RM-581 is an aminosteroid derivative comprised of a
steroid core and a
quinoline side chain showing potent cytotoxic activity on several types of
cancer cells but for which the mechanism of action (MoA) remains to be fully elucidated. The opportunity to turn
RM-581 into a
fluorescent probe was explored because the addition of a N-dimethyl group was recently reported to induce fluorescence to
quinoline derivatives. After the chemical synthesis of the N-dimethyl analogue of
RM-581 (RM-581-Fluo), its fluorescent properties, as well as its cytotoxic activity in
breast cancer MCF-7 cells, were confirmed. A cell imaging experiment in MCF-7 cells using confocal microscopy then revealed that RM-581-Fluo accumulated into the endoplasmic reticulum (ER) as highlighted by its colocalization with an ER-Tracker
dye. This work provides a new tool for
RM-581 MoA investigations as well as being a relevant example of a tailor-made
quinolone-fluorescent version of a bioactive molecule.