Optimization of Thymidine Kinase-Based Safety Switch for Neural Cell Therapy.

Cell therapies based on pluripotent stem cells (PSC), have opened new therapeutic strategies for neurodegenerative diseases. However, insufficiently differentiated PSC can lead to tumor formation. Ideally, safety switch therapies should selectively kill proliferative transplant cells while preserving post-mitotic neurons.

Hypoxia theranostics of a human prostate cancer xenograft and the resulting effects on the tumor microenvironment.

Hypoxia is frequently observed in human prostate cancer, and is associated with chemoresistance, radioresistance, metastasis, and castrate-resistance. Our purpose in these studies was to perform hypoxia theranostics by combining in vivo hypoxia imaging and hypoxic cancer cell targeting in a human prostate cancer xenograft. This was achieved by engineering PC3 human prostate cancer cells to express luciferase as well as a prodrug enzyme, yeast cytosine deaminase, under control of hypoxic response elements (HREs).

Issues facing employability assessment in total and permanent disability insurance claims: A rehabilitation perspective.

Background: Expert employment information helps life insurers to decide total and permanent disability claims. The employability assessment model was developed a decade ago by rehabilitation counselors and has not been critically examined.

Objective: This exploratory descriptive study aims to elicit key issues of employability assessment within Australian life insurance.

Delayed Progression of Lung Metastases Following Delivery of a Prodrug-activating Enzyme.

Background: Chemotherapy is an effective option to treat recurrent or metastatic cancer but its debilitating side-effects limit the dose and time of exposure. Prodrugs that can be activated locally by an activating enzyme can minimize collateral damage from chemotherapy. We previously demonstrated the efficacy of a poly-L-lysine-based theranostic nanoplex containing bacterial cytosine deaminase (bCD) that locally converted 5-fluorocytosine (5-FC) to the chemotherapeutic agent 5-fluorouracil in MDA-MB-231 primary tumor xenografts.

Creation of zebularine-resistant human cytidine deaminase mutants to enhance the chemoprotection of hematopoietic stem cells.

Human cytidine deaminase (hCDA) is a biomedically important enzyme able to inactivate cytidine nucleoside analogs such as the antileukemic agent cytosine arabinoside (AraC) and thereby limit antineoplastic efficacy. Potent inhibitors of hCDA have been developed, e.g.

Evaluation of a UCMK/dCK fusion enzyme for gemcitabine-mediated cytotoxicity.

While gemcitabine (2'-2'-difluoro-2'-deoxycytidine, dFdC) displays wide-ranging antineoplastic activity as a single agent, variable response rates and poor intracellular metabolism often limit its clinical efficacy. In an effort to enhance dFdC cytotoxicity and help normalize response rates, we created a bifunctional fusion enzyme that combines the enzymatic activities of deoxycytidine kinase (dCK) and uridine/cytidine monophosphate kinase (UCMK) in a single polypeptide. Our goal was to evaluate whether the created fusion could induce beneficial, functional changes toward dFdC, expedite dFdC conversion to its active antimetabolites and consequently amplify cell dFdC sensitivity.

Development and validation of a rapid and sensitive HPLC method for the quantification of 5-fluorocytosine and its metabolites.

To study the intracellular metabolism of the prodrug 5-fluorocytosine (5FC), we developed a novel reverse-phase high-performance liquid chromatography method to simultaneously detect 5FC and its four major anabolic metabolites: 5-fluorouracil, 5-fluorouridine, 5-fluorouridine-monophosphate and 5-fluoro-2'deoxyuridine-5'-monophosphate. Separation of each compound was accomplished under isocratic conditions using a C(18) column and mobile phase of formic acid-water (1 : 99 v/v). The method was validated for both accuracy and reproducibility in cell culture media.

Bacterial cytosine deaminase mutants created by molecular engineering show improved 5-fluorocytosine-mediated cell killing in vitro and in vivo.

Cytosine deaminase is used in combination with 5-fluorocytosine as an enzyme-prodrug combination for targeted genetic cancer treatment. This approach is limited by inefficient gene delivery and poor prodrug conversion activities. Previously, we reported individual point mutations within the substrate binding pocket of bacterial cytosine deaminase (bCD) that result in marginal improvements in the ability to sensitize cells to 5-fluorocytosine (5FC).

Titration of variant HSV1-tk gene expression to determine the sensitivity of 18F-FHBG PET imaging in a prostate tumor.

Unlabelled: Because of its high selectivity and specificity for the imaging reporter probe 9-(4-(18)F-fluoro-3-[hydroxymethyl]butyl)guanine ((18)F-FHBG), the herpes simplex virus type 1 thymidine kinase (HSV1-tk) variant sr39tk is actively being studied as a PET reporter gene. We recently demonstrated the capability of using a prostate-specific transcriptional amplification PET reporter vector, AdTSTA-sr39tk, to target prostate cancer lymph node metastasis. However, one area that warrants further study is the examination of the sensitivity of PET by determining the minimum percentage of cells expressing the sr39tk transgene needed for detection.

Mutations at serine 37 in mouse guanylate kinase confer resistance to 6-thioguanine.

Guanylate kinase (GMK) is an essential nucleoside monophosphate kinase that catalyzes the phosphorylation of guanine-monophosphate (GMP) and dGMP to yield GDP and dGDP, respectively, important precursors for nucleotide synthesis. GMK is also responsible for the activation of 6-thioguanine (6-TG), a drug widely used as chemotherapeutic agent to treat leukemia. Several mechanisms of resistance to 6-TG have been reported but a subset of drug resistant cells cannot be explained by these mechanisms.

Molecular chemotherapy of pancreatic cancer using novel mutant bacterial cytosine deaminase gene.

The combination of molecular chemotherapy with radiation therapy has the potential to become a powerful approach for treatment of pancreatic cancer. We have developed an adenoviral vector (AdbCD-D314A) encoding a mutant bacterial cytosine deaminase (bCD) gene, which converts the prodrug 5-fluorocytosine (5-FC) into the active drug 5-fluorouracil. The aim of this study was to investigate AdbCD-D314A/5-FC-mediated cytotoxicity in vitro and therapeutic efficacy in vivo alone and in combination with radiation against human pancreatic cancer cells and xenografts.

Development of an instrument to assess individual student performance in small group tutorials.

Recognizing the need for a valid and reliable method to assess individual tutorial performance in a problem-based learning curriculum, we developed a 31-item instrument from theoretical frameworks and items used elsewhere. A scale was developed for each of three broad learning domains: self-directed learning (SDL), critical thinking (CT), and group process (GP). The instrument demonstrated high internal consistency (SDL = .

Seeking to understand telephone support for dementia caregivers.

Caregivers of persons with dementia encounter particular challenges in their roles and often experience unmet needs for information and emotional support. This article describes a qualitative descriptive study designed to explore the intervention of telephone support for such caregivers. Data were collected from both caregivers and telephone support providers.

Computational thermostabilization of an enzyme.

Thermostabilizing an enzyme while maintaining its activity for industrial or biomedical applications can be difficult with traditional selection methods. We describe a rapid computational approach that identified three mutations within a model enzyme that produced a 10 degrees C increase in apparent melting temperature T(m) and a 30-fold increase in half-life at 50 degrees C, with no reduction in catalytic efficiency. The effects of the mutations were synergistic, giving an increase in excess of the sum of their individual effects.

A novel Escherichia coli strain allows functional analysis of guanylate kinase drug resistance and sensitivity.

Guanylate kinase is a critical enzyme in the biosynthesis of guanosine 5'-triphosphate (GTP) and dGTP and is responsible for the phosphorylation of guanosine 5'-monophosphate (GMP) and dGMP to guanosine 5'-diphosphate (GDP) and dGDP, respectively. As with many nucleotide-metabolizing enzymes, guanylate kinase is involved in antimicrobial and antineoplastic drug activation. This is due to the structural similarities of such agents with nucleobases or nucleosides that are acted upon by endogenous enzymes.