Strategies to enhance the response of liver cancer to pharmacological treatments

In contrast to other types of cancers, there is no available efficient pharmacological treatment to improve the outcomes of patients suffering from major primary liver cancers, i.e., hepatocellular carcinoma and cholangiocarcinoma. This dismal situation is partly due to the existence in these tumors of many different and synergistic mechanisms of resistance, accounting for the lack of response of these patients, not only to classical chemotherapy but also to more modern pharmacological agents based on the inhibition of tyrosine kinase receptors (TKIs) and the stimulation of the immune response against the tumor using immune checkpoint inhibitors (ICIs). This review summarizes the effort to develop strategies to overcome this severe limitation, including searching for novel drugs derived from synthetic, semisynthetic, or natural products with vectorial properties against therapeutic targets to increase drug uptake or reduce drug export from cancer cells. Besides, immunotherapy is a promising line of research that is already starting to be implemented in clinical practice. Although less successful than in other cancers, the foreseen future for this strategy in treating liver cancers is considerable. Similarly, the pharmacological inhibition of epigenetic targets is highly promising. Many novel "epidrugs", able to act on "writer", "reader" and "eraser" epigenetic players, are currently being evaluated in preclinical and clinical studies. Finally, gene therapy is a broad field of research in the fight against liver cancer chemoresistance, based on the impressive advances recently achieved in gene manipulation. In sum, although the present is still dismal, there is reason for hope in the non-too-distant future.

Impact of liver diseases and pharmacological interactions on the transportome involved in hepatic drug disposition

The liver plays a pivotal role in drug disposition owing to the expression of transporters accounting for the uptake at the sinusoidal membrane and the efflux across the basolateral and canalicular membranes of hepatocytes of many different compounds. Moreover, intracellular mechanisms of phases I and II biotransformation generate, in general, inactive compounds that are more polar and easier to eliminate into bile or refluxed back toward the blood for their elimination by the kidneys, which becomes crucial when the biliary route is hampered. The set of transporters expressed at a given time, i.e., the so-called transportome, is encoded by genes belonging to two gene superfamilies named Solute Carriers (SLC) and ATP-Binding Cassette (ABC), which account mainly, but not exclusively, for the uptake and efflux of endogenous substances and xenobiotics, which include many different drugs. Besides the existence of genetic variants, which determines a marked interindividual heterogeneity regarding liver drug disposition among patients, prevalent diseases, such as cirrhosis, non-alcoholic steatohepatitis, primary sclerosing cholangitis, primary biliary cirrhosis, viral hepatitis, hepatocellular carcinoma, cholangiocarcinoma, and several cholestatic liver diseases, can alter the transportome and hence affect the pharmacokinetics of drugs used to treat these patients. Moreover, hepatic drug transporters are involved in many drug-drug interactions (DDI) that challenge the safety of using a combination of agents handled by these proteins. Updated information on these questions has been organized in this article by superfamilies and families of members of the transportome involved in hepatic drug disposition.

Relationship between cholestasis and altered progesterone metabolism in the placenta-maternal liver tandem

BACKGROUND

In intrahepatic cholestasis of pregnancy (ICP), there are elevated maternal serum levels of total bile acids, progesterone, and some sulfated metabolites, such as allopregnanolone sulfate, which inhibits canalicular function.

AIM

To investigate the relationship between cholestasis and the expression of crucial enzymes involved in progesterone metabolism in the liver and placenta.

METHODS

Obstructive cholestasis was induced by bile duct ligation (BDL). RT-qPCR (mRNA) and western blot (protein) were used to determine expression levels. Srd5a1 and Akr1c2 enzymatic activities were assayed by substrate disappearance (progesterone and 5α-dihydroprogesterone, respectively), measured by HPLC-MS/MS.

RESULTS

BDL induced decreased Srd5a1 and Akr1c2 expression and activity in rat liver, whereas both enzymes were up-regulated in rat placenta. Regarding sulfotransferases, Sult2b1 was also moderately up-regulated in the liver. In placenta from ICP patients, SRD5A1 and AKR1C2 expression was elevated, whereas both genes were down-regulated in liver biopsies collected from patients with several liver diseases accompanied by cholestasis. SRD5A1 and AKR1C2 expression was not affected by incubating human hepatoma HepG2 cells with FXR agonists (chenodeoxycholic acid and GW4064). Knocking-out Fxr in mice did not reduce Srd5a1 and Akr1c14 expression, which was similarly down-regulated by BDL.

CONCLUSION

SRD5A1 and AKR1C2 expression was markedly altered by cholestasis. This was enhanced in the placenta but decreased in the liver, which is not mediated by FXR. These results suggest that the excess of progesterone metabolites in the serum of ICP patients can involve both enhanced placental production and decreased hepatic clearance. The latter may also occur in other cholestatic conditions.

Sensitization of cholangiocarcinoma cells to chemotherapy through BCRP inhibition with β-caryophyllene oxide

Cholangiocarcinomas (CCAs) are cancers originated in the biliary tree, which are characterized by their high mortality and marked chemoresistance, partly due to the activity of ATP-binding cassette (ABC) export pumps, whose inhibition has been proposed as a strategy for enhancing the response to chemotherapy. We have previously shown that β-caryophyllene oxide (CRYO) acts as a chemosensitizer in hepatocellular carcinoma by inhibiting ABCB1, MRP1, and MRP2. Here, we have evaluated the usefulness of CRYO in inhibiting BCRP and improving the response of CCA to antitumor drugs. The TCGA-CHOL cohort (n = 36) was used for in silico analysis. BCRP expression (mRNA and protein) was assayed in samples from intrahepatic (iCCA) and extrahepatic (eCCA) tumors (n = 50) and CCA-derived cells (EGI-1 and TFK-1). In these cells, BCRP-dependent mitoxantrone transport was determined by flow cytometry. At non-toxic concentrations, CRYO inhibited BCRP function, which enhanced the cytostatic effect of drugs used in the treatment of CCA. The BCRP ability to confer resistance to a panel of antitumor drugs was determined in Chinese hamster ovary (CHO) cells with stable BCRP expression. At non-toxic concentrations, CRYO markedly reduced BCRP-induced resistance to known substrate drugs (mitoxantrone and SN-38) and cisplatin, gemcitabine, sorafenib, and 5-FU but not oxaliplatin. Neither CRYO nor cisplatin alone significantly affected the growth of BCRP-expressing tumors subcutaneously implanted in immunodeficient mice. In contrast, intratumor drug content was enhanced when administered together, and tumor growth was inhibited. In sum, the combined treatment of drugs exported by BCRP with CRYO can improve the response to chemotherapy in CCA patients.

Evaluation of potential targets to enhance the sensitivity of cholangiocarcinoma cells to anticancer drugs

BACKGROUND

Cholangiocarcinoma (CCA) is a highly lethal cancer originated in the biliary tree. Available treatments for CCA are scarcely effective, partly due to mechanisms of chemoresistance, such as aberrant activation of Wnt/β-catenin pathway and dysfunctional p53.

AIM

To evaluate the impact of enhancing the expression of negative regulators of the Wnt/β-catenin pathway (AXIN1, AXIN2, and GSK3B) and the tumor suppressor gene TP53.

METHODS

Gene expression in paired samples of CCA and adjacent non-tumor liver tissue was determined by RT-qPCR and immunohistochemistry (IHC). Using lentiviral vectors, CCA cells were transduced with genes of interest to assess their impact on the resistome (TLDA), apoptosis (annexin V/propidium iodide), and decreased cell viability (MTT).

RESULTS

IHC revealed marked nuclear localization of β-catenin, consistent with Wnt/β-catenin pathway activation. In silico analysis with data from TCGA showed heterogeneous down-regulation of AXIN1, AXIN2, and GSK3B in CCA. Enhancing the expression of AXIN1, AXIN2, and GSK3B in CCA cells was not enough to block the activity of this signaling pathway or significantly modify resistance to 5-FU, gemcitabine, and platinated drugs. Consistent with impaired p53 function, CDKN1A was down-regulated in CCA. Forced TP53 expression induced p21 up-regulation and reduced cell proliferation. Moreover, the resistome was modified (FAS, BAX, TYMP, and CES2 up-regulation along with DHFR, RRM1, and BIRC5 down-regulation), which was accompanied by enhanced sensitivity to some antitumor drugs, mainly platinated drugs.

CONCLUSION

Enhancing TP53 expression, but not that of AXIN1, AXIN2, and GSK3B, in CCA cells may be a useful strategy to sensitize CCA to antitumor drugs.

Role of organic cation transporter 3 (OCT3) in the response of hepatocellular carcinoma to tyrosine kinase inhibitors

Impaired function of organic cation transporter 1 (OCT1) in hepatocellular carcinoma (HCC) has been associated with unsatisfactory response to sorafenib. However, some patients lacking OCT1 at the plasma membrane (PM) of HCC cells still respond to sorafenib, suggesting that another transporter may contribute to take up this drug. The aim of this study was to investigate whether OCT3 could contribute to the uptake of sorafenib and other tyrosine kinase inhibitors (TKIs) and whether OCT3 determination can predict HCC response to sorafenib. Cells overexpressing OCT3 were used to determine the ability of this carrier to transport sorafenib. Immunostaining of OCT3 was performed in HCC samples obtained in the TRANSFER study. Considering the intensity of staining and the number of OCT3-positive cells, tumors were classified as having absent, weak, moderate, or strong OCT3 expression and were also categorized according to the presence or absence of PM staining. Functional in vitro studies revealed that OCT3 is also able to mediate sorafenib uptake. Other TKIs, such as regorafenib, lenvatinib, and cabozantinib can also interact with this transporter. In silico studies suggested that the expression of OCT3 is better preserved in HCC than that of OCT1. In HCC samples, OCT3 was expressed at the PM of cancer cells, and its presence, detected in 26% of tumors, was associated with better outcomes in patients treated with sorafenib. In conclusion, analysis by immunohistochemistry of OCT3 in the PM of tumor cells may help to predict the response of HCC patients to sorafenib and potentially to other TKIs.

Serum lipidome unravels a diagnostic potential in bile acid diarrhoea

OBJECTIVE

Bile acid diarrhoea (BAD) is debilitating yet treatable, but it remains underdiagnosed due to challenging diagnostics. We developed a blood test-based method to guide BAD diagnosis.

DESIGN

We included serum from 50 treatment-naive patients with BAD diagnosed by gold standard 75selenium homotaurocholic acid test, 56 feature-matched controls and 37 patients with non-alcoholic fatty liver disease (NAFLD). Metabolomes were generated using mass spectrometry covering 1295 metabolites and compared between groups. Machine learning was used to develop a BAD Diagnostic Score (BDS).

RESULTS

Metabolomes of patients with BAD significantly differed from controls and NAFLD. We detected 70 metabolites with a discriminatory performance in the discovery set with an area under receiver-operating curve metric above 0.80. Logistic regression modelling using concentrations of decanoylcarnitine, cholesterol ester (22:5), eicosatrienoic acid, L-alpha-lysophosphatidylinositol (18:0) and phosphatidylethanolamine (O-16:0/18:1) distinguished BAD from controls with a sensitivity of 0.78 (95% CI 0.64 to 0.89) and a specificity of 0.93 (95% CI 0.83 to 0.98). The model was independent of covariates (age, sex, body mass index) and distinguished BAD from NAFLD irrespective of fibrosis stage. BDS outperformed other blood test-based tests (7-alpha-hydroxy-4-cholesten-3-one and fibroblast growth factor 19) currently under development.

CONCLUSIONS

BDS derived from serum metabolites in a single-blood sample showed robust identification of patients with BAD with superior specificity and sensitivity compared with current blood test-based diagnostics.

Lacking Immunotherapy Biomarkers for Biliary Tract Cancer: A Comprehensive Systematic Literature Review and Meta-Analysis

BACKGROUND

Immunotherapy has recently been incorporated into the spectrum of biliary tract cancer (BTC) treatment. The identification of predictive response biomarkers is essential in order to identify those patients who may benefit most from this novel treatment option. Here, we propose a systematic literature review and a meta-analysis of PD-1, PD-L1, and other immune-related biomarker expression levels in patients with BTC.

METHODS

Prisma guidelines were followed for this systematic review and meta-analysis. Eligible studies were searched on PubMed. Studies published between 2017 and 2022, reporting data on PD-1/PD-L1 expression and other immune-related biomarkers in patients with BTC, were considered eligible.

RESULTS

A total of 61 eligible studies were identified. Despite the great heterogeneity between 39 studies reporting data on PD-L1 expression, we found a mean PD-L1 expression percentage (by choosing the lowest cut-off per study) of 25.6% (95% CI 21.0 to 30.3) in BTCs. The mean expression percentages of PD-L1 were 27.3%, 21.3%, and 27.4% in intrahepatic cholangiocarcinomas (iCCAs-15 studies), perihilar-distal CCAs (p/dCCAs-7 studies), and gallbladder cancer (GBC-5 studies), respectively. Furthermore, 4.6% (95% CI 2.38 to 6.97) and 2.5% (95% CI 1.75 to 3.34) of BTCs could be classified as TMB-H and MSI/MMRd tumors, respectively.

CONCLUSION

From our analysis, PD-L1 expression was found to occur approximately in 26% of BTC patients, with minimal differences based on anatomical location. TMB-H and MSI molecular phenotypes occurred less frequently. We still lack a reliable biomarker, especially in patients with mismatch-proficient tumors, and we must need to make an effort to conceive new prospective biomarker discovery studies.

Relevance of the organic anion transporting polypeptide 1B3 (OATP1B3) in the personalized pharmacological treatment of hepatocellular carcinoma

Although pharmacological treatment is the best option for most patients with advanced hepatocellular carcinoma (HCC), its success is very limited, partly due to reduced uptake and enhanced efflux of antitumor drugs. Here we have explored the usefulness of vectorizing drugs towards the organic anion transporting polypeptide 1B3 (OATP1B3) to enhance their efficacy against HCC cells. In silico studies (RNA-Seq data, 11 cohorts) and immunohistochemistry analyses revealed a marked interindividual variability, together with general downregulation but still expression of OATP1B3 in the plasma membrane of HCC cells. The measurement of mRNA variants in 20 HCC samples showed the almost absence of the cancer-type variant (Ct-OATP1B3) together with marked predominance of the liver-type variant (Lt-OATP1B3). In Lt-OATP1B3-expressing cells, the screening of 37 chemotherapeutical drugs and 17 tyrosine kinase receptors inhibitors (TKIs) revealed that 10 classical anticancer drugs and 12 TKIs were able to inhibit Lt-OATP1B3-mediated transport. Lt-OATP1B3-expressing cells were more sensitive than Mock parental cells (transduced with empty lentiviral vectors) to some Lt-OATP1B3 substrates (paclitaxel and the bile acid-cisplatin derivative Bamet-UD2), but not to cisplatin, which is not transported by Lt-OATP1B3. This enhanced response was abolished by competition with taurocholic acid, a known Lt-OATP1B3 substrate. Tumors subcutaneously generated in immunodeficient mice by Lt-OATP1B3-expressing HCC cells were more sensitive to Bamet-UD2 than those derived from Mock cells. In conclusion, Lt-OATP1B3 expression should be screened before deciding the use of anticancer drugs substrates of this carrier in the personalized treatment of HCC. Moreover, Lt-OATP1B3-mediated uptake must be considered when designing novel anti-HCC targeted drugs.

Liquid biopsy-based protein biomarkers for risk prediction, early diagnosis, and prognostication of cholangiocarcinoma

BACKGROUND & AIMS

Cholangiocarcinoma (CCA), heterogeneous biliary tumours with dismal prognosis, lacks accurate early diagnostic methods especially important for individuals at high-risk (i.e. those with primary sclerosing cholangitis [PSC]). Here, we searched for protein biomarkers in serum extracellular vesicles (EVs).

METHODS

EVs from patients with isolated PSC (n = 45), concomitant PSC-CCA (n = 44), PSC who developed CCA during follow-up (PSC to CCA; n = 25), CCAs from non-PSC aetiology (n = 56), and hepatocellular carcinoma (n = 34) and healthy individuals (n = 56) were characterised by mass spectrometry. Diagnostic biomarkers for PSC-CCA, non-PSC CCA, or CCAs regardless of aetiology (Pan-CCAs) were defined and validated by ELISA. Their expression was evaluated in CCA tumours at a single-cell level. Prognostic EV biomarkers for CCA were investigated.

RESULTS

High-throughput proteomics of EVs identified diagnostic biomarkers for PSC-CCA, non-PSC CCA, or Pan-CCA, and for the differential diagnosis of intrahepatic CCA and hepatocellular carcinoma, which were cross-validated by ELISA using total serum. Machine learning-based algorithms disclosed CRP/FIBRINOGEN/FRIL for the diagnosis of PSC-CCA (local disease [LD]) vs. isolated PSC (AUC = 0.947; odds ratio [OR] =36.9) and, combined with carbohydrate antigen 19-9, overpowers carbohydrate antigen 19-9 alone. CRP/PIGR/VWF allowed the diagnosis of LD non-PSC CCAs vs. healthy individuals (AUC = 0.992; OR = 387.5). It is noteworthy that CRP/FRIL accurately diagnosed LD Pan-CCA (AUC = 0.941; OR = 89.4). Levels of CRP/FIBRINOGEN/FRIL/PIGR showed predictive capacity for CCA development in PSC before clinical evidence of malignancy. Multi-organ transcriptomic analysis revealed that serum EV biomarkers were mostly expressed in hepatobiliary tissues, and single-cell RNA sequencing and immunofluorescence analysis of CCA tumours showed their presence mainly in malignant cholangiocytes. Multivariable analysis unveiled EV prognostic biomarkers, with COMP/GNAI2/CFAI and ACTN1/MYCT1/PF4V associated negatively and positively with patients' survival, respectively.

CONCLUSIONS

Serum EVs contain protein biomarkers for the prediction, early diagnosis, and prognostication of CCA that are detectable using total serum, representing a tumour cell-derived liquid biopsy tool for personalised medicine.

IMPACT AND IMPLICATIONS

The accuracy of current imaging tests and circulating tumour biomarkers for cholangiocarcinoma (CCA) diagnosis is far from satisfactory. Most CCAs are considered sporadic, although up to 20% of patients with primary sclerosing cholangitis (PSC) develop CCA during their lifetime, constituting a major cause of PSC-related death. This international study has proposed protein-based and aetiology-related logistic models with predictive, diagnostic, or prognostic capacities by combining two to four circulating protein biomarkers, moving a step forward into personalised medicine. These novel liquid biopsy tools may allow the (i) easy and non-invasive diagnosis of sporadic CCAs, (ii) identification of patients with PSC with higher risk for CCA development, (iii) establishment of cost-effective surveillance programmes for the early detection of CCA in high-risk populations (e.g. PSC), and (iv) prognostic stratification of patients with CCA, which, altogether, may increase the number of cases eligible for potentially curative options or to receive more successful treatments, decreasing CCA-related mortality.

Role of Intracellular Drug Disposition in the Response of Acute Myeloid Leukemia to Cytarabine and Idarubicin Induction Chemotherapy

Despite its often low efficacy and high toxicity, the standard treatment for acute myeloid leukemia (AML) is induction chemotherapy with cytarabine and idarubicin. Here, we have investigated the role of transporters and drug-metabolizing enzymes in this poor outcome. The expression levels (RT-qPCR) of potentially responsible genes in blasts collected at diagnosis were related to the subsequent response to two-cycle induction chemotherapy. The high expression of uptake carriers (ENT2), export ATP-binding cassette (ABC) pumps (MDR1), and enzymes (DCK, 5-NT, and CDA) in the blasts was associated with a lower response. Moreover, the sensitivity to cytarabine in AML cell lines was associated with ENT2 expression, whereas the expression of ABC pumps and enzymes was reduced. No ability of any AML cell line to export idarubicin through the ABC pumps, MDR1 and MRP, was found. The exposure of AML cells to cytarabine or idarubicin upregulated the detoxifying enzymes (5-NT and DCK). In AML patients, 5-NT and DCK expression was associated with the lack of response to induction chemotherapy (high sensitivity and specificity). In conclusion, in the blasts of AML patients, the reduction of the intracellular concentration of the active metabolite of cytarabine, mainly due to the increased expression of inactivating enzymes, can determine the response to induction chemotherapy.

Impact of Aberrant β-Catenin Pathway on Cholangiocarcinoma Heterogeneity

The poor prognosis of most cases of advanced cholangiocarcinoma (CCA) constitutes a severe problem in modern oncology, which is aggravated by the fact that the incidence of this liver cancer is increasing worldwide and is often diagnosed late, when surgical removal is not feasible. The difficulty of dealing with this deadly tumor is augmented by the heterogeneity of CCA subtypes and the complexity of mechanisms involved in enhanced proliferation, apoptosis avoidance, chemoresistance, invasiveness, and metastasis that characterize CCA. Among the regulatory processes implicated in developing these malignant traits, the Wnt/β-catenin pathway plays a pivotal role. Alteration of β-catenin expression and subcellular localization has been associated with worse outcomes in some CCA subtypes. This heterogeneity, which also affects cellular and in vivo models commonly used to study CCA biology and anticancer drug development, must be taken into account for CCA investigation to more accurately extrapolate basic laboratory research to the clinical situation. A better understanding of the altered Wnt/β-catenin pathway in relationship with the heterogeneous forms of CCA is mandatory for developing novel diagnostic tools and therapeutic strategies for patients suffering from this lethal disease.

Criteria for preclinical models of cholangiocarcinoma: scientific and medical relevance

Cholangiocarcinoma (CCA) is a rare malignancy that develops at any point along the biliary tree. CCA has a poor prognosis, its clinical management remains challenging, and effective treatments are lacking. Therefore, preclinical research is of pivotal importance and necessary to acquire a deeper understanding of CCA and improve therapeutic outcomes. Preclinical research involves developing and managing complementary experimental models, from in vitro assays using primary cells or cell lines cultured in 2D or 3D to in vivo models with engrafted material, chemically induced CCA or genetically engineered models. All are valuable tools with well-defined advantages and limitations. The choice of a preclinical model is guided by the question(s) to be addressed; ideally, results should be recapitulated in independent approaches. In this Consensus Statement, a task force of 45 experts in CCA molecular and cellular biology and clinicians, including pathologists, from ten countries provides recommendations on the minimal criteria for preclinical models to provide a uniform approach. These recommendations are based on two rounds of questionnaires completed by 35 (first round) and 45 (second round) experts to reach a consensus with 13 statements. An agreement was defined when at least 90% of the participants voting anonymously agreed with a statement. The ultimate goal was to transfer basic laboratory research to the clinics through increased disease understanding and to develop clinical biomarkers and innovative therapies for patients with CCA.

Clinical relevance of biomarkers in cholangiocarcinoma: critical revision and future directions

Cholangiocarcinoma (CCA) is a malignant tumour arising from the biliary system. In Europe, this tumour frequently presents as a sporadic cancer in patients without defined risk factors and is usually diagnosed at advanced stages with a consequent poor prognosis. Therefore, the identification of biomarkers represents an utmost need for patients with CCA. Numerous studies proposed a wide spectrum of biomarkers at tissue and molecular levels. With the present paper, a multidisciplinary group of experts within the European Network for the Study of Cholangiocarcinoma discusses the clinical role of tissue biomarkers and provides a selection based on their current relevance and potential applications in the framework of CCA. Recent advances are proposed by dividing biomarkers based on their potential role in diagnosis, prognosis and therapy response. Limitations of current biomarkers are also identified, together with specific promising areas (ie, artificial intelligence, patient-derived organoids, targeted therapy) where research should be focused to develop future biomarkers.

Expression of Chemoresistance-Associated ABC Proteins in Hepatobiliary, Pancreatic and Gastrointestinal Cancers

Simple Summary

One-third of the approximately 10 million deaths yearly caused by cancer worldwide are due to hepatobiliary, pancreatic, and gastrointestinal tumors. One primary reason for this high mortality is the lack of response of these cancers to pharmacological treatment. More than 100 genes have been identified as responsible for seven mechanisms of chemoresistance, but only a few of them play a critical role. These include ABC proteins (mainly MDR1, MRP1-6, and BCRP), whose expression pattern greatly determines the individual sensitivity of each tumor to pharmacotherapy.

Abstract

Hepatobiliary, pancreatic, and gastrointestinal cancers account for 36% of the ten million deaths caused by cancer worldwide every year. The two main reasons for this high mortality are their late diagnosis and their high refractoriness to pharmacological treatments, regardless of whether these are based on classical chemotherapeutic agents, targeted drugs, or newer immunomodulators. Mechanisms of chemoresistance (MOC) defining the multidrug resistance (MDR) phenotype of each tumor depend on the synergic function of proteins encoded by more than one hundred genes classified into seven groups (MOC1-7). Among them, the efflux of active agents from cancer cells across the plasma membrane caused by members of the superfamily of ATP-binding cassette (ABC) proteins (MOC-1b) plays a crucial role in determining tumor MDR. Although seven families of human ABC proteins are known, only a few pumps (mainly MDR1, MRP1-6, and BCRP) have been associated with reducing drug content and hence inducing chemoresistance in hepatobiliary, pancreatic, and gastrointestinal cancer cells. The present descriptive review, which compiles the updated information on the expression of these ABC proteins, will be helpful because there is still some confusion on the actual relevance of these pumps in response to pharmacological regimens currently used in treating these cancers. Moreover, we aim to define the MOC pattern on a tumor-by-tumor basis, even in a dynamic way, because it can vary during tumor progression and in response to chemotherapy. This information is indispensable for developing novel strategies for sensitization.

Targeting NAE1-mediated protein hyper-NEDDylation halts cholangiocarcinogenesis and impacts on tumor-stroma crosstalk in experimental models

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) comprises a heterogeneous group of malignant tumors associated with dismal prognosis. Alterations in post-translational modifications (PTMs), including NEDDylation, result in abnormal protein dynamics, cell disturbances and disease. Herein, we investigate the role of NEDDylation in CCA development and progression.

METHODS

Levels and functions of NEDDylation, together with response to pevonedistat (NEDDylation inhibitor) or CRISPR/Cas9 against NAE1 were evaluated in vitro, in vivo and/or in patients with CCA. The development of preneoplastic lesions in Nae1^+/- mice was investigated using an oncogene-driven CCA model. The impact of NEDDylation in CCA cells on tumor-stroma crosstalk was assessed using CCA-derived cancer-associated fibroblasts (CAFs). Proteomic analyses were carried out by mass-spectrometry.

RESULTS

The NEDDylation machinery was found overexpressed and overactivated in human CCA cells and tumors. Most NEDDylated proteins found upregulated in CCA cells, after NEDD8-immunoprecipitation and further proteomics, participate in the cell cycle, proliferation or survival. Genetic (CRISPR/Cas9-NAE1) and pharmacological (pevonedistat) inhibition of NEDDylation reduced CCA cell proliferation and impeded colony formation in vitro. NEDDylation depletion (pevonedistat or Nae1^+/- mice) halted tumorigenesis in subcutaneous, orthotopic, and oncogene-driven models of CCA in vivo. Moreover, pevonedistat potentiated chemotherapy-induced cell death in CCA cells in vitro. Mechanistically, impaired NEDDylation triggered the accumulation of both cullin RING ligase and NEDD8 substrates, inducing DNA damage and cell cycle arrest. Furthermore, impaired NEDDylation in CCA cells reduced the secretion of proteins involved in fibroblast activation, angiogenesis, and oncogenic pathways, ultimately hampering CAF proliferation and migration.

CONCLUSION

Aberrant protein NEDDylation contributes to cholangiocarcinogenesis by promoting cell survival and proliferation. Moreover, NEDDylation impacts the CCA-stroma crosstalk. Inhibition of NEDDylation with pevonedistat may represent a potential therapeutic strategy for patients with CCA.

LAY SUMMARY

Little is known about the role of post-translational modifications of proteins in cholangiocarcinoma development and progression. Herein, we show that protein NEDDylation is upregulated and hyperactivated in cholangiocarcinoma, promoting tumor growth. Pharmacological inhibition of NEDDylation halts cholangiocarcinogenesis and could be an effective therapeutic strategy to tackle these tumors.

Ursodeoxycholic acid in intrahepatic cholestasis of pregnancy: a systematic review and individual participant data meta-analysis

BACKGROUND

Ursodeoxycholic acid is commonly used to treat intrahepatic cholestasis of pregnancy, yet its largest trial detected minimal benefit for a composite outcome (stillbirth, preterm birth, and neonatal unit admission). We aimed to examine whether ursodeoxycholic acid affects specific adverse perinatal outcomes.

METHODS

In this systematic review and individual participant data meta-analysis, we searched PubMed, Web of Science, Embase, MEDLINE, CINAHL, Global Health, MIDIRS, and Cochrane without language restrictions for relevant articles published between database inception, and Jan 1, 2020, using search terms referencing intrahepatic cholestasis of pregnancy, ursodeoxycholic acid, and perinatal outcomes. Eligible studies had 30 or more study participants and reported on at least one individual with intrahepatic cholestasis of pregnancy and bile acid concentrations of 40 μmol/L or more. We also included two unpublished cohort studies. Individual participant data were collected from the authors of selected studies. The primary outcome was the prevalence of stillbirth, for which we anticipated there would be insufficient data to achieve statistical power. Therefore, we included a composite of stillbirth and preterm birth as a main secondary outcome. A mixed-effects meta-analysis was done using multi-level modelling and adjusting for bile acid concentration, parity, and multifetal pregnancy. Individual participant data analyses were done for all studies and in different subgroups, which were produced by limiting analyses to randomised controlled trials only, singleton pregnancies only, or two-arm studies only. This study is registered with PROSPERO, CRD42019131495.

FINDINGS

The authors of the 85 studies fulfilling our inclusion criteria were contacted. Individual participant data from 6974 women in 34 studies were included in the meta-analysis, of whom 4726 (67·8%) took ursodeoxycholic acid. Stillbirth occurred in 35 (0·7%) of 5097 fetuses among women with intrahepatic cholestasis of pregnancy treated with ursodeoxycholic acid and in 12 (0·6%) of 2038 fetuses among women with intrahepatic cholestasis of pregnancy not treated with ursodeoxycholic acid (adjusted odds ratio [aOR] 1·04, 95% CI 0·35-3·07; p=0·95). Ursodeoxycholic acid treatment also had no effect on the prevalence of stillbirth when considering only randomised controlled trials (aOR 0·29, 95% CI 0·04-2·42; p=0·25). Ursodeoxycholic acid treatment had no effect on the prevalence of the composite outcome in all studies (aOR 1·28, 95% CI 0·86-1·91; p=0·22), but was associated with a reduced composite outcome when considering only randomised controlled trials (0·60, 0·39-0·91; p=0·016).

INTERPRETATION

Ursodeoxycholic acid treatment had no significant effect on the prevalence of stillbirth in women with intrahepatic cholestasis of pregnancy, but our analysis was probably limited by the low overall event rate. However, when considering only randomised controlled trials, ursodeoxycholic acid was associated with a reduction in stillbirth in combination with preterm birth, providing evidence for the clinical benefit of antenatal ursodeoxycholic acid treatment.

FUNDING

Tommy's, the Wellcome Trust, ICP Support, and the National Institute for Health Research.

Cholangiocarcinoma 2020: the next horizon in mechanisms and management

Cholangiocarcinoma (CCA) includes a cluster of highly heterogeneous biliary malignant tumours that can arise at any point of the biliary tree. Their incidence is increasing globally, currently accounting for ~15% of all primary liver cancers and ~3% of gastrointestinal malignancies. The silent presentation of these tumours combined with their highly aggressive nature and refractoriness to chemotherapy contribute to their alarming mortality, representing ~2% of all cancer-related deaths worldwide yearly. The current diagnosis of CCA by non-invasive approaches is not accurate enough, and histological confirmation is necessary. Furthermore, the high heterogeneity of CCAs at the genomic, epigenetic and molecular levels severely compromises the efficacy of the available therapies. In the past decade, increasing efforts have been made to understand the complexity of these tumours and to develop new diagnostic tools and therapies that might help to improve patient outcomes. In this expert Consensus Statement, which is endorsed by the European Network for the Study of Cholangiocarcinoma, we aim to summarize and critically discuss the latest advances in CCA, mostly focusing on classification, cells of origin, genetic and epigenetic abnormalities, molecular alterations, biomarker discovery and treatments. Furthermore, the horizon of CCA for the next decade from 2020 onwards is highlighted.

Relationship between changes in the exon-recognition machinery and SLC22A1 alternative splicing in hepatocellular carcinoma

Changes in the phenotype that characterizes cancer cells are partly due to altered processing of pre-mRNA by the spliceosome. We have previously reported that aberrant splicing plays an essential role in the impaired response of hepatocellular carcinoma (HCC) to sorafenib by reducing the expression of functional organic cation transporter type 1 (OCT1, gene SLC22A1) that constitutes the primary way for HCC cells to take up this and other drugs. The present study includes an in silico analysis of publicly available databases to investigate the relationship between alternative splicing of SLC22A1 pre-mRNA and the expression of genes involved in the exon-recognition machinery in HCC and adjacent non-tumor tissue. Using Taqman Low-Density Arrays, the findings were validated in 25 tumors that were resected without neoadjuvant chemotherapy. The results supported previous reports showing that there was a considerable degree of alternative splicing of SLC22A1 in adjacent non-tumor tissue, which was further increased in the tumor in a stage-unrelated manner. Splicing perturbation was associated with changes in the profile of proteins determining exon recognition. The results revealed the importance of using paired samples for splicing analysis in HCC and confirmed that aberrant splicing plays an essential role in the expression of functional OCT1. Changes in the exon recognition machinery may also affect the expression of other proteins in HCC. Moreover, these results pave the way to further investigations on the mechanistic bases of the relationship between the expression of spliceosome-associated genes and its repercussion on the appearance of alternative and aberrant splicing in HCC.

Sensitizing gastric adenocarcinoma to chemotherapy by pharmacological manipulation of drug transporters

Owing to intrinsic and acquired chemoresistance, the response of gastric adenocarcinoma (GAC) to chemotherapy is very poor. Here we have investigated the role of transportome in reducing the intracellular content of anticancer drugs and conferring multidrug resistance (MDR) phenotype. Tumors specimens and paired adjacent tissue were analyzed to determine the MDR signature by TaqMan Low-Density Arrays and single-gene qPCR. Strategies of sensitization were evaluated in vitro using the GAC-derived cell line AGS and in vivo using a subcutaneous xenograft model in immunodeficient nude mice. Several transporters involved in drug uptake and export, which are present in healthy stomach, were highly expressed in GAC. In contrast, the cancer-type OATP1B3 was almost exclusively expressed in tumor tissue. The transportome profile varied depending on tumor anatomical location, differentiation, and stage. Immunofluorescence analysis revealed high MRP1 and MRP4 expression at the plasma membrane of tumor cells as well as AGS cells in culture, in which MRP inhibition resulted in selective sensitization to cytotoxic MRP substrates, such as sorafenib, docetaxel, etoposide, and doxorubicin. In mice with subcutaneous tumors formed by AGS cells, sorafenib alone failed to prevent tumor growth. In contrast, this drug induced a marked inhibitory effect when it was co-administered with diclofenac. In conclusion, MRP1 and MRP4 play an important role in the lack of response of GAC to drugs that are transported by these export pumps. Moreover, agents, such as sorafenib, considered at present useless to treat GAC, may become active antitumor drugs when co-administered with non-toxic MRP inhibitors, such as diclofenac.

Causes of hOCT1-Dependent Cholangiocarcinoma Resistance to Sorafenib and Sensitization by Tumor-Selective Gene Therapy

Although the multi-tyrosine kinase inhibitor sorafenib is useful in the treatment of several cancers, cholangiocarcinoma (CCA) is refractory to this drug. Among other mechanisms of chemoresistance, impaired uptake through human organic cation transporter type 1 (hOCT1) (gene SLC22A1) has been suggested. Here we have investigated the events accounting for this phenotypic characteristic and have evaluated the interest of selective gene therapy strategies to overcome this limitation. Gene expression and DNA methylation of SLC22A1 were analyzed using intrahepatic (iCCA) and extrahepatic (eCCA) biopsies (Copenhagen and Salamanca cohorts; n = 132) and The Cancer Genome Atlas (TCGA)-CHOL (n = 36). Decreased hOCT1 mRNA correlated with hypermethylation status of the SLC22A1 promoter. Treatment of CCA cells with decitabine (demethylating agent) or butyrate (histone deacetylase inhibitor) restored hOCT1 expression and increased sorafenib uptake. MicroRNAs able to induce hOCT1 mRNA decay were analyzed in paired samples of TCGA-CHOL (n = 9) and Copenhagen (n = 57) cohorts. Consistent up-regulation in tumor tissue was found for miR-141 and miR-330. High proportion of aberrant hOCT1 mRNA splicing in CCA was also seen. Lentiviral-mediated transduction of eCCA (EGI-1 and TFK-1) and iCCA (HuCCT1) cells with hOCT1 enhanced sorafenib uptake and cytotoxic effects. In chemically induced CCA in rats, reduced rOct1 expression was accompanied by impaired sorafenib uptake. In xenograft models of eCCA cells implanted in mouse liver, poor response to sorafenib was observed. However, tumor growth was markedly reduced by cotreatment with sorafenib and adenoviral vectors encoding hOCT1 under the control of the BIRC5 promoter, a gene highly up-regulated in CCA. Conclusion: The reason for impaired hOCT1-mediated sorafenib uptake by CCA is multifactorial. Gene therapy capable of selectively inducing hOCT1 in tumor cells can be considered a potentially useful chemosensitization strategy to improve the response of CCA to sorafenib.

Diagnostic and prognostic biomarkers in cholangiocarcinoma

The high mortality rate of cholangiocarcinoma (CCA) is due, in part, to the lack of non-invasive approaches able to accurately detect this silent tumour at early stages, when therapeutic options can be potentially curative or may at least increase the overall survival of patients. The fact that the majority of CCA tumours are not linked to any known aetiological factor highly compromises the monitoring of patients at risk for tumour development and also their early diagnosis. Combination of clinical/biochemical features, imaging techniques and analysis of non-specific tumour biomarkers in serum are commonly used to help in the diagnosis of CCA, but tumour biopsy is usually required to confirm the diagnosis. Moreover, no prognostic biomarkers are currently used in the clinical setting, deserving more innovative research, and international validation and consensus. Important efforts have been made in the last few years to identify accurate non-invasive biomarkers, by using innovative techniques and high-throughput omics technologies. This review summarizes and discusses the advances in the investigation of novel diagnostic and prognostic biomarkers in CCA and envisions the future directions in this field of research.

Association of adverse perinatal outcomes of intrahepatic cholestasis of pregnancy with biochemical markers: results of aggregate and individual patient data meta-analyses

BACKGROUND

Intrahepatic cholestasis of pregnancy is associated with adverse perinatal outcomes, but the association with the concentration of specific biochemical markers is unclear. We aimed to quantify the adverse perinatal effects of intrahepatic cholestasis of pregnancy in women with increased serum bile acid concentrations and determine whether elevated bile acid concentrations were associated with the risk of stillbirth and preterm birth.

METHODS

We did a systematic review by searching PubMed, Web of Science, and Embase databases for studies published from database inception to June 1, 2018, reporting perinatal outcomes for women with intrahepatic cholestasis of pregnancy when serum bile acid concentrations were available. Inclusion criteria were studies defining intrahepatic cholestasis of pregnancy based upon pruritus and elevated serum bile acid concentrations, with or without raised liver aminotransferase concentrations. Eligible studies were case-control, cohort, and population-based studies, and randomised controlled trials, with at least 30 participants, and that reported bile acid concentrations and perinatal outcomes. Studies at potential higher risk of reporter bias were excluded, including case reports, studies not comprising cohorts, or successive cases seen in a unit; we also excluded studies with high risk of bias from groups selected (eg, a subgroup of babies with poor outcomes were explicitly excluded), conference abstracts, and Letters to the Editor without clear peer review. We also included unpublished data from two UK hospitals. We did a random effects meta-analysis to determine risk of adverse perinatal outcomes. Aggregate data for maternal and perinatal outcomes were extracted from case-control studies, and individual patient data (IPD) were requested from study authors for all types of study (as no control group was required for the IPD analysis) to assess associations between biochemical markers and adverse outcomes using logistic and stepwise logistic regression. This study is registered with PROSPERO, number CRD42017069134.

FINDINGS

We assessed 109 full-text articles, of which 23 studies were eligible for the aggregate data meta-analysis (5557 intrahepatic cholestasis of pregnancy cases and 165 136 controls), and 27 provided IPD (5269 intrahepatic cholestasis of pregnancy cases). Stillbirth occurred in 45 (0·83%) of 4936 intrahepatic cholestasis of pregnancy cases and 519 (0·32%) of 163 947 control pregnancies (odds ratio [OR] 1·46 [95% CI 0·73-2·89]; I2=59·8%). In singleton pregnancies, stillbirth was associated with maximum total bile acid concentration (area under the receiver operating characteristic curve [ROC AUC]) 0·83 [95% CI 0·74-0·92]), but not alanine aminotransferase (ROC AUC 0·46 [0·35-0·57]). For singleton pregnancies, the prevalence of stillbirth was three (0·13%; 95% CI 0·02-0·38) of 2310 intrahepatic cholestasis of pregnancy cases in women with serum total bile acids of less than 40 μmol/L versus four (0·28%; 0·08-0·72) of 1412 cases with total bile acids of 40-99 μmol/L (hazard ratio [HR] 2·35 [95% CI 0·52-10·50]; p=0·26), and versus 18 (3·44%; 2·05-5·37) of 524 cases for bile acids of 100 μmol/L or more (HR 30·50 [8·83-105·30]; p<0·0001).

INTERPRETATION

The risk of stillbirth is increased in women with intrahepatic cholestasis of pregnancy and singleton pregnancies when serum bile acids concentrations are of 100 μmol/L or more. Because most women with intrahepatic cholestasis of pregnancy have bile acids below this concentration, they can probably be reassured that the risk of stillbirth is similar to that of pregnant women in the general population, provided repeat bile acid testing is done until delivery.

FUNDING

Tommy's, ICP Support, UK National Institute of Health Research, Wellcome Trust, and Genesis Research Trust.

Epigenetic events involved in organic cation transporter 1-dependent impaired response of hepatocellular carcinoma to sorafenib

BACKGROUND AND PURPOSE

The expression of the human organic cation transporter-1 (hOCT1, gene SLC22A1) is reduced in hepatocellular carcinoma (HCC). The molecular bases of this reduction and its relationship with the poor response of HCC to sorafenib were investigated.

EXPERIMENTAL APPROACH

HCC transcriptomes from 366 samples available at TCGA were analysed. Alternative splicing was determined by RT-PCR. The role of miRNAs in SLC22A1 downregulation was investigated. Expression of Oct1 was measured in rodent HCC models (spontaneously generated in Fxr^-/- mice and chemically-induced in rats). hOCT1 was overexpressed in human hepatoma cells (HuH7 and HepG2). Sorafenib and regorafenib uptake was determined by HPLC-MS/MS.

KEY RESULTS

hOCT1 overexpression enhanced sorafenib, but not regorafenib, quinine-inhibitable uptake by hepatoma cells. In rodent HCC, Oct1 was downregulated, which was accompanied by impaired sorafenib uptake. In mice with s.c.-implanted HCC, sorafenib inhibited the growth of hOCT1 overexpressing tumours. In human HCC, hOCT1 expression was inversely correlated with SLC22A1 promoter methylation, whereas demethylation with decitabine enhanced hOCT1 expression in hepatoma cells. Increased proportion of aberrant hOCT1 mRNA variants was found in HCC samples. In silico analysis identified six miRNAs as candidates to target hOCT1 mRNA. When overexpressed in HepG2 cells a significant hOCT1 mRNA decay was induced by hsa-miR-330 and hsa-miR-1468. Analysis of 39 paired tumour/adjacent samples from TCGA revealed that hsa-mir-330 was consistently upregulated in HCC.

CONCLUSION AND IMPLICATIONS

Impaired hOCT1 expression/function in HCC, in part due to epigenetic modifications, plays an important role in the poor pharmacological response of this cancer to sorafenib.

Role of the placenta in serum autotaxin elevation during maternal cholestasis

Intrahepatic cholestasis of pregnancy (ICP) is frequently accompanied by pruritus, whose etiology has been associated with an enhanced production of lysophosphatidic acid (LPA) by the combined action of phospholipase A1/A2 (PLA1/PLA2) and autotaxin (ATX). Here, we have investigated whether the placenta is involved in LPA release to maternal circulation during ICP. Serum levels of ATX and LPA (determined by ELISA) were elevated in women with ICP, and a correlation between both parameters was found. No relationship between serum levels of ATX or LPA and bile acids was found. Expression levels of ATX and PLA2 were determined by RT-qPCR and Western blot. Placenta ATX but not PLA2 was significantly upregulated in ICP, and a tendency to increase was found at the protein level. A correlation between serum ATX and placental ATX mRNA levels was found. In human placenta at term, ATX was clearly detected (by immunofluorescence) in Hofbauer cells, but only faintly in trophoblast cells. In pregnant rats, the expression of Atx and Pla2 in placenta was lower than in liver. When obstructive cholestasis was imposed by bile duct ligation from day 14 of gestation until term, placenta Atx and Pla2 expression was markedly enhanced, and overexpression was confirmed at the protein level for Pla2, whereas Atx protein was not detected. In conclusion, the placenta substantially participates in LPA production during gestation. This contribution is markedly higher during maternal cholestasis and hence, may be involved in ICP-associated pruritus. NEW & NOTEWORTHY Fetal placental macrophages and, to a lesser extent, trophoblast cells express high levels of autotaxin at term. An increased expression of mRNA and protein autotaxin, the key secretory enzyme responsible for the production of lysophosphatidic acid in serum, has been observed in placentas of women with cholestasis of pregnancy, which supports that the placenta can contribute to an increased production of this pruritogenic compound in women suffering from this liver disease.

Molecular bases of the poor response of liver cancer to chemotherapy

A characteristic shared by most frequent types of primary liver cancer, i.e., hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) in adults, and in a lesser extent hepatoblastoma (HB) mainly in children, is their high refractoriness to chemotherapy. This is the result of synergic interactions among complex and diverse mechanisms of chemoresistance (MOC) in which more than 100 genes are involved. Pharmacological treatment, although it can be initially effective, frequently stimulates the expression of MOC genes, which results in the relapse of the tumor, usually with a more aggressive and less chemosensitive phenotype. Identification of the MOC genetic signature accounting for the "resistome" present at each moment of tumor life would prevent the administration of chemotherapeutic regimens without chance of success but still with noxious side effects for the patient. Moreover, a better description of cancer cells strength is required to develop novel strategies based on pharmacological, cellular or gene therapy to overcome liver cancer chemoresistance.

Molecular Bases of Chemoresistance in Cholangiocarcinoma

The multidrug resistance (MDR) phenotype accounts for the poor response of cholangiocarcinoma to available antitumor drugs. This is an important limitation to the use of pharmacological approaches, both as adjuvant therapies and for treating advanced CCA when surgical removal is not possible. MDR is the result of a complex combination of defense mechanisms against toxic compounds already present in cholangiocytes, which play a role in the physiology of these cells by protecting the biliary epithelium from the toxins reaching the biliary tree with the blood that perfuses this tissue, or that are secreted by hepatocytes into bile, to which cholangiocytes are exposed. These mechanisms of chemoresistance (MOC) are also present, usually with enhanced efficacy, in tumors derived from cholangiolar cells. The present review article is an update of the state-of-the-art regarding the MOC involved in the poor response of CCA to antitumor drugs. These MOC have been classified as: changes in the amount of drug in the cells due to decreased uptake (MOC-1a) or enhanced efflux (MOC-1b); altered proportions between prodrug, active drug and inactive metabolites (MOC-2); changes in the molecular targets of antitumor drugs (MOC-3); an enhanced ability of tumor cells to repair drug-induced DNA damage (MOC-4), and an impaired apoptosis/survival balance (MOC-5).

Serum extracellular vesicles contain protein biomarkers for primary sclerosing cholangitis and cholangiocarcinoma

Cholangiocarcinoma (CCA) includes a heterogeneous group of biliary cancers with poor prognosis. Several conditions, such as primary sclerosing cholangitis (PSC), are risk factors. Noninvasive differential diagnosis between intrahepatic CCA and hepatocellular carcinoma (HCC) is sometimes difficult. Accurate noninvasive biomarkers for PSC, CCA, and HCC are not available. In the search for novel biomarkers, serum extracellular vesicles (EV) were isolated from CCA (n = 43), PSC (n = 30), or HCC (n = 29) patients and healthy individuals (control, n = 32); and their protein content was characterized. By using nanoparticle tracking analysis, serum EV concentration was found to be higher in HCC than in all the other groups. Round morphology (by transmission electron microscopy), size (∼180 nm diameter by nanoparticle tracking analysis), and markers (clusters of differentiation 9, 63, and 81 by immunoblot) indicated that most serum EV were exosomes. Proteome profiles (by mass spectrometry) revealed multiple differentially expressed proteins among groups. Several of these proteins showed high diagnostic values with maximum area under the receiver operating characteristic curve of 0.878 for CCA versus control, 0.905 for CCA stage I-II versus control, 0.789 for PSC versus control, 0.806 for noncirhottic PSC versus control, 0.796 for CCA versus PSC, 0.956 for CCA stage I-II versus PSC, 0.904 for HCC versus control, and 0.894 for intrahepatic CCA versus HCC. Proteomic analysis of EV derived from CCA human cells in vitro revealed higher abundance of oncogenic proteins compared to EV released by normal human cholangiocytes. Orthotopic implant of CCA human cells in the liver of immunodeficient mice resulted in the release to serum of EV containing some similar human oncogenic proteins.

CONCLUSION

Proteomic signatures found in serum EV of CCA, PSC, and HCC patients show potential usefulness as diagnostic tools. (Hepatology 2017;66:1125-1143).

The lack of the organic cation transporter OCT1 at the plasma membrane of tumor cells precludes a positive response to sorafenib in patients with hepatocellular carcinoma

Background

Sorafenib is the drug of choice in the treatment of advanced hepatocellular carcinoma (HCC). Beneficial effects are limited by mechanisms of chemoresistance, which include downregulation and/or impaired function of plasma membrane transporters accounting for drug uptake. The organic cation transporter 1 (OCT1) plays a major role in sorafenib uptake and decreased expression in HCC has been associated with poorer response.

Methods

The multicenter retrospective TRANSFER study involved tumor biopsies from 39 patients with advanced HCC and sorafenib therapy for ≥4 wk. Endpoint was the relationship between clinicopathological features and immunohistological result. Immunostaining was performed using specific primary anti-OCT1-head and anti-OCT1-tail antibodies. Tumors were classified according to a simplified staining score as absent, weak, moderate or strong, taking into account the localization of the staining at the plasma membrane as positive or negative.

Results

Results confirmed OCT1 downregulation in half of the cases investigated (10% absent, 38% weak). However, only one third of tumors expressing OCT1 displayed plasma membrane location (15% vs. 36% cytosolic expression). When comparing HCC with and without OCT1 expression, no different sorafenib response was found. When tumors expressing OCT1 at the plasma membrane were considered separately, a marked longer survival was found (Log Rank p<0.001). No association between OCT1 expression at the plasma membrane with tumor stage, previous treatment with TACE or radiological response was seen.

In conclusion, these results indicate that the presence of OCT1 at the plasma membrane, rather than its expression levels, is related to better outcome of HCC patients treated with sorafenib.

The search for novel diagnostic and prognostic biomarkers in cholangiocarcinoma

The poor prognosis of cholangiocarcinoma (CCA) is in part due to late diagnosis, which is currently achieved by a combination of clinical, radiological and histological approaches. Available biomarkers determined in serum and biopsy samples to assist in CCA diagnosis are not sufficiently sensitive and specific. Therefore, the identification of new biomarkers, preferably those obtained by minimally invasive methods, such as liquid biopsy, is important. The development of innovative technologies has permitted to identify a significant number of genetic, epigenetic, proteomic and metabolomic CCA features with potential clinical usefulness in early diagnosis, prognosis or prediction of treatment response. Potential new candidates must be rigorously evaluated prior to entering routine clinical application. Unfortunately, to date, no such biomarker has achieved validation for these purposes. This review is an up-to-date of currently used biomarkers and the candidates with promising characteristics that could be included in the clinical practice in the next future. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Mechanisms of Resistance to Chemotherapy in Gastric Cancer

Although surgical resection is the standard curative therapy for gastric cancer, these tumors are often diagnosed at an advanced stage, when surgery is not recommended. Alternative treatments such as radiotherapy and chemotherapy achieve only very modest results. There is therefore an urgent need to advance in this field of oncologic gastroenterology. The poor response of gastric cancer to chemotherapy is usually due to a combination of mechanisms of chemoresistance (MOC), which may include a reduction in drug uptake (MOC-1a), enhanced drug efflux (MOC-1b), a reduced proportion of active agents in tumor cells due to a reduction in pro-drug activation or an enhancement in drug inactivation (MOC-2), changes in the expression/function of the molecular targets of anticancer drugs (MOC-3), an enhanced ability of cancer cells to repair anticancer drug-induced DNA damage (MOC-4), and decreased expression/function of pro-apoptotic factors or up-regulation of anti-apoptotic genes (MOC-5). Two major goals of modern pharmacology aimed at overcoming this situation are the prediction of a lack of response to chemotherapy and the identification of the underlying mechanisms accounting for primary or acquired refractoriness to anticancer drugs. These are important issues if we are to select the best pharmacological regime for each patient and develop novel strategies to overcome chemoresistance. The present review reports updated information regarding the mechanisms of chemoresistance (from MOC-1 to MOC-5) in gastric cancer, the advances made in the prediction of the failure of chemotherapeutic treatment, and novel strategies based on gene therapy currently being developed to treat these tumors.

Bile Acids in Physiology, Pathology and Pharmacology

Bile acids, synthesized by hepatocytes from cholesterol, are specific and quantitatively important organic components of bile, where they are the main driving force of the osmotic process that generates bile flow toward the canaliculus. The bile acid pool comprises a variety of species of amphipathic acidic steroids. They are not mere detergent molecules that play a key role in fat digestion and the intestinal absorption of hydrophobic compounds present in the intestinal lumen after meals, including liposoluble vitamins. They are now known to be involved in the regulation of multiple functions in liver cells, mainly hepatocytes and cholangiocytes, and also in extrahepatic tissues. The identification of nuclear receptors, such as farnesoid X receptor (FXR or NR1H4), and plasma membrane receptors, such as the G protein-coupled bile acid receptor (TGR5, GPBAR1 or MBAR), which are able to trigger specific and complex responses upon activation (with dissimilar sensitivities) by different bile acid molecular species and synthetic agonists, has opened a new and promising field of research whose implications extend to physiology, pathology and pharmacology. In addition, pharmacological development has taken advantage of advances in the understanding of the chemistry and biology of bile acids and the biological systems that interact with them, which in addition to the receptors include several families of transporters and export pumps, to generate novel bile acid derivatives aimed at treating different liver diseases, such as cholestasis, biliary diseases, metabolic disorders and cancer. This review is an update of the role of bile acids in health and disease.

Expert consensus document: Cholangiocarcinoma: current knowledge and future perspectives consensus statement from the European Network for the Study of Cholangiocarcinoma (ENS-CCA)

Cholangiocarcinoma (CCA) is a heterogeneous group of malignancies with features of biliary tract differentiation. CCA is the second most common primary liver tumour and the incidence is increasing worldwide. CCA has high mortality owing to its aggressiveness, late diagnosis and refractory nature. In May 2015, the "European Network for the Study of Cholangiocarcinoma" (ENS-CCA: www.enscca.org or www.cholangiocarcinoma.eu) was created to promote and boost international research collaboration on the study of CCA at basic, translational and clinical level. In this Consensus Statement, we aim to provide valuable information on classifications, pathological features, risk factors, cells of origin, genetic and epigenetic modifications and current therapies available for this cancer. Moreover, future directions on basic and clinical investigations and plans for the ENS-CCA are highlighted.

Effect of ursodeoxycholic acid treatment on the altered progesterone and bile acid homeostasis in the mother-placenta-foetus trio during cholestasis of pregnancy

AIM

Intrahepatic cholestasis of pregnancy (ICP) is characterized by pruritus and elevated bile acid concentrations in maternal serum. This is accompanied by an enhanced risk of intra-uterine and perinatal complications. High concentrations of sulphated progesterone metabolites (PMS) have been suggested to be involved in the multifactorial aetiopathogenesis of ICP. The aim of this study was to investigate further the mechanism accounting for the beneficial effect of oral administration of ursodeoxycholic acid (UDCA), which is the standard treatment, regarding bile acid and PMS homeostasis in the mother-placenta-foetus trio.

METHOD

Using HPLC-MS/MS bile acids and PMS were determined in maternal and foetal serum and placenta. The expression of ABC proteins in placenta was determined by real time quantitative PCR (RT-QPCR) and immunofluorescence.

RESULTS

In ICP, markedly increased concentrations of bile acids (tauroconjugates > glycoconjugates >> unconjugated), progesterone and PMS in placenta and maternal serum were accompanied by enhanced concentrations in foetal serum of bile acids, but not of PMS. UDCA treatment reduced bile acid accumulation in the mother-placenta-foetus trio, but had no significant effect on progesterone and PMS concentrations. ABCG2 mRNA abundance was increased in placentas from ICP patients vs. controls and remained stable following UDCA treatment, despite an apparent further increase in ABCG2.

CONCLUSION

UDCA administration partially reduces ICP-induced bile acid accumulation in mothers and foetuses despite the lack of effect on concentrations of progesterone and PMS in maternal serum. Up-regulation of placental ABCG2 may play an important role in protecting the foetus from high concentrations of bile acids and PMS during ICP.

Cocarcinogenic effects of intrahepatic bile acid accumulation in cholangiocarcinoma development

Bile acid accumulation in liver with cholangiolar neoplastic lesions may occur before cholestasis is clinically detected. Whether this favors intrahepatic cholangiocarcinoma development has been investigated in this study. The E. coli RecA gene promoter was cloned upstream from Luc2 to detect in vitro direct genotoxic ability by activation of SOS genes. This assay demonstrated that bile acids were not able to induce DNA damage. The genotoxic effect of the DNA-damaging agent cisplatin was neither enhanced nor hindered by the hepatotoxic and hepatoprotective glycochenodeoxycholic and glycoursodeoxycholic acids, respectively. In contrast, thioacetamide metabolites, but not thioacetamide itself, induced DNA damage. Thus, thioacetamide was used to induce liver cancer in rats, which resulted in visible tumors after 30 weeks. The effect of bile acid accumulation on initial carcinogenesis phase (8 weeks) was investigated in bile duct ligated (BDL) animals. Serum bile acid measurement and determination of liver-specific healthy and tumor markers revealed that early thioacetamide treatment induced hypercholanemia together with upregulation of the tumor marker Neu in bile ducts, which were enhanced by BDL. Bile acid accumulation was associated with increased expression of interleukin (IL)-6 and downregulation of farnesoid X receptor (FXR). Bile duct proliferation and apoptosis activation, with inverse pattern (BDL > thioacetamide + BDL >> thioacetamide vs. thioacetamide > thioacetamide + BDL > BDL), were observed. In conclusion, intrahepatic accumulation of bile acids does not induce carcinogenesis directly but facilitates a cocarcinogenic effect due to stimulation of bile duct proliferation, enhanced inflammation, and reduction in FXR-dependent chemoprotection.

IMPLICATIONS

This study reveals that bile acids foster cocarcinogenic events that impact cholangiocarcinoma.

Expression of SLC22A1 variants may affect the response of hepatocellular carcinoma and cholangiocarcinoma to sorafenib

Reduced drug uptake is an important mechanism of chemoresistance. Down-regulation of SLC22A1 encoding the organic cation transporter-1 (OCT1) may affect the response of hepatocellular carcinoma (HCC) and cholangiocarcinoma (CGC) to sorafenib, a cationic drug. Here we investigated whether SLC22A1 variants may contribute to sorafenib chemoresistance. Complete sequencing and selective variant identification were carried out to detect single nucleotide polymorphisms (SNPs) in SLC22A1 complementary DNA (cDNA). In HCC and CGC biopsies, in addition to previously described variants, two novel alternative spliced variants and three SNPs were identified. To study their functional consequences, these variants were mimicked by directed mutagenesis and expressed in HCC (Alexander and SK-Hep-1) and CGC (TFK1) cells. The two novel described variants, R61S fs*10 and C88A fs*16, encoded truncated proteins unable to reach the plasma membrane. Both variants abolished OCT1-mediated uptake of tetraethylammonium, a typical OCT1 substrate, and were not able to induce sorafenib sensitivity. In cells expressing functional OCT1 variants, OCT1 inhibition with quinine prevented sorafenib-induced toxicity. Expression of OCT1 variants in Xenopus laevis oocytes and determination of quinine-sensitive sorafenib uptake by high-performance liquid chromatography-dual mass spectrometry confirmed that OCT1 is able to transport sorafenib and that R61S fs*10 and C88A fs*16 abolish this ability. Screening of these SNPs in 23 HCC and 15 CGC biopsies revealed that R61S fs*10 was present in both HCC (17%) and CGC (13%), whereas C88A fs*16 was only found in HCC (17%). Considering all SLC22A1 variants, at least one inactivating SNP was found in 48% HCC and 40% CGC.

CONCLUSION

Development of HCC and CGC is accompanied by the appearance of aberrant OCT1 variants that, together with decreased OCT1 expression, may dramatically affect the ability of sorafenib to reach active intracellular concentrations in these tumors.

Genetic variants in genes involved in mechanisms of chemoresistance to anticancer drugs

Refractoriness to the pharmacological treatment of cancer is dependent on the expression levels of genes involved in mechanisms of chemoresistance and on the existence of genetic variants that may affect their function. Thus, changes in genes encoding solute carriers may account for considerable inter-individual variability in drug uptake and the lack of sensitivity to the substrates of these transporters. Moreover, changes in proteins involved in drug export can affect their subcellular localization and transport ability and hence may also modify the bioavailability of antitumor agents. Regarding pro-drug activation or drug inactivation, genetic variants are responsible for changes in the activity of drug-metabolizing enzymes, which affect drug clearance and may determine the lack of response to anticancer chemotherapy. The presence of genetic variants may also decrease the sensitivity to pharmacological agents acting through molecular targets or signaling pathways. Recent investigations suggest that changes in genes involved in DNA repair may affect the response to platinum-based drugs. Since most anticancer agents activate cell death pathways, the evasion of apoptosis plays an important role in chemoresistance. Several genetic variants affecting death-receptor pathways, the mitochondrial pathway, downstream caspases and their natural modulators, and the p53 pathway, whose elements are mutated in more than half of tumors, and survival pathways, have been reported. The present review summarizes the available data regarding the role of genetic variants in the different mechanisms of chemoresistance and discusses their potential impact in clinical practice and in the development of tools to predict and overcome chemoresistance.

Genetic variants in genes involved in mechanisms of chemoresistance to anticancer drugs

Refractoriness to the pharmacological treatment of cancer is dependent on the expression levels of genes involved in mechanisms of chemoresistance and on the existence of genetic variants that may affect their function. Thus, changes in genes encoding solute carriers may account for considerable inter-individual variability in drug uptake and the lack of sensitivity to the substrates of these transporters. Moreover, changes in proteins involved in drug export can affect their subcellular localization and transport ability and hence may also modify the bioavailability of antitumor agents. Regarding pro-drug activation or drug inactivation, genetic variants are responsible for changes in the activity of drug-metabolizing enzymes, which affect drug clearance and may determine the lack of response to anticancer chemotherapy. The presence of genetic variants may also decrease the sensitivity to pharmacological agents acting through molecular targets or signaling pathways. Recent investigations suggest that changes in genes involved in DNA repair may affect the response to platinum-based drugs. Since most anticancer agents activate cell death pathways, the evasion of apoptosis plays an important role in chemoresistance. Several genetic variants affecting death-receptor pathways, the mitochondrial pathway, downstream caspases and their natural modulators, and the p53 pathway, whose elements are mutated in more than half of tumors, and survival pathways, have been reported. The present review summarizes the available data regarding the role of genetic variants in the different mechanisms of chemoresistance and discusses their potential impact in clinical practice and in the development of tools to predict and overcome chemoresistance.

No correlation between the expression of FXR and genes involved in multidrug resistance phenotype of primary liver tumors

Farnesoid X receptor (FXR) has been recently reported to enhance chemoresistance through bile acid-independent mechanisms. Thus, FXR transfection plus activation with GW4064 resulted in reduced sensitivity to cisplatin-induced toxicity. This is interesting because primary tumors of the liver, an organ where FXR is expressed, exhibit marked refractoriness to pharmacological treatment. Here we have determined whether FXR is upregulated in hepatocellular carcinoma (HCC), cholangiocarcinoma (CGC) and hepatoblastoma (HPB) and whether this is related with the expression of genes involved in mechanisms of chemoresistance. Using RT-QPCR and Taqman low density arrays we have analyzed biopsies from healthy livers or surgically removed tumors from naive patients and cell lines derived from HCC (SK-HEP-1, Alexander and Huh7), CGC (TFK1) and HPB (HepG2), before and after exposure to cisplatin at IC50 for 72 h. In liver tumors FXR expression was not enhanced but significantly decreased (healthy liver > HCC > HPB ≈ CGC). Except for CGC, this was not accompanied by changes in the proportions of FXR isoforms. Changes in 36 genes involved in drug uptake/efflux and metabolism, expression/function of molecular targets, and survival/apoptosis balance were found. Changes affecting SLC22A1, CYP2A1 and BIRC5 were shared by HCC, CGC and HPB. Similarity in gene expression profiles between cell lines and parent tumors was found. Pharmacological challenge with cisplatin induced changes that increased this resemblance. This was not dependent upon FXR expression. Thus, although FXR may play a role in inducing chemoresistance under certain circumstances, its upregulation does not seem to be involved in the multidrug resistance phenotype characteristic of HCC, CGC and HPB.

Further characterization of the electrogenicity and pH sensitivity of the human organic anion-transporting polypeptides OATP1B1 and OATP1B3

Organic anion-transporting polypeptides (OATPs) are involved in the liver uptake of many endogenous and xenobiotic compounds, such as bile acids and drugs, respectively. Using Xenopus laevis oocytes and Chinese hamster ovary (CHO) cells expressing rat Oatp1a1, human OATP1B1, or OATP1B3, the sensitivity of these transporters to extracellular/intracellular pH (pHo/pHi) and changes in plasma membrane potential (ΔΨ) was investigated. In X. laevis oocytes, nonspecific plasma membrane permeability increased only at pHo below 4.5. Above this value, both using oocytes and CHO cells, extracellular acidification affected differently the specific transport of taurocholic acid (TCA) and estradiol 17β-d-glucuronide (E(2)17βG) by Oatp1a1 (stimulation), OATP1B1 (inhibition), and OATP1B3 (stimulation). Changes in substrate uptake in the presence of valinomycin (K(+)-ionophore), carbonyl cyanide 3-chlorophenylhydrazone and nigericin (protonophores), and amiloride (Na(+)/H(+)-inhibitor) and cation replacement in the medium were studied with fluorescent probes for measuring substrate uptake (cholylglycyl amidofluorescein) and changes in pHi (SNARF-4F) and ΔΨ [DilC(1)(5)]. The results suggest that activity of these three carriers is sodium/potassium-independent and affected differently by changes in pHo and ΔΨ: Oatp1a1 was confirmed to be an electroneutral anion exchanger, whereas the function of both OATP1B1 and OATP1B3 was markedly affected by the magnitude of ΔΨ. Moreover, electrophysiological measurements revealed the existence of a net anion influx associated to OATP1B1/OATP1B3-mediated transport of TCA, E(2)17βG, and estrone-3-sulfate. Furthermore, a leakage of Na(+) through OATP1B1 and OATP1B3, which is not coupled to substrate transport, was found. In conclusion, these results suggest that OATP1B1 and OATP1B3 are electrogenic transporters whose activity may be strongly affected under circumstances of displacement of local pH.

TNP-470 Inhibits Oxidative Stress, Nitric Oxide Production and Nuclear Factor Kappa B Activation in a Rat Model of Hepatocellular Carcinoma

The objective of this study is to determine if treatment with the angiogenesis inhibitor TNP-470 results in impairment of oxidative stress, inhibition of nuclear factor kappa B (NF-kappaB) activation and decrease of nitric oxide production in an experimental model of rat hepatocarcinogenesis. Tumour was induced by diethylnitrosamine and promoted by two-thirds hepatectomy plus acetaminofluorene administration. Experiments were carried out at 28 weeks after initiating the treatment. TNP-470 was administered at 30mg/kg, three times per week from 20 to 28 weeks. Carcinomatous tissue growing outside dysplastic nodules and a marked expression of placental glutathione S-transferase were detected in rats with induced carcinogenesis. Liver concentrations of thiobarbituric acid reactive substances, reduced glutathione (GSH) and glutathione disulfide (GSSG) were significantly higher than those of controls and there was a significant increase in the GSSG/GSH ratio. Tumour growth was accompanied by augmented expression of inducible nitric oxide synthase, activation of (NF-kappaB) and proteolysis of IkappaB. All these effects were absent in animals receiving TNP-470. Our results indicate that TNP-470 inhibits oxidative stress, nitric oxide production and NF-kappaB activation induced by experimental hepatocarcinogenesis. These changes would contribute to the beneficial effects of TNP-470 in cancer treatment.

Protective effect of bile acid derivatives in phalloidin-induced rat liver toxicity

Phalloidin causes severe liver damage characterized by marked cholestasis, which is due in part to irreversible polymerization of actin filaments. Liver uptake of this toxin through the transporter OATP1B1 is inhibited by the bile acid derivative BALU-1, which does not inhibit the sodium-dependent bile acid transporter NTCP. The aim of the present study was to investigate whether BALU-1 prevents liver uptake of phalloidin without impairing endogenous bile acid handling and hence may have protective effects against the hepatotoxicity induced by this toxin. In anaesthetized rats, i.v. administration of BALU-1 increased bile flow more than taurocholic acid (TCA). Phalloidin administration decreased basal (-60%) and TCA-stimulated bile flow (-55%) without impairing bile acid output. Phalloidin-induced cholestasis was accompanied by liver necrosis, nephrotoxicity and haematuria. In BALU-1-treated animals, phalloidin-induced cholestasis was partially prevented. Moreover haematuria was not observed, which was consistent with histological evidences of BALU-1-prevented injury of liver and kidney tissue. HPLC-MS/MS analysis revealed that BALU-1 was secreted in bile mainly in non-conjugated form, although a small proportion (<5%) of tauro-BALU-1 was detected. BALU-1 did not inhibit the biliary secretion of endogenous bile acids. When highly choleretic bile acids, - ursodeoxycholic (UDCA) and dehydrocholic acid (DHCA) - were administered, they were found less efficient than BALU-1 in preventing phalloidin-induced cholestasis. Biliary phalloidin elimination was low but it was increased by BALU-1>TCA>DHCA>UDCA. In conclusion, BALU-1 is able to protect against phalloidin-induced hepatotoxicity, probably due to an inhibition of the liver uptake and an enhanced biliary secretion of this toxin.

Cytosol-nucleus traffic and colocalization with FXR of conjugated bile acids in rat hepatocytes

Bile acids (BAs) are natural ligands of nuclear receptors, in particular farnesoid X receptor (FXR). Whether, in addition to protein-mediated cytosolic-nuclear BA translocation, other mechanisms are involved in the access of BAs to nuclear FXR was investigated. When rat hepatocytes were incubated with radiolabeled taurocholic acid, taurodeoxycholic acid, taurochenodeoxycholic acid, and tauroursodeoxycholic acid, their nuclear accumulation was proportional to their intracellular levels. With the use of flow cytometry analysis, the accumulation by nuclei isolated from rat liver cells was found to differ for several fluorescent compounds of similar molecular weight and different charge, including fluorescein-tagged BAs [cholylglycyl amidofluorescein (CGamF), ursodeoxycholylglycyl amidofluorescein, or chenodeoxycholylglycyl amidofluorescein]. When we varied nuclear volume by incubation with different sucrose concentrations, a similar relationship between nuclear volume and content of FITC and 4-kDa FITC-dextran was found. In contrast, this relationship was markedly lower for CGamF. Confocal microscopy studies revealed that fluorescein-tagged BAs, but also FITC or 10-kDa FITC-dextran were found in the nuclear envelope and concentrated in regions where DNA was less densely packed. In contrast to the cytosolic subcellular localization of peroxisome proliferator-activated receptor-alpha, FXR and nucleolin (a marker of transcriptional active chromatin) were also localized by immunoreactivity in these intranuclear regions. In conclusion, although intranuclear levels of small organic molecules including conjugated BAs depend on their concentrations in the extranuclear space, the existence of certain molecular selectivity (not strictly dependent on molecular weight or charge) suggests that, in addition to simple diffusional exchange, other mechanisms may be also involved in determining their overall nuclear content in regions where these compounds coincide and may interact with nuclear receptors such as FXR.

Molecular bases of the fetal liver-placenta-maternal liver excretory pathway for cholephilic compounds

Potentially toxic endogenous compounds, such as bile acids (BAs) and biliary pigments, as well as many xenobiotics, such as drugs and food components, are biotransformed and eliminated by the hepatobiliary system with the collaboration of the kidney. However, the situation is very different during pregnancy because the fetal liver produces biliary compounds despite the fact that this organ, owing to its immaturity, is not able to eliminate them into bile. Moreover, the excretory ability of the fetal kidneys is also very limited. Thus, during the intra-uterine life, the major route to eliminate fetal BAs and biliary pigments is their transfer to the mother across the placenta. The maternal liver and, to a lesser extent, the maternal kidney, are then in charge of their biotransformation and elimination into faeces and urine respectively. This review describes current knowledge of the machinery responsible for the detoxification and excretion of cholephilic compounds through the pathway formed by the fetal liver-placenta-maternal liver trio.

Expression, localization, and inducibility by bile acids of hepatobiliary transporters in the new polarized rat hepatic cell lines, Can 3−1 and Can 10

Sinusoidal and apical transporters are responsible for the uptake and biliary elimination of many compounds by hepatocytes. Few in vitro models are however available for analyzing such functions. The expression and bile-acid inducibility of 13 transporters and two nuclear receptors were investigated in the new rat polarized lines, Can 3-1 and Can 10, and in their unpolarized parent, Fao. The relative abundance of mRNA, the protein level, and their localization were examined by real-time quantitative PCR, Western blotting, immunofluorescence, and confocal microscopy. Compared with rat liver, mRNA levels of Fao cells were: negligible for Bsep/Abcb11; lower for the uptake transporters Ntcp and Oatps; similar for SHP, FXR, and Bcrp/Abcg2; and higher (four-fold to 160-fold) for the efflux pumps Mdr1b/Abcb1b, Mdr2/Abcb4, Mrp1/Abcc1, Mrp2/Abcc2, Mrp3/Abcc3, Abcg5, and Abcg8. This profile was mostly maintained (and improved for Bsep) in Can 10. Some transporters were less well expressed in Can 3-1. In both lines, sinusoidal (Ntcp, Mrp3) and canalicular transporters (Mdr-P-glycoproteins detected with C219 antibody, Mrp2) were localized at their correct poles. Bile-acid effects on polarity and mRNA levels of transporters were analyzed after a 6-day treatment with 50 microM taurocholic, chenodeoxycholic (CDCA), or ursodeoxycholic acid (UDCA). No polarization of Fao cells was induced; Can 10 and Can 3-1 polarity was maintained. CDCA and UDCA induced marked enhancement of the volume of Can 10 bile canaliculi. CDCA upregulated Bsep, Mdr2, SHP, Mdr1b, and Oatp2/1a4 in Can 10 (two- to seven-fold) and in Fao cells. Thus, Can 10 constitutes an attractive polarized model for studying vectorial hepatobiliary transport of endogenous and xenobiotic cholephilic compounds.