Abstract
Our previous studies showed that several sipholane triterpenes, sipholenol A, sipholenone E, sipholenol L and siphonellinol D, have potent reversal effect for multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp/ABCB1). Through comparison of cytotoxicity towards sensitive and multi-drug resistant cell lines, we identified that the semisynthetic esters sipholenol A-4-O-acetate and sipholenol A-4-O-isonicotinate potently reversed P-gp-mediated MDR but had no effect on MRP1/ABCC1 and BCRP/ABCG2-mediated MDR. The results from [3H]-paclitaxel accumulation and efflux studies suggested that these two triterpenoids were able to increase the intracellular accumulation of paclitaxel by inhibiting its active efflux. In addition, western blot analysis revealed that these two compounds did not alter the expression levels of P-gp when treated up to 72 h. These sipholenol derivatives also stimulated the ATPase activity of P-gp membranes, which suggested that they might be substrates of P-gp. Moreover, in silico molecular docking studies revealed the virtual binding modes of these two compounds into human homology model of P-gp. In conclusion, sipholenol A-4-O-acetate and sipholenol A-4-O-isonicotinate efficiently inhibit the P-gp and may represent potential reversal agents for the treatment of multidrug resistant cancers.
Highlights
Multi-drug Resistance (MDR) is a major clinical obstacle in the treatment of cancer
This demonstrated that P-gp overexpressing HEK/ABCB1 cells were re-sensitized to paclitaxel by SSJ26 and SSJ32 treatment
Our results indicated that SSJ26 and SSJ32 did not show reversal effect on
Summary
Multi-drug Resistance (MDR) is a major clinical obstacle in the treatment of cancer. The cause of MDR is diversely characterized by multiple alterations in protein expression. Many scientists aim to inhibit the P-gp transporter to reverse MDR and again re-sensitize the cancer cells at clinically effective doses of chemotherapeutic agents. Several semisynthetic analogs of sipholenol A were synthesized and showed potent breast cancer migration inhibitory activities [19,20] These sipholenol analogs have close structural and pharmacophoric similarities to the previously described compounds that showed drug-resistance reversal properties. They were first tested for cytotoxicity on cancer cells and for reversal of. A-4-O-isonicotinate (SSJ32) demonstrated P-gp inhibition comparable to that of verapamil In this study, these two compounds were further analyzed to elucidate their mechanism of action and strengthen their value as potential P-gp-mediated drug resistance reversal agents
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