engleski

Proprietary crown ethers significantly inhibit P-glycoprotein activity

Cancer stem cells (CSCs) are regarded as a leading cause of cancer relapse due to their ability to reconstitute tumour’s heterogeneity even after its eradication. It has been suggested that CSC resistance to chemo- and radiotherapy could be related to enhanced survival pathways, decreased levels of reactive oxygen species and increased expression of drug efflux pumps. Nevertheless, related molecular mechanisms remain elusive. Recent research has pinpointed salinomycin, a naturally occurring potassium ionophore, as a promising compound for targeting CSCs. Moreover, several studies indicate that one of the mechanisms of action of salinomycin towards CSCs is the inhibition of P-gp drug efflux pump activity. Pertaining to the mentioned studies and results previously published by our group regarding anticancer activity of proprietary crown ethers that act as K+ ionophores, we hypothesized that these compounds could show selectivity towards CSCs. Therefore, we set about to elucidate their mechanism of action, with the focus on the effect towards the function and activity of drug efflux pumps. To evaluate the impact of proprietary crown ethers on cancer cells with respect to P-gp expression, we used a multidrug resistance model cell lines A2780 and A2780/Adr, latter having overexpressed P-gp. Cytotoxicity evaluated by MTT showed increased resistance of A2780/Adr cells to P-gp substrates (e.g. doxorubicine, paclitaxel), as expected. Rhodamine efflux assay was performed in order to assess the functional activity of P-gp. Obtained results showed strong inhibition by proprietary compounds, while combined treatment with paclitaxel indicated cell sensitization towards this chemotherapeutic. These results were further confirmed by cell cycle analysis and annexin V assay. Additionally, implications of crown ether molecular mechanisms of action were obtained by analysis of the impact of these compounds on P-gp expression and upstream regulators of this drug efflux pump. Results indicate stronger P-gp inhibition obtained by proprietary crown ether treatment than by the commercially available P-gp inhibitor, verapamil. Additionally, plausible molecular mechanisms of action of crown ether compounds will be presented.

cancer stem cells, ABC transporters, P-gp, crown ethers

nije evidentirano