RESUMEN
Nodular pulmonary amyloidosis, a subtype of pulmonary amyloidosis, is a unique disease that can mimic lung cancer on radiographic imaging and is related to lymphoproliferative disorders. In this report, we describe a case of a 76-year-old male who presented with a solitary nodule in his left lower lung lobe on computed tomography that increased from 6 mm to 13 mm in diameter over 40 months. Lung cancer was suspected; however, transbronchial lung biopsy revealed deposition of an eosinophilic and homogeneous amorphous substance, which showed apple-green birefringence under polarized light after Congo red staining, and immunohistochemistry analysis returned positive results for immunoglobulin lambda light-chain. Upper gastrointestinal endoscopy revealed a gastric mucosa-associated lymphoid tissue (MALT) lymphoma. These findings indicated that this was a case of nodular pulmonary amyloidosis that preceded a diagnosis of MALT lymphoma.
Asunto(s)
Amiloidosis , Neoplasias Pulmonares , Linfoma de Células B de la Zona Marginal , Masculino , Humanos , Anciano , Linfoma de Células B de la Zona Marginal/diagnóstico por imagen , Neoplasias Pulmonares/diagnóstico por imagen , Amiloidosis/diagnóstico , Amiloidosis/etiología , Pulmón/diagnóstico por imagenRESUMEN
We report a case of retroperitoneal hematoma during prophylactic heparin therapy for coronavirus disease 2019 (COVID-19). A 79-year-old man was diagnosed with COVID-19 pneumonia with possible exacerbation of fibrotic hypersensitivity pneumonia. He received a prophylactic dose of subcutaneous heparin therapy, methylprednisolone pulse therapy and Intravenous remdesivir but developed a spontaneous iliopsoas muscle hematoma, and transcatheter arterial embolization was performed. Even with a prophylactic dose of subcutaneous heparin therapy, the course should be carefully monitored, especially in patients with preexisting risk factors for hemorrhagic complications. Once retroperitoneal hematoma develops, aggressive procedures, such as transcatheter arterial embolization, should be considered to avoid fatal outcomes.
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COVID-19 , Masculino , Humanos , Anciano , Anticoagulantes/efectos adversos , Heparina/efectos adversos , Hematoma/inducido químicamente , Hematoma/tratamiento farmacológico , Hemorragia GastrointestinalRESUMEN
Colonization of surfaces in the human body by microorganisms is an early, essential, step in the initiation of infectious disease. We have developed in vitro assays to investigate interactions between yeast or bacterial cells and human tissues, fluids, or prostheses. Such assays can be used to identify the adhesins, ligands, and receptors involved in these interactions, for example, by determining which components of the microbe or human tissue/fluid interfere with adherence in the assay. The assays can also be applied to find ways of preventing adhesion, and subsequent disease, by investigating the effects of different conditions and added compounds on adherence in the in vitro assays. Here we describe assays for measuring adhesion of the oral yeast Candida albicans, a common commensal and opportunistic pathogen, or the bacterium Staphylococcus epidermidis, which is not normally pathogenic but is known to form biofilms on medical prostheses. The assays described belong to two approaches to investigating adhesion and biofilm formation: (i) retention at a fixed time point following liquid washes, and (ii) retention against a continuous flow of medium.
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Candida albicans , Levaduras , Humanos , Biopelículas , Staphylococcus epidermidis , Adhesinas BacterianasRESUMEN
While palliative care for patients with cancer is actively performed, it is provided only occasionally for patients with chronic non-cancerous respiratory diseases. This is due to various factors, including the fact that palliative care is not covered by health insurance and the difficulty in determining end-of-life in these patients. This paper presents two case studies to highlight the significance of palliative care team intervention for patients in the terminal stage of chronic non-cancerous respiratory diseases. Palliative care is essential to support physical problems, such as dyspnea, as well as mental disorders, such as depression, and to provide nutrition therapy and rehabilitation. To achieve care at the appropriate time in accordance with the patient's wishes, it is essential for patients to understand and accept the progress and deterioration of their disease and prepare for the end of life at an earlier stage under multidisciplinary involvement (advance care planning).
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Neoplasias , Cuidados Paliativos , Humanos , Muerte , Neoplasias/terapiaRESUMEN
OBJECTIVES: To analyse the clinical characteristics and prognosis of acute exacerbation (AE) in patients with idiopathic pulmonary fibrosis (IPF) and pulmonary emphysema. DESIGN: A multicentre retrospective cohort study SETTING: Two university hospitals in Japan PARTICIPANTS: Patients admitted to hospitals due to AE of IPF diagnosed based on a multidisciplinary discussion. INTERVENTIONS: None PRIMARY AND SECONDARY OUTCOME MEASURES: 90-day mortality rate METHODS: We retrospectively analysed consecutive patients with AE of IPF, with or without pulmonary emphysema, admitted to two university hospitals between 2007 and 2018. RESULTS: Among 62 patients (median age, 75 years; 48 men) admitted for AE of IPF, 29 patients (46%) presented with concomitant pulmonary emphysema. There was no significant difference in the arterial partial oxygen pressure/fraction of inhaled oxygen (P/F) ratio or other laboratory and radiographic data between patients with and without emphysema. The 90-day mortality rate was significantly lower in patients with emphysema than in those with IPF alone (23% vs 52%, p=0.03). The median survival time was significantly longer in patients with emphysema than in those with IPF alone (405 vs 242 days, p=0.02). CONCLUSION: Patients with IPF and emphysema had better short-term survival after AE than those with non-emphysematous IPF.
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Fibrosis Pulmonar Idiopática , Enfisema Pulmonar , Anciano , Estudios de Cohortes , Humanos , Fibrosis Pulmonar Idiopática/complicaciones , Japón , Masculino , Oxígeno , Pronóstico , Enfisema Pulmonar/complicaciones , Estudios RetrospectivosRESUMEN
OBJECTIVE: Post-bronchoscopy pneumonia can affect the prognosis of lung cancer patients. This prospective study examined the efficacy of prophylactic antibiotics for lung cancer patients at high-risk of post-bronchoscopy pneumonia, determined by our prediction score, using three risk factors: age 70 years or older, current smoking, and central tumors visualized on CT. METHODS: Patients with lung cancer who underwent diagnostic bronchoscopy between June 2018 and March 2020 with a score of 2 points or higher were enrolled. Sulbactam/ampicillin was administered intravenously within one hour prior to bronchoscopy, followed by oral clavulanate/amoxicillin for three days. We used the data of lung cancer patients who underwent diagnostic bronchoscopy between April 2012 and July 2014 and exhibited a score of 2 or higher as the historical control. RESULTS: Post-bronchoscopy pneumonia occurred in none of the 24 patients in the prophylaxis group and in 17 of 144 patients in the control group, with no significant difference in the incidence of pneumonia between the two groups. CONCLUSIONS: Antibiotic prophylaxis can be effective and safe for the patients high-risk of post-bronchoscopy pneumonia. A multicenter prospective study to examine the effects of prophylactic antibiotics in high-risk patients is feasible with a modest number of participants.
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Neoplasias Pulmonares , Neumonía , Anciano , Antibacterianos/uso terapéutico , Broncoscopía/efectos adversos , Humanos , Neoplasias Pulmonares/complicaciones , Neumonía/etiología , Neumonía/prevención & control , Estudios ProspectivosRESUMEN
An 82-year-old woman with a history of chronic thromboembolic pulmonary hypertension (CTEPH) presented with malaise, left facial nerve paralysis and the positive seroconversion of myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA). She was diagnosed with ANCA-associated vasculitis (AAV). Administration of corticosteroids significantly improved her symptoms, with a decline in the serum MPOANCA level. Ten months later than the initial presentation, she developed an AAV exacerbation with lung infiltration and pericardial effusion, which improved with high-dose corticosteroid therapy. To date, a limited number of AAV cases concomitant with pulmonary hypertension have been reported. The case report presented herein suggests a potential role for CTEPH in the development of AAV.
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Vasculitis Asociada a Anticuerpos Citoplasmáticos Antineutrófilos , Hipertensión Pulmonar , Anciano de 80 o más Años , Vasculitis Asociada a Anticuerpos Citoplasmáticos Antineutrófilos/complicaciones , Anticuerpos Anticitoplasma de Neutrófilos , Femenino , Humanos , Hipertensión Pulmonar/tratamiento farmacológico , Hipertensión Pulmonar/etiologíaRESUMEN
Cryptogenic bilateral fibrosing pleuritis is a rare condition, and its pathogenesis and clinical course are poorly understood, with no established therapy available. A 61-year-old man presented with bilateral pleural thickening and lymphocytic exudative effusions. The patient was diagnosed with fibrosing pleuritis with no evidence of a known etiology on a surgical pleural biopsy. Within 16 months from the onset of respiratory symptoms, restrictive ventilatory impairment progressed rapidly, resulting in hypercapnic respiratory failure requiring home oxygen and non-invasive positive pressure ventilation therapies.
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Derrame Pleural , Pleuresia , Insuficiencia Respiratoria , Biopsia/efectos adversos , Fibrosis , Humanos , Masculino , Persona de Mediana Edad , Pleura/patología , Derrame Pleural/etiología , Pleuresia/complicaciones , Pleuresia/diagnóstico , Insuficiencia Respiratoria/complicaciones , Insuficiencia Respiratoria/terapiaRESUMEN
Unilateral absence of the pulmonary artery (UAPA) with or without other anomalies in the heart is a rare congenital malformation. A 55-year-old Filipino woman without a remarkable medical history was admitted to our hospital for hemoptysis. Contrast-enhanced chest computed tomography revealed the absence of the left pulmonary artery. Echocardiography and right heart catheterization showed no cardiac malformations or pulmonary hypertension. We diagnosed her with isolated left-sided UAPA and performed transarterial embolization of the left inferior phrenic artery. This resolved the hemoptysis, and there was no recurrence during the four-year follow-up period.
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Embolización Terapéutica , Cardiopatías Congénitas , Enfermedades Pulmonares , Malformaciones Vasculares , Femenino , Hemoptisis/etiología , Hemoptisis/terapia , Humanos , Pulmón/irrigación sanguínea , Enfermedades Pulmonares/terapia , Persona de Mediana Edad , Pronóstico , Arteria Pulmonar/anomalías , Arteria Pulmonar/diagnóstico por imagenRESUMEN
Overexpression of ATP-binding cassette (ABC) transporters is a major cause of drug resistance in fungal pathogens. Milbemycins, enniatin B, beauvericin, and FK506 are promising leads for broad-spectrum fungal multidrug efflux pump inhibitors. The characterization of naturally generated inhibitor-resistant mutants is a powerful tool to elucidate structure-activity relationships in ABC transporters. We isolated 20 Saccharomyces cerevisiae mutants overexpressing Candida albicans ABC pump Cdr1 variants resistant to fluconazole efflux inhibition by milbemycin α25 (8 mutants), enniatin B (8), or beauvericin (4). The 20 mutations were in just 9 residues at the centers of transmembrane segment 1 (TMS1) (6 mutations), TMS4 (4), TMS5 (4), TMS8 (1), and TMS11 (2) and in A713P (3), a previously reported FK506-resistant "hot spot 1" mutation in extracellular loop 3. Six Cdr1-G521S/C/V/R (TMS1) variants were resistant to all four inhibitors, four Cdr1-M639I (TMS4) variants were resistant to milbemycin α25 and enniatin B, and two Cdr1-V668I/D (TMS5) variants were resistant to enniatin B and beauvericin. The eight milbemycin α25-resistant mutants were altered in four amino acids as follows: G521R, M639I, A713P, and T1355N (TMS11). These four Cdr1 variants responded differently to various types of inhibitors, and each exhibited altered substrate specificity and kinetic properties. The data infer an entry gate function for Cdr1-G521 and a role for Cdr1-A713 in the constitutively high Cdr1 ATPase activity. Cdr1-M639I and -T1355N possibly cause inhibitor resistance by altering TMS contacts near the substrate/inhibitor-binding pocket. Models for the interactions of substrates and different types of inhibitors with Cdr1 at various stages of the transport cycle are presented.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Candida albicans , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/metabolismo , Antifúngicos/metabolismo , Antifúngicos/farmacología , Candida albicans/genética , Candida albicans/metabolismo , Farmacorresistencia Fúngica/genética , Fluconazol/metabolismo , Fluconazol/farmacología , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Especificidad por SustratoRESUMEN
Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are common therapeutic agents for EGFR mutation-positive advanced non-small-cell lung cancer. There has been no report of rhabdomyolysis caused by an overdose of EGFR-TKIs. We herein review the existing literature on the subject and report a rare case of rhabdomyolysis due to an overdose of gefitinib, an EGFR-TKI.
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Antineoplásicos , Carcinoma de Pulmón de Células no Pequeñas , Neoplasias Pulmonares , Rabdomiólisis , Antineoplásicos/efectos adversos , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Receptores ErbB/genética , Gefitinib/efectos adversos , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Mutación , Inhibidores de Proteínas Quinasas/uso terapéutico , Quinazolinas/efectos adversos , Rabdomiólisis/inducido químicamente , Rabdomiólisis/tratamiento farmacológicoRESUMEN
We clarified the roles of VPH1 in Cryptococcus neoformans serotype D by examining the detailed phenotypes of VPH1-deficient cells (Δvph1) in terms of their capability to grow in acidic and alkaline pH, at a high temperature, and under high osmotic conditions, in addition to the involvement of VPH1 in copper (Cu) homeostasis and the expression of some C. neoformans virulence factors. Δvph1 could grow well on minimal medium (YNB) but exhibited hypersensitivity to 20 µM Cu due to the failure to induce Cu-detoxifying metallothionein genes (CMT1 and CMT2). In contrast, Δvph1 exhibited defective growth on rich medium (YPD), and the induction of Cu transporter genes (CTR1 and CTR4) did not occur in this medium, implying that this strain was incapable of the uptake of Cu ions for growth. However, the addition of excess Cu promoted CTR gene expression and supported Δvph1 growth. These results suggested that the lack of the VPH1 gene disturbed Cu homeostasis in C. neoformans. Moreover, the loss of Vph1 function influenced the urease activity of C. neoformans.
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Proteínas Bacterianas/metabolismo , Cobre/fisiología , Cryptococcus neoformans/fisiología , Cryptococcus neoformans/genética , Homeostasis , SerogrupoRESUMEN
Introduction: Candida albicans is an opportunistic pathogen that causes oral candidiasis. A previous study showed that Bgl2p and Ecm33p may mediate the interaction between the yeast and saliva-coated hydroxyapatite (SHA; a model for the tooth surface). This study investigated the roles of these cell wall proteins in the adherence of C. albicans to SHA beads. Methods: C. albicans BGL2 and ECM33 null mutants were generated from wild-type strain SC5314 by using the SAT1-flipper gene disruption method. A novel method based on labelling the yeast with Nile red, was used to investigate the adherence. Results: Adhesion of bgl2Δ and ecm33Δ null mutants to SHA beads was 76.4% and 64.8% of the wild-type strain, respectively. Interestingly, the adhesion of the bgl2Δ, ecm33Δ double mutant (87.7%) was higher than that of both single mutants. qRT-PCR analysis indicated that the ALS1 gene was over-expressed in the bgl2Δ, ecm33Δ strain. The triple null mutant showed a significantly reduced adherence to the beads, (37.6%), compared to the wild-type strain. Conclusion: Bgl2p and Ecm33p contributed to the interaction between C. albicans and SHA beads. Deletion of these genes triggered overexpression of the ALS1 gene in the bgl2Δ/ecm33Δ mutant strain, and deletion of all three genes caused a significant decrease in adhesion.
RESUMEN
A 72-year-old man was treated with prednisolone and cyclosporine A for idiopathic pulmonary fibrosis. A nodule with a diameter of 19 mm was found in the right lung and diagnosed as lung squamous cell carcinoma. Anti-cancer treatments were not performed because of the presence of advanced interstitial pneumonia and chronic respiratory failure. Cyclosporine A was tapered to avoid suppression of anti-tumor immunity, and pirfenidone was initiated. Within 2 months, the tumor had shrunk to 10 mm in diameter and remained regressed for 9 months. This is the first report of a non-hematologic solid organ tumor responding to the discontinuation of immunosuppressants.
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Carcinoma de Células Escamosas , Fibrosis Pulmonar Idiopática , Neoplasias Pulmonares , Anciano , Antiinflamatorios no Esteroideos/uso terapéutico , Carcinoma de Células Escamosas/tratamiento farmacológico , Ciclosporina/uso terapéutico , Humanos , Fibrosis Pulmonar Idiopática/tratamiento farmacológico , Pulmón , Neoplasias Pulmonares/tratamiento farmacológico , Masculino , Piridonas/uso terapéutico , Resultado del TratamientoAsunto(s)
Asma/complicaciones , COVID-19/complicaciones , Corticoesteroides/administración & dosificación , Asma/diagnóstico , Asma/patología , Asma/terapia , COVID-19/diagnóstico , COVID-19/patología , COVID-19/terapia , Terapia Combinada , Femenino , Humanos , Pulmón/diagnóstico por imagen , Pulmón/efectos de los fármacos , Pulmón/patología , Persona de Mediana Edad , SARS-CoV-2/aislamiento & purificación , SARS-CoV-2/patogenicidad , Brote de los SíntomasRESUMEN
OBJECTIVE: Malignant pleural effusions (MPEs) deteriorate the quality of life in patients with advanced stages of cancer. Although vascular endothelial growth factor (VEGF) is known to be a key factor for MPE formation, it is not fully clarified whether there are other components related to its appearance. METHODS: Pleural effusion and serum samples were collected from patients with MPEs of non-small cell lung cancer. Cellular analysis of pleural effusion was performed using fluorescence flow cytometry. The concentrations of 12 cytokines, chemokines, and growth factors in MPEs and serum samples were analyzed using the cytometric bead array method. RESULTS: Fifteen patients (median age: 70 years, 11 males) with non-small cell lung cancer (13 adenocarcinoma, 2 squamous cell carcinoma) were enrolled in this study. Concentrations of VEGF, interleukin (IL)-5, IL-6, IL-8, IL-12/IL-23p40, and C-C motif chemokine ligand (CCL) 2 were significantly higher in MPE than in serum. Pleural IL-5 levels correlated with malignant cell numbers in MPE. There was no factor related to the total amount of drained effusion or period of chest tube insertion. CONCLUSIONS: Production of six molecules were increased in the pleural cavity with MPE of non-small cell lung cancer. Complex interactions among these molecules may regulate MPE formation.
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Carcinoma de Pulmón de Células no Pequeñas/complicaciones , Quimiocinas/metabolismo , Citocinas/metabolismo , Neoplasias Pulmonares/complicaciones , Derrame Pleural Maligno/etiología , Factor A de Crecimiento Endotelial Vascular/metabolismo , Anciano , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Femenino , Humanos , Interleucina-12/metabolismo , Interleucina-23/metabolismo , Interleucina-5/metabolismo , Neoplasias Pulmonares/metabolismo , Masculino , Cavidad Pleural/metabolismo , Derrame Pleural Maligno/genética , Derrame Pleural Maligno/metabolismoRESUMEN
PENICILLIUM MARNEFFEI: is a thermally dimorphic fungus that causes penicilliosis, and become the third-most-common opportunistic fungal infection in immunocompromised patients in Southeast Asia. Azoles and amphotericin B have been introduced for the treatment, however, it is important to investigate possible mechanisms of azole resistance for future treatment failure. We identified 177 putative MFS transporters and classified into 17 subfamilies. Among those, members of the Drug:H+ antiporter 1 subfamily are known to confer resistance to antifungals. Out of 39 paralogs, three (encoded by PmMDR1, PmMDR2, and PmMDR3) were heterologously overexpressed in S. cerevisiae AD∆ conferred resistance to various drugs and compounds including azoles, albeit to different degrees. PmMDR1-expressing strain showed resistance to the broadest range of drugs, followed by the PmMDR3, and PmMDR2 conferred weak resistance to a limited range of drugs. We conclude that PmMDR1 and PmMDR3, may be able to serve as multidrug efflux pumps.
Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/química , Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Anfotericina B/farmacología , Antifúngicos/farmacología , Micosis/metabolismo , Talaromyces/metabolismo , Triazoles/farmacología , Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Secuencia de Aminoácidos , Anfotericina B/uso terapéutico , Asia Sudoriental/epidemiología , Candida albicans/efectos de los fármacos , Candida albicans/metabolismo , Farmacorresistencia Fúngica/efectos de los fármacos , Humanos , Huésped Inmunocomprometido , Pruebas de Sensibilidad Microbiana , Micosis/tratamiento farmacológico , Micosis/epidemiología , Micosis/microbiología , Filogenia , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Talaromyces/efectos de los fármacos , Transcriptoma , Triazoles/uso terapéuticoRESUMEN
BACKGROUND: Although development of immune checkpoint inhibitors and various molecular target agents has extended overall survival time (OS) in advanced non-small cell lung cancer (NSCLC), a complete cure remains rare. We aimed to identify features and treatment modalities of complete remission (CR) cases in stages III and IV NSCLC by analyzing long-term survivors whose OS exceeded 3 years. METHODS: From our hospital database, 1,699 patients, registered as lung cancer between 1st Mar 2004 and 30th Apr 2011, were retrospectively examined. Stage III or IV histologically or cytologically confirmed NSCLC patients with chemotherapy initiated during this period were enrolled. A Cox proportion hazards regression model was used. Data collection was closed on 13th Feb 2017. RESULTS: There were 164 stage III and 279 stage IV patients, including 37 (22.6%) and 51 (18.3%) long-term survivors and 12 (7.3%) and 5 (1.8%) CR patients, respectively. The long-term survivors were divided into three groups: 3 ≤ OS < 5 years, 5 years ≤ OS with tumor, and 5 years ≤ OS without tumor (CR). The median OS of these groups were 1,405, 2,238, and 2,876 days in stage III and 1,368, 2,503, and 2,643 days in stage IV, respectively. The mean chemotherapy cycle numbers were 16, 20, and 10 in stage III and 24, 25, and 5 in stage IV, respectively. In the stage III CR group, all patients received chemoradiation, all oligometastases were controlled by radiation, and none had brain metastases. Compared with non-CR patients, the stage IV CR patients had smaller primary tumors and fewer metastases, which were independent prognostic factors for OS among long-term survivors. The 80% stage IV CR patients received radiation or surgery for controlling primary tumors, and the surgery rate for oligometastases was high. Pathological findings in the stage IV CR patients revealed that numerous inflammatory cells existed around and inside resected lung and brain tumors, indicating strong immune response. CONCLUSIONS: Multiple line chemotherapies with primary and oligometastatic controls by surgery and/or radiation might achieve cure in certain advanced NSCLC. Cure strategies must be changed according to stage III or IV. This study was retrospectively registered on 16th Jun 2019 in UMIN Clinical Trials Registry (number UMIN000037078).
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Carcinoma de Pulmón de Células no Pequeñas/diagnóstico por imagen , Carcinoma de Pulmón de Células no Pequeñas/terapia , Neoplasias Pulmonares/diagnóstico por imagen , Neoplasias Pulmonares/terapia , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma de Pulmón de Células no Pequeñas/mortalidad , Supervivencia sin Enfermedad , Femenino , Humanos , Neoplasias Pulmonares/mortalidad , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias/métodos , Estadificación de Neoplasias/tendencias , Inducción de Remisión/métodos , Estudios RetrospectivosRESUMEN
The 23-membered-ring macrolide tacrolimus, a commonly used immunosuppressant, also known as FK506, is a broad-spectrum inhibitor and an efflux pump substrate of pleiotropic drug resistance (PDR) ATP-binding cassette (ABC) transporters. Little, however, is known about the molecular mechanism by which FK506 inhibits PDR transporter drug efflux. Thus, to obtain further insights we searched for FK506-resistant mutants of Saccharomyces cerevisiae cells overexpressing either the endogenous multidrug efflux pump Pdr5 or its Candida albicans orthologue, Cdr1. A simple but powerful screen gave 69 FK506-resistant mutants with, between them, 72 mutations in either Pdr5 or Cdr1. Twenty mutations were in just three Pdr5/Cdr1 equivalent amino acid positions, T550/T540 and T552/S542 of extracellular loop 1 (EL1) and A723/A713 of EL3. Sixty of the 72 mutations were either in the ELs or the extracellular halves of individual transmembrane spans (TMSs), while 11 mutations were found near the center of individual TMSs, mostly in predicted TMS-TMS contact points, and only two mutations were in the cytosolic nucleotide-binding domains of Pdr5. We propose that FK506 inhibits Pdr5 and Cdr1 drug efflux by slowing transporter opening and/or substrate release, and that FK506 resistance of Pdr5/Cdr1 drug efflux is achieved by modifying critical intramolecular contact points that, when mutated, enable the cotransport of FK506 with other pump substrates. This may also explain why the 35 Cdr1 mutations that caused FK506 insensitivity of fluconazole efflux differed from the 13 Cdr1 mutations that caused FK506 insensitivity of cycloheximide efflux.