Hormone-dependent estrogen receptor positive (ER+) breast cancers generally respond well to anti-estrogen therapy. Unfortunately, hormone-independent estrogen receptor negative (ER-) breast cancers are aggressive, respond poorly to current treatments and have a poor prognosis. New approaches and targets are needed for the prevention and treatment of ER- breast cancer. The NF-κB signaling pathway is strongly implicated in ER- tumor genesis, constituting a possible target for treatment. Hydrogen sulfide-releasing aspirin (HS-ASA), a novel and safer derivative of aspirin, has shown promise as an anti-cancer agent. We examined the growth inhibitory effect of HS-ASA via alterations in cell proliferation, cell cycle phase transitions, and apoptosis, using MDA-MB-231 cells as a model of triple negative breast cancer. Tumor xenografts in mice, representing human ER- breast cancer, were evaluated for reduction in tumor size, followed by immunohistochemical analysis for proliferation, apoptosis and expression of NF-κB. HS-ASA suppressed the growth of MDA-MB-231 cells by induction of G(0)/G(1) arrest and apoptosis, down-regulation of NF-κB, reduction of thioredoxin reductase activity, and increased levels reactive oxygen species. Tumor xenografts in mice, were significantly reduced in volume and mass by HS-ASA treatment. The decrease in tumor mass was associated with inhibition of cell proliferation, induction of apoptosis and decrease in NF-κB levels in vivo. HS-ASA has anti-cancer potential against ER- breast cancer and merits further study.
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