Suicide gene therapy on LNCaP human prostate cancer cells

The efficacy of combination suicide gene therapy was evaluated using a Herp es simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) system and an Es cherichia coli cytosine deaminase/5-fluorocytosine (CD/5-FC) system on the LNCaP human prostate cancer cell model. Two types of plasmid vectors with t he HSV-TK gene were constructed. A constitutive chicken P-actin promoter dr ove one and a prostate-specific antigen (PSA) promoter drove the other. Sim ilarly, a pair of plasmids with the CD gene under a cytomegalovirus (CMV) p romoter and the PSA promoter was also constructed. LNCaP cells were transfe cted in vitro with either or both of those plasmids using a cationic lipid reagent. Transfected cells were treated with GCV and/or 5-FC. The percentag e of viable LNCaP cells 7 days after treatment with HSV-TK/GCV or CD/5-FC u nder a constitutive promoter was 40% and 41% of controls, respectively. The cell viability when two suicide genes were combined was 23%. The cell viab ilities after four days with PSA promoter-HSV-TK vectors, CD vectors and a combination of both were 79%, 88% and 88%, respectively. Suicide gene thera py using either HSV-TK/GCV, CD/5-FC, or both, was effective in the LNCaP mo del. An additive effect was observed when the two suicide genes were used t ogether. The PSA promoter did not seem to be effective enough to elicit cyt otoxicity under the experimental conditions used here.