Cell Death Induced by Homoisoflavonoid Brazilin and its Semi-synthetic Derivates on MDA-MB-231 and MCF7 Breast Cancer Cell Lines

Flavonoids are naturally occurring polyphenolic compounds that have been extensively explored as scaffolds for drug development due to their diverse biological activities. Brazilin, a homoisoflavonoid with reported antitumoral properties, does not fully meet pharmaceutical criteria, and chemical modification of natural compounds is often required to enhance bioactivity and efficacy. Here, we evaluated the pro-apoptotic activity of Brazilin and its semi-synthesized methoxylated (OMe)3 and acetylated (OAc)3 derivatives in triple-negative MDA-MB-231 and luminal A MCF7 breast cancer cell lines. We assessed cell viability, proliferation, oxidative stress, and mitochondrial integrity, and analyzed apoptotic features using confocal microscopy, western blotting, and RT-qPCR. In addition, RNA sequencing was performed to characterize transcriptomic changes in MDA-MB-231 cells following treatment with unmodified Brazilin or its derivatives. Brazilin and Brazilin-(OAc)3 significantly reduced cell viability and proliferation in MDA-MB-231 cells, whereas MCF7 cells exhibited increased viability and growth in response to Brazilin-(OMe)3. In MDA-MB-231 cells, treatment with Brazilin and Brazilin-(OAc)3 induced apoptosis-associated features, including chromatin condensation, {gamma}H2AX accumulation, and PARP cleavage. These effects were accompanied by a modest increase in mitochondrial oxidative stress and loss of mitochondrial membrane potential. Notably, no cytotoxic or apoptotic features were detected in non-tumorigenic MCF10A cells. Transcriptomic analysis revealed that Brazilin treatment upregulated genes associated with endoplasmic reticulum stress, including ATF3, in MDA-MB-231 cells. Collectively, our results indicate that Brazilin and its acetylated derivative selectively induce mitochondrial stress and cell death in triple-negative breast cancer cells, potentially involving ER stress pathways.