Gemcitabine is currently the best treatment available for
pancreatic cancer, but causes high toxicity. Agents that can enhance the effects of
gemcitabine with no or low toxicity are needed for the treatment of
pancreatic cancer.
Emodin, a natural
anthraquinone derivative, is one such agent that has been shown to induce apoptosis in other
tumor cells via down-regulation of Bcl-2/Bax and promoting the release of
Cytochrome C (CytC), but with very low toxicity. The aim of this study was to evaluate whether
emodin can enhance the effect of
gemcitabine on
pancreatic cancer in vitro and in vivo and to investigate the possible mechanisms of the enhancement. In vitro,
emodin inhibited the proliferation of the SW1990 cell line and potentiated the apoptosis induced by
gemcitabine, which was demonstrated by activation of
caspase-3 in the combination group. In vivo,
tumors from nude mice subcutaneously injected with SW1990 cells and treated with a combination of
emodin (40 mg/kg) and
gemcitabine (80 mg/kg) showed significant reductions in volume, Ki-67 proliferation index and expression of the Bcl-2/Bax ratio (compared with
tumors from mice treated with
sodium chloride,
emodin alone (40 mg/kg) or
gemcitabine alone (125 mg/kg), which induced increasing release of CytC from the mitochondria to the cytoplasm and triggered
caspase-3 activation leading to apoptosis. Taken together, our results suggest that
emodin improved the anti-
tumor effect of
gemcitabine, even at a lower dose of
gemcitabine which could decrease the toxicity of
chemotherapy, on transplanted
tumors of the SW1990 cell line through the enhancement of apoptosis induced by
gemcitabine, the mechanism of which may be through down-regulation of the Bcl-2/Bax ratio and promoting release of CytC from the mitochondria into the cytoplasm.