OAT, OATP, and MRP Drug Transporters and the Remote Sensing and Signaling Theory.

The coordinated movement of organic anions (e.g., drugs, metabolites, signaling molecules, nutrients, antioxidants, gut microbiome products) between tissues and body fluids depends, in large part, on organic anion transporters (OATs) [solute carrier 22 (SLC22)], organic anion transporting polypeptides (OATPs) [solute carrier organic (SLCO)], and multidrug resistance proteins (MRPs) [ATP-binding cassette, subfamily C (ABCC)]. Depending on the range of substrates, transporters in these families can be considered multispecific, oligospecific, or (relatively) monospecific. Systems biology analyses of these transporters in the context of expression patterns reveal they are hubs in networks involved in interorgan and interorganismal communication. The remote sensing and signaling theory explains how the coordinated functions of drug transporters, drug-metabolizing enzymes, and regulatory proteins play a role in optimizing systemic and local levels of important endogenous small molecules. We focus on the role of OATs, OATPs, and MRPs in endogenous metabolism and how their substrates (e.g., bile acids, short chain fatty acids, urate, uremic toxins) mediate interorgan and interorganismal communication and help maintain and restore homeostasis in healthy and disease states.

Inflammation alters the expression pattern of drug transporters during Caco-2 cell stimulation and azoxymethane-induced colon tumorigenesis.

Drug transporters play a pivotal role in modulating drug disposition and are subject to alterations under inflammatory conditions. This study aimed to elucidate the intricate expression patterns of drug transporters during both acute and chronic inflammation, which are closely linked to malignant transformation. To investigate acute inflammation, we employed an in vitro model by subjecting Caco-2 cells to various inflammatory stimuli (IL-1ß, TNF-α, or LPS) individually or in combination. The successful induction of inflammation was confirmed by robust increases in IL-6 and NO production. Notably, inflamed Caco-2 cells exhibited significantly diminished levels of ABCB1 and ABCG2, while the expression of ABCC2 was upregulated. For chronic inflammation induction in vivo, we employed the well-established AOM/DSS mouse model known for its association with colitis-driven tumorigenesis. Persistent inflammation was effectively monitored throughout the experiment via elevated IL-6 and NO levels. The sequential stages of tumorigenesis were confirmed through Ki-67 immunohistochemistry. Intriguingly, we observed gradual alterations in the expression patterns of the studied drug transporters during stepwise induction, with ABCB1, ABCG2, and ABCC1 showing downregulation and ABCC2 exhibiting upregulation. Immunohistochemistry further revealed dynamic changes in the expression of ABCB1 and ABCC2 during the induction cycles, closely paralleling the gradual increase in Ki-67 expression observed during the development of precancerous lesions. Collectively, our findings underscore the significant impact of inflammation on drug transporter expression, potentially influencing the process of malignant transformation of the colon.

Papillary renal neoplasm with reverse polarity is biologically and clinically distinct from eosinophilic papillary renal cell carcinoma.

Papillary renal neoplasm with reverse polarity (PRNRP) is a recently described indolent entity with distinct features and its recognition from other oncocytic/eosinophilic papillary renal cell carcinoma (ePRCC) has important prognostic implications. ABCC2, a renal drug transporter, is overexpressed in aggressive PRCCs. In this study, we compared the clinicopathological parameters and the biological ABCC2 expression between PRNRP and ePRCC. PRNRP (n = 8) and ePRCC (n = 21) cases were selected from resection specimens and corresponding clinicopathological data were collected. ABCC2 immunohistochemical (IHC) staining was performed and ABCC2 staining patterns were classified as negative, cytoplasmic, and brush-border. RNA in-situ hybridization (ISH) was used to assess ABCC2 transcript levels. All eight PRNRP cases had weak cytoplasmic ABCC2 IHC reactivity; however, they showed no detectable ABCC2 transcripts on RNA ISH. In comparison, 76% (16/21) of ePRCCs showed ABCC2 IHC brush-border expression and significantly higher ABCC2 RNA ISH transcript levels (p < 0.001). Additionally, the ePRCC group showed a significantly larger tumor size (p = 0.004), higher WHO/ISUP grade (p < 0.001), and stage (p = 0.044). None of the PRNRP cases showed disease progression, while 9.5% (2/21) ePRCCs had disease progression. PRNRP is clinically and biologically distinct from ePRCC. Hence, it is crucial to differentiate between these two entities, particularly in needle core biopsies.

Throwing Brazilian strains into the melting pot of P. xylostella resistance to Bacillus thuringiensis.

The resistance of pest insects to biopesticides based on the bacterium Bacillus thuringiensis (Bt) is normally associated with changes to the receptors involved in the mechanism of action of the pesticidal proteins produced by Bt. In some strains of Plutella xylostella (the diamondback moth) resistance has evolved through a signalling mechanism in which the genes encoding the receptor proteins are downregulated whereas in others it has been linked to structural changes in the receptors themselves. One such well characterized mutation is in the ABCC2 gene indicating that changes to this protein can result in resistance. However other studies have found that knocking out this protein does not result in a significant level of resistance. In this study we wanted to test the hypothesis that constitutive receptor downregulation is the major cause of Bt resistance in P. xylostella and that mutations in the now poorly expressed receptor genes may not contribute significantly to the phenotype. To that end we investigated the expression of a receptor (ABCC2) and the major regulator of the signalling pathway (MAP4K4) in two resistant and four susceptible strains. No correlation was found between expression levels and susceptibility; however, a frameshift mutation was identified in the ABCC2 receptor in a newly characterized resistant strain.

Extracellular Vesicles as Surrogates for the Regulation of the Drug Transporters ABCC2 (MRP2) and ABCG2 (BCRP).

Drug efflux transporters of the ATP-binding-cassette superfamily play a major role in the availability and concentration of drugs at their site of action. ABCC2 (MRP2) and ABCG2 (BCRP) are among the most important drug transporters that determine the pharmacokinetics of many drugs and whose overexpression is associated with cancer chemoresistance. ABCC2 and ABCG2 expression is frequently altered during treatment, thus influencing efficacy and toxicity. Currently, there are no routine approaches available to closely monitor transporter expression. Here, we developed and validated a UPLC-MS/MS method to quantify ABCC2 and ABCG2 in extracellular vesicles (EVs) from cell culture and plasma. In this way, an association between ABCC2 protein levels and transporter activity in HepG2 cells treated with rifampicin and hypericin and their derived EVs was observed. Although ABCG2 was detected in MCF7 cell-derived EVs, the transporter levels in the vesicles did not reflect the expression in the cells. An analysis of plasma EVs from healthy volunteers confirmed, for the first time at the protein level, the presence of both transporters in more than half of the samples. Our findings support the potential of analyzing ABC transporters, and especially ABCC2, in EVs to estimate the transporter expression in HepG2 cells.

ABCC2 brush-border expression predicts outcome in papillary renal cell carcinoma: a multi-institutional study of 254 cases.

AIMS: Papillary renal cell carcinoma (PRCC) histologic subtyping is no longer recommended in the 2022 WHO classification. Currently, WHO/ISUP nucleolar grade is the only accepted prognostic histologic parameter for PRCC. ABCC2, a renal drug transporter, has been shown to significantly predict outcomes in PRCC. In this study we evaluated the prognostic significance of ABCC2 IHC staining patterns in a large, multi-institutional PRCC cohort and assessed the association of these patterns with ABCC2 mRNA expression. METHODS AND RESULTS: We assessed 254 PRCCs for ABCC2 IHC reactivity patterns that were stratified into negative, cytoplasmic, brush-border <50%, and brush-border ≥50%. RNA in situ hybridization (ISH) was used to determine the transcript level of each group. Survival analysis was performed with SPSS and GraphPad software. RNA-ISH showed that the ABCC2 group with any brush-border staining was associated with a significant increase in the transcript level, when compared to the negative/cytoplasmic group (P = 0.034). Both ABCC2 groups with brush-border <50% (P = 0.024) and brush-border ≥50% (P < 0.001) were also associated with worse disease-free survival (DFS) in univariate analysis. Multivariate analysis showed that only ABCC2 IHC brush-border (<50% and ≥50%) reactivity groups (P = 0.037 and P = 0.003, respectively), and high-stage disease (P < 0.001) had a DFS of prognostic significance. In addition, ABCC2 brush-border showed significantly worse DFS in pT1a (P = 0.014), pT1 (P = 0.013), ≤4 cm tumour (P = 0.041) and high stage (P = 0.014) groups, while a similar analysis with high WHO/ISUP grade in these groups was not significant. CONCLUSION: ABCC2 IHC brush-border expression in PRCC correlates with significantly higher gene expression and also independently predicts survival outcomes.

Helicoverpa armigera GATAe transcriptional factor regulates the expression of Bacillus thuringiensis Cry1Ac receptor gene ABCC2 by its interplay with additional transcription factors.

Helicoverpa armigera is a worldwide pest that has been efficiently controlled by transgenic plants expressing Bt Cry toxins. To exert toxicity, Cry toxins bind to different receptors located in larval midgut cells. Previously, we reported that GATA transcription factor GATAe activates the expression of multiple H. armigera Cry1Ac receptors in different insect cell lines. Here, the mechanism involved in GATAe regulation of HaABCC2 gene expression, a key receptor of Cry1Ac, was analyzed. HaGATAe gene silencing by RNAi in H. armigera larvae confirmed the activation role of HaGATAe on the expression of HaABCC2 in the midgut. The contribution of all potential GATAe-binding sites was analyzed by site-directed mutagenesis using Hi5 cells expressing a reporter gene under regulation of different modified HaABCC2 promoters. DNA pull-down assays revealed that GATAe bound to different predicted GATA-binding sites and mutations of the different GATAe-binding sites identified two binding sites responsible for the promoter activity. The binding site B9, which is located near the transcription initiator site, has a major contribution on HaABCC2 expression. Also, DNA pull-down assays revealed that all other members of GATA TF family in H. armigera, besides GATAe, HaGATAa, HaGATAb, HaGATAc and HaGATAd also bound to the HaABCC2 promoter and decreased the GATAe dependent promoter activity. Finally, the potential participation in the regulation of HaABCC2 promoter of several TFs other than GATA TFs expressed in the midgut cells was analyzed. HaHR3 inhibited the GATAe dependent activity of the HaABCC2 promoter, while two other midgut-related TFs, HaCDX and HaSox21, also bound to the HaABCC2 promoter region and increased the GATAe dependent promoter activity. All these data showed that GATAe induces HaABCC2 expression by binding to HaGATAe binding sites in the promoter region and that additional TFs participate in modulating the HaGATAe-driven expression of HaABCC2.

Molecular and Clinical Links between Drug-Induced Cholestasis and Familial Intrahepatic Cholestasis.

Idiosyncratic Drug-Induced Liver Injury (iDILI) represents an actual health challenge, accounting for more than 40% of hepatitis cases in adults over 50 years and more than 50% of acute fulminant hepatic failure cases. In addition, approximately 30% of iDILI are cholestatic (drug-induced cholestasis (DIC)). The liver's metabolism and clearance of lipophilic drugs depend on their emission into the bile. Therefore, many medications cause cholestasis through their interaction with hepatic transporters. The main canalicular efflux transport proteins include: 1. the bile salt export pump (BSEP) protein (ABCB11); 2. the multidrug resistance protein-2 (MRP2, ABCC2) regulating the bile salts' independent flow by excretion of glutathione; 3. the multidrug resistance-1 protein (MDR1, ABCB1) that transports organic cations; 4. the multidrug resistance-3 protein (MDR3, ABCB4). Two of the most known proteins involved in bile acids' (BAs) metabolism and transport are BSEP and MDR3. BSEP inhibition by drugs leads to reduced BAs' secretion and their retention within hepatocytes, exiting in cholestasis, while mutations in the ABCB4 gene expose the biliary epithelium to the injurious detergent actions of BAs, thus increasing susceptibility to DIC. Herein, we review the leading molecular pathways behind the DIC, the links with the other clinical forms of familial intrahepatic cholestasis, and, finally, the main cholestasis-inducing drugs.

Map-based cloning and functional analysis revealed ABCC2 is responsible for Cry1Ac toxin resistance in Bombyx mori.

Bt toxins are parasporal crystals produced by Bacillus thuringiensis (Bt). They have specific killing activity against various insects and have been widely used to control agricultural pests. However, their widespread use has developed the resistance of many target insects. To maintain the sustainable use of Bt products, the resistance mechanism of insects to Bt toxins must be fully clarified. In this study, Bt-resistant and Bt-susceptible silkworm strains were used to construct genetic populations, and the genetic pattern of silkworm resistance to Cry1Ac toxin was determined. Sequence-tagged site molecular marker technology was used to finely map the resistance gene and to draw a molecular genetic linkage map, and the two closest markers were T1590 and T1581, indicating the resistance gene located in the 155 kb genetic region. After analyzing the sequence of the predicted gene in the genetic region, an ATP binding cassette transporter (ABCC2) was identified as the candidate gene. Molecular modeling and protein-protein docking result showed that a tyrosine insertion in the mutant ABCC2 might be responsible for the interaction between Cry1Ac and ABCC2. Moreover, CRISPR/Cas9-mediated genome editing technology was used to knockout ABCC2 gene. The homozygous mutant ABCC2 silkworm was resistant to Cry1Ac toxin, which indicated ABCC2 is the key gene that controls silkworm resistance to Cry1Ac toxin. The results have laid the foundation for elucidating the molecular resistance mechanism of silkworms to Cry1Ac toxin and could provide a theoretical basis for the biological control of lepidopteran pests.

Genotype-Phenotype Association in ABCC2 Exon 18 Missense Mutation Leading to Dubin-Johnson Syndrome: A Case Report.

We report a case of a patient with Dubin-Johnson syndrome confirmed by a genetic study. A 50-year-old woman who had symptoms of intermittent right upper quadrant abdominal pain was diagnosed with calculous cholecystitis at another institute and was presented to our hospital for a cholecystectomy. She had no history of liver disease, and her physical examination was normal. Abdominal computed tomography showed a gallbladder stone with chronic cholecystitis. During a laparoscopic cholecystectomy for cholecystitis, a smooth, black-colored liver was noted, and a liver biopsy was performed. The biopsy specimen showed coarse, dark brown granules in centrilobular hepatocytes via hematoxylin and eosin staining. We performed a genetic study using the blood samples of the patient. In the adenosine triphosphate-binding cassette subfamily C member 2 (ABCC2) mutation study, a missense mutation in exon 18 was noted. Based on the black-colored liver without nodularity, conjugated hyperbilirubinemia, the liver biopsy results of the coarse pigment in centrilobular hepatocytes, and the ABCC2 mutation, Dubin-Johnson syndrome was diagnosed. The patient was managed with conservative care using hepatotonics. One month after follow-up, total bilirubin and direct bilirubin remained in a similar range. Another follow-up was planned a month later, and the patient maintained her use of hepatotonics.

Association between ABCC2 polymorphism and hematological toxicity in patients with esophageal cancer receiving platinum plus 5-fluorouracil therapy.

BACKGROUND: Platinum agents are taken up into cells by copper transporter (CTR) 1 (gene code: SLC31A1) and are excreted from cells by copper-transporting P-type adenosine triphosphatase (ATP7B) and multidrug resistance-associated protein (MRP) 2 (gene code: ABCC2). In addition, glutathione S transferase (GST) P1 is involved in the metabolism of platinum agents. The present study aimed to determine whether the rate of grade 3-4 hematological toxicity associated with platinum plus 5-fluorouracil (5-FU) therapy in 239 patients with esophageal cancer was affected by the SLC31A1 rs10981694A>C and rs12686377G>T, ATP7B rs9535828A>G, GSTP1 rs1695A>G, and ABCC2 -24C>T polymorphisms. METHODS: Chemotherapy consisted of protracted infusion of 5-FU (800 mg/m2/day) on days 1-5 and cisplatin or nedaplatin (80 mg/m2/day) on day 1. RESULTS: A total of 82 of 239 patients developed grade 3-4 hematological toxicity after chemotherapy. Univariate analysis showed that ABCC2 -24C/T + T/T genotypes (P = 0.038), radiation therapy (P = 0.013), baseline white blood cell count < 6000/µL (P = 0.003), and baseline neutrophil count < 3900/µL (P = 0.021) were statistically significant predictors of grade 3-4 hematological toxicity. Multivariate analysis revealed that ABCC2 -24C/T + T/T genotypes (P = 0.036), radiation therapy (P = 0.005), and baseline white blood cell count < 6000/µL (P < 0.001) were significant risk factors. CONCLUSIONS: We determined that ABCC2 -24C>T is significantly associated with grade 3-4 hematological toxicity after platinum plus 5-FU therapy. These findings might contribute to improved treatment strategies for patients with esophageal cancer.

A Case of Dubin-Johnson Syndrome Presenting as Neonatal Cholestasis With Paucity of Interlobular Bile Ducts.

Dubin-Johnson syndrome (DJS) is a rare autosomal recessive disorder that typically manifests in young adulthood as jaundice with conjugated hyperbilirubinemia. We report a case presenting as neonatal cholestasis with the unexpected histologic finding of paucity of interlobular bile ducts, a feature that is not typically seen in DJS. The diagnosis was confirmed by absent canalicular multidrug-resistance-associated protein 2 (MRP2) immunohistochemical staining on liver biopsy tissue and molecular genetic testing that demonstrated heterozygous mutations in the ATP-Binding Cassette Subfamily C Member 2 (ABCC2) gene, including a novel missense mutation. This report describes a case of DJS with atypical clinicopathologic findings and suggests that DJS should be considered in patients with neonatal cholestasis and bile duct paucity.

Prediction model of human ABCC2/MRP2 efflux pump inhibitors: a QSAR study.

The overexpression of ABCC2/MRP2, an ATP-binding cassette transporter, contributes to multidrug resistance in cancer cells. In this study, a quantitative structure-activity relationship (QSAR) analysis on ABCC2 inhibitors has been carried out, aiming to establish a computational prediction model for ABCC2 modulators. Seven classification models and two regression models were built by SONNIA 4.2, and two other regression models were built by MOE 2008.10 based on a data set comprising 372 compounds collected from 16 relevant publications. The CPG-C iABCC2 model for classifying ABCC2 inhibitors has total accuracy of 0.88 and Matthews correlation coefficient MCC = 0.75. The CPG-C iEG model for classifying ABCC2 inhibitors (substrate EG: ß-estradiol 17-ß-D-glucuronide) has total accuracy of 0.91 and MCC = 0.82. The regression model PLS EG-IC50 for predicting ABCC2 inhibitors (substrate EG) gave root-mean-square error RMSE = 0.26, Q2 = 0.73 and [Formula: see text]. The regression model PLS CDCF-IC50 for predicting ABCC2 inhibitors [substrate CDCF: 5(6)-carboxy-2',7'-dichlorofluorescein] gave RMSE = 0.31, Q2 = 0.74 and [Formula: see text]. Four 2D-QSAR models were applied to 1661 compounds, with results indicating 369 compounds having the ability to reverse the efflux of both EG and CDCF by ABCC2, 152 among them having IC50 < 100 µM.

Increased ABCC2 expression predicts cisplatin resistance in non-small cell lung cancer.

Long-term use of platinum-based drugs can cause non-small cell lung cancer (NSCLC) to develop extremely strong drug resistance. Increasing the drug dosage does not have better treatment effects and could lead to serious complications. High levels of drug resistance are considered to be characteristic of human tumours and are usually mediated by genes related to multidrug resistance. Multidrug resistance-associated protein 2 (ABCC2), an ATP-binding cassette multidrug resistance transporter, was found to be overexpressed in various human cancers. In this study, we found that ABCC2 was also upregulated in cisplatin (DDP)-resistant A549 cells (A549/DDP). Functional studies demonstrated that ABCC2 knockdown reversed DDP resistance and promoted G1 phase arrest in A549/DDP cells, and PARP and caspase-3 were activated in A549/DDP cells following ABCC2 knockdown. In vivo, ABCC2 knockdown enhanced the cytotoxicity of DDP to subcutaneous A549 tumours. Together, these results suggest that ABCC2 may be a potential therapeutic strategy for overcoming DDP resistance in NSCLC patients. SIGNIFICANCE OF THE STUDY: In this study, we investigated the role of ABCC2 in cisplatin resistance of NSCLC cells. Our data show that ABCC2 expression was associated with resistance to cisplatin and that knockdown ABCC2 could reverse cisplatin resistance in NSCLC cells. Taken together, our study suggests that reducing the expression of ABCC2 could become an important strategy for enhancing the sensitivity of NSCLC cells to cisplatin.

Whole-exome sequencing identifies novel mutations in ABC transporter genes associated with intrahepatic cholestasis of pregnancy disease: a case-control study.

BACKGROUND: Intrahepatic cholestasis of pregnancy (ICP) can cause premature delivery and stillbirth. Previous studies have reported that mutations in ABC transporter genes strongly influence the transport of bile salts. However, to date, their effects are still largely elusive. METHODS: A whole-exome sequencing (WES) approach was used to detect novel variants. Rare novel exonic variants (minor allele frequencies: MAF < 1%) were analyzed. Three web-available tools, namely, SIFT, Mutation Taster and FATHMM, were used to predict protein damage. Protein structure modeling and comparisons between reference and modified protein structures were performed by SWISS-MODEL and Chimera 1.14rc, respectively. RESULTS: We detected a total of 2953 mutations in 44 ABC family transporter genes. When the MAF of loci was controlled in all databases at less than 0.01, 320 mutations were reserved for further analysis. Among these mutations, 42 were novel. We classified these loci into four groups (the damaging, probably damaging, possibly damaging, and neutral groups) according to the prediction results, of which 7 novel possible pathogenic mutations were identified that were located in known functional genes, including ABCB4 (Trp708Ter, Gly527Glu and Lys386Glu), ABCB11 (Gln1194Ter, Gln605Pro and Leu589Met) and ABCC2 (Ser1342Tyr), in the damaging group. New mutations in the first two genes were reported in our recent article. In addition, compared to the wild-type protein structure, the ABCC2 Ser1342Tyr-modified protein structure showed a slight change in the chemical bond lengths of ATP ligand-binding amino acid side chains. In placental tissue, the expression level of the ABCC2 gene in patients with ICP was significantly higher (P < 0.05) than that in healthy pregnant women. In particular, the patients with two mutations in ABC family genes had higher average values of total bile acids (TBA), aspartate transaminase (AST), direct bilirubin (DBIL), total cholesterol (CHOL), triglycerides (TG) and high-density lipoprotein (HDL) than the patients who had one mutation, no mutation in ABC genes and local controls. CONCLUSIONS: Our present study provide new insight into the genetic architecture of ICP and will benefit the final identification of the underlying mutations.

Association of polymorphism of CYP3A4, ABCB1, ABCC2, ABCG2, NFKB1, POR, and PXR with the concentration of cyclosporin A in allogeneic haematopoietic stem cell transplantation recipients.

Cyclosporin a (CsA) was characterized by a narrow therapeutic window and high interindividual pharmacokinetic variability. In this study, we aimed to identify the association of CYP3A4, ABCB1, ABCC2, ABCG2, NFKB1, POR, and PXR polymorphisms with CsA concentrations in patients with allogeneic haematopoietic cell transplantation (allo-HSCT) based on the route of administration.A total of 40 allo-HSCT recipients receiving CsA were genotyped for CYP3A4, ABCB1, ABCC2, ABCG2, NFKB1, POR, and PXR polymorphisms. The correlation between polymorphisms and CsA concentration was analysed.The CsA dose-adjusted trough concentration (Cssmin/D) of oral or intravenous administration was significantly different (p < 0.001). For CsA Cssmin/D of intravenous administration, CYP3A4 rs2246709 (p = 0.015), ABCC2 rs717620 (p = 0.024), ABCG2 rs2231142 (p = 0.042), PXR rs3732359 (p = 0.008), PXR rs3814058 (p = 0.028) and PXR rs6785049 (p < 0.001) had a significant effect on CsA Cssmin/D. For CsA Cssmin/D of oral administration, ABCC2 rs717620 (p = 0.009) and ABCG2 rs2231142 (p = 0.011) had a significant effect on CsA Cssmin/D.These results illustrated that the CYP3A4, ABCC2, ABCG2, and PXR genotypes were closely correlated with CsA Cssmin/D, suggesting these SNPs were suitable for determining the appropriate dose of CsA.

Molecular Regulation of Canalicular ABC Transporters.

The ATP-binding cassette (ABC) transporters expressed at the canalicular membrane of hepatocytes mediate the secretion of several compounds into the bile canaliculi and therefore play a key role in bile secretion. Among these transporters, ABCB11 secretes bile acids, ABCB4 translocates phosphatidylcholine and ABCG5/G8 is responsible for cholesterol secretion, while ABCB1 and ABCC2 transport a variety of drugs and other compounds. The dysfunction of these transporters leads to severe, rare, evolutionary biliary diseases. The development of new therapies for patients with these diseases requires a deep understanding of the biology of these transporters. In this review, we report the current knowledge regarding the regulation of canalicular ABC transporters' folding, trafficking, membrane stability and function, and we highlight the role of molecular partners in these regulating mechanisms.

Wilson disease, ABCC2 c.3972C > T polymorphism and primary liver cancers: suggestions from a familial cluster.

BACKGROUND: Polymorphisms in genes modulating xenobiotics metabolism, in particular the ABCC2 c.3972C > T single nucleotide polymorphism (SNP) at exon 28, have been suggested to increase primary liver cancer (PLC) risk. Conversely, the occurrence of PLCs in Wilson disease patients is a rare event, in contrast with the occurrence observed in other chronic liver diseases. Here we report the clinical case of five siblings carrying the ABCC2 c.3972C > T SNP; three of them were affected by Wilson disease and two brothers with Wilson disease also developed PLCs. METHODS: The presence of the ABCC2 c.3972C > T SNP was assessed by Sanger sequencing and the exposure of PLC risk factors by standardized questionnaires. RESULTS: Notably, PLCs occurred only in the two brothers with the ABCC2 c.3972C > T SNP and Wilson disease who resulted exposed to asbestos and cigarette smoking, but not in the other siblings with the ABCC2 c.3972C > T SNP, alone or in association with Wilson disease, not exposed to these carcinogens and/or to other known risk factors for PLCs. CONCLUSIONS: These findings suggest that ABCC2 c.3972C > T SNP and WD, also in association, may not represent a sufficient condition for PLC development, but that co-occurrence of further host/exogenous risk factors are needed to drive this process, reinforcing the notion that liver carcinogenesis is the result of a complex interplay between environmental and host genetic determinants. Due to the sporadic cases of this study and the paucity of data currently available in literature on this issue, future investigations in a larger population are needed to confirm our findings.

Genetic contribution of ABCC2 to Dubin-Johnson syndrome and inherited cholestatic disorders.

BACKGROUND AND AIMS: The ABCC2 gene is implicated in Dubin-Johnson syndrome (DJS), a rare autosomal recessive liver disorder. The primary aim of this study was to determine the diagnostic value of ABCC2 genetic testing in the largest cohort of DJS reported to date. The high number of patients with cholestatic manifestations in this series prompted us to evaluate the genetic contribution of rare, potentially pathogenic ABCC2 variants to other inherited cholestatic disorders. METHODS: The cohort study included 32 patients with clinical DJS diagnosis, and 372 patients referred for the following disorders: low phospholipid-associated cholelithiasis (LPAC) syndrome, intrahepatic cholestasis of pregnancy (ICP) and benign recurrent intrahepatic cholestasis (BRIC). ABCC2 was screened by next-generation sequencing. RESULTS: Most patients with clinical DJS had positive genetic diagnosis (n = 30; 94%), with a great diversity of point mutations and copy number variations in ABCC2. Strikingly, eight (27%) of these patients showed transient cholestatic features at presentation: four neonatal cholestasis, two ICP, one contraceptive-induced cholestasis and one sporadic cholestasis. Conversely, the frequency of rare, heterozygous, potentially pathogenic ABCC2 variants in patients with LPAC, ICP or BRIC did not differ significantly from that of the general population. CONCLUSIONS: This large series reveals that DJS is a highly homogeneous Mendelian disorder involving a large spectrum of ABCC2 variants. Genetic testing is crucial to establish early DJS diagnosis in patients with atypical presentations, such as neonatal cholestasis. This study also provides no evidence for the contribution of rare, potentially pathogenic ABCC2 variants to other inherited cholestatic disorders.

Effect of cyclosporine a and polymorphisms in CYP2C19 and ABCC2 on the concentration of voriconazole in patients undergoing allogeneic hematopoietic stem cell transplantation.

1. Voriconazole is known to display highly variable pharmacokinetics affecting treatment efficacy and safety. This study aimed to identify the factors causing the variation of voriconazole concentration in patients with allogeneic hematopoietic stem cell transplantation.2. The data of patients was collected, including clinical characteristics and voriconazole concentrations. A total of 5 single nucleotide polymorphisms of 3 candidate genes (CYP2C19, ABCC2, ABCG2) related to voriconazole metabolism were genotyped by MassArray method. The correlation between polymorphisms and voriconazole concentration was analyzed.3. A total of 244 voriconazole concentrations of 43 patients were included in this study. The voriconazole concentration was significantly correlated with patients' total bile acid (p = 0.001) and cyclosporin A (p < 0.001). The median concentration of the CYP2C19 normal metabolizers was remarkably lower than poor metabolizers (0.86 vs 2.27 µg/mL). The median concentration of ABCC2 rs2273697 GG genotype carriers was significantly higher than that of GA genotype carriers (p = 0.026).4. The variability of voriconazole concentration is partially explained by total bile acid, metabolic types of CYP2C19. The voriconazole concentration of CYP2C19 normal metabolizers is likely to be lower than 1.0 µg/mL and thus at risk of infection due to inadequate treatment.