Programmed death 1 ligand 1 (PD-L1) is an immune regulatory molecule that limits anti-tumor immune activity. Targeting of PD-L1 and other immune checkpoint proteins has shown therapeutic activity in various tumor types. The expression of PD-L1 and its correlation with response to neoadjuvant chemotherapy in breast cancer has not been studied extensively. Our goal was to assess PD-L1 expression in a cohort of breast cancer patients treated with neoadjuvant chemotherapy.Pre-treatment biopsies from 105 breast cancer patients from Yale New Haven Hospital that subsequently received neoadjuvant chemotherapy were assessed for PD-L1 protein expression by automated quantitative analysis (AQUA) with a rabbit monoclonal antibody (E1L3N) to the cytoplasmic domain. Additionally, tumor infiltrating lymphocytes (TILs) were assessed on H&E slides.PD-L1 expression was observed in 30% of patients and it was positively associated with hormone receptor negative and triple-negative status and high levels of TILs. Both TILs and PD-L1 measured in the epithelium or stroma predicted pathological complete response (pCR) to neoadjuvant chemotherapy in univariate and multivariate analysis. However, since they are strongly associated, TILs and PD-L1 cannot both be included in a significant multivariate model.PD-L1 expression is prevalent in breast cancer, particularly hormone receptor negative and triple-negative patients, indicating a subset of patients which may benefit from immune therapy. Furthermore, PD-L1 and TILs correlate with pCR and high PD-L1 predicts pCR in multivariate analysis.
- Received July 14, 2014.
- Revision received November 23, 2014.
- Accepted December 11, 2014.
- Copyright © 2014, American Association for Cancer Research.