Manipulation of the nerve growth factor network in prostate cancer

Targeting the Nerve Growth Factor Signaling Impairs the Proliferative and Migratory Phenotype of Triple-Negative Breast Cancer Cells

Triple-negative breast cancer is a heterogeneous disease that still lacks specific therapeutic approaches. The identification of new biomarkers, predictive of the disease's aggressiveness and pharmacological response, is a challenge for a more tailored approach in the clinical management of patients. Nerve growth factor, initially identified as a key factor for neuronal survival and differentiation, turned out to be a multifaceted molecule with pleiotropic effects in quite divergent cell types, including cancer cells. Many solid tumors exhibit derangements of the nerve growth factor and its receptors, including the tropomyosin receptor kinase A. This receptor is expressed in triple-negative breast cancer, although its role in the pathogenesis and aggressiveness of this disease is still under investigation. We now report that triple-negative breast cancer-derived MDA-MB-231 and MDA-MB-453 cells express appreciable levels of tropomyosin receptor kinase A and release a biologically active nerve growth factor. Activation of tropomyosin receptor kinase by nerve growth factor treatment positively affects the migration, invasion, and proliferation of triple-negative breast cancer cells. An increase in the size of triple-negative breast cancer cell spheroids is also detected. This latter effect might occur through the nerve growth factor-induced release of matrix metalloproteinase 9, which contributes to the reorganization of the extracellular matrix and cell invasiveness. The tropomyosin receptor kinase A inhibitor GW441756 reverses all these responses. Co-immunoprecipitation experiments in both cell lines show that nerve growth factor triggers the assembly of the TrkA/β1-integrin/FAK/Src complex, thereby activating several downstream effectors. GW441756 prevents the complex assembly induced by nerve growth factor as well as the activation of its dependent signaling. Pharmacological inhibition of the tyrosine kinases Src and FAK (focal adhesion kinase), together with the silencing of β1-integrin, shows that the tyrosine kinases impinge on both proliferation and motility, while β1-integrin is needed for motility induced by nerve growth factor in triple-negative breast cancer cells. The present data support the key role of the nerve growth factor/tropomyosin receptor kinase A pathway in triple-negative breast cancer and offer new hints in the diagnostic and therapeutic management of patients.

Perineural invasion in cervical cancer: pay attention to the indications of nerve-sparing radical hysterectomy

Perineural invasion (PNI) in early-stage cervical cancer, is associated with multiple high-risk factors and represents a poor outcome in the patients. For nerve-sparing radical hysterectomy (NSRH) to become a standard and widely used treatment for cervical cancer, we need to define its oncological safety, and to establish standardized surgical procedures and indications of NSRH. Here, we review the definition and mechanisms, and clinical significance of PNI in cervical cancer, and discuss the indications of NSRH. PNI should be regarded as one of the main pathological features of cervical cancer and a factor affecting prognosis. A deeper understanding of PNI in cervical cancer, hopefully, will provide clear indications of NSRH.

Distinct Osteomimetic Response of Androgen-Dependent and Independent Human Prostate Cancer Cells to Mechanical Action of Fluid Flow: Prometastatic Implications

BACKGROUND AND METHODS

Prostate cancer frequently expresses an osteomimetic phenotype, but it is unclear how it is regulated and what biological and clinical implications it confers. Because mechanical forces physiologically regulate bone-remodeling activity in osteocytes, we hypothesized that mechanical action of fluid flow (MAFF) at the cancer microenvironment may similarly foster prostate cancer cell osteomimicry.

RESULTS

We showed that in vitro MAFF on androgen-dependent (LNCap) and androgen-independent (PC3) prostate cancer cells remarkably increased OPG, VEGF, RunX2, PTH1R, and PTHrP gene expression in both cell lines irrespective of their androgen dependency. MAFF also altered the cytokine secretion pattern of prostate cancer cells, including Ang2, SCF, and TNFα increase with TRAIL decrease in the supernatant of both cell lines; preferential increase of Leptin and PDGF-BB in LnCap and of VEGF, IL-8, and G-CSF in PC3; and exclusive increase of FGFβ, MIF, and PECAM-1 with HGF decrease in LnCap, and of TGBβ1, HGF, M-CSF, CXCL1, and CCL7 with NGF decrease in PC3. Murine MLO-Y4 osteocyte-conditioned medium (CM) abrogated M-CSF, G-CSG, IL-8, TNFα, and FGFβ secretion-stimulating activity of mechanical stimulation on PC3 cells, and did the opposite effect on LnCap cells. However, MAFF fostered osteomimetic gene expression response of PC3 cells, but not of LnCap cells, to mechanically stimulated osteocyte-CM. Moreover, it abrogated TNFα and IL-8 secretion inhibitory effect of osteocyte-CM on mechanically stimulated PC3 cells and G-CSF, TNFα, and FGFβ-stimulating effect on mechanically stimulated LnCap cells.

CONCLUSIONS

MAFF activated osteoblast-like phenotype of prostate cancer cells and altered their responses to osteocyte soluble factors. It also induced osteocyte production of osteomimetic gene expression- and cytokine secretion-stimulating factors for prostate cancer cells, particularly, when they were mechanically stimulated. Importantly, MAFF induced a prometastatic response in androgen-independent prostate cancer cells, suggesting the interest of mechanical stimulation-dependent transcription and secretion patterns as diagnostic biomarkers, and as therapeutic targets for the screening of bone-metastasizing phenotype inhibitors upregulated during prostate cancer cell response to MAFF at the cancer microenvironment. Prostate 77:321-333, 2017. © 2016 Wiley Periodicals, Inc.

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.

Nerve growth factor & TrkA as novel therapeutic targets in cancer

In the past 20years, nerve growth factor (NGF) and its receptors TrkA & p75NTR were recognized to be overexpressed in the overwhelming majority of human solid cancers. Recent studies discovered the presence of overactive TrkA signaling due to TrkA rearrangements or TrkA fusion products in frequent cancers like colorectal cancer, thyroid cancer, or acute myeloid leukemia. Thus, targeting TrkA/NGF via selective small-molecule-inhibitors or antibodies has gained enormous attention in the drug discovery sector. Clinical studies on the anti-cancer impact of NGF-blocking antibodies are likely to be accelerated after the recent removal of clinical holds on these agents by regulatory authorities. Based on these current developments, the present review provides not only a broad overview of the biological effects of NGF-TrkA-p75NTR on cancer cells and their microenvironment, but also explains why NGF and its receptors are going to evoke major interest as promising therapeutic anti-cancer targets in the coming decade.

Expression of nerve growth factor in the prostate of male rats in response to chronic stress and sympathetic denervation

Nerve growth factor (NGF) has been found in the normal prostate of the Wistar rat and is regarded as an important prostatic mitogen. We have previously shown that chronic stress induced epithelial hyperplasia while sympathetic denervation caused atrophy in the male Wistar rat prostate. NGF may have been a contributing mechanism to the hyperplasia and atrophy response that was observed. The aim of the present study was to investigate the expression of NGF in the prostate of the male rat in response to chronic stress and denervation. Two weeks of restraint water-immersion stress were used to induce a chronic stress model in Wistar rats. Denervation of the peripheral sympathetic nerve was induced by 6-hydroxydopamine. The expression levels of NGF in the dissected prostate lobes were examined by immunohistochemistry. After 14 days of stress, proliferation of the epithelium in the ventral lobes was observed, whereas the dorsolateral lobes were almost unaffected. NGF immunoreactive protein was localized to the columnar secretory epithelium lines of the prostate tissue. Stress and denervation led to an increase in NGF expression in the ventral lobes. In conclusion, NGF was involved in the hyperplasia and atrophy in the prostate of the male rat in response to chronic stress and sympathetic denervation, and thus may be a contributing factor in the pathophysiology of the prostate.

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.

Nerve growth factor signaling following unilateral pelvic ganglionectomy in the rat ventral prostate is age dependent

Benign prostatic hyperplasia (BPH) is a serious health concern and is an underlying cause of lower urinary tract symptoms (LUTS) in many men. In affected men, LUTS/BPH is believed to result from benign proliferation of the prostate resulting in bladder outlet obstruction. Postnatal growth of the prostate is controlled via growth factor and endocrine mechanisms. However, little attention had been given to the function of the autonomic nervous system in prostate growth and differentiation. Nerve growth factor (NGF) is a prostatic mitogen that has a trophic role in autonomic sensory end organ interaction. In this study, we examine how the autonomic nervous system influences prostate growth as a function of age by quantifying NGF in the rat ventral prostate (VP) after pelvic ganglionectomy. Unilateral pelvic ganglionectomy was performed on postnatal days 30 (P30), 60 and 120 Sprague-Dawley rats in comparison to sham controls (n=39). Semiquantitative RT-PCR, Western blotting and immunohistochemical analysis for NGF were performed on denervated, intact (contralateral side) and sham control VP 7 days after surgery. Ngf RNA expression was significantly increased in the denervated and intact hyperplastic VP. Western blotting showed age-dependent increases in NGF protein at P60 in the contralateral intact VP. NGF was localized in the nerves, basal cells and columnar epithelium of the prostatic ducts. Denervation causes age-dependent increases in NGF in the VP, which is a potential mechanism by which the autonomic nervous system may regulate prostate growth and lead to BPH/LUTS.

GPNMB/Osteoactivin as a Malignancy Biomarker in an Experimental Model of Human Prostate Adenocarcinoma

Background

The goal is to analyze the role of Osteactivin (OA) in human prostate adenocarcinoma (CaP) cell lines, DU145 and PC3. OA plays a role in proliferation, adhesion, differentiation and protein synthesis in normal and malignant cells. Further, the OA expression is specific of activated mature osteoblasts.

Methods

DU145 and PC3 were maintained under recommended conditions and treated, respectively, with 50 ng/mL for 8 days and with 100 ng/mL for 15 days of Nerve Growth Factor (NGF). The NGF-induced reduction of invasive capacity was assessed by the BioCoat Matrigel Invasion Chambers technique. The gene expression was evaluated by Q-RT-PCR, while the protein expression by indirect immunofluorescence and by western blot.

Results

NGF treatment of DU145 and PC3 induced a reduction of 95% and 78% of the invasive capacity. NGF treatment decreased OA expression at both mRNA and protein levels. The OA was secreted into the culture medium.

Conclusions

DU145 and PC3 cells expressed OA, that is strongly reduced by NGF treatment. Since it is known that OA is involved in the acquisition of the cell invasive capability, it could thus be hypothesized that OA could be a factor that contributes to the acquisition of invasive properties of PCa and could be proposed as a biomarker of cell tendency to metastatization.

Therapeutic potential of perineural invasion, hypoxia and desmoplasia in pancreatic cancer

Pancreatic cancer is one of the most fatal human malignancies. Though a relatively rare malignancy, it remains one of the deadliest tumors, with an extremely high mortality rate. The prognosis of patients with pancreatic cancer remains poor; only patients with small tumors and complete resection have a chance of a complete cure. Pancreatic cancer responds poorly to conventional therapies, including chemotherapy and irradiation. Tumor-specific targeted therapy is a relatively recent addition to the arsenal of anti-cancer therapies. It is important to find novel targets to distinguish tumor cells from their normal counterparts in therapeutic approaches. In the past few decades, studies have revealed the molecular mechanisms of pancreatic tumorigenesis, growth, invasion and metastasis. The proteins that participate in the pathophysiological processes of pancreatic cancer might be potential targets for therapy. This review describes the main players in perineural invasion, hypoxia and desmoplasia and the molecular mechanisms of these pathophysiological processes.

Phase I study of the safety, tolerability and pharmacokinetics of PHA-848125AC, a dual tropomyosin receptor kinase A and cyclin-dependent kinase inhibitor, in patients with advanced solid malignancies

PURPOSE

This phase I trial assessed the safety, maximally tolerated dose (MTD) and pharmacokinetics of TRKA/CDK inhibitor PHA-848125AC in adult patients with advanced/metastatic solid tumors.

PATIENTS AND METHODS

Patients with relapsed or refractory solid tumors, for which no standard therapy existed, were eligible. PHA-848125AC was administered orally in two schedules: daily for 7 consecutive days in 2-week cycles (i.e. 7 days on/7 days off q2wks; S1) or daily for 4 consecutive days a week for 3 weeks in 4-week cycles (i.e. 4 days on/3 days off x 3wks q4wks; S2).

RESULTS

Thirty-seven patients were treated in this study, 22 in S1 and 15 in S2. The recommended phase II dose (RP2D) was 150 mg/day for either schedule. The dose-limiting toxicities (DLTs) in S1 included ataxia (Grade 2-4) and tremors (Grade 2-3). In S2, DLTs included tremors (Grade 2-3), elevated lipase (Grade 3), increased creatinine (Grade 2), and nausea and vomiting (Grade 3). These events were all reversible. In S2, out of 14 patients evaluable for efficacy, 2 patients with thymic carcinoma, showed partial response and stable disease was observed in 3 patients. Stable disease was observed in 6 out 14 patients evaluable for efficacy on S1. Drug pharmacokinetics demonstrated a half-life of approximately 33 h, and dose-proportionality with accumulation by a factor of 3 after repeated administrations.

CONCLUSION

The RP2D of PHA-848125AC was 150 mg/day on both schedules. Based on the responses noted in thymic carcinoma, a phase II study for patients with that disease is currently enrolling.

Identification of novel inhibitors of tropomyosin-related kinase A through the structure-based virtual screening with homology-modeled protein structure

Tropomyosin-related kinase A (TrkA) is a promising target for the development of cancer and pain therapeutics. Here, we report the first successful example of the use of a structure-based virtual screening to identify novel TrkA inhibitors. The accuracy of the virtual screening was improved by introducing an accurate solvation free energy term into the original AutoDock scoring function. We applied a drug design protocol involving homology modeling, docking analysis of a large chemical library, and enzyme inhibition assays to identify six structurally diverse TrkA inhibitors with K(d) values ranging from 3 to 40 μM. The significant potencies and good physicochemical properties of these drug candidates strongly support their consideration in a development effort that would involve structure-activity relationship (SAR) studies to optimize the inhibitory activities. We also addressed the structural and energetic features associated with binding of the newly identified inhibitors in the ATP-binding site of TrkA. The results indicate that any structural modifications introduced for the purpose of enhancing the activity of TrkA inhibitors should maximize the attractive interactions within the ATP-binding site and simultaneously minimize the desolvation cost for complexation.

Nerve growth factor links oral cancer progression, pain, and cachexia

Cancers often cause excruciating pain and rapid weight loss, severely reducing quality of life in cancer patients. Cancer-induced pain and cachexia are often studied and treated independently, although both symptoms are strongly linked with chronic inflammation and sustained production of proinflammatory cytokines. Because nerve growth factor (NGF) plays a cardinal role in inflammation and pain, and because it interacts with multiple proinflammatory cytokines, we hypothesized that NGF acts as a key endogenous molecule involved in the orchestration of cancer-related inflammation. NGF might be a molecule common to the mechanisms responsible for clinically distinctive cancer symptoms such as pain and cachexia as well as cancer progression. Here we reported that NGF was highly elevated in human oral squamous cell carcinoma tumors and cell cultures. Using two validated mouse cancer models, we further showed that NGF blockade decreased tumor proliferation, nociception, and weight loss by orchestrating proinflammatory cytokines and leptin production. NGF blockade also decreased expression levels of nociceptive receptors TRPV1, TRPA1, and PAR-2. Together, these results identified NGF as a common link among proliferation, pain, and cachexia in oral cancer. Anti-NGF could be an important mechanism-based therapy for oral cancer and its related symptoms.

Brain-derived neurotrophic factor and neurotrophin-4/5 are expressed in breast cancer and can be targeted to inhibit tumor cell survival

PURPOSE

Given that nerve growth factor has previously been shown to be involved in breast cancer progression, we have tested here the hypothesis that the other neurotrophins (NT) are expressed and have an influence in breast tumor growth.

EXPERIMENTAL DESIGN

The expression of brain-derived neurotrophic factor (BDNF), NT-3 and NT-4/5, as well as the neurotrophin receptor p75(NTR), TrkB, and TrkC, was studied by RT-PCR, Western blotting, and immunohistochemistry in cell lines and tumor biopsies. The biological impacts of neurotrophins, and associated mechanisms, were analyzed in cell cultures and xenografted mice.

RESULTS

BDNF and NT-4/5 were expressed and secreted by breast cancer cells, and the use of blocking antibodies suggested an autocrine loop mediating cell resistance to apoptosis. The corresponding tyrosine kinase receptor TrkB was only rarely observed at full length, whereas the expression of TrkB-T1, lacking the kinase domain, as well as p75(NTR), were detected in all tested breast cancer cell lines and tumor biopsies. In contrast, NT-3 and TrkC were not detected. SiRNA against p75(NTR) and TrkB-T1 abolished the antiapoptotic effect of BDNF and NT-4/5, whereas the pharmacological inhibitors K252a and PD98059 had no effect, suggesting the involvement of p75(NTR) and TrkB-T1, but not kinase activities from Trks and MAPK. In xenografted mice, anti-BDNF, anti-NT-4/5, anti-p75(NTR), or anti-TrkB-T1 treatments resulted in tumor growth inhibition, characterized by an increase in cell apoptosis, but with no change in proliferation.

CONCLUSION

BDNF and NT-4/5 contribute to breast cancer cell survival and can serve as prospective targets in attempts to inhibit tumor growth.

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.

Identification of N,1,4,4-tetramethyl-8-{[4-(4-methylpiperazin-1-yl)phenyl]amino}-4,5-dihydro-1H-pyrazolo[4,3-h]quinazoline-3-carboxamide (PHA-848125), a potent, orally available cyclin dependent kinase inhibitor

The discovery of a novel class of inhibitors of cyclin dependent kinases (CDKs) is described. Starting from compound 1, showing good potency as inhibitor of CDKs but being poorly selective against a panel of serine-threonine and tyrosine kinases, new analogues were synthesized. Enhancement in selectivity, antiproliferative activity against A2780 human ovarian carcinoma cells, and optimization of the physical properties and pharmacokinetic profile led to the identification of highly potent and orally available compounds. Compound 28 (PHA-848125), which in the preclinical xenograft A2780 human ovarian carcinoma model showed good efficacy and was well tolerated upon repeated daily treatments, was identified as a drug candidate for further development. Compound 28 is currently undergoing phase I and phase II clinical trials.

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.

Transforming growth factor-beta induces nerve growth factor expression in pancreatic stellate cells by activation of the ALK-5 pathway

Nerve growth factor (NGF), a survival factor for neurons enforces pain by sensitizing nociceptors. Also in the pancreas, NGF was associated with pain and it can stimulate the proliferation of pancreatic cancer cells. Hepatic stellate cells (HSC) respond to NGF with apoptosis. Transforming growth factor (TGF)-beta, one of the strongest pro-fibrogenic activators of pancreatic stellate cells (PSC) induced NGF and its two receptors in an immortalized human cell line (ihPSC) and primary rat PSC (prPSC) as determined by RT-PCR, western blot, and immunofluorescence. In contrast to HSC, PSC expressed both NGF receptors, although p75(NTR) expression was weak in prPSC. In contrast to ihPSC TGF-beta activated both Smad signaling cascades in prPSC. NGF secretion was diminished by the activin-like kinase (ALK)-5 inhibitor SB431542, indicating the predominant role of ALK5 in activating the NGF system in PSC. While NGF did not affect proliferation or survival of PSC it induced expression of Inhibitor of Differentiation-1. We conclude that under conditions of upregulated TGF-beta, like fibrosis, NGF levels will also increase in PSC which might contribute to pancreatic wound healing responses.

Perineural invasion in cancer: a review of the literature

Perineural invasion (PNI) is the process of neoplastic invasion of nerves and is an under-recognized route of metastatic spread. It is emerging as an important pathologic feature of many malignancies, including those of the pancreas, colon and rectum, prostate, head and neck, biliary tract, and stomach. For many of these malignancies, PNI is a marker of poor outcome and a harbinger of decreased survival. PNI is a distinct pathologic entity that can be observed in the absence of lymphatic or vascular invasion. It can be a source of distant tumor spread well beyond the extent of any local invasion; and, for some tumors, PNI may be the sole route of metastatic spread. Despite increasing recognition of this metastatic process, there has been little progress in the understanding of molecular mechanisms behind PNI and, to date, no targeted treatment modalities aimed at this pathologic entity. The objectives of this review were to lay out a clear definition of PNI to highlight its significance in those malignancies in which it has been studied best. The authors also summarized current theories on the molecular mediators and pathogenesis of PNI and introduced current research models that are leading to advancements in the understanding of this metastatic process.

Trk kinase inhibitors as new treatments for cancer and pain

BACKGROUND

Tropomyosin-related kinases (Trks) are a family of receptor tyrosine kinases activated by neurotrophins. Trks play important roles in pain sensation as well as tumour cell growth and survival signaling. Thus, inhibitors of Trk receptor kinases might provide targeted treatments for pain and cancer.

OBJECTIVE

This paper reviews those patent applications since 2002 claiming small-molecule inhibitors of Trk receptor kinases.

METHODS

Primary literature and patents were searched with SciFinder and Google Scholar. Patents were selected based on their relevance to Trks and were evaluated and representative compounds were listed as examples.

RESULTS/CONCLUSION

Several series of Trk inhibitors with excellent in vitro potencies have been reported and a number of compounds have gone into the clinic. It should be noted that few of these inhibitors are Trk selective, demonstrating that targeting Trk kinases for treatment of pain and/or cancer offers a promising but also challenging approach.

Neurotrophin NT3 promotes ovarian primordial to primary follicle transition

Neurotrophins are growth factors that are known to have a role in promoting cell survival and differentiation. The focus of the current study is to examine the role of neurotrophins in regulating ovarian primordial follicle development. Ovaries from 4-day old rats were placed into organ culture and cultured for 10 days in the absence or presence of neurotrophin-3 (NT3), brain-derived neurotrophic factor (BDNF), or nerve growth factor (NGF). Treatment of ovaries with NT3 resulted in a significant (P<0.01) increase in primordial follicle development (i.e. primordial to primary follicle transition). Treatment with BDNF at high doses of 100-250 ng/ml also significantly (P<0.01) increased primordial follicle development, but NGF had no effect. Immunohistochemical studies determined that NT3 was present in granulosa cells, interstitial tissue, and in the oocytes of primordial and primary follicles. The NT3 receptor NTRK3 was present in oocytes at all stages of development. Analysis of ovaries that contain predominantly primordial follicles demonstrated the transcripts for NT3, NTRK3, NGF, and the BDNF/neurotrophin-4 (NT4) receptor NTRK2 are expressed, while BDNF, NT4, and the NGF receptor NTRK1 are not detectable. Inhibition of the NTRK3 receptor with the tyrphostin AG 879 resulted in oocyte death and a significant (P<0.01) reduction in follicle pool size. Inhibition of the NTRK receptors with K252a slowed primordial to primary follicle transition. A microarray analysis demonstrated that a small number of genes were differentially expressed after NT3 treatment. Observations indicate that the neurotrophin NT3, acting through the NTRK3 receptor in oocytes, promotes the primordial to primary follicle transition.

Identification and preclinical characterization of AZ-23, a novel, selective, and orally bioavailable inhibitor of the Trk kinase pathway

Tropomyosin-related kinases (TrkA, TrkB, and TrkC) are receptor tyrosine kinases that, along with their ligands, the neurotrophins, are involved in neuronal cell growth, development, and survival. The Trk-neurotrophin pathway may also play a role in tumorigenesis through oncogenic fusions, mutations, and autocrine signaling, prompting the development of novel Trk inhibitors as agents for cancer therapy. This report describes the identification of AZ-23, a novel, potent, and selective Trk kinase inhibitor. In vitro studies with AZ-23 showed improved selectivity over previous compounds and inhibition of Trk kinase activity in cells at low nanomolar concentrations. AZ-23 showed in vivo TrkA kinase inhibition and efficacy in mice following oral administration in a TrkA-driven allograft model and significant tumor growth inhibition in a Trk-expressing xenograft model of neuroblastoma. AZ-23 represents a potent and selective Trk kinase inhibitor from a novel series with the potential for use as a treatment for cancer.

Gene expression profile of prostate cancer cell lines: effect of nerve growth factor treatment

A dysregulation of the nerve growth factor (NGF)-mediated control of prostate cell growth is associated with the malignant progression of prostate epithelial cells. Exogenous NGF induced in prostate cancer (PCa) cell lines DU145 and PC3 the expression of p75(NGFR), accompanied by a reduction of the cell malignancy. The aim of this study was to analyze the profile of NGF-regulated genes the PCa cell line DU145 by using the cDNA microarray technique. NGF treatment of DU145 cells decreased the expression of 52 known genes, while the expression of 40 known genes was increased. NGF treatment of the DU145 cell line modified the expression profile of clusters of genes involved in invasion and metastasis, in cell proliferation and apoptosis, inflammation, cell metabolism and transcriptional activity. Interestingly, NGF induced the same pattern of gene modifications in both PCa cell lines. Data presented here may help to identify gene/proteins that dispose to PCa progression and to assess future markers that could allow the development of new clinic diagnostic and therapeutical approaches.

Targeting the nerve growth factor network in Alzheimer's disease

In this issue of Expert Opinion on Investigational Drugs, Papatsoris et al. describe approaches to target the nerve growth factor (NGF) network in the treatment of prostate cancer. During the progression of prostate cancer, the growth-promoting effects of NGF signaling predominate. Conversely, the pro-survival functions of NGF are compromised in Alzheimer's disease. Thus NGF-targeting agents that can selectively modulate the pathway's activity could be beneficial in both of these age-related diseases, although the goal of the modulation will be different in each setting. This editorial provides a brief overview of NGF signaling, selectively summarizes some of the recent data on its dysregulation in Alzheimer's disease and highlights efforts to develop novel pharmacologic agents for its modulation.