CD36 Expression Is Associated with Cancer Aggressiveness and Energy Source in Esophageal Squamous Cell Carcinoma.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is an important cause of cancer-related death worldwide. CD36, a long-chain fatty acid (FA) receptor, can initiate metastasis in human oral squamous cell carcinoma (SCC), and its expression is associated with poor prognosis in several cancers. The clinical significance of CD36 expression and its function in ESCC remain unknown. METHODS: We examined the clinical significance of CD36 expression in 160 ESCC samples using immunohistochemical staining. Functional analysis was performed to determine the association between CD36 and ESCC characteristics (proliferative ability, invasive ability, and energy source dependency). RESULTS: Thirty (18.8%) ESCC cases showed high CD36 expression, indicating a significant association with progression. CD36 suppression inhibited proliferation and invasiveness in ESCC cells. ESCC cells with CD36 suppression used specific essential amino acids (EAAs) as energy sources. Cell viability depended on FAs under CD36 expression. The viability of ESCC cells with CD36 suppression depended on EAAs but not FAs. CONCLUSIONS: CD36 may be a good biomarker and therapeutic target in ESCC. Our data provide new insights into the basic mechanism of CD36-dependent energy utilization for ESCC survival. CD36 might be a key regulator of the dependency of FAs as energy source in ESCC cells.

Comparable Data Between Double Endoscopic Intraluminal Operation and Conventional Endoscopic Submucosal Dissection for Esophageal Cancer.

BACKGROUND: Endoscopic submucosal dissection (ESD) of superficial esophageal cancer has been used increasingly as an alternative to surgery because it is minimally invasive and has a high rate of en bloc resection. We previously reported that the double endoscopic intraluminal operation (DEILO) is a useful technique for ESD of early esophageal cancers. In the current study, we showed comparable short-term data between DEILO and conventional ESD groups to demonstrate the further advanced use of DEILO. METHODS: We studied 111 esophageal cancer patients with 111 lesions treated using endoscopic surgery between January 2010 and June 2016 at Gunma University Hospital. Of the patients, 51 underwent DEILO (DEILO group) and 60 underwent conventional ESD (ESD group). We compared the operable performance, complications, and pathological outcome between the ESD and DEILO groups. RESULTS: There was no significant difference in operable performance. However, the DEILO group showed a significantly lower rate of mediastinal emphysema compared to the ESD group (p = 0.025). Overall, the DEILO group showed a lower complication rate compared to the ESD group, although there was no apparent significance. CONCLUSION: To our knowledge, this is the first report comparing DEILO and conventional ESD for esophageal cancer. The results showed that DEILO is not inferior to conventional ESD. DEILO is an excellent endoscopic surgical method, although it has some limitations compared to conventional ESD.

High expression of carcinoembryonic antigen and telomerase reverse transcriptase in circulating tumor cells is associated with poor clinical response to the immune checkpoint inhibitor nivolumab.

The present study aimed to enrich circulating tumor cells (CTCs) from blood samples using a new size-sorting CTC chip. The present study also set out to identify a blood sensitivity marker for the immune checkpoint inhibitor nivolumab in patients with advanced, pre-treatment lung cancer. The CTC sorting efficacy of the chip was investigated and the large cell fraction of blood samples from 15 patients with pre-treatment lung cancer who were later administered nivolumab were purified. The expression levels of carcinoembryonic antigen (CEA), human Telomerase Reverse Transcriptase (hTERT), cytokeratin19 (CK19), and programmed death ligand-1 (PD-L1) were investigated to clarify the association between these CTC markers and the clinical response to nivolumab. The CTC chip effectively enriched cells from lung cancer cell line PC-9. The large cell fraction had a high expression of CEA and hTERT, with the former being significantly associated with the clinical response to nivolumab. The expression of CEA and hTERT in CTCs derived from the blood of a patient with lung cancer were also validated. The evaluation of CEA and possibly hTERT in CTCs collected by the CTC chip may represent a promising predictive blood marker for sensitivity to nivolumab. To the best of our knowledge this is the first report to describe the predictive CTC marker for nivolumab in pre-treatment patients.

Association of Preoperative Nutritional Status with Prognosis in Patients with Esophageal Cancer Undergoing Salvage Esophagectomy.

BACKGROUND: To investigate whether malnutrition is associated with poor prognosis of patients who undergo salvage esophagectomy. We examined the association between the preoperative prognostic nutritional index (PNI) and prognosis of patients who undergo salvage esophagectomy. PATIENTS AND METHODS: We conducted a single-center retrospective study and reviewed hospital patient records for tumor characteristics and patient outcomes. Univariate and multivariate survival analyses were carried out using the Cox proportional hazards regression model. RESULTS: Thirty-two patients with esophageal squamous cell carcinoma (ESCC) who underwent salvage esophagectomy between 1998 and 2015 at our Institute were included in this study. Univariate analysis revealed that clinical response (p=0.045), preoperative PNI (p<0.001), pT (p=0.024), pN (p=0.004), and residual tumors (p<0.001) were significant prognostic factor for overall survival. Multivariate analysis using age and these five variables found no independent prognostic factors. Multivariate analysis using three preoperative variables (age, clinical response, and preoperative PNI) revealed that PNI was an independent prognostic preoperative factor for overall survival (p=0.005). CONCLUSION: Preoperative nutritional status is associated with the prognosis of patients undergoing salvage esophagectomy.

Clinical Significance and Phenotype of MTA1 Expression in Esophageal Squamous Cell Carcinoma.

BACKGROUND/AIM: Metastasis-associated gene 1 (MTA1) is considered a potential prognostic factor in esophageal cancer. We investigated the clinical relationship between MTA1, LAT1, and tumor metabolism, as evaluated by positron emission tomography (PET) in esophageal squamous cell carcinoma. MATERIALS AND METHODS: We analyzed 142 esophageal squamous cell carcinoma patients who underwent curative resection without preoperative treatment. MTA1 expression was assessed by immuno-zahistochemistry, and tested against standardized uptake values from preoperative PET-CT. The association among MTA1, LAT1, and 18FAMT PET results were analyzed. RESULTS: MTA1 staining was observed in 82 of 142 cancer tissues. Five-year overall survival was 69.9 % in the absence of MTA1, but 50.7% otherwise (p=0.021), while disease-free survival was 66.5% and 49.0% (p=0.071), respectively. Abnormal 18FAMT accumulation was noted in 13 patients without MTA1 and in 18 patients with MTA1 (p=0.079), with maximum standardized uptake value 1.6±1.6 and 2.7±1.6, respectively (p=0.036). MTA1 expression was positively correlated with LAT1 (p=0.013) and CD34 (p=0.034) expression, but not with Ki-67 (p=0.078). CONCLUSION: MTA1 shows promise as a diagnostic and prognostic marker in esophageal cancer, and we anticipate that the gene will also prove to be a good therapeutic target.

TNFAIP3 overexpression is an independent factor for poor survival in esophageal squamous cell carcinoma.

Tumor necrosis factor α induced protein 3 (TNFAIP3) is a protein that is induced by TNF-mediated NF-κB activation and has a dual function in regulating NF-κB. TNFAIP3 is associated with inflammatory carcinogenesis in many cancer types. However, the clinical significance of TNFAIP3 expression and function in esophageal squamous cell carcinoma (ESCC) has not yet been reported. We examined 149 ESCC tissue specimens to determine the clinical significance of TNFAIP3 by immunohistochemistry. Western blot analyses were used to detect TNFAIP3 expression in TE-1, TE-8, TE-15 and KYSE-70 ESCC cells and in Het-1A, a non-cancerous esophageal cell line. TNFAIP3 protein knockdown was conducted using small-interfering RNA to investigate its impact on cell proliferation, migration and invasion. Significant correlations between TNFAIP3 expression and differentiation (P=0.04) among clinicopathological characteristics of ESCC patients were demonstrated, and high TNFAIP3 expression was associated with poor survival (P=0.02). Moreover, multivariate analysis result showed that high TNFAIP3 expression was an independent factor for poor survival (P=0.04). In vitro analysis showed high expression of TNFAIP3 protein in TE-15 cells and low expression in Het-1A cells. Furthermore, the proliferation, migration and invasion of TE-15 cells after TNFAIP3 suppression by siRNA were significantly reduced. These findings suggest that TNFAIP3 protein may be an independent prognostic marker for poor survival, and a promising target for ESCC therapy.

Impact of the Level of Anastomosis on Reflux Esophagitis Following Esophagectomy with Gastric Tube Reconstruction.

BACKGROUND: Among patients who undergo gastric tube reconstruction after esophagectomy, it is generally accepted that the incidence of reflux esophagitis (RE) is significantly lower in patients with neck anastomosis than in those with intrathoracic anastomosis. However, the true impact of the level of anastomosis on RE currently remains unclear. METHODS: We examined 53 patients with thoracic esophageal cancer underwent radical esophagectomy with gastric tube reconstruction and neck anastomosis. The level of anastomosis was assessed by measuring the distance from the sternal notch to the stapled ring by computed tomography. The relative level of anastomosis was calculated by the distance from the sternal notch to the most caudal side of the stapled ring (mm)/height (cm). RESULTS: The relative level of anastomosis in 30 (56.6%) patients showed <0, which indicated that anastomosis in these patients was located at a lower level than the sternal notch. The mean relative level of anastomosis was significantly lower in patients with RE (grade A to D) than in those without RE (grade N) (-0.062 vs. -0.012 mm/cm, respectively; p = 0.043). RE was more severe with a lower relative level of anastomosis (p for trends = 0.044). CONCLUSIONS: The level of anastomosis in patients with gastric tube reconstruction following esophagectomy was associated with the incidence of RE. The displacement of anastomosis into the thoracic cavity was detected in approximately half of the patients with neck anastomosis. RE was more severe with a lower level of anastomosis, even in patients with neck anastomosis.

Clinicopathological significance of LAT1 and ASCT2 in patients with surgically resected esophageal squamous cell carcinoma.

BACKGROUND: Amino acid transporters are highly expressed in various human cancers. L-type amino acid transporter 1 (LAT1) and system alanine-serine-cysteine amino acid transporter-2 (ASCT2) play a crucial role in tumor progression and survival. However, the clinicopathological significance of these transporters in patients with esophageal squamous cell carcinoma (ESCC) remains unclear. METHODS: One hundred and fifty-seven patients with surgically resected ESCC were evaluated. Immunohistochemical analysis was performed for LAT1, ASCT2, CD98, Ki-67, and micro-vessel density (MVD), as determined by CD34 expression. RESULTS: LAT1 and ASCT2 were positively expressed in 59% (93/157) and 48% (76/157) of tumors respectively. LAT1 and ASCT2 expression significantly correlated with T factor, N factor, lymphatic permeation, vascular invasion, and CD98 expression. The 5-year survival rates of LAT1-high and -low and ASCT2-high and -low expressing patients were 62.0% and 69.6% (P < 0.05) and 59.6% and 70.1% (P = 0.068), respectively. The combined positive expression of LAT1 and ASCT2 was a significant prognostic factor in univariate analysis. CONCLUSION: High expression of LAT1 and ASCT2 correlates with metastasis and invasion. Accordingly, these proteins could serve as prognostic biomarkers and therapeutic targets for treating patients with surgically resectable ESCC. J. Surg. Oncol. 2016;113:381-389. © 2016 Wiley Periodicals, Inc.

TGFBI Expression in Cancer Stromal Cells is Associated with Poor Prognosis and Hematogenous Recurrence in Esophageal Squamous Cell Carcinoma.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is an important cause of cancer-related death worldwide. To improve prognoses in patients with ESCC, we evaluated the potential of transforming growth factor-beta-induced protein (TGFBI), which is overexpressed in ESCC, as a therapeutic candidate. METHODS: We examined the clinical significance of TBFBI in 102 ESCC samples using real-time RT-PCR. Immunohistochemical studies were conducted to examine the localization of TGFBI. Knockdown of TGFBI in cocultured fibroblasts was performed to determine the roles of TGFBI in migration and invasion. RESULTS: The level of TGFBI in ESCC tissues was higher than that in normal tissues. The high TGFBI expression group (n = 16) had higher TGFB1 expression and more frequent hematogenous recurrence than the low-expression group (n = 86). High TGFBI expression was an independent prognostic factor in patients with ESCC. TGFBI was mainly localized in stromal cells of ESCC. Moreover, suppression of TGFBI in fibroblasts inhibited the migration and invasion capacity of TE8 ESCC cells. CONCLUSIONS: High TGFBI expression in ESCC tissues could be a powerful biomarker of poor prognosis and hematogenous recurrence. TGFBI in stromal cells might be a promising molecular target for ESCC treatment.

Umbilical hernia with cholelithiasis and hiatal hernia: a clinical entity similar to Saint's triad.

We experienced two cases involving the simultaneous presence of cholelithiasis, hiatal hernia, and umbilical hernia. Both patients were female and overweight (body mass index of 25.0-29.9 kg/m(2)) and had a history of pregnancy and surgical treatment of cholelithiasis. Additionally, both patients had two of the three conditions of Saint's triad. Based on analysis of the pathogenesis of these two cases, we consider that these four diseases (Saint's triad and umbilical hernia) are associated with one another. Obesity is a common risk factor for both umbilical hernia and Saint's triad. Female sex, older age, and a history of pregnancy are common risk factors for umbilical hernia and two of the three conditions of Saint's triad. Thus, umbilical hernia may readily develop with Saint's triad. Knowledge of this coincidence is important in the clinical setting. The concomitant occurrence of Saint's triad and umbilical hernia may be another clinical "tetralogy."

Nuclear PROX1 is Associated with Hypoxia-Inducible Factor 1α Expression and Cancer Progression in Esophageal Squamous Cell Carcinoma.

BACKGROUND: Transcription factor prospero homeobox 1 (PROX1) has been identified as a master regulator of lymphangiogenesis associated with metastasis. Although PROX1 expression has been investigated in several cancers, its clinical significance remains controversial and needs further validation. In this study, we investigated the clinical and functional significance of PROX1 and PROX1 regulator hypoxia-inducible factor 1α (HIF1α) in esophageal squamous cell carcinoma (ESCC). METHODS: A total of 117 samples from ESCC patients were analyzed for PROX1, HIF1α, and E-cadherin expression by immunohistochemistry; correlation with clinicopathological characteristics was determined. PROX1 function was evaluated in PROX1 small interfering RNA (siRNA)-transfected human ESCC cells in vitro by assessing cell proliferation and migration. RESULTS: PROX1 expression was higher in ESCC than in normal tissues. Patients with higher PROX1 expression (n = 26) had increased nuclear accumulation of HIF1α (p = 0.004) and more advanced metastasis, both lymph node (N factor; p = 0.09) and hematogenous (M factor; p = 0.04), than those with lower PROX1 expression (n = 91). In addition, high PROX1 and HIF1α expression correlated with low levels of E-cadherin, an epithelial cell marker. Analysis of overall and cancer-specific survival indicated that elevated PROX1 expression was significantly correlated with poor prognosis (p = 0.0064). PROX1 downregulation in ESCC cells inhibited cellular proliferation and migration (p < 0.05). Hypoxia restored PROX1 levels that were reduced by PROX1-specific siRNA. CONCLUSION: Our data suggest that high expression of PROX1 in ESCC could be used as an indicator of poor prognosis, and that PROX1 is a promising candidate molecular target for ESCC treatment.

Usefulness of 18f-Fluorodeoxyglucose Positron Emission Tomography for Predicting the Pathological Response of Neoadjuvant Chemoradiotherapy for T4 Esophageal Squamous Cell Carcinoma.

BACKGROUND/AIMS: The purpose of this study is to assess the efficacy of 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) in predicting the pathological response of neoadjuvant chemoradiation (CRT) for clinically diagnosed T4 esophageal squamous cell carcinoma (SCC). METHODOLOGY: We examined 32 patients with T4 thoracic esophageal SCC who received neoadjuvant CRT followed by surgery. RESULTS: Pathological complete response (pCR) was achieved in 7 patients (21.9%). pCR was significant correlated with standardized uptake value (SUV) after neoadjuvant CRT (P = 0.034) and SUV decrease (%) (P = 0.030). The optimal cut-off values to predict pCR were 2.25 for SUV after neoadjuvant CRT and 79.3 for SUV decrease (%). Of note, no patients who did not reach both cut-off values achieved pCR. Conclusions: SUV after CRT and SUV decrease (%) in FDG-PET of the primary tumor are useful tools to predict pathological response of neoadjuvant CRT for T4 esophageal SCC.

Heterotopic mesenteric ossification after a ruptured abdominal aortic aneurism: case report with a review of literatures.

Heterotopic mesenteric ossification (HMO) is a rare disease that results in intra-abdominal ossification of unknown origin. An 88-year-old man developed an intestinal obstruction 2 weeks after undergoing an operation for a ruptured abdominal aortic aneurysm, resulting in intestinal obstructions those did not improved concervatively. During relaparotomy performed 30 days after the first operation, hard adhesions of the small intestine and mesentery were found; these adhesions were difficult to separate without damaging the serosa of the small intestine. We removed 240 cm of the small intestine and performed a jejuno-ileo anastomosis. Microscopically, trabecular bone tissue had increased irregularly in the fat tissue of the nodules with fibrosis, which were partially lined with osteoblasts. Accordingly, we histopathologically diagnosed the patient as having HMO. The patient was treated with NSAIDs and cimetidine to prevent the recurrence of HMO. No signs of recurrence have occurred as of one year after the second operation.

Effect of selective cyclooxygenase-2 inhibitor lumiracoxib on phenolsulfonphthalein disposition in rats.

Selective cyclooxygenase-2 inhibitor lumiracoxib was shown to have the strong inhibitory potencies on the renal organic anion transporter (OAT)1 and also on OAT3 from drug transport experiments. The purpose of this study was to examine the effect of lumiracoxib on disposition of phenolsulfonphthalein (PSP) - which is mainly excreted into urine via OATs - from in vivo experiments. After the intravenous injection of PSP and lumiracoxib into rats, pharmacokinetic analysis was performed. After the intravenous injection of PSP as a bolus, its plasma concentration decreased time-dependently. Until 60 min after the injection, 51.1% of the dose was recovered into urine. The simultaneous administration of lumiracoxib increased the plasma levels of PSP and reduced its urinary recovery to 23.6% of the dose. The pharmacokinetic analysis using a two-compartment model exhibited that lumiracoxib affected the parameters implying the elimination of PSP. The present study demonstrates that lumiracoxib interfered with urinary excretion of PSP in rats.

[The efficacy of postoperative adjuvant chemotherapy for esophageal cancer with lymph node metastasis].

The clinical significance of postoperative 5-fluorouracil+cisplatin(FP) therapy for esophageal cancer with lymph node metastasis was retrospectively investigated. Overall, 37 patients who underwent curative resection of esophageal squamous cell cancer with lymph node metastasis were investigated. Clinical background and prognosis were compared between patients treated with FP therapy(FP group, 13 patients) and patients treated without FP therapy(non-FP group, 24 patients). In the FP group, the completion rate and adverse events were also analyzed. No significant difference was found between the FP and non-FP group in terms of age, gender, tumor location, number of dissected lymph nodes, and number of lymph node metastases. However, the frequency of 3-field lymph node dissection in the FP group was higher than that in the non-FP group(p=0.04), and the risk for operation in the FP group tended to be lower than that in the non-FP group(p=0.06). There was no significant difference in disease-free survival between these groups(p=0.46). Overall survival time in the FP group tended to be longer than that in the non-FP group (p=0.06). In the FP group, 2 patients with Grade 3 adverse events were recognized, and the completion rate of FP therapy was 77%. Although we analyzed a small number of patients in this study, postoperative adjuvant chemotherapy using FP does not contribute to the prevention of recurrence in esophageal cancer patients with lymph node metastasis.

Usefulness of indocyanine green angiography for evaluation of blood supply in a reconstructed gastric tube during esophagectomy.

We report a case of necrosis of a reconstructed gastric tube in a 77-year-old male patient who had undergone esophagectomy. At the time of admission, the patient had active gastric ulcers, but these were resolved by treatment with a proton pump inhibitor. Subtotal esophagectomy with gastric tube reconstruction was performed. Visually, the reconstructed gastric tube appeared to be well perfused with blood. Using indocyanine green (ICG) fluorescence imaging the gastroepiploic vessels were well enhanced and no enhancement was visable 3 to 4 cm from the tip of the gastric tube. Four days after esophagectomy, gastric tube necrosis was confirmed, necessitating a second operation. The necrosis of the gastric tube matched the area that had been shown to lack blood perfusion by ICG angiography imaging. It seems that ICG angiography is useful for the evaluation of perfusion in a reconstructed gastric tube.

Interaction and transport of kynurenic acid via human organic anion transporters hOAT1 and hOAT3.

Kynurenic acid, a catabolite of tryptophan, is suggested to be involved in schizophrenia, and is known to be a uremic toxin, although there is little information about the mechanism of its disposition. In this study, we performed uptake experiment using Xenopus laevis oocyte expression system to examine the transport of kynurenic acid by human organic anion transporters hOAT1 (SLC22A6) and hOAT3 (SLC22A8), which mediate the transport of organic anions in the brain and kidney. The uptake of p-aminohippurate in hOAT1-expressing oocytes and of estrone sulfate in hOAT3-expressing oocytes was strongly inhibited by kynurenic acid, and other tryptophan catabolites, kynurenine and quinolinic acid, showed moderate and no inhibition, respectively. The apparent 50% inhibitory concentrations of kynurenic acid were estimated to be 12.9 µM for hOAT1, and 7.76 µM for hOAT3. Both hOAT1 and hOAT3 markedly stimulated the uptake of kynurenic acid into oocytes, and the K(m) values of the transport were calculated to be 5.06 µM and 4.86 µM, respectively. The transport efficiencies of kynurenic acid by hOAT1 and hOAT3 were comparable to those of p-aminohippurate and estrone sulfate, respectively. Probenecid inhibited kynurenic acid transport by hOAT1 and hOAT3. These findings show the interaction of kynurenic acid with hOAT1 and hOAT3, and that kynurenic acid is their substrate. It is suggested that these transporters are involved in the disposition of kynurenic acid.

Stereoselective inhibitory effect of flurbiprofen, ibuprofen and naproxen on human organic anion transporters hOAT1 and hOAT3.

Nonsteroidal anti-inflammatory drugs (NSAIDs) delay the renal excretion of antifolate methotrexate by inhibiting human organic anion transporters hOAT1 (SLC22A6) and hOAT3 (SLC22A8). In this study, uptake experiments were performed using Xenopus laevis oocytes to assess stereoselectivity in the inhibitory characteristics of flurbiprofen, ibuprofen and naproxen against hOAT1 and hOAT3. Uptake of p-aminohippurate by hOAT1 was inhibited by each enantiomer of the three NSAIDs, and the inhibitory effect was superior in each (S)-enantiomer around 10 µM. The apparent 50% inhibitory concentrations were estimated to be 0.615 µM for (S)-flurbiprofen, 2.84 µM for (S)-ibuprofen and 1.93 µM for (S)-naproxen, and these values were significantly lower than those of the respective (R)-enantiomers [(R)-flurbiprofen: 2.35 µM, (R)-ibuprofen: 6.14 µM, (R)-naproxen: 5.26 µM]. Furthermore, the (S)-NSAIDs at 3 µM reduced methotrexate accumulation in hOAT1-expressing oocytes more strongly than the corresponding (R)-enantiomers. All enantiomers inhibited hOAT3-mediated transport of estrone sulfate and methotrexate, but there was no difference between both enantiomers of each NSAID in the inhibitory potencies. Eadie-Hofstee plot analysis showed that (S)-flurbiprofen and (R)-flurbiprofen inhibited hOAT1 and hOAT3 in a competitive manner. These findings represent the stereoselective inhibitory potencies of flurbiprofen, ibuprofen and naproxen on hOAT1, and the (S)-enantiomers are greater. In contrast, stereoselectivity was not recognized in their inhibitory effect on hOAT3.

Inhibitory effect of caffeic acid on human organic anion transporters hOAT1 and hOAT3: a novel candidate for food-drug interaction.

Several kinds of food have been shown to influence the absorption and metabolism of drugs, although there is little information about their effect on the renal excretion of drugs. In this study, we performed uptake experiments using Xenopus laevis oocytes to assess the inhibitory effects of chlorogenic acid, caffeic acid and quinic acid, which are contained in coffee, fruits and vegetables, on human organic anion transporters hOAT1 and hOAT3; these transporters mediate renal tubular uptake of anionic drugs from blood. Injection of hOAT1 and hOAT3 cRNA into oocytes stimulated uptake of typical substrates of hOAT1 and hOAT3 (p-aminohippurate and estrone sulfate, respectively); among the three compounds tested, caffeic acid most strongly inhibited these transporters. The apparent 50% inhibitory concentrations of caffeic acid were estimated to be 16.6 µM for hOAT1 and 5.4 µM for hOAT3. Eadie-Hofstee plot analysis showed that caffeic acid inhibited both transporters in a competitive manner. In addition to the transport of p-aminohippurate and estrone sulfate, that of antifolates and antivirals was inhibited by caffeic acid. These findings show that caffeic acid has inhibitory potential against hOAT1 and hOAT3, suggesting that renal excretion of their substrates could be affected in patients consuming a diet including caffeic acid.

Inhibitory effect of selective cyclooxygenase-2 inhibitor etoricoxib on human organic anion transporter 3 (hOAT3).

It is well known that nonsteroidal anti-inflammatory drugs (NSAIDs) delay the elimination of methotrexate. One of the mechanisms is thought to be inhibition of methotrexate uptake via human organic anion transporter 3 (hOAT3, SLC22A8) in the renal proximal tubule by NSAIDs. In this study, we evaluated the inhibitory effects of selective cyclooxygenase-2 inhibitor etoricoxib on hOAT3 by uptake experiments using Xenopus laevis oocytes. The injection of hOAT3 cRNA stimulated the uptake of methotrexate into the oocytes, and its transport was inhibited by etoricoxib. Etoricoxib inhibited estrone sulfate uptake by hOAT3 dose dependently, and the 50% inhibitory concentration was estimated to be 9.8 µM. Eadie-Hofstee plot analysis showed that etoricoxib inhibited hOAT3 in a competitive manner. These findings show that etoricoxib has inhibitory effect on hOAT3, and that the potential is comparable to that of traditional NSAIDs.