Selective cytotoxicity of butyrate highlights its potential as a targeted anti-cancer agent

Background: Within the marked heterogeneity of breast cancer, the triple-negative subtype stands out for its highly aggressive nature. Its absence of hormonal receptors prevents the use of targeted treatments, pointing the need to uncover improved therapeutic strategies. Nevertheless, recent studies have recognized butyrate as a potential agent for intervention. Butyrate is a microbial-derived short chain fatty acid that exerts anti-cancer effects. Our preliminary data showed that butyrate treatment can significantly reduce cell viability, migration, and proliferation at concentrations of 5 mM in the triple-negative cell line MDA-MB-231. While butyrate has proven its potential as a treatment option, its safety towards healthy mammary cells remains unclear. Therefore, in this study, we evaluated the effects of butyrate in a non-tumorigenic mammary epithelial cell model (MCF10A). Methods: Cells were cultured in 1:1 DMEM/F12 supplemented with 20ng/mL EGF, 0.5 ug/mL hydrocortisone, 10ug/mL insulin, 100ng/mL cholera toxin, and 5% horse serum. Cell viability was measured using AlamarBlue assay, and butyrate treatment was given in serial dilutions (1:2) starting at 800 mM for 24, 48, and 72 hours. The half-minimal inhibitory values (IC-50) were assessed via fluorescence (590nm). Cell proliferation was evaluated by treating MCF10A with 5mM of butyrate and then quantifying for 24, 48, and 72 hours using an automated cell counter. Results: No IC-50 was reached, yet there was a reduction in cell viability with concentrations from 100 mM and higher. In fact, MCF10A cells continued to be viable at 24, 48, and 72 hours at 5mM. There was no significant change in cell proliferation at 5mM in all time points. Conclusions: These results suggest that butyrate reduced viability in triple-negative breast cancer cells while having no meaningful effect on the viability of MCF10A cell line, indicating a selective cytotoxic response. Proliferation results show that MCF10A presents no significant change in cell growth upon butyrate exposure in comparison to untreated controls. These results show the potential of butyrate as a selective anti-cancer agent and raise interest in the mechanism of which butyrate modulates cancer cell behavior.