B Cells Undergo Transcriptional Changes Following Autoimmune Sicca Development in Melanoma Patients Treated with Immune Checkpoint Inhibitors 2256997

Abstract Introduction Immune checkpoint inhibitor (ICI) therapy has revolutionized the treatment of melanoma and other cancers but can cause immune-related adverse events (irAEs) and lasting autoimmune tissue damage. One such irAE (ICI-sicca) shares some features with the rheumatic disease, Sjögren’s syndrome, with dry mouth being the symptom typically reported by ICI-sicca patients. A fraction of ICI-sicca patients have Sjögren’s-associated autoantibodies, signifying autoreactive B cell activity in this disease. Methods To identify B cell gene dysregulation that arises with ICI-sicca onset, we used single-cell RNA-sequencing to compare CD19+ cells isolated from peripheral blood collected 3-4 weeks after ICI therapy initiation (pre-ICI sicca) or following ICI-sicca symptom onset (post-ICI sicca) in n = 6 melanoma patients. Transcriptome-based clustering using Seurat identified n = 14 clusters, which we manually collapsed into five major B cell subsets (transitional, naïve, activated, memory, and plasmablasts). Results We observed upregulation of genes following ICI-sicca development in naïve (n = 1296 genes), activated (n = 42 genes), and memory (n = 775 genes) B cell subsets, relative to the pre-ICI sicca timepoint, based on adjusted p-value < 0.05 and fold change > 1.2 cutoffs. These upregulated genes were related to BCR signaling, actin cytoskeleton rearrangement, antigen processing and presentation, and interferon responses. Conclusion Some of the ICI-sicca upregulated genes were also noted to be increased in rheumatic disease patients relative to healthy controls in other single-cell RNA-seq studies performed by our lab, suggesting the potential for shared B cell liability across spontaneous and ICI-induced autoimmunity. Future studies will validate alteration of these key B cell functions and explore pharmacologic methods to restore this aberrant B cell rewiring as a means to generate new hypotheses that can be tested with the ultimate goal of limiting ICI sicca, and potentially other irAE development. Funding Source National Institutes of Health Grants R03 AI163835 (RHB), Luke and Susan Simons Directorship (DBJ), and K12 HD043483 (RHB), as well as the Vanderbilt University Summer Research Program (HB), MARC/START (HB) supported this work. Studies were performed using Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)