Nobiletin Significantly Enhances Apoptosis in MCF-7 Breast Cancer Cells: A Natural Compound with Potential to Prevent Cancer Progression

Background: Breast cancer (BC) is one of the leading causes of cancer-related death among women worldwide. Nobiletin (NOB), a natural polymethoxylated flavone found in citrus fruits, has demonstrated promising anticancer properties. However, its potential role in preventing cancer progression, particularly in BC cells, remains incompletely understood. This study aims to investigate the apoptotic effects of NOB on MCF-7 BC cells and its involvement in the regulation of apoptotic and cell cycle-related genes, highlighting its potential as a natural compound for cancer prevention. Objectives: We assess the impact of NOB on BC cell viability. Furthermore, we investigated the expression of Bax, Bcl-2, and Cyclin D1 genes, and we analyzed the mediating role of estrogen receptor alpha (ERα) in this context. Methods: MCF-7 BC cells were treated with different concentrations of NOB (25, 50, and 100 µM), and cell viability was assessed using the MTT assay. The qRT-PCR was used to measure Bax, Bcl-2, and Cyclin D1 gene expression, while Western blotting evaluated corresponding protein levels. Caspase activity assays and flow cytometry were conducted to assess apoptosis. Results: Nobiletin significantly reduced MCF-7 cell viability in a dose-dependent manner, with a maximum reduction of 74.3% at 50 µM after 24 hours (P < 0.01). The IC50 was 124.5 µM. Treatment with 50 and 100 µM of NOB for 24 hours significantly downregulated Cyclin D1 and Bcl-2 expression (1.33-and-1.20-fold reduction, respectively) and upregulated Bax expression (1.36-fold increase, P < 0.01). Flow cytometry confirmed a significant increase in apoptotic cells, especially at 100 µM, with a notable rise in annexin V-positive and propidium iodide-positive cells (P < 0.01). Conclusions: From our results, we conclude that NOB negatively affects BC cell viability and their gene expression through the estrogen receptor (ER). Based on this verdict, we present NOB as a natural potential anti-BC compound, to be further studied for its therapeutic effects.