Immunohistochemical expression of ataxia telangiectasia mutated, ataxia telangiectasia mutated-Rad3-related, breast cancer type 1 susceptibility protein, mediator of DNA damage checkpoint protein 1 and meiotic recombination 11 in gastric cancer tissues. ATM: Ataxia telangiectasia mutated; ATR: Ataxia telangiectasia mutated-Rad3-related; BRCA1: Breast cancer type 1 susceptibility protein 1; MDC1: Mediator of DNA damage checkpoint protein 1; Mre11: Meiotic recombination 11. 3,3'-Diaminobenzidine staining, ×200.