Chemo-radio-gene therapy for colorectal cancer cells using Escherichia coli uracil phosphoribosyltransferase gene.

5-Fluorouracil (5-FU) is one of the most widely used chemotherapeutic agents, and is known to be a radiosensitizer. Previously, we reported that adenoviral transduction of the Escherichia coli (E. coli) uracil phosphoribosyltransferase (UPRT) gene induced marked sensitivity in human colon cancer cells to 5-FU. The aim of the current study was to investigate the efficacy of virally-directed UPRT and 5-FU to enhance the radiosensitivity of HT29 human colon cancer cells. Cytotoxicity as a result of radiation treatment following AdCA-UPRT infection and 5-FU exposure was confirmed by radiation dose-response analysis with colony formation assay. In vivo chemoradio-gene therapy using the UPRT/5-FU/radiation system showed tumor regressive effects even against large HT29-established subcutaneous tumors in nude mice. Our results suggested that adenovirus-mediated UPRT gene transduction combined with 5-FU administration and radiation may be an effective new chemo-radio-gene therapy for colorectal cancer.