Fig. 1

DLL1 expression is higher in luminal (non-TNBC) breast cancer patients and is associated with poor patient survival. a, b Representative IHC images (a) and calculated H-score (b) show higher DLL1 protein levels in non-TNBC (n = 60) compared to tumor-adjacent normal tissue (n = 23) and TNBC (n = 58) patient tumors. The H-Score was calculated by multiplying intensity with abundance. Negative control is tumor tissue stained with anti-IgG antibody showing no nonspecific staining. c, d Kaplan–Meier (KM) plots show poor distant metastasis-free survival (DMFS) of breast cancer patients by DLL1 expression status (DLL1^high or DLL1^low) in ER⁺ (c), ER⁻ (d). n = 965 ER⁺ patients (c) and n = 430 ER⁻ (d) patients were used to make KM-plots. e Representative IHC images of non-TNBC patient breast tumors show DLL1^high and DLL1^low protein expression respectively. f KM plot shows poor patient survival of patients with high levels of DLL1 protein compared to patients with low levels of DLL1 protein. H-score was evaluated to stratify patients into DLL1 high and low expressers based on the IHC with DLL1 antibody on the non-TNBC patient breast tumors. n = 32 non-TNBC samples were used with overall survival data. Samples were stratified into DLL1^low (n = 12) and DLL1^high (n = 20) groups for KM plot analysis. b Mann−Whitney U test and c, d, f Log-rank test was used to calculate p values. b Data are presented as the mean ± SEM. ***p < 0.001 and # nonsignificant. Scale bars, 40 µm (a, e)