The Study Of Taxane Analogues On The Interaction With Different ?-tubulin Isotypes And Drug Resistance

Objective: Microtubules,an important component of the cell cytoskeleton,are involved in the cell mitosis and the motor transmission.They are one of the most important targets for the treatment of malignant tumors.Taxane analogues,a class of microtubule stabilizers,prevent microtubule depolymerization to block the cell cycle and mitosis,thereby causing the cancer cell death.Paclitaxel,docetaxel,and cabazitaxel are widely used in clinical treatment.Clinical studies have shown that paclitaxel and docetaxel are effective in the early stage of treatment,but they are easy to develop tolerance.Cabazitaxel can be used to further treat patients with resistance to paclitaxel or docetaxel.The computational studies of taxane analogues currently are mainly focused on the structural modification or nano-targeted drug design.Our group has completed the theoretical research on paclitaxel and docetaxel.And the purposes of this paper are to further understand the action process and drug resistance of different taxane analogues through theoretical calculations,and to provide a theoretical basis for future experimental research.Methods: In the research,we studied the interaction of three taxane analogues with different tubulin isotypes and P-glycoprotein by computer simulation.Firstly,the quantum mechanics was used to optimize the conformation of cabazitaxel and the same density functional theory as the previous study was used to study the properties of cabazitaxel.Then,the molecular dynamics was used to simulate the effects of three taxane analogues.We built the three-dimensional models of different human tubulin isotypes and P-glycoprotein by homology modeling,found the action sites and orientations of taxane analogues with proteins by molecular docking,as well as simulated the three taxane analogues with various tubulin isotypes and P-glycoprotein to study the similarities and differences of their interaction at the residue level by molecular dynamics simulations.Finally,the quantum mechanics/molecular mechanics was used to calculate the more accurate binding free energies,so as to further study the effects and drug resistance of different taxane analogues.Results: Firstly,we obtained the lowest-lying conformation and the theoretical properties of cabazitaxel in the gaseous state or solution.The molecular docking and molecular dynamics simulations of the interaction between three taxane analogues and different tubulin isotypes showed that the action sites of the three taxane analogues were at the Taxanes sites on ?-tubulin,but the key amino acids and orientations of binding conformations are different.According to the results of binding free energies,the binding affinity of paclitaxel with ??a-tubulin and that of docetaxel with ??-tubulin were much higher than those with ??-tubulin.The binding affinities of cabazitaxel with ??-tubulin and ??a-tubulin are lower than those of paclitaxel and docetaxel,but that with ??-tubulin is comparable with ??a-tubulin.The results of the interaction between three taxane analogues and P-glycoprotein showed that the binding of them are greatly varied,and the binding affinity of docetaxel to P-glycoprotein was higher than that of cabazitaxel.Conclusions: According to the interaction of three taxane analogues with different tubulin isotypes,paclitaxel and docetaxel binding to ??-tubulin and ??-tubulin isotypes play an important role in drug therapy,while the overexpression of ??-tubulin increases the drug resistance to paclitaxel and docetaxel.This is consistent with the clinical results of Magnani et al.(FEBS J.2006)and Urano et al.(Int.J.Oncol.2006).However,the binding affinity of cabazitaxel is comparable with that on ??a-tubulin,indicating that the overexpression of ??-tubulin has little influence for cabazitaxel,which was observed by Smiyun et al.(Cancer Chemother.Pharmacol.2017).The theoretical research supports the use of cabazitaxel for patients who are resistant to the action of paclitaxel and docetaxel.In addition,by calculating the sequence-variation amino acid sites,we have also found that the sequence-variation sites on the ??-tubulin isotypes would weaken the binding of drugs.The study about the interaction of three taxane analogues with P-glycoprotein showed that the taxane analogues did not act at fixed sites with the P-glycoprotein,and the small molecules were removed from the cell by intermolecular forces.The research finds that docetaxel has a higher binding affinity to P-glycoprotein than cabazitaxel.