Objective To investigate the effect and potential mechanism of cadmium (Cd) on the proliferation of human breast cancer MCF-7 cells and the expression of estrogen receptor (ER).
Methods A and B strains of MCF-7 cells were treated with 17β-estradiol (hereinafter referred to as estrogen) at 1×10-6, 1×10-7, 1×10-8, 1×10-9, 1×10-10, and 1×10-11 mol/L, respectively, for 4 d. CCK8 assay was employed to detect a susceptible MCF-7 cell strain and to identify the concentration of estrogen promoting maximum cell proliferation. Then, the susceptible MCF-7 cell strain was treated with 1×10-6, 1×10-7, 1×10-8, 1×10-9, 1×10-10, and 1×10-11 mol/L cadmium solution, respectively, to identify the concentration of cadmium promoting maximum cell proliferation. We set a negative control group (medium without estrogen), an experimental group (1×10-8 mol/L cadmium), and a positive control group (1×10-9 mol/L estrogen) to evaluate colony formation ability by clonogenicity assay. Additionally, we set an experimental inhibitor group1×10-8 mol/L Cd+1×10-7 mol/L ER antagonist (ICI182780) and a positive inhibitor group (1×10-9 mol/L estrogen+1×10-7 mol/L ER antagonist) to detect cell proliferation, the ratio of S phase cells, and the expression level of ER by CCK8, flow cytometry, and Western blot, respectively.
Results The MCF-7 cells of strain B were estrogen sensitive cells, and the 1×10-9 mol/L estrogen treatment induced the maximum cell proliferation(203.55±36.65)%. Compared with the negative control group (100%), 1×10-8-1×10-10 mol/L cadmium significantly promoted proliferation of MCF-7 cells(163.78±31.90)%-(176.88±10.06)% (P < 0.001). Besides, 1×10-8 mol/L cadmium treatment promoted colony formation of MCF-7 cells (P < 0.05), increased the ratio of S phase cells (P < 0.001), and elevated ER protein expression level (P < 0.001). Compare with the experimental group, ER antagonist suppressed the effect of cadmium on proliferation of MCF-7 cellsfrom (135.17±23.96)% to (107.66±7.64)% (P < 0.01), reduced the ratio of S phase cellsfrom (24.17±0.53)% to (12.36±0.43)% (P < 0.001), and down-regulated ER protein expression levelfrom (56.19±3.67)% to (38.84±1.04)% (P < 0.05).
Conclusion Cadmium can promote proliferation and ER expression of breast cancer MCF-7 cells, and the effect can be inhibited by ER antagonist, indicating estrogen-like effect of cadmium.
DownLoad: