Overexpression of Tropomysin-Related Kinase B in Metastatic Human Pancreatic Cancer Cells

Comparison between Substance P and Calcitonin Gene-Related Peptide and Their Receptors in Colorectal Adenocarcinoma

Background: Colorectal cancer is a major health problem that still causes many deaths worldwide. Neuropeptides, such as substance P and calcitonin gene-related peptide, play the neurotransmitter and neurohormone roles that increase tumor invasiveness and metastasis potential. This study aimed to see whether these neuropeptides and their receptors-neurokinin 1 receptor and calcitonin receptor-like receptor-correlate with the diagnosis stage, tumor differentiation grade, and different patient characteristics in colorectal cancer and also to compare them. Methods: We performed serum analyses of substance P and CGRP levels in patients with colorectal cancer and also the immunohistochemical analysis of their receptors in colorectal tumors and then correlated them with the disease stage and with different tumor characteristics. Results: We demonstrated that both substance P and calcitonin gene-related peptide had increased levels in colorectal cancer and that their levels correlated with the stage of the disease and with the tumor differentiation grade. We also demonstrated the correlation of NK-1R and CRLR higher immunohistochemical scores with advanced and poorly differentiated tumors. Conclusions: This study demonstrates that the neuropeptides SP and CGRP and their receptors NK-1R and CRLR could play a role in the pathogenesis of colorectal cancer, and they could be used as diagnostic and prognostic markers and could represent potential therapeutic targets.

Schwann cells in pancreatic cancer: Unraveling their multifaceted roles in tumorigenesis and neural interactions

Pancreatic ductal adenocarcinoma (PDAC), characterized by heightened neural density, presents a challenging prognosis primarily due to perineural invasion. Recognized for their crucial roles in neural support and myelination, Schwann cells (SCs) significantly influence the process of tumorigenesis. This review succinctly outlines the interplay between PDAC and neural systems, positioning SCs as a nexus in the tumor-neural interface. Subsequently, it delves into the cellular origin and influencers of SCs within the pancreatic tumor microenvironment, emphasizing their multifaceted roles in tumor initiation, progression, and modulation of the neural and immune microenvironment. The discussion encompasses potential therapeutic interventions targeting SCs. Lastly, the review underscores pressing issues, advocating for sustained exploration into the diverse contributions of SCs within the intricate landscape of PDAC, with the aim of enhancing our understanding of their involvement in this complex malignancy.

Novel CAR-T cells targeting TRKB for the treatment of solid cancer

Chimeric antigen receptor (CAR) T-cell therapy is highly effective for treating blood cancers such as B-cell malignancies, however, its effectiveness as an approach to treat solid tumors remains to be further explored. Here, we focused on the development of CAR-T cell therapies targeting tropomyosin-related kinase receptor B (TRKB), a highly expressed protein that is significantly associated with tumor progression, malignancy, and drug resistance in multiple forms of aggressive solid tumors. To achieve this, we screened brain-derived neurotrophic factor (BDNF) and neurotrophin 4 (NTF4) ligand-based CAR-T cells for their efficiency in targeting the TRKB receptor in the context of solid tumors, particularly hepatocellular carcinoma and pancreatic cancer. We demonstrated that TRKB is overexpressed not only in hepatocellular carcinoma and pancreatic carcinoma cell lines but also in cancer stem-like cells (CSCs). Notably, BDNF-CAR T and NTF4-CAR T cells could not only effectively target and kill TRKB-expressing pan-cancer cell lines in a dose-dependent manner but also effectively kill CSCs. We also performed in vivo studies to show that NTF4-CAR T cells have a better potential to inhibit the tumor growth of hepatocellular carcinoma xenografts in mice, compared with BDNF-CAR T cells. Taken together, our findings suggest that CAR-T targeting TRKB may be a promising approach for developing novel therapies to treat solid cancers.

Tumor microenvironment crosstalk between tumors and the nervous system in pancreatic cancer: Molecular mechanisms and clinical perspectives

Pancreatic ductal adenocarcinoma (PDAC) exhibits the highest incidence of perineural invasion among all solid tumors. The intricate interplay between tumors and the nervous system plays an important role in PDAC tumorigenesis, progression, recurrence, and metastasis. Various clinical symptoms of PDAC, including anorexia and cancer pain, have been linked to aberrant neural activity, while the presence of perineural invasion is a significant prognostic indicator. The use of conventional neuroactive drugs and neurosurgical interventions for PDAC patients is on the rise. An in-depth exploration of tumor-nervous system crosstalk has revealed novel therapeutic strategies for mitigating PDAC progression and effectively relieving symptoms. In this comprehensive review, we elucidate the regulatory functions of tumor-nervous system crosstalk, provide a succinct overview of the relationship between tumor-nervous system dialogue and clinical symptomatology, and deliberate the current research progress and forthcoming avenues of neural therapy for PDAC.

Research Progress of Neural Invasion in Pancreatic Cancer

Pancreatic cancer is one of the highly malignant gastrointestinal tumors in humans, and patients suffer from cancer pain in the process of cancer. Most patients suffer from severe pain in the later stages of the disease. The latest studies have shown that the main cause of pain in patients with pancreatic cancer is neuroinflammation caused by tumor cells invading nerves and triggering neuropathic pain on this basis, which is believed to be the result of nerve invasion. Peripheral nerve invasion (PNI), defined as the presence of cancer cells along the nerve or in the epineurial, perineural, and endoneurial spaces of the nerve sheath, is a special way for cancer to spread to distant sites. However, due to limited clinical materials, the research on the mechanism of pancreatic cancer nerve invasion has not been carried out in depth. In addition, perineural invasion is considered to be one of the underlying causes of recurrence and metastasis after pancreatectomy and an independent predictor of prognosis. This article systematically reviewed the neural invasion of pancreatic cancer through bioinformatics analysis, clinical manifestations and literature reviews.

Brain-derived neurotrophic factor: Its role in energy balance and cancer cachexia

Brain-derived neurotrophic factor (BDNF) plays an important role in the development of the central and peripheral nervous system during embryogenesis. In the mature central nervous system, BDNF is required for the maintenance and enhancement of synaptic transmissions and the survival of neurons. Particularly, it is involved in the modulation of neurocircuits that control energy balance through food intake, energy expenditure, and locomotion. Regulation of BDNF in the central nervous system is complex and environmental factors affect its expression in murine models which may reflect to phenotype dramatically. Furthermore, BDNF and its high-affinity receptor tropomyosin receptor kinase B (TrkB), as well as pan-neurotrophin receptor (p75NTR) is expressed in peripheral tissues in adulthood and their signaling is associated with regulation of energy balance. BDNF/TrkB signaling is exploited by cancer cells as well and BDNF expression is increased in tumors. Intriguingly, previously demonstrated roles of BDNF in regulation of food intake, adipose tissue and muscle overlap with derangements observed in cancer cachexia. However, data about the involvement of BDNF in cachectic cancer patients and murine models are scarce and inconclusive. In the future, knock-in and/or knock-out experiments with murine cancer models could be helpful to explore potential new roles for BDNF in the development of cancer cachexia.

Compounds originating from the edible mushroom Auricularia auricula-judae inhibit tropomyosin receptor kinase B activity

Tropomyosin receptor kinase B (TrkB) serves as a pivotal factor in various cancers. To identify novel natural compounds with TrkB-inhibiting properties, a screening approach was applied using extracts from a collection of wild and cultivated mushroom fruiting bodies, and Ba/F3 cells that ectopically express TrkB (TPR-TrkB). We selected mushroom extracts that selectively inhibited proliferation of the TPR-TrkB cells. We then evaluated the ability of exogenous interleukin 3 to rescue growth inhibition by the selected TrkB-positive extracts. An ethyl acetate extract of Auricularia auricula-judae actively inhibited auto-phosphorylation of TrkB. LC-MS/MS analysis of this extract revealed substances that might be responsible for the observed activity. This screening approach demonstrates, for the first time, that extracts originating from the mushroom A. auricula-judae exhibit TrkB-inhibition properties that might hold therapeutic potential for TrkB-positive cancers.

Oncogenic role of a developmentally regulated NTRK2 splice variant

Temporally regulated alternative splicing choices are vital for proper development, yet the wrong splice choice may be detrimental. Here, we highlight a previously unidentified role for the neurotrophin receptor splice variant TrkB.T1 in neurodevelopment, embryogenesis, transformation, and oncogenesis across multiple tumor types in humans and mice. TrkB.T1 is the predominant NTRK2 isoform across embryonic organogenesis, and forced overexpression of this embryonic pattern causes multiple solid and nonsolid tumors in mice in the context of tumor suppressor loss. TrkB.T1 also emerges as the predominant NTRK isoform expressed in a wide range of adult and pediatric tumors, including those harboring tropomyosin receptor kinase fusions. Affinity purification-mass spectrometry proteomic analysis reveals distinct interactors with known developmental and oncogenic signaling pathways such as Wnt, transforming growth factor-β, Sonic Hedgehog, and Ras. From alterations in splicing factors to changes in gene expression, the discovery of isoform specific oncogenes with embryonic ancestry has the potential to shape the way we think about developmental systems and oncology.

The Role of Neural Signaling in the Pancreatic Cancer Microenvironment

Simple Summary

Pancreatic cancer is a highly lethal malignant disease with a dense stroma, called the tumor microenvironment. Accumulating evidence indicates the important role of sympathetic, parasympathetic, and sensory nerves in the tumor microenvironment of various cancers, including pancreatic cancer. Cancer cells and neural cells interact with each other to form a complex network and cooperatively promote cancer growth and invasion. In this review article, we describe the current understanding of the role of nerves in the tumor microenvironment.

Abstract

Pancreatic cancer is one of the most lethal malignant diseases. Various cells in the tumor microenvironment interact with tumor cells and orchestrate to support tumor progression. Several kinds of nerves are found in the tumor microenvironment, and each plays an essential role in tumor biology. Recent studies have shown that sympathetic, parasympathetic, and sensory neurons are found in the pancreatic cancer microenvironment. Neural signaling not only targets neural cells, but tumor cells and immune cells via neural receptors expressed on these cells, through which tumor growth, inflammation, and anti-tumor immunity are affected. Thus, these broad-range effects of neural signaling in the pancreatic cancer microenvironment may represent novel therapeutic targets. The modulation of neural signaling may be a therapeutic strategy targeting the whole tumor microenvironment. In this review, we describe the current understanding of the role of nerves in the tumor microenvironment of various cancers, with an emphasis on pancreatic cancer. We also discuss the underlying mechanisms and the possibility of therapeutic applications.

Emerging Roles of the Nervous System in Gastrointestinal Cancer Development

Simple Summary

Nerve–cancer cross-talk has increasingly become a focus of the oncology field, particularly in gastrointestinal (GI) cancers. The indispensable roles of the nervous system in GI tumorigenesis and malignancy have been dissected by epidemiological, experimental animal and mechanistic data. Herein, we review and integrate recent discoveries linking the nervous system to GI cancer initiation and progression, and focus on the molecular mechanisms by which nerves and neural receptor pathways drive GI malignancy.

Abstract

Our understanding of the fascinating connection between nervous system and gastrointestinal (GI) tumorigenesis has expanded greatly in recent years. Recent studies revealed that neurogenesis plays an active part in GI tumor initiation and progression. Tumor-driven neurogenesis, as well as neurite outgrowth of the pre-existing peripheral nervous system (PNS), may fuel GI tumor progression via facilitating cancer cell proliferation, chemoresistance, invasion and immune escape. Neurotransmitters and neuropeptides drive the activation of various oncogenic pathways downstream of neural receptors within cancer cells, underscoring the importance of neural signaling pathways in GI tumor malignancy. In addition, neural infiltration also plays an integral role in tumor microenvironments, and contributes to an environment in favor of tumor angiogenesis, immune evasion and invasion. Blockade of tumor innervation via denervation or pharmacological agents may serve as a promising therapeutic strategy against GI tumors. In this review, we summarize recent findings linking the nervous system to GI tumor progression, set the spotlight on the molecular mechanisms by which neural signaling fuels cancer aggressiveness, and highlight the importance of targeting neural mechanisms in GI tumor therapy.

Nerves and Pancreatic Cancer: New Insights into a Dangerous Relationship

Perineural invasion (PNI) is defined as the presence of neoplastic cells along nerves and/or within the different layers of nervous fibers: epineural, perineural and endoneural spaces. In pancreatic cancer-particularly in pancreatic ductal adenocarcinoma (PDAC)-PNI has a prevalence between 70 and 100%, surpassing any other solid tumor. PNI has been detected in the early stages of pancreatic cancer and has been associated with pain, increased tumor recurrence and diminished overall survival. Such an early, invasive and recurrent phenomenon is probably crucial for tumor growth and metastasis. PNI is a still not a uniformly characterized event; usually it is described only dichotomously ("present" or "absent"). Recently, a more detailed scoring system for PNI has been proposed, though not specific for pancreatic cancer. Previous studies have implicated several molecules and pathways in PNI, among which are secreted neurotrophins, chemokines and inflammatory cells. However, the mechanisms underlying PNI are poorly understood and several aspects are actively being investigated. In this review, we will discuss the main molecules and signaling pathways implicated in PNI and their roles in the PDAC.

Preclinical pharmacodynamic evaluation of a new Src/FOSL1 inhibitor, LY-1816, in pancreatic ductal adenocarcinoma

Despite tremendous efforts, the clinical prognosis of pancreatic ductal adenocarcinoma (PDAC) remains disappointing. There is an urgent need to develop more effective treatment strategies to improve the prognosis of patients with PDAC. In this study, we evaluate the anti‐PDAC effects of LY‐1816, a new multikinase inhibitor developed by us. In in vitro assays, LY‐1816 showed significant inhibitory effects on the proliferation, migration, and invasion of human PDAC cells, and induced PDAC cell apoptosis. Western blot analysis revealed that LY‐1816 markedly suppressed the Src signaling, and downregulated the expression of FOSL1; FOSL1 is an oncogene vulnerability in KRAS‐driven pancreatic cancer. In in vivo models of PDAC xenografts (Aspc‐1 and Bxpc‐3), LY‐1816 showed more potent antitumor activity than dasatinib and gemcitabine. Moreover, mice treated with LY‐1816 showed a much more significant survival advantage in a metastatic model of PDAC compared with those treated with vehicle, dasatinib, or gemcitabine. These results provide effective support for the subsequent clinical evaluation of LY‐1816 in the treatment of PDAC.

Neurotrophins and their involvement in digestive cancers

Cancers of the digestive system, including esophageal, gastric, pancreatic, hepatic, and colorectal cancers, have a high incidence and mortality worldwide. Efficient therapies have improved patient care; however, many challenges remain including late diagnosis, disease recurrence, and resistance to therapies. Mechanisms responsible for these aforementioned challenges are numerous. This review focuses on neurotrophins, including NGF, BDNF, and NT3, and their specific tyrosine kinase receptors called tropomyosin receptor kinase (Trk A, B, C, respectively), associated with sortilin and the p75 neurotrophin receptor (p75NTR), and their implication in digestive cancers. Globally, p75NTR is a frequently downregulated tumor suppressor. On the contrary, Trk and their ligands are considered oncogenic factors. New therapies which target NT and/or their receptors, or use them as diagnosis biomarkers could help us to combat digestive cancers.

Insights into Current Tropomyosin Receptor Kinase (TRK) Inhibitors: Development and Clinical Application

The use of kinase-directed precision medicine has been heavily pursued since the discovery and development of imatinib. Annually, it is estimated that around ∼20 000 new cases of tropomyosin receptor kinase (TRK) cancers are diagnosed, with the majority of cases exhibiting a TRK genomic rearrangement. In this Perspective, we discuss current development and clinical applications for TRK precision medicine by providing the following: (1) the biological background and significance of the TRK kinase family, (2) a compilation of known TRK inhibitors and analysis of their cocrystal structures, (3) an overview of TRK clinical trials, and (4) future perspectives for drug discovery and development of TRK inhibitors.

Tropomyosin-related kinase B mediated signaling contributes to the induction of malignant phenotype of gallbladder cancer

This study aims to demonstrate the clinical and biological significance of Brain derived neurotrophic factor (BDNF)/Tropomyosin-related kinase B (TrkB) signaling in gallbladder cancer (GBC) through a series of in vitro and in vivo experiments. TrkB expression was detected in 63 (91.3%) out of 69 surgically resected primary GBC specimens by immunohistochemistry. TrkB expression in the invasive front correlated with T factor (p=0.0391) and clinical staging (p=0.0391). Overall survival was lower in patients with high TrkB expression in the invasive front than in those with low TrkB expression (p=0.0363). In vitro experiment, we used five TrkB-expressing GBC cell lines with or without K-ras mutation. TrkB-mediated signaling increased proliferation and the invasiveness by inducing epithelial mesenchymal transition, and activating matrix metalloproteinases-2 (MMP-2) and MMP-9. Inhibition of TrkB-mediated signaling also decreased hypoxia-inducible factor-1α, vascular endothelial growth factor A (VEGF-A), VEGF-C, and VEGF-D expression. In vivo experiment, inhibition of TrkB-mediated signaling suppressed tumorigenicity and tumor growth in GBC. These findings demonstrate that TrkB-mediated signaling contributes to the induction of malignant phenotypes (proliferation, invasiveness, angiogenesis, lymphangiogenesis, and tumorigenesis) in GBC, and could be a promising therapeutic target regardless of K-ras mutation status.

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.

Targeting Novel but Less Common Driver Mutations and Chromosomal Translocations in Advanced Non-Small Cell Lung Cancer

Discovery of the epidermal growth factor receptor gene mutation and the anaplastic lymphoma kinase chromosomal translocation in non-small cell lung cancer has prompted efforts around the world to identify many less common targetable oncogenic drivers. Such concerted efforts have been variably successful in both non-squamous and squamous cell carcinomas of the lung. Some of the targeted therapies for these oncogenic drivers have received regulatory approval for clinical use, while others have modest clinical benefit. In this mini-review, several of these targets will be reviewed.

Uncovering the role of brain-derived neurotrophic factor/tyrosine kinase receptor B signaling in head and neck malignancies

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors that was first known as responsible for sustain the growth, function, and plasticity of neural cells. BDNF exerts its effects by binding to the tyrosine kinase receptor B (TrkB). The BDNF/TrkB axis has been reported to be overexpressed in several neurogenic and non-neurogenic tumors. Its higher expression was associated with a poor prognosis to patients affected by different human malignancies, tumor growth, invasion, and metastasis; epithelial-mesenchymal transition and resistance to chemotherapy. BDNF/TrkB represent promising targets to the development of novel anticancer therapies. Some clinical trials are currently evaluating the efficacy of Trk protein-target drugs in different types of solid tumors. To date, few groups have evaluated the DNF/TrkB pathway in head and neck malignancies. The aims of this study were to review the literature concerning the role of BDNF/TrkB activation in head and neck squamous cell carcinoma and malignant salivary gland tumors and to discuss future perspectives of BDNF/TrkB-target therapy.

Dual inhibition of BDNF/TrkB and autophagy: a promising therapeutic approach for colorectal cancer

Colorectal cancer (CRC) is the most common digestive cancer in the Western world. Despite effective therapies, resistance and/or recurrence frequently occur. The present study investigated the impact of two survival pathways—neurotrophic factors (TrkB/BDNF) and autophagy—on cell fate and tumour evolution. In vitro studies were performed on two CRC cell lines, SW480 (primary tumour) and SW620 (lymph node invasion), which were also used for subcutaneous xenografts on a nude mouse model. In addition, the presence of neurotrophic factors (NTs) and autophagy markers were assessed in tissue samples representative of different stages. On the basis of our previous study (which demonstrated that TrkB overexpression is associated with prosurvival signaling in CRC cells), we pharmacologically inhibited NTs pathways with K252a. As expected, an inactivation of the PI3K/AKT pathway was observed and CRC cells initiated autophagy. Conversely, blocking the autophagic flux with chloroquine or with ATG5‐siRNA overactivated TrkB/BDNF signaling. In vitro, dual inhibition improved the effectiveness of single treatment by significantly reducing metabolic activity and enhancing apoptotic cell death. These findings were accentuated in vivo, in which dual inhibition induced a spectacular reduction in tumour volume following long‐term treatment (21 days for K252a and 12 days for CQ). Finally, significant amounts of phospho‐TrkB and LC3II were found in the patients’ tissues, highlighting their relevance in CRC tumour biology. Taken together, our results show that targeting NTs and autophagy pathways potentially constitutes a new therapeutic approach for CRC.

Amigo2-upregulation in Tumour Cells Facilitates Their Attachment to Liver Endothelial Cells Resulting in Liver Metastases

Since liver metastasis is the main cause of death in cancer patients, we attempted to identify the driver gene involved. QRsP-11 fibrosarcoma cells were injected into the spleens of syngeneic mice to isolate tumour sub-populations that colonize the liver. Cells from liver metastatic nodules were established and subsequently injected intrasplenically for selection. After 12 cycles, the cell subline LV12 was obtained. Intravenous injection of LV12 cells produced more liver metastases than QRsP-11 cells, whereas the incidence of lung metastases was similar to that of QRsP-11 cells. LV12 cells adhered to liver-derived but not to lung-derived endothelial cells. DNA chip analysis showed that amphoterin-induced gene and open reading frame 2 (Amigo2) was overexpressed in LV12 cells. siRNA-mediated knockdown of Amigo2 expression in LV12 cells attenuated liver endothelial cell adhesion. Ex vivo imaging showed that suppression of Amigo2 in luciferase-expressing LV12 cells reduced attachment/metastasis to liver to the same level as that observed with QRsP-11 cells. Forced expression of Amigo2 in QRsP-11 cells increased liver endothelial cell adhesion and liver metastasis. Additionally, Amigo2 expression in human cancers was higher in liver metastatic lesions than in primary lesions. Thus, Amigo2 regulated tumour cell adhesion to liver endothelial cells and formation of liver metastases.

Tropomyosin receptor kinase inhibitors: an updated patent review for 2010-2016 - Part I

INTRODUCTION

Tropomyosin receptor kinases (TrkA/B/C) play crucial roles in the development and maintenance of the nervous system, and aberrant expression of Trk has been implicated in neurological disorders as well as neural and non-neural neoplasms. Patent activity encompassing Trk inhibitors has grown substantially over the last 6 years, recognized by a rise in the number of pharmaceutical entrants to the field and the escalation of novel inhibitor chemotypes. Area covered: In Part I of this two part review, a biological and structural overview of Trk is provided in the context of Trk as a therapeutic target for cancer and pain, followed by the report of recent patent literature claiming small molecule inhibitors of Trk family kinases or which describe inhibitors developed for other kinase targets but include noteworthy Trk inhibition/application. The discussion of the patent literature continues in Part II of this review, which includes an in-depth view of the current clinical applications of Trk inhibitors. Expert opinion: Substantial synthetic efforts in Trk inhibitor development has propagated numerous and diverse inhibitor chemotypes, including TrkA-specific inhibitors. While many novel Trk inhibitors remain the original progeny of Trk-specific development programs, kinase inhibitors initially developed for other kinases have also been successfully repositioned for Trk.

The significance of Trk receptors in pancreatic cancer

This study investigated the Trk receptor family as a therapeutic target in pancreatic ductal adenocarcinoma and assessed their prognostic significance. Global gene expression analysis was investigated in prospectively collected pancreatic ductal adenocarcinomas that had either undergone neoadjuvant chemoradiation or were treated by surgery. PANC-1 and MIA-PaCa-2 cell lines were investigated to establish whether fractionated radiation altered expression of four neuroendocrine genes and whether this resulted in subsequent changes in radiosensitivity. A specific inhibitor of TrkA, B, and C, AstraZeneca 1332, was investigated in vitro and in vivo in combination with radiation. A tissue microarray was constructed from 77 pancreatic ductal adenocarcinoma patients who had undergone neoadjuvant chemoradiation and the Trk receptor, and neurogenic differentiation 1 expression was assessed and correlated with overall survival. A total of 99 genes were identified that were differentially expressed in the chemoradiation patients with neuroendocrine genes and pathways, in particular the neurogenic differentiation 1 and Trk receptor family, being prominent. Fractionated radiation upregulated the expression of neuroendocrine genes, and AstraZeneca 1332 treatment in vitro enhanced radiosensitivity. No added effect of AstraZeneca 1332 was observed in vivo. Trk receptor expression varied between isoforms but did not correlate significantly with clinical outcome. Radiation treatment upregulated neuroendocrine gene expression but the Trk receptor family does not appear to be a promising treatment target.

Synthesis, anticancer, and docking studies of salicyl-hydrazone analogues: A novel series of small potent tropomyosin receptor kinase A inhibitors

A series of novel salicyl-hydrazone analogues were synthesized and evaluated for their in vitro cytotoxic activities in five human cancer cell lines, namely, lung cancer (A549), ovarian cancer (SK-OV-3), skin cancer (SK-MEL-2), colon cancer (HCT15) and pancreatic cancer (MIA-PaCa-2) cells, and for their in vitro tropomyosin receptor kinase A (TrkA) inhibitory activities. Each of the compounds showed significant cytotoxicity against all cancer cells. Compound 3i was found to be most potent against all cancer cell lines with IC₅₀ values of 2.46 (A549), 0.87 (SK-OV-3), 1.43 (SK-MEL-2), 0.89 (HCT15), and 0.48μM (MIA-PaCa-2), followed by compound 3l. Cytotoxicity of 3i was similar to that of doxorubicin (0.87μM) against HCT15 cells. Compounds 3i and 3l also showed highest TrkA inhibitory activities with IC₅₀ values of 0.231 and 0.380μM, respectively. A SAR study of the series revealed that compounds with hydroxyl groups showed better cytotoxicity and TrkA inhibitory potency (in the following order 2,4-OH>2,3,4-OH>3,4-OH>4-OH) than compounds possessing electron donating or withdrawing groups on the benzylidenephenyl ring. Docking studies of compounds 3i and 3l conducted on the crystal structure of TrkA receptor (a promising target for anticancer agents) showed both had a high docking score and similar order of experimental TrkA inhibitory activities. The formation of several hydrogen bonds involving N and O containing moieties contributed most significantly to ligand binding and stabilization at the active site of the receptor. In addition, ligand-receptor complexes were further stabilized by π-cation, π-anion, amide-π stacked, and van der Waal's interactions. Conformational analyses showed ligand molecules adopted similar conformations at the receptor active site during interactions, but that the low energy optimized conformations of compounds 3i and 3l differed.

Expression and clinical significance of TrkB in sinonasal squamous cell carcinoma: a pilot study

Previous studies have confirmed that tropomyosin-related kinase B (TrkB) plays a critical role in the occurrence, development, and metastasis of many kinds of malignant tumour. More recently, TrkB was found to be overexpressed in head and neck squamous cell carcinoma (SCC) and to be involved in multistep tumour progression. In this study, the expression of TrkB was investigated in 27 cases of sinonasal SCC using an immunohistochemical method. The clinical significance and possible role of TrkB as a prognostic marker in these tumours was also explored. The results showed that TrkB was overexpressed in all cases of sinonasal SCC. A high level of expression of TrkB was significantly related with poor-to-moderate differentiation of SCC (P=0.026), high clinical stage (P=0.023), and the presence of local recurrence (P=0.004). Analysis by Kaplan-Meier method indicated that patients with high levels of TrkB expression had shorter overall survival (P=0.006) and disease-free survival (P=0.018). Multivariate analysis revealed that the level of TrkB expression was an independent prognostic factor for both overall and disease-free survival (P=0.019 and P=0.048, respectively). These data suggest that the overexpression of TrkB may play a significant role in sinonasal SCC and that TrkB may be used as a potential prognostic marker for the clinical outcome.

Neurogenin 3 is regulated by neurotrophic tyrosine kinase receptor type 2 (TRKB) signaling in the adult human exocrine pancreas

BACKGROUND

Reports of exocrine-to-endocrine reprogramming through expression or stabilization of the transcription factor neurogenin 3 (NGN3) have generated renewed interest in harnessing pancreatic plasticity for therapeutic applications. NGN3 is expressed by a population of endocrine progenitor cells that give rise exclusively to hormone-secreting cells within pancreatic islets and is necessary and sufficient for endocrine differentiation during development. In the adult human pancreas, NGN3 is expressed by dedifferentiating exocrine cells with a phenotype resembling endocrine progenitor cells and the capacity for endocrine differentiation in vitro. Neurotrophic tyrosine kinase receptor type 2 (TRKB), which regulates neuronal cell survival, differentiation and plasticity, was identified as highly overexpressed in the NGN3 positive cell transcriptome compared to NGN3 negative exocrine cells. This study was designed to determine if NGN3 is regulated by TRKB signaling in the adult human exocrine pancreas.

METHODS

Transcriptome analysis, quantitative reverse transcriptase polymerase chain reaction (RTPCR) and immunochemistry were used to identify TRKB isoform expression in primary cultures of human islet-depleted exocrine tissue and human cadaveric pancreas biopsies. The effects of pharmacological modulation of TRKB signaling on the expression of NGN3 were assessed by Student's t-test and ANOVA.

RESULTS

Approximately 30 % of cultured exocrine cells and 95 % of NGN3+ cells express TRKB on their cell surface. Transcriptome-based exon splicing analyses, isoform-specific quantitative RTPCR and immunochemical staining demonstrate that TRKB-T1, which lacks a tyrosine kinase domain, is the predominant isoform expressed in cultured exocrine tissue and is expressed in histologically normal cadaveric pancreas biopsies. Pharmacological inhibition of TRKB significantly decreased the percentage of NGN3+ cells, while a TRKB agonist significantly increased this percentage. Inhibition of protein kinase B (AKT) blocked the effect of the TRKB agonist, while inhibition of tyrosine kinase had no effect. Modulation of TRKB and AKT signaling did not significantly affect the level of NGN3 mRNA.

CONCLUSIONS

In the adult human exocrine pancreas, TRKB-T1 positively regulates NGN3 independent of effects on NGN3 transcription. Targeting mechanisms controlling the NGN3+ cell population size and endocrine cell fate commitment represent a potential new approach to understand pancreas pathobiology and means whereby cell populations could be expanded for therapeutic purposes.

Overexpression of Tyrosine Kinase Receptor B Promotes Metastasis of Ovarian Serous Adenocarcinoma by Lymphangiogenesis

Aims and Background

The aim of this study was to detect the expression features of tyrosine kinase receptor B (TrkB) and analyze the possible correlation between TrkB expression and lymph vessel density (LVD) in metastasis of ovarian serous adenocarcinoma.

Methods

An immunohistochemical method was used to evaluate TrkB expression in 139 ovarian tumor sections (103 primary ovarian serous adenocarcinomas and 36 serous adenomas) and investigate the correlation between TrkB expression and LVD, which was estimated by means of VEGFR-3 assessment.

Results

TrkB was significantly upregulated in serous adenocarcinomas and absent in serous adenomas. There was no association between TrkB expression and the histological grade of cancer cells. The expression of TrkB was correlated with surgico-pathological stage and metastasis in serous adenocarcinomas. The level of TrkB was higher in advanced-stage than in early-stage disease. TrkB was overexpressed in metastatic lesions compared with the corresponding primary lesions. Furthermore, a positive correlation between TrkB expression and LVD in serous adenocarcinomas was observed.

Conclusions

TrkB was overexpressed in ovarian serous adenocarcinomas and might be involved in cancer metastasis by associated lymphangiogenesis.

DNA methylation-dependent regulation of TrkA, TrkB, and TrkC genes in human hepatocellular carcinoma

The tropomyosin-related kinase (Trk) family of neurotrophin receptors, TrkA, TrkB and TrkC, has been implicated in the growth and survival of human cancers. Here we report that Trks are frequently overexpressed in hepatocellular carcinoma (HCC) from patients and human liver cancer cell lines. To unravel the underlying molecular mechanism(s) for this phenomenon, DNA methylation patterns of CpG islands in TrkA, TrkB, and TrkC genes were examined in normal and cancer cell lines derived from liver. A good correlation was observed between promoter hypermethylation and lower expression of TrkA, TrkB, and TrkC genes, which was supported by the data that inhibiting DNA methylation with 5-azacytidine restored expression of those genes in normal liver cell lines. Furthermore, Trks promoted the proliferation of HepG2 and induced expression of the metastatic regulator, Twist. These results suggest that Trks may contribute to growth and metastasis of liver cancer.