Idiosyncratic drug-induced liver injury (DILI) is a common cause for drug withdrawal from the market and although infrequent, DILI can result in serious clinical outcomes including acute liver failure and the need for liver transplantation. Eliminating the iatrogenic "harm" caused by a therapeutic intent is a priority in patient care. However, identifying culprit drugs and individuals at risk for DILI remains challenging. Apart from genetic factors predisposing individuals at risk, the role of the drugs' physicochemical and toxicological properties and their interactions with host and environmental factors need to be considered. The influence of these factors on mechanisms involved in DILI is multi-layered. In this review, we summarize current knowledge on 1) drug properties associated with hepatotoxicity, 2) host factors considered to modify an individuals' risk for DILI and clinical phenotypes, and 3) drug-host interactions. We aim at clarifying knowledge gaps needed to be filled in as to improve risk stratification in patient care. We therefore broadly discuss relevant areas of future research. Emerging insight will stimulate new investigational approaches to facilitate the discovery of clinical DILI risk modifiers in the context of disease complexity and associated interactions with drug properties, and hence will be able to move towards safety personalized medicine.

Sirtuins are nicotinamide adenine dinucleotide oxidized form (NAD 1 )-dependent deacetylases and function in cellular metabolism, stress resistance, and aging. For sirtuin7 (SIRT7), a role in ribosomal gene transcription is proposed, but its function in cancer has been unclear. In this study we show that SIRT7 expression was up-regulated in a large cohort of human hepatocellular carcinoma (HCC) patients. SIRT7 knockdown influenced the cell cycle and caused a significant increase of liver cancer cells to remain in the G 1 /S phase and to suppress growth. This treatment restored p21, induced Beclin-1, and repressed cyclin D1. In addition, sustained suppression of SIRT7 reduced the in vivo tumor growth rate in a mouse xenograft model. To explore mechanisms in SIRT7 regulation, microRNA (miRNA) profiling was carried out. This identified five significantly down-regulated miRNAs in HCC. Bioinformatics analysis of target sites and ectopic expression in HCC cells showed that miR-125a-5p and miR-125b suppressed SIRT7 and cyclin D1 expression and induced p21 WAF1/Cip1 -dependent G 1 cell cycle arrest. Furthermore, treatment of HCC cells with 5-aza-2 0 -deoxycytidine or ectopic expression of wildtype but not mutated p53 restored miR125a-5p and miR-125b expression and inhibited tumor cell growth, suggesting their regulation by promoter methylation and p53 activity. To show the clinical significance of these findings, mutations in the DNA binding domain of p53 and promoter methylation of miR125b were investigated. Four out of nine patients with induced SIRT7 carried mutations in the p53 gene and one patient showed hypermethylation of the miR-125b promoter region. Conclusion: Our findings suggest the oncogenic potential of SIRT7 in hepatocarcinogenesis. A regulatory loop is proposed whereby SIRT7 inhibits transcriptional activation of p21 WAF1/Cip1 by way of repression of miR-125a-5p and miR-125b. This makes SIRT7 a promising target in cancer therapy. (HEPATOLOGY 2013;57:1055-1067 S irtuins, also designated as class III histone deacetylases, are nicotinamide adenine dinucleotide oxidized form (NAD þ )-dependent deacetylases that target histone and nonhistone proteins and are implicated in the control of a wide range of biological processes such as apoptosis, stress responses, DNA repair, cell cycle, metabolism, and senescence. 1 The importance of sirtuins is demonstrated by their role in several major human pathologic conditions, including cancer, diabetes, cardiovascular disease, and neurodegenerative disease. 2 Mammals express seven sirtuins (denoted SIRT1-7) that have considerably different functions and catalytic activities. 3 The most closely related to yeast Sir2 and the best-characterized sirtuin, Abbreviations: 5-aza-dC, 5-aza-2 0 -deoxycytidine; CDKN1A, cyclin dependent kinase 1A;

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Drug-induced liver injury (DILI) is a leading cause of drug failure in clinical trials and a major reason for drug withdrawals from the market. Although there is evidence that dosages of !100 mg/day are associated with increased risk for hepatotoxicity, many drugs are safe at such dosages. There is an unmet need to predict risk for DILI more reliably, and lipophilicity might be a contributing factor. We analyzed the combined factors of daily dose and lipophilicity for 164 US Food and Drug Administration-approved oral medications and observed high risk for hepatotoxicity (odds ratio [OR], 14.05; P < 0.001) for drugs given at dosages !100 mg/day and octanol-water partition coefficient (logP) !3. This defined the ''rule-of-two.'' Similar results were obtained for an independent set of 179 oral medications with 85% of the rule-of-two positives being associated with hepatotoxicity (OR, 3.89; P < 0.01). Using the World Health Organization's Anatomical Therapeutic Chemical classification system, the rule-of-two performed best in predicting DILI in seven therapeutic categories. Among 15 rule-of-two positives, 14 were withdrawn from hepatotoxic drugs, and one was over-the-counter medication labeled for liver injury. We additionally examined drug pairs that have similar chemical structures and act on the same molecular target but differ in their potential for DILI. Again, the rule-of-two predicted hepatotoxicity reliably. Finally, the rule-of-two was applied to clinical case studies to identify hepatotoxic drugs in complex comedication regimes to further demonstrate its use. Conclusion: Apart from dose, lipophilicity contributes significantly to risk for hepatotoxicity. Applying the rule-of-two is an appropriate means of estimating risk for DILI compared with dose alone. (HEPATOLOGY 2013;58:388-396)

Numerous studies have established the pivotal role of liver-enriched transcription factors in organ development and cellular function, and there is conclusive evidence for transcription factors to act in concert in liver-specific gene expression. During organ development and in progenitor cells the timely expression of certain transcription factors is necessary for cellular differentiation, and there is overwhelming evidence for hierarchical and cooperative principles in a networked environment of transcription factors. The search for molecular switches that control stem cell imprinting and liver-specific functions has lead to the discovery of many interactions between such different molecules as transcription factors, coactivators, corepressors, enzymes, DNA, and RNA. Many of these interactions either repress or activate liver-specific gene expression. It thus can be demonstrated that specific mutational changes in liver-enriched transcription factors lead to altered intermolecular interactions with the consequence of human disease. This review provides an overview of our current knowledge about liver-enriched transcription factors and their role in liver function and development. We review the basic principles of gene transcription, the role of liver-enriched transcription factors in liver gene regulation, and the classification of transcription factors by their DNA-binding domains.

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Toxicogenomics enjoyed considerable attention as a ground-breaking addition to conventional toxicology assays at its inception. However, the pace at which toxicogenomics was expected to perform has been tempered in recent years. Next to cost, the lack of advanced knowledge discovery and data mining tools significantly hampered progress in this new field of toxicological sciences. Recently, two of the largest toxicogenomics databases were made freely available to the public. These comprehensive studies are expected to stimulate knowledge discovery and development of novel data mining tools, which are essential to advance this field. In this review, we provide a concise summary of each of these two databases with a brief discussion on the commonalities and differences between them. We place our emphasis on some key questions in toxicogenomics and how these questions can be appropriately addressed with the two databases. Finally, we provide a perspective on the future direction of toxicogenomics and how new technologies such as RNA-Seq may impact this field.

Drug-induced liver injury (DILI) is a major public health concern, and improving its prediction remains an unmet challenge. Recently, we reported the Rule-of-2 (RO2) and found lipophilicity (logP 3) and daily dose 100 mg of oral medications to be associated with significant risk for DILI; however, the RO2 failed to estimate grades of DILI severity. In an effort to develop a quantitative metrics, we analyzed the association of daily dose, logP, and formation of reactive metabolites (RM) in a large set of Food and Drug Administration-approved oral medications and found factoring RM into the RO2 to highly improve DILI prediction. Based on these parameters and by considering n 5 354 drugs, an algorithm to assign a DILI score was developed. In univariate and multivariate logistic regression analyses the algorithm (i.e., DILI score model) defined the relative contribution of daily dose, logP, and RM and permitted a quantitative assessment of risk of clinical DILI. Furthermore, a clear relationship between calculated DILI scores and DILI risk was obtained when applied to three independent studies. The DILI score model was also functional with drug pairs defined by similar chemical structure and mode of action but divergent toxicities. Specifically, for drug pairs where the RO2 failed, the DILI score correctly identified toxic drugs. Finally, the model was applied to n 5 159 clinical cases collected from the National Institutes of Health's LiverTox database to demonstrate that the DILI score correlated with the severity of clinical outcome. Conclusions: Based on daily dose, lipophilicity, and RM, a DILI score algorithm was developed that provides a scale of assessing the severity of DILI risk in humans associated with oral medications. (HEPATOLOGY 2016;64:931-940) A lthough animal studies are mandatory for investigational new drug approvals by regulatory agencies, (1,2) a retrospective analysis revealed such tests to fail in predicting risk for drug-induced liver injury (DILI) in about 45% of clinical trials. (3) The findings reinforce the need to improve the prediction power of DILI model more reliably and to define contributing factors. (4) Recently, we demonstrated that oral medications of high lipophilicity (i.e., logP 3) administered at daily doses of 100 mg are associated with an increased risk of developing DILI, which led us to develop the concept of the "Rule-of-2" (RO2). (5) It was stated that the RO2 added value in predicting risk for developing DILI but fell short of foreseeing severity. (6,7) Incorporating additional factors, especially those relevant to mechanisms of DILI, (8) facilitates the development of a quantitative metrics by considering relevant factors. Covalent binding of reactive metabolites (RM) is a frequently cited mechanism and was shown to cause liver injury through direct toxicity events (9) or by endorsing immune reactions. (10) This prompted us to investigate the relationship between the RO2 and RM for the development of a quantitative measure in predicting risk for DILI.Numerous drug...