Caffeine enhances the anti-tumor effect of 5-fluorouracil via increasing the production of reactive oxygen species in hepatocellular carcinoma.

The development of drug resistance affecting the prognosis of patients with hepatocellular carcinoma (HCC) leads to low survival rate of HCC patients. Caffeine is reported to have a function of protecting the liver and anti-tumor activity. Therefore, caffeine may be an ideal enhancer for HCC chemotherapy regimens. Our study showed that the combination of caffeine and 5-FU significantly inhibited the proliferation of HCC cells in vivo and in vitro comparing with caffeine or 5-FU monotherapy. The CI values of caffeine (0.5 mM) combined with 5-FU (25, 50 μM) were all less than 1, confirming that the utilization of drug combination has a synergistic inhibitory effect on the proliferation of HCC cells. Meanwhile, results of Western blot and TUNEL assays demonstrated that the apoptotic level of HCC cells in the combined group was significantly increased. The protein expression level of cleaved PARP was up-regulated, while the protein level of Bcl-2 and Bcl-xL was down-regulated. In addition, we found that ROS levels were increased in the 1 mM caffeine and 25 μM 5-FU combination group comparing with the control or single drug group. Taken together, this is the first study to demonstrate that the combination of caffeine and 5-FU inhibits HCC cells proliferation and promotes cellular apoptosis by regulating intracellular ROS production. The present data provides a basis for the application of caffeine combined with 5-FU as a novel chemotherapy regimen for HCC.