Although
coffee is known to have
antioxidant, anti-inflammatory, and antitumor properties, there have been few reports about the effect and mechanism of
coffee compounds in
colorectal cancer.
Heat shock proteins (HSPs) are
molecular chaperones that prevent cell death. Their expression is significantly elevated in many
tumors and is accompanied by increased cell proliferation,
metastasis and poor response to
chemotherapy. In this study, we investigated the cytotoxicity of four bioactive compounds in
coffee, namely,
caffeine,
caffeic acid,
chlorogenic acid, and
kahweol, in HT-29 human
colon adenocarcinoma cells. Only
kahweol showed significant cytotoxicity. Specifically,
kahweol increased the expression of
caspase-3, a pro-apoptotic factor, and decreased the expression of anti-apoptotic factors, such as Bcl-2 and phosphorylated Akt. In addition,
kahweol significantly attenuated the expression of HSP70. Inhibition of HSP70 activity with
triptolide increased
kahweol-induced cytotoxicity. In contrast, overexpression of HSP70 significantly reduced
kahweol-induced cell death. Taken together, these results demonstrate that
kahweol inhibits
colorectal tumor cell growth by promoting apoptosis and suppressing HSP70 expression.