Comparison of Reversal Effects of 5-Bromotetrandrine and Tetrandrine on P-Glycoprotein-dependent Resistance to Adriamycin in Human Lukemia

BACKGROUND OBJECTIVE: 5-Bromotetrandrine (BrTet), a bromized derivative of tetrandrine (Tet), could effectively reverse P-glycoprotein (P-gp)-mediated multidrug resistance (MDR). This study was to compare the reversal effects of BrTet and Tet on MDR of human leukemia cell line K562/A02. METHODS: The effects of BrTet on the proliferation of K562 and K562/A02 cells were observed by MTT assay. The inhibitory effects of adriamycin (ADM) used alone or in combination with BrTet or Tet on the proliferation of K562 and K562/A02 cells were evaluated by MTT assay. The effect of BrTet or Tet on ADM accumulation was analyzed by flow cytometry (FCM). The protein level of P-gp was detected by Western blot. RESULTS: The inhibition rates of low concentrations of BrTet (≤2.0 μmol/L) and Tet (≤1.5 μmol/L) on the proliferation of K562 and K562/A02 cells were below 10%; no significant cytotoxicity was observed. The resistance of K562/A02 cells to ADM was 49.51 folds of that of K562 cells. When added 1.0 μmol/L Tet, the chemosensitivity of K562/A02 cells to ADM was increased to 12.17 folds; when added 0.25, 0.5 and 1.0 μmol/L BrTet, the chemosensitivity of K562/A02 cells to ADM was increased to 17.88, 9.9 and 4.24 folds, respectively. FCM showed that 1.0 μmol/L BrTet inhibited the overexpression of P-gp and increased the accumulation of ADM in K562/A02 cells, and its potency was greater than that of 1.0 μmol/L Tet(P0.05). CONCLUSIONS: BrTet could reverse MDR in vitro. Its activity may be related to the inhibition of P-gp overexpression and the increase in intracellular accumulation of anticancer drugs.