Caffeine and other methylxanthines produce multiple physiologic effects throughout the human body, many of these effects could potentially modulate the activity of anticancer therapy. Caffeine may directly interfere with drug transport to tumor cells by formation of mixed stacking complexes with polyaromatic drugs. If formed in cells, these complexes may also prevent of intercalating drugs from DNA binding and, in this way, lower their antitumor activity. Since many of potent carcinogens are polyaromatic compounds, formation of stacking complexes with carcinogens could be associated with anti-genotoxic activity of caffeine and its use in cancer chemoprevention. Caffeine has also been reported to inhibit ATM and ATR kinases which leads to the disruption of multiple DNA damage-responsive cell cycle checkpoints and greatly sensitizes tumor cells to antitumor agents which induce genotoxic stress. Caffeine may inhibit repair of DNA lesions through a direct intereference with DNA-PK activity and other repair enzymes. A number of in vitro and in vivo studies demonstrated that caffeine modulates both innate and adaptive immune responses via inhibition of cyclic adenosine monophosphate (cAMP)-phosphodiesterase. Finally, another group of effects induced by caffeine is mediated through its inhibitory action on adenosine receptors. This may modulate the stability of HIF1 alpha as well as VEGF and interleukin-8 expression in tumor cells, which could have a direct impact on neovascularization of human tumors. In this review, we present different molecular mechanisms by which caffeine and other methylxanthines may directly or indirectly modulate the effect of antitumor treatment in tumor cells and in cancer patients.
Keywords: Modulation, anticancer therapy, cell cycle, checkpoints, DNA repair, caffeine analogs, antitumor drug, irradiation
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