Clinicopathological significance of ataxia-telangiectasia-mutated (ATM) kinase and ataxia telangiectasia-mutated and Rad3 related (ATR) kinase in MYC overexpressed breast cancers

Purpose: MYC transcription factor has critical roles in cell growth, proliferation, metabolism, differentiation, transformation and angiogenesis. MYC overexpression is seen in about 15% of breast cancers and linked to aggressive phenotypes. MYC overexpression also induces oxidative stress and replication stress in cells. ATM and ATR- mediated signalling is critical for MYC induced DNA damage response. Whether ATM and ATR expression influence clinical outcomes in MYC overexpressed breast cancers is unknown.Methods: We investigated ATM, ATR and MYC at the transcriptional level [Molecular Taxonomy of Breast Cancer International Consortium cohort (n=1950)] and at the protein level in the Nottingham series comprising 1650 breast tumours. We correlated ATM, ATR and MYC expression to clinicopathological features and survival outcomes.Results: In MYC over expressed tumours, high ATR or low ATM levels were associated with aggressive breast cancer features such as higher tumour grade, de-differentiation, pleomorphism, high mitotic index, high risk Nottingham Prognostic Index, triple negative and basal-like breast cancers (all adjusted p values [less than] 0.05). Tumours with low ATM or high ATR levels in conjunction with MYC overexpression also have worse overall breast cancer-specific survival (BCSS) (p value [less than] 0.05).Conclusions: We conclude that ATR/ATM directed stratification and personalisation of therapy may be feasible in MYC overexpressed breast cancer