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Issue 2, 2016
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Oligomycins as inhibitors of K-Ras plasma membrane localisation

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Abstract

Frequently present in pancreatic, colorectal and non-small cell lung carcinomas, oncogenic mutant K-Ras must be localised to the plasma membrane (PM) to be functional. Inhibitors of K-Ras PM localisation are therefore putative cancer chemotherapeutics. By screening a microbial extract library in a high content cell-based assay we detected the rare oligomycin class of Streptomyces polyketides as inhibitors of K-Ras PM localisation. Cultivation and fractionation of three unique oligomycin producing Streptomyces strains yielded oligomycins A–E (1–5) and 21-hydroxy-oligomycin A (6), together with the new 21-hydroxy-oligomycin C (7) and 40-hydroxy-oligomycin B (8). Structures for 1–8 were assigned by detailed spectroscopic analysis. Cancer cell viability screening confirmed 1–8 were cytotoxic to human colorectal carcinoma cells (IC50 > 3 μM), and were inhibitors of the ABC transporter efflux pump P-glycoprotein (P-gp), with 5 being comparable in potency to the positive control verapamil. Significantly, oligomycins 1–8 proved to be exceptionally potent inhibitors of K-Ras PM localisation (Emax 0.67–0.75 with an IC50 ∼ 1.5–14 nM).

Graphical abstract: Oligomycins as inhibitors of K-Ras plasma membrane localisation

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Supplementary files

Article information


Submitted
28 Sep 2015
Accepted
03 Nov 2015
First published
04 Nov 2015

Org. Biomol. Chem., 2016,14, 711-715
Article type
Paper
Author version available

Oligomycins as inhibitors of K-Ras plasma membrane localisation

A. A. Salim, L. Tan, X.-C. Huang, K.-J. Cho, E. Lacey, J. F. Hancock and R. J. Capon, Org. Biomol. Chem., 2016, 14, 711
DOI: 10.1039/C5OB02020D

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