can inhibit cell proliferation, migration, and invasion, and promote anoikis of pancreatic cancer cells, in which decreased proNGF may participate.

The neurotrophic tyrosine kinase receptor TrkA and its ligand NGF are increased in squamous cell carcinomas of the lung

The neurotrophic tyrosine kinase receptor TrkA (NTRK1) and its ligand nerve growth factor (NGF) are emerging promoters of tumor progression. In lung cancer, drugs targeting TrkA are in clinical trials, but the clinicopathological significance of TrkA and NGF, as well as that of the precursor proNGF, the neurotrophin co-receptor p75^NTR and the proneurotrophin co-receptor sortilin, remains unclear. In the present study, analysis of these proteins was conducted by immunohistochemistry and digital quantification in a series of 204 lung cancers of different histological subtypes versus 121 normal lung tissues. TrkA immunoreactivity was increased in squamous cell carcinoma compared with benign and other malignant lung cancer histological subtypes (p < 0.0001). NGF and proNGF were also increased in squamous cell carcinoma, as well as in adenocarcinoma (p < 0.0001). In contrast, p75^NTR was increased across all lung cancer histological subtypes compared to normal lung (p < 0.0001). Sortilin was higher in adenocarcinoma and small cell carcinoma (p < 0.0001). Nerves in the tumor microenvironment were negative for TrkA, NGF, proNGF, p75^NTR and sortilin. In conclusion, these data suggest a preferential therapeutic value of targeting the NGF-TrkA axis in squamous cell carcinomas of the lung.

Prediction of potential drivers connecting different dysfunctional levels in lung adenocarcinoma via a protein-protein interaction network

Lung cancer is a serious disease that threatens an affected individual's life. Its pathogenesis has not yet to be fully described, thereby impeding the development of effective treatments and preventive measures. "Cancer driver" theory considers that tumor initiation can be associated with a number of specific mutations in genes called cancer driver genes. Four omics levels, namely, (1) methylation, (2) microRNA, (3) mutation, and (4) mRNA levels, are utilized to cluster cancer driver genes. In this study, the known dysfunctional genes of these four levels were used to identify novel driver genes of lung adenocarcinoma, a subtype of lung cancer. These genes could contribute to the initiation and progression of lung adenocarcinoma in at least two levels. First, random walk with restart algorithm was performed on a protein-protein interaction (PPI) network constructed with PPI information in STRING by using known dysfunctional genes as seed nodes for each level, thereby yielding four groups of possible genes. Second, these genes were further evaluated in a test strategy to exclude false positives and select the most important ones. Finally, after conducting an intersection operation in any two groups of genes, we obtained several inferred driver genes that contributed to the initiation of lung adenocarcinoma in at least two omics levels. Several genes from these groups could be confirmed according to recently published studies. The inferred genes reported in this study were also different from those described in a previous study, suggesting that they can be used as essential supplementary data for investigations on the initiation of lung adenocarcinoma. This article is part of a Special Issue entitled: Accelerating Precision Medicine through Genetic and Genomic Big Data Analysis edited by Yudong Cai & Tao Huang.

Brain-derived neurotrophic factor/tropomyosin-related kinase B signaling pathway contributes to the aggressive behavior of lung squamous cell carcinoma

The tropomyosin-related kinase (Trk) family consists of TrkA, TrkB, and TrkC, which play essential roles in tumor progression and/or suppression in various cancers. Little is known about the biological significance of the Trk family in human lung squamous cell carcinoma (SCC). Here we investigated the clinical significance of the protein expression of Trk family members in samples from 99 SCC patients, and we explored the relationship between invasion/proliferation activities and Trk expression using lung SCC cell lines to clarify the biological significance of the Trk family in lung SCC. Immunohistochemical high expression of TrkB was significantly correlated with vascular invasion (P=0.004), lymph node metastasis (P<0.001), and advanced stage (P=0.0015). The overall survival of the patients with TrkB-high expression was significantly shorter than those with TrkB-low expression (P=0.0110). TrkA/TrkC expressions were not predictors of poor prognosis. An in vitro assay demonstrated that the inhibition of brain-derived neurotrophic factor (BDNF) (a TrkB ligand) and TrkB by K252a (a Trk inhibitor) or siRNA (BDNF-siRNA, TrkB-siRNA) suppressed the invasion, migration, and proliferative activities of lung SCC cells. The administration of recombinant human BDNF (rhBDNF) enhanced the invasion, migration, and proliferation activities, which were abrogated by K252a. TrkB-siRNA transfection increased the protein expression of E-cadherin and decreased vimentin expressions in lung SCC cells. Matrix metalloproteinase-2 (MMP-2)-mediated gelatin degradations were decreased in lung SCC cells transfected with TrkB-siRNA. Thus, TrkB-high expression is an indicator of poor prognosis in lung SCC, probably due to invasion/proliferation activities promoted by the BDNF/TrkB signaling pathway, which could become a therapeutic target for lung SCC.

BDNF/TrkB axis activation promotes epithelial-mesenchymal transition in idiopathic pulmonary fibrosis

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 β-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.

siRNA-mediated inhibition of endogenous brain‑derived neurotrophic factor gene modulates the biological behavior of HeLa cells

Brain-derived neurotrophic factor (BDNF) is expressed in a number of neural and non-neuronal tumors. The present study investigated the effect of endogenous BDNF on the biological behavior of cervix cancer cells using small interfering RNA (siRNA). HeLa, a cervix cancer cell line with high expression of BDNF, was used as a living model to screen out the effective sequences of short hairpin RNA of the BDNF gene, and the effects of RNA interference on proliferation, apoptosis, migration and invasion of these cells were evaluated. Among the 4 siRNAs examined, siRNA1 caused a 99% reduction in the relative BDNF mRNA level, while a 58% decrease in the relative BDNF protein level (p<0.01) was noted, and thus this siRNA was selected as the most efficient for use in the present study. In subsequent experiments, MTT assay revealed that BDNF silencing caused marked inhibition of HeLa cell proliferation while Hoechst 33258 staining assay demonstrated apoptosis-related changes in cell morphology. Downregulation of BDNF expression induced cell cycle arrest in the G1 phase as shown by flow cytometry. As indicated by Transwell migration and invasion assays, downregulation of BDNF expression suppressed the migratory and invasive capabilities of the HeLa cells. Together, our data revealed that BDNF modulates the proliferation, apoptosis, migratory and invasive capabilities of HeLa cells. BDNF siRNA may represent a novel therapy or drug target for preventing the tumorigenesis of cervical cancer.

Deletion of cyclooxygenase-2 inhibits K-ras-induced lung carcinogenesis

The purpose of this study was to identify the role COX-2 plays in K-ras–induced lung carcinogenesis. We crossed COX-2–homozygous knockout mice with K-ras^LA1 (G12D) expressing mice to obtain COX-2–deficient mice with K-ras expression (K-ras/COX-2^−/− mice) and COX-2 wild type mice with K-ras expression (K-ras mice). At 3.5 months of age, the K-ras/COX-2^−/− mice had significantly fewer lung adenocarcinomas and substantially smaller tumors than K-ras mice. K-ras/COX-2^−/− mice also had significantly fewer bronchioalveolar hyperplasias than K-ras mice. Compared with lung tumors from K-Ras mice, the levels of prostaglandin E₂ (PGE₂) were significantly lower, whereas levels of the PGE₂ metabolite 13,14-dihydro-15-keto-PGE₂ were significantly higher, in lung tumors from K-ras/COX-2^−/− mice. In addition, K-ras/COX-2^−/− mice had strikingly lower rates of tumor cell proliferation and expressed less MEK and p-Erk1/2 protein than K-ras mice did. In line with this, knocking down COX-2 in mutant K-ras non-small cell lung cancer A549 cells reduced colony formation, PGE₂ synthesis and ERK phosphorylation compared to that of vector control cells. Taken together, these findings suggest that COX-2 deletion contributes to the repression of K-ras–induced lung tumorigenesis by reducing tumor cell proliferation, decreasing the production of PGE₂, and increasing the production of 13,14-dihydro-15-keto-PGE₂, possibly via the MAPK pathway. Thus, COX-2 is likely important in lung tumorigenesis, and COX-2 and its product, PGE₂, are potential targets for lung cancer prevention.

Neurotrophins and B-cell malignancies

Neurotrophins and their receptors act as important proliferative and pro-survival factors in a variety of cell types. Neurotrophins are produced by multiple cell types in both pro- and mature forms, and can act in an autocrine or paracrine fashion. The p75(NTR) and Trk receptors can elicit signalling in response to the presence or absence of their corresponding neurotrophin ligands. This signalling, along with neurotrophin and receptor expression, varies between different cell types. Neurotrophins and their receptors have been shown to be expressed by and elicit signalling in B lymphocytes. In general, most neurotrophins are expressed by activated B-cells and memory B-cells. Likewise, the TrkB95 receptor is seen on activated B-cells, while TrkA and p75(NTR) are expressed by both resting and active B-cells as well as memory B-cells. Nerve growth factor stimulates B-cell proliferation, memory B-cell survival, antibody production and CD40 expression. Brain-derived neurotrophic factor is involved in B-cell maturation in the bone marrow through TrkB95. Overall neurotrophins and their receptors have been shown to be involved in B-cell proliferation, development, differentiation, antibody secretion and survival. As well as expression and activity in healthy B-cells, the neurotrophins and their receptors can contribute to B-cell malignancies including acute lymphoblastic leukaemia, diffuse large B-cell lymphoma, Burkitt's lymphoma and multiple myeloma. They are involved in B-cell malignancy survival and potentially in drug resistance.

MET inhibitors in combination with other therapies in non-small cell lung cancer

MET and its ligand hepatocyte growth factor/scatter factor (HGF) influence cell motility and lead to tumor growth, invasion, and angiogenesis. Alterations in MET have been observed in non-small cell lung cancer (NSCLC) tumors, with increased expression associated with more aggressive cancer, as well as acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI). MET inhibitors act via two basic mechanisms. Small molecule inhibitors antagonize ATP in the intracellular tyrosine kinase domain of MET, with studies on the following agents reviewed here: tivantinib (ARQ-197), cabozantinib (XL-184), crizotinib (PF-02341066), amuvatinib (MP470), MGCD265, foretinib (EXEL-2880), MK2461, SGX523, PHA665752, JNJ-38877605, SU11274, and K252A. The monoclonal monovalent antibody fragment onartuzumab (MetMAb) is also discussed here, which binds to and prevents the extracellular activation of the receptor by ligand. MET inhibition may both overcome the negative prognostic effect of MET tumor expression as well as antagonize MET-dependent acquired resistance to EGFR inhibitors. Here we discuss MET inhibitors in combination with other therapies in lung cancer.

Tropomyosin-related kinase B promotes distant metastasis of colorectal cancer through protein kinase B-mediated anoikis suppression and correlates with poor prognosis

An increasing amount of evidence demonstrated that the neurotrophic receptor tropomyosin-related kinase B (TrkB) plays a critical role in the development and progression of multiple types of cancer. However, its underlying mechanism in distant metastasis through the circulatory and lymphatic systems in colorectal cancer (CRC) is still unclear. Here we showed that downregulation of TrkB using short hairpin RNA obviously increased anoikis (detachment-induced apoptosis resulting from loss of cell-matrix interactions) sensitivity of CRC cells in vitro. Furthermore, using tail vein injection model, we confirmed that silencing TrkB significantly inhibited metastasis of CRC cells in vivo. Conversely, overexpression of TrkB obviously protected CRC cells from anoikis in vitro. Both loss- and gain-of-functional experiments indicated that TrkB could be a functional molecule in anti-anoikis of CRC cells. Mechanistically, we found that protein kinase B (PKB, also known as Akt) signaling pathway was a functional link in TrkB-induced anoikis suppression in CRC cells. Phosphorylation levels of Akt are closely related with the expression pattern of TrkB in CRC cells and inhibition of Akt activation robustly induces anoikis of CRC cells in vitro. In addition, our clinical investigation showed that high TrkB expression levels in CRC patients were associated with lymph node metastasis, distant metastasis and unfavourable prognosis. Thus, based on our results, this study suggests that an important function of TrkB is to protect CRC cells from anoikis in the circulatory and lymphatic systems, and that TrkB could be a promising candidate in CRC therapy, especially in the inhibition of cancer metastasis.

Neurotrophin receptor TrkB promotes lung adenocarcinoma metastasis

Lung cancer is notorious for its ability to metastasize, but the pathways regulating lung cancer metastasis are largely unknown. An in vitro system designed to discover factors critical for lung cancer cell migration identified brain-derived neurotrophic factor, which stimulates cell migration through activation of tropomyosin-related kinase B (TrkB; also called NTRK2). Knockdown of TrkB in human lung cancer cell lines significantly decreased their migratory and metastatic ability in vitro and in vivo. In an autochthonous lung adenocarcinoma model driven by activated oncogenic Kras and p53 loss, TrkB deficiency significantly reduced metastasis. Hypoxia-inducible factor-1 directly regulated TrkB expression, and, in turn, TrkB activated Akt signaling in metastatic lung cancer cells. Finally, TrkB expression was correlated with metastasis in patient samples, and TrkB was detected more often in tumors that did not have Kras or epidermal growth factor receptor mutations. These studies demonstrate that TrkB is an important therapeutic target in metastatic lung adenocarcinoma.

Clinical significance of TrkB expression in nasopharyngeal carcinoma

Recent research has demonstrated that tropomyosin‑related kinase B (TrkB) plays an important role in neuronal survival, differentiation and migration; yet, its specific role in human nasopharyngeal carcinoma (NPC) is unclear. To elucidate its role in NPC, we examined TrkB expression in NPC tissues and cell lines, and investigated the correlation between TrkB expression and prognosis in patients with NPC. Immunohistochemical analysis was performed on NPC specimens from 108 patients with follow-up information. Additionally, reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analyses were used to determine TrkB expression levels in NPC and noncancerous nasopharyngeal tissues. RT-PCR and western blot analyses were also used to determine TrkB expression levels in 7 NPC cell lines and a nasopharyngeal epithelium cell line. High TrkB expression was significantly correlated with T classification, lymph node metastasis and clinical stage, respectively. Patients with NPC who had high TrkB expression had reduced disease-free survival and overall survival when compared with patients who had low TrkB expression. Multivariate Cox regression analysis revealed that TrkB overexpression was an independent prognostic factor for patients with NPC. Furthermore, TrkB was overexpressed in NPC specimens and cell lines. TrkB expression levels were significantly increased in NPC specimens, and enhanced levels were correlated with a poor prognosis in patients with NPC. These findings suggest that TrkB may contribute to NPC progression and represent a novel prognostic indicator for patients with NPC.

TrkB is responsible for EMT transition in malignant pleural effusions derived cultures from adenocarcinoma of the lung

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.

Peripheral immune cell gene expression changes in advanced non-small cell lung cancer patients treated with first line combination chemotherapy

Introduction

Increasing evidence has shown that immune surveillance is compromised in a tumor-promoting microenvironment for patients with non-small cell lung cancer (NSCLC), and can be restored by appropriate chemotherapy.

Methods

To test this hypothesis, we analyzed microarray gene expression profiles of peripheral blood mononuclear cells from 30 patients with newly-diagnosed advanced stage NSCLC, and 20 age-, sex-, and co-morbidity-matched healthy controls. All the patients received a median of four courses of chemotherapy with cisplatin and gemcitabine for a 28-day cycle as first line treatment.

Results

Sixty-nine differentially expressed genes between the patients and controls, and 59 differentially expressed genes before and after chemotherapy were identified. The IL4 pathway was significantly enriched in both tumor progression and chemotherapy signatures. CXCR4 and IL2RG were down-regulated, while DOK2 and S100A15 were up-regulated in the patients, and expressions of all four genes were partially or totally reversed after chemotherapy. Real-time quantitative RT-PCR for the four up-regulated (S100A15, DOK2) and down-regulated (TLR7, TOP1MT) genes in the patients, and the six up-regulated (TLR7, CRISP3, TOP1MT) and down-regulated (S100A15, DOK2, IL2RG) genes after chemotherapy confirmed the validity of the microarray results. Further immunohistochemical analysis of the paraffin-embedded lung cancer tissues identified strong S100A15 nuclear staining not only in stage IV NSCLC as compared to stage IIIB NSCLC (p = 0.005), but also in patients with stable or progressive disease as compared to those with a partial response (p = 0.032). A high percentage of S100A15 nuclear stained cells (HR 1.028, p = 0.01) was the only independent factor associated with three-year overall mortality.

Conclusions

Our results suggest a potential role of the IL4 pathway in immune surveillance of advanced stage NSCLC, and immune potentiation of combination chemotherapy. S100A15 may serve as a potential biomarker for tumor staging, and a predictor of poor prognosis in NSCLC.

Diagnostic value of neurotrophin expression in malignant pleural effusions

Neurotrophins (NTs) modulate the growth of human malignancies, including lung cancers. Our prospective study evaluated the accuracy of pleural NTs [nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotrophin 3 (nT3) and 4 (nT4)] levels for differentiating benign from malignant pleural exudates. Levels of NTs were measured by ELISA in 170 patients with non-neutrophilic (<50%) exudative benign or malignant pleurisies diagnosed by pleuroscopy. Fifty-nine benign (9 infections and 50 inflammatory diseases) and 111 malignant (50 extrathoracic tumors, 51 lung cancers and 10 mesotheliomas) pleural exudates were diagnosed by thoracoscopy. Levels of BDNF were significantly higher in malignant than in benign effusions [17 pg/ml (0-367) vs. 8 pg/ml (0-51), p<0.05]. ROC analysis showed an area under the curve of 0.609 (p=0.012; best threshold 44 pg/ml). Pleural BDNF levels were significantly higher in pleural metastasis of pulmonary tumors and in mesothelioma than in pleural benign effusions. Finally, a higher proportion of pleural nT3 was detected in squamous cell lung carcinoma in comparison to that in non-squamous cell lung carcinoma (72.7 vs. 10%, p<0.0001). NTs and particularly BDNF may play a role in the pathogenesis of malignant pleural effusions.

Influence of GRPR and BDNF/TrkB signaling on the viability of breast and gynecologic cancer cells

Neuropeptide and neurotrophin receptors are increasingly important molecular targets in cancer. Scientific findings indicate that compounds blocking gastrin-releasing peptide receptors (GRPR) or tropomyosin receptor kinase (Trk) receptors are likely to have antiproliferative activities against cancer cells. The present study aimed to demonstrate that, in contrast to previous findings, GRPR activation reduces, whereas its blockade increases the viability of breast, ovarian and cervical cancer cell lines. However, consistent with previous studies, Trk inhibition was demonstrated to reduce the viability of these cells. MCF-7 (breast), OVCAR-3 (ovarian) and HeLa (cervical) human cancer cell lines were treated with GRP, the GRPR antagonists RC-3095 and RC-3940-II, brain-derived neurotrophic factor (BDNF) and the Trk antagonist K252α. Cell viability was measured by the MTT assay. Expression of GRPR and BDNF was confirmed with reverse transcription-polymerase chain reaction (RT-PCR). GRP reduced, whereas RC-3940-II enhanced the viability of the three cell lines. Treatment with K252α inhibited the viability of the cell lines, while BDNF increased the viability of OVCAR-3 cells. The results supported the hypothesis that GRPR and BDNF/TrkB signaling regulates cancer cell viability. Most importantly, these findings are the first to demonstrate that GRPR blockade can stimulate, rather than inhibits the viability of breast and gynecologic cancer cell lines.

High TrkB expression levels are associated with poor prognosis and EMT induction in colorectal cancer cells

BACKGROUND

The neurotrophic receptor tropomyosin related kinase (TrkB) is associated with tumor progression in neuroblastoma and certain human malignancies. Recent reports indicate TrkB may participate in the epithelial-mesenchymal transition (EMT). This study investigates whether TrkB expression is associated with the clinical outcome of colorectal cancer (CRC) patients and whether TrkB induces EMT in CRC cells.

METHODS

TrkB and E-cadherin expression in surgical tissue samples and clinicopathological data from 102 CRC patients were analyzed by real-time polymerase chain reaction and immunohistochemistry. The biological role of TrkB in CRC was analyzed using RNA interference against TrkB in the CRC cell line SW480 to assess tumor progression and the correlation between TrkB and E-cadherin expression.

RESULTS

Patients with high TrkB mRNA expression in clinical samples had a significantly poorer prognosis relative to those with low TrkB levels (p = 0.03). TrkB was inversely correlated with E-cadherin at both the mRNA and protein levels. In vitro, cell proliferation (p = 0.02), migration (p < 0.001), and invasion (p < 0.001) were significantly inhibited by TrkB knockdown while the anoikis rate increased in TrkB siRNA-transfected cells compared to control siRNA. Interestingly, E-cadherin expression in TrkB siRNA-transfected cells was higher than in control cells and vimentin was lower conversely.

CONCLUSIONS

High TrkB expression is associated with poor prognosis in CRC patients and enhanced malignant potential in terms of proliferation, migration, invasion, and anoikis inhibition in CRC cells. These results indicate TrkB could induce EMT and play an important role in CRC progression to metastasis.

Kinomic profiling approach identifies Trk as a novel radiation modulator

BACKGROUND

Ionizing radiation treatment is used in over half of all cancer patients, thus determining the mechanisms of response or resistance is critical for the development of novel treatment approaches.

MATERIALS AND METHODS

In this report, we utilize a high-content peptide array platform that performs multiplex kinase assays with real-time kinetic readout to investigate the mechanism of radiation response in vascular endothelial cells. We applied this technology to irradiated human umbilical vein endothelial cells (HUVEC).

RESULTS

We identified 49 specific tyrosine phosphopeptides that were differentially affected by irradiation over a time course of 1h. In one example, the Tropomyosin receptor kinase (Trk) family members, TrkA and TrkB, showed transient activation between 2 and 15 min following irradiation. When we targeted TrkA and TrkB using small molecule inhibitors, HUVEC were protected from radiation damage. Conversely, stimulation of TrkA using gambogic amide promoted radiation enhancement.

CONCLUSIONS

Thus, we show that our approach not only can identify rapid changes in kinase activity but also identify novel targets such as TrkA. TrkA inhibition resulted in radioprotection that correlated with enhanced repair of radiation-induced damage while TrkA stimulation by gambogic amide produced radiation sensitization.

More expressions of BDNF and TrkB in multiple hepatocellular carcinoma and anti-BDNF or K252a induced apoptosis, supressed invasion of HepG2 and HCCLM3 cells

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and its receptor Tropomysin-related kinase B (TrkB) are commonly up-regulated in a variety of human tumors. However, the roles of BDNF/TrkB in hepatocellular carcinoma (HCC) have been poorly investigated.

METHODS

We evaluated the expressions of BDNF and TrkB in 65 cases of HCC by immunohistochemical staining. Moreover, in human HCC cell lines of HepG2 and high metastatic HCCLM3, the secretory BDNF in supernatant was measured by ELISA, the effects of BDNF neutralizing antibody or Trk tyrosine kinase inhibitor K252a on apoptosis and invasion were examined by flow cytometry and transwell assay respectively.

RESULTS

Higher expression of BDNF (63.1%) or positive expression of TrkB (55.4%) was found in HCC specimens, which was significantly correlated with multiple and advanced stage of HCC. BDNF secretory level in HCCLM3 was higher than that in HepG2 cells. Both anti-BDNF and K252a effectively induced apoptosis and suppressed invasion of HepG2 and HCCLM3 cells.

CONCLUSIONS

These findings suggested that BDNF/TrkB are essential for HCC cells survival and invasion. BDNF/TrkB signaling should probably be an effective target to prevent HCC advancement.

Immunohistochemical expression of neurotrophic tyrosine kinase receptors 1 and 2 in lung carcinoma: potential discriminators between squamous and nonsquamous subtypes

CONTEXT

The neurotrophic tyrosine kinase receptors NTRK1 and NTRK2 have been implicated in the pathogenesis of lung carcinomas. NTRK receptor expression has been reported in lung carcinomas; however, the clinical utility of immunohistochemical expression of these receptors is unclear.

OBJECTIVE

To compare the immunohistochemical expression profiles of NTRK1 and NTRK2 in various histologic subtypes of lung carcinomas and correlate with patient outcome.

DESIGN

Six hundred eighty-six unique lung cancer cases (including squamous cell carcinoma, adenocarcinoma, large cell carcinoma, small cell carcinoma, and carcinoid tumor) with clinical outcome data in tissue microarray format were immunohistochemically stained for NTRK1 and NTRK2 using commercially available antibodies, automated immunostaining, and standard protocols.

RESULTS

Expression of both NTRK1 and NTRK2 correlates strongly with squamous histology. NTRK1 and NTRK2 are highly specific markers (1: 92.8%, 2: 96.4%) of squamous lung carcinoma when compared with the other carcinoma subtypes, including adenocarcinoma. Positive NTRK2 staining in squamous carcinoma correlates with improved disease-specific survival (P < .001) and overall survival (P  =  .047).

CONCLUSIONS

NTRK1 and NTRK2 are potentially useful immunohistochemical markers that may be particularly helpful in separating squamous cell carcinoma from adenocarcinoma.

Neurotrophic tyrosine kinase receptor B/neurotrophin 4 signaling axis is perturbed in clinical and experimental pulmonary fibrosis

The neurotrophins (NTs) are emerging as exciting new participants in normal lung physiology, as well as in several pathological processes in diseased lungs. In this study, the increased expression of NT4/5 and of its cognate receptor, the neurotrophic tyrosine kinase receptor Type 2 (TrkB), was observed in human lungs explanted from patients with idiopathic pulmonary fibrosis (IPF), and in lungs from mice with bleomycin-induced pulmonary fibrosis. The expression of NT4/5 and TrkB localized to hyperplastic alveolar Type II cells (ATII) and fibroblastic foci in affected lungs. Increased concentrations of NT4/5 and TrkB were evident in ATII isolated from the lungs of bleomycin-treated mice. Primary ATII were shown to secrete NT4/5 into the cell culture medium. The profibrotic cytokine transforming growth factor-β1, stimulated TrkB, but not NT4/5 gene expression, suggesting that perturbed profibrotic growth factor signaling in affected lungs may drive the expression of TrkB. NT4/5 enhanced the proliferation of ATII through a TrkB/extracellular-regulated kinase/protein kinase B pathway, and could also drive the proliferation of primary human and murine lung fibroblasts, through TrkB-dependent and protein kinase B-dependent pathways. Taken together, these data suggest that a dysregulated TrkB/NT4/5 axis may contribute to several of the pathological lesions associated with pulmonary fibrosis, including ATII hyperplasia and the proliferation of fibroblasts, and we would add IPF to the list of disorders, such as pain and cancer, for which therapeutic targeting of the TrkB/neurotrophin axis has been proposed for further investigation.

Neurotrophins in lung health and disease

Neurotrophins (NTs) are a family of growth factors that are well-known in the nervous system. There is increasing recognition that NTs (nerve growth factor, brain-derived neurotrophic factor and NT3) and their receptors (high-affinity TrkA, TrkB and TrkC, and low-affinity p75NTR) are expressed in lung components including the nasal and bronchial epithelium, smooth muscle, nerves and immune cells. NT signaling may be important in normal lung development, developmental lung disease, allergy and inflammation (e.g., rhinitis, asthma), lung fibrosis and even lung cancer. In this review, we describe the current status of our understanding of NT signaling in the lung, with hopes of using aspects of the NT signaling pathway in the diagnosis and therapy of lung diseases.

K252a induces anoikis-sensitization with suppression of cellular migration in Epstein-Barr virus (EBV)--associated nasopharyngeal carcinoma cells

Recent studies revealed an unexpected role of the neurotrophin receptor pathway, BDNF/TrkB signaling, in cancer metastasis and anoikis (i.e. detachment-induced cell death). Survival of cancer cells in detached state (known as anoikis-resistance) is known to be pre-requisite for metastasis. Nasopharyngeal carcinoma (NPC), an endemic head and neck cancer in Southeast Asia, is highly invasive, metastatic, and etiologically associated with Epstein-Barr virus (EBV, an oncovirus) infection. Mechanistic studies on the invasive/metastatic nature of NPC can facilitate the development of anti-metastatic therapy in NPC. Thus far, the role of BDNF/TrkB signaling in virus-associated human cancer is unclear. Here, using multiple cell line models of NPC with EBV-association (HONE-1-EBV, HK1-LMP1 and C666-1), we investigated the potential involvement of BDNF/TrkB signaling in cellular migration and anoikis-resistant characteristics of NPC. We found that all three EBV-associated NPC cell lines tested were intrinsically anoikis-resistant (i.e. survived in detached state) and expressed both BDNF and TrkB. BDNF stimulation induced cellular migration, but not proliferation of these cells. Further, we examined if pharmacologic targeting of anoikis-resistance of NPC cells can be achievable by a proof-of-concept Trk inhibitor, K252a, in these EBV-associated NPC models. Our results demonstrated that K252a, was able to attenuate BDNF-induced migration and proliferation of NPC cells. More importantly, we demonstrated for the first time that K252a harbored potent anoikis-sensitization activity (i.e. sensitizing cancer cells to detachment-induced cell death) against EBV-associated human cancer cells, namely NPC cells. This proof-of-concept study demonstrated that K252a, a Trk inhibitor, can potentially be used as an anoikis-sensitizing agent in NPC.

Neurotrophin system activation in pleural effusions

Neurotrophins (NTs) expression was assessed in malignant and non-malignant pleural effusions (inflammatory exudates and transudates). Enzyme-linked immunosorbent assay, in malignant exudates from small and non-small cell lung cancer (SCLC and NSCLC), detected nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), and their levels are higher as compared with inflammatory and transudative effusions. By immunoblots, in cultured cancer cells coming from malignant pleural effusions, NTs and low- and high-affinity NT receptors were detected in a percentage of SCLC and NSCLC. Proliferation assay demonstrated that BDNF significantly increased cancer cell proliferation in vitro, on the contrary, NT-3 reduced cancer cell growth rate and NGF did not modify cell growth. Moreover, NGF protects cells from death during starvation. These effects are reverted by the addition of NT receptor antagonists. Cultured cancer cells injected into the lung of immunodeficient mice generate lung tumors expressing NTs and NT receptors. These findings suggest that NTs may be able to modulate cancer cell behavior and their growth.

Angiostatic effects of K252a, a Trk inhibitor, in murine brain capillary endothelial cells

Nerve growth factor (NGF) supports the survival and differentiation of sympathetic and sensory neurons and is also mitogenic for a variety of tumors. K252a, an antagonist of NGF receptor TrkA, was previously used as a pharmacological tool to study NGF actions and as a lead compound for developing anti-tumor drugs. Since recently, NGF was characterized as an angiogenic factor, we sought to investigate the angiostatic properties of K252a on endothelial cells (ECs). For this purpose, we used a murine brain microcapillary ECs model in which we found autocrine release of NGF in the culture medium and activation of TrkA receptor-induced downstream signaling molecules Erk1/2, Akt, and PLCgamma. In this model, we demonstrated the angiostatic property of K252a based on its ability to affect several important angiogenic steps. K252a, but not its cell membrane impermeable analogue K252b at 100 nM: (i) inhibited the proliferation of the ECs by 45 +/- 9%; (ii) reduced by 70 +/- 4% the migration of the ECs measured in a wound-closure model; (iii) reduced by 29 +/- 9% the formation of tube-like structures of the ECs cultured on Matrigel; (iv) stimulated by 100 +/- 25% the collagen deposition by the ECs, a process responsible for the increased endothelial barrier functions expressed by 22 +/- 5% reduction of paracellular permeability and by 17 +/- 3% elevation of transendothelial electrical resistance. These data suggest that NGF/TrkA may represent a target for the development of novel, K252a-derived multikinase inhibitors drugs with anti-tumor and angiostatic dual activities.

Chemical genetics identifies small-molecule modulators of neuritogenesis involving neuregulin-1/ErbB4 signaling

Genetic findings have suggested that neuregulin-1 (Nrg1) and its receptor v-erb-a erythroblastic leukemia viral oncogene homolog 4 (ErbB4) may play a role in neuropsychiatric diseases. However, the downstream signaling events and relevant phenotypic consequences of altered Nrg1 signaling in the nervous system remain poorly understood. To identify small molecules for probing Nrg1-ErbB4 signaling, a PC12-cell model was developed and used to perform a live-cell, image-based screen of the effects of small molecules on Nrg1-induced neuritogenesis. By comparing the resulting phenotypic data to that of a similar screening performed with nerve growth factor (NGF), this multidimensional screen identified compounds that directly inhibit Nrg1-ErbB4 signaling, such as the 4-anilino-quinazoline Iressa (gefitinib), as well as compounds that potentiate Nrg1-ErbB4 signaling, such as the indolocarbazole K-252a. These findings provide new insights into the regulation of Nrg1-ErbB4 signaling events and demonstrate the feasibility of using such a multidimensional, chemical-genetic approach for discovering probes of pathways implicated in neuropsychiatric diseases.

Neurotrophin signaling through tropomyosin receptor kinases contributes to survival and proliferation of non-Hodgkin lymphoma

OBJECTIVE

Neurotrophin receptor signaling has been increasingly recognized as an important factor in the development and progression of a variety of malignancies. In order to analyze the potential contribution of neurotrophin signaling to lymphoma cell survival, we investigated the role of a neurotrophin axis in promoting survival and proliferation of non-Hodgkin lymphoma (NHL) cells.

MATERIALS AND METHODS

The role of neurotrophins in the survival and proliferation of NHL cells was determined by exposing cells to the Trk-specific inhibitor, K252a, and then performing (3)H-thymidine incorporation and Annexin-V/propidium iodide staining. The involvement of nuclear factor-kappaB (NF-kappaB) in this process was studied using Western blot, electrophoretic mobility shift assay, and immunofluorescence assays.

RESULTS

Here we demonstrate that both primary NHL cells and diffuse large B-cell lymphoma cell lines express Trk receptors and their neurotrophin ligands. Furthermore, these cells are sensitive to the Trk-specific inhibitor, K252a, as evidenced by the inhibition of proliferation and/or induction of apoptosis. Analysis of the mechanism into the effects of K252a revealed that, in the OCI-LY3 cell line, K252a induced a subnuclear distribution of NF-kappaB resulting in the sequestration of RelA in the nucleolus, thereby inhibiting NF-kappaB-dependent gene transcription. This results in the loss of interleukin-6 production; a known survival-promoting signal for OCI-LY3, as well as many primary diffuse large B-cell lymphomas.

CONCLUSION

Thus, Trk receptors represent a novel therapeutic target for the treatment of NHL.

Tyrosine kinase B receptor and BDNF expression in ovarian cancers - Effect on cell migration, angiogenesis and clinical outcome

In this report, we demonstrated that overexpression of tropomyosin-related kinase B (TrkB) was associated with shorter survival in ovarian cancer patients. Brain-derived neurotrophic factor (BDNF), the TrkB ligand, induced activation (phosphorylation) of TrkB in a dose dependent manner. Besides demonstrating the effect of BDNF/TrkB pathway in enhancing cancer cell migration and invasion but inhibiting apoptosis, we also report for the first time that exogenous hepatocyte growth factor induced TrkB expression at both mRNA and protein levels as well as phosphorylation. Our findings suggest that BDNF/TrkB pathway is important in ovarian carcinogenesis and TrkB may be a potential therapeutic target for ovarian cancer.

TrkB is necessary for the normal development of the lung

Normal development of the lung requires coordinated activation of cascades of signaling pathways initiated by growth factors signaling through their receptors. TrkB and its ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-4, belong to the neurotrophin family of growth factors, which are expressed in a large variety of non-neuronal tissues including the lung. Aberrant neurotrophin signaling underlies the pathogenesis of several lung-related pathologies, including asthma and lung cancer, however, little is known about the role of neurotrophins in the embryonic development of the lung. To fill this gap in knowledge, we analyzed the pattern of TrkB expression in the murine lung and we observed that TrkB is expressed in alveolar macrophages, type II pneumocytes, neuroepithelial bodies and nerves. Analysis of the structure of lung from mice deficient in TrkB revealed that absence of TrkB signaling results in thinner bronchial epithelium and apparent larger air space, and, more importantly, lack of neuroepithelial bodies, an important reduction in the density of nerve fibres in the bronchial smooth muscle, submucous plexus in bronchioles, and pulmonary artery walls. These findings suggest TrkB is essential for the normal development of the lung and the nervous system in the lung.

Neuroprotection by NGF and BDNF against neurotoxin-exerted apoptotic death in neural stem cells are mediated through Trk receptors, activating PI3-kinase and MAPK pathways

Neural stem cells (NSC) undergo apoptotic cell death during development of nervous system and in adult. However, little is known about the biochemical regulation of neuroprotection by neurotrophin in these cells. In this report, we demonstrate that Staurosporine (STS) and Etoposide (ETS) induced apoptotic cell death of NSC by a mechanism requiring Caspase 3 activation, poly (ADP-ribose) polymerase and Lamin A/C cleavage. Although C17.2 cells revealed higher mRNA level of p75 neurotrophin receptor (p75(NTR)) compared with TrkA or TrkB receptor, neuroprotective effect of both nerve growth factor (NGF) and brain-derived growth factor (BDNF) mediated through the activation of tropomyosin receptor kinase (Trk) receptors. Moreover, both NGF and BDNF induced the activation of the phosphatidylinositide 3 kinase (PI3K)/Akt and the mitogen-activated protein kinase (MAPK) pathway. Inhibition of Trk receptor by K252a reduced PARP cleavage as well as cell viability, whereas inhibition of p75(NTR) did not affect the effect of neurotrophin on neurotoxic insults. Thus our studies indicate that the protective effect of NGF and BDNF in NSC against apoptotic stimuli is mediated by the PI3K/Akt and MAPK signaling pathway via Trk receptors.

Dieldrin promotes resistance to anoikis in breast cancer cells in vitro

Epidemiological evidence suggests that exposure to the pesticide dieldrin, is associated with increased risk of breast cancer and mortality. We hypothesize that dieldrin promotes breast cancer by increasing survival of breast cancer cells. The aims of this study were to measure the effect of dieldrin on survival of breast cancer cells and the expression of tyrosine kinase B (TrkB), a suppressor of anoikis (apoptosis triggered by inappropriate anchorage). The human breast cancer cell line MDA-MB-231 was treated with dieldrin and proliferation, viability and resistance to anoikis were measured. TrkB expression was measured by Western blot in lysates and by immunohistochemistry in human tissue specimens. Dieldrin increased resistance to anoikis and TrkB expression. TrkB was expressed in a subset of high-grade breast carcinoma specimens. Our results demonstrate that dieldrin increases resistance to anoikis and expression of TrkB and show for the first time TrkB protein expression in human breast cancer.