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1.
Artigo em Inglês | MEDLINE | ID: mdl-38682421

RESUMO

AIM: A new treatment interval for nivolumab administration at 480 mg every 4 weeks, in addition to 240 mg every 2 weeks, was approved in Japan in 2020. Using model-based evaluation, it was speculated that the effects or safety of nivolumab do not differ between the two treatment intervals; however, real-world data on nivolumab efficacy, safety, and economic impact are lacking. Accordingly, we aimed to examine the effects of nivolumab treatment intervals (2 weeks vs. 4 weeks) in terms of efficacy, safety, and economic impact in Japanese patients with cancer. METHODS: We retrospectively analyzed 126 patients treated with nivolumab. The patients were divided into two groups depending on whether they received nivolumab at 240 mg every 2 weeks (2-week group) or 480 mg every 4 weeks (4-week group). RESULTS: Efficacy results found no significant difference between the 4- and 2-week groups considering median overall survival (p = 0.70) and median progression-free survival (p = 0.57). The incidence of any grade and ≥  grade 3 immune-related adverse events did not differ between the 4-week and 2-week groups (any grade, p = 0.13; ≥  grade 3, p = 0.36). Excluding drug costs, the 4-week group had significantly lower medical costs than the 2-week group (2-week vs. 4-week: mean, 94,659 JPY [679.0 USD] vs. 58,737 JPY [421.3 USD]; p < 0.05). CONCLUSION: Collectively, our findings suggest that nivolumab 480 mg every 4 weeks may be more effective than nivolumab 240 mg every 2 weeks in terms of economic impact.

2.
Cancer Med ; 12(24): 21666-21679, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37986680

RESUMO

BACKGROUND: Immune checkpoint inhibitors (ICIs) can cause severe immune-related adverse events (irAEs). However, biomarkers for irAEs common to different types of ICIs and cancers have not been reported. This study examined whether eosinophils can be used as a predictor of irAEs. METHODS: Six hundred fourteen patients with cancer (esophageal, gastric, head and neck, lung, melanoma, renal cell, urothelial, and other cancer) received anti-PD-1, anti-PD-L1, or anti-CTLA-4 plus anti-PD-1 therapy. The patients were divided into two groups depending on whether they experienced irAEs (irAE group) or not (non-irAE group). Eosinophils were examined before the two-course treatment. RESULTS: Patients in the irAE group who received anti-PD-1 or anti-CTLA-4 plus anti-PD-1 therapy had higher eosinophils before the two-course treatment than those in the non-irAE group (p < 0.05). The eosinophils in the anti-PD-L1 therapy group tended to increase in the irAE group. Furthermore, eosinophils in gastric, head and neck, lung, melanoma, renal, and urothelial cancers were significantly higher in the irAE group than in the non-irAE group (p < 0.05). The optimal cutoff value for eosinophils against irAEs was 3.0% (area under the curve = 0.668). In multivariate analyses, eosinophils of ≥3.0% were an independent factor for irAEs (odds ratio: 2.57, 95% CI: 1.79-3.67). CONCLUSION: An increased eosinophil before the two-course treatment may be a predictor of irAEs in various cancers treated with different ICIs.


Assuntos
Melanoma , Humanos , Melanoma/tratamento farmacológico , Inibidores de Checkpoint Imunológico/efeitos adversos , Eosinófilos , Estudos Retrospectivos , Biomarcadores
3.
Int J Urol ; 30(10): 866-874, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37278575

RESUMO

OBJECTIVES: Ipilimumab and nivolumab treatment against advanced and metastatic renal cell carcinoma (RCC) causes severe and lethal immune-related adverse events (irAEs). Predicting irAEs might improve clinical outcomes, however no practical biomarkers exist. This study examined whether eosinophils could be effective biomarkers for ≥grade 2 irAEs in RCC. METHODS: We retrospectively analyzed 75 patients with RCC treated with ipilimumab and nivolumab between August 2018 and March 2021 in a multicenter study. Eosinophils were examined before and 2 weeks after treatment, and immediately after irAEs development. The optimal cut-off value for ≥grade 2 irAEs was determined by a receiver operating characteristic (ROC) curve. Univariate and multivariate analyses were undertaken to identify predictors of ≥grade 2 irAEs. RESULTS: Two weeks after treatment, eosinophils were significantly upregulated in patients who had experienced ≥grade 2 irAEs than in those who had not experienced irAEs (mean, 5.7% vs. 3.2%; p < 0.05). The optimal cut-off value for eosinophils against ≥grade 2 irAEs was 3.0% (area under the curve = 0.69). In multivariate analyses, an eosinophil level ≥ 3.0% was a risk factor for ≥grade 2 irAEs (odds ratio 4.18, 95% confidence interval 1.16-15.1). The eosinophil level 2 weeks after treatment was upregulated by the onset of any type of irAEs including endocrine, gastrointestinal, pulmonary and skin disorders. CONCLUSIONS: An increased eosinophil level 2 weeks after treatment might be an effective biomarker for ≥grade 2 irAEs in patients with RCC treated with ipilimumab and nivolumab.


Assuntos
Antineoplásicos Imunológicos , Carcinoma de Células Renais , Neoplasias Renais , Melanoma , Humanos , Nivolumabe/efeitos adversos , Ipilimumab/efeitos adversos , Carcinoma de Células Renais/tratamento farmacológico , Eosinófilos/patologia , Melanoma/tratamento farmacológico , Melanoma/induzido quimicamente , Estudos Retrospectivos , Antineoplásicos Imunológicos/efeitos adversos , Neoplasias Renais/tratamento farmacológico , Neoplasias Renais/patologia , Biomarcadores
4.
Int J Urol ; 30(9): 754-761, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37150513

RESUMO

OBJECTIVE: To identify biomarkers associated with the effectiveness of ipilimumab plus nivolumab against advanced metastatic renal cell carcinoma. METHODS: We retrospectively analyzed the data of 75 patients treated with ipilimumab plus nivolumab at seven hospitals between August 2018 and April 2021. Prognostic biomarkers were assessed prior to initiating treatment with ipilimumab plus nivolumab. Median overall survival and progression-free survival were examined using the Kaplan-Meier method. Univariate and multivariate analyses were performed to identify predictors of disease progression. The International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) risk factors most important for predicting disease progression were determined using classification and regression tree analysis. RESULTS: Median overall survival and progression-free survival were longer in the intermediate IMDC risk group than in the poor IMDC risk group (overall: not reached vs. 18.3 months; progression-free: not reached vs. 13.5 months). The multivariate analysis identified poor IMDC risk as a risk factor for disease progression (hazard ratio 2.61, 95% confidence interval: 1.05-6.51). Based on the results of the classification and regression tree analysis, the cohort was divided into non-anemia, anemia + neutro-Low, and anemia + neutro-High groups. Median overall survival and progression-free survival were longer in the non-anemia and anemia + neutro-Low groups than in the anemia + neutro-High group (overall: not reached vs. 29.3 months vs. 4.3 months: progression-free: not reached vs. 29.0 months vs. 3.9 months). CONCLUSION: Hemoglobin and neutrophil levels may represent crucial biomarkers for predicting the effectiveness of ipilimumab plus nivolumab therapy in patients with renal cell carcinoma.


Assuntos
Carcinoma de Células Renais , Neoplasias Renais , Humanos , Carcinoma de Células Renais/patologia , Nivolumabe/uso terapêutico , Ipilimumab/uso terapêutico , Ipilimumab/efeitos adversos , Neoplasias Renais/patologia , Estudos Retrospectivos , Neutrófilos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Progressão da Doença , Hemoglobinas/uso terapêutico
5.
Oncology ; 101(4): 224-233, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36689919

RESUMO

INTRODUCTION: This study evaluated the prognostic value of a sustained high Geriatric Nutritional Risk Index (GNRI) during first-line chemotherapy for patients with metastatic urothelial carcinoma (mUC). METHODS: Between January 2018 and February 2022, 123 patients received platinum-based chemotherapy at Nagoya City University Hospital and affiliated institutions. Of these, 118 eligible patients who showed an Eastern Cooperative Oncology Group performance status (ECOG-PS) between 0 and 2 were retrospectively examined. Based on body mass index and serum albumin levels, GNRI was calculated immediately before and after the first primary chemotherapy cycle. Patients were divided into two groups based on GNRI: GNRI sustained ≥92 in sustainable (n = 63) and GNRI <92 in unsustainable (n = 55) groups, respectively. Clinical outcomes were compared. RESULTS: No significant differences were noted between the two groups for age, gender, cycle of first-line treatment, and type of series of sequential treatments after failure of first-line therapy. Median overall survival from the start of first-line chemotherapy was 30.2 months (95% confidence interval [CI]: 20.9-NA) for sustainable and 12.6 months (95% CI: 9.0-21.2) for unsustainable groups, respectively (p < 0.05). Multivariate analysis identified ECOG-PS:2 and fatigue, an adverse event, as independent predictors of unsustainable GNRI transition (95% CI: 1.29-90.6, odds ratio [OR]: 10.8; 95% CI: 1.06-26.9, OR: 5.34, respectively). CONCLUSION: Sustaining a high level of GNRI was an important prognostic indicator in patients with mUC receiving first-line chemotherapy. Appropriate intervention for controlling adverse events, including fatigue, may enhance physical strength during cancer treatment.


Assuntos
Carcinoma de Células de Transição , Neoplasias da Bexiga Urinária , Humanos , Idoso , Prognóstico , Carcinoma de Células de Transição/tratamento farmacológico , Estudos Retrospectivos , Avaliação Nutricional , Fatores de Risco , Neoplasias da Bexiga Urinária/tratamento farmacológico , Avaliação Geriátrica
6.
Ther Drug Monit ; 45(2): 245-250, 2023 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-36006610

RESUMO

BACKGROUND: The area under the concentration-time curve (AUC)-guided dosing of vancomycin has been introduced in Japan; however, the optimal dosing method remains controversial. Here, a novel software program was developed for AUC-guided vancomycin dosing and to estimate the theoretical threshold of the steady-state AUC 24 that could reduce the risk of renal injury. METHODS: A single-center, retrospective, observational study was conducted to develop a novel software program (SAKURA-TDM ver.1.0) for AUC-guided dosing. The estimation accuracy of pharmacokinetic parameters determined using SAKURA-TDM was compared with that of clinically available software programs and assessed with Bland-Altman analysis. In addition, theoretical cutoff points of the steady-state AUC 24 and the predicted trough values were estimated using Youden J statistic approach. RESULTS: The estimation accuracy of pharmacokinetic parameters and AUC determined using SAKURA-TDM was comparable to that of other TDM software programs. Of note, despite a good relationship between the predicted AUC 24 and trough values, the correlation between the predicted AUC 24 and measured trough values was not strong. The cutoff values of the steady-state AUC 24 and the predicted trough value for reducing the probability of a measured trough value of >20 mcg/mL were 513.1 mg·h/L and 15.6 mcg/mL, respectively. CONCLUSIONS: We demonstrated the equivalence of the estimated PK parameters between SAKURA-TDM and other TDM software programs available in Japan. Considering the threshold of both trough values and the steady-state AUC and monitoring of the AUC in a non-steady state, it would be possible to reduce the risk of vancomycin-associated renal injury.


Assuntos
Antibacterianos , Vancomicina , Humanos , Vancomicina/farmacocinética , Antibacterianos/farmacocinética , Estudos Retrospectivos , Área Sob a Curva , Software , Testes de Sensibilidade Microbiana
7.
In Vivo ; 35(5): 2793-2800, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34410970

RESUMO

BACKGROUND/AIM: Predicting the prognosis of metastatic urothelial carcinoma (mUC) patients is needed for clinical decisions. We examined the value of a modified Glasgow prognostic score (mGPS) as a predictive marker for mUC patients. PATIENTS AND METHODS: In a multicenter study, 68 mUC patients received short hydration gemcitabine/cisplatin (shGC) and 74 received pembrolizumab (PEM). Patients were allocated according to mGPS. Progression-free (PFS) and cancer-specific (CSS) survival were examined. RESULTS: Higher mGPS reflected poorer PFS and CSS in shGC (p=0.03, p<0.0001, respectively) and PEM (p=0.02, p<0.001, respectively) patients. PFS for the high mGPS group was longer than that of the low mGPS group in the two cohorts (p <0.0001 for both), with similar CSS results (p<0.0001 and p<0.001, respectively). Multivariate analyses revealed high mGPS was a risk factor for poor CSS in both cohorts (HR=3.55, p<0.001, and HR=2.21, p<0.01, respectively). CONCLUSION: In the mUC patients receiving shGC or PEM, mGPS was a predictive prognostic marker.


Assuntos
Carcinoma de Células de Transição , Neoplasias da Bexiga Urinária , Carcinoma de Células de Transição/tratamento farmacológico , Humanos , Prognóstico , Estudos Retrospectivos
8.
Cancer Treat Res Commun ; 25: 100245, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33291048

RESUMO

BACKGROUND: It is difficult to objectively evaluate chemotherapy-related adverse events early in elderly patients with urothelial carcinoma. A delayed response causes a reduction in quality of life (QoL). Wearable activity systems that objectively record life logs have recently been used. OBJECTIVES: This study was undertaken to verify the reliability and effectiveness of a wearable activity system (Fitbit) to monitor subjective symptoms in an objective manner during chemotherapy for elderly patients with urothelial cancer (UC). MATERIALS AND METHODS: This was a cohort prospective study. Elderly patients with UC were enrolled who received short hydration gemcitabine and cisplatin (shGC) combination therapy at Nagoya City University Hospital from January 2018 to March 2020. A Fitbit was used to monitor heart rate, distance moved, and cardio zone time. Heart rate was also monitored by an oscillometric method. The relationship between Fitbit recordings and perceived adverse events, such as fatigue, constipation and nausea, observed during chemotherapy was investigated using a general linear mixed effects model. RESULTS: Twenty-one of 28 inpatients were enrolled and observed for a total of 824 days. A significant, moderately strong correlation was found between two measurements of heart rate (Pearson's r = 0.65, p < 0.05). The measurement of fatigue using Fitbit was effective (p = 0.03). CONCLUSION: Fitbit monitoring can measure the QoL of a patient and was useful for monitoring elderly patients with UC undergoing shGC therapy in an outpatient setting. Fitbit may be useful for monitoring outpatients and their QoL during chemotherapy.


Assuntos
Tratamento Farmacológico/métodos , Monitores de Aptidão Física/normas , Neoplasias Urológicas/tratamento farmacológico , Neoplasias Urológicas/terapia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Qualidade de Vida , Neoplasias Urológicas/fisiopatologia
9.
Oncology ; 98(12): 876-883, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32862183

RESUMO

BACKGROUND: We evaluated the prognostic efficacy of the Geriatric Nutritional Risk Index (GNRI) in second-line pembrolizumab (PEM) therapy for patients with metastatic urothelial carcinoma (mUC). PATIENTS AND METHODS: From January 2018 to October 2019, 52 mUC patients, treated previously with platinum-based chemotherapy, underwent second-line PEM therapy. Peripheral blood parameters were measured at the start of treatment: serum neutrophil-to-lymphocyte ratio (NLR), serum albumin, serum C-reactive protein (CRP), and body height and weight. PEM was intravenously administered (200 mg every 3 weeks). The patients were organized into two groups based on their GNRI (<92 [low GNRI] and ≥92 [high GNRI]), and the data were retrospectively analyzed. Adverse events (AEs) were evaluated and imaging studies assessed for all patients. Analyses of survival and recurrence were performed using Kaplan-Meier curves. Potential prognostic factors affecting cancer-specific survival (CSS) were assessed by univariate and multivariate Cox regression analyses. RESULTS: patients' baseline characteristics, except for their BMI and objective response rate, did not significantly differ between the two groups. The median total number of cycles of PEM therapy was significantly higher for the high-GNRI group (n [range]: 6 [2-20] vs. 3 [1-6]). The median CSS with second-line PEM therapy was 3.6 months (95% confidence interval [CI]: 2.5-6.1) and 11.8 months (95% CI: 6.2-NA) in the low-GNRI and the high-GNRI group (p < 0.01), respectively. Significant differences in CSS between the low- and high-CRP or -NRL groups were not found. Multivariate Cox proportional-hazards regression analysis revealed that a poor Eastern Cooperative Oncology Group performance status, visceral metastasis, and a low GNRI were significant prognostic factors for short CSS (95% CI: 1.62-6.10, HR: 3.14; 95% CI: 1.13-8.11, HR: 3.03; 95% CI: 1.32-8.02, HR: 3.25, respectively). Of the AEs, fatigue showed a significantly higher incidence in the low-GNRI group. CONCLUSIONS: For mUC patients receiving second-line PEM therapy, the GNRI is a useful predictive biomarker for survival outcome.


Assuntos
Anticorpos Monoclonais Humanizados/administração & dosagem , Biomarcadores Tumorais/genética , Carcinoma/tratamento farmacológico , Urotélio/patologia , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais Humanizados/efeitos adversos , Biomarcadores Tumorais/sangue , Peso Corporal , Proteína C-Reativa/metabolismo , Carcinoma/sangue , Carcinoma/patologia , Feminino , Avaliação Geriátrica , Humanos , Linfócitos/patologia , Masculino , Pessoa de Meia-Idade , Metástase Neoplásica , Recidiva Local de Neoplasia , Neutrófilos/patologia , Avaliação Nutricional , Prognóstico , Intervalo Livre de Progressão , Estudos Retrospectivos , Fatores de Risco , Urotélio/efeitos dos fármacos
10.
Physiol Rep ; 6(10): e13714, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29845779

RESUMO

Sodium-dependent nucleobase transporter 1 (SNBT1) is a nucleobase-specific transporter identified in our recent study. In an attempt to search for its potential substrates other than nucleobases in this study, we could successfully find urate, a metabolic derivative of purine nucleobases, as a novel substrate, as indicated by its specific Na+ -dependent and saturable transport, with a Michaelis constant of 433 µmol/L, by rat SNBT1 (rSNBT1) stably expressed in Madin-Darby canine kidney II cells. However, urate uptake was observed only barely in the everted tissue sacs of the rat small intestine, in which rSNBT1 operates for nucleobase uptake. These findings suggested that urate undergoes a futile cycle, in which urate transported into epithelial cells is immediately effluxed back by urate efflux transporters, in the small intestine. In subsequent attempts to examine that possibility, such a futile urate cycle was demonstrated in the human embryonic kidney 293 cell line as a model cell system, where urate uptake induced by transiently introduced rSNBT1 was extensively reduced by the co-introduction of rat breast cancer resistance protein (rBCRP), a urate efflux transporter present in the small intestine. However, urate uptake was not raised in the presence of Ko143, a BCRP inhibitor, in the everted intestinal tissue sacs, suggesting that some other transporter might also be involved in urate efflux. The newly found urate transport function of SNBT1, together with the suggested futile urate cycle in the small intestine, should be of interest for its evolutional and biological implications, although SNBT1 is genetically deficient in humans.


Assuntos
Proteínas de Transporte de Nucleobases/metabolismo , Ácido Úrico/metabolismo , Animais , Transporte Biológico , Cães , Células HEK293 , Humanos , Intestino Delgado/metabolismo , Células Madin Darby de Rim Canino , Masculino , Ratos Wistar
11.
J Pharm Sci ; 106(9): 2592-2598, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28089688

RESUMO

The intestinal absorption of atenolol has recently been reported to be reduced by simultaneous ingestion of fruit juices, such as apple juice. This finding implies a possibility that an unidentified carrier-mediated transport system, which could be interfered by some components of those juices, might be involved in atenolol absorption. In an attempt to explore that possibility, we successfully identified plasma membrane monoamine transporter (PMAT/SLC29A4) as a transporter that can operate for cellular atenolol uptake in the intestine, using Madin-Darby canine kidney II cells stably expressing PMAT. The specific uptake of atenolol by PMAT was greatest at around pH 6.0 and decreased with an increase in pH. At pH 6.0, the PMAT-specific uptake of atenolol was saturable with a Michaelis constant of 0.907 mM. Moreover, PMAT-specific atenolol uptake was extensively inhibited by phloretin and quercetin, which are the major flavonoids contained in apple juice, with the half maximal inhibitory concentrations of 33.3 and 116.3 µM, respectively. PMAT-specific atenolol uptake was also inhibited by several ß-blockers, suggesting that they may also be recognized and transported by PMAT. These results suggest that PMAT is an atenolol transporter that may be involved in intestinal atenolol absorption and sensitive to flavonoids contained in apple juice.


Assuntos
Atenolol/metabolismo , Proteínas de Transporte de Nucleosídeo Equilibrativas/metabolismo , Flavonoides/metabolismo , Sucos de Frutas e Vegetais/análise , Malus/química , Animais , Atenolol/química , Transporte Biológico , Linhagem Celular , Membrana Celular/metabolismo , Cães , Flavonoides/química , Expressão Gênica , Células HEK293 , Humanos , Absorção Intestinal/fisiologia , Rim/metabolismo , Especificidade por Substrato , Termodinâmica
12.
J Pharmacol Exp Ther ; 360(1): 59-68, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27807008

RESUMO

A suicide gene therapy using herpes simplex virus thymidine kinase (HSV-TK) with ganciclovir (GCV) has been under development as a tumor-targeted therapy; however, the mechanism of cellular GCV uptake, which is prerequisite in the therapy, has not been clarified. In an attempt to resolve this situation and gain information to optimize HSV-TK/GCV system for cancer therapy, we found that human equilibrative nucleobase transporter 1 (ENBT1) can transport GCV with a Michaelis constant of 2.75 mM in Madin-Darby canine kidney II (MDCKII) cells stably transfected with this transporter. In subsequent experiments using green fluorescent protein (GFP)-tagged ENBT1 (GFP-ENBT1) and HSV-TK, the uptake of GCV (30 µM), which was minimal in MDCKII cells and unchanged by their transfection with HSV-TK alone, was increased extensively by their transfection with GFP-ENBT1, together with HSV-TK. Accordingly, cytotoxicity, which was assessed by the WST-8 cell viability assay after the treatment of those cells with GCV (30 µM) for 72 hours, was induced in those transfected with GFP-ENBT1, together with HSV-TK but not in those transfected with HSV-TK alone. These results suggest that ENBT1 could facilitate GCV uptake and thereby enhance cytotoxicity in HSV-TK/GCV system. We also identified Helacyton gartleri (HeLa) and HepG2 as cancer cell lines that are rich with ENBT1 and A549, HCT-15 and MCF-7 as those poor with ENBT1. Accordingly, the HSV-TK/GCV system was effective in inducing cytotoxicity in the former but not in the latter. Thus, ENBT1 was found to be a GCV transporter that could enhance the performance of HSV-TK/GCV suicide gene therapy.


Assuntos
Sistemas de Transporte de Aminoácidos/metabolismo , Apoptose/genética , Ganciclovir/metabolismo , Ganciclovir/farmacologia , Terapia Genética , Simplexvirus/enzimologia , Timidina Quinase/genética , Animais , Transporte Biológico , Linhagem Celular , Cães , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Simplexvirus/genética
13.
Biochem Biophys Rep ; 2: 166-171, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29124159

RESUMO

Atenolol, a ß1-adrenergic receptor blocker, is administered orally and its intestinal absorption has recently been indicated to be mediated by carrier protein and reduced markedly by ingestion of some fruit juices, such as apple and orange juices. This could be postulated to be a problem arising from the interaction of some components of fruit juices with atenolol at a transporter involved in its intestinal uptake, but the responsible transporter and its interacting components have not been identified yet. In an attempt to examine that possibility, we could successfully find that human organic cation transporter 1 (OCT1/SLC22A1), which is suggested to be expressed at the brush border membrane of enterocytes, is highly capable of transporting atenolol. In this attempt, OCT1 was stably expressed in Madin-Darby canine kidney II cells and the specific uptake of atenolol by the transporter was found to be saturable, conforming to the Michaelis-Menten kinetics with the maximum transport rate (Vmax) of 4.00 nmol/min/mg protein and the Michaelis constant (Km) of 3.08 mM. Furthermore, the OCT1-specific uptake was found to be inhibited by various flavonoids, including those contained in fruit juices that have been suggested to interfere with intestinal atenolol absorption. Particularly, phloretin and quercetin, which are major components of apple juice, were potent in inhibiting OCT1-mediated atenolol transport with the inhibition constants of 38.0 and 48.0 µM, respectively. It is also notable that the inhibition by these flavonoids was of the noncompetitive type. These results indicate that OCT1 is an atenolol transporter that may be involved in intestinal atenolol uptake and sensitive to fruit juices, although its physiological and clinical relevance remains to be further examined.

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