Programmed death 1 ligand 1 (PD-L1) is an immune regulatory molecule that limits antitumor 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 of PD-L1. Additionally, tumor-infiltrating lymphocytes (TIL) 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 pathologic 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 that may benefit from immune therapy. Furthermore, PD-L1 and TILs correlate with pCR and high PD-L1 predicts pCR in multivariate analysis.

Purpose: To deepen our understanding of mutant ROS1 expression, localization, and frequency in nonsmall cell lung cancer (NSCLC), we developed a highly specific and sensitive immunohistochemistry (IHC)-based assay that is useful for the detection of wild-type and mutant ROS1.Experimental Design: We analyzed 556 tumors with the ROS1 D4D6 rabbit monoclonal antibody IHC assay to assess ROS1 expression levels and localization. A subset of tumors was analyzed by FISH to determine the percentage of these tumors harboring ROS1 translocations. Using specific and sensitive IHC assays, we analyzed the expression of anaplastic lymphoma kinase (ALK), EGFR L858R, and EGFR E746-A750del mutations in a subset of lung tumors, including those expressing ROS1.Results: In our NSCLC cohort of Chinese patients, we identified 9 (1.6%) tumors expressing ROS1 and 22 (4.0%) tumors expressing ALK. FISH identified tumors with ALK or ROS1 rearrangements, and IHC alone was capable of detecting all cases with ALK and ROS1 rearrangements. ROS1 fusion partners were determined by reverse transcriptase PCR identifying CD74-ROS1, SLC34A2-ROS1, and FIG-ROS1 fusions. Some of the ALK and ROS1 rearranged tumors may also harbor coexisting EGFR mutations.Conclusions: NSCLC tumors with ROS1 rearrangements are uncommon in the Chinese population and represent a distinct entity of carcinomas. The ROS1 IHC assay described here is a valuable tool for identifying patients expressing mutant ROS1 and could be routinely applied in clinical practice to detect lung cancers that may be responsive to targeted therapies.

IL-33 amplifies inflammation in both IgE-independent and IgE-dependent responses.