Quercetin is a
flavonoid well known to inhibit growth and
heat shock protein (HSP) synthesis of
cancer cells. However,
sunphenon has been scarcely reported concerning effects on
cancer cells. We compared the effects of
sunphenon with those of
quercetin on the human cholangio-cellular
carcinoma cell line (HuCC-T1). Both
flavonoids inhibited HuCC-T1 growth in a concentration-dependent manner without reduction of HSP70 and HSP90 expression before heat shock damage. The heat shock reduced the cell viability of the
quercetin-treated HuCC-T1, but not that of the
sunphenon-treated cells. This inhibitory effect of
quercetin on tolerance to heat shock is thought to be due to marked suppression of HSP72.
Sunphenon conversely increased HSP72 expression after heat shock. Although neither
flavonoid altered HSP90
protein levels before and after heat shock,
quercetin delayed the reorganization of filamentous actin (
F-actin) during the recovery period after heat shock. Since HSP90 could preserve
F-actin structure during stresses,
quercetin might affect the interaction between HSP90 and
F-actin without influencing HSP90 expression. In conclusion,
quercetin would be more useful than
sunphenon in combined
therapy with
hyperthermia for
cancer.