Development of radiation inducible promoter in prostate cancer

A promoter library was developed that is composed of DNA fragments constructed by randomly elongating cis-acting elements of transcription factors presumably activated in prostate cancer by radiation, and linking to the TATA box sequence. One promoter with the strongest reactivity to X-ray in LNCap cells of the library was chosen and improved by the introduction of random mutations. A resultant promoter was designated clone 880-8 showing the highest dose-dependent activity enhancement with X-ray irradiation (X-irradiation). A recombinant retrovirus expressing the luciferase gene under the control of clone 880-8 was infected to LNCap that showed 9.12 ± 0.36-fold enhancement of luciferase activity 12 h after X-irradiation at 10 Gy. When the infected cells were inoculated onto nude mice, enhancement of luciferase expression was 4.27 ± 1.36-fold 12 h after X-irradiation at 10 Gy. When LNCap was infected with another recombinant carrying the fcy::fur gene downstream to clone 880-8, fcy::fur expression was enhanced by X-irradiation. It was also shown to increase dose-dependent cell killing ratio with 5-fluorocytosine compared to a counterpart without X-irradiation. These results suggest that the method employed in this study is effective to construct a promoter responsive to stimulation. Such promoters can be utilized for stimulation controlled-gene therapies.