Molecular Imaging of PD-L1 Expression and Dynamics with the Adnectin-Based PET Tracer F-18-BMS-986192

F-18-BMS-986192, an adnectin-based human programmed cell death ligand 1 (PD-L1) tracer, was developed to noninvasively determine whole-body PD-L1 expression by PET. We evaluated the usability of F-18-BMS-986192 PET to detect different PD-L1 expression levels and therapy-induced changes in PD-L1 expression in tumors. Methods: In vitro binding assays with F-18-BMS-986192 were performed on human tumor cell lines with different total cellular and membrane PD-L1 protein expression levels. Subsequently, PET imaging was performed on immunodeficient mice xenografted with these cell lines. The mice were treated with interferon gamma (IFN gamma) intraperitoneally for 3 d or with the mitogen-activated protein kinase kinase inhibitor selumetinib by oral gavage for 24 h. Afterward, F-18-BMS-986192 was administered intravenously, followed by a 60-min dynamic PET scan. Tracer uptake was expressed as percentage injected dose per gram of tissue. Tissues were collected to evaluate ex vivo tracer biodistribution and to perform flow cytometric, Western blot, and immunohistochemical tumor analyses. Results: F-18-BMS-986192 uptake reflected PD-L1 membrane levels in tumor cell lines, and tumor tracer uptake in mice was associated with PD-L1 expression measured immunohistochemically. In vitro IFN gamma treatment increased PD-L1 expression in the tumor cell lines and caused up to a 12-fold increase in tracer binding. In vivo, IFN gamma affected neither PD-L1 tumor expression measured immunohistochemically nor F-18-BMS-986192 tumor uptake. In vitro, selumetinib downregulated cellular and membrane levels of PD-L1 in tumor cells by 50% as measured by Western blotting and flow cytometry. In mice, selumetinib lowered cellular, but not membrane, PD-L1 levels of tumors, and consequently, no treatment-induced change in F-18-BMS-986192 tumor uptake was observed. Conclusion: F-18-BMS-986192 PET imaging allows detection of membrane-expressed PD-L1 as soon as 60 min after tracer injection. The tracer can discriminate a range of tumor cell PD-L1 membrane expression levels

Immunotherapeutic options on the horizon in breast cancer treatment

It is increasingly acknowledged that breast cancer can be an immunogenic disease. Immunogenicity appears to differ between subtypes. For instance, in triple negative breast cancer (TNBC) and HER2-positive breast cancer tumor infiltrating lymphocytes (TILs) are prognostic and predictive for response to chemotherapy containing anthracyclines, but in other subtypes they are not. Preclinical evidence suggests important immune based mechanisms of conventional chemotherapeutics, in particular anthracyclines. Early clinical studies with monoclonal antibodies targeting programmed death protein 1, programmed death-ligand 1 and cytotoxic T-lymphocyte-associated antigen 4 have shown anti-tumor efficacy. Tumor vaccines designed to increase the body's own anti-tumor immunity have shown an increased anti-tumor immunity, however clinical efficacy has not yet been demonstrated. Novel strategies will likely follow. In light of the increased interest in immune modulation, this review focuses on predictive immune-based biomarkers, immune-mediated effects from conventional therapies, as well as recent results and ongoing studies concerning immunotherapies in breast cancer. (C) 2015 Elsevier Inc. All rights reserved

MAPK pathway activity plays a key role in PD-L1 expression of lung adenocarcinoma cells

Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) have improved the survival of patients with non-small cell lung cancer (NSCLC). Still, many patients do not respond to these inhibitors. PD-L1 (CD274) expression, one of the factors that influences the efficacy of immune checkpoint inhibitors, is dynamic. Here, we studied the regulation of PD-L1 expression in NSCLC without targetable genetic alterations in EGFR, ALK, BRAF, ROS1, MET, ERBB2 and RET. Analysis of RNA sequencing data from these NSCLCs revealed that inferred IFN gamma, EGFR and MAPK signaling correlated with CD274 gene expression in lung adenocarcinoma. In a representative lung adenocarcinoma cell line panel, stimulation with EGF or IFN gamma increased CD274 mRNA and PD-L1 protein and membrane levels, which were further enhanced by combining EGF and IFN gamma. Similarly, tumor cell PD-L1 membrane levels increased after coculture with activated peripheral blood mononuclear cells. Inhibition of the MAPK pathway, using EGFR inhibitors cetuximab and erlotinib or the MEK 1 and 2 inhibitor selumetinib, prevented EGF- and IFN gamma-induced CD274 mRNA and PD-L1 protein and membrane upregulation, but had no effect on IFN gamma-induced MHC-I upregulation. Interestingly, although IFN gamma increases transcriptional activity of CD274, MAPK signaling also increased stabilization of CD274 mRNA. In conclusion, MAPK pathway activity plays a key role in EGF- and IFN gamma-induced PD-L1 expression in lung adenocarcinoma without targetable genetic alterations and may present a target to improve the efficacy of immunotherapy. (c) 2019 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland