Abstract 1186: Differences in the levels, localization and DNA binding of p53 in breast cancer cell lines

Abstract

Abstract Mutations in the p53 tumor suppressor affect protein accumulation, localization and DNA binding. We undertook to determine these properties of p53 in breast cancer cells and to see how those attributes change following oxidative stress. We analyzed the p53 in 8 different breast cancer cell lines, with either wild-type or mutant p53 protein. By ELISA and western blots, we found that the levels of the p53 protein were generally low for cells carrying wild-type protein and high in cells having a mutation in the TP53 gene. This was contrasted to the case in the HCC2157 cell line which has wild-type p53 but accumulates the protein to high levels. Using biotinylated DNA and streptavidin magnetic beads, we found that wild-type p53 protein from MCF-7 and ZR-75-1 cells binds with different affinity to 12 gene sequences covering several pathways regulated by p53. Treatment of MCF-7 cells with H2O2 caused an increase in this binding affinity. The p53 from the HCC2157 cells and all of the mutant p53 proteins had minimal to weak binding to these sequences even after treatment with H2O2. We also analyzed the phosphorylation of serine 15 on p53 in 4 of the cell lines. The p53 protein from the HCC2157 cells and two other cell lines showed phosphorylated protein at this site, but we found no correlation between that modification and the levels, localization, or binding affinity of the protein. From this and other work, it appears that the mutation status of the TP53 gene alone can not predict the activity of this tumor suppressor since cell lines with the same genetic information do not show the same properties of this protein. We argue that the analysis of DNA binding or transcription activity must be done in order to correlate the functionality of p53 with clinical outcome in tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1186. doi:1538-7445.AM2012-1186