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In many instances, multidrug resistance (MDR) is mediated by increasing the expression at the cell surface of the MDR1 gene product, P-glycoprotein (P-gp), a 170-kD energy-dependent efflux pump. The aim of this study was to investigate the potential benefit of combination therapy with magnetic Fe(3)O(4) nanoparticle [MNP (Fe(3)O(4))] and MDR1 shRNA expression vector in K562/A02 cells. For stable reversal of "classical" MDR by short hairpin RNA (shRNA) aiming directly at the target sequence (3491-3509, 1539-1557, and 3103-3121 nucleotide) of MDR1 mRNA. PGC silencer-U6-neo-GFP-shRNA/MDR1 called PGY1-1, PGY1-2, and PGY1-3 were constructed and transfected into K562/A02 cells by lipofectamine 2000. After transfected and incubated with or without MNP (Fe(3)O(4)) for 48 hours, the transcription of MDR1 mRNA and the expression of P-gp were detected by quantitative real-time PCR and Western-blot assay respectively. Meanwhile intracellular concentration of DNR in K562/A02 cells was detected by flow cytometry (FCM). PGC silencer-U6-neo-GFP-shRNA/MDR1 was successfully constructed, which was confirmed by sequencing and PGY1-2 had the greatest MDR1 gene inhibitory ratio. Analysis of the reversal ratio of MDR, the concentration of daunorubicin (DNR) and the transcription of MDR1 gene and expression of P-gp in K562/A02 showed that combination of DNR with either MNP (Fe(3)O(4)) or PGY1-2 exerted a potent cytotoxic effect on K562/A02 cells, while combination of MNP (Fe(3)O(4)) and PGY1-2 could synergistically reverse multidrug resistance. Thus our in vitro data strongly suggested that a combination of MNP (Fe(3)O(4)) and shRNA expression vector might be a more sufficient and less toxic anti-MDR method on leukemia.

Background and Objective: Resistance to cisplatin (DDP) remains a major obstacle for the successful treatment of ovarian cancer. This study was to determine the reversal effect of Fe3O4-magnetic nanoparticles (MNPs) on DDP-resistance of ovarian carcinoma cell line SKOV3/DDP, and to explore its correlation with apoptosis-associated genes., Methods: SKOV3/DDP cells were divided into the DDP group, the Fe3O4-MNPs group, the combination (DDP plus Fe3O4-MNPs) group, and the control group. Cell proliferation was determined by MTT assay. Cell apoptosis was analyzed by flow cytometry (FCM). Intracellular DDP level was detected by inductively coupled plasma atomic emission spectrometry (ICP-AES). The expressions of apoptosis-associated genes, bcl-2, and survivin were detected by reverse transcription-polymerase chain reaction (RT-PCR)., Results: Fe3O4-MNPs reversed DDP-resistance of SKOV3/DDP cells by 2.259 folds. The cell apotosis rate and the intracellular DDP level were significantly higher in the combination group than in the DDP group (P<0.05). Moreover, the mRNA levels of bcl-2 and survivin were significantly lower in the combination group than in the DDP group(P<0.05)., Conclusions: Fe3O4-MNPs can reverse the DDP resistance of ovarian carcinoma SKOV3/DDP cells, and the effect may be ascribed to the down-regulation of bcl-2 and survivin expression.

The present study was aimed to evaluate the MDR reversal activity of bromotetrandrine (BrTet) in vitro and in vivo. 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 ADM accumulation and the protein levels of P-glycoprotein (P-gp) were detected by flow cytometry. The mRNA levels of P-gp were determined by RT-PCR. The in vivo effect of BrTet and Tet was investigated by using nude mice grafted with sensitive human leukemia cell line K562 and MDR cell line K562/A02. The results showed that BrTet at 0.25, 0.5 and 1 micromol/L reversed the resistance to ADM in MDR K562/A02 cells in a dose-dependent manner. Flow cytometry suggested that BrTet significantly increased the intracellular accumulation of ADM in K562/A02 cells in a dose-dependent manner. BrTet also inhibited the overexpression of P-gp in K562/A02 cells, and down-regulated mdr1 expression. In nude mice bearing K562 xenografts on the left flank and K562/A02 xenografts on the right flank, intraperitoneal injection of 10 mg/kg BrTet significantly enhanced the antitumor activity of ADM against K562/A02 xenografts with inhibitory rates of 26.1%, while ADM alone inhibited the growth of K562/A02 xenografts only by 5.8%. No enhancement effect by BrTet was seen in K562 xenografts. It is concluded that BrTet shows significant MDR reversal activity in vitro and in vivo. Its activity may be related to the inhibition of P-gp overexpression and the increase intracellular accumulation of anticancer drugs. BrTet may be a promising-MDR modulator for eventual assessment in the clinic.

This study was aimed to investigate the reversal effect of 5-bromotetrandrine (5-BrTet) and magnetic nanoparticle of Fe(3)O(4) (Fe(3)O(4)-MNPs) combined with DNR in vivo. The xenograft leukemia model with stable multiple drug resistance in nude mice was established. The two sub-clones of K562 and K562/A02 cells were respectively inoculated subcutaneously into back of athymic nude mice (1 x 10(7) cells/each) to establish the leukemia xenograft models. Drug resistant and the sensitive tumor-bearing nude mice were both assigned randomly into 5 groups: group A was treated with NS; group B was treated with DNR; group C was treated with nanoparticle of Fe(3)O(4) combined with DNR; group D was treated with 5-BrTet combined with DNR; group E was treated with 5-bromotetrandrine and magnetic nanoparticle of Fe(3)O(4) combined with DNR. The incidence of tumor formation, growth characteristics, weight and volume of tumor were observed. The histopathologic examination of tumors and organs were carried out. The protein levels of BCL-2, BAX, and Caspase-3 in resistant tumors were detected by Western blot. The results indicated that 5-BrTet and magnetic nanoparticle of Fe(3)O(4) combined with DNR significantly suppressed growth of K562/A02 cell xenograft tumor, histopathologic examination of tumors showed the tumors necrosis obviously. Application of 5-BrTet and magnetic nanoparticle of Fe(3)O(4) inhibited the expression of BCL-2 protein and up-regulated the expression of BAX, and Caspase-3 protein in K562/A02 cell xenograft tumor. It is concluded that 5-bromotetrandrine and magnetic nanoparticle of Fe(3)O(4) combined with DNR have significant tumor-suppressing effect on MDR leukemia cell xenograft model.

To explore whether the magnetic nanoparticles of Fe3O4 (MNPs-Fe3O4) loaded with cisplatin can reverse the diaminedichloro platinum (DDP) resistance to multidrug resistance of ovarian carcinoma cells and to investigate its mechanisms. The SKOV3/DDP cells were divided into DDP treatment (DDP group), MNPs-Fe3O4 treatment (MNPs-Fe3O4 group), DDP + MNPs-Fe3O4 treatment (DDP + MNPs-Fe3O4 group), and control group. After incubation with those conjugates for 48 h, the cytotoxic effects were measured by MTT assay. Apoptosis and the intracellular DDP concentration were investigated by flow cytometry and inductively coupled plasma atomic emission spectroscopy, respectively. The expression of apoptosis associated gene Bcl-2 mRNA was detected by reverse transcription polymerase chain reaction and the expressions of MDR1, lung resistance-related protein (LRP), and P-glycoprotein (P-gp) genes were studied by Western blot. Our results indicated that the 50% inhibition concentration (IC50) of the MNPs-Fe3O4 loaded with DDP was 17.4 micromol/l, while the IC50 was 39.31 micromol/l in DDP groups (p < 0.05); Apoptosis rates of SKOV3/DDP cells increased more than those of DDP groups. Accumulation of intracellular cisplatin in DDP + MNPs-Fe3O4 groups was higher than those in DDP groups (p < 0.05). Moreover, the expression of Bcl-2 mRNA and the protein expressions of MDR1, LRP, and P-gp were decreased when compared with those of DDP groups, respectively. Our results suggest that MNPs-Fe3O4 can reverse the DDP resistance to the ovarian carcinoma cell. The effects may be associated with over-expression of MDR1, LRP, P-gp, and Bcl-2, which can increase the intracellular platinum accumulation and induce the cell apoptosis.