Effect of Novobiocin on Repair of Hydrogen Peroxide and UV-induced DNA Damage in Tumour Cell Lines by Modified Comet Assay

Abstract

In the present study, a modified comet assay for treatment and extended periods of post-incubation of cells embedded in agarose on microscope slides was used. The human prostate adenocarcinoma PC3 cell line and colon adenocarcinoma HCT116 cell line were used. The survival of PC3 cells in these conditions was evaluated up to 48 h post-incubation after treatment, showing high percentage of viable cells and proliferative activity. The repair of DNA strand breaks induced by hydrogen peroxide and UV light in PC3 and HCT116 cell lines was evaluated for periods of 1 h and 24 h of post-incubation in complete culture medium. The effect of the DNA Polymerase theta inhibitor novobiocin was also investigated. The PC3 cell line showed decrease in the induced DNA strand breaks at 24 h of post-incubation for both agents, indicating DNA repair process. In the HCT116 cell line, a similar decrease in DNA strand breaks was observed only in absence of novobiocin in the post-incubation medium. This could suggest involvement of DNA Polymerase theta in the repair process of the HCT116 cell line. Our results indicated the utility of the modified comet assay to study the effect of DNA repair inhibitors on the action of chemotherapeutic agents.