Figure 5

DNA repair activity of APE1 plays a critical role in melphalan resistance of MM cells. (A) The difference in DNA repair activity of APE1 between RPMI-8226/LR5 and RPMI-8226 cells was analyzed using AP site incision assay. The results indicated that the RPMI-8226/LR5 cells possess a higher AP endonuclease activity than its parental line. (B) The overall DNA repair activity for single DNA strand breaks was assayed by the alkaline comet assay. Cell suspensions from both RPMI-8226/LR5 and RPMI-8226 cells were treated with 15 μM melphalan on ice for 20 min, then the comet assay was performed immediately or after a 30 min repair in culture medium in a 37°C incubator. Representative images are shown.