ABSTRACT
<p><b>OBJECTIVE</b>The functional characters of MCF7 and HCC1937 cell lines were compared through the activity of BRCA1 and p53 following DNA damage in order to provide more research evidence for the related studies in both breast cancer cell lines.</p><p><b>METHODS</b>The protein level of BRCA1 and p53 in two breast cancer cell lines and the protein level of BRCA1 in MCF7, HCC1937 and HCC1937 wtBRCA1 breast cancer cell lines treated with 10Gy after 1 h, 4 h or 8 h were detected by western blotting analysis. The distribution and foci formation of BRCA1 in the cells were observed through immunostaining assay and the percentage of BRCA1 or Rad51 foci formation after ionizing radiation was calculated. Cell cycle profiling was analyzed using flow cytometry.</p><p><b>RESULTS</b>Most of BRCA1 and p53 localized in nucleus, and both proteins responded to DNA damage in MCF7 cells. In MCF7 cells,BRCA1 and Rad51 foci formation respectively increased to (59.40 ± 3.66)% from (11.80 ± 3.51)% (t = 16.26, P < 0.05) and (73.90 ± 8.66) % from (16.70 ± 3.76) % (t = 10.49, P < 0.05) after 10 Gy 8 h ; p53 and p21 protein level was further separately induced and enhanced to (82.54 ± 1.04) from (23.75 ± 0.51) (t = 87.90, P < 0.05) and (90.95 ± 1.13) from (50.19 ± 0.89) ( t = 49.11, P < 0.05) after 10 Gy 8 h; and the cells were accumulated in G1 phase. In contrast to MCF7, in HCC1937 cell line, both of BRCA1 and p53 were defective in nucleus since both proteins were mutated; in response to DNA damage, BRCA1 foci formation was not found, p53 and p21 was not induced; there was no cell accumulation in both of G1-S and G2-M phases. However, after complementation of wild-type BRCA1 in HCC1937 cells, DNA damage-induced Rad51 foci formation increased to (61.70 ± 4.03) % from (6.22 ± 2.27) % (t = 20.78, P < 0.05) and accumulation of cells in G2-M phase was also restored after 10 Gy 8h , which was similar to that of in MCF7 cells.</p><p><b>CONCLUSIONS</b>We have identified that BRCA1 and p53 have dramatically different functions in MCF7 and HCC1937 cell lines in response to DNA damage.</p>
