Anti-Cancer Effects of the Ethyl Acetate Fraction From <i>Opuntia humifusa</i> on Human Triple-Negative Breast Cancer Cells

This study investigated the anti-cancer effects of the ethyl acetate fraction from <i>Opuntia humifusa</i> on human breast cancer MDA-MB-231 cells. <i>O. humifusa</i>, a cactus species capable of surviving under extreme environmental conditions, is currently being studied for its potential pharmacological properties. The MDA-MB-231 cell line is a highly invasive and metastatic model of triple-negative breast cancer (TNBC), which lacks estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. TNBCs are often clinically challenging because they generally have a poor prognosis and limited treatment options. The ethyl acetate fraction was obtained from ethanol extracts of fruit powder of <i>O. humifusa</i>. Treating MDA-MB-231 cells with ethyl acetate fraction for 48 hours reduced cell viability by more than 50% and inhibited migration demonstrated by wound healing assays. DAPI staining proved nuclear condensation and fragmentation, and flow cytometry confirmed the induction and progression of apoptosis and arrest of cell cycle at the S and G2/M phases. Western blot analysis revealed that Akt, ERK1/2, integrin β1, HIF-1α, MMP-9, MMP-7, CDK2, cyclin A2, pro-caspase-9, pro-caspase-8, pro-caspase-3, and lamin A/C were decreased in a dose-dependent manner, whereas Smac/DIABLO, cleaved caspase-9, cleaved caspase-8, and cleaved caspase-3 were increased in a concentration-dependent manner, indicating downregulation of proliferation, activation of upstream signal transduction influencing cell cycle arrest and apoptosis, deactivation of metastasis, induction of cell cycle arrest at the S and G2/M phases, and activation of intrinsic and extrinsic apoptotic pathways. These findings suggest that the ethyl acetate fraction of <i>O. humifusa</i> induces apoptosis, cell cycle arrest, and anti-metastasis as well as contributing to upstream signal transduction of anti-proliferation, apoptosis, and cell cycle arrest in human triple-negative breast cancer cells.