Melanoma is a lethal form of skin cancer with rising global incidence. However, limited treatment options are available for advanced melanoma and this is further compounded by the development of resistance toward existing drugs. Panduratin A (PA), a cyclohexanyl chalcone found in Boesenbergia rotunda, was investigated for its cytotoxic potentials against human malignant melanoma A375 cells. Our initial findings revealed that mitochondrion is the primary acting site of PA on A375 cancer cells and the cytotoxic mechanisms of PA were further investigated using a temporal quantitative proteomics approach by iTRAQ 2D-LC-MS/MS. Comprehensive proteomics analysis identified 296 proteins that were significantly deregulated in PA-treated A375 cells and revealed the involvement of mitochondrial oxidative phosphorylation, secretory and ER stress pathway, and apoptosis. We further confirmed that the PA-induced apoptosis was mediated by prolonged ER stress at least in part via the PERK/eIF2α/ATF4/CHOP pathway. Pretreatment with cycloheximide, an ER stress inhibitor rescued PA-induced cell death, which was accompanied by the suppression of ER-stress-related HSPA5 and CHOP proteins. The present study provides comprehensive mechanistic insights into the cytotoxic mechanisms of PA.
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