Radiation and Bacillus Calmette-Guérin (BCG) instillations are used clinically for treatment of urothelial carcinoma, but the precise mechanisms by which they activate an immune response remain elusive. The role of the cGAS-STING pathway has been implicated in both BCG and radiation-induced immune response however comparison of STING-pathway molecules and immune landscape following treatment in urothelial carcinoma has not be performed. We therefore comprehensively analyzed the local immune response in the bladder tumor microenvironment following radiotherapy and BCG instillations in a well-established spontaneous murine model of urothelial carcinoma to provide insight into activation of STING-mediated immune response. Mice were exposed to the oral carcinogen, BBN, for 12 weeks prior to treatment with a single 15Gy dose of radiation or 3 intravesical instillations of BCG (1x108 CFU). At sacrifice, tumors were staged by a urologic pathologist and effects of therapy on the immune microenvironment were measured using the NanoString Myeloid Innate Immunity Panel and immunohistochemistry. Clinical relevance was established by measuring immune biomarker expression of cGAS and STING on a human tissue microarray consisting of BCG-treated non-muscle invasive urothelial carcinomas. BCG instillations in the murine model elevated STING and downstream STING-induced interferon and pro-inflammatory molecules, intratumoral M1 macrophage and T-cell accumulation, and complete tumor eradication. In contrast, radiotherapy caused no changes in STING pathway or innate immune gene expression; rather, it induced M2 macrophage accumulation and elevated FoxP3 expression characteristic of immunosuppression. In human non-muscle invasive bladder cancer, STING protein expression was elevated at baseline in patients who responded to BCG therapy and increased further after BCG therapy. Overall, these results show that STING pathway activation plays a key role in effective BCG-induced immune response and strongly indicate that the effects of BCG on the bladder cancer immune microenvironment are more beneficial than those induced by radiation. This article is protected by copyright. All rights reserved.
The Journal of pathology. 2021 Nov 03 [Epub ahead of print]
Kara A Lombardo, Aleksandar Obradovic, Alok Kumar Singh, James L Liu, Gregory Joice, Max Kates, William Bishai, David McConkey, Alcides Chaux, Marie-Lisa Eich, M Katayoon Rezaei, George J Netto, Charles G Drake, Phuoc Tran, Andres Matoso, Trinity J Bivalacqua
Department of Urology, The Johns Hopkins Medical Institutions, Baltimore, MD, USA., Department of Systems Biology, Columbia University Irving Medical Center, New York, NY, USA., Center for Tuberculosis Research, The Johns Hopkins Medical Institutions, Baltimore, MD, USA., Greenberg Bladder Cancer Institute, The Johns Hopkins Medical Institutions, Baltimore, MD, USA., Department of Scientific Research, School of Postgraduate Studies, Norte University, 1614, Asunción, Paraguay., Department of Pathology, The University of Alabama at Birmingham, Birmingham, AL, USA., Department of Pathology, George Washington University, Washington, DC, USA., Division of Urology, Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY, USA.