Hepatic safety of voriconazole after allogeneic hematopoietic stem cell transplantation

Voriconazole is increasingly used in allogeneic hematopoietic stem cell transplantation (HSCT) for prophylaxis and treatment of fungal infections. Hepatic dysfunction is common in patients undergoing HSCT and may have an impact on the clinical decision to institute voriconazole. We conducted a retrospective review of all adult and pediatric HSCT recipients who received >2 consecutive doses of voriconazole between January 2005 and February 2008. Clinical hepatotoxicity was defined as the subjective attribution of liver enzyme elevation (even a mild one) to hepatotoxicity because of voriconazole by the treating physician and leading to discontinuation of voriconazole. Biochemical hepatotoxicity was defined as an elevation in one or more liver enzymes to >3 times the upper limit of normal or >3 times the baseline value if abnormal at baseline. Liver enzymes assessed included aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and total bilirubin. Simple and multiple logistic regressions were used to define the risks for hepatic dysfunction. The Wilcoxon signed-rank test was used to assess the differences in liver function test values before, during, and after the use of voriconazole. Sixty-eight of 200 patients (34%) developed hepatotoxicity while on voriconazole. The median duration of voriconazole therapy was 72 days (range, 1-804 days). Biochemical hepatotoxicity occurred in 51 patients (75%); clinical hepatotoxicity, in 17 patients (25%). Thirty-five (51%) of the patients with hepatotoxicity required discontinuation of therapy. In simple logistic regression, acute graft-versus-host disease (GVHD) was a risk factor for hepatotoxicity, and receipt of a T-cell depleted allograft was protective. In multiple logistic regression, acute GVHD (P = .002) remained significant. There were no cases of liver failure or death attributed to voriconazole. In this cohort of patients undergoing allogeneic HSCT, the rate of hepatotoxicity while on voriconazole was 34%. In general, the hepatic dysfunction was mild and reversible. Voriconazole therapy with monitoring appears to be reasonably safe for use in HSCT recipients at high risk for invasive fungal infections.

Molecular dissection of NRG1-ERBB4 signaling implicates PTPRZ1 as a potential schizophrenia susceptibility gene

Neuregulin and the neuregulin receptor ERBB4 have been genetically and functionally implicated in schizophrenia. In this study, we used the yeast two-hybrid system to identify proteins that interact with ERBB4, to identify genes and pathways that might contribute to schizophrenia susceptibility. We identified the MAGI scaffolding proteins as ERBB4-binding proteins. After validating the interaction of MAGI proteins with ERBB4 in mammalian cells, we demonstrated that ERBB4 expression, alone or in combination with ERBB2 or ERBB3, led to the tyrosine phosphorylation of MAGI proteins, and that this could be further enhanced with receptor activation by neuregulin. As MAGI proteins were previously shown to interact with receptor phosphotyrosine phosphatase beta/zeta (RPTPbeta), we postulated that simultaneous binding of MAGI proteins to RPTPbeta and ERBB4 forms a phosphotyrosine kinase/phosphotyrosine phosphatase complex. Studies in cultured cells confirmed both a spatial and functional association between ERBB4, MAGI and RPTPbeta. Given the evidence for this functional association, we examined the genes coding for MAGI and RPTPbeta for genetic association with schizophrenia in a Caucasian United Kingdom case-control cohort (n= approximately 1400). PTPRZ1, which codes for RPTPbeta, showed significant, gene-wide and hypothesis-wide association with schizophrenia in our study (best individual single-nucleotide polymorphism allelic P=0.0003; gene-wide P=0.0064; hypothesis-wide P=0.026). The data provide evidence for a role of PTPRZ1, and for RPTPbeta signaling abnormalities, in the etiology of schizophrenia. Furthermore, the data indicate a role for RPTPbeta in the modulation of ERBB4 signaling that may in turn provide further support for an important role of neuregulin/ERBB4 signaling in the molecular basis of schizophrenia.

Genomic expression analysis implicates Wnt signaling pathway and extracellular matrix alterations in hepatic specification and differentiation of murine hepatic stem cells

HBC-3 hepatic stem cells maintained in the undifferentiated state can be induced to differentiate along the hepatocyte lineage in response to DMSO (Rogler, 1997). In order to understand the complex transcriptional regulatory mechanisms associated with the differentiation of these somatic stem cells and to identify novel candidate stem cell and differentiation associated genes, we have begun to characterize the transcriptome of HBC-3 cells during a 7-day differentiation protocol. This analysis showed that differentiating HBC-3 cells undergo biphasic bursts of gene regulation peaking at 3 hours and 120 hours of DMSO treatment. In the undifferentiated state, HBC-3 cells express muscle, neuron, myeloid, and lymphoid specific genes that are rapidly downregulated during hepatocytic differentiation. Cluster analysis has revealed large groups of genes with different temporal regulation profiles demonstrating complex and widespread transcriptional changes. Specifically, we discovered a multifaceted downregulation of the Wnt/beta-catenin pathway accompanied by the repression of TCF target genes during HBC-3 differentiation. In addition, there is downregulation of cellular receptors for fibronectin and laminin and other extracellular matrix molecules indicative of widespread cell surface alterations. DMSO induces cell cycle arrest, and this is reflected in upregulation of growth inhibitory proteins such as cyclin I and p18 and downregulation of cyclins B1 and D. Genes needed for hepatocytic functions, such as apolipoprotein C-IV, phosphoenolpyruvate carboxykinase, alcohol dehydrogenase, and asialoglycoprotein receptor were upregulated. Finally, transcriptional regulators including Twist, Snail, HNF1a, and GATA6 were upregulated during differentiation of HBC-3 cells. The significance of these findings is that our genome-based approach has allowed the parallel identification of multiple regulatory pathways that is needed to begin to fully understand the complex differentiation process.