S100A14 is a novel independent prognostic biomarker in the triple‐negative breast cancer subtype

Triple‐negative breast cancer (TNBC) represents a heterogeneous subgroup with generally poor outcome and lack of an effective targeted therapy. Prognostic or predictive biomarkers to guide treatment decisions for this group of patients are needed. To evaluate the potential of S100A14 protein as a novel biomarker in TNBC, the protein expression of S100A14 was correlated with clinical outcomes in a Pilot Sample set and a Danish cohort of predominantly TNBC patients. Kaplan‐Meier analysis identified a prognostic impact of S100A14 on disease‐free survival and overall survival, showing that tumors with high S100A14 protein expression levels were significantly correlated with poor outcome in TNBC patients (p = 0.017; p = 0.038), particularly those in the basal‐like subgroup (p = 0.006; p = 0.037). Importantly, TNBC patients with high S100A14 expression, but tumor‐negative axillary lymph nodes (N−), had equally poor outcomes as those with tumor‐positive axillary lymph nodes (N+), while TNBC/N− patients with low S100A14 expression had a significantly better disease free survival (p = 0.013). Multivariate analysis revealed that S100A14 is an independent prognostic factor for TNBC patients (p = 0.024; p = 0.05). At the cellular level, S100A14 was found to be expressed in epithelial‐like, but not in mesenchymal‐like, TNBC cells in vitro. S100A14 is an independent prognostic factor in TNBC and a novel potential therapeutic target in TNBC. What's new? Patients with triple‐negative breast cancer (TNBC) may respond very differently to therapy, despite their apparent similarities. Thus, prognostic and predictive biomarkers are needed in order to identify subgroups that will allow treatment to be individualized. In this study, the authors found that patients with lower expression of a calcium‐binding protein called S100A14 had significantly better disease‐free survival. In addition to its prognostic value, S100A14 may therefore also be a potential therapeutic target.