A prime example is a novel finding that triple-negative breast cancers, where genomic stratification has failed to identify biomarkers for this hard to treat aggressive subtype6,55,62, are clearly separated into two major groups based on their dominant malignant cell type (basal-like CC B1 vs mesenchymal-like CCs M1-3), with rather distinct drug-response profiles to conventional chemotherapy (cisplatin, epirubicin, camptothecin) or to drugs targeting the DNA damage response (AZD1775- Wee1 inhibitor, AZD7762- CHEK1/2 inhibitor, KU-55933- ATM inhibitor). The gene discussed is CHEK1; the disease is triple-negative breast carcinoma.