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PURPOSE: The use of endobronchial ultrasound (EBUS) is standard practice for lung cancer diagnosis and staging. Next generation sequencing (NGS) for detection of genetic alterations is recommended in advanced, non-squamous, non-small-cell lung cancer (NSCLC). Existing protocols for NGS testing are minimal and reported yields vary. This study aimed to determine the yield of EBUS samples obtained for NGS using a sampling protocol at our institution and assess predictive factors to form collection protocols. METHODS: We reviewed EBUS bronchoscopies from 2016 to 2021 with non-squamous NSCLC diagnoses. For target lesions suspected to be malignant, the sampling protocol was: (a) two slides for on-site evaluation, (b) three to five fine needle aspirations rinsed into saline for immunohistochemical staining and in-house molecular markers, and (c) additional three to five rinses for NGS. Sufficiency for NGS processing was determined by the pathology department. RESULTS: Two hundred and seventy-eight non-squamous NSCLC samples were obtained by EBUS (205 adenocarcinoma; 73 not otherwise specified). EBUS was performed under general anesthesia in 75.5% of cases. The overall sample adequacy for NGS testing was 57.5%. Higher adequacy rates were observed when protocol was adhered to 66.0% versus 37.2% (p < 0.001). There was no statistically significant difference based on the size of the lesion or location of the sample. CONCLUSION: When a protocol of three to five dedicated needle rinses for NGS was followed, we nearly doubled our sample adequacy rate for NSG as compared to standard care. Studies are needed to determine the ideal collection and processing modality to preserve tissue samples for genetic sequencing.
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Broncoscopía , Carcinoma de Pulmón de Células no Pequeñas , Biopsia por Aspiración con Aguja Fina Guiada por Ultrasonido Endoscópico , Secuenciación de Nucleótidos de Alto Rendimiento , Neoplasias Pulmonares , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Biopsia por Aspiración con Aguja Fina Guiada por Ultrasonido Endoscópico/métodos , Persona de Mediana Edad , Masculino , Anciano , Femenino , Broncoscopía/métodos , Estudios Retrospectivos , Anciano de 80 o más Años , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/patología , Adenocarcinoma del Pulmón/diagnóstico por imagen , Adenocarcinoma del Pulmón/diagnóstico , AdultoRESUMEN
The Percepta Genomic Sequencing Classifier (GSC) was developed to up-classify as well as down-classify the risk of malignancy for lung lesions when bronchoscopy is non-diagnostic. We evaluated the performance of Percepta GSC in risk re-classification of indeterminate lung lesions. This multicenter study included individuals who currently or formerly smoked undergoing bronchoscopy for suspected lung cancer from the AEGIS I/ II cohorts and the Percepta Registry. The classifier was measured in normal-appearing bronchial epithelium from bronchial brushings. The sensitivity, specificity, and predictive values were calculated using predefined thresholds. The ability of the classifier to decrease unnecessary invasive procedures was estimated. A set of 412 patients were included in the validation (prevalence of malignancy was 39.6%). Overall, 29% of intermediate-risk lung lesions were down-classified to low-risk with a 91.0% negative predictive value (NPV) and 12.2% of intermediate-risk lesions were up-classified to high-risk with a 65.4% positive predictive value (PPV). In addition, 54.5% of low-risk lesions were down-classified to very low risk with >99% NPV and 27.3% of high-risk lesions were up-classified to very high risk with a 91.5% PPV. If the classifier results were used in nodule management, 50% of patients with benign lesions and 29% of patients with malignant lesions undergoing additional invasive procedures could have avoided these procedures. The Percepta GSC is highly accurate as both a rule-out and rule-in test. This high accuracy of risk re-classification may lead to improved management of lung lesions.
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Broncoscopía , Neoplasias Pulmonares , Biopsia , Broncoscopía/métodos , Mapeo Cromosómico , Humanos , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/genética , Mucosa RespiratoriaRESUMEN
Background Limited data are available regarding whether computer-aided diagnosis (CAD) improves assessment of malignancy risk in indeterminate pulmonary nodules (IPNs). Purpose To evaluate the effect of an artificial intelligence-based CAD tool on clinician IPN diagnostic performance and agreement for both malignancy risk categories and management recommendations. Materials and Methods This was a retrospective multireader multicase study performed in June and July 2020 on chest CT studies of IPNs. Readers used only CT imaging data and provided an estimate of malignancy risk and a management recommendation for each case without and with CAD. The effect of CAD on average reader diagnostic performance was assessed using the Obuchowski-Rockette and Dorfman-Berbaum-Metz method to calculate estimates of area under the receiver operating characteristic curve (AUC), sensitivity, and specificity. Multirater Fleiss κ statistics were used to measure interobserver agreement for malignancy risk and management recommendations. Results A total of 300 chest CT scans of IPNs with maximal diameters of 5-30 mm (50.0% malignant) were reviewed by 12 readers (six radiologists, six pulmonologists) (patient median age, 65 years; IQR, 59-71 years; 164 [55%] men). Readers' average AUC improved from 0.82 to 0.89 with CAD (P < .001). At malignancy risk thresholds of 5% and 65%, use of CAD improved average sensitivity from 94.1% to 97.9% (P = .01) and from 52.6% to 63.1% (P < .001), respectively. Average reader specificity improved from 37.4% to 42.3% (P = .03) and from 87.3% to 89.9% (P = .05), respectively. Reader interobserver agreement improved with CAD for both the less than 5% (Fleiss κ, 0.50 vs 0.71; P < .001) and more than 65% (Fleiss κ, 0.54 vs 0.71; P < .001) malignancy risk categories. Overall reader interobserver agreement for management recommendation categories (no action, CT surveillance, diagnostic procedure) also improved with CAD (Fleiss κ, 0.44 vs 0.52; P = .001). Conclusion Use of computer-aided diagnosis improved estimation of indeterminate pulmonary nodule malignancy risk on chest CT scans and improved interobserver agreement for both risk stratification and management recommendations. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Yanagawa in this issue.
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Neoplasias Pulmonares , Nódulos Pulmonares Múltiples , Anciano , Inteligencia Artificial , Femenino , Humanos , Neoplasias Pulmonares/diagnóstico por imagen , Masculino , Nódulos Pulmonares Múltiples/diagnóstico por imagen , Estudios Retrospectivos , Sensibilidad y Especificidad , Tomografía Computarizada por Rayos X/métodosRESUMEN
The Comprehensive, Computable NanoString Diagnostic gene panel (C2Dx) is a promising solution to address the need for a molecular pathological research and diagnostic tool for precision oncology utilizing small volume tumor specimens. We translate subtyping-related gene expression patterns of Non-Small Cell Lung Cancer (NSCLC) derived from public transcriptomic data which establish a highly robust and accurate subtyping system. The C2Dx demonstrates supreme performance on the NanoString platform using microgram-level FNA samples and has excellent portability to frozen tissues and RNA-Seq transcriptomic data. This workflow shows great potential for research and the clinical practice of cancer molecular diagnosis.
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RATIONALE: Electromagnetic navigational bronchoscopy (ENB) is an important, minimally invasive diagnostic tool for malignant and benign peripheral lung lesions, offering lower complication risks than transthoracic needle aspirations. As a relatively new technology, the best sampling modality and lesion characteristics for ENB has yet to be determined. We evaluated the sensitivity and diagnostic yield of different sampling modalities (needle aspiration, brush biopsy, transbronchial forceps biopsies) and radiographical lesion characteristics by Tsuboi classification. We also evaluated the difference in yield and sensitivity with the addition of radial probe EBUS to augment ENB. METHODS: We completed a retrospective chart review of all patients that had ENB performed at our institution since its implementation in 2011. We reviewed the lesion size, location, Tsuboi classification, cytology, pathology results and analyzed biopsy specimen tool types. RESULTS: We included a total of 248 patients who had ENB performed between 2011 and 2018. Average age was 67 years and 50% female. A total of 270 lesions were targeted with a mean size of 24 ± 12 mm. Sensitivity for malignancy was 59.2% with a diagnostic yield of 72.3%. Sensitivity and diagnostic accuracy trended higher with combined sampling modalities (brush and transbronchial needle aspiration and forcep biopsy). Lesions with type I and type II Tsuboi classification of bronchus sign had higher sensitivity compared to type III classification (67.9% [n = 101 type I], 64.6% [n = 65 type II], 37.9% [n = 36 type III]), p = 0.01 and p = 0.04. CONCLUSION: For navigation bronchoscopy, sensitivity is higher in bronchus sign lesions that end directly into lesion (Tsuboi type I) and travel through malignant lesions (Tsuboi type II) compared to tangentially circumventing the lesion (Tsuboi type III).
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Bronquios/patología , Bronquios/cirugía , Broncoscopía/métodos , Fenómenos Electromagnéticos , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/patología , Pulmón/patología , Pulmón/cirugía , Cirugía Asistida por Computador/métodos , Anciano , Biopsia/métodos , Femenino , Humanos , Neoplasias Pulmonares/cirugía , Masculino , Estudios Retrospectivos , Sensibilidad y EspecificidadRESUMEN
Chemo-immunotherapy is central to the treatment of small cell lung cancer (SCLC). Despite modest progress made with the addition of immunotherapy, current cytotoxic regimens display minimal survival benefit and new treatments are needed. Thymidylate synthase (TS) is a well-validated anti-cancer drug target, but conventional TS inhibitors display limited clinical efficacy in refractory or recurrent SCLC. We performed RNA-Seq analysis to identify gene expression changes in SCLC biopsy samples to provide mechanistic insight into the potential utility of targeting pyrimidine biosynthesis to treat SCLC. We identified systematic dysregulation of pyrimidine biosynthesis, including elevated TYMS expression that likely contributes to the lack of efficacy for current TS inhibitors in SCLC. We also identified E2F1-3 upregulation in SCLC as a potential driver of TYMS expression that may contribute to tumor aggressiveness. To test if TS inhibition could be a viable strategy for SCLC treatment, we developed patient-derived organoids (PDOs) from human SCLC biopsy samples and used these to evaluate both conventional fluoropyrimidine drugs (e.g., 5-fluorouracil), platinum-based drugs, and CF10, a novel fluoropyrimidine polymer with enhanced TS inhibition activity. PDOs were relatively resistant to 5-FU and while moderately sensitive to the front-line agent cisplatin, were relatively more sensitive to CF10. Our studies demonstrate dysregulated pyrimidine biosynthesis contributes to drug resistance in SCLC and indicate that a novel approach to target these pathways may improve outcomes.
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PURPOSE/OBJECTIVES: We aimed to assess the predictive value of a lung cancer gene panel for the development of brain metastases. MATERIALS/METHODS: Between 2011 and 2015, 102 patients with lung cancer were prospectively enrolled in a clinical trial in which a diagnostic fine-needle aspirate was obtained. Gene expression was conducted on all samples that rendered a diagnosis of non-small cell lung cancer (NSCLC). Subsequent retrospective analysis of brain metastases-related outcomes was performed by reviewing patient electronic medical records. A competing risk multivariable regression was performed to estimate the adjusted hazard ratio for the development of brain metastases and non-brain metastases from NSCLC. RESULTS: A total of 49 of 102 patients had died by the last follow-up. Median time of follow-up was 13 months (range 0.23-67 months). A total of 17 patients developed brain metastases. Median survival time after diagnosis of brain metastases was 3.58 months (95% confidence interval (CI) 2.17, not available). A total of 30 patients developed metastases without any evidence of brain metastases until the time of death or last follow-up. Competing risk analysis identified three genes that were downregulated differentially in the patients with brain metastases versus non-brain metastatic disease: CD37 (0.017), cystatin A (0.022), and IL-23A (0.027). Other factors associated with brain metastases include: stage T ( P ⩽ 8.3e-6) and stage N ( P= 6.8e-4). CONCLUSIONS: We have identified three genes, CD37, cystatin A, and IL-23A, for which downregulation of gene expression was associated with a greater propensity for developing brain metastases. Validation of these biomarkers could have implications on surveillance patterns in patients with brain metastases from NSCLC.
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Antígenos de Neoplasias/metabolismo , Biomarcadores de Tumor/metabolismo , Neoplasias Encefálicas/secundario , Carcinoma de Pulmón de Células no Pequeñas/patología , Cistatina A/metabolismo , Subunidad p19 de la Interleucina-23/metabolismo , Neoplasias Pulmonares/patología , Tetraspaninas/metabolismo , Adenocarcinoma/metabolismo , Adenocarcinoma/secundario , Anciano , Neoplasias Encefálicas/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma de Células Escamosas/metabolismo , Carcinoma de Células Escamosas/secundario , Femenino , Estudios de Seguimiento , Humanos , Neoplasias Pulmonares/metabolismo , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Estudios Retrospectivos , Tasa de SupervivenciaRESUMEN
INTRODUCTION: RNA isolation from tumor tissue is used for biomarker analyses and validation. Limited diagnostic material from small volume biopsies combined with an increasing demand for standard histologic, molecular characterization, and next generation sequencing applications often leads to limited material for research. We sought to evaluate small volume sampling of lung cancer tissue collected from a single needle pass during a diagnostic procedure and determine if it can provide RNA of acceptable quantity and quality. METHODS: We enrolled 140 patients with probable primary bronchogenic carcinoma and collected RNA from a dedicated FNA aspiration. Total RNA (ηg), RNA integrity number (RIN), and %Mass in base pairs were evaluated from each patient sample. A customized nanoString nCounter® 95-gene panel was used to profile the expression patterns of feature NSCLC genes. We compared gene expression patterns that distinguish lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) in our cohort with a corresponding Cancer Genome Atlas (TCGA) NSCLC datasets. RESULTS: Of the 149 patients consented. RNA-extraction was performed in 101 eligible patients. A satisfactory total RNA mass and RIN was quantified for all samples with a similar distribution among cellular subtypes. Mean %-Mass over 300 base pairs was noted for all specimens and 96% of samples met criteria to perform genetic evaluation with our commercialized gene expression assay. The FNA-derived transcriptomic results showed excellent consistency with the TCGA counterparts, and the differential expression pattern of LUAD vs LUSC subtypes were highly similar. DISCUSSION: In this study, RNA retrieval from a single-pass FNA regardless of procedural approach showed equivalence and suitability for gene expression assessments. RNA extraction from small volume samples has the potential to provide valuable material for genetic profiling.
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Biomarcadores de Tumor/análisis , Biopsia con Aguja Fina/métodos , Carcinoma Broncogénico/diagnóstico , Neoplasias Pulmonares/diagnóstico , ARN Neoplásico/análisis , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Cohortes , Estudios de Factibilidad , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , TranscriptomaRESUMEN
OBJECTIVES: Targeted therapies for non-small-cell lung cancers (NSCLCs) are based on the presence of driver mutations such as epidermal growth factor receptor (EGFR) and the echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) translocation. Endobronchial ultrasound-guided-transbronchial needle aspiration (EBUS-TBNA) is a first-line modality for diagnosing and staging NSCLC. A quality improvement protocol maximizing tissue acquisition for molecular analysis has not been previously described. METHODS: We instituted a standardized protocol designed from a multidisciplinary meeting of the pulmonology, oncology, and pathology departments for the acquisition and on-site processing of samples obtained through EBUS-TBNA to improve the yield for genetic analysis of EGFR and ALK testing. RESULTS: Preprotocol there were 50 NSCLCs (29 adenocarcinomas) and postprotocol there were 109 NSCLCs (52 adenocarcinomas). A statistically significant increase in yield for molecular analysis was seen in both EGFR (36% preprotocol and 80% postprotocol, P < 0.01) and ALK (41% preprotocol and 80% postprotocol, P < 0.01). There was no difference in complications preprotocol and postprotocol. CONCLUSIONS: Implementation of a standardized protocol with EBUS-TBNA was associated with an increase in adequacy for molecular genetic analysis in NSCLC.
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Quinasa de Linfoma Anaplásico/genética , Carcinoma de Pulmón de Células no Pequeñas/diagnóstico , Proteínas de Ciclo Celular/genética , Biopsia por Aspiración con Aguja Fina Guiada por Ultrasonido Endoscópico , Receptores ErbB/genética , Neoplasias Pulmonares/diagnóstico , Proteínas Asociadas a Microtúbulos/genética , Serina Endopeptidasas/genética , Anciano , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Protocolos Clínicos , Femenino , Genotipo , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Translocación GenéticaRESUMEN
BACKGROUND: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) presents a minimally invasive way to evaluate abnormal mediastinal and hilar adenopathy. Although EBUS has been established as an effective modality to diagnose lung cancer, its sensitivity for the diagnosis of lymphoma has been demonstrated to be lower. Because of these lower yields uncertainty persists about the ability of EBUS-TBNA to reliably diagnose lymphoma and questions remain regarding the utility of EBUS-TBNA as a first-line biopsy modality for patients suspected of having lymphoma. METHODS: We conducted a review of our database (n=806 EBUS-TBNAs) for patients undergoing EBUS-TBNA for mediastinal and/or hilar lymphadenopathy over an 8-year span to identify patients diagnosed with lymphoma. RESULTS: Twenty patients (2.3%) who underwent EBUS-TBNA were ultimately diagnosed with lymphoma. In total, 17 of the 20 patients with lymphoma obtained a diagnosis using EBUS-TBNA. The overall sensitivity of EBUS-TBNA for lymphoma was 85%. The sensitivity for de novo diagnosis was 78% (7/9), and sensitivity for recurrence was 91% (10/11). All patients who achieved a diagnosis by EBUS-TBNA could be adequately subtyped, allowing treatment recommendations. CONCLUSION: Although the sensitivity of EBUS-TBNA for the diagnosis of lymphoma did not reach values of published data for non-small cell lung cancer, EBUS-TBNA can be considered as a first-line diagnostic tool for patients with mediastinal and/or hilar lymphadenopathy suspected to be lymphoma. Because of the inherent limitations in small volume needle biopsies it is essential that negative samples obtained in the setting of high clinical suspicion warrant further evaluation.
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Biopsia por Aspiración con Aguja Fina Guiada por Ultrasonido Endoscópico/normas , Neoplasias Pulmonares/patología , Linfoma/patología , Adulto , Anciano , Anciano de 80 o más Años , Broncoscopía/normas , Árboles de Decisión , Femenino , Humanos , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Adulto JovenAsunto(s)
Biopsia con Aguja Fina , Biopsia Guiada por Imagen , Broncoscopía , Humanos , Neoplasias PulmonaresRESUMEN
PURPOSE: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a well-established diagnostic tool for lung cancer, sarcoidosis, and suspected metastatic extrathoracic malignancy. EBUS-TBNA carries a high diagnostic yield, but its negative predictive value (NPV) requires further clarification. METHODS: We reviewed EBUS-TBNA at our cancer center from 2008 to 2015. We identified negative diagnostic samples for adenopathy suspected to represent metastatic disease from extrathoracic malignancy. RESULTS: We reviewed 529 EBUS-TBNAs. Ninety patients underwent EBUS-TBNA sampling of the hilum and/or mediastinum (121 nodes, 14 masses) for suspected extrathoracic malignancy. Thirty-seven patients had negative samples (lymph node, granulomas or non-diagnostic specimens). The overall NPV was 98 %. Granulomas (11 patients, 25 nodes) seen on histology had a 100 % NPV, including those that were FDG-PET (fluorodeoxyglucose positron emission tomography) avid (n = 14 nodes). CONCLUSION: Negative EBUS-TBNA in patients with extrathoracic malignancy and suspected secondary hilar or mediastinal metastases can infer a high NPV especially if granulomas are seen on histology. Larger prospective investigations are needed to confirm the high NPV of EBUS-TBNA with granulomas in extrathoracic malignancies.
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Granuloma/patología , Ganglios Linfáticos/patología , Linfadenopatía/patología , Neoplasias/patología , Anciano , Broncoscopía , Biopsia por Aspiración con Aguja Fina Guiada por Ultrasonido Endoscópico/métodos , Reacciones Falso Negativas , Femenino , Granuloma/diagnóstico , Humanos , Linfadenopatía/diagnóstico por imagen , Metástasis Linfática , Masculino , Mediastino , Persona de Mediana Edad , Neoplasias/diagnóstico , Valor Predictivo de las Pruebas , Estudios RetrospectivosRESUMEN
This phase II study investigated dose-intense erlotinib maintenance after dose-dense chemotherapy for patients with metastatic non-small cell lung cancer and examined two cell cycle biomarkers. Patients with newly diagnosed metastatic non-small cell lung cancer received docetaxel 75 mg/m² and cisplatin 75 mg/m² on day 1 and pegfilgrastim on day 2 every 14 days for four cycles. Patients then received erlotinib with initial doses based on smoking status. Doses were increased in 75 mg increments every two weeks depending on toxicities until each patient's maximal tolerable dose (MTD) was achieved. Cyclin D1 and D3 biomarkers were measured by immunohistochemistry. The objectives of the study were to evaluate time to progression (TTP) and overall survival (OS) for the entire population and biomarker subgroups. Forty-five patients were enrolled. Intra-patient erlotinib MTD ranged from 0 to 525 mg. Median MTD achieved in smokers was higher than in non-smokers (300 vs. 150 mg; P=0.019). TTP for the entire cohort was not significantly improved compared to historical controls. Patients with high cyclin D1 expressing tumors demonstrated improved TTP on erlotinib (8.2 vs. 4.7 months; hazard ratio, 4.1; 95% CI, 1.6-0.6; P=0.003) and improved OS (20.5 vs. 8.0 months; hazard ratio 2.8; 95% CI, 1.2-6.3; P=0.016). Intratumoral cyclin D3 expression did not impact clinical outcomes. Current smokers but not former smokers exhibit a higher erlotinib MTD. High cyclin D1 expression was associated with favorable TTP and OS.
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Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Receptores ErbB/antagonistas & inhibidores , Neoplasias Pulmonares/tratamiento farmacológico , Quinazolinas/uso terapéutico , Adulto , Anciano , Anciano de 80 o más Años , Antineoplásicos/uso terapéutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Biomarcadores de Tumor/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/mortalidad , Cisplatino/uso terapéutico , Ciclina D1/metabolismo , Ciclina D3/metabolismo , Supervivencia sin Enfermedad , Docetaxel , Esquema de Medicación , Clorhidrato de Erlotinib , Femenino , Filgrastim , Factor Estimulante de Colonias de Granulocitos/uso terapéutico , Humanos , Neoplasias Pulmonares/mortalidad , Masculino , Persona de Mediana Edad , Polietilenglicoles , Inhibidores de Proteínas Quinasas/uso terapéutico , Proteínas Recombinantes/uso terapéutico , Sobrevida , Taxoides/uso terapéutico , Resultado del TratamientoRESUMEN
CONTEXT: Beta-3 agonists acutely reduce food intake, but the mechanism is not well understood. OBJECTIVE: To evaluate the effect of a beta3 agonist on food intake in two strains of rats that differ in their sensitivity to becoming obese while eating a high-fat (HF) diet. METHODS: Male Osborne-Mendel (OM) and S5B/Pl (S5B) rats were treated with a beta3-adrenergic agonist (CL 316,243) at 8 weeks of age, after an adaptation to either an HF (56% fat energy) or a low-fat (LF; 10% fat energy) diet that was equicaloric for protein (24% energy). Ad-lib-fed rats were injected intraperitoneally with CL 316,243, at doses of 0.03, 0.1, 0.3, 1.0 or 3.0 mg/kg, or with vehicle at the beginning of the dark cycle. Food intake was measured at 1, 3, 6 and 24 h after injections. RESULTS: The beta3 agonist CL 316,243 significantly decreased food intake at all timepoints in both strains of rats eating both diets. However, this inhibition of food intake was significantly greater in the S5B rat. CL 316,243 significantly decreased serum leptin and serum glucose in both the OM and the S5B rats, and again, the inhibition was greater in the S5B rat. Whereas CL 316,243 increased serum insulin levels in the OM rat, it decreased them in the S5B rat on an LF diet. In a second experiment, chow-fed rats were implanted with vascular ports into the jugular vein and allowed to recover. When CL 316,243 was injected into the animals that were fasted overnight, rats of both strains significantly increased their serum insulin at 30 min, but the increase was much more pronounced in the S5B rat. Serum glucose was decreased significantly at both the 30- and 60-min timepoints in the OM rat and at 30 min in the S5B rat. CONCLUSION: These experiments demonstrate that a beta3 agonist (CL 316,243) has a much greater effect in a strain of rats that resist fat-induced obesity.