Rational basis for Trk inhibition therapy for prostate cancer

The nerve growth factor-delivered signals in prostate cancer and its associated microenvironment: when the dialogue replaces the monologue

Prostate cancer (PC) represents the most diagnosed and the second most lethal cancer in men worldwide. Its development and progression occur in concert with alterations in the surrounding tumor microenvironment (TME), made up of stromal cells and extracellular matrix (ECM) that dynamically interact with epithelial PC cells affecting their growth and invasiveness. PC cells, in turn, can functionally sculpt the TME through the secretion of various factors, including neurotrophins. Among them, the nerve growth factor (NGF) that is released by both epithelial PC cells and carcinoma-associated fibroblasts (CAFs) triggers the activation of various intracellular signaling cascades, thereby promoting the acquisition of a metastatic phenotype. After many years of investigation, it is indeed well established that aberrations and/or derangement of NGF signaling are involved not only in neurological disorders, but also in the pathogenesis of human proliferative diseases, including PC. Another key feature of cancer progression is the nerve outgrowth in TME and the concept of nerve dependence related to perineural invasion is currently emerging. NGF released by cancer cells can be a driver of tumor neurogenesis and nerves infiltrated in TME release neurotransmitters, which might stimulate the growth and sustainment of tumor cells.In this review, we aim to provide a snapshot of NGF action in the interactions between TME, nerves and PC cells. Understanding the molecular basis of this dialogue might expand the arsenal of therapeutic strategies against this widespread disease.

In Vitro Effects of Photon Beam and Carbon Ion Radiotherapy on the Perineural Invasion of Two Cell Lines of Neurotropic Tumours

Primary mucosal melanoma (PMM) and pancreatic ductal adenocarcinoma (PDAC) are two aggressive malignancies, characterized by intrinsic radio-chemoresistance and neurotropism, a histological feature resulting in frequent perineural invasion (PNI), supported by neurotrophic factors secreted in the tumour microenvironment (TME), such as neurotrophin-3 (NT-3). Carbon-ion radiotherapy (CIRT) could represent an effective option in unresectable PMM and PDAC. Only a few data about the effects of CIRT on PNI in relation to NT-3 are available in the literature, despite the numerous pieces of evidence revealing the peculiar effects of this type of radiation on tumour cell migration. This in vitro study investigated for the first time the response of PMM and PDAC cells to NT-3 and evaluated the effects of conventional photon beam radiotherapy (XRT) and CIRT on cell viability, proliferation, and migration. Our results demonstrated the greater capacity of C-ions to generally decrease cell viability, proliferation, and migration, while the addition of NT-3 after both types of irradiation determined an increase in these features, maintaining a dose-dependent trend and acting more effectively as a chemoattractant than inductor in the case of migration.

Downregulation of MMP1 functions in preventing perineural invasion of pancreatic cancer through blocking the NT-3/TrkC signaling pathway

BACKGROUND

Pancreatic cancer (PC) is a fatal malignancy that frequently involves perineural invasion (PNI). This study aims to investigate the function and underlying mechanisms of matrix metalloproteinase-1 (MMP1) in PNI of PC.

METHODS

Human pancreatic cancer PANC-1 cells were co-cultured with dorsal root ganglion in vitro. The expression of MMP1, epithelial-mesenchymal transition (EMT) markers, Schwann cell markers, neurotrophic factors, NT-3, and TrkC was measured by qRT-PCR or Western blot. Transwell assay was performed to evaluate cell migration and invasion. In vivo model of PNI was established via inoculating PANC-1 cells into mice. PANC-1 cells and mice were also treated with LM22B-10 (an activator of TrkC) to confirm the mechanisms involving NT-3/TrkC in PNI of PC both in vivo and in vitro.

RESULTS

The expression of MMP1 was significantly higher in PDAC tissues than non-cancerous tissues, which was positively associated with PNI. MMP1 knockdown repressed the migration and invasion of PANC-1 cells. Except for E-cadherin, the expression of EMT markers, Schwann cell markers, neurotrophic factors, NT-3, and TrkC was inhibited by MMP1 silencing. The same effects of MMP1 knockdown on the above factors were also observed in the PNI model. Moreover, MMP1 knockdown elevated the sciatic nerve function and reduced PNI in the model mice. LM22B-10 partially abolished the effects of MMP1 knockdown both in vivo and in vitro.

CONCLUSIONS

Silencing of MMP1 prevents PC cells from EMT and Schwann-like cell differentiation via inhibiting the activation of the NT-3/TrkC signaling pathway, thus alleviating the PNI of PC.

A Quantitative Bioassay to Determine the Inhibitory Potency of NGF-TrkA Antagonists

In this article, we demonstrate and validate a new bioassay named the NTAB [NGF-TrkA (nerve growth factor-tropomyosin receptor kinase A) antagonist bioassay] for the determination of the inhibitory potency of NGF-TrkA antagonists, based on the inhibition of NGF-dependent proliferation of the human TF1 erythroleukemic cell line.It is well known that NGF holds great therapeutic potential due to its neurotrophic and neuroprotective properties. NGF is also involved in some pathways, however, principally driven by TrkA that, if not correctly regulated, can lead to unwanted pathological outcomes linked to pain, angiogenesis, and cancer.Indeed, there is an increasing interest, from a therapeutic perspective, in designing new effective molecules (antibodies, antibody fragments, or small molecules) able to inhibit the undesired NGF-TrkA pathway. For these reasons, there is an interest to develop functional cell-based assays for determination of the inhibition potency of compounds inhibiting the NGF-TrkA axis. The NTAB presents significant advantages over other published NGF-TrkA functional bioassays, for these reasons: (1) It is quantitative, (2) it measures a pure TrkA response, (3) it is simpler, (4) it is based on a natural biological response, and (5) it is easily scalable from a lab scale to an automated industrial assay.The NTAB assay was validated with a panel of well-characterized NGF-TrkA inhibitors, yielding characteristic dose-response curves, from which the relative strength of the inhibitors was quantitatively determined and used for comparisons. This new bioassay will be very useful to assist in the validation and prioritization of the best inhibitors among a large number of candidates.

Identification of candidate miRNAs in early-onset and late-onset prostate cancer by network analysis

The incidence of patients under 55 years old diagnosed with Prostate Cancer (EO-PCa) has increased during recent years. The molecular biology of PCa cancer in this group of patients remains unclear. Here, we applied weighted gene coexpression network analysis of the expression of miRNAs from 24 EO-PCa patients (38–45 years) and 25 late-onset PCa patients (LO-PCa, 71–74 years) to identify key miRNAs in EO-PCa patients. In total, 69 differentially expressed miRNAs were identified. Specifically, 26 and 14 miRNAs were exclusively deregulated in young and elderly patients, respectively, and 29 miRNAs were shared. We identified 20 hub miRNAs for the network built for EO-PCa. Six of these hub miRNAs exhibited prognostic significance in relapse‐free or overall survival. Additionally, two of the hub miRNAs were coexpressed with mRNAs of genes previously identified as deregulated in EO-PCa and in the most aggressive forms of PCa in African-American patients compared with Caucasian patients. These genes are involved in activation of immune response pathways, increased rates of metastasis and poor prognosis in PCa patients. In conclusion, our analysis identified miRNAs that are potentially important in the molecular pathology of EO-PCa. These genes may serve as biomarkers in EO-PCa and as possible therapeutic targets.

Activation of BDNF/TrkB pathway promotes prostate cancer progression via induction of epithelial-mesenchymal transition and anoikis resistance

Prostate cancer (PCa) is one of the most common malignant diseases in male worldwide, yet, the molecular mechanisms involved in PCa progression are still poorly understood. This study aimed to investigate the roles of the brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) pathway in PCa progression. It was demonstrated by immunohistochemical analysis that both BDNF and TrkB were overexpressed in PCa tissues and elevated TrkB expression was tightly related with lymph node metastasis and advanced stage of PCa. In vitro studies showed that stimulation with rhBDNF or overexpression of TrkB in PCa cells promoted cell migration, invasion, and anoikis resistance. Overexpression of TrkB also resulted in epithelial-mesenchymal transition (EMT)-like transformation in cell morphology, whereas RNA interference-mediated TrkB depletion caused reversion of EMT. Further investigation demonstrated that protein kinase B (AKT) was responsible for BDNF/TrkB signaling-induced pro-migratory and pro-invasive effects, EMT, and anoikis resistance. Finally, in vivo studies confirmed that enhanced TrkB expression facilitated tumor growth, whereas downregulation of TrkB suppressed tumor growth. Our findings illustrate that BDNF/TrkB pathway is crucial for PCa progression, which may provide a novel therapeutic strategy for the treatment of advanced PCa.

Nerves in cancer

The contribution of nerves to the pathogenesis of malignancies has emerged as an important component of the tumour microenvironment. Recent studies have shown that peripheral nerves (sympathetic, parasympathetic and sensory) interact with tumour and stromal cells to promote the initiation and progression of a variety of solid and haematological malignancies. Furthermore, new evidence suggests that cancers may reactivate nerve-dependent developmental and regenerative processes to promote their growth and survival. Here we review emerging concepts and discuss the therapeutic implications of manipulating nerves and neural signalling for the prevention and treatment of cancer.

Tumour innervation and neurosignalling in prostate cancer

Prostate cancer progression has been shown to be dependent on the development of autonomic nerves into the tumour microenvironment. Sympathetic nerves activate adrenergic neurosignalling that is necessary in early stages of tumour progression and for initiating an angiogenic switch, whereas parasympathetic nerves activate cholinergic neurosignalling resulting in tumour dissemination and metastasis. The innervation of prostate cancer seems to be initiated by neurotrophic growth factors, such as the precursor to nerve growth factor secreted by tumour cells, and the contribution of brain-derived neural progenitor cells has also been reported. Current experimental, epidemiological and clinical evidence shows the stimulatory effect of tumour innervation and neurosignalling in prostate cancer. Using nerves and neurosignalling could have value in the management of prostate cancer by predicting aggressive disease, treating localized disease through denervation and relieving cancer-associated pain in bone metastases.

NT-3/TrkC Axis Contributes to the Perineural Invasion and the Poor Prognosis in Human Salivary Adenoid Cystic Carcinoma

The present study was aimed to investigate the role and mechanism of neurotrophin-3 (NT-3) and its specific receptor tropomyosin receptor kinase C (TrkC) in the perineural invasion (PNI) process of the salivary adenoid cystic carcinoma (SACC). The co-cultured system between SACC cells and Schwann cells (SCs) was employed to detect the expression of NT-3 and TrkC. The results of ELISA, qRT-PCR and western blot showed that NT-3 was noticeably elevated in the co-cultured SACC-83 cells, while TrkC was increased in the co-cultured SCs. The results of scratch wound healing, migration, and 3D co-culture assays showed that the directional migration abilities of the co-cultured SACC-83 cells and SCs were significantly increased. Under the stimulation of NT-3, the directional motor ability of SACC-83 cells and SCs was significantly improved, and the apoptosis of SACC-83 cells and SCs were obviously inhibited. In addition, blocking TrkC by its specific inhibitor AZD7451 could significantly inhibit these effects. Immunohistochemistry staining showed that the positive expression of NT-3 (88.5%) and TrkC (92.3%) was significantly correlated with the PNI in SACC specimens (P < 0.05). Additionally, the high expression of NT-3 was significantly associated with the poor prognosis of SACC patients (P < 0.05). The present study indicated that NT-3/TrkC axis contributed to the PNI progression and the poor prognosis of SACC via regulating the interaction between SACC cells and SCs. Interruption of the interaction between SACC cells and SCs by blocking the NT-3/TrkC axis might be an effective strategy for anti-PNI therapy in SACC.

Nerve Growth Factor Induces Proliferation and Aggressiveness In Prostate Cancer Cells

Resistance to hormone therapy and disease progression is the major challenge in clinical management of prostate cancer (PC). Drugs currently used in PC therapy initially show a potent antitumor effects, but PC gradually develops resistance, relapses and spreads. Most patients who fail primary therapy and have recurrences eventually develop castration-resistant prostate cancer (CRPC), which is almost incurable. The nerve growth factor (NGF) acts on a variety of non-neuronal cells by activating the NGF tyrosine-kinase receptor, tropomyosin receptor kinase A (TrkA). NGF signaling is deregulated in PC. In androgen-dependent PC cells, TrkA mediates the proliferative action of NGF through its crosstalk with the androgen receptor (AR). Epithelial PC cells, however, acquire the ability to express NGF and TrkA, as the disease progresses, indicating a role for NGF/TrkA axis in PC progression and androgen-resistance. We here report that once activated by NGF, TrkA mediates proliferation, invasiveness and epithelial-mesenchymal transition (EMT) in various CRPC cells. NGF promotes organoid growth in 3D models of CRPC cells, and specific inhibition of TrkA impairs all these responses. Thus TrkA represents a new biomarker to target in CRPC.

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.

TRAF4-mediated ubiquitination of NGF receptor TrkA regulates prostate cancer metastasis

Receptor tyrosine kinases (RTKs) are important drivers of cancers. In addition to genomic alterations, aberrant activation of WT RTKs plays an important role in driving cancer progression. However, the mechanisms underlying how RTKs drive prostate cancer remain incompletely characterized. Here we show that non-proteolytic ubiquitination of RTK regulates its kinase activity and contributes to RTK-mediated prostate cancer metastasis. TRAF4, an E3 ubiquitin ligase, is highly expressed in metastatic prostate cancer. We demonstrated here that it is a key player in regulating RTK-mediated prostate cancer metastasis. We further identified TrkA, a neurotrophin RTK, as a TRAF4-targeted ubiquitination substrate that promotes cancer cell invasion and found that inhibition of TrkA activity abolished TRAF4-dependent cell invasion. TRAF4 promoted K27- and K29-linked ubiquitination at the TrkA kinase domain and increased its kinase activity. Mutation of TRAF4-targeted ubiquitination sites abolished TrkA tyrosine autophosphorylation and its interaction with downstream proteins. TRAF4 knockdown also suppressed nerve growth factor (NGF) stimulated TrkA downstream p38 MAPK activation and invasion-associated gene expression. Furthermore, elevated TRAF4 levels significantly correlated with increased NGF-stimulated invasion-associated gene expression in prostate cancer patients, indicating that this signaling axis is significantly activated during oncogenesis. Our results revealed a posttranslational modification mechanism contributing to aberrant non-mutated RTK activation in cancer cells.

Inhibiting TRK Proteins in Clinical Cancer Therapy

Gene rearrangements resulting in the aberrant activity of tyrosine kinases have been identified as drivers of oncogenesis in a variety of cancers. The tropomyosin receptor kinase (TRK) family of tyrosine receptor kinases is emerging as an important target for cancer therapeutics. The TRK family contains three members, TRKA, TRKB, and TRKC, and these proteins are encoded by the genes NTRK1, NTRK2, and NTRK3, respectively. To activate TRK receptors, neurotrophins bind to the extracellular region stimulating dimerization, phosphorylation, and activation of downstream signaling pathways. Major known downstream pathways include RAS/MAPK/ERK, PLCγ, and PI3K/Akt. While being rare in most cancers, TRK fusions with other proteins have been well-established as oncogenic events in specific malignancies, including glioblastoma, papillary thyroid carcinoma, and secretory breast carcinomas. TRK protein amplification as well as alternative splicing events have also been described as contributors to cancer pathogenesis. For patients harboring alterations in TRK expression or activity, TRK inhibition emerges as an important therapeutic target. To date, multiple trials testing TRK-inhibiting compounds in various cancers are underway. In this review, we will summarize the current therapeutic trials for neoplasms involving NTKR gene alterations, as well as the promises and setbacks that are associated with targeting gene fusions.

A novel in-cell ELISA method for screening of compounds inhibiting TRKA phosphorylation, using KM12 cell line harboring TRKA rearrangement

Tropomyosin-related kinase A (TRKA) fusion was originally detected in colorectal carcinoma that had resulted in expression of the oncogenic chimeric protein TPM3-TRKA. Lately, many more rearrangements in TRK family of kinases generating oncogenic fusion proteins have been identified. These genetic rearrangements usually result in fusion of cytoplasmic kinase domain of TRK to another gene of interest resulting in constitutive kinase activity. Estimation of TRK inhibitor potency in a cellular context is required for drug discovery programs and is measured by receptor phosphorylation levels upon compound administration. However, since a large chunk of the TRK protein is lost in this rearrangement, it's difficult to set up sandwich ELISA for detection of receptor phosphorylation in any cell assay harboring these fusion proteins. In order to address this issue, we developed a novel and robust in-cell ELISA method which quantifies the phosphorylation of TRK kinase (Tyr 674/675) within the KM12 cells. This cell based method is more versatile & economical than conventional ELISA using engineered overexpressing cell line and/or western blot methods. Performance reliability & robustness for the validated assay were determined by %CV and Z factor in assays with reference molecule larotrectinib. This in-cell ELISA method can be used with any TRKA rearranged oncogenic fusion cell type and can be extended to other TRK isoforms as well. We have used this assay to screen novel molecules in KM12 cells and to study pharmacodynamic properties of compounds in TRKA signaling.

Crystal Structures of Neurotrophin Receptors Kinase Domain

Neurotrophins and their receptors (Trk) play key roles in the development of the nervous system and in cell survival. Trk receptors are therefore attractive pharmacological targets for brain disorders as well as for cancers. While the druggability of the extracellular domain of the receptors, that specifically binds neurotrophins, is yet to be proven, the intracellular kinase domains are attractive targets for small-molecule binding. The recent crystal structures of the three isoforms of the Trk family, TrkA, TrkB, and TrkC have been described in their apo forms and in complex with potent and selective pan-Trk inhibitors. The description of the kinase domain of each of the isoforms will be discussed in their apo forms or bound to potent inhibitors of interest in cancer therapy. Nononcology indications and selectivity issues will also be discussed.

Entrectinib is a potent inhibitor of Trk-driven neuroblastomas in a xenograft mouse model

Neuroblastoma (NB) is one of the most common and deadly childhood solid tumors. These tumors are characterized by clinical heterogeneity, from spontaneous regression to relentless progression, and the Trk family of neurotrophin receptors plays an important role in this heterogeneous behavior. We wanted to determine if entrectinib (RXDX-101, Ignyta, Inc.), an oral Pan-Trk, Alk and Ros1 inhibitor, was effective in our NB model. In vitro effects of entrectinib, either as a single agent or in combination with the chemotherapeutic agents Irinotecan (Irino) and Temozolomide (TMZ), were studied on an SH-SY5Y cell line stably transfected with TrkB. In vivo growth inhibition activity was studied in NB xenografts, again as a single agent or in combination with Irino-TMZ. Entrectinib significantly inhibited the growth of TrkB-expressing NB cells in vitro, and it significantly enhanced the growth inhibition of Irino-TMZ when used in combination. Single agent therapy resulted in significant tumor growth inhibition in animals treated with entrectinib compared to control animals [p < 0.0001 for event-free survival (EFS)]. Addition of entrectinib to Irino-TMZ also significantly improved the EFS of animals compared to vehicle or Irino-TMZ treated animals [p < 0.0001 for combination vs. control, p = 0.0012 for combination vs. Irino-TMZ]. We show that entrectinib inhibits growth of TrkB expressing NB cells in vitro and in vivo, and that it enhances the efficacy of conventional chemotherapy in in vivo models. Our data suggest that entrectinib is a potent Trk inhibitor and should be tested in clinical trials for NBs and other Trk-expressing tumors.

Identifying New Candidate Genes and Chemicals Related to Prostate Cancer Using a Hybrid Network and Shortest Path Approach

Prostate cancer is a type of cancer that occurs in the male prostate, a gland in the male reproductive system. Because prostate cancer cells may spread to other parts of the body and can influence human reproduction, understanding the mechanisms underlying this disease is critical for designing effective treatments. The identification of as many genes and chemicals related to prostate cancer as possible will enhance our understanding of this disease. In this study, we proposed a computational method to identify new candidate genes and chemicals based on currently known genes and chemicals related to prostate cancer by applying a shortest path approach in a hybrid network. The hybrid network was constructed according to information concerning chemical-chemical interactions, chemical-protein interactions, and protein-protein interactions. Many of the obtained genes and chemicals are associated with prostate cancer.

TrkB inhibition by GNF-4256 slows growth and enhances chemotherapeutic efficacy in neuroblastoma xenografts

PURPOSE

Neuroblastoma (NB) is one of the most common and deadly pediatric solid tumors. NB is characterized by clinical heterogeneity, from spontaneous regression to relentless progression despite intensive multimodality therapy. There is compelling evidence that members of the tropomyosin receptor kinase (Trk) family play important roles in these disparate clinical behaviors. Indeed, TrkB and its ligand, brain-derived neurotrophic factor (BDNF), are expressed in 50-60 % of high-risk NBs. The BDNF/TrkB autocrine pathway enhances survival, invasion, metastasis, angiogenesis and drug resistance.

METHODS

We tested a novel pan-Trk inhibitor, GNF-4256 (Genomics Institute of the Novartis Research Foundation), in vitro and in vivo in a nu/nu athymic xenograft mouse model to determine its efficacy in inhibiting the growth of TrkB-expressing human NB cells (SY5Y-TrkB). Additionally, we assessed the ability of GNF-4256 to enhance NB cell growth inhibition in vitro and in vivo, when combined with conventional chemotherapeutic agents, irinotecan and temozolomide (Irino-TMZ).

RESULTS

GNF-4256 inhibits TrkB phosphorylation and the in vitro growth of TrkB-expressing NBs in a dose-dependent manner, with an IC₅₀ around 7 and 50 nM, respectively. Furthermore, GNF-4256 inhibits the growth of NB xenografts as a single agent (p < 0.0001 for mice treated at 40 or 100 mg/kg BID, compared to controls), and it significantly enhances the antitumor efficacy of irinotecan plus temozolomide (Irino-TMZ, p < 0.0071 compared to Irino-TMZ alone).

CONCLUSIONS

Our data suggest that GNF-4256 is a potent and specific Trk inhibitor capable of significantly slowing SY5Y-TrkB growth, both in vitro and in vivo. More importantly, the addition of GNF-4256 significantly enhanced the antitumor efficacy of Irino-TMZ, as measured by in vitro and in vivo growth inhibition and increased event-free survival in a mouse xenograft model, without additional toxicity. These data strongly suggest that inhibition of TrkB with GNF-4256 can enhance the efficacy of current chemotherapeutic treatment for recurrent/refractory high-risk NBs with minimal or no additional toxicity.

Decreased urinary nerve growth factor reflects prostatic volume reduction and relief of outlet obstruction in patients with benign prostatic enlargement treated with dutasteride

OBJECTIVES

To examine urinary nerve growth factor before and after dutasteride treatment, and to analyze correlations between clinical parameters and change of urinary nerve growth factor in patients with benign prostatic enlargement.

METHODS

We prospectively studied 30 patients with benign prostatic enlargement who had not been satisfied with α-adrenergic antagonist monotherapy for more than 3 months. Before and 24 weeks after dutasteride add-on treatment, we assessed International Prostate Symptom Score, prostatic volume, filling cystometry and pressure-flow study. Urinary nerve growth factor was measured by enzyme-linked immunosorbent assay, and normalized to the urinary creatinine (nerve growth factor/creatinine) before and 24 weeks after dutasteride add-on treatment.

RESULTS

In baseline characteristics before dutasteride, there was no significant correlation between urinary nerve growth factor/creatinine and any clinical parameters including age, International Prostate Symptom Score, prostatic volume, presence of detrusor overactivity, detrusor pressure at maximum flow rate, bladder outlet obstruction index or bladder contractility index. Dutasteride significantly reduced prostatic volume (from 68 ± 31 mL to 49 ± 28 mL) and improved International Prostate Symptom Score (from 17.2 ± 8.7 to 13.1 ± 6.8), storage (from 8.0 ± 4.3 to 6.0 ± 2.9) and voiding symptom subscore of International Prostate Symptom Score (from 9.3 ± 5.7 to 7.1 ± 4.5). In urodynamic study, detrusor pressure at maximum flow rate (from 77 ± 32 cmH2 O to 59 ± 24 cmH2 O) and bladder outlet obstruction index (from 62 ± 32 to 42 ± 27) were significantly decreased after dutasteride treatment. Urinary nerve growth factor/creatinine was significantly decreased after dutasteride from 2.61 ± 2.50 to 1.64 ± 1.68. The change of urinary nerve growth factor/creatinine significantly correlated only with the change of prostatic volume (r = 0.38) and bladder outlet obstruction index (r = 0.36).

CONCLUSIONS

Urinary nerve growth factor decreases in association with reduction of prostatic volume and relief of bladder outlet obstruction. Urinary nerve growth factor might be useful as a biomarker to monitor the improvement of bladder outlet obstruction in patients with benign prostatic enlargement.

Tropomyosin receptor kinase inhibitors: a patent update 2009 - 2013

INTRODUCTION

Tropomyosin receptor kinases (Trks) are a family of three similar tyrosine kinases activated by peptide hormones of the neurotrophin family. The nerve growth factor antibody tanezumab has provided clinical proof of concept for inhibition of the TrkA pathway in pain. As an alternative modality, small-molecule inhibitors of the Trks have been pursued in recent years to probe the role of these neurotrophin pathways in pain, cancer and other indications.

AREAS COVERED

This paper reviews the patent literature between mid-2009 and 2013, claiming inhibitors of Trk family members as the primary biological targets. Additional patents have been reviewed where Trk is not the main kinase of interest but in which high Trk potency is observed and the chemical matter is particularly noteworthy. Patents pre-dating this period have been reviewed previously. Scifinder and Google were used to find relevant patents and clinical information using Trk or Tropomyosin as the search term.

EXPERT OPINION

Considerable recent progress has been made in the identification of selective pan Trk inhibitors with pharmacodynamic and pharmacokinetic properties appropriate for clinical evaluation. Inhibitors of both active and inactive conformations of the Trks as well as peripherally restricted molecules have been identified. Furthermore, TrkA-selective allosteric inhibitors have recently been disclosed, which enables the biology of this isoform to be probed. The recent identification of a TrkA gene fusion in a subset of lung cancer patients will increase further the attraction of Trk inhibition to the pharmaceutical industry.

Evaluation of the antitumor effects of BPR1J-340, a potent and selective FLT3 inhibitor, alone or in combination with an HDAC inhibitor, vorinostat, in AML cancer

Overexpression or/and activating mutation of FLT3 kinase play a major driving role in the pathogenesis of acute myeloid leukemia (AML). Hence, pharmacologic inhibitors of FLT3 are of therapeutic potential for AML treatment. In this study, BPR1J-340 was identified as a novel potent FLT3 inhibitor by biochemical kinase activity (IC₅₀ approximately 25 nM) and cellular proliferation (GC₅₀ approximately 5 nM) assays. BPR1J-340 inhibited the phosphorylation of FLT3 and STAT5 and triggered apoptosis in FLT3-ITD⁺ AML cells. The pharmacokinetic parameters of BPR1J-340 in rats were determined. BPR1J-340 also demonstrated pronounced tumor growth inhibition and regression in FLT3-ITD⁺ AML murine xenograft models. The combination treatment of the HDAC inhibitor vorinostat (SAHA) with BPR1J-340 synergistically induced apoptosis via Mcl-1 down-regulation in MOLM-13 AML cells, indicating that the combination of selective FLT3 kinase inhibitors and HDAC inhibitors could exhibit clinical benefit in AML therapy. Our results suggest that BPR1J-340 may be further developed in the preclinical and clinical studies as therapeutics in AML treatments.

c-Src activation through a TrkA and c-Src interaction is essential for cell proliferation and hematological malignancies

Although the kinase receptor TrkA may play an important role in acute myeloid leukemia (AML), its involvement in other types of leukemia has not been reported. Furthermore, how it contributes to leukemogenesis is unknown. Here, we describe a molecular network that is important for TrkA function in leukemogenesis. We found that TrkA is frequently overexpressed in other types of leukemia such as acute lymphoblastic leukemia (ALL), chronic myelogenous leukemia (CML), and myelodysplastic syndrome (MDS) including AML. In addition, TrkA was overexpressed in patients with MDS or secondary AML evolving from MDS. TrkA induced significant hematological malignancies by inducing PLK-1 and Twist-1, and enhanced survival and proliferation of leukemia, which was correlated with activation of the phosphatidylinositol 3-kinase/Akt/mTOR pathway. Moreover, endogenous TrkA associated with c-Src complexes was detected in leukemia. Suppression of c-Src activation by TrkA resulted in markedly decreased expression of PLK-1 and Twist-1 via suppressed activation of Akt/mTOR cascades. These data suggest that TrkA plays a key role in leukemogenesis and reveal an unexpected physiological role for TrkA in the pathogenesis of leukemia. These data have important implications for understanding various hematological malignancies.

TGFβ1 alters androgenic metabolites and hydroxysteroid dehydrogenase enzyme expression in human prostate reactive stromal primary cells: Is steroid metabolism altered by prostate reactive stromal microenvironment?

The inflammatory tissue microenvironment can be an active promoter in preneoplastic cancer lesions. Altered steroid hormone metabolism as induced by the inflammatory microenvironment may contribute to epithelial cancer progression. Dehydroepiandrosterone sulfate (DHEAS) is the most abundant endogenous steroid hormone present in human serum and can be metabolized to DHEA, androgens and/or estrogens in peripheral tissues. We have previously reported that TGFβ1-induced reactive prostate stromal cells increase DHEA metabolism to active androgens and alter prostate cancer cell gene expression. While much of the focus on mechanisms of prostate cancer and steroid metabolism is in the epithelial cancer cells, this study focuses on TGFβ1-induced effects on DHEA metabolic pathways and enzymes in human prostate stromal cells. In DHEA-treated primary prostate stromal cells, TGFβ1 produced time- and dose-dependent increases in metabolism of DHEA to androstenedione and testosterone. Also TGFβ1-treated prostate stromal cells exhibited changes in the gene expression of enzymes involved in steroid metabolism including up-regulation of 3β hydroxysteroid dehydrogenase (HSD), and down-regulation of 17βHSD5, and 17βHSD2. These studies suggest that reactive prostate stroma and the inflammatory microenvironment may contribute to altered steroid metabolism and increased intratumoral androgens.

Homage to Rita Levi-Montalcini, the queen of modern neuroscience

The first cell growth factor, nerve growth factor (NGF), was discovered by Rita Levi-Montalcini (RLM) in the early 1950s. Originally identified as neurite outgrowth-stimulating factor, later studies revealed that non-neuronal cells, including immune cells, endothelial cells, cardiomyocytes, pancreatic beta cells, prostate epithelial and adipose tissue cells, were also targets for and/or sources of NGF. Nerve growth factor is well recognised as mediating multiple biological phenomena, ranging from the neurotrophic through immunotrophic and epitheliotrophic to metabotrophic effects. Consequently, NGF and other members of the neurotrophin family are implicated in the pathogenesis of a large spectrum of neuronal and non-neuronal diseases, ranging from Alzheimer's and other neurodegenerative diseases to atherosclerosis and cardiometabolic disorders. Recent studies have demonstrated the therapeutic potentials of NGF in these conditions, including ocular and cutaneous diseases. NGF TrkA receptor antagonists emerged as novel drugs for pain, prostate and breast cancer, melanoma and urinary bladder syndromes. Here, we briefly describe the 'unpredictable' ideogenesis of the discovery of NGF, a eureka in the neuroscience.

The multiple life of nerve growth factor: tribute to rita levi-montalcini (1909-2012)

At the end of the 19(th) century, it was envisaged by Santiago Ramon y Cajal, but not, proven, that life at the neuronal level requires trophic support. The proof was obtained in the early 1950's by work initiated by Rita Levi-Montalcini (RLM) discovering the nerve growth factor (NGF). Today, NGF and its relatives, collectively designated neurotrophins, are well recognized as mediators of multiple biological phenomena in health and disease, ranging from the neurotrophic through immunotrophic and epitheliotrophic to metabotrophic effects. Consequently, NGF and other neurotrophins are implicated in the pathogenesis of a large spectrum of neuronal and non-neuronal diseases, from Alzheimer's and other neurodegenerative diseases to atherosclerosis and other cardiometabolic diseases. Recent studies demonstrated the therapeutic potentials of NGF in these diseases, including ocular and cutaneous diseases. Furthermore, NGF TrkA receptor antagonists emerged as novel drugs for pain, prostate and breast cancer, melanoma, and urinary bladder syndromes. Altogether, NGF's multiple potential in health and disease is briefly described here.

Discovery of Disubstituted Imidazo[4,5-b]pyridines and Purines as Potent TrkA Inhibitors

Trk receptor tyrosine kinases have been implicated in cancer and pain. A crystal structure of TrkA with AZ-23 (1a) was obtained, and scaffold hopping resulted in two 5/6-bicyclic series comprising either imidazo[4,5-b]pyridines or purines. Further optimization of these two fusion series led to compounds with subnanomolar potencies against TrkA kinase in cellular assays. Antitumor effects in a TrkA-driven mouse allograft model were demonstrated with compounds 2d and 3a.

Effects of castration on the expression of the NGF and TrkA in the vas deferens and accessory male genital glands of the rat

Nerve Growth Factor (NGF) is a member of the neurotrophin family. Neurotrophins exert their effects by binding to corresponding receptors, which are formed by the tyrosine protein kinases TrkA, TrkB, and TrkC, and the low affinity p75NTR receptor. The role of neurotrophins in the biology of male genital organs is far from clear. In particular, little is known about the influence of sex hormones on the expression of neurotrophins and their receptors. In the present study, using immunohistochemistry and real time RT-PCR, we investigated the expression of NGF and TrkA in the vas deferens and accessory male genital glands in normal and castrated rats.In normal rats, both NGF- and TrkA-immunoreactivities (IR) were localized in the epithelial layer of the vas deferens. NGF-IR was also found in the stroma and epithelium of the vesicular gland and prostate. TrkA-IR was distributed in the epithelial cells of vesicular and prostate glands. The nerves were weakly immunoreactive in all the examined organs. After castration the immunoreactivities increased. Real-time RT-PCR experiments indicated that NGF and TrkA mRNA levels increased significantly after castration. These results suggest that NGF and TrkA are expressed in the internal male genital organs of the rat and that their expression is downregulated by androgen hormones. We hypothesize NGF and TrkA play a role in the processes that regulate the involution of these organs under conditions of androgen deprivation.

Transforming growth factor β1 increase of hydroxysteroid dehydrogenase proteins is partly suppressed by red clover isoflavones in human primary prostate cancer-derived stromal cells

Transforming growth factor β1 (TGF-β1) increases dehydro-epiandrosterone (DHEA) metabolism to androgens and prostate-specific antigen (PSA) in a prostate tissue model where stromal (6S) cells and epithelial (LAPC-4) cells are cocultured. Red clover (RC) isoflavones inhibits transforming growth factor (TGF)-β-induced androgenicity. Mechanisms controlling those activities were explored. Three hydroxysteroid dehydrogenases (HSDs), 3β-HSD, HSD-17β1 and HSD-17β5 involved in metabolizing DHEA to testosterone (TESTO) were investigated. Individual depletion of HSDs in 6S cells significantly reduced TGF-β1/DHEA-induced PSA in LAPC-4 cells in cocultures. Monomer amounts of 3β-HSD were similar without or with TGF-β1 in both cell types but aggregates of 3β-HSD in 6S cells were much higher than those in LAPC-4 cells and were upregulated by TGFβ in 6S cells. Basal and TGF-β1-treated levels of HSD-17β1 and HSD-17β5 in LAPC-4 cells were significantly lower than in 6S cells, whereas levels of HSD-17β1 but not HSD-17β5 were TGFβ inducible. 6S cell HSD genes expression induced by TGFβ or androgen signaling was insignificant to contribute TGF-β1/DHEA-upregulated protein levels of HSDs. RC decreased TGF-β1- upregulation of aggregates of 3β-HSD but not HSD-17β1. Depletion of TGFβ receptors (TGFβ Rs) reduced TGF-β1/DHEA-upregulated HSDs and TESTO. Immunoprecipitation studies demonstrated that TGF-β1 disrupted associations of TGFβ Rs/HSDs aggregates, whereas RC suppressed the dissociations of aggregates of 3β-HSD but not HSD-17β1 from the receptors. Given that TGFβ Rs are recycled with or without ligand, TGF-β1-induced disassociation of the HSDs from TGFβ Rs may increase stability and activity of the HSDs. These data suggest a pathway connecting overproduction of TGFβ with increased PSA in prostate cancer.

TRK-A, HER-2/neu, and KIT Expression/Activation Profiles in Salivary Gland Carcinoma

Salivary duct carcinomas (SDCs) and adenoid cystic carcinomas (ACCs) are the most aggressive and the most frequent carcinomas of the salivary glands, respectively. Little is known about them in terms of molecular/biochemical characterization and conventional treatments are ineffective. On cryopreserved material, we analyzed the expression/activation status of TRK-A, HER-2/neu, and KIT receptors by means of immunoprecipitation and Western blot analysis experiments, and the presence of their cognate ligands by means of Western blot analysis and/or reverse transcription-polymerase chain reaction in 9 SDCs, 12 ACCs, and 8 normal glands. The amplification status of HER-2/neu was also investigated by means of fluorescent in situ hybridization analysis on fixed material. The receptor tyrosine kinase (RTK)-deregulated profile of the SDCs was characterized by the overexpression of activated TRK-A in the presence of its ligand, and the overexpression of HER-2/neu sustained by gene amplification. The RTK signature of the ACCs was represented by the overexpression of activated KIT and TRK-A and their cognate ligands, and the overexpression of activated HER-2/neu, in the absence of gene amplification, possibly sustained by epidermal growth factor receptor heterodimerization. In conclusion, SDCs and ACCs, although sharing TRK-A autocrine loop activation, have different pathologically activated RTK-deregulated profiles that may be potential targets for pharmacological RTK inhibitors.

Androgen-induced PSA expression requires not only activation of AR but also endogenous IGF-I or IGF-I/PI3K/Akt signaling in human prostate cancer epithelial cells

BACKGROUND

Prostate cancer (PrCa) risk is positively associated with levels of insulin-like growth factor I (IGF-I) and prostate specific antigen (PSA), both androgen receptor (AR) signaling target genes in PrCa cells. Although activated AR is required for androgen-induction of expression of both genes, effects of the IGF-I signaling pathways on the androgen-induction of PSA have not been studied.

METHODS

Human prostate stromal and epithelial cancer cells were treated alone or in coculture with steroid hormone and/or inhibitors. Gene or protein expression was analyzed by real time RT-PCR or Western blotting of lysates, nuclear extracts, or immunoprecipitated products.

RESULTS

In PrCa epithelial cells, endogenous IGF-I, significantly induced by R1881, was required for R1881-induction of PSA. Increased IGF-I correlated with accumulation of cytoplasmic dephospho β-catenin (CPDP β-catenin), a co-activator of AR signaling. Exogenous IGF-I enhanced R1881-induced PSA and accumulation of CPDP β-catenin in LAPC-4 cells. Functional depletion of IGF-I or IGF-I receptor diminished PSA induction. Induction of IGF-I reached a plateau while PSA consecutively increased. Inhibiting PI3K abolished R1881-induced Akt phosphorylation, CPDP and nuclear β-catenin and nuclear association of AR/β-catenin, consequently abrogating R1881-induced expression of IGF-I and/or PSA.

CONCLUSIONS

By integrating androgen, IGF-I and β-catenin signaling pathways, these data reveal that androgen-induced PSA expression requires activation of AR and endogenous IGF-I or IGF-I/PI3K/Akt signaling, suggesting a positive feedback cycle for increased production of PSA associated with PrCa.

The neuronal influence on tumor progression

Nerve fibers accompany blood and lymphatic vessels all over the body. An extensive amount of knowledge has been obtained with regard to tumor angiogenesis and tumor lymphangiogenesis, yet little is known about the potential biological effects of "neoneurogenesis". Cancer cells can exploit the advantage of the factors released by the nerve fibers to generate a positive microenvironment for cell survival and proliferation. At the same time, they can stimulate the formation of neurites by secreting neurotrophic factors and axon guidance molecules. The neuronal influence on the biology of a neoplasm was initially described several decades ago. Since then, an increasing amount of experimental evidence strongly suggests the existence of reciprocal interactions between cancer cells and nerves in humans. Moreover, researchers have been able to demonstrate a crosstalk between cancer cells and nerve fibers as a strategy for survival. Despite all these evidence, a lot remains to be done in order to clarify the role of neurotransmitters, neuropeptides, and their associated receptor-initiated signaling pathways in the development and progression of cancer, and response to therapy. A global-wide characterization of the neurotransmitters or neuropeptides present in the tumor microenvironment would provide insights into the real biological influences of the neuronal tissue on tumor progression. This review is intended to discuss our current understanding of neurosignaling in cancer and its potential implications on cancer prevention and therapy. The review will focus on the soluble factors released by cancer cells and nerve endings, their biological effects and their potential relevance in the treatment of cancer.

Dysregulated TRK signalling is a therapeutic target in CYLD defective tumours

Individuals with germline mutations in the tumour suppressor gene CYLD are at high risk of developing disfiguring cutaneous appendageal tumours, the defining tumour being the highly organised cylindroma. Here, we analysed CYLD mutant tumour genomes by array comparative genomic hybridisation (aCGH) and gene expression microarray analysis. CYLD mutant tumours were characterised by an absence of copy number aberrations apart from loss-of-heterozygosity at chromosome 16q, the genomic location of the CYLD gene. Gene expression profiling of CYLD mutant tumours revealed dysregulated tropomyosin kinase (TRK) signalling with overexpression of TRKB and TRKC in tumours when compared to perilesional skin. Immunohistochemical analysis of a tumour microarray demonstrated strong membranous TRKB and TRKC staining in cylindromas, as well as elevated levels of ERK phosphorylation and BCL2 expression. Membranous TRKC overexpression was also observed in 70% of sporadic basal cell carcinomas. RNA interference mediated silencing of TRKB and TRKC, as well as treatment with the small molecule TRK inhibitor lestaurtinib, reduced colony formation and proliferation in three-dimensional primary cell cultures established from CYLD mutant tumours. These results suggest that TRK inhibition could be used as a strategy to treat tumours with loss of functional CYLD.

The sensors and regulators of cell-matrix surveillance in anoikis resistance of tumors

Normal cells continuously monitor the nature of their respective cellular microenvironment. They are equipped with an inherent molecular defense to detect changes that can precipitate and trigger an oncogenic cascade in the internal and external environment of cells. The process called anoikis unleashes many a characteristic molecular change in the cells which eventually program to cell death in response to cell detachment and inappropriate cellular attachment, both of which can otherwise potentiate the ability of cells to preferentially pursue a malignant course due to the release of molecular discipline which conforms them to a benign structural and functional spectrum. The initiation and propagation of signaling that serves as a switch to cell survival or cell death mediated by surveillance of cell microenvironment is comprised of many heterogeneous sets of molecules interacting mainly at the interface of cell-extracellular matrix. Transforming cells continuously reprogram their signaling characteristics in sensing and modulating the stimuli from cell surface molecules like integrins, cadherins and immunoglobulin family of cell adhesion molecules at adhesion complexes, which enables them to resist anoikis and metastasize to different organs. Actin cytoskeleton binds BIM and Bcl2 modifying factor (BMF), which are regulated by the adhesion status and consequent conformation of cytoskeleton in the cells. This review aims at an integrated synopsis of fundamental mechanisms of the critical interactions of cell surface molecules to facilitate a focused analysis of the differential regulation of signaling processes at cell-ECM junctions that collectively rein the anoikis resistance, which in turn impacts metastatic aggressiveness and drug resistance of tumors originating from respective organs.

Natural antibodies against nerve growth factor inhibit in vitro prostate cancer cell metastasis

Prostate cancer is a major cause of death in older men, and bone metastasis is the primary cause of morbidity and mortality in prostate cancer. Prostate is an abundant source of nerve growth factor (NGF) that is secreted by malignant epithelial cells and utilized as an important autocrine factor for growth and metastasis. We previously showed that intravenous gammaglobulin (IVIg) contains natural antibodies against NGF, which inhibit growth and differentiation of the NGF-dependent cell line PC-12. In the present study, we examined the effects of these natural antibodies on in vitro migration or metastasis of two prostate cancer cell lines namely DU-145 and PC-3. Cancer cell migration was assessed using these cell lines in the upper chambers of Matrigel invasion chambers. The effects of IVIg and affinity-purified anti-NGF antibodies on cell migration through membrane into the lower chamber were assessed in dose/response experiments by a colorimetric method. Affinity-purified natural IgG anti-NGF antibody inhibited DU-145 migration by 38% (p = 0.01) and PC-3 migration by 25% (p = 0.02); whereas, a monoclonal anti-NGF antibody inhibited DU-145 migration by 40% (p = 0.01) and PC-3 migration by 37% (p = 0.02), at the same concentration. When IVIg was depleted of NGF-specific IgG by affinity chromatography, there was no significant inhibition of migration of the DU-145 and PC-3 cells at a concentration of 1 mg/well. Removal of the NGF-specific antibody from the IVIg was also demonstrated by a lack of effect on PC-12 cell differentiation. Therefore, IVIg is able to inhibit the migration of prostate cancer cell lines, through Matrigel chambers in vitro, only when the natural NGF-specific antibodies actively are present in IVIg.

Chiral kinase inhibitors

Small molecule kinase inhibitors are important tools for studying cellular signaling pathways, phenotypes and are, occasionally, useful clinical agents. With stereochemistry pervasive throughout the molecules of life it is no surprise that a single stereocenter can bestow a ligand with distinct binding affinities to various protein targets. While the majority of small molecule kinase inhibitors reported to date are achiral, a number of asymmetric compounds show great utility as tools for probing kinase-associated biomolecular events as well as promising therapeutic leads. The mechanism by which chirality is introduced varies but includes screening of chiral libraries, incorporation of chiral centers during optimization efforts and the rational installation of a chiral moiety as guided by structural and modeling efforts. Here we discuss several advanced chiral small molecule kinase inhibitors where stereochemistry plays an important role in terms of potency and selectivity.

TrkC plays an essential role in breast tumor growth and metastasis

Tropomyosin-related kinase (Trk) C, a member of the Trk family of neurotrophin receptors, has been implicated in the growth and survival of human cancer tissues. Here, we report that TrkC is frequently overexpressed in human breast cancers and plays an essential role in tumor growth and metastasis. Ectopic expression of TrkC in non-malignant mammary epithelial cells suppressed anoikis, which correlated with activation of the Ras-mitogen-activated protein kinase and phosphatidylinositol-3-OH kinase (PI3K)/Akt pathways, and reduced expression of the metastatic regulator Twist. Furthermore, suppression of TrkC expression in highly metastatic mammary carcinoma cells inhibited their growth in vitro, as well as their ability to metastasize from the mammary gland to the lung in vivo. These results have identified TrkC as a critical regulator of breast cancer cell growth and metastasis.

Dual targeting of CDK and tropomyosin receptor kinase families by the oral inhibitor PHA-848125, an agent with broad-spectrum antitumor efficacy

Altered expression and activity of cyclin-dependent kinase (CDK) and tropomyosin receptor kinase (TRK) families are observed in a wide variety of tumors. In those malignancies with aberrant CDK activation, the retinoblastoma protein (pRb) pathway is deregulated, leading to uncontrolled cell proliferation. Constitutive activation of TRKs is instead linked to cancer cell survival and dissemination. Here, we show that the novel small-molecule PHA-848125, a potent dual inhibitor of CDKs and TRKs, possesses significant antitumor activity. The compound inhibits cell proliferation of a wide panel of tumoral cell lines with submicromolar IC(50). PHA-848125-treated cells show cell cycle arrest in G(1) and reduced DNA synthesis, accompanied by inhibition of pRb phosphorylation and modulation of other CDK-dependent markers. The compound additionally inhibits phosphorylation of TRKA and its substrates in cells, which functionally express this receptor. Following oral administration, PHA-848125 has significant antitumor activity in various human xenografts and carcinogen-induced tumors as well as in disseminated primary leukemia models, with plasma concentrations in rodents in the same range as those found active in inhibiting cancer cell proliferation. Mechanism of action was also confirmed in vivo as assessed in tumor biopsies from treated mice. These results show that the dual CDK-TRK inhibitor PHA-848125 has the potential for being a novel and efficacious targeted drug for cancer treatment.

Nerve growth factor promotes breast cancer angiogenesis by activating multiple pathways

Background

Although several anti-angiogenic therapies have been approved in the treatment of cancer, the survival benefits of such therapies are relatively modest. Discovering new molecules and/or better understating signaling pathways of angiogenesis is therefore essential for therapeutic improvements. The objective of the present study was to determine the involvement of nerve growth factor (NGF) in breast cancer angiogenesis and the underlying molecular mechanisms.

Results

We showed that both recombinant NGF and NGF produced by breast cancer cells stimulated angiogenesis in Matrigel plugs in immunodeficient mice. NGF strongly increased invasion, cord formation and the monolayer permeability of endothelial cells. Moreover, NGF-stimulated invasion was under the control of its tyrosine kinase receptor (TrkA) and downstream signaling pathways such as PI3K and ERK, leading to the activation of matrix metalloprotease 2 and nitric oxide synthase. Interestingly, NGF increased the secretion of VEGF in both endothelial and breast cancer cells. Inhibition of VEGF, with a neutralizing antibody, reduced about half of NGF-induced endothelial cell invasion and angiogenesis in vivo.

Conclusions

Our findings provided direct evidence that NGF could be an important stimulator for breast cancer angiogenesis. Thus, NGF, as well as the activated signaling pathways, should be regarded as potential new targets for anti-angiogenic therapy against breast cancer.

Nerve growth factor signaling in prostate health and disease

The prostate is one of the most abundant sources of nerve growth factor (NGF) in different species, including humans. NGF and its receptors are implicated in the control of prostate cell proliferation and apoptosis and it can either support or suppress cell growth. The co-expression of both NGF receptors, p75(NGFR) and tropomyosin-related kinase A (trkA), represents a crucial condition for the antiproliferative effect of NGF; indeed, p75(NGFR) is progressively lost during prostate tumorigenesis and its disappearance represents a malignancy marker of prostate adenocarcinoma (PCa). Interestingly, a dysregulation of NGF signal transduction was found in a number of human tumors. This review summarizes the current knowledge on the role of NGF and its receptors in prostate and in PCa. Conclusions bring to the hypothesis that the NGF network could be a candidate for future pharmacological manipulation in the PCa therapy: in particular the re-expression of p75(NTR) and/or the negative modulation of trkA could represent a target to induce apoptosis and to reduce proliferation and invasiveness of PCa.

Novel localization of low affinity NGF receptor (p75) in the stroma of prostate cancer and possible implication in neoplastic invasion: an immunohistochemical and ultracytochemical study

BACKGROUND

The localization of low affinity nerve growth factor receptor (p75) in prostate carcinogenesis is still unclear. Our aim was to reinvestigate the localization of p75 in normal and pathological prostate and to check a possible correlation to neoplastic grading.

METHODS

Specimens from 33 prostate cancers and from normal prostatic tissue were analyzed for p75 expression at light and ultrastructural levels.

RESULTS

In normal tissue p75-immunoreactivity was restricted to basal cells in the epithelial compartment and to nerves and blood vessel in stroma. During carcinogenesis, p75-immunoreactivity progressively decreased at the periphery of the foci according to the increase in malignancy. No p75-immunoreactivity was detected inside of the foci. On the contrary, in stroma we found a dramatic increase in p75-immunoreactivity correlated to an increase in malignancy. In this compartment, for the first time ultrastructural analysis identified p75-immunoreactivity in smooth muscle cells (SMC) that are p75-negative in normal conditions.

CONCLUSION

The present study confirms at ultrastructural level a malignant-dependent p75 decrease in basal cells of neoplastic foci. Furthermore, we show a novel, malignant-dependent localization of p75 in SMC in the stroma around the neoplastic foci. Since p75 expression is present in muscle cells only during the earliest stages of differentiation and mature muscle cells lose this expression, we hypothesize that p75 re-expression in stromal SMC is a further mechanism related to the general de-differentiation of the stroma connected to the neoplastic invasion. According to this hypothesis, our results suggest that p75 analysis could be a novel prognostic marker for prostate cancer.

Ku86 is important for TrkA overexpression-induced breast cancer cell invasion

PURPOSE

We have recently shown that breast tumors express high levels of TrkA compared with normal breast tissues, with TrkA overexpression enhancing breast cancer cell invasion in vitro and metastasis in animal models. In this study, we tried to identify molecules involved in TrkA overexpression-mediated biological effects in breast cancer cells.

EXPERIMENTAL DESIGN

We used a proteomic-based approach to identify proteins involved in TrkA overexpression-stimulated invasion of MDA-MB-231 breast cancer cells. Proteins from control and TrkA overexpressing cells were separated using a cup-loading two-dimensional electrophoresis system before MALDI and LC-MS/MS mass spectrometry analysis.

RESULTS

Among several putative regulated proteins, Ku86 was found increased in TrkA overexpressing cells. Moreover, Ku86 was co-immunoprecipitated with TrkA, suggesting the interaction of these two proteins in TrkA overexpressing cells. Interestingly, inhibition with small-interfering RNA and neutralizing antibodies showed that Ku86 was required for TrkA-stimulated cell invasion.

CONCLUSIONS AND CLINICAL RELEVANCE

These data allowed the identification of Ku86 as a new player involved in metastasis in breast cancer cells. Our findings suggest that TrkA and its down stream signaling pathways should be regarded as potential new targets for the development of future breast cancer therapy.

Striking the target in Wnt-y conditions: intervening in Wnt signaling during cancer progression

Wnt signaling can be divided into three pathways, namely the canonical Wnt/beta-catenin pathway, and the non-canonical (or heretical) Wnt/Ca(2+) and planar cell polarity (PCP) pathways. Although the canonical Wnt/beta-catenin pathway is the best described in cancer, increasing data points to the importance of the heretical Wnt pathways in several aspects of tumor progression. The recent advances in understanding the players and mechanisms by which these Wnt pathways contribute to cancer progression have led to the identification of numerous molecules that are already, or could be considered, targets for cancer therapy.

Neurotrophin-3 production promotes human neuroblastoma cell survival by inhibiting TrkC-induced apoptosis

Tropomyosin-related kinase receptor C (TrkC) is a neurotrophin receptor with tyrosine kinase activity that was expected to be oncogenic. However, it has several characteristics of a tumor suppressor: its expression in tumors has often been associated with good prognosis; and it was recently demonstrated to be a dependence receptor, transducing different positive signals in the presence of ligand but inducing apoptosis in the absence of ligand. Here we show that the TrkC ligand neurotrophin-3 (NT-3) is upregulated in a large fraction of aggressive human neuroblastomas (NBs) and that it blocks TrkC-induced apoptosis of human NB cell lines, consistent with the idea that TrkC is a dependence receptor. Functionally, both siRNA knockdown of NT-3 expression and incubation with a TrkC-specific blocking antibody triggered apoptosis in human NB cell lines. Importantly, disruption of the NT-3 autocrine loop in malignant human neuroblasts triggered in vitro NB cell death and inhibited tumor growth and metastasis in both a chick and a mouse xenograft model. Thus, we believe that our data suggest that NT-3/TrkC disruption is a putative alternative targeted therapeutic strategy for the treatment of NB.

The orphan tyrosine kinase receptor, ROR2, mediates Wnt5A signaling in metastatic melanoma

Tyrosine kinase receptors represent targets of great interest for cancer therapy. Here we demonstrate, for the first time, the importance of the orphan tyrosine kinase receptor, ROR2, in melanoma progression. Using melanoma tissue microarrays we show that ROR2 is expressed predominantly in metastatic melanoma. Because ROR2 has been shown to specifically interact with the non-canonical Wnt ligand, Wnt5A, this corroborates our previous data implicating Wnt5A as a mediator of melanoma metastasis. We show here that increases in Wnt5A cause increases in ROR2 expression, as well as the PKC-dependent, clathrin-mediated internalization of ROR2. WNT5A knockdown by siRNA decreases ROR2 expression, but silencing of ROR2 has no effect on WNT5A levels. ROR2 knockdown does, however, result in a decrease in signaling downstream of Wnt5A. Using in vitro and in vivo metastasis assays we demonstrate that ROR2 is necessary for the Wnt5A-mediated metastasis of melanoma cells. These data imply that ROR2 may represent a novel target for melanoma therapy.

On Trk--the TrkB signal transduction pathway is an increasingly important target in cancer biology

In the beginning, Trk was an oncogene. Yet Neurotrophin-Trk signaling came to preeminence in the field of neurobiology. Now it is appreciated that Trks regulate important processes in nonneuronal cells and, in addition to their impact on tumors of neural origin, may contribute to the pathogenesis of carcinomas, myelomas, and prostate and lymphoid tumors. Although mutations and rearrangements of Trk are seen only sporadically in human cancers, such as medullary thyroid carcinoma, a number of recent studies indicate that expression of TrkB contributes to tumor pathology. In neuroblastoma, TrkA expression marks good prognosis which TrkB and Brain-derived neurotrophic factor (BDNF) expression marks poor prognosis. Activation of the BDNF/TrkB signal transduction pathway also stimulates tumor cell survival and angiogenesis and contributes to resistance to cytotoxic drugs and anoikis, enabling cells to acquire many of the characteristic features required for tumorigenesis. Small molecule inhibitors, such as Cephalon's CEP-701, are in phase 1 and 2 clinical trials, and a series of AstraZeneca Trk inhibitors are poised to enter the clinic. As monotherapy, inhibitors may be effective only in tumors with activating Trk mutations. Important clinical follow-up will be the assessment of Trk inhibitors in combination with standard chemo- or radiotherapy or other signal transduction pathway inhibitors.