Licochalcone A Inhibits Melanoma Cell Survival by Suppressing HSP75 (TRAP1) and Disrupting Cellular Redox and Energy Homeostasis

Heat shock protein 75(HSP75), a mitochondrial chaperone of the HSP90 family, sustains tumor cell survival by restraining oxidative phosphorylation, favoring aerobic glycolysis, and limiting mitochondrial ROS to preserve redox homeostasis. Although Licochalcone A (LCA), a flavonoid isolated from licorice root, displays anticancer activity across diverse tumors, whether HSP75 suppression contributes to its anti-melanoma effects remains undefined. This study assessed HSP75 expression in melanoma and evaluated the anti-melanoma efficacy of LCA. Expression of HSP75 was compared between melanoma and normal skin specimens by Western blotting. G361 melanoma cells were exposed to LCA, after which HSP75 expression, cell viability (MTT and trypan blue assays), intracellular ROS, the GSH/GSSG balance, ATP-associated luminescence, AMPK phosphorylation, MMP2, and apoptosis-related proteins were examined. HSP75 was also silenced by siRNA in normal melanocytes (HEMn-MP) and G361 cells, alone or combined with LCA treatment, with HSP75, p-AMPK, MMP2, cleaved PARP, and cleaved caspase-3 assessed by Western blotting. Melanoma tissue showed elevated HSP75 relative to normal tissue. LCA reduced HSP75 expression and viability while raising ROS, shifting the GSH/GSSG ratio toward oxidative stress, and reducing ATP-associated luminescence. AMPK phosphorylation rose, MMP2 declined, and pro-apoptotic markers (Bax, cleaved caspase-3, cleaved PARP) increased. HSP75 knockdown alone reproduced the LCA-induced changes in ATP-associated luminescence, p-AMPK, cleaved PARP, cleaved caspase-3, and MMP2, and combined knockdown with LCA further enhanced these changes in G361 cells, which were largely attenuated in normal HEMn-MP melanocytes. LCA suppresses melanoma cell survival by inducing cellular oxidative stress, reducing ATP-associated luminescence, and promoting apoptosis, with HSP75 suppression contributing to the ATP/AMPK and apoptotic responses. These findings support further evaluation of LCA and HSP75 in melanoma.