Quercetin (QUE) belonging to the flavonoid class is a common phytochemical present in the daily diet of some individuals. Quercetin is an important source of free radical scavengers. This property makes this flavonoid a reliable antioxidant with the following properties: anti-inflammatory, anti-diabetic, antimicrobial and anti-carcinogenic. Sodium butyrate (NaBu) acts as a histone deacetylase inhibitor (HDACi) and is known to regulate apoptosis in cancer cells. Combining natural flavonoids such as QUE with different substances may synergistically enhance their anti-carcinogenic capacity. Thus, the aim of this study was to examine the combined treatment effects of QUE and NaBu in hormone-sensitive breast cancer cells in vitro. MCF-7 breast cancer cells were treated with QUE alone, NaBu alone, as well as QUE and NaBu combined to determine the following: cell proliferation, levels of protein annexin A5 (ANXA5) and reactive oxygen species (ROS), mRNA protein expression, as well as cell and nuclear morphology. Data demonstrated that either QUE or NaBu alone inhibited cell proliferation, and reduced levels protein ANXA5, ROS and mRNA protein expression, The combination of QUE and NaBu produced a significant synergistic inhibitory effect compared to treatment groups of QUE or NaBu alone. In conclusion, our findings showed that the combination treatment of QUE and NaBu may constitute a promising therapeutic approach to breast cancer treatment but this needs further molecular and in vivo investigations.

Background: Sodium butyrate (NaBu), a short-chain fatty acid, modulates global gene expression through histone deacetylase (HDAC) inhibition, suppressing proliferation and inducing apoptosis in various cancers. Rutin (RUT), a polyphenolic flavonoid found in many plants, exhibits notable anticancer properties. Combining chemotherapeutic agents with natural polyphenols represents a promising strategy for cancer therapy. This study aims to evaluate, for the first time, the potential effects of NaBu and RUT combination therapy on metastatic castration-resistant prostate cancer (mCRPC) cells. Methods: PC-3 cells were treated with varying concentrations of NaBu, RUT, and their combinations. Cell viability was assessed using the WST-1 assay. Based on combination index values, selected treatments were further analyzed for apoptosis (Annexin V assay), intracellular reactive oxygen species (ROS) production, mRNA expression levels, and changes in cell and nuclear morphology. Results: The combined treatment of NaBu and RUT significantly reduced cell viability compared to individual treatments. Enhanced apoptotic induction and elevated ROS levels were observed in combination-treated cells, alongside notable changes in cellular and nuclear morphology and mRNA expression levels. Conclusions: NaBu and RUT combination therapy exhibits a synergistic anticancer effect in mCRPC cells by inhibiting cell viability, inducing apoptosis, and increasing ROS production. These findings suggest a promising therapeutic approach that warrants further investigation to elucidate the underlying molecular mechanisms and assess its potential in preclinical and clinical settings.