CYP2B6 metabolizes many drugs, and its expression varies greatly. CYP2B6 genotype-phenotype associations were determined using human livers that were biochemically phenotyped for CYP2B6 (mRNA, protein, and CYP2B6 activity), and genotyped for CYP2B6 coding and 5Ј-flanking regions. CYP2B6 expression differed significantly between sexes. Females had higher amounts of CYP2B6 mRNA (3.9-fold, P Ͻ 0.001), protein (1.7-fold, P Ͻ 0.009), and activity (1.6-fold, P Ͻ 0.05) than did male subjects. Furthermore, 7.1% of females and 20% of males were poor CYP2B6 metabolizers. Striking differences among different ethnic groups were observed: CYP2B6 activity was 3.6-and 5.0-fold higher in Hispanic females than in Caucasian (P Ͻ 0.022) or African-American females (P Ͻ 0.038). Ten single nucleotide polymorphisms (SNPs) in the CYP2B6 promoter and seven in the coding region were found, including a newly identified 13072AϾG substitution that resulted in an Lys139Glu change. Many CYP2B6 splice variants (SV) were observed, and the most common variant lacked exons 4 to 6. A nonsynonymous SNP in exon 4 (15631GϾT), which disrupted an exonic splicing enhancer, and a SNP 15582CϾT in an intron-3 branch site were correlated with this SV. The extent to which CYP2B6 variation was a predictor of CYP2B6 activity varied according to sex and ethnicity. The 1459CϾT SNP, which resulted in the Arg487Cys substitution, was associated with the lowest level of CYP2B6 activity in livers of females. The intron-3 15582CϾT SNP (in significant linkage disequilibrium with a SNP in a putative hepatic nuclear factor 4 (HNF4) binding site) was correlated with lower CYP2B6 expression in females. In conclusion, we found several common SNPs that are associated with polymorphic CYP2B6 expression.

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The multicenter retrospective study conducted in 38 centers from 20 countries including 172 adult patients with CNS MM aimed to describe the clinical and pathological characteristics and outcomes of patients with multiple myeloma (MM) involving the central nervous system (CNS). Univariate and multivariate analyses were performed to identify prognostic factors for survival. The median time from MM diagnosis to CNS MM diagnosis was 3 years. Thirty-eight patients (22%) were diagnosed with CNS involvement at the time of initial MM diagnosis and 134 (78%) at relapse/progression. Upon diagnosis of CNS MM, 97% patients received initial therapy for CNS disease, of which 76% received systemic therapy, 36% radiotherapy and 32% intrathecal therapy. After a median follow-up of 3.5 years, the median overall survival (OS) from the onset of CNS involvement for the entire group was 7 months. Untreated and treated patients had median OS of 2 and 8 months, respectively (p<0.001). At least one previous line of therapy for MM before the diagnosis of CNS disease and >1 cytogenetic abnormality detected by FISH were independently associated with worse OS. The median OS for patients with 0, 1 and 2 of these risk factors were 25 months, 5.5 months and 2 months, respectively (p<0.001). Neurological manifestations, not considered chemotherapy-related, observed at any time after initial diagnosis of MM should raise a suspicion of CNS involvement. Although prognosis is generally poor, the survival of previously untreated patients and patients with favorable cytogenetic profile might be prolonged due to systemic treatment and/or radiotherapy.

Hepatocyte transplantation to treat liver disease is largely limited by the availability of useful cells. Amniotic epithelial cells (hAECs) from term human placenta express surface markers and genes characteristic of embryonic stem cells and have the ability to differentiate into all three germ layers, including tissues of endodermal origin (i.e. liver). Thus, hAECs could provide a source of stem cell-derived hepatocytes for transplantation. We investigated the differentiation of hAECs in vitro and after transplantation into the liver of SCID/Beige mice. Moreover, we tested the ability of rat amniotic epithelial cells (rAECs) to replicate and differentiate upon transplantation into a syngenic model of liver repopulation. In vitro results indicate that the presence of extracellular matrix proteins together with a cocktail of growth factors, cytokines and hormones are required for differentiation of hAECs into hepatocyte-like cells. Differentiated hAECs expressed hepatocyte markers at levels comparable to those of fetal hepatocytes. They were able to metabolize ammonia, testosterone and 17α-hydroxyprogesterone caproate, and expressed inducible fetal cytochromes. After transplantation into the liver of Retrorsine (RS) treated SCID/beige mice, naïve hAECs differentiated into hepatocyte-like cells which expressed mature liver genes such as cytochromes, plasma proteins, transporters and other hepatic enzymes at levels equal to adult liver tissue. When transplanted in a syngenic animal pretreated with RS, rAECs were able to engraft and generate a progeny of cells with morphology and protein expression typical of mature hepatocytes. Conclusion amniotic epithelial cells possess the ability to differentiate into cells with characteristics of functional hepatocytes, in vitro and in vivo, thus representing a useful and non controversial source of cells for transplantation.

In recent years, stem cells have been the subject of increasing scientific interest because of their utility in numerous biomedical applications. Stem cells are capable of renewing themselves; that is, they can be continuously cultured in an undifferentiated state, giving rise to more specialized cells of the human body such as heart, liver, bone marrow, blood vessel, pancreatic islet, and nerve cells. Therefore, stem cells are an important new tool for developing unique, in vitro model systems to test drugs and chemicals and a potential to predict or anticipate toxicity in humans. The following review provides an overview of the applications of stem cell technology in the area of toxicology. Specifically, this review addresses core technologies that are emerging in the field and how they could fulfill critical safety issues such as QT prolongation and hepatotoxicity, two leading causes of failures in preclinical development of new therapeutic drugs. We report how adult stem cells derived from various sources, such as human bone marrow and placenta, can potentially generate suitable models for cardiotoxicity, hepatotoxicity, genotoxicity/epigenetic and reproductive toxicology screens. Additionally, this review addresses the role and advantages of embryonic stem cells in the aforementioned models for toxicity and how genetic selection is employed to overcome major limitations to the implementation of stem cell-based in vitro models for toxicology.