Identification of a lathyrane-type diterpenoid EM-E-11-4 as a novel paclitaxel resistance reversing agent with multiple mechanisms of action.

Qian Liu,Jiangong Shi,Hua Sun,Siwei Guo,Pei Cai

doi:10.18632/aging.102842

Abstract

P-glycoprotein (P-gp) and βIII-tubulin overexpression-mediated drug resistance leads to clinical therapy failure for paclitaxel. However, the development of paclitaxel-resistance reversal agents has not had much success. In this study, EM-E-11-4, a lathyrane-type diterpenoid extracted from Euphorbia micractina, demonstrated good anti-MDR (multidrug resistance) activity in paclitaxel-resistant tumor cells overexpressing either P-gp or βIII-tubulin. EM-E-11-4 was able to recover the effects of paclitaxel in inducing arrest at G2/M phase and apoptosis in both A549/Tax (P-gp overexpression) and Hela/βIII (βIII-tubulin overexpression) cells, respectively, at a non-cytotoxic dose. EM-E-11-4 could enable Flutax-1 and Rhodamine 123 be accumulated intracellularly at an accelerating rate in A549/Tax cells by inhibiting the activity of P-gp ATPase, rather than affecting the expression of P-gp. In addition, it also strengthened the effects of paclitaxel in promoting tubulin polymerization and the binding of paclitaxel to microtubules in vitro. It inhibited the expression of βIII-tubulin in Hela/βIII cells in a dose-dependent manner while not exerting influence on the other β-tubulin subtypes. As far as we know, this is the first study to report that a small molecule natural product could specifically inhibit the expression of βIII-tubulin. These results suggest EM-E-11-4 may serve as a promising MDR reversal agent, particularly for patients bearing tumors with high expression of P-gp and βIII-tubulin.

Highlights

Chemotherapy is an alternative therapeutic method for patients with cancer
The cytotoxicity of EM-E-11-4 was examined by an MTT assay in A549/Tax and Hela/βIII cell lines
These results indicate that EM-E-11-4 could reverse paclitaxel-resistance mediated through P-gp or βIII-tubulin

Summary

Introduction

Chemotherapy is an alternative therapeutic method for patients with cancer. the outcome is not always satisfactory because drug resistance can develop during the course of treatment. As a vital transporter of the ATP-binding cassette (ABC) family [9,10], P-gp is encoded by abcb1/mdr gene [11], functioning as an ATP-dependent broad-spectrum drug efflux pump, and the drug concentration in cells is downregulated by P-gp. It is involved with lots of structurally uncorrelated anti-cancer drugs, for instance, paclitaxel, docetaxel, doxorubicin, and vincristine [12], and that can lead to multidrug resistance (MDR). There has been a certain degree of success in the development of P-gp-mediated paclitaxel resistance reversal agents [16,17,18]

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Conclusion