In the current work, we investigated the biochemical toxicity of
acetylsalicylic acid (ASA;
Aspirin) in human
melanoma cell lines using
tyrosinase enzyme as a molecular
cancer therapeutic target. At 2 h, ASA was oxidized 88% by
tyrosinase.
Ascorbic acid and
NADH,
quinone reducing agents, were significantly depleted during the enzymatic oxidation of ASA by
tyrosinase to
quinone. The 50% inhibitory concentration (48 h) of ASA and
salicylic acid toward SK-MEL-28 cells were 100 micromol/l and 5.2 mmol/l, respectively. ASA at 100 micromol/l was selectively toxic toward human melanocytic SK-MEL-28, MeWo, and SK-MEL-5 and murine melanocytic B16-F0 and B16-F10
melanoma cell lines. However, ASA was not significantly toxic to human amelanotic C32
melanoma cell line, which does not express
tyrosinase enzyme, and human nonmelanoma BJ, SW-620, Saos, and PC-3 cells.
Dicoumarol, a diaphorase inhibitor, and 1-bromoheptane, a GSH depleting agent, increased ASA toxicity toward SK-MEL-28 cells indicating
quinone formation and intracellular GSH depletion played important mechanistic roles in ASA-induced
melanoma toxicity.
Ascorbic acid, a
quinone reducing agent, and GSH, an
antioxidant and
quinone trap substrate, prevented ASA cell toxicity.
Trifluoperazine, inhibitor of permeability transition pore in mitochondria, prevented ASA toxicity. ASA led to significant intracellular GSH depletion in melanocytic SK-MEL-28
melanoma cells but not in amelanotic C32
melanoma cells. ASA also led to significant
reactive oxygen species (ROS) formation in melanocytic SK-MEL-28
melanoma cells but not in amelanotic C32
melanoma cells. ROS formation was exacerbated by
dicoumarol and 1-bromoheptane in SK-MEL-28. Our investigation suggests that
quinone species, intracellular GSH depletion, ROS formation, and mitochondrial toxicity significantly contributed toward ASA selective toxicity in melanocytic SK-MEL-28
melanoma cells.