Furthermore, when DLL1 expression was compared with DMFS in four different molecular subtypes of breast cancer, higher DLL1 levels strongly correlated with poor patient outcome in the ERα+ Luminal A subtype, but not in the ERαlow subtypes such as luminal B, TNBC/basal, and HER2 (Supplementary Fig. S1B-E). The gene discussed is ESR1; the disease is breast cancer.