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Enzyme Prodrug Therapy (enzyme + prodrug_therapy)
Selected AbstractsTherapy with Cell Encapsulation for Substitution of Organ Function and Tumor Treatment,ADVANCED ENGINEERING MATERIALS, Issue 8 2009J. Matthias Löhr Cell encapsulation represents an innovative technique. However, clinical applications are sparse. Most experiments and clinical studies have been performed with either alginate or cellulose sulfate capsules, containing several cell lines and a broad variety of applications, ranging all the way from substitution for impaired organ function and release of cytokines or growth factors to gene-directed enzyme prodrug therapy. A few clinical studies have been conducted and/or are under way. [source] Developing bifunctional , -lactamase molecules with built-in target-recognizing module for prodrug therapy: identification of Enterobacter Cloacae P99 cephalosporinase loops suitable for randomization and phage-display selectionJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2009Girja S. Shukla Abstract This study was focused on developing catalytically active , -lactamase enzyme molecules that have target-recognizing sites built within their scaffold. Using phage-display approach, nine libraries were constructed by inserting the randomized linear or cysteine-constrained heptapeptides in the five different loops on the outer surface of P99 , -lactamase molecule. The pIII signal peptide of Sec-pathway was employed for a periplasmic translocation of the , -lactamase fusion protein, which we found more efficient than the DsbA signal peptide of SRP-pathway. The randomized heptapeptide loops replaced native amino acids between positions 34Y- 37K, 238M- 246A, 275N- 280A, 305A- 311S, or 329I- 334I of the P99 , -lactamase molecules for generating the loop-1 to -5 libraries, respectively. The diversity of each loop library was judged by counting the primary and , -lactamase-active clones. The linear peptide inserts in the loop-2 library showed the maximum number of the , -lactamase-active clones, followed by the loop-5, loop-3, and loop-4. The insertion of the cysteine-constrained loops exhibited a dramatic loss of the enzyme-active , -lactamase clones. The complexity of the loop-2 linear library, as determined by the frequency and diversity of amino acid distributions in the randomized region, appears consistent with the standards of other types of phage display library systems. The selection of the loop-2 linear library on streptavidin protein as a test target identified several , -lactamase clones that specifically bound to streptavidin. In conclusion, this study identified the suitability of the loop-2 of P99 , -lactamase for constructing a phage-display library of the , -lactamase enzyme-active molecules that can be selected against a target. This is an enabling step in our long-term goal of developing bifunctional , -lactamase molecules against cancer-specific targets for enzyme prodrug therapy of cancer. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hyperpolarized 13C magnetic resonance detection of carboxypeptidase G2 activityMAGNETIC RESONANCE IN MEDICINE, Issue 5 2009Yann Jamin Abstract Carboxypeptidase G2 (CPG2) is a bacterial enzyme that is currently employed in a range of targeted cancer chemotherapy strategies such as gene-directed enzyme prodrug therapy (GDEPT). Employing dynamic nuclear polarization (DNP) and natural abundance 13C magnetic resonance spectroscopy (MRS), we observed the CPG2-mediated conversion of a novel hyperpolarized reporter probe 3,5-difluorobenzoyl-L-glutamic acid (3,5-DFBGlu) to 3,5-difluorobenzoic acid (3,5-DFBA) and L-glutamic acid (L-Glu) in vitro. Isotopic labeling of the relevant nuclei with 13C in 3,5-DFBGlu or related substrates will yield a further factor of 100 increase in the signal-to-noise. We discuss the feasibility of translating these experiments to generate metabolic images of CPG2 activity in vivo. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] A novel technique to monitor carboxypeptidase G2 expression in suicide gene therapy using 19F magnetic resonance spectroscopyNMR IN BIOMEDICINE, Issue 5 2009Laura Mancini Abstract Development and evaluation of new anticancer drugs are expedited when minimally invasive biomarkers of pharmacokinetic and pharmacodynamic behaviour are available. Gene-directed enzyme prodrug therapy (GDEPT) is a suicide gene therapy in which the anticancer drug is activated in the tumor by an exogenous enzyme previously targeted by a vector carrying the gene. GDEPT has been evaluated in various clinical trials using several enzyme/prodrug combinations. The key processes to be monitored in GDEPT are gene delivery and expression, as well as prodrug delivery and activation. {4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoyl}-L-glutamic acid, a prodrug for the GDEPT enzyme carboxypeptidase-G2 (CPG2; Km,=,1.71,µM; kcat,=,732,s,1), was measured with 19F magnetic resonance spectroscopy (MRS). The 1,ppm chemical shift separation found between the signals of prodrug and activated drug (4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoic acid) is sufficient for the detection of prodrug activation in vivo. However, these compounds hydrolyze rapidly, and protein binding broadens the MR signals. A new CPG2 substrate was designed with hydroxyethyl instead of chloroethyl groups (Km,=,3.5,µM, kcat,=,747,s,1). This substrate is nontoxic and stable in solution, has a narrow MRS resonance in the presence of bovine and foetal bovine albumin, and exhibits a 1.1,ppm change in chemical shift upon cleavage by CPG2. In cells transfected to express CPG2 in the cytoplasm (MDA MB 361 breast carcinoma cells and WiDr colon cancer cells), well-resolved 19F MRS signals were observed from clinically relevant concentrations of the new substrate and its nontoxic product. The MRS conversion half-life (470,min) agreed with that measured by HPLC (500,min). This substrate is, therefore, suitable for evaluating gene delivery and expression prior to administration of the therapeutic agent. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of the prodrugs 5-fluorocytosine and CPT-11 on ovarian cancer cells using genetically engineered stem cells: tumor-tropic potential and inhibition of ovarian cancer cell growthCANCER SCIENCE, Issue 4 2010Ki-Yon Kim Recent studies have shown that genetically engineered stem cells (GESTECs) to produce suicide enzymes that convert non-toxic prodrugs to toxic metabolites selectively migrate toward tumor sites and reduce tumor growth. In the present study, we evaluated whether these GESTECs were capable of migrating to human ovarian cancer cells and examined the potential therapeutic efficacy of the gene-directed enzyme prodrug therapy against ovarian cancer cells in vitro. The expression of cytosine deaminase (CD) or carboxyl esterase (CE) mRNA of GESTECs was confirmed by RT-PCR. A modified transwell migration assay was performed to determine the migratory capacity of GESTECs to ovarian cancer cells. GESTECs (HB1.F3.CD or HB1.F3.CE cells) engineered to express a suicide gene (CD or CE) selectively migrated toward ovarian cancer cells. A [3H] thymidine incorporation assay was conducted to measure the proliferative index. Treatment of human epithelial ovarian cancer cell line (SKOV-3, an ovarian adenocarcinoma derived from the ascites of an ovarian cancer patient) with the prodrugs 5-fluorocytosine (5-FC) or camptothecin-11 (CPT-11) in the presence of HB1.F3.CD or HB1.F3.CE cells resulted in the inhibition of ovarian cancer cell growth. Based on the data presented herein, we suggest that GESTECs expressing CD/CE may have a potent advantage to selectively treat ovarian cancers. (Cancer Sci 2010; 101: 955,962) [source] Selective Treatment of Cancer: Synthesis, Biological Evaluation and Structural Elucidation of Novel Analogues of the Antibiotic CC-1065 and the DuocarmycinsCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Abstract Novel diastereomerically pure ,- D -galactosidic prodrugs (+)- 12,a,e of the cytotoxic antibiotics CC-1065 and the duocarmycins were prepared for an antibody directed enzyme prodrug therapy (ADEPT) using 4 as a substrate via a radical cyclization to give rac - 5 and rac - 6 followed by a chromatographic resolution of the enantiomers of rac - 5, glycosidation and linkage to the DNA-binding units 10,a,e. These only slightly toxic compounds can be toxified enzymatically by an antibody,,- D -galactosidase conjugate at the surface of malignant cells to give the cytotoxic drugs, which then alkylate DNA. The new prodrugs were tested in in vitro cytotoxicity assays showing excellent QIC50 values of 4800 and 4300 for (+)- 12,a and (+)- 12,b, respectively. The absolute configuration of precursor (+)- 5 was determined by comparison of the experimental CD spectrum with the theoretically predicted CD spectra and by X-ray structure analysis. [source] Prodrug Strategies in Anticancer ChemotherapyCHEMMEDCHEM, Issue 1 2008Felix Kratz Dr. Abstract The majority of clinically approved anticancer drugs are characterized by a narrow therapeutic window that results mainly from a high systemic toxicity of the drugs in combination with an evident lack of tumor selectivity. Besides the development of suitable galenic formulations such as liposomes or micelles, several promising prodrug approaches have been followed in the last decades with the aim of improving chemotherapy. In this review we elucidate the two main concepts that underlie the design of most anticancer prodrugs: drug targeting and controlled release of the drug at the tumor site. Consequently, active and passive targeting using tumor-specific ligands or macromolecular carriers are discussed as well as release strategies that are based on tumor-specific characteristics such as low pH or the expression of tumor-associated enzymes. Furthermore, other strategies such as ADEPT (antibody-directed enzyme prodrug therapy) and the design of self-eliminating structures are introduced. Chemical realization of prodrug approaches is illustrated by drug candidates that have or may have clinical importance. [source] | |||||||||||||