Cell Death Induced by Homoisoflavonoid Brazilin and Its Semisynthetic Derivatives 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
proapoptotic activity of brazilin and its semisynthesized methoxylated
(OMe)3 and acetylated (OAc)3 derivatives in
triple-negative MDA-MB-231, luminal A MCF7 breast cancer cell lines
and nontumorigenic MCF10A cells. We assessed cell viability, oxidative
stress, and mitochondrial integrity, and analyzed apoptotic features
using confocal microscopy, Western blot, 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 a more subtle response. In MDA-MB-231 cells,
treatment with brazilin and brazilin-(OAc)3 induced mild
apoptosis-associated features, including chromatin condensation, γH2AX
accumulation, and PARP cleavage. These effects were accompanied by
a modest increase in oxidative stress and loss of mitochondrial membrane
potential. Transcriptomic analysis revealed that in MDA-MB-231 cells
brazilin treatment regulates genes associated with endoplasmic reticulum
stress and RNA metabolism, among other categories. Only high doses
or long exposure to brazilin and brazilin-(OAc)3 affected
the nontumorigenic MCF10A cells. Notably, the methylated compound
exhibited minimal biological activity, as it did not significantly
affect cell viability across the tested cell lines and induced no
substantial transcriptional changes. Collectively, our results suggest
that brazilin and its acetylated derivative induce mitochondrial stress
and cell death in triple-negative breast cancer cells, potentially
involving endoplasmic reticulum stress pathways.