Genistein Enhances the Radiosensitivity of Breast Cancer Cells via G2/M Cell Cycle Arrest and Apoptosis

Abstract

Abstract:The aim of the present study was to investigate the radiosensitizing effect of genistein, and the corresponding mechanisms of action on breast cancer cells with different estrogen receptor (ER) status. Human breast cancer cell lines such as MCF-7 (ER-positive, harboring wild-type p53) and MDA-MB-231 (ER-negative, harboring mutant p53) were irradiated with X-rays in the presence or absence of genistein. Cell survival, DNA damage and repair, cell cycle distribution, cell apoptosis, expression of proteins related to G 2 /M cell cycle checkpoint and apoptosis were measured with colony formation assays, immunohistochemistry, flow cytometry and western blot analysis, respectively. Genistein showed relatively weak toxicity to both cell lines at concentrations in the range of 5-20 μM. Using the dosage of 10 μM genistein, the sensitizer enhancement ratios after exposure to X-rays at a 10% cell survival (IC 10 ) were 1.43 for MCF-7 and 1.36 for MDA-MB-231 cells, respectively. Significantly increased DNA damages, arrested cells at G 2 /M phase, decreased homologous recombination repair protein Rad51 foci formation and enhanced apoptotic rates were observed in both cell lines treated by genistein combined with X-rays compared with the irradiation alone. The combined treatment obviously up-regulated the phosphorylation of ATM, Chk2, Cdc25c and Cdc2, leading to permanent G 2 /M phase OPEN ACCESSMolecules 2013, 18 13201 arrest, and up-regulated Bax and p73, down-regulated Bcl-2, finally induced mitochondriamediated apoptosis in both cell lines. These results suggest that genistein induces G 2 /M arrest by the activation of the ATM/Chk2/Cdc25C/Cdc2 checkpoint pathway and ultimately enhances the radiosensitivity of both ER+ and ER-breast cancer cells through a mitochondria-mediated apoptosis pathway.

Long Term, Low Dose Genistein decreases Stem Cell Populations and Sensitizes Inflammatory Breast Cancer Cell Lines to Radiation

“…Previous studies have shown micromolar doses of genistein increase radiation induced cell death in non-inflammatory breast cancer cell lines by induced growth arrest and accumulation of cells in the most radiosensitive phase of the cell cycle. 10 Our data suggest that high dose genistein may act on inflammatory breast cancer cells in a similar matter, as growth arrest was detected after treatment with micromolar doses. However, this mechanism does not explain the radiosensitizing effect of long term low dose genistein as this had a minimal effect on growth of the total population of cancer cells.…”

“…8 While genistein has been reported to have a radioprotective effect on normal tissues, 9 treatment of non-inflammatory breast cancer cells with high doses (µM range) of genistein has been shown to increase radiation induced death through modulation of cell cycle and reduced expression of DNA repair proteins. 10 Although treatment of cancer cells with high doses of genistein may have a growth inhibitory effect, dietary intake may result in long term exposure to much lower doses. The effect of chronic exposure to low doses of genistein is unclear.…”

Radioprotective effects of genistein on HL-7702 cells via the inhibition of apoptosis and DNA damage

“…Another study demonstrated that 10 μM of GEN increased lowdose hyper-radiosensitivity in LNCaP prostate cancer cells [52]. Liu et al [53] showed that the apoptosis rates of MCF-7 cells and MDA-MB-231 cells increased when they were incubated with 5 μM of GEN plus 4 Gy X-irradiation, this ability was enhanced with the increasing GEN concentration to 20 μM. Unfortunately, the radio-sensitizing mechanisms of high dose of GEN remain unclear.…”

Disturbance of redox status enhances radiosensitivity of hepatocellular carcinoma

“…Briefly, approximately 1 × 10 6 cells per experimental condition were harvested, washed with cold PBS twice, and resuspended with 400 μL binding buffer. After adding 5 μL of Annexin V-FITC solution and 10 μL of PI solution, the cells were incubated for 15 min at room temperature in the dark [32]. After the incubation, 10,000 cells were analyzed with the flow cytometer (Becton Dickinson).…”