The Oncopathic Potency of Clostridium perfringens Is Independent of Its α-Toxin Gene

Hypoxia in solid tumors is a major obstacle in conventional treatment because of inefficient delivery of therapeutic agents to the lesions, but offers the potential for anaerobic bacterial colonization that can lead to tumor destruction. We have previously reported a recombinant Clostridium perfringens (Cp) strain constructed by deletion of the superoxide dismutase (sod) gene and insertion of the Panton–Valentine leukocidin (PVL) gene, Cp/sod−/PVL, which showed elevated oxygen sensitivity, tumor selectivity, and oncopathic potency in an orthotopic model of pancreatic cancer in immune-competent and syngeneic mice, and that led to substantial prolongation of animal survival. A major limitation to Cp/sod−/PVL in clinical applications is that it expresses phospholipase C (plc), the α-toxin and the major virulence determinant in Cp that is causative in the development of gas gangrene. In this study, the plc gene in Cp/sod−/PVL was knocked out to create Cp/plc−/sod−/PVL, which was shown to be incapable of inducing gas gangrene in mice. Intravenous injection of Cp/plc−/sod−/PVL spores led to a significant survival advantage in tumor-bearing mice with the same efficacy as Cp/sod−/PVL, indicating that the oncopathic potency of Cp is independent of a functional plc gene. The treatment also did not lead to an attenuated immune response to a subsequent pathogen challenge, indicating that a systemic immune-suppressive effect in the host is absent. Consequently, Cp/plc−/sod−/PVL is a novel oncopathic bacterial agent for the effective treatment of pancreatic cancer and other poorly vascularized tumors, with a substantially enhanced safety profile, which is essential for the development of translational studies in the future

Phenylketonuria in Costa Rica: preliminary spectrum of PAH mutations and their associations with highly polymorphic haplotypes

Artículo científico -- Universidad de Costa Rica, Instituto de Investigaciones en Salud. 1996. Este artículo es privado debido a limitaciones de derechos de autor.A preliminary evaluation of the molecular basis of phenylketonuria (PKU) in Costa Rica was made by performing mutational analyses in the six PKU families identified to date. These studies revealed the presence of the previously reported European mutations IVS ntS, L48S, E221G and IVS12M1 as well as the novel mutation IVS7nt3. The combined use of the STR, VNTR and Xmol polymorphic systems for the PAH gene resulted in a discriminant distribution of haplotypes among normal and mutant chromosomes and suggests its potential usefulness for future diagnostic applications in Costa Rican PKU kindreds. This is the first report of a genetic analysis in a Central American PKU population.Baylor College of Medicine, HoustonInstitute of Human and Molecular GeneticsUniversidad de Costa Rica, Instituto de Investigaciones en SaludUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones en Salud (INISA

Development of a Transgenic Mouse System for the Analysis of Stages in Liver Carcinogenesis Using Tissue-specific Expression of SV40 Large T-Antigen Controlled by Regulatory Elements of the Human α-1-Antitrypsin Gene

α-1-Antitrypsin (AAT) is the major antiprotease in human plasma; it is synthesized primarily in hepatocytes and to a lesser extent in several nonhepatic tissues. Under the control of regulatory elements of the human AA T gene, expression of SV40 large tumor antigen (T-ag) in transgenic mice occurred in the liver, stomach, pancreas, and kidney. Among seven founder transgenic animals, six developed liver carcinoma, four showed gastric neoplasia, and one developed pancreatic carcinoma. In three animals the kidneys showed glomerular or tubular epithelial hyperplasia but no malignancy. A stable transgenic line, 1812, was established. Members of this line reproducibly develop liver tumors by 10 weeks of age but do not exhibit any phenotypic changes in other tissues. Histological changes leading to liver tumor formation occurred with predictable kinetics and could be classified into four distinct stages: (a) embryonal/ fetal stage, no recognizable histological changes; (b) newborn to 2 weeks of age, hyperplastic hepatocytes with reduced amounts of cytoplasm but no nuclear alterations; (c) between 3 and 8 weeks of age, diffuse liver cell dysplasia without observable tumor nodules; and (d) 8 weeks of age and thereafter, hepatocellular carcinomas in a background of liver dysplasia. Embryonic and newborn liver tissue showed uniform, high level expression of T-ag in the majority of hepatocytes by immunohistochemistry, whereas the dysplastic and tumoral stages were characterized by considerable variation in both the intensity of T-ag staining and the proportion of T-ag-positive cells. Immunoprecipitation analyses showed that T-ag was complexed with cellular protein p53 in all tumor samples. This study showed that SV40 T-ag expression in the liver resulted in cellular hyperplasia and dysplasia; additional event(s) apparently were required for progression to neoplasia. Those cooperating events occurred with predictable kinetics. This transgenic mouse system displays several similarities with human liver disease and provides a practical model for the study of separate steps in hepatocarcinogenesis. © 1989, American Association for Cancer Research. All rights reserved

Mechanism of Sustained Release of Vascular Endothelial Growth Factor in Accelerating Experimental Diabetic Healing

In this study, we hypothesize that local sustained release of vascular endothelial growth factor (VEGF), using adenovirus vector (ADV)-mediated gene transfer, accelerates experimental wound healing. This hypothesis was tested by determining the specific effects of VEGF165 application on multiple aspects of the wound healing process, that is, time to complete wound closure and skin biomechanical properties. After showing accelerated wound healing in vivo, we studied the mechanism to explain the findings on multiple aspects of the wound healing cascade, including epithelialization, collagen deposition, and cell migration. Intradermal treatment of wounds in non-obese diabetic and db/db mice with ADV/VEGF165 improves healing by enhancing tensile stiffness and/or increasing epithelialization and collagen deposition, as well as by decreasing time to wound closure. VEGF165, in vitro, stimulates the migration of cultured human keratinocytes and fibroblasts, thus revealing a non-angiogenic effect of VEGF on wound closure. In conclusion, ADV/VEGF is effective in accelerating wound closure by stimulating angiogenesis, epithelialization, and collagen deposition. In the future, local administration and sustained, controlled release of VEGF165 may decrease amputations in patients with diabetic foot ulcers and possibly accelerate closure of venous ulcers and pressure ulcers. JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://network.nature.com/group/jidclu