The Urothelial Transcriptomic Response to Interferon Gamma: Implications for Bladder Cancer Prognosis and Immunotherapy

Simple Summary Bladder cancers are frequently treated by instilling BCG vaccine into the bladder. By provoking inflammation, BCG can lead to the production of a factor called "interferon gamma" and an immune response that can eliminate the cancer. Here, we used normal human uro-epithelial cells that line the urinary tract to establish a specific "signature" of genes activated in response to interferon gamma. When assessed in bladder cancers, the interferon gamma signature was associated with a subset of patients who showed significantly better survival. In normal tissues, immune responses are subject to stop signals called "checkpoints" that prevent runaway inflammation, and this process may prevent immune cells from killing cancer cells. New treatments aimed at tackling immune checkpoints have met with limited success in bladder cancer. In this study, we have identified immune checkpoint genes expressed by normal human uro-epithelial cells that were increased by interferon gamma. This research suggests new targets for use in combination treatments aimed at overcoming immune checkpoints. Interferon gamma (IFN gamma) is central to the inflammatory immune response, such as that entrained by BCG immunotherapy for bladder cancer. However, immune-mediated tumour cell killing is subject to modulation by immunoinhibitory "checkpoint" receptors such as PD-L1. We investigated the effects of IFN gamma on barrier-forming in vitro-differentiated normal human urothelium using mRNA-sequencing, and showed canonical upregulation of MHC class I/II and de novo expression of the T cell tropic CXCL9-11 chemokines. Normal urothelium constitutively expressed immunoinhibitory B7 family member VSIR (VISTA), while CD274 (PD-L1) expression was induced/upregulated by IFN gamma. We generated a urothelial IFN gamma response gene signature. When applied to the unsupervised clustering of non-muscle-invasive bladder cancers, the IFN gamma-signature predicted longer recurrence-free survival. In muscle-invasive cancers, the IFN gamma-signature split the basal/squamous consensus subtype, with significantly worse overall survival when weak or absent. This study offers novel insights into strategies to enhance immunotherapy via the IFN gamma and VISTA/PD-L1 nexus.