Effects of Luteolin on Breast Cancer Cell Survival and Response to Ionizing Radiation

This study investigated the antiproliferative effects of luteolin (LUT) and its potential to modify the response of breast cancer (BC) cells to ionizing radiation (IR). LUT effects alone or with IR were evaluated in MCF-7 and MDA-MB-231 cells using clonogenic and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Apoptosis and cell cycle distribution were assessed by flow cytometry, while reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blotting were used to determine apoptosis-related gene and protein expression. LUT reduced the clonogenic survival and metabolic activity in both BC cell lines. In MCF-7 cells, combined LUT and IR treatment produced a greater reduction in metabolic activity and clonogenic survival than either treatment alone, whereas no comparable effect was observed in MDA-MB-231 cells. LUT induced apoptosis in both cell lines. Cell cycle analysis indicated G2/M phase accumulation, reaching statistical significance in MDA-MB-231 cells. In MCF-7 cells, LUT decreased BCL2 and MCL1 gene expression, with a further reduction following combined LUT and IR treatment. Consistently, BCL-2 protein levels were reduced in MCF-7 cells. In MDA-MB-231 cells, LUT modulated the expression of selected anti-apoptotic genes. Overall, these findings demonstrate cell line-dependent effects of LUT and suggest that its ability to modify the response to IR may depend on the molecular characteristics of BC cells.