MDR1 promoter has been shown to contain heat shock elements (HSE), and it has been shown that FM3A/M and P388/M MDR cells show a constitutively activated heat shock factor (HSF), suggesting that HSF might be an important target for reversing the multi...
MDR1 promoter has been shown to contain heat shock elements (HSE), and it has been shown that FM3A/M and P388/M MDR cells show a constitutively activated heat shock factor (HSF), suggesting that HSF might be an important target for reversing the multidrug resistance Therefore, it was examined whether quercetin, which has been shown to interfere with the formation of the complex between HSE and HSF, and to downregulate the level of HSF1, can sensitize MDR cells against anticancer drugs by inhibition of HSF DNA-binding activity. In this study, quercetin appeared to inhibit dose-dependently the constitutive HSF DNA-binding activity and the sodium arsenite-induced HSF DNA-binding activity in the MDR cells The basal and sodium arsenite-induced MDRCAT activities were remarkably suppressed by the treatment of quercetin These findings were well consistent with the finding that the treatment of quercetin decreases the expression level of P-gp, MDR1 gene product, in dose-dependent manner, and markedly increases the sensitivity of MDR cells to vincristine or vinblastine. These results suggest that quercetin can decrease the expression of P-gp via inhibition of HSF DNA-binding activity, and might be useful as a chemosensitizer in MDR cells