Abstract
Methylxanthine derivatives increase cAMP and are known to have diuretic, cardiac, and central nervous system stimulatory effects. Moreover, caffeine inhibits the development of tumors induced by various carcinogens. The aim of this work was to elucidate the anticancer effects on apoptosis of xanthine derivatives alone and with doxorubicin in canine hemangiosarcoma cells. Xanthine derivatives with or without doxorubicin were administered to cells, and the effects were investigated by measuring tumor cell proliferation, cell death (cytotoxicity) induction, and apoptosis by the expression of annexin V or caspase 3/7. Both caffeine and theophylline induced apoptosis, and the treated cells expressed annexin V and caspase 3/7. Both drugs enhanced doxorubicin-induced cytotoxicity; however, hypoxanthine showed no effect. These results indicate that theophylline is similar to caffeine; both drugs may enhance doxorubicin-induced cytotoxicity by inhibiting ATM/ATR kinases. Our data suggest that caffeine and theophylline have anticancer effects and can improve the treatment effect in canine hemangiosarcoma patients.