Savreet Aujla1, Christian Aloe1, Amanda Vannitamby1, Shona Hendry2, Kanishka Rangamuwa3, Hao Wang1, Ross Vlahos1, Stavros Selemidis1, Tracy Leong4, Daniel Steinfort5, Steven Bozinovski6. 1. School of Health & Biomedical Sciences, RMIT University, Bundoora, Australia. 2. Department of Anatomical Pathology, St Vincent's Hospital, Melbourne, Australia. 3. Department of Respiratory Medicine & Sleep Medicine, Royal Melbourne Hospital, Melbourne, Australia. 4. Department of Respiratory Medicine & Sleep Medicine, Austin Health, Heidelberg, Australia; The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia. 5. Department of Respiratory Medicine & Sleep Medicine, Royal Melbourne Hospital, Melbourne, Australia; Faculty of Medicine, University of Melbourne, Parkville, Australia. 6. School of Health & Biomedical Sciences, RMIT University, Bundoora, Australia. Electronic address: steven.bozinovski@rmit.edu.au.
Abstract
INTRODUCTION: Programmed death-ligand 1 (PD-L1) copy number gains may be predictive of clinical response to immunotherapy in NSCLC. This study investigated PD-L1 copy number variations in tumor resection and bronchoscopy biopsies and its relationship with PD-L1 tumor cell staining and inflammatory gene expression. METHODS: PD-L1 gene copy number and mRNA expression were evaluated by real-time polymerase chain reaction in surgically resected NSCLC tumor biopsies (n = 87) and control biopsies (n = 20). A second cohort (n = 15) of bronchoscopy-derived tumor biopsies was analyzed, including multiple biopsies from the same patient across different anatomical sites. RESULTS: PD-L1 mRNA levels strongly correlated with PD-L1 tumor staining (r = 0.55, p < 0.0001). Interferon-γ mRNA expression associated with PD-L1 immune cell staining, but not PD-L1 tumor cell staining. In contrast, PD-L1 copy number positively associated PD-L1 tumor staining, but not PD-L1 immune cell staining. PD-L1 copy number analysis detected loss (15 of 87 = 17%) and gain (5 of 87 = 7%) of copy number. Tumors with low PD-L1 copy number expressed significantly reduced levels of inflammatory (interferon-γ, interleukin [IL]-6, IL-1β, MMP-9) and immunosuppressive (IL-10, transforming growth factor β) mediators. Analysis of bronchoscopy-derived biopsies revealed low heterogeneity in copy number values across different anatomical sites, in contrast to more variable PD-L1 mRNA expression. CONCLUSIONS: Low PD-L1 copy number tumors display reduced PD-L1 expression, reduced PD-L1 tumor cell staining, and an immunologic cold tumor microenvironment. Because PD-L1 copy number values are highly stable across different tumor regions, its evaluation may represent a robust and complimentary biomarker for predicting response to immunotherapy, where low copy number may predict lack of response.
INTRODUCTION: Programmed death-ligand 1 (PD-L1) copy number gains may be predictive of clinical response to immunotherapy in NSCLC. This study investigated PD-L1 copy number variations in tumor resection and bronchoscopy biopsies and its relationship with PD-L1 tumor cell staining and inflammatory gene expression. METHODS: PD-L1 gene copy number and mRNA expression were evaluated by real-time polymerase chain reaction in surgically resected NSCLC tumor biopsies (n = 87) and control biopsies (n = 20). A second cohort (n = 15) of bronchoscopy-derived tumor biopsies was analyzed, including multiple biopsies from the same patient across different anatomical sites. RESULTS: PD-L1 mRNA levels strongly correlated with PD-L1 tumor staining (r = 0.55, p < 0.0001). Interferon-γ mRNA expression associated with PD-L1 immune cell staining, but not PD-L1 tumor cell staining. In contrast, PD-L1 copy number positively associated PD-L1 tumor staining, but not PD-L1 immune cell staining. PD-L1 copy number analysis detected loss (15 of 87 = 17%) and gain (5 of 87 = 7%) of copy number. Tumors with low PD-L1 copy number expressed significantly reduced levels of inflammatory (interferon-γ, interleukin [IL]-6, IL-1β, MMP-9) and immunosuppressive (IL-10, transforming growth factor β) mediators. Analysis of bronchoscopy-derived biopsies revealed low heterogeneity in copy number values across different anatomical sites, in contrast to more variable PD-L1 mRNA expression. CONCLUSIONS: Low PD-L1 copy number tumors display reduced PD-L1 expression, reduced PD-L1 tumor cell staining, and an immunologic cold tumor microenvironment. Because PD-L1 copy number values are highly stable across different tumor regions, its evaluation may represent a robust and complimentary biomarker for predicting response to immunotherapy, where low copy number may predict lack of response.