Abstract 4286: Tissue-specific preference for ATM or ATR pathway activation determines DNA damage outcome and provides insights in cancer predisposition
Authors: Jaarsveld Marijn T. Van , Deng Difan , Wiemer Erik A. , Zi Zhike 
Published: August 2018

Abstract
The DNA damage response (DDR) is an elaborate signaling network that protects against mutations and genomic instability. Despite its importance in preventing carcinogenesis, certain mutations in the DDR (e.g. BRCA1/2) predispose for specific cancers only. An explanation for this could be that the DDR is regulated differently across tissues; however, systematic analyses of the response to DNA damage in healthy human cells have not been carried out.
We analyzed proteomic changes in response to single- and double strand DNA damage in non-immortalized human primary cells and related them to cell outcome. Primary breast and lung cells were treated with cisplatin (single-strand damage) or doxorubicin (double-strand breaks) at doses that caused a similar amount of DNA damage. Cell outcomes that were studied were apoptosis and cell cycle progression. Protein dynamics of 366 proteins were assessed using protein arrays and quantitative western blots. Inhibitors and an ODE-based mathematical model were used to determine the network topology and link it to outcome.
Treatment of primary breast and lung epithelial cells with an equal amount of damage resulted in different viabilities. Primary mammary cells showed higher levels of apoptosis after single-strand damage, primary airway cells were more sensitive to double-strand breaks. The difference in outcome was reflected in distinct protein dynamics, including DNA repair pathways. Surprisingly, these differences originated at the earliest level of DNA damage detection by ATM and ATR. We demonstrated that differential activation of ATM and ATR pathways in breast and lung cells affects p53 and p21 dynamics and leads to distinct outcomes. We were able to identify key network nodes, providing new insights into the regulation of p53 and p21 and their relation to cell outcome. p53 and p21 dynamics are also linked to regulation of the cell cycle. In line with this, we found that cell cycle progression under normal conditions and after DNA damage is different. Importantly, we show that the double-strand break pathway plays a larger role in cell cycle control in breast cells than in lung cells. Since cell cycle checkpoints are a safeguard against genomic instability, differential regulation may affect cancer predisposition in a cell-type specific manner. Our work may provide an explanation for the fact that certain mutations in the DSB-repair pathway predispose for breast cancer, but not for lung cancer.
In summary, we show that primary breast and lung cells activate distinct programs in response to equal doses of DNA damage, resulting in different p53 and p21 dynamics and, consequently, diverse outcomes. In addition, this work sheds light on the tissue-specific cancer predisposition of mutated DNA repair genes and may be the basis for further studies.
Citation Format: Marijn T. Van Jaarsveld, Difan Deng, Erik A. Wiemer, Zhike Zi. Tissue-specific preference for ATM or ATR pathway activation determines DNA damage outcome and provides insights in cancer predisposition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4286.