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Title: Cytosine Deaminase/5-Fluorocytosine Exposure Induces Bystander and Radiosensitization Effects in Hypoxic Glioblastoma Cells in vitro

Abstract

Purpose: Treatment of glioblastoma (GBM) is limited by therapeutic ratio; therefore, successful therapy must be specifically cytotoxic to cancer cells. Hypoxic cells are ubiquitous in GBM, and resistant to radiation and chemotherapy, and, thus, are logical targets for gene therapy. In this study, we investigated whether cytosine deaminase (CD)/5-fluorocytosine (5-FC) enzyme/prodrug treatment induced a bystander effect (BE) and/or radiosensitization in hypoxic GBM cells. Methods and Materials: We stably transfected cells with a gene construct consisting of the SV40 minimal promoter, nine copies of a hypoxia-responsive element, and the yeast CD gene. During hypoxia, a hypoxia-responsive element regulates expression of the CD gene and facilitates the conversion of 5-FC to 5-fluorouracil, a highly toxic antimetabolite. We used colony-forming efficiency (CFE) and immunofluorescence assays to assess for BE in co-cultures of CD-expressing clone cells and parent, pNeo- or green fluorescent protein-stably transfected GBM cells. We also investigated the radiosensitivity of CD clone cells treated with 5-FC under hypoxic conditions, and we used flow cytometry to investigate treatment-induced cell cycle changes. Results: Both a large BE and radiosensitization occurred in GBM cells under hypoxic conditions. The magnitude of the BE depended on the number of transfected cells producing CD, the functionality of themore » CD, the administered concentration of 5-FC, and the sensitivity of cell type to 5-fluorouracil. Conclusion: Hypoxia-inducible CD/5-FC therapy in combination with radiation therapy shows both a pronounced BE and a radiosensitizing effect under hypoxic conditions.« less

Authors:
 [1];  [1];  [1];  [1];  [2]
  1. Brain Tumor Research Center of the Department of Neurological Surgery, University of California-San Francisco, San Francisco, CA (United States)
  2. Brain Tumor Research Center of the Department of Neurological Surgery, University of California-San Francisco, San Francisco, CA (United States). E-mail: dennisdeen@juno.com
Publication Date:
OSTI Identifier:
20951602
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 67; Journal Issue: 5; Other Information: DOI: 10.1016/j.ijrobp.2006.12.020; PII: S0360-3016(06)03659-5; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ANOXIA; BIOLOGICAL RADIATION EFFECTS; CELL CYCLE; CHEMOTHERAPY; CLONE CELLS; CYTOSINE; ENZYMES; GENE THERAPY; GENES; GLIOMAS; IN VITRO; RADIOSENSITIVITY; RADIOTHERAPY; TOXICITY; URACILS; YEASTS

Citation Formats

Chen, Jennifer K., Hu, Lily J., Wang Dongfang, Lamborn, Kathleen R., and Deen, Dennis F. Cytosine Deaminase/5-Fluorocytosine Exposure Induces Bystander and Radiosensitization Effects in Hypoxic Glioblastoma Cells in vitro. United States: N. p., 2007. Web. doi:10.1016/j.ijrobp.2006.12.020.
Chen, Jennifer K., Hu, Lily J., Wang Dongfang, Lamborn, Kathleen R., & Deen, Dennis F. Cytosine Deaminase/5-Fluorocytosine Exposure Induces Bystander and Radiosensitization Effects in Hypoxic Glioblastoma Cells in vitro. United States. doi:10.1016/j.ijrobp.2006.12.020.
Chen, Jennifer K., Hu, Lily J., Wang Dongfang, Lamborn, Kathleen R., and Deen, Dennis F. Sun . "Cytosine Deaminase/5-Fluorocytosine Exposure Induces Bystander and Radiosensitization Effects in Hypoxic Glioblastoma Cells in vitro". United States. doi:10.1016/j.ijrobp.2006.12.020.
@article{osti_20951602,
title = {Cytosine Deaminase/5-Fluorocytosine Exposure Induces Bystander and Radiosensitization Effects in Hypoxic Glioblastoma Cells in vitro},
author = {Chen, Jennifer K. and Hu, Lily J. and Wang Dongfang and Lamborn, Kathleen R. and Deen, Dennis F.},
abstractNote = {Purpose: Treatment of glioblastoma (GBM) is limited by therapeutic ratio; therefore, successful therapy must be specifically cytotoxic to cancer cells. Hypoxic cells are ubiquitous in GBM, and resistant to radiation and chemotherapy, and, thus, are logical targets for gene therapy. In this study, we investigated whether cytosine deaminase (CD)/5-fluorocytosine (5-FC) enzyme/prodrug treatment induced a bystander effect (BE) and/or radiosensitization in hypoxic GBM cells. Methods and Materials: We stably transfected cells with a gene construct consisting of the SV40 minimal promoter, nine copies of a hypoxia-responsive element, and the yeast CD gene. During hypoxia, a hypoxia-responsive element regulates expression of the CD gene and facilitates the conversion of 5-FC to 5-fluorouracil, a highly toxic antimetabolite. We used colony-forming efficiency (CFE) and immunofluorescence assays to assess for BE in co-cultures of CD-expressing clone cells and parent, pNeo- or green fluorescent protein-stably transfected GBM cells. We also investigated the radiosensitivity of CD clone cells treated with 5-FC under hypoxic conditions, and we used flow cytometry to investigate treatment-induced cell cycle changes. Results: Both a large BE and radiosensitization occurred in GBM cells under hypoxic conditions. The magnitude of the BE depended on the number of transfected cells producing CD, the functionality of the CD, the administered concentration of 5-FC, and the sensitivity of cell type to 5-fluorouracil. Conclusion: Hypoxia-inducible CD/5-FC therapy in combination with radiation therapy shows both a pronounced BE and a radiosensitizing effect under hypoxic conditions.},
doi = {10.1016/j.ijrobp.2006.12.020},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 5,
volume = 67,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}