The impact of COVID-19 on the diagnosis and treatment of HCC: analysis of a nationwide registry for advanced liver diseases (REAL)

The number of cancer cases diagnosed during the coronavirus disease 2019 (COVID-19) pandemic has decreased. This study investigated the impact of the pandemic on the clinical practice of hepatocellular carcinoma (HCC) using a novel nationwide REgistry for Advanced Liver diseases (REAL) in Japan. We retrieved data of patients initially diagnosed with HCC between January 2018 and December 2021. We adopted tumor size as the primary outcome measure and compared it between the pre-COVID-19 (2018 and 2019) and COVID-19 eras (2020 and 2021). We analyzed 13,777 patients initially diagnosed with HCC (8074 in the pre-COVID-19 era and 5703 in the COVID-19 era). The size of the maximal intrahepatic tumor did not change between the two periods (mean [SD] = 4.3 [3.6] cm and 4.4 [3.6] cm), whereas the proportion of patients with a single tumor increased slightly from 72.0 to 74.3%. HCC was diagnosed at a similar Barcelona Clinic Liver Cancer stage. However, the proportion of patients treated with systemic therapy has increased from 5.4 to 8.9%. The proportion of patients with a non-viral etiology significantly increased from 55.3 to 60.4%. Although the tumor size was significantly different among the etiologies, the subgroup analysis showed that the tumor size did not change after stratification by etiology. In conclusion, the characteristics of initially diagnosed HCC remained unchanged during the COVID-19 pandemic in Japan, regardless of differences in etiology. A robust surveillance system should be established particularly for non-B, non-C etiology to detect HCC in earlier stages.

Development of a transformer model for predicting the prognosis of patients with hepatocellular carcinoma after radiofrequency ablation

INTRODUCTION

Radiofrequency ablation (RFA) is a widely accepted, minimally invasive treatment modality for patients with hepatocellular carcinoma (HCC). Accurate prognosis prediction is important to identify patients at high risk for cancer progression/recurrence after RFA. Recently, state-of-the-art transformer models showing improved performance over existing deep learning-based models have been developed in several fields. This study was aimed at developing and validating a transformer model to predict the overall survival in HCC patients with treated by RFA.

METHODS

We enrolled a total of 1778 treatment-naïve HCC patients treated by RFA as the first-line treatment. We developed a transformer-based machine learning model to predict the overall survival in the HCC patients treated by RFA and compared its predictive performance with that of a deep learning-based model. Model performance was evaluated by determining the Harrel's c-index and validated externally by the split-sample method.

RESULTS

The Harrel's c-index of the transformer-based model was 0.69, indicating its better discrimination performance than that of the deep learning model (Harrel's c-index, 0.60) in the external validation cohort. The transformer model showed a high discriminative ability for stratifying the external validation cohort into two or three different risk groups (p < 0.001 for both risk groupings). The model also enabled output of a personalized cumulative recurrence prediction curve for each patient.

CONCLUSIONS

We developed a novel transformer model for personalized prediction of the overall survival in HCC patients after RFA treatment. The current model may offer a personalized survival prediction schema for patients with HCC undergoing RFA treatment.

Clinical utility of postablation liver tumor biopsy and possibility of gene mutation analysis

AIM

Radiofrequency ablation (RFA) is regarded as a first-line treatment for hepatocellular carcinoma (HCC) at an early stage. When treated with RFA, tumor biopsy may not be performed due to the risk of neoplastic seeding. We previously revealed that the risk of neoplastic seeding is significantly reduced by performing biopsies after RFA. In this study, we investigated the possibility of pathological evaluation and gene mutation analysis of post-RFA tumor specimens.

METHODS

Radiofrequency ablation was undertaken on diethylnitrosamine-induced mouse liver tumor, and tumor samples with or without RFA were subjected to whole exome sequencing. Post-RFA human liver tumor specimens were used for detection of TERT promoter mutations and pathological assessment.

RESULTS

The average somatic mutation rate, sites of mutation, and small indels and base transition patterns were comparable between the nontreated and post-RFA tumors. We identified 684 sites of nonsynonymous somatic substitutions in the nontreated tumor and 704 sites of nonsynonymous somatic substitutions in the post-RFA tumor, with approximately 85% in common. In the human post-RFA samples, the TERT promoter mutations were successfully detected in 40% of the cases. Pathological evaluation was possible with post-RFA specimens, and in one case, the diagnosis of adenocarcinoma was made.

CONCLUSION

Our findings suggest that post-RFA liver tumor biopsy is a useful and safe method for obtaining tumor samples that can be used for gene mutation analysis and for pathological assessment.

Proton Beam Therapy versus Radiofrequency Ablation for Patients with Treatment-Naïve Single Hepatocellular Carcinoma: A Propensity Score Analysis

Introduction

Proton beam therapy (PBT) is known to be an effective locoregional treatment for hepatocellular carcinoma (HCC). However, few comparative studies in treatment-naïve cases have been reported. The aim of this study was to compare the survival outcomes of PBT with those of radiofrequency ablation (RFA) in patients with treatment-naïve solitary HCC.

Methods

Ninety-five consecutive patients with treatment-naïve HCC, a single nodule measuring ≤5 cm in diameter, and a Child-Pugh score of ≤8 who were treated with PBT at the University of Tsukuba Hospital between 2001 and 2013 were enrolled in the study. In addition, 836 patients with treatment-naïve HCC treated by RFA at the University of Tokyo Hospital during the same period were analyzed as controls. Recurrence-free survival (RFS) and overall survival (OS) were compared in 83 patient pairs after propensity score matching.

Results

The 1-year, 3-year, and 5-year RFS rates were 86.6%, 49.5%, and 35.5%, respectively, in the PBT group and 59.5%, 34.0%, and 20.9% in the RFA group (p = 0.058); the respective OS rates were 97.6%, 77.8%, and 57.1% in the PBT group and 95.1%, 81.7%, and 67.7% in the RFA group (p = 0.16). Regarding adverse effects, no grade 3 or higher adverse events were noted in the PBT; however, two grade 3 adverse events occurred within 30 days of RFA in the RFA group: one hemoperitoneum and one hemothorax.

Discussion

After propensity score matching, PBT showed no significant difference in RFS and OS compared to RFA. PBT can be an alternative for patients with solitary treatment-naïve HCC.

Machine learning for individualized prediction of hepatocellular carcinoma development after the eradication of hepatitis C virus with antivirals

BACKGROUND AND AIMS

Accurate risk stratification for hepatocellular carcinoma (HCC) after achieving a sustained viral response (SVR) is necessary for optimal surveillance. We aimed to develop and validate a machine learning (ML) model to predict the risk of HCC after achieving an SVR in individual patients.

METHODS

In this multicenter cohort study, 1742 patients with chronic hepatitis C who achieved an SVR were enrolled. Five ML models were developed including DeepSurv, gradient boosting survival analysis, random survival forest (RSF), survival support vector machine, and a conventional Cox proportional hazard model. Model performance was evaluated using Harrel' c-index and was externally validated in an independent cohort (977 patients).

RESULTS

During the mean observation period of 5.4 years, 122 patients developed HCC (83 in the derivation cohort and 39 in the external validation cohort). The RSF model showed the best discrimination ability using seven parameters at the achievement of an SVR with a c-index of 0.839 in the external validation cohort and a high discriminative ability when the patients were categorized into three risk groups (P <0.001). Furthermore, this RSF model enabled the generation of an individualized predictive curve for HCC occurrence for each patient with an app available online.

CONCLUSIONS

We developed and externally validated an RSF model with good predictive performance for the risk of HCC after an SVR. The application of this novel model is available on the website. This model could provide the data to consider an effective surveillance method. Further studies are needed to make recommendations for surveillance policies tailored to the medical situation in each country.

IMPACT AND IMPLICATIONS

A novel prediction model for HCC occurrence in patients after hepatitis C virus eradication was developed using machine learning algorithms. This model, using seven commonly measured parameters, has been shown to have a good predictive ability for HCC development and could provide a personalized surveillance system.

Steroid administration for ischemic complications after radiofrequency ablation: A retrospective study

AIM

The aim of this study was to evaluate the effects of steroids on ischemic complications after radiofrequency ablation.

METHODS

A total of 58 patients with ischemic complications were divided into two groups according to corticosteroid use or non-use.

RESULTS

A total of 13 patients who were administered steroids had a shorter duration of fever than those who were not administered steroids (median 6.0 vs. 2.0 days; p < 0.001). Linear regression analysis showed that steroid administration was associated with a reduction of 3.9 days in the duration of fever (p = 0.008).

CONCLUSIONS

Steroid administration for ischemic complications after radiofrequency ablation may reduce the risk of fatal outcomes by blocking systemic inflammatory reactions.

Current status of primary liver cancer and decompensated cirrhosis in Japan: launch of a nationwide registry for advanced liver diseases (REAL)

BACKGROUND

We developed a nationwide database that stores data of patients with primary liver cancer (PLC) and decompensated cirrhosis (DC) on an admission basis.

METHODS

A database was constructed using the National Clinical Database, a nationwide registry platform for various diseases in Japan. Mutual data exchange was possible with the Nationwide Follow-up Survey of Primary Liver Cancer in Japan by the Liver Cancer Study Group of Japan. The stored data on the admission of patients with PLC, DC, or both, included treatment details as well as patient characteristics.

RESULTS

A total of 37,705 admissions (29,489 PLC, 10,077 DC, and 1862 for both) in 21,376 patients from 224 hospitals were analyzed. The proportions of patients with hepatitis B, hepatitis C, and non-viral etiology were 11.9%, 36.2%, and 42.6%, respectively, in PLC, and 7.5%, 23.8%, and 55.0%, respectively, in DC. The mean ages (± standard deviation) on admission with PLC and DC were 73 ± 10 and 68 ± 13 years, respectively. The Barcelona Clinic Liver Cancer (BCLC) stage for PLC was 0, A, B, C, and D in 22.0%, 17.1%, 29.6%, 15.1%, and 5.1%, respectively. Treatment modalities for PLC were resection, ablation, transarterial chemoembolization, and systemic therapy in 18.4%, 22.8%, 33.7%, and 11.4%, respectively. A vasopressin receptor V2 antagonist was used in 38.2% in addition to conventionally used loop diuretics and aldosterone antagonists for DC.

CONCLUSIONS

The distribution of treatment options for PLC on admission differed from that of the initial treatment. Newly introduced drugs are widely used in patients with DC.

Improved prognosis of hepatitis C-related hepatocellular carcinoma in the era of direct-acting antivirals

The prognostic impact of direct‐acting antivirals (DAAs) on patients with hepatitis C‐related hepatocellular carcinoma (C‐HCC) is still unclear. This study aimed to evaluate the prognosis of C‐HCC in the DAA era. We enrolled 1237 consecutive patients with treatment‐naive C‐HCC who underwent radical radiofrequency ablation between 1999 and 2019. We also enrolled 350 patients with nonviral HCC as controls. We divided these patients into three groups according to the year of initial treatment: 1999–2005 (cohort 1), 2006–2013 (cohort 2), and 2014–2019 (cohort 3). The use of antiviral agents and their effect in patients with C‐HCC was investigated. Overall survival was evaluated for each cohort using the Kaplan‐Meier method and a multivariable Cox proportional hazards regression model. Sustained virologic response (SVR) was achieved in 52 (10%), 157 (26%), and 102 (74%) patients with C‐HCC in cohorts 1–3, respectively. The 3‐ and 5‐year survival rates of patients with C‐HCC were 82% and 59% in cohort 1; 80% and 64% in cohort 2; and 86% and 78% in cohort 3, respectively (p = 0.003). Multivariable analysis adjusted for age, liver function, and tumor extension showed that the prognosis of C‐HCC improved in cohort 3 compared to cohort 1 (adjusted hazard ratio [aHR], 0.49; 95% confidence interval [CI], 0.32–0.73; p < 0.001), whereas the prognosis of nonviral HCC did not improve significantly (aHR, 0.96; 95% CI, 0.59–1.57; p = 0.88). The prognosis of C‐HCC drastically improved with the advent of DAAs.

Infectious complications related to radiofrequency ablation of liver tumors: The role of antibiotics

Background and aim

Prophylactic administration of antibiotics within 24 hours of surgery is recommended to reduce the risk of infection. We conducted a prospective study to compare the efficacy of single administration of antibiotics with a historical control of continuous administration of antibiotics for radiofrequency ablation (RFA) of malignant liver tumors.

Methods

Between February 1, 1999 and November 30, 2010, a total of 6,763 RFA treatments were performed in 2,355 patients, using a protocol with continuous administration of prophylactic antibiotics. On December 1, 2010, we began using a revised protocol with a single administration of prophylactic antibiotics, while continuing to use the old continuous administration protocol for patients who declined the new protocol. Interim analysis was performed to assess the safety of the single administration protocol. Thereafter, from April 1, 2012, all patients were treated using the new protocol. Risk factors for infectious complications of RFA were assessed using logistic regression.

Results

From December 2010 to March 2012, 766 RFA treatments were performed in 663 patients using the new antibiotic protocol. Infectious complications were observed following 4 of these treatments (0.52%). As the upper limit of the confidence interval (CI) resulting from a one-sided binomial test was exactly the prespecified limit of 1.0%, from April 2012 onwards, we treated all patients using the new protocol with single administration of prophylactic antibiotics. A total of 3,547 RFA treatments were performed using the single administration protocol. Univariable logistic regression indicated that prior transcatheter arterial chemoembolization (TACE) and maximal tumor diameter were significant risk factors for infectious complications (P = 0.04 and P < 0.001, respectively). Multivariable analysis indicated that the adjusted hazard ratio of single vs. continuous administration of antibiotics was 1.20 (95% CI: 0.53–2.75; P = 0.66).

Conclusions

The rate of infectious complications related to RFA was acceptably low. Single administration of prophylactic antibiotics did not significantly increase the rate of infectious complications related to RFA, compared with a more intensive antibiotic protocol.

Impact of Obesity and Heavy Alcohol Consumption on Hepatocellular Carcinoma Development after HCV Eradication with Antivirals

BACKGROUND AND AIMS

It remains unclear whether obesity increases the risk of hepatocellular carcinoma (HCC) in patients with chronic hepatitis C who achieved a sustained virological response (SVR) with antiviral therapy.

METHODS

In this multicenter cohort study, we enrolled patients with chronic hepatitis C who achieved SVR with interferon (IFN)-based therapy (IFN group) or direct-acting antiviral (DAA) therapy (DAA group) between January 1, 1990, and December 31, 2018. The patients underwent regular surveillance for HCC. Cumulative incidence of and the risk factors for HCC development after SVR were assessed using the Kaplan-Meier method and Cox proportional hazard regression analysis, respectively.

RESULTS

Among 2,055 patients (840 in the IFN group and 1,215 in the DAA group), 75 developed HCC (41 in the IFN group and 34 in the DAA group) during the mean observation period of 4.1 years. The incidence rates of HCC at 1, 2, and 3 years were 1.2, 1.9, and 3.0%, respectively. Multivariate analysis revealed that in addition to older age, lower albumin level, lower platelet count, higher alpha-fetoprotein level, and absence of dyslipidemia, obesity (body mass index ≥25 kg/m²) and heavy alcohol consumption (≥60 g/day) were independent risk factors for HCC development, with adjusted hazard ratio (HR) of 2.53 (95% confidence interval [CI]: 1.51-4.25) and 2.56 (95% CI: 1.14-5.75), respectively. The adjusted HR was not significant between the 2 groups (DAA vs. IFN; HR 1.19, 95% CI: 0.61-2.33).

CONCLUSIONS

Obesity and heavy alcohol consumption increased the risk of HCC development after SVR.

Post-treatment cell-free DNA as a predictive biomarker in molecular-targeted therapy of hepatocellular carcinoma

BACKGROUND

Liquid biopsies, particularly those involving circulating tumor DNA (ctDNA), are rapidly emerging as a non-invasive alternative to tumor biopsies. However, clinical applications of ctDNA analysis in hepatocellular carcinoma (HCC) have not been fully elucidated.

METHODS

We measured the amount of plasma-derived cell-free DNA (cfDNA) in HCC patients before (n = 100) and a few days after treatment (n = 87), including radiofrequency ablation, transarterial chemoembolization, and molecular-targeted agents (MTAs), and prospectively analyzed their associations with clinical parameters and prognosis. TERT promoter mutations in cfDNA were analyzed using droplet digital PCR. Furthermore, we performed a comprehensive mutational analysis of post-treatment cfDNA via targeted ultra-deep sequencing (22,000× coverage) in a panel of 275 cancer-related genes in selected patients.

RESULTS

Plasma cfDNA levels increased significantly according to HCC clinical stage, and a high cfDNA level was independently associated with a poor prognosis. TERT promoter mutations were detected in 45% of all cases but were not associated with any clinical characteristics. cfDNA levels increased significantly a few days after treatment, and a greater increase in post-treatment cfDNA levels was associated with a greater therapeutic response to MTAs. The detection rate of TERT mutations increased to 57% using post-treatment cfDNA, suggesting that the ctDNA was enriched. Targeted ultra-deep sequencing using post-treatment cfDNA after administering lenvatinib successfully detected various gene mutations and obtained promising results in lenvatinib-responsive cases.

CONCLUSIONS

Post-treatment cfDNA analysis may facilitate the construction of biomarkers for predicting MTA treatment effects.

Axin2+ Peribiliary Glands in the Periampullary Region Generate Biliary Epithelial Stem Cells That Give Rise to Ampullary Carcinoma

BACKGROUND & AIMS

Peribiliary glands (PBGs), clusters of epithelial cells residing in the submucosal compartment of extrahepatic bile ducts, have been suggested as biliary epithelial stem/progenitor cell niche; however, evidence to support this claim is limited because of a lack of PBG-specific markers. We therefore sought to identify PBG-specific markers to investigate the potential role of PBGs as stem/progenitor cell niches, as well as an origin of cancer.

METHODS

We examined the expression pattern of the Wnt target gene Axin2 in extrahepatic bile ducts. We then applied lineage tracing to investigate whether Axin2-expressing cells from PBGs contribute to biliary regeneration and carcinogenesis using Axin2-Cre^ERT mice.

RESULTS

Wnt signaling activation, marked by Axin2, was limited to PBGs located in the periampullary region. Lineage tracing showed that Axin2-expressing periampullary PBG cells are capable of self-renewal and supplying new biliary epithelial cells (BECs) to the luminal surface. Additionally, the expression pattern of Axin2 and the mature ductal cell marker CK19 were mutually exclusive in periampullary region, and fate tracing of CK19⁺ luminal surface BECs showed gradual replacement by CK19^- cells, further supporting the continuous replenishment of new BECs from PBGs to the luminal surface. We also found that Wnt signal enhancer R-spondin3 secreted from Myh11-expressing stromal cells, corresponding to human sphincter of Oddi, maintained the periampullary Wnt signal-activating niche. Notably, introduction of PTEN deletion into Axin2⁺ PBG cells, but not CK19⁺ luminal surface BECs, induced ampullary carcinoma whose development was suppressed by Wnt inhibitor.

CONCLUSION

A specific cell population receiving Wnt-activating signal in periampullary PBGs functions as biliary epithelial stem/progenitor cells and also the cellular origin of ampullary carcinoma.

Improved liver function in patients with cirrhosis due to chronic hepatitis C virus who achieve sustained virologic response is not accompanied by increased liver volume

Background

Serum albumin level improves in patients with chronic hepatitis C virus (HCV) infection who achieve sustained virologic response (SVR) with antiviral therapy. However, it remains controversial whether liver volume increases along with SVR.

Methods

Patients with chronic HCV infection with a history of hepatocellular carcinoma (HCC) who achieved SVR with anti-HCV treatment from March 2003 to November 2017 were enrolled. Patients were followed up with periodic computed tomography (CT) scans to detect HCC recurrence. Patients who underwent treatment for HCC recurrence within 1 year after initiation of anti-HCV treatment were excluded. Laboratory data, including alanine aminotransferase (ALT) level, serum albumin level, and platelet count, were collected at baseline and timepoints after treatment initiation. Liver volume was evaluated at baseline and 24 and 48 weeks after treatment initiation using a CT volume analyzer. A linear mixed-effects model was applied to analyze the chronologic change in liver volume. The correlations between changes in ALT level, albumin level, and liver volume were also evaluated.

Results

Of 108 enrolled patients, 78 had cirrhosis. Serum albumin level continued to increase through 48 weeks after treatment initiation. A significant increase in liver volume was observed only in patients without cirrhosis (P = 0.005). There was a significant correlation between ALT level decrease and albumin level increase (P = 0.018).

Conclusions

Improved liver albumin production with SVR was contributed by improved liver cell function rather than increased liver volume in patients with cirrhosis.

A Novel Non-invasive Method for Predicting Liver Fibrosis by Quantifying the Hepatic Vein Waveform

The hepatic vein (HV) waveform by Doppler ultrasound reflects the severity of liver fibrosis. We conducted a proof-of-concept study of a new method for quantifying the HV waveform. We calculated the coefficient of variation (CV) of the HV flow velocity and created a new index "q-HV" (quantified HV) and analyzed its performance for predicting histologic liver fibrosis in 114 patients with chronic liver disease. The CV of the HV flow velocity was well associated with flattening of the waveform and the q-HV significantly increased with the progression of liver fibrosis. The areas under the curve for the prediction of fibrosis stage were 0.732 for F2, 0.772 for F3 and 0.805 for F4. Combined q-HV and FIB-4 index (widely used liver fibrosis score) increased the diagnostic accuracy for liver fibrosis. The q-HV showed good accuracy for predicting liver fibrosis; thus, q-HV is feasible and acceptable as a non-invasive tool for predicting liver fibrosis.

Liver stiffness measurements in chronic hepatitis C: Treatment evaluation and risk assessment

BACKGROUND AND AIM

Liver stiffness (LS), measured by transient elastography, has been validated as a non-invasive surrogate for liver fibrosis.

METHODS

We investigated the long-term predictive ability of LS for hepatocellular carcinoma (HCC) development and overall survival in 1146 patients with chronic hepatitis C by using LS value at enrollment. We also investigated chronological changes in LS based on antiviral therapy and its outcome in 752 patients.

RESULTS

During the mean follow-up period of 6.6 years, 190 patients developed HCC. Cumulative HCC incidence rates at 5 years were clearly stratified as 1.7% in the ≤ 5 kPa, 3.3% in 5.1-10 kPa, 16.7% in 10.1-15 kPa, 24.4% in 15.1-20 kPa, 36.3% in 20.1-25 kPa, and 43.7% in > 25 kPa subgroups (P < 0.001). Overall survival was also stratified: 10-year survival rates were 99.3% in the ≤ 5 kPa, 95.4% in 5.1-10 kPa, 81.4% in 10.1-15 kPa, 79.5% in 15.1-20 kPa, 66.1% in 20.1-25 kPa, and 49.1% in > 25 kPa subgroups (P < 0.001). LS decreased at a rate of 8.1% per year in those who achieved sustained virological responses, but increased at 0.1% per year in those who could not achieve sustained virological response instead of antiviral therapy, and increased at 3.7% per year in those who did not undergo antiviral therapy.

CONCLUSIONS

Liver stiffness measurements can be useful in the prediction of HCC development and overall survival and in the evaluation of chronological changes in liver fibrosis grade during and after antiviral therapy.

Ischemic complications after percutaneous radiofrequency ablation of liver tumors: Liver volume loss and recovery

AIM

The liver regrows after acute liver injury and liver resection. However, it is not clear whether the liver regenerates in advanced cirrhosis. This study aimed to evaluate the clinical course of, and liver volume change after, ischemic liver complications caused by radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC).

METHODS

We enrolled 35 patients with ischemic complications after RFA. Ischemic complications were defined as rapid elevation of aspartate aminotransferase (AST) to over 500 U/L, with typical radiological findings. Patient characteristics and the ischemic liver volume were investigated. Long-term liver volume changes at 3-8 months after ischemic complications were also assessed in 32 patients. We also assessed the overall survival rate after ischemic complications.

RESULTS

The median value of peak AST was 798 U/L (range, 531-4096 U/L). The median ischemic liver volume relative to the functional liver volume before RFA was 13% (range, 3.1-46.5%). There was a strong correlation between the peak AST value and the ischemic liver volume (r = 0.84, P < 0.001). The liver volume recovered to some extent in 18 of 32 (56%) patients after ischemic complications. The survival rate after ischemic complications was 45.7% at 5 years and correlated with the functional liver volume after ischemic complications (P = 0.02).

CONCLUSIONS

Ischemic complications after RFA can lead to massive liver parenchymal loss. Although the liver volume recovered to some extent in the majority of our patients, ischemic liver complications after RFA should be avoided to improve the overall survival rate.

Identification of liver fibrosis using the hepatic vein waveform in patients with Fontan circulation

AIM

Liver fibrosis caused by congestive hepatopathy has emerged as an important complication after Fontan procedure. We evaluated the utility of the hepatic vein (HV) waveform using Doppler ultrasound for identification of liver fibrosis in Fontan patients.

METHODS

We investigated the HV waveforms in 41 Fontan patients and assessed correlations with clinical parameters, liver fibrosis markers, and hemodynamic data.

RESULTS

Based on our preliminary analysis of 64 adult patients with chronic liver disease who underwent liver biopsy, we classified HV waveforms into five types with reference to the degree of flattening (from type 1, normal triphasic waveform; to type 5, a monophasic waveform indicating cirrhosis), and confirmed a significant correlation between waveform pattern and fibrosis stage. Notably, we detected HV waveforms in all of the Fontan patients and classified them into five types. The HV waveform pattern positively correlated with γ-glutamyl transferase and hyaluronic acid levels, and negatively correlated with albumin level and platelet count, but did not correlate with central venous pressure or brain natriuretic peptide level, suggesting that HV waveform could reflect pathophysiological changes in the liver without being affected by hepatic congestion. The highest area under the receiver operating characteristic curve of the HV waveform for detecting advanced liver fibrosis, as defined by ultrasonic findings and clinical features, was 0.829 (81.8% sensitivity, 73.3% specificity), which was higher than that of other non-invasive fibrosis markers.

CONCLUSIONS

Hepatic vein waveforms change in accordance with liver fibrosis progression in Fontan patients, and can be a useful indicator of liver fibrosis after the Fontan procedure.

Impact of direct-acting antivirals on early recurrence of HCV-related HCC: Comparison with interferon-based therapy

BACKGROUND & AIMS

It remains controversial whether direct-acting antivirals (DAAs) accelerate the recurrence of hepatitis C-related hepatocellular carcinoma (HCC) after curative therapy. This study aimed to evaluate HCC recurrence after DAA treatment of chronic hepatitis C.

METHODS

We enrolled patients with a history of successful radiofrequency ablation treatment for hepatitis C-related HCC who received antiviral therapy with DAAs (DAA group: 147 patients) or with interferon (IFN)-based therapy (IFN group: 156 patients). We assessed HCC recurrence rates from the initiation of antiviral therapy using the Kaplan-Meier method and evaluated risk factors for HCC recurrence by multivariate Cox proportional hazard regression analysis. The recurrence pattern was categorized as follows: intrahepatic recurrence with a single tumor <2 cm (stage 0), a single tumor or up to 3 tumors ≤3 cm (stage A), multinodular (stage B), and extrahepatic metastasis or macrovascular invasion (stage C).

RESULTS

The recurrence rates at 1 and 2 years were 39% and 61% in the IFN group and 39% and 60% in the DAA group, respectively (p = 0.43). Multivariate analysis identified higher lens culinaris agglutinin-reactive fraction of alpha-fetoprotein level, a history of multiple HCC treatments, and a shorter interval between HCC treatment and initiation of antiviral therapy as independent risk factors for HCC recurrence. HCC recurrence in stage 0, A, B, and C was found in 56 (41%), 60 (44%), 19 (14%), and 1 (0.7%) patients in the IFN group and 35 (44%), 32 (40%), 11 (14%), and 2 (2.5%) patients in the DAA group, respectively (p = 0.70).

CONCLUSIONS

HCC recurrence rates and patterns after initiation of antiviral therapy did not differ between patients who received IFN-based therapy and DAA therapy.

LAY SUMMARY

We detected no significant difference in early hepatocellular carcinoma (HCC) recurrence rates and patterns between patients who received interferon-based and direct-acting antiviral therapy after HCC treatment. High lens culinaris agglutinin-reactive fraction of alpha-fetoprotein level, short recurrence-free period, and a history of multiple HCC treatments were independent risk factors for early HCC recurrence after the initiation of antiviral therapy.

Disappearance of perihepatic lymph node enlargement after hepatitis C viral eradication with direct-acting antivirals

Perihepatic lymph node enlargement (PLNE) which has been shown to be negatively associated with hepatocellular carcinoma (HCC) occurrence is frequently observed in chronic liver disease; however, changes in the state of perihepatic lymph nodes after eradication of hepatitis C virus (HCV) have not been investigated yet. We aimed to evaluate this issue. We enrolled 472 patients with chronic HCV infection who achieved viral eradication with direct-acting antivirals (DAA). We investigated whether the status of perihepatic lymph nodes changed before and after HCV eradication (primary endpoint). We also evaluated the association between PLNE and clinical findings such as liver fibrosis or hepatocellular injury before HCV eradication (secondary endpoint). Perihepatic lymph node enlargement was detected in 164 of 472 (34.7%) patients before DAA treatment. Surprisingly, disappearance of PLNE was observed in 23.8% (39 patients) of all PLNE-positive patients after eradication of HCV. Disappearance of PLNE was not associated with baseline clinical parameters or changing rates of clinical findings before and after DAA treatment. At baseline, presence of PLNE was significantly associated with a lower serum HCV-RNA level (P = .03), a higher serum AST level (P = .004) and a higher ALT level (P < .001) after adjustment for sex and age. In conclusion, PLNEs became undetectable after DAA treatment in 23.8% of PLNE-positive patients. Further study with a longer follow-up period is needed to clarify the clinical importance of this phenomenon especially in relationship with the risk of HCC development.

Hepatic IRS1 and ß-catenin expression is associated with histological progression and overt diabetes emergence in NAFLD patients

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a risk factor for type 2 diabetes. Our aim was to investigate the relationship between NAFLD and impaired glucose metabolism in terms of insulin receptor substrate 1 and 2 (IRS1 and IRS2) expression in the liver.

METHODS

Liver biopsy was performed at the University of Tokyo Hospital between November 2011 and March 2016 on 146 patients with NAFLD who were not being treated with any diabetes or dyslipidemia drugs. Among them, 63 underwent liver biopsy after an overnight fast, and 83 at 5 h after an oral glucose tolerance test (OGTT). Differences in messenger RNA (mRNA) levels of several glucose metabolism-related factors were determined and correlated with hepatic histological changes assessed by NAFLD activity score. We prospectively followed up with the patients until May 2017.

RESULTS

Hepatic necroinflammation was significantly correlated with serum insulin levels and inversely correlated with IRS1 mRNA levels. In specimens obtained after an OGTT, hepatic necroinflammation and IRS1 expression correlated significantly with both peripheral and hepatic insulin resistance. We also found that hepatic β-catenin and glucokinase mRNA levels were elevated in patients undergoing liver biopsy after an OGTT, especially in those with less hepatic necroinflammation and a lower degree of fibrosis. A prospective cohort study showed that ballooning is the most significant risk factor for developing diabetes.

CONCLUSIONS

The decreased hepatic expression of IRS1 and β-catenin in NAFLD is linked to histological progression such as ballooning, and might lead to diabetes as a result of impaired glucose metabolism.

Comparison of improved prognosis between hepatitis B- and hepatitis C-related hepatocellular carcinoma

AIM

Treatment strategies for hepatocellular carcinoma (HCC) have been advanced. The aim of this study was to compare the change of the prognosis between hepatitis B-related HCC (B-HCC) and hepatitis C-related HCC (C-HCC) in the last two decades.

METHODS

We enrolled 166 B-HCC patients who underwent percutaneous ablation between 1990 and 2009. Patients were divided into three groups according to the treatment time period: 1990-1995 (cohort 1, n = 19), 1996-2002 (cohort 2, n = 49) and 2003-2009 (cohort 3, n = 98). We enrolled 1219 C-HCC patients who underwent percutaneous ablation during the same period (n = 190, 413 and 616, respectively.). Interferon and nucleoside/nucleotide analog use was investigated. Prognosis was evaluated for each cohort using the Kaplan-Meier method and a multivariate Cox proportional hazard regression model.

RESULTS

Two (11%), 24 (49%) and 80 (82%) B-HCC patients received nucleoside/nucleotide analogs during the follow-up period in cohorts 1-3, respectively. Among them 1, 18 and 62 patients achieved viral remission, respectively. Thirty-four (18%), 35 (8%) and 84 (14%) C-HCC patients received interferon therapy, respectively. The 5-year B-HCC (P < 0.001) survival rates were 52.6%, 61.1% and 81.6% for cohorts 1-3, respectively. However, the survival rates were 55.6%, 58.8% and 61.1% for C-HCC (P = 0.12), respectively. The B-HCC prognosis improved dramatically (P < 0.001) over time, whereas the prognosis of C-HCC improved moderately (P = 0.01).

CONCLUSION

The prognosis of B-HCC has improved dramatically over time, whereas that of C-HCC has improved moderately.

Sarcopenia, intramuscular fat deposition, and visceral adiposity independently predict the outcomes of hepatocellular carcinoma

BACKGROUND & AIMS

Obesity defined by body mass index (BMI) significantly increases the risk of hepatocellular carcinoma (HCC). In contrast, not only obesity but also underweight is associated with poor prognosis in patients with HCC. Differences in body composition rather than BMI were suggested to be true determinants of prognosis. However, this hypothesis has not been demonstrated conclusively.

METHODS

We measured skeletal muscle index (SMI), mean muscle attenuation (MA), visceral adipose tissue index, subcutaneous adipose tissue index, and visceral to subcutaneous adipose tissue area ratios (VSR) via computed tomography in a large-scale retrospective cohort of 1257 patients with different stages of HCC, and comprehensively analyzed the impact of body composition on the prognoses.

RESULTS

Among five body composition components, low SMI (called sarcopenia), low MA (called intramuscular fat [IMF] deposition), and high VSR (called visceral adiposity) were significantly associated with mortality, independently of cancer stage or Child-Pugh class. A multivariate analysis revealed that sarcopenia (hazard ratio [HR], 1.52; 95% confidence interval [CI], 1.18-1.96; p=0.001), IMF deposition (HR, 1.34; 95% CI, 1.05-1.71; p=0.020), and visceral adiposity (HR, 1.35; 95% CI, 1.09-1.66; p=0.005) but not BMI were significant predictors of survival. The prevalence of poor prognostic body composition components was significantly higher in underweight and obese patients than in normal weight patients.

CONCLUSIONS

Sarcopenia, IMF deposition, and visceral adiposity independently predict mortality in patients with HCC. Body composition rather than BMI is a major determinant of prognosis in patients with HCC.

Slight elevation of high-sensitivity C-reactive protein to predict recurrence and survival in patients with early stage hepatitis C-related hepatocellular carcinoma

AIM

Hepatocellular carcinoma (HCC) is associated with chronic inflammation derived from various origins. We investigated whether high-sensitivity C-reactive protein (hsCRP) could predict recurrence and survival after curative treatment for early stage hepatitis C virus-related HCC (C-HCC).

METHODS

We enrolled 387 patients with three or fewer C-HCC nodules, none of which exceeded 3 cm, and of Child-Pugh class A or B who underwent radiofrequency ablation. We divided the patients into high and low hsCRP groups based on the optimal cut-off value for recurrence using a split-sample method and maximally selected rank statistics. Differences in recurrence and survival rates were evaluated by the Kaplan-Meier method and the log-rank test. Hazard ratios of hsCRP were adjusted with confounding factors using a multiple Cox regression model. We also assessed the correlations between hsCRP levels and clinical parameters.

RESULTS

The optimal hsCRP cut-off value was 0.08 mg/dL. The cumulative recurrence rates after 5 years in the high and low hsCRP groups were 90.0% and 82.2%, respectively (P = 0.028), and the corresponding survival rates were 50.9% and 71.8%, respectively (P < 0.001). Higher hsCRP was an independent predictor for recurrence (adjusted hazard ratio [aHR], 1.32; 95% confidence interval [CI], 1.03-1.67; P = 0.026) and survival (aHR, 1.59; 95% CI, 1.14-2.22; P = 0.007). hsCRP was correlated with central obesity as well as tumor burden and liver dysfunction.

CONCLUSION

Slight elevation of the hsCRP level, even within the normal range, can predict recurrence and survival after curative treatment among patients with early stage C-HCC.

Serum Alpha-Fetoprotein Has High Specificity for the Early Detection of Hepatocellular Carcinoma After Hepatitis C Virus Eradication in Patients

Alpha-fetoprotein (AFP) has not played a large role in the surveillance of hepatocellular carcinoma due to inadequate sensitivity and specificity for active chronic hepatitis or cirrhosis. The aim of this study was to evaluate the diagnostic accuracy of AFP in small hepatocellular carcinomas after hepatitis C virus eradication to determine the optimal cutoff value. We conducted a case-control study of 29 cases and 58 controls, matched for age, gender, and platelet counts. The AFP cutoff was 5 ng/mL in patients after hepatitis C virus eradication and 17 ng/mL in those without hepatitis C virus eradication. The areas under the receiver operating characteristic curve were 0.86 (95% confidence interval, 0.76-0.96) in patients after hepatitis C virus eradication and 0.83 (95% confidence interval, 0.74-0.91) in those without hepatitis C virus eradication. In patients after hepatitis C virus eradication, the sensitivity and specificity of AFP levels were 24.1% and 100%, respectively, using a cutoff value of 17 ng/mL. Using a lower cutoff value of 5 ng/mL, the sensitivity increased to 75.9%, although the specificity decreased to 89.0%. AFP is a specific tumor marker for the diagnosis of hepatocellular carcinoma after hepatitis C virus eradication when using the optimal cutoff value of 5 ng/mL.

Impact of serum levels of interleukin-6 and adiponectin on all-cause, liver-related, and liver-unrelated mortality in chronic hepatitis C patients

BACKGROUND AND AIM

Various inflammatory cytokines and adipokines have been implicated in hepatitis C virus (HCV)-mediated liver disease, and interleukin-6 (IL-6) and adiponectin may play key roles. In addition, these factors may be associated with chronic hepatitis C (CHC)-induced extrahepatic manifestations. However, little data are available on the role of these factors on future outcomes of CHC patients. This study aims to evaluate the impact of serum levels of IL-6 and adiponectin on all-cause mortality, liver-related mortality, and liver-unrelated mortality.

METHODS

A long-term follow-up study was conducted, consisting of 325 CHC patients, for which we previously reported positive associations between these factors (Serum levels of IL-6 and adiponectin) and hepatocellular carcinoma (HCC) development.

RESULTS

During the follow-up period (mean, 13.0 year), there were 92 events consisting of 91 deaths (liver related, 72; liver unrelated, 19) and 1 liver transplantation due to liver failure. High IL-6 and adiponectin levels, defined as being higher than each median value at baseline, were associated with significantly higher incidences of not only HCC development but also all-cause mortality. Interestingly, high IL-6 was strongly associated with only liver-related mortality, whereas high-serum adiponectin was associated with not only liver-related, but also liver-unrelated mortality. Multivariate analysis identified high IL-6 as an independent risk factor for liver-related mortality and high adiponectin as an independent risk factor for liver-unrelated mortality.

CONCLUSION

High serum levels of IL-6 and adiponectin were associated with higher all-cause and liver-related mortality in CHC patients. In addition, high adiponectin was associated with liver-unrelated mortality. The measurement of these factors may provide information useful for predicting future outcomes in CHC patients.

Frequency of and predictive factors for vascular invasion after radiofrequency ablation for hepatocellular carcinoma

BACKGROUND

Vascular invasion in patients with hepatocellular carcinoma (HCC) is representative of advanced disease with an extremely poor prognosis. The detailed course of its development has not been fully elucidated.

METHODS

We enrolled 1057 consecutive patients with HCC who had been treated with curative intent by radiofrequency ablation (RFA) as an initial therapy from 1999 to 2008 at our department. We analyzed the incidence rate of and predictive factors for vascular invasion. The survival rate after detection of vascular invasion was also analyzed.

RESULTS

During a mean follow-up period of 4.5 years, 6075 nodules including primary and recurrent lesions were treated by RFA. Vascular invasion was observed in 97 patients. The rate of vascular invasion associated with site of original RFA procedure was 0.66% on a nodule basis. The incidence rates of vascular invasion on a patient basis at 1, 3, and 5 years were 1.1%, 5.9%, and 10.4%, respectively. Univariate analysis revealed that tumor size, tumor number, alpha-fetoprotein (AFP), des-gamma-carboxy prothrombin (DCP), and Lens culinaris agglutinin-reactive fraction of alpha-fetoprotein were significant risk predictors of vascular invasion. In multivariate analysis, DCP was the most significant predictor for vascular invasion (compared with a DCP of ≤100 mAu/mL, the hazard ratio was 1.95 when DCP was 101-200 mAu/mL and 3.22 when DCP was >200 mAu/mL). The median survival time after development of vascular invasion was only 6 months.

CONCLUSION

Vascular invasion occurs during the clinical course of patients initially treated with curative intent. High-risk patients may be identified using tumor markers.

LST-2, a human liver-specific organic anion transporter, determines methotrexate sensitivity in gastrointestinal cancers

BACKGROUND & AIMS

One approach to the development of targeted cancer chemotherapy exploits increased uptake of the agent into neoplastic cells. In this scenario, higher concentrations of the agent in cancer cells are responsible for differential killing, whereas the low concentration in normal human cells decreases side effects. The aim of this study was to isolate an organic anion transporter that is weak in normal cells, but abundantly expressed in cancer cells, to deliver the anticancer drugs to the cells.

METHODS

A human liver complementary DNA (cDNA) library was screened with liver-specific transporter (LST)-1 cDNA as a probe. Northern blot analyses were performed using the isolated cDNA (termed LST-2). An LST-2-specific antibody was raised, and immunohistochemical analyses including immunoelectron microscopy were performed. Xenopus oocyte expression system was used for functional analysis. We also established a permanent cell line that consistently expresses LST-2 to examine the relationship between methotrexate uptake and sensitivity.

RESULTS

The isolated cDNA, LST-2, has 79.7% of overall homology with human LST-1. LST-2 exclusively expressed in the liver under normal conditions and its immunoreactivity was highest at the basolateral membrane of the hepatocytes around the central vein. Although its weak expression in the liver, LST-2 is abundantly expressed in the gastric, colon, and pancreatic cancers. On the other hand, the LST-1 was only detected in a hepatic cell line. LST-2 transports methotrexate in a saturable and dose-dependent manner. Furthermore, introduction of the LST-2 gene into mammalian cells potentiates sensitivity to methotrexate.

CONCLUSIONS

LST-2 is one of the prime candidate molecules for determining methotrexate sensitivity and may be a good target to deliver anticancer drugs to the gastrointestinal cancers.

Human liver-specific organic anion transporter, LST-1, mediates uptake of pravastatin by human hepatocytes

Involvement of LST-1 (a human liver-specific transporter, also called OATP2) as the major transporter in the uptake of pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, by human liver was demonstrated. The hepatic uptake of pravastatin evaluated using human hepatocytes was Na(+)-independent and reached saturation with a Michaelis constant (K(m)) of 11.5 +/- 2.2 microM. The uptake of pravastatin was temperature-dependent and was inhibited by estradiol-17beta-D-glucuronide, taurocholic acid, bromosulfophthalein, and simvastatin acid, but not by p-aminohippurate. Estradiol-17beta-D-glucuronide competitively inhibited pravastatin uptake with an inhibition constant comparable to the K(m) value for estradiol-17beta-D-glucuronide transport, indicating that a common transporter mediates the transport of pravastatin and estradiol-17beta-D-glucuronide in human hepatocytes. The results obtained with human hepatocytes agreed with those obtained with LST-1 expressing Xenopus oocytes. Oocytes microinjected with human liver polyadenylated mRNA showed Na(+)-independent uptake of pravastatin and estradiol-17beta-D-glucuronide. A simultaneous injection of LST-1 antisense oligonucleotides completely abolished this uptake. Expression of LST-1 was immunohistochemically demonstrated in the human hepatocytes, but not in Hep G2 cells, which showed very low uptake of pravastatin. Therefore, LST-1 was regarded as a key molecule for pravastatin in liver-specific inhibition of cholesterol synthesis, making pravastatin accessible to the target enzyme, which would otherwise not be inhibited by this hydrophilic drug.

Molecular identification of a rat novel organic anion transporter moat1, which transports prostaglandin D(2), leukotriene C(4), and taurocholate

We have isolated a rat novel multispecific organic anion transporter, moat1. The isolated clones were originated by alternative splicing of the moat1 mRNA. The nucleotide sequences predict a protein of 682 amino acids with moderate sequence similarity to LST-1, the oatp family, and the prostaglandin transporter. Northern blot analysis of rat moat1 identified a predominant transcript of 4.4 kilonucleotides in all tissues. Northern blot and in situ hybridization analyses of rat brain further indicated that moat1 mRNA is widely distributed in neuronal cells of the central nervous system, especially in the hippocampus and cerebellum. moat1 transports prostaglandin D(2) (K(m); 35.5 nM), leukotriene C(4) (K(m); 3.2 microM) and taurocholate (K(m); 17.6 microM) in a sodium-independent manner. moat1 also transports prostaglandin E(1), E(2), thromboxane B(2), and iloprost but not dehydroepiandrosterone sulfate and digoxin, of which the substrate specificity is similar, but definitively different from those of any other organic anion transporters.

Molecular characterization and functional regulation of a novel rat liver-specific organic anion transporter rlst-1

BACKGROUND & AIMS

Recently, we isolated a new complementary DNA (cDNA) encoding human liver-specific organic anion transporter (LST-1), representing the multispecificity of human liver. The aim of this study was to isolate a rat counterpart of human LST-1 and examine the expression regulation of its messenger RNA (mRNA) to clarify the molecular basis of cholestasis.

METHODS

A rat liver cDNA library was screened with human LST-1 cDNA as a probe. Xenopus oocyte expression system was used for functional analysis. Northern blot analyses were performed using the isolated cDNA (termed rlst-1). The bile duct ligation model and the cecum ligation and puncture model were used for expression analyses.

RESULTS

rlst-1 encodes 652 amino acids, predicting at least 11 transmembrane regions. The overall homology with human LST-1 was 60.2%, which is the highest among all known organic anion transporters. rlst-1 also belongs to the same new gene family as human LST-1, located between the organic anion transporter family and the prostaglandin transporter. rlst-1 preferably transports taurocholate (K(m), 9.45 micromol/L) in an Na(+)-independent manner. The rlst-1 mRNA is exclusively expressed in the liver. In both the bile duct ligation model and the cecum ligation and puncture model, mRNA expression levels of rlst-1 were down-regulated.

CONCLUSIONS

rlst-1 is a counterpart of human LST-1 and is one of the important transporters in rat liver for the clearance of bile acid. The expression of rlst-1 may be under feedback regulation of cholestasis by biliary obstruction and/or sepsis.

Identification of a novel gene family encoding human liver-specific organic anion transporter LST-1

We have isolated a novel liver-specific organic anion transporter, LST-1, that is expressed exclusively in the human, rat, and mouse liver. LST-1 is a new gene family located between the organic anion transporter family and prostaglandin transporter. LST-1 transports taurocholate (Km = 13.6 microM) in a sodium-independent manner. LST-1 also shows broad substrate specificity. It transports conjugated steroids (dehydroepiandrosterone sulfate, estradiol-17beta-glucuronide, and estrone-3-sulfate), eicosanoids (prostaglandin E2, thromboxane B2, leukotriene C4, leukotriene E4), and thyroid hormones (thyroxine, Km = 3.0 microM and triiodothyronine, Km = 2.7 microM), reflecting hepatic multispecificity. LST-1 is probably the most important transporter in human liver for clearance of bile acids and organic anions because hepatic levels of another organic anion transporter, OATP, is very low. This is also the first report of the human molecule that transports thyroid hormones.

Pravastatin, an HMG-CoA reductase inhibitor, is transported by rat organic anion transporting polypeptide, oatp2

PURPOSE

We previously demonstrated the HMG-CoA reductase inhibitor, pravastatin, is actively taken up into isolated rat hepatocytes through multispecific organic anion transporters. The present study examined whether a newly cloned organic anion transporting polypeptide (oatp2) transports pravastatin.

METHODS

We investigated functional expression of oatp2 in Xenopus laevis oocytes, to examine [14C] pravastatin uptake.

RESULTS

[14C] Pravastatin (30 microM) uptake into oatp2 cRNA-injected oocytes was 40 times higher than that of water-injected control oocytes. The oatp2-mediated pravastatin uptake was Na+-independent and saturable. The Michaelis-Menten constant was 37.5+/-9.9 microM, a level comparable to that obtained in isolated rat hepatocytes in our previous study. As is the case with rat hepatocytes, the uptake of pravastatin (30 microM) was inhibited by 300 microM concentrations of taurocholate, cholate, bromosulfophthalein, estradiol-17beta-glucuronide, and simvastatin acid, but not by para-aminohippurate. On the other hand, [14C] simvastatin acid (30 microM) uptake of oatp2 cRNA-injected oocytes was not significantly different from that of water-injected oocytes.

CONCLUSIONS

The cloned oatp2 was identified as the transporter responsible for the active hepatocellular pravastatin uptake.

Immunohistochemical distribution and functional characterization of an organic anion transporting polypeptide 2 (oatp2)

The rabbit polyclonal antibody against rat organic anion transporting polypeptide 2 (oatp2) was raised and immunoaffinity-purified. Western blot analysis for oatp2 detected two bands ( 74 and 76 kDa) in rat brain and a single band (76 kDa) in the liver. By immunohistochemical analysis, the oatp2 immunoreactivity was specifically high at the basolateral membrane of rat hepatocytes. Functionally, the oatp2-expressing oocytes were found to transport dehydroepiandrosterone sulfate, delta1 opioid receptor agonist [D-Pen2,D-Pen5]enkephalin, Leuenkephalin, and biotin significantly, as well as the substrates previously reported. These data reveal the exact distribution of the rat oatp2 at the protein level in the liver, and that oatp2 appears to be involved in the multispecificity of the uptaking substrates in the liver and brain.