Emma E. Furth

Liver failure and defective hepatocyte regeneration in interleukin-6-deficient mice.

Liver regeneration stimulated by a loss of liver mass leads to hepatocyte and nonparenchymal cell proliferation and rapid restoration of liver parenchyma. Mice with targeted disruption of the interleukin-6 (IL-6) gene had impaired liver regeneration characterized by liver necrosis and failure. There was a blunted DNA synthetic response in hepatocytes of these mice but not in nonparenchymal liver cells. Furthermore, there were discrete G1 phase (prereplicative stage in the cell cycle) abnormalities including absence of STAT3 (signal transducer and activator of transcription protein 3) activation and depressed AP-1, Myc, and cyclin D1 expression. Treatment of IL-6-deficient mice with a single preoperative dose of IL-6 returned STAT3 binding, gene expression, and hepatocyte proliferation to near normal and prevented liver damage, establishing that IL-6 is a critical component of the regenerative response.

Augmentation of tumor angiogenesis by a Myc-activated microRNA cluster

Human adenocarcinomas commonly harbor mutations in the KRAS and MYC proto-oncogenes and the TP53 tumor suppressor gene. All three genetic lesions are potentially pro-angiogenic, as they sustain production of vascular endothelial growth factor (VEGF). Yet Kras-transformed mouse colonocytes lacking p53 formed indolent, poorly vascularized tumors, whereas additional transduction with a Myc-encoding retrovirus promoted vigorous vascularization and growth. In addition, VEGF levels were unaffected by Myc, but enhanced neovascularization correlated with downregulation of anti-angiogenic thrombospondin-1 (Tsp1) and related proteins, such as connective tissue growth factor (CTGF). Both Tsp1 and CTGF are predicted targets for repression by the miR-17-92 microRNA cluster, which was upregulated in colonocytes coexpressing K-Ras and c-Myc. Indeed, miR-17-92 knockdown with antisense 2′-O-methyl oligoribonucleotides partly restored Tsp1 and CTGF expression; in addition, transduction of Ras-only cells with a miR-17-92–encoding retrovirus reduced Tsp1 and CTGF levels. Notably, miR-17-92–transduced cells formed larger, better-perfused tumors. These findings establish a role for microRNAs in non–cell-autonomous Myc-induced tumor phenotypes.

Regulation of pancreatic |[beta]|-cell growth and survival by the serine/threonine protein kinase Akt1/PKB|[alpha]|

The physiological performance of an organ depends on an interplay between changes in cellular function and organ size, determined by cell growth, proliferation and death. Nowhere is this more evident than in the endocrine pancreas, where disturbances in function or mass result in severe disease. Recently, the insulin signal-transduction pathway has been implicated in both the regulation of hormone secretion from β cells in mammals as well as the determination of cell and organ size in Drosophila melanogaster. A prominent mediator of the actions of insulin and insulin-like growth factor 1 (IGF-1) is the 3′-phosphoinositide–dependent protein kinase Akt, also known as protein kinase B (PKB). Here we report that overexpression of active Akt1 in the mouse β cell substantially affects compartment size and function. There was a significant increase in both β-cell size and total islet mass, accompanied by improved glucose tolerance and complete resistance to experimental diabetes.

A Pilot Study of In Vivo Liver-Directed Gene Transfer with an Adenoviral Vector in Partial Ornithine Transcarbamylase Deficiency

Ornithine transcarbamylase deficiency (OTCD) is an inborn error of urea synthesis that has been considered as a model for liver-directed gene therapy. Current treatment has failed to avert a high mortality or morbidity from hyperammonemic coma. Restoration of enzyme activity in the liver should suffice to normalize metabolism. An E1- and E4-deleted vector based on adenovirus type 5 and containing human OTC cDNA was infused into the right hepatic artery in adults with partial OTCD. Six cohorts of three or four subjects received 1/2 log-increasing doses of vector from 2 x 10(9) to 6 x 10(11) particles/kg. This paper describes the experience in all but the last subject, who experienced lethal complications. Adverse effects included a flu-like episode and a transient rise in temperature, hepatic transaminases, thrombocytopenia, and hypophosphatemia. Humoral responses to the vector were seen in all research subjects and a proliferative cellular response to the vector developed in apparently naive subjects. In situ hybridization studies showed transgene expression in hepatocytes of 7 of 17 subjects. Three of 11 subjects with symptoms related to OTCD showed modest increases in urea cycle metabolic activity that were not statistically significant. The low levels of gene transfer detected in this trial suggest that at the doses tested, significant metabolic correction did not occur.

Pathology of Genetically Engineered Mouse Models of Pancreatic Exocrine Cancer: Consensus Report and Recommendations

Several diverse genetically engineered mouse models of pancreatic exocrine neoplasia have been developed. These mouse models have a spectrum of pathologic changes; however, until now, there has been no uniform nomenclature to characterize these changes. An international workshop, sponsored by The National Cancer Institute and the University of Pennsylvania, was held from December 1 to 3, 2004 with the goal of establishing an internationally accepted uniform nomenclature for the pathology of genetically engineered mouse models of pancreatic exocrine neoplasia. The pancreatic pathology in 12 existing mouse models of pancreatic neoplasia was reviewed at this workshop, and a standardized nomenclature with definitions and associated images was developed. It is our intention that this nomenclature will standardize the reporting of genetically engineered mouse models of pancreatic exocrine neoplasia, that it will facilitate comparisons between genetically engineered mouse models and human pancreatic disease, and that it will be broad enough to accommodate newly emerging mouse models of pancreatic neoplasia.

Quantitative assay for mutation in diploid human lymphoblasts using microtiter plates

We describe a microtiter plating technique which eliminates the need for soft agar and fibroblast feeder layers to determine the colony-forming ability of diploid human lymphoblast lines. The calculation of cloning efficiency is based on the Poisson distribution, and we present a statistical method for calculating confidence intervals. We have applied this technique to the comcomitant examination of induced mutation at the putative loci for hypoxanthine guanine phosphoribosyl transferase, thymidine, kinase, and Na+/K+ adenosine triphosphatase.

Liver transplantation for hepatocellular carcinoma validation of present selection criteria in predicting outcome

Appropriate patient selection is crucial in ensuring acceptable outcomes from orthotopic liver transplantation (OLT) for hepatocellular carcinoma (HCC). The United Network for Organ Sharing (UNOS) has elected to prioritize HCC patients for OLT based on criteria of tumor burden. However, it is unclear whether these criteria correlate with outcome, or with the pathobiological features associated with tumor recurrence. Therefore, we analyzed 109 consecutive patients undergoing OLT for HCC at our center, to determine the utility of present selection criteria in predicting outcome. Pathologic tumor staging of the explanted liver was based on the American Tumor Study Group modified tumor node metastases (pTNM) classification system. Multifocality was defined as >4 tumor nodules on explant. Survival analysis was performed using Kaplan‐Meier and Cox proportional hazards regression methods. At a median follow‐up of 18.9 months, the overall mortality was 19% with 15 patients (14%) dying of recurrent HCC. Kaplan‐Meier 1, 3 and 5‐year survival rates were 89.5%, 68%, and 65%, respectively. Recurrence‐free rates of 1, 3, and 5 years were 89%, 75%, and 65%, respectively. On univariate analysis, the factors found to be significantly associated with recurrence of HCC were explant features of macrovascular invasion, tumor size (per centimeter increase), pTNM stage (per 1‐stage increase), and pre‐transplant serum alphafetoprotein (AFP) >300 ng/mL. In defining a threshold level, we found that explant tumor diameter ≥3 cm, and those tumors classified as at least pT3 on pathological examination, were significantly associated with recurrence (P = .01 and .03, respectively). Tumor size on explant was found to be strongly correlated with multifocality (P = .017) and vascular invasion (P = .02). Patients exceeding pathological UNOS criteria were 3.1 times more likely to have recurrence of HCC (P = .03). In conclusion, we found that tumor size appears to be a surrogate marker for negative pathobiological predictors of outcome, i.e., vascular invasion and multifocality. Present UNOS selection criteria for HCC based on tumor burden appear to provide adequate discriminatory power in predicting outcome of OLT. (Liver Transpl 2004;10:911–918.)

Telomere Shortening Exposes Functions for the Mouse Werner and Bloom Syndrome Genes

ABSTRACT The Werner and Bloom syndromes are caused by loss-of-function mutations in WRN and BLM, respectively, which encode the RecQ family DNA helicases WRN and BLM, respectively. Persons with Werner syndrome displays premature aging of the skin, vasculature, reproductive system, and bone, and those with Bloom syndrome display more limited features of aging, including premature menopause; both syndromes involve genome instability and increased cancer. The proteins participate in recombinational repair of stalled replication forks or DNA breaks, but the precise functions of the proteins that prevent rapid aging are unknown. Accumulating evidence points to telomeres as targets of WRN and BLM, but the importance in vivo of the proteins in telomere biology has not been tested. We show that Wrn and Blm mutations each accentuate pathology in later-generation mice lacking the telomerase RNA template Terc, including acceleration of phenotypes characteristic of latest-generation Terc mutants. Furthermore, pathology not observed in Terc mutants but similar to that observed in Werner syndrome and Bloom syndrome, such as bone loss, was observed. The pathology was accompanied by enhanced telomere dysfunction, including end-to-end chromosome fusions and greater loss of telomere repeat DNA compared with Terc mutants. These findings indicate that telomere dysfunction may contribute to the pathogenesis of Werner syndrome and Bloom syndrome.

An open-label trial of the PPARγ ligand rosiglitazone for active ulcerative colitis

OBJECTIVES:Previous research has demonstrated that ligands for the γ subtype of peroxisome proliferator-activated receptors (PPARs) reduce inflammation in two different murine models of colitis. This study was designed to examine the potential efficacy of rosiglitazone, a ligand for the γ subtype of PPARs, as a therapy for active ulcerative colitis.METHODS:Fifteen patients with mild to moderately active ulcerative colitis despite therapy with 5-aminosalicylic acid compounds were enrolled in an open-label study of rosiglitazone (4 mg b.i.d. p.o.) for 12 wk. Thirteen of 15 patients were receiving concomitant therapy with corticosteroids and/or immunomodulator medications. Disease activity was measured with the Disease Activity Index.RESULTS:After 12 wk of therapy, four patients (27%) had achieved clinical remission, of whom three (20%) also had an endoscopic remission. Four additional patients (27%) had a clinical response without achieving remission. Two patients were hospitalized with worsened disease activity, and one patient was withdrawn for nephrotic syndrome.CONCLUSIONS:These data suggest that ligands for the γ subtype of PPARs may represent a novel therapy for ulcerative colitis. A double blind, placebo-controlled, randomized trial is warranted.

The Myc–miR-17∼92 Axis Blunts TGFβ Signaling and Production of Multiple TGFβ-Dependent Antiangiogenic Factors

c-Myc stimulates angiogenesis in tumors through mechanisms that remain incompletely understood. Recent work indicates that c-Myc upregulates the miR-17∼92 microRNA cluster and downregulates the angiogenesis inhibitor thrombospondin-1, along with other members of the thrombospondin type 1 repeat superfamily. Here, we show that downregulation of the thrombospondin type 1 repeat protein clusterin in cells overexpressing c-Myc and miR-17∼92 promotes angiogenesis and tumor growth. However, clusterin downregulation by miR-17∼92 is indirect. It occurs as a result of reduced transforming growth factor-β (TGFβ) signaling caused by targeting of several regulatory components in this signaling pathway. Specifically, miR-17-5p and miR-20 reduce the expression of the type II TGFβ receptor and miR-18 limits the expression of Smad4. Supporting these results, in human cancer cell lines, levels of the miR-17∼92 primary transcript MIR17HG negatively correlate with those of many TGFβ-induced genes that are not direct targets of miR-17∼92 (e.g., clusterin and angiopoietin-like 4). Furthermore, enforced expression of miR-17∼92 in MIR17HG(low) cell lines (e.g., glioblastoma) results in impaired gene activation by TGFβ. Together, our results define a pathway in which c-Myc activation of miR-17∼92 attenuates the TGFβ signaling pathway to shut down clusterin expression, thereby stimulating angiogenesis and tumor cell growth.