George Y. Wu

Delivery systems for gene therapy

Introduction of foreign genes into mammalian cellsin vitro has been accomplished previously by a variety of methods. The few techniques that have been developed for transfection of mammalian cellsin vivo, are technically difficult or lack cell specificity.We have developed a soluble, targetable DNA carrier system consisting of an asialoglycoprotein covalently coupled to a polycation. The strategy was based on: 1) the presence of unique receptors on hepatocytes which internalize galactose-terminal (asialo-)glycoproteins; 2) polycations can bind DNA in a non-covalent, non-damaging interaction. Using chloramphenicol acetyltransferase (CAT) as a marker gene, specific delivery and expression of CAT was demonstratedin vitro using asialoglycoprotein receptor ( +) and (-) cell lines.Intravenous injection of conjugate-DNA complexes in rats resulted in detection of CAT DNA sequences in liver 10 min later by dot blots with a CAT cDNA probe. CAT enzyme activity 24 hrs later was found specifically in liver but no other tissues or control livers. Targeted hepatic CAT expression was transient, maximal at 24 hrs but declined to barely detectable levels by 96 hrs. Persistent foreign gene expression was achieved by injection of DNA complex followed by 67% partial hepatectomy. High levels of hepatic CAT activity were detected through 11 weeks post-hepatectomy.The data indicate that a targetable gene delivery system can permitin vivo expression of an exogenous gene after simple intravenous injection. The foreign gene expression can be enhanced and made to persist by induction of hepatocyte replication.

Autoimmune hepatitis triggered by statins.

Although the cause of autoimmune hepatitis (AIH) is unknown, drugs are believed to be potential triggers in some patients. In isolated case reports, statins have been considered such triggers. Here we describe 3 patients in whom it is probable that statins initiated the development of AIH. Two men (aged 47 and 51) and one woman (aged 57) developed AIH after the initiation of statin therapy. They developed positive titers of antinuclear antibodies, antismooth muscle antibodies (1/40 to 1/160), and hypergammaglobulinemia. Features of all 3 patients met the criteria for AIH according to the International Autoimmune Hepatitis Panel. Liver biopsies in all 3 showed varying stages of fibrosis and plasma cell infiltration, compatible with AIH. The woman developed hepatitis due to statins on 2 separate occasions: the first in 1999, due to simvastatin, and the second in 2001 to 2002, due to atorvastatin, which was severe and persisted even after discontinuing medication. Similarly, in the 2 other cases, exposure to statins preceded development of AIH, which persisted despite discontinuing medications. All 3 patients responded well to prednisone and azathioprine or mycophenolate therapy. 3 similar previously reported cases are reviewed. We conclude that the 3 cases reported here and 3 similar previously reported cases, indicate that severe, ongoing AIH on rare occasions can be triggered by statins.

Risk factors for sessile serrated adenomas.

Background Although sessile serrated adenomas (SSAs) may represent a separate and important pathway for colorectal cancer (CRC), little is known about the risk factors for these lesions. Molecular abnormalities such as BRAF have been observed in SSA and smokers. Our hypothesis is that smoking may be associated with these lesions. Methods All patients diagnosed with an SSA from January 2007 to September 2010 were identified retrospectively based on a pathology database query. There were 2 sets of controls. One group had no adenomas, whereas another group had tubular adenomas. These groups were randomly identified from 2007 to 2010. Data collected included age, sex, ethnicity, height, weight, family history of CRC, diabetes mellitus, use of aspirin, statins, and calcium, and serum trigylcerides and cholesterol. We defined smokers as those patients who smoked at least 20 pack-years. Results We identified 90 patients with an SSA of any size, 90 patients with tubular adenomas, and 200 controls with no adenomas. Of the 90 SSAs, 42 were 6 mm or larger and 19 of them were ≥1 cm. Most of the SSAs was flat (76/90; 84.4%). After multivariate analyses, smokers with at least 20 pack-year exposure were found to have an increased risk [adjusted odds ratio (OR)=7.31; 95% confidence interval (CI), 3.92-13.63] of having any SSAs, SSAs ≥6 mm (adjusted OR=7.77; 95% CI, 3.48-17.35), and large SSAs (adjusted OR=10.20; 95% CI, 3.31-31.41) compared with nonsmokers. We also observed this relationship when comparing patients with SSAs to those with tubular adenomas. Conclusions Our data suggest that smoking at least 20 pack-years is strongly associated with any and large SSAs. In addition, diabetes mellitus and obesity seem to be associated with SSAs as well. Our data has implications for CRC screening.

Hepatocellular Carcinoma: Update on Diagnosis and Treatment

In this review, the current approach to the screening, diagnostic evaluation, staging, and treatment for hepatocellular carcinoma (HCC) is outlined. The serum alpha-fetoprotein (AFP) level and abdominal ultrasonography (US) remain the cornerstones of screening protocols for HCC. Other serum marker proteins, such as abnormal serum prothrombin (PIVKA-II), when used in conjunction with AFP, can increase the yield for HCC. For diagnosis and staging of HCC, other imaging modalities employed include CT scan, infusion hepatic angiography, CT with arterial portography or iodized oil enhancement, MRI with contrast enhancement, intraoperative US, and US-guided fine-needle aspiration cytology and biopsy. Treatment options which have afforded some improvement in survival and tumor regression include surgical resection, orthotopic liver transplantation, percutaneous injection of ethanol, arterial chemoembolization, cryotherapy, and systemic or regional chemotherapy. Despite these advances, the diagnosis of HCC still portends a dismal prognosis.

Receptor-mediated delivery of foreign genes to hepatocytes

Naturally existing cell surface receptors provide convenient systems for transporting substances from the extracellular environment to the interior of cells. When such receptors are highly selective for certain cell types, the possibility exists for targeting biological agents of interest to specific tissues. In this review, the concepts, progress and problems in targeting genes and their subsequent expression in hepatocytes based on the asialoglycoprotein receptor in vitro and in vivo will be discussed. The use of protein carriers for hepatocyte specific delivery of double stranded DNA to introduce novel gene expression novel, as well as, delivery of single stranded DNA for inhibition of endogenous genes with examples of each are reviewed.

An engineered multidomain bactericidal peptide as a model for targeted antibiotics against specific bacteria

We constructed a peptide consisting of a staphylococcal AgrD1 pheromone fused to the channel-forming domain of colicin Ia and named it pheromonicin. This fusion peptide had bactericidal effects against methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA, respectively), but not against Staphylococcus epidermidis or Streptococcus pneumoniae. Growth rates, vital staining and colony forming unit (CFU) counts showed that pheromonicin did not merely suppress growth but killed S. aureus cells. The specificity of pheromonicin was shown by the absence of bactericidal effects against an accessory gene regulator (agr) locus knockout of S. aureus, and a dose-dependent inhibition of the bactericidal effects of pheromonicin by competition with corresponding free AgrD pheromone. In vivo, all pheromonicin-treated mice survived administration of MRSA that was lethal to controls. No toxicity was detectable in human liver or renal cells in culture, or in livers, kidneys or spleens of pheromonicin-treated mice. The results suggest that these types of chimeric peptides may be of value as antibiotics against specific bacterial infections.

Gene therapy: Applications to the treatment of gastrointestinal and liver diseases

There has been much progress in our understanding of molecular mechanisms in the pathogenesis of inherited metabolic disorders. In addition, powerful new molecular techniques have made possible phenotypic alterations by delivery of foreign genes to target cells. As a result, concepts and methods that would have been considered purely science fiction 10 years ago can now be found in human clinical trials engaged in the treatment of these disorders. In this review, we have attempted to provide an introduction and survey of the topic of gene therapy, with specific examples of laboratory and clinical achievements to date, and highlights on potentials for applications in digestive diseases.

Secondary Structure and Hybridization Accessibility of Hepatitis C Virus 3′-Terminal Sequences

ABSTRACT The 3′-terminal sequences of hepatitis C virus (HCV) positive- and negative-strand RNAs contribute cis-acting functions essential for viral replication. The secondary structure and protein-binding properties of these highly conserved regions are of interest not only for the further elucidation of HCV molecular biology, but also for the design of antisense therapeutic constructs. The RNA structure of the positive-strand 3′ untranslated region has been shown previously to influence binding by various host and viral proteins and is thus thought to promote HCV RNA synthesis and genome stability. Recent studies have attributed analogous functions to the negative-strand 3′ terminus. We evaluated the HCV negative-strand secondary structure by enzymatic probing with single-strand-specific RNases and thermodynamic modeling of RNA folding. The accessibility of both 3′-terminal sequences to hybridization by antisense constructs was evaluated by RNase H cleavage mapping in the presence of combinatorial oligodeoxynucleotide libraries. The mapping results facilitated identification of antisense oligodeoxynucleotides and a 10-23 deoxyribozyme active against the positive-strand 3′-X region RNA in vitro.

Targeting of genes to the liver with glycoprotein carriers

Abstract Several techniques are available to deliver foreign genes to cells in vitro. These techniques have offered valuable insights into gene regulation and expression. Many of these methods, however, have limited in vivo potential for clinical gene therapy because they compromise cell viability or cannot be targeted to desired cell types. Strategies with high potential for use in gene therapy need to satisfy several criteria: (1) use of a stable vector for the foreign DNA, (2) efficient expression of foreign DNA in host cells, and (3) a means to target a desired cell type or organ. Hepatocytes are attractive targets for gene therapy because of their large number, rich blood supply and important role in intermediary metabolism. Hepatocytes have also been found to have specific cell surface receptors that can be utilized for targeted delivery of foreign DNA. This article discusses in vitro and in vivo methods of targeted delivery and expression of foreign genes in hepatocytes with emphasis on those techniques with potential for clinical gene therapy. Methods to enhance and prolong foreign gene expression such as the use of the lysosomotropic agent chloroquine, endosomal disruption by adenovirus and influenza virus hemagglutinin HA-2 subunit, and partial hepatectomy, which has been found to augment foreign gene expression, are covered. Finally, the use of ligand-based systems to target sense and antisense DNA in gene therapy to correct metabolic disorders and the targeted delivery of protective agents to the liver are addressed.

Nonalcoholic fatty liver disease and low-carbohydrate diets.

Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance, obesity, and other features of metabolic syndrome and is known to be the most common cause for abnormal liver enzymes. The recent surge in the number of patients with NAFLD has been accompanied by an increase in research on potential treatment options, particularly weight loss and dietary interventions. Given the growing interest on the role of carbohydrates in the prevention and treatment of NAFLD, this review discusses the relationship between the amount of carbohydrates in the diet and effects on NAFLD, with special emphasis on a low-carbohydrate diet. We discuss the role of insulin resistance in the pathophysiology of NAFLD and provide an overview of various popular diets and their role as a treatment option for NAFLD. Additional large, longer-duration trials studying the efficacy of a low-carbohydrate diet in the treatment and prevention of NAFLD are eagerly awaited.