ABSTRACT
Aim To investigate the reversal effect of vatalanib, a novel kinase inhibitor, on multidrug re-sistance in cancer cells and its mechanism. Methods The cytotoxicity and reversal effects of vatalanib were evaluated in both resistant and sensitive tumor cell lines by MTS or SRB assays. The intracellular accumu-lation of fluorescence substrates ( Rh-123 , MX and ADR for P-gp, BCRP, MRP1, respectively) were ana-lysed by flow cytometry. Western blot or qRT-PCR was used to determine the protein or mRNA expression lev-el of BCRP. The effect of vatalanib on ATPase activity of BCRP was determined using crude membranes pre-pared from HEK293/ABCG2 cells. Results Vata-lanib at the nontoxic dose ( 5 μmol · L-1 ) potentially reversed BCRP-mediated MDR in cancer cells, howev-er it had no effect on P-gp or MRP1 mediated MDR. Vatalanib did not alter the intracellular accumulation of MX in HEK 2 9 3 / ABCG 2 , and had no influence on the BCRP-mediated drug efflux. The ATPase assay indica-ted that vatalanib may serve as a substrate of BCRP. Furthermore, vatalanib dramatically suppressed levels of both the protein and mRNA expression of BCRP in concentration-and time-dependent manners. However, reversal concentration of vatalanib had no influence on the total and phosphorylated forms of AKT and ERK1/ 2 in resistant cancer cells. Conclusion Vatalanib could significantly reverse BCRP-mediated MDR with specificity, and its mechanism may correlate with the down-regulation levels of BCRP both mRNA and pro-tein in resistant cancer cells.
ABSTRACT
To investigate the relationship between p38 mitogen-activated protein kinase (p38MAPK)and cell apoptosis during the paclitaxel resistance of ovarian carcinoma cell lines, flow cytometry(FCM) and PI staining were employed to determine the effect of p38MAPK inhibitor SB203580 onthe apoptosis of A2780/Taxol cells, a drug-resistant human ovarian carcinoma cell line. p38MAPKprotein expression in SB203580-treated cells was immunochemically measured. The 50% inhibitionconcentration (IC<,50) of paclitaxel on A2780/Taxol cells was determined by MTT assay. MDR-1mRNA, and expression of p38MAPK and phospho-p53 protein were detected by RT-PCR and West-ern blotting, respectively. The apoptosis rate of A2780/Taxol cells was (19.7±1.04)% 24 h afterSB203580 treatment. A significant difference in apoptosis rate was found among experiment group,control group and untreated group (P<0.05). The relative reversal rate of A2780/Taxol cells to pacli-taxel was (57.18±2.01)%. As compared with the control group and the untreated group, p38MAPKprotein and MDR-1 mRNA in SB203580-treated cells was substantially decreased. The expression ofp53 protein was significantly increased. It is concluded that p38MAPK pathway is related to pacli-taxel resistance of ovarian carcinoma, and blockade of this pathway can promote the apoptosis of thedrug-resistant cells and reverse the drug-resistance. Moreover, p38MAPK-mediated apoptosis in pa-clitaxel-resistant ovarian carcinoma cells depends on the activation of p53.