Discovery of a novel cinnamoyl piperazinyl alepterolic acid hybrid as a TrxR1 inhibitor for inducing ROS/ER stress-mediated apoptosis in breast cancer

Targeting thioredoxin reductase 1 (TrxR1) to induce reactive oxygen species (ROS)-mediated apoptosis represents a promising anticancer strategy. However, whether TrxR1-targeted therapy holds broad-spectrum antitumor promise for breast cancer remains to be determined. Alepterolic acid is an attractive natural scaffold for drug development, yet its therapeutic potential is hampered by low potency and an undefined molecular target profile. In this work, a novel series of cinnamoyl piperazinyl alepterolic acid hybrids containing the Michael acceptor scaffolds were designed and synthesized via molecular hybridization, and their anti-breast cancer effects and TrxR1 inhibitory activity were evaluated. Among these compounds, 6m displayed the strongest antiproliferative activity against diverse breast cancer subtypes, including triple-negative breast cancer (TNBC). Importantly, 6m exhibited low cytotoxicity toward normal human breast epithelial MCF-10A cells (IC50 = 26.79 ± 0.24 μM), with a selectivity index (SI) exceeding 10 for each of the breast cancer cell lines tested. Mechanistic exploration validated that 6m directly targets TrxR1, elevating intracellular ROS, inducing ER stress, and activating caspase-dependent apoptosis. In vivo xenograft experiments further demonstrated that 6m significantly inhibited tumor growth. This study identifies 6m as a promising anti-breast cancer agent and provides novel insights into TrxR1-based targeted therapy strategies for breast cancer.