Isoliquiritigenin Induces Apoptosis via ROS-Mediated Inhibition of p38/mTOR/STAT3 Pathway in Human Melanoma Cells

Isoliquiritigenin (ISL), a phenolic compound derived from licorice, exhibits various biological activities, including anti-inflammatory, anti-viral, anti-tumor, and antioxidant effects. However, the molecular mechanisms underlying its anti-cancer effects are not well understood in SK-MEL-28 melanoma cells. Melanoma, a highly aggressive and treatment-resistant cancer, remains a significant health challenge. This study investigates the anti-cancer effects of ISL, focusing on identifying reactive oxygen species (ROS)-mediated apoptosis mechanisms on SK-MEL-28 melanoma cells. Our results show that ISL treatment induces apoptosis in SK-MEL-28 cells, as evidenced by the cleavage of caspase-9, -7, -3, and PARP. ISL increased Bax expression, decreased Bcl-2 expression, and promoted cytochrome C release into the cytosol. ISL also reduced the expression of cell cycle markers, including cyclin D1, D3, and survivin. Notably, ISL treatment markedly increased intracellular ROS levels and pretreatment with N-acetyl cysteine, a ROS scavenger, abrogated the ISL-induced inhibition of the p38/mTOR/STAT3 pathway and prevented apoptosis. Moreover, ISL significantly diminished the constitutive phosphorylation of mTOR and STAT3 in SK-MEL-28 cells by blocking the phosphorylation of p38 MAPK, an upstream kinase of mTOR. Pharmacological inhibition of mTOR attenuated the STAT3 signaling, indicating that mTOR acts as an upstream kinase of STAT3 in these cells. Collectively, these findings demonstrate that ISL inhibits SK-MEL-28 cell growth by downregulating cell survival proteins and inducing apoptosis through ROS generation.