bromotetrandrine and tetrandrine

Multidrug resistance has remained a major cause of treatment failure in chemotherapy due to the presence of P-glycoproteins (P-gp) that actively pump drugs from inside the cell to the outside. P-gp inhibitors were developed and coadministered with chemotherapeutic drugs to overcome the effect of efflux pumps thus enhancing the chemosensitivity of therapeutics. Our study aimed at developing a lipid nanoemulsion system for the coencapsulation of doxorubicin (DOX) and bromotetrandrine (W198) to reverse multidrug resistance (MDR) in breast cancer. W198 was a potent P-gp inhibitor, and DOX was selected as a model compound which is a common substrate for P-gp. Coencapsulated DOX and W198 lipid nanoemulsions (DOX/W198-LNs) displayed significantly enhanced cytotoxicity in DOX-resistant human breast cancer cells (MCF-7/ADR) compared with DOX loaded lipid nanoemulsions (DOX-LNs) (p < 0.05), which is due to the enhanced intracellular uptake of DOX in MCF-7/ADR cells. The biodistribution study was performed using a nude mice xenograft model, which demonstrates enhanced tumor uptake of DOX in the DOX/W198-LN treated group. Compared with DOX solution, DOX/W198-LNs showed reduced cardiac toxicity and gastrointestinal injury in rats. Taken together, DOX/W198-LNs represent a promising formulation for overcoming MDR in breast cancer.

Topics: Animals; Antineoplastic Agents; Apoptosis; Benzylisoquinolines; Breast Neoplasms; Cell Line, Tumor; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Emulsions; Female; Humans; Lipids; Mice; Mice, Nude; Nanomedicine; Necrosis; Neoplasm Transplantation; Rats; Rats, Wistar; Tissue Distribution

Both tetrandrine (Tet) and 5-bromotetrandrine (BrTet) can effectively reverse P-glycoprotein (P-gp)-mediated multidrug resistance (MDR). The structure of multidrug resistance associated protein 7 (MRP7) has its own specificity and difference compared with other members of the MRP family. This study was aimed to investigate whether Tet and BrTet can inhibit the expression level of MRP7 so as to further look into the mechanisms of the reversal effects of Tet and BrTet on MDR. The inhibitory effects of daunorubicin (DNR) used alone on the proliferation of K562 and K562/A02 cells were evaluated by MTT assay, the IC(50) of DNR and drug resistant folds were calculated. The mRNA level of MRP7 was tested by real-time PCR, and the protein levels of MRP7 and P-gp were tested by Western blot. The DNR accumulation was analyzed by flow cytometry (FCM). The results showed that the resistance of K562/A02 cells to DNR was 23.65-folds of that of K562 cells. After administration of 1 µmol/L Tet or 2 µmol/L BrTet, the mRNA level of MRP7 in the K562/A02 cells decreased to 2% and 12% respectively, and the protein level of MRP7 decreased by 53.2% and 83.7% respectively. The protein level of P-gp decreased by 58.47% and 52.20% in the 1 µmol/L Tet and 2 µmol/L BrTet groups. FCM detection showed that 1 µmol/L Tet and 2 µmol/L BrTet significantly increased the accumulation of DNR in K562/A02 cells by 94.32% and 271% respectively. It is concluded that Tet and BrTet both can reverse MDR in vitro. The mechanisms may be related to the inhibition of MRP7 overexpression and the increase of anticancer drug concentration in cells. At the same molar concentration, the effects of Tet and BrTet in inhibiting the protein level of MRP7 expression do not show significant difference.

Topics: Benzylisoquinolines; Down-Regulation; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Humans; K562 Cells; Multidrug Resistance-Associated Proteins

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.. 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.. The inhibition rates of low concentrations of BrTet (< or =2.0 micromol/L) and Tet (< or =1.5 micromol/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 micromol/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 micromol/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 micromol/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 micromol/L Tet(P<0.05).. 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.

Topics: Antibiotics, Antineoplastic; Antineoplastic Agents, Phytogenic; ATP Binding Cassette Transporter, Subfamily B, Member 1; Benzylisoquinolines; Cell Proliferation; Doxorubicin; Drug Resistance, Neoplasm; Humans; K562 Cells