In vitro pro-oxidant action of Methotrexate in presence of white light

Methotrexate (MTX) an anti-cancer drug as well as a photosensitizer is able to generate reactive oxygen species (ROS). Cu (II) is present associated with chromatin in cancer cells and has been shown to be capable of mediating the action of several anti-cancer drugs through production of ROS. The objective of the present study is to determine Cu (II) mediated anti-cancer mechanism of MIX under photoilluminated condition as well as alone, using alkaline single cell gel electrophoresis (comet assay). We have shown that cellular DNA breakage was enhanced when Cu (II) is used with MIX as compared to MIX alone. It is also shown that MIX alone as well as in combination with Cu (II) is able to generate oxidative stress in lymphocyte which is inhibited by scavengers of ROS but the pattern of inhibition was differential as was also demonstrated by plasmid nicking assay. Thus, we can say that MTX exhibit pro-oxidant action in presence of white light which gets elevated in presence of Cu (II). Hence, we propose that the mobilization of endogenous copper is possibly involved in killing of cancer cells by MIX during chemo-radio therapy besides acting as antifolate. (C) 2011 Elsevier B.V. All rights reserved.