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Neoplasias Óseas/metabolismo , Dolor en Cáncer/metabolismo , Ácido Glutámico/metabolismo , Sistema Nervioso Periférico/metabolismo , Células Receptoras Sensoriales/metabolismo , Animales , Conducta Animal , Neoplasias Óseas/fisiopatología , Línea Celular Tumoral , Modelos Animales de Enfermedad , Femenino , Trasplante de Neoplasias , Neuronas/metabolismo , Nocicepción , Manejo del Dolor , Dimensión del Dolor , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Transducción de Señal , Sulfasalazina/farmacologíaRESUMEN
Background: Cancer pain involves nervous system damage and pathological neurogenesis. Neuropathic pain arises from damage to the nervous system and is driven by ectopic signaling. Both progesterone and pregabalin are neuroprotective in animal models, and there is evidence that both drugs bind to and inhibit voltage-gated calcium channels. Aims: This study was designed to characterize the effects of progesterone and pregabalin in preclinical models of cancer and neuropathic pain in both sexes. Methods: We measured peripheral sensory signaling by intracellular in vivo electrophysiology and behavioral indicators of pain in rat models of cancer-induced bone pain and neuropathic pain. Results: Female but not male models of cancer pain showed a behavioral response to treatment and pregabalin reduced excitability in C and A high-threshold but not low-threshold sensory neurons of both sexes. Male models of neuropathic pain treated with pregabalin demonstrated higher signaling thresholds only in A high-threshold neurons, and behavioral data indicated a clear recovery to baseline mechanical withdrawal thresholds in all treatment groups. Female rat treatment groups did not show excitability changes in sensory neurons, but all demonstrated higher mechanical withdrawal thresholds than vehicle-treated females, although not to baseline levels. Athymic female rat models of neuropathic pain showed no behavioral or electrophysiological responses to treatment. Conclusions: Both pregabalin and progesterone showed evidence of efficacy in male models of neuropathic pain. These results add to the evidence demonstrating differential effects of treatments for pain in male and female animals and widely differing responses in models of cancer and neuropathic pain.
Contexte: La douleur cancéreuse implique des lésions du système nerveux et une neurogenèse pathologique. La douleur neuropathique résulte d'une lésion du système nerveux et est provoquée par une signalisation ectopique. La progestérone et la prégabaline sont toutes deux neuroprotectrices dans les modèles animaux et il est prouvé que ces deux médicaments se lient aux canaux calciques à tension contrôlée et les inhibent.Objectifs: Cette étude visait à caractériser les effets de la progestérone et de la prégabaline dans des modèles précliniques de cancer et de douleur neuropathique chez les deux sexes.Méthodes: Nous avons mesuré la signalisation sensorielle périphérique par électrophysiologie intracellulaire in vivo, ainsi que les indicateurs comportementaux de la douleur dans des modèles de rats atteints de douleurs osseuses et de douleurs neuropathiques induites par le cancer.Résultats: Contrairement aux modèles masculins, les modèles féminins atteints de douleur cancéreuse ont montré une réponse comportementale au traitement, tandis que la prégabaline a réduit l'excitabilité des neurones sensoriels C et A à seuil élevé mais non à seuil bas chez les deux sexes. Les modèles masculins atteints de douleur neuropathique traités à la prégabaline ont montré des seuils de signalisation plus élevés uniquement dans les neurones A à seuil élevé, tandis que les données comportementales ont indiqué un net retour aux seuils de retrait mécanique de départ dans tous les groupes de traitement. Les groupes de rats femelles traités n'ont pas montré de changements d'excitabilité dans les neurones sensoriels, mais tous ont montré des seuils de retrait mécanique plus élevés que les femelles traitées avec le vecteur, sans toutefois atteindre les niveaux de départ. Les modèles atteints de douleur neuropathique parmi les rats femelles athymiques n'ont montré aucune réponse comportementale ou électrophysiologique au traitement.Conclusions: La prégabaline et la progestérone ont toutes deux démontré leur efficacité dans les modèles masculins atteints de douleur neuropathique. Ces résultats s'ajoutent aux données probantes démontrant les effets différentiels des traitements de la douleur chez les animaux mâles et femelles, et les réponses très différentes dans les modèles atteints de cancer et de douleur neuropathique.
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INTRODUCTION: Pain is a common and debilitating comorbidity of metastatic breast cancer. The hippocampus has been implicated in nociceptive processing, particularly relating to the subjective aspect of pain. Here, a syngeneic mouse model was used to characterize the effects of peripheral tumors on hippocampal microglial activation in relation to cancer-induced pain (CIP). MATERIALS AND METHODS: Mice were systemically treated with the colony-stimulating factor 1 receptor inhibitor Pexidartinib prior to intrafemoral (IF) or subcutaneous 4T1 carcinoma cell inoculation. Spontaneous and evoked nociceptive responses were quantitated throughout tumor development, and contralateral hippocampi were collected via endpoint microdissection for RNA analysis. Additionally, IF tumor-bearing animals were sacrificed on days 5, 10, 15, and 20 post 4T1 cell inoculation, and brain sections were immunofluorescently stained for Iba1, a marker of activated microglia. RESULTS: Ablation of these neuroimmune cells with the CSF1R inhibitor Pexidartinib delayed the onset and severity of cancer-induced nociceptive behaviors in IF tumor-bearing animals, adding to the body of literature that demonstrates microglial contribution to the development and maintenance of CIP. Furthermore, in untreated IF tumor-bearing mice, nociceptive behaviors appeared to progress in parallel with microglial activation in hippocampal regions. Immunofluorescent Iba1+ microglia increased in the dentate gyrus and cornu ammonis 1 hippocampal regions in IF tumor-bearing animals over time, which was confirmed at the mRNA level using relevant microglial markers. CONCLUSION: This is the first experimental evidence to demonstrate the effects of peripheral tumor-induced nociception on hippocampal microglial activation. The increase in hippocampal microglia observed in the present study may reflect the emotional and cognitive deficits reported by patients with CIP.
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Cancers in the bone produce a number of severe symptoms including pain that compromises patient functional status, quality of life, and survival. The source of this pain is multifaceted and includes factors secreted from tumor cells. Malignant cells release the neurotransmitter and cell-signaling molecule glutamate via the oxidative stress-related cystine/glutamate antiporter, system xC-, which reciprocally imports cystine for synthesis of glutathione and the cystine/cysteine redox cycle. Pharmacological inhibition of system xC- has shown success in reducing and delaying the onset of cancer pain-related behavior in mouse models. This investigation describes the development of a stable siRNA-induced knockdown of the functional trans-membrane system xC- subunit xCT ( SLC7A11) in the human breast cancer cell line MDA-MB-231. Clones were verified for xCT knockdown at the transcript, protein, and functional levels. RNAseq was performed on a representative clone to comprehensively examine the transcriptional cellular signature in response to xCT knockdown, identifying multiple differentially regulated factors relevant to cancer pain including nerve growth factor, interleukin-1, and colony-stimulating factor-1. Mice were inoculated intrafemorally and recordings of pain-related behaviors including weight bearing, mechanical withdrawal, and limb use were performed. Animals implanted with xCT knockdown cancer cells displayed a delay until the onset of nociceptive behaviors relative to control cells. These results add to the body of evidence suggesting that a reduction in glutamate release from cancers in bone by inhibition of the system xC- transporter may decrease the severe and intractable pain associated with bone metastases.
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Sistema de Transporte de Aminoácidos y+/metabolismo , Neoplasias de la Mama/complicaciones , Dolor en Cáncer/etiología , Dolor en Cáncer/genética , Regulación Neoplásica de la Expresión Génica/fisiología , Sistema de Transporte de Aminoácidos y+/genética , Animales , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Isótopos de Carbono/farmacocinética , Carnitina O-Palmitoiltransferasa/genética , Carnitina O-Palmitoiltransferasa/metabolismo , Línea Celular Tumoral , Cistina/farmacocinética , Modelos Animales de Enfermedad , Femenino , Ácido Glutámico/metabolismo , Glutatión/metabolismo , Humanos , Interleucina-1/metabolismo , Factor Estimulante de Colonias de Macrófagos/genética , Factor Estimulante de Colonias de Macrófagos/metabolismo , Ratones Endogámicos BALB C , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Factor de Crecimiento Nervioso/genética , Factor de Crecimiento Nervioso/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismoRESUMEN
Aggressive breast cancer subtypes utilize system xc-, a membrane antiporter, to import cystine for glutathione synthesis and maintenance of redox homeostasis, in turn releasing glutamate as a metabolic pro-nociceptive by-product. Metastatic breast cancers establish themselves at distal sites including bone, where changes in extracellular glutamate levels contribute to cancer-induced bone pain. We previously established that stearically blocking system xc- activity with sulfasalazine delays the onset of nociceptive behaviours and that xCT, the functional antiporter subunit, is positively regulated by signal transducer and activator of transcription 3 (STAT3). In the current investigation, a murine xenograft cancer-induced bone pain model was applied to examine whether pharmacological inhibition of phosphorylated STAT3 (pSTAT3) induces changes in nociception. A high glutamate-releasing, xCT/pSTAT3 over-expressing human breast cancer cell line was selected for injection into the distal epiphysis of the right femur of female nude mice. A 14-day regimen of intraperitoneal injections with either vehicle or the novel STAT3 inhibitor DR-1-55 commenced three weeks after initial intrafemoral bone injection. Nociceptive behaviours were temporally monitored by automated von Frey, dynamic weight bearing and open-field testing for the duration of the study, beginning at the baseline. Prior to sacrifice and at ethical end point, tumour-induced osteolytic lesions were radiographically assessed. Treatment with DR-1-55 significantly delayed the onset and severity of spontaneous and induced nociceptive behaviours, also decreasing human SLC7A11 ( xCT) mRNA levels in tumour-bearing limbs without altering osteolysis. In addition, two pro-inflammatory cytokines released by this cell line, interleukin 6 and interleukin 1ß, were also down-regulated at the mRNA level in response to DR-1-55 treatment in vivo, with lower human interleukin 6 levels detected in the host circulation. This study demonstrates that targeting pSTAT3 may be a viable therapeutic means to manage cancer-induced bone pain, alone or in combination with stearic system xc- blockers.
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Huesos/patología , Dolor en Cáncer/metabolismo , Regulación Neoplásica de la Expresión Génica/fisiología , Nocicepción/fisiología , Factor de Transcripción STAT3/metabolismo , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias Óseas/complicaciones , Neoplasias Óseas/tratamiento farmacológico , Neoplasias de la Mama/complicaciones , Dolor en Cáncer/etiología , Dolor en Cáncer/terapia , Carcinoma/complicaciones , Línea Celular Tumoral/patología , Citocinas/sangre , Citocinas/genética , Modelos Animales de Enfermedad , Conducta Exploratoria/efectos de los fármacos , Conducta Exploratoria/fisiología , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/etiología , Masculino , Ratones , Ratones Desnudos , Nocicepción/efectos de los fármacos , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Transcripción STAT3/genética , Soporte de Peso/fisiología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Evidence suggests that there are both nociceptive and neuropathic components of cancer-induced pain. We have observed that changes in intrinsic membrane properties and excitability of normally non-nociceptive Aß sensory neurons are consistent in rat models of peripheral neuropathic pain and cancer-induced pain. This has prompted a comparative investigation of the intracellular electrophysiological characteristics of sensory neurons and of the ultrastructural morphology of the dorsal horn in rat models of neuropathic pain and cancer-induced pain. Neuropathic pain model rats were induced with a polyethylene cuff implanted around a sciatic nerve. Cancer-induced pain model rats were induced with mammary rat metastasis tumour-1 rat breast cancer or MATLyLu rat prostate cancer cells implanted into the distal epiphysis of a femur. Behavioural evidence of nociception was detected using von Frey tactile assessment. Aß-fibre low threshold mechanoreceptor neurons in both cancer-induced pain and neuropathic pain models exhibited slower dynamics of action potential genesis, including a wider action potential duration and lower action potential amplitude compared to those in control animals. Enhanced excitability of Aß-fibre low threshold mechanoreceptor neurons was also observed in cancer-induced pain and neuropathic pain models. Furthermore, both cancer-induced pain and neuropathic pain models showed abundant abnormal axonal sprouting in bundles of myelinated axons in the ipsilateral spinal laminae IV and V. The patterns of changes show consistency between rat models of cancer-induced pain and neuropathic pain. These findings add to the body of evidence that animal models of cancer-induced pain and neuropathic pain share features that may contribute to the peripheral and central sensitization and tactile hypersensitivity in both pain states.
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Dolor en Cáncer/fisiopatología , Ganglios Espinales/fisiopatología , Neuralgia/fisiopatología , Plasticidad Neuronal/fisiología , Médula Espinal/fisiopatología , Potenciales de Acción/fisiología , Animales , Dolor en Cáncer/patología , Ganglios Espinales/patología , Hiperalgesia/fisiopatología , Neuralgia/patología , Umbral del Dolor/fisiología , Ratas Sprague-Dawley , Células Receptoras Sensoriales/fisiologíaRESUMEN
Breast cancer cells release the signalling molecule glutamate via the system xC- antiporter, which is upregulated to exchange extracellular cystine for intracellular glutamate to protect against oxidative stress. Here, we demonstrate that this antiporter is functionally influenced by the actions of the neurotrophin nerve growth factor on its cognate receptor tyrosine kinase, TrkA, and that inhibiting this complex may reduce cancer-induced bone pain via its downstream actions on xCT, the functional subunit of system xC-. We have characterized the effects of the selective TrkA inhibitor AG879 on system xC- activity in murine 4T1 and human MDA-MB-231 mammary carcinoma cells, as well as its effects on nociception in our validated immunocompetent mouse model of cancer-induced bone pain, in which BALB/c mice are intrafemorally inoculated with 4T1 murine carcinoma cells. AG879 decreased functional system xC- activity, as measured by cystine uptake and glutamate release, and inhibited nociceptive and physiologically relevant responses in tumour-bearing animals. Cumulatively, these data suggest that the activation of TrkA by nerve growth factor may have functional implications on system xC--mediated cancer pain. System xC--mediated TrkA activation therefore presents a promising target for therapeutic intervention in cancer pain treatment.
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Sistema de Transporte de Aminoácidos y+/metabolismo , Neoplasias Óseas/complicaciones , Dolor en Cáncer/etiología , Dolor en Cáncer/metabolismo , Ácido Glutámico/metabolismo , Receptor trkA/antagonistas & inhibidores , Sistema de Transporte de Aminoácidos y+/genética , Animales , Conducta Animal , Recuento de Células , Línea Celular Tumoral , Femenino , Fémur/patología , Humanos , Ratones Endogámicos BALB C , Modelos Biológicos , Factor de Crecimiento Nervioso/farmacología , Nocicepción/efectos de los fármacos , Osteólisis/metabolismo , Osteólisis/patología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Receptor trkA/metabolismo , Tirfostinos/farmacologíaRESUMEN
The aim of this work was to synthesize and evaluate [2 + 1] 99mTc(i) polypyridine complexes containing tetrazines, which along with the corresponding Re(i) complexes, represent a new class of isostructural nuclear and turn-on luminescent probes that can be derivatized and targeted using bioorthogonal chemistry. To this end, [2 + 1] complexes of 99mTc(i) of the type [99mTc(CO)3(N^N)(L)] (N^N = bathophenanthroline disulfonate (BPS) or 2,2'-bipyridine (bipy)), where the monodentate ligand (L) was a tetrazine linked to the metal through an imidazole derivative, were prepared. The desired products were obtained in nearly quantitative radiochemical yield by adding [99mTc(CO)3(N^N)(OH2)]n to the imidazole-tetrazine ligand and heating at 60 °C for 30 min. Measurement of the reaction kinetics between the tetrazine and (E)-cyclooct-4-enol revealed a second-order rate constant of 8.6 × 103 M-1 s-1 at 37 °C, which is suitable for in vivo applications that require rapid coupling. Stability studies showed that the metal complexes were resistant to ligand challenge and exhibited reasonable protein binding in vitro. Biodistribution studies of the more water-soluble BPS derivative in normal mice, one hour after administration of a bisphosphonate derivative of trans-cyclooctene (TCO-BP), revealed high activity concentrations in the knee (9.3 ± 0.3 %ID g-1) and shoulder (5.3 ± 0.7 %ID g-1). Using the same pretargeting approach, SPECT/CT imaging showed that the [2 + 1] tetrazine complex localized to implanted skeletal tumors. This is the first report of the preparation of 99mTc complexes of BPS and demonstration that their tetrazine derivatives can be used to prepare targeted imaging probes by employing bioorthogonal chemistry.
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Compuestos de Organotecnecio/química , Radioquímica/métodos , Transporte de Electrón , Compuestos de Organotecnecio/farmacocinética , Distribución Tisular , Tomografía Computarizada de Emisión de Fotón ÚnicoRESUMEN
Despite the lack of robust evidence of effectiveness, current treatment options for cancer-induced depression (CID) are limited to those developed for non-cancer related depression. Here, anhedonia-like and coping behaviours were assessed in female BALB/c mice inoculated with 4T1 mammary carcinoma cells. The behavioural effects of orally administered sulfasalazine (SSZ), a system xc- inhibitor, were compared with fluoxetine (FLX). FLX and SSZ prevented the development of anhedonia-like behaviour on the sucrose preference test (SPT) and passive coping behaviour on the forced swim test (FST). The SSZ metabolites 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP) exerted an effect on the SPT but not on the FST. Although 5-ASA is a known anti-inflammatory agent, neither treatment with SSZ nor 5-ASA/SP prevented tumour-induced increases in serum levels of interleukin-1ß (IL-1ß) and IL-6, which are indicated in depressive disorders. Thus, the observed antidepressant-like effect of SSZ may primarily be attributable to the intact form of the drug, which inhibits system xc-. This study represents the first attempt at targeting cancer cells as a therapeutic strategy for CID, rather than targeting downstream effects of tumour burden on the central nervous system. In doing so, we have also begun to characterize the molecular pathways of CID.
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Conducta Animal , Depresión/tratamiento farmacológico , Depresión/etiología , Ácido Glutámico/metabolismo , Neoplasias/complicaciones , Neoplasias/metabolismo , Sulfasalazina/uso terapéutico , Sistema de Transporte de Aminoácidos y+/metabolismo , Animales , Neoplasias Encefálicas/secundario , Línea Celular Tumoral , Cistina/metabolismo , Citocinas/biosíntesis , Depresión/sangre , Femenino , Ácido Glutámico/sangre , Ratones Endogámicos BALB C , Neoplasias/sangre , Análisis de Regresión , Sulfasalazina/farmacologíaRESUMEN
INTRODUCTION: Clinical data on cancer-induced bone pain (CIBP) suggest extensive changes in sensory function. In a previous investigation of an animal model of CIBP, we have observed that changes in intrinsic membrane properties and excitability of dorsal root ganglion (DRG) nociceptive neurons correspond to mechanical allodynia and hyperalgesia. OBJECTIVES: To investigate the mechanisms underlying changes in nonnociceptive sensory neurons in this model, we have compared the electrophysiological properties of primary nonnociceptive sensory neurons at <1 and >2 weeks after CIBP model induction with properties in sham control animals. METHODS: Copenhagen rats were injected with 106 MAT-LyLu rat prostate cancer cells into the distal femur epiphysis to generate a model of CIBP. After von Frey tactile measurement of mechanical withdrawal thresholds, the animals were prepared for acute electrophysiological recordings of mechanically sensitive neurons in the DRG in vivo. RESULTS: The mechanical withdrawal threshold progressively decreased in CIBP model rats. At <1 week after model induction, there were no changes observed in nonnociceptive Aß-fiber DRG neurons between CIBP model rats and sham rats. However, at >2 weeks, the Aß-fiber low-threshold mechanoreceptors (LTMs) in CIBP model rats exhibited a slowing of the dynamics of action potential (AP) genesis, including wider AP duration and lower AP amplitude compared with sham rats. Furthermore, enhanced excitability of Aß-fiber LTM neurons was observed as an excitatory discharge in response to intracellular injection of depolarizing current into the soma. CONCLUSION: After induction of the CIBP model, Aß-fiber LTMs at >2 weeks but not <1 week had undergone changes in electrophysiological properties. Importantly, changes observed are consistent with observations in models of peripheral neuropathy. Thus, Aß-fiber nonnociceptive primary sensory neurons might be involved in the peripheral sensitization and tumor-induced tactile hypersensitivity in CIBP.
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Pharmacologically targeting activated STAT3 and/or STAT5 has been an active area of cancer research. The cystine/glutamate antiporter, system xc-, contributes to redox balance and export of intracellularly produced glutamate in response to up-regulated glutaminolysis in cancer cells. We have previously shown that blocking STAT3/5 using the small molecule inhibitor, SH-4-54, which targets the SH2 domains of both proteins, increases xCT expression, thereby increasing system xc- activity in human breast cancer cells. The current investigation demonstrates that chronic SH-4-54 administration, followed by clonal selection of treatment-resistant MDA-MB-231 and T47D breast cancer cells, elicits distinct subtype-dependent effects. xCT mRNA and protein levels, glutamate release, and cystine uptake are decreased relative to untreated passage-matched controls in triple-negative MDA-MB-231 cells, with the inverse occurring in estrogen-responsive T47D cells. This "ying-yang" effect is linked with a shifted balance between the phosphorylation status of STAT3 and STAT5, intracellular ROS levels, and STAT5 SUMOylation/de-SUMOylation. STAT5 emerged as a definitive negative regulator of xCT at the transcriptional level, while STAT3 activation is coupled with increased system xc- activity. We propose that careful classification of a patient's breast cancer subtype is central to effectively targeting STAT3/5 as a therapeutic means of treating breast cancer, particularly given that xCT is emerging as an important biomarker of aggressive cancers.
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Sistema de Transporte de Aminoácidos y+/metabolismo , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Especies Reactivas de Oxígeno/metabolismo , Factor de Transcripción STAT3/metabolismo , Factor de Transcripción STAT5/metabolismo , Proteínas Modificadoras Pequeñas Relacionadas con Ubiquitina/metabolismo , Animales , Apoptosis , Western Blotting , Neoplasias de la Mama/tratamiento farmacológico , Proliferación Celular , Resistencia a Antineoplásicos , Femenino , Humanos , Técnicas para Inmunoenzimas , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Oxidación-Reducción , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción STAT3/genética , Factor de Transcripción STAT5/genética , Proteínas Modificadoras Pequeñas Relacionadas con Ubiquitina/genética , Sumoilación , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
BACKGROUND: Bone cancer pain is often severe, yet little is known about mechanisms generating this type of chronic pain. While previous studies have identified functional alterations in peripheral sensory neurons that correlate with bone tumours, none has provided direct evidence correlating behavioural nociceptive responses with properties of sensory neurons in an intact bone cancer model. RESULTS: In a rat model of prostate cancer-induced bone pain, we confirmed tactile hypersensitivity using the von Frey test. Subsequently, we recorded intracellularly from dorsal root ganglion neurons in vivo in anesthetized animals. Neurons remained connected to their peripheral receptive terminals and were classified on the basis of action potential properties, responses to dorsal root stimulation, and to mechanical stimulation of the respective peripheral receptive fields. Neurons included C-, Aδ-, and Aß-fibre nociceptors, identified by their expression of substance P. We suggest that bone tumour may induce phenotypic changes in peripheral nociceptors and that these could contribute to bone cancer pain. CONCLUSIONS: This work represents a significant technical and conceptual advance in the study of peripheral nociceptor functions in the development of cancer-induced bone pain. This is the first study to report that changes in sensitivity and excitability of dorsal root ganglion primary afferents directly correspond to mechanical allodynia and hyperalgesia behaviours following prostate cancer cell injection into the femur of rats. Furthermore, our unique combination of techniques has allowed us to follow, in a single neuron, mechanical pain-related behaviours, electrophysiological changes in action potential properties, and dorsal root substance P expression. These data provide a more complete understanding of this unique pain state at the cellular level that may allow for future development of mechanism-based treatments for cancer-induced bone pain.
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Neoplasias Óseas/patología , Dolor en Cáncer/patología , Dolor en Cáncer/fisiopatología , Fenómenos Electrofisiológicos , Nociceptores/patología , Potenciales de Acción , Animales , Neoplasias Óseas/complicaciones , Modelos Animales de Enfermedad , Ganglios Espinales/patología , Masculino , Modelos Neurológicos , Fibras Nerviosas/patología , Conducción Nerviosa , Osteólisis/complicaciones , Osteólisis/patología , Umbral del Dolor , Ratas , Factores de TiempoRESUMEN
Glutamate is an important signaling molecule in a wide variety of tissues. Aberrant glutamatergic signaling disrupts normal tissue homeostasis and induces several disruptive pathological conditions including pain. Breast cancer cells secrete high levels of glutamate and often metastasize to bone. Exogenous glutamate can disrupt normal bone turnover and may be responsible for cancer-induced bone pain (CIBP). CIBP is a significant co-morbidity that affects quality of life for many advanced-stage breast cancer patients. Current treatment options are commonly accompanied by serious side-effects that negatively impact patient care. Identifying small molecule inhibitors of glutamate release from aggressive breast cancer cells advances a novel, mechanistic approach to targeting CIBP that could advance treatment for several pathological conditions. Using high-throughput screening, we investigated the ability of approximately 30,000 compounds from the Canadian Compound Collection to reduce glutamate release from MDA-MB-231 breast cancer cells. This line is known to secrete high levels of glutamate and has been demonstrated to induce CIBP by this mechanism. Positive chemical hits were based on the potency of each molecule relative to a known pharmacological inhibitor of glutamate release, sulfasalazine. Efficacy was confirmed and drug-like molecules were identified as potent inhibitors of glutamate secretion from MDA-MB-231, MCF-7 and Mat-Ly-Lu cells.
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Neoplasias de la Mama/metabolismo , Ácido Glutámico/metabolismo , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/farmacología , Huesos/efectos de los fármacos , Huesos/metabolismo , Neoplasias de la Mama/complicaciones , Capsaicina/análogos & derivados , Capsaicina/farmacología , Línea Celular Tumoral , Agonistas de Dopamina/farmacología , Descubrimiento de Drogas , Femenino , Ensayos Analíticos de Alto Rendimiento , Humanos , Concentración 50 Inhibidora , Dolor/tratamiento farmacológico , Dolor/etiología , Dolor/metabolismo , Transducción de Señal/efectos de los fármacos , Bibliotecas de Moléculas PequeñasRESUMEN
Cancer in bone is frequently a result of metastases from distant sites, particularly from the breast, lung, and prostate. Pain is a common and often severe pathological feature of cancers in bone, and is a significant impediment to the maintenance of quality of life of patients living with bone metastases. Cancer cell lines have been demonstrated to release significant amounts of the neurotransmitter and cell-signalling molecule l-glutamate via the system xC(-) cystine/glutamate antiporter. We have developed a novel mouse model of breast cancer bone metastases to investigate the impact of inhibiting cancer cell glutamate transporters on nociceptive behaviour. Immunodeficient mice were inoculated intrafemorally with the human breast adenocarcinoma cell line MDA-MB-231, then treated 14days later via mini-osmotic pumps inserted intraperitoneally with sulfasalazine, (S)-4-carboxyphenylglycine, or vehicle. Both sulfasalazine and (S)-4-carboxyphenylglycine attenuated in vitro cancer cell glutamate release in a dose-dependent manner via the system xC(-) transporter. Animals treated with sulfasalazine displayed reduced nociceptive behaviours and an extended time until the onset of behavioural evidence of pain. Animals treated with a lower dose of (S)-4-carboxyphenylglycine did not display this reduction in nociceptive behaviour. These results suggest that a reduction in glutamate secretion from cancers in bone with the system xC(-) inhibitor sulfasalazine may provide some benefit for treating the often severe and intractable pain associated with bone metastases.
Asunto(s)
Antiinflamatorios no Esteroideos/uso terapéutico , Huesos/fisiopatología , Ácido Glutámico/metabolismo , Dolor/tratamiento farmacológico , Sulfasalazina/uso terapéutico , Adenocarcinoma/complicaciones , Adenocarcinoma/metabolismo , Animales , Antiinflamatorios no Esteroideos/farmacología , Benzoatos/uso terapéutico , Neoplasias de la Mama/complicaciones , Neoplasias de la Mama/metabolismo , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Glicina/análogos & derivados , Glicina/uso terapéutico , Humanos , Ratones , Ratones Desnudos , Dolor/etiología , Dolor/patología , Dimensión del Dolor , Sulfasalazina/farmacología , Análisis de Supervivencia , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Breast cancers are the most common source of metastases to bone, of which cancer-induced bone pain is a frequent pathological feature. Cancer-induced bone pain is a unique pain state with multiple determinants that remains to be well understood and managed. Current standard treatments are limited by dose-dependent side effects that can reduce the quality of life of patients. Glutamate is a neurotransmitter and bone cell-signalling molecule that is released via the system x(c)(-) cystine/glutamate antiporter from cancer cell types that frequently metastasize to bone, including breast cancers. In cancer cells, glutamate release is understood to be a side effect of the cellular response to oxidative stress that upregulates the expression and activity of system x(c)(-) to promote the increased import of cystine. Attenuation of glutamate release from cancer cells has been demonstrated to result in reductions in associated cancer-induced bone pain in animal models. This review examines the clinical implications of attenuating cystine uptake and glutamate release in the treatment of cancer-induced bone pain.