Triplex metallohelices have enantiomer-dependent mechanisms of action in colon cancer cells

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-05, Vol.52 (2), p.6656-6667
• Main Authors: Coverdale, J. P. C, Kostrhunova, H, Markova, L, Song, H, Postings, M, Bridgewater, H. E, Brabec, V, Rogers, N. J, Scott, P
• Format: Article
• Language: English
• Subjects: Actins; Binding; Cell cycle; Colonic Neoplasms - drug therapy; Colorectal cancer; Depolymerization; Dichroism; DNA - chemistry; Efflux; Enantiomers; Flow cytometry; Fractionation; Grooves; Helicity; Humans; Microtubules; Self-assembly; Temperature dependence; Tubulin - metabolism
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d3dt00948c

Self-assembled enantiomers of an asymmetric di-iron metallohelix differ in their antiproliferative activities against HCT116 colon cancer cells such that the compound with Λ-helicity at the metals becomes more potent than the Δ compound with increasing exposure time. From concentration- and temperature-dependent 57 Fe isotopic labelling studies of cellular accumulation we postulate that while the more potent Λ enantiomer undergoes carrier-mediated efflux, for Δ the process is principally equilibrative. Cell fractionation studies demonstrate that both enantiomers localise in a similar fashion; compound is observed mostly within the cytoskeleton and/or genomic DNA, with significant amounts also found in the nucleus and membrane, but with negligible concentration in the cytosol. Cell cycle analyses using flow cytometry reveal that the Δ enantiomer induces mild arrest in the G 1 phase, while Λ causes a very large dose-dependent increase in the G 2 /M population at a concentration significantly below the relevant IC 50 . Correspondingly, G 2 -M checkpoint failure as a result of Λ-metallohelix binding to DNA is shown to be feasible by linear dichroism studies, which indicate, in contrast to the Δ compound, a quite specific mode of binding, probably in the major groove. Further, spindle assembly checkpoint (SAC) failure, which could also be responsible for the observed G 2 /M arrest, is established as a feasible mechanism for the Λ helix via drug combination (synergy) studies and the discovery of tubulin and actin inhibition. Here, while the Λ compound stabilizes F-actin and induces a distinct change in tubulin architecture of HCT116 cells, Δ promotes depolymerization and more subtle changes in microtubule and actin networks. Modes of cancer cell influx/efflux and molecular mechanism of action depend on absolute configuration at the metal.