Altered membrane rigidity via enhanced endogenous cholesterol synthesis drives cancer cell resistance to destruxins
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Daniela Heilos1,2, Clemens Röhrl3, Christine Pirker1, Bernhard Englinger1, Dina Baier1,4, Thomas Mohr1, Michaela Schwaiger5, Shahid Muhammad Iqbal2, Sushilla van Schoonhoven1, Kristaps Klavins6, Tanja Eberhart3, Ursula Windberger4, Judith Taibon7, Sonja Sturm7, Hermann Stuppner7, Gunda Koellensperger5,8, Rita Dornetshuber-Fleiss1,2, Walter Jäger9, Rosa Lemmens-Gruber2 and Walter Berger1
1Institute of Cancer Research, Department of Internal Medicine I, Medical University of Vienna, Comprehensive Cancer Center of the Medical University of Vienna, Vienna, Austria
2Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
3Center for Pathobiochemistry and Genetics, Medical University of Vienna, Vienna, Austria
4Decentralized Biomedical Facilities of the Medical University of Vienna, Vienna, Austria
5Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
6BIOCRATES Life Sciences AG, Innsbruck, Austria
7Institute of Pharmacy, Pharmacognosy and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
8Vienna Metabolomics Center, University of Vienna, Vienna, Austria
9Department of Pharmaceutical Chemistry, Division of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria
Walter Berger, email: email@example.com
Keywords: cholesterol synthesis pathway; cancer cell resistance; destruxins; mycotoxins; cell membrane alterations
Received: January 15, 2018 Accepted: April 25, 2018 Published: May 22, 2018
Destruxins, secondary metabolites of entomopathogenic fungi, exert a wide variety of interesting characteristics ranging from antiviral to anticancer effects. Although their mode of action was evaluated previously, the molecular mechanisms of resistance development are unknown. Hence, we have established destruxin-resistant sublines of HCT116 colon carcinoma cells by selection with the most prevalent derivatives, destruxin (dtx)A, dtxB and dtxE. Various cell biological and molecular techniques were applied to elucidate the regulatory mechanisms underlying these acquired and highly stable destruxin resistance phenotypes. Interestingly, well-known chemoresistance-mediating ABC efflux transporters were not the major players. Instead, in dtxA- and dtxB-resistant cells a hyper-activated mevalonate pathway was uncovered resulting in increased de-novo cholesterol synthesis rates and elevated levels of lanosterol, cholesterol as well as several oxysterol metabolites. Accordingly, inhibition of the mevalonate pathway at two different steps, using either statins or zoledronic acid, significantly reduced acquired but also intrinsic destruxin resistance. Vice versa, cholesterol supplementation protected destruxin-sensitive cells against their cytotoxic activity. Additionally, an increased cell membrane adhesiveness of dtxA-resistant as compared to parental cells was detected by atomic force microscopy. This was paralleled by a dramatically reduced ionophoric capacity of dtxA in resistant cells when cultured in absence but not in presence of statins. Summarizing, our results suggest a reduced ionophoric activity of destruxins due to cholesterol-mediated plasma membrane re-organization as molecular mechanism underlying acquired destruxin resistance in human colon cancer cells. Whether this mechanism might be valid also in other cell types and organisms exposed to destruxins e.g. as bio-insecticides needs to be evaluated.
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