tumor drugs by 62 117 times was the second most active similar effects were observed in k562 dr and kb v1 cells cis dmdck exhibited multidrug resistance reversing ability that was obviously superior to the other three compounds in hepg2 dr or k562 dr cells trans dmdck and trans dmdbk also showed significant effect but were less effective than cis dmdck and cis dmdbk in kb v1 cells however trans dmdck and trans dmdck exhibited limited ability in reducing drug resistance for example decrease in ic 50 values of vinblastine or doxorubicin in the presence of 4 u03bcm of trans dmdck or trans dmdck was less than 5 folds the ability of the four compounds for reversing drug resistance of tumor cells are listed as following cis dmdck gt cis dmdbk gt trans dmdck and trans dmdbk 1 4 drug treatment hepg2 and hepg2 dr cells were respectively treated with each of cis dmdck cis dmdbk trans dmdck trans dmdbk and doxorubicin for 48 hours or treated respectively with the combination of doxorubicin and one of cis dmdck cis dmdbk trans dmdck trans dmdbk for 48 hours 1 5 treatment and detection of sample cells after washed twice by ice cold pbs the cells were fixed with 70 ethanol at u2212 20 u00b0 c overnight the fixed.