We investigated whether human breast cancer cells, when cultured under hyperglycemia, are more vulnerable to DNA repair inhibitors, assessing a panel of cancer drugs that included the checkpoint kinase inhibitor AZD7762, the ATR (ataxia telangiectasia and Rad3 related) inhibitor berzosertib, the topoisomerase II inhibitor etoposide, and the PARP inhibitor olaparib. The gene discussed is ATR; the disease is cancer.