Disulfiram, a clinically used alcohol-deterrent has gained prominence as a potential anti-
cancer agent due to its impact on
copper-dependent processes. Few studies have investigated
zinc effects on
disulfiram action, despite it having high affinity for this
metal. Here we studied the cytotoxic effects of
disulfiram in
breast cancer cells, and its relationship with both intra and extracellular
zinc. MCF-7 and BT474
cancer cell lines gave a striking time-dependent biphasic cytotoxic response between 0.01 and 10 μM
disulfiram. Co-incubation of
disulfiram with low-level
zinc removed this effect, suggesting that availability of extracellular
zinc significantly influences
disulfiram efficacy. Live-cell confocal microscopy using fluorescent endocytic probes and the
zinc dye Fluozin-3 revealed that
disulfiram selectively and rapidly increased
zinc levels in endo-lysosomes.
Disulfiram also caused spatial disorganization of late endosomes and lysosomes, suggesting they are novel targets for this
drug. This relationship between
disulfiram toxicity and
ionophore activity was consolidated via synthesis of a new
disulfiram analog and overall we demonstrate a novel mechanism of
disulfiram-cytotoxicity with significant clinical implications for future use as a
cancer therapeutic.