Interaction of the mitotic kinesin Eg5 inhibitor monastrol with P-glycoprotein

Abstract

Monastrol is the first characterised small molecule inhibitor of the motor protein Eg5 involved in bipolar mitotic spindle assembly. Eg5 localises to microtubules in mitosis, but not to interphase microtubules, suggesting that Eg5 inhibitors may be useful to specifically target proliferating tumour tissue, thereby avoiding dose-limiting neuropathy observed with other antimicrotubule agents like taxanes or vinca alkaloids. Because other antimicrotubule agents fail in multidrug resistance associated with P-glycoprotein (Pgp) over-expression, we investigated the interaction of monastrol with Pgp in vitro. By means of the calcein assay (with P388/dx cells and primary porcine brain capillary endothelial cells) and confocal laser-scanning microscopy (with L-MDR1 cells) we demonstrated that monastrol is a weak inhibitor of Pgp in vitro, with f2 values being about two orders of magnitude greater than those of the well-known inhibitors verapamil and quinidine. Monastrol also induces Pgp in vitro as measured by mRNA expression in LS180 cells after incubation with monastrol. However, its effect is weak compared to rifampicin. Whilst it reveals weak inhibitory and inductive characteristics, monastrol appears to be not transported by Pgp, as indicated by the lack of difference in the antiproliferative effect of this compound in cell lines with and without over-expression of Pgp. The observed interaction profile of monastrol with Pgp is promising for the development of other more potent Eg5 inhibitors.

Involvement of drug transporters in the synergistic action of FOLFOX combination chemotherapy

“…Cells were seeded onto collagencoated 96-well microtiter plates and preincubated for 24 h. After addition of test compounds, cells were incubated for another 48 h. Cells were then washed with PBS and stained with crystal violet 0.5% as described previously [20]. Absorption was measured using a Multiskan RC Germany) as published previously [21].…”

“…Cell proliferation was quantified by crystal violet staining [20]. Cells were seeded onto collagencoated 96-well microtiter plates and preincubated for 24 h. After addition of test compounds, cells were incubated for another 48 h. Cells were then washed with PBS and stained with crystal violet 0.5% as described previously [20].…”

Bortezomib, carfilzomib and ixazomib do not mediate relevant transporter-based drug-drug interactions

“…For the adherent LS180 cells, growth inhibition was quantified following 48 h of incubation at standard cell culture conditions via crystal violet staining of the surviving cells, as previously described (29). For the myeloma cells, an MTT assay was used to assess growth inhibition following 48 h of incubation at standard cell culture conditions, as described previously (29). Each experiment was performed in quadruplicate with n=8 wells for each concentration (0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 50 and 100 µM).…”

A potent chemotherapeutic strategy in prostate cancer: S-(methoxytrityl)-L-cysteine, a novel Eg5 inhibitor

“…15,16 S-(methoxytrityl)-L-cysteine (S(MeO)TLC), 17 a derivative of S-trityl-L-cysteine (STLC), 18 can specifically inhibit Eg5, as does STLC, 19 and induce monopolar mitotic spindle formation, but it is more than 10 times as potent as STLC. 17 Meanwhile, the functionalized indoles, such as KPYC10665 (2-(trifluoromethyl)-9H-carbazole), KPYC10666 (2-(tert-butyl)-9H-carbazole) and KPYC10728 (7-(trifluoromethyl)-9H-pyrido [3,4-b]indole), which are synthesized by one-pot Narylation-oxidative biaryl coupling of anilines and phenyl triflates, In our previous study, S(MeO)TLC displayed its potent anticancer efficacy in bladder cancer in vitro and in vivo.…”