Bcg Can Subvert Patients Antitumor Immune Response By Downregulating Hla-I Expression On Cancer Cells.

Abstract Patients with high-risk non muscle-invasive bladder cancer (NMIBC) frequently relapse after standard BCG immunotherapy and have a dismal outcome after progression to muscle-invasive bladder cancer (MIBC). The mechanisms of tumor resistance to such immunotherapy remain elusive. We performed functional assays of fresh bladder tumors mixed with BCG, reinforced with in vitro experiments and in situ immune profiling of a cohort of MIBC pre- and post BCG therapy. Here, we demonstrate two distinct patterns of BCG-induced immune subversion. In the first pattern, intracellular BCG infection was associated with HLA-I loss and epithelial-to- mesenchymal transition (EMT) characteristics. HLA-I deficient tumors displayed a myeloid immunosuppressive microenvironment and dismal outcomes. Conversely, HLA-I+ BCG-treated tumors generated a Th1 type of immune response associated with an upregulation of exhaustion markers. Such patients had a very favorable outcome upon radical surgery. We surmise that HLA-I expression in bladder cancers does not result from immunoediting but rather from a BCG-induced EMT process that predicts dismal prognosis. Cancer cells HLA-I scoring by immunohistochemistry (IHC) staining can be easily implemented by pathologists in routine practice in order to stratify future urothelial cancer patient treatment strategies. Citation Format: Mathieu Rouanne, Julien Adam, Camélia Radulescu, Séverine Mouraud, Delphine Bredel, Diane Letourneur, Tuan Zea Tan, Nicolas Signolle, Amélie Bigorgne, Michael Dussiot, Sandrine Susini, Lambros Tselikas, François-Xavier Danlos, Roman Chabanon, Anna K. Schneider, Sophie Vacher, Thierry Lebret, Ivan Bièche, Yves Allory, Jean-Charles Soria, Jean Paul Thiery, Laurence Zitvogel, Aurélien Marabelle. BCG can subvert patients antitumor immune response by downregulating HLA-I expression on cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 66.