Abstract B060: CMV-induced adaptive NK cell functions to improve bladder cancer patient outcomes

Abstract INTRODUCTION Intravesical instillation of Bacillus Calmette Guérin (BCG) is the frontline therapy for high grade non-muscle invasive bladder cancer (NMIBC). However, 32-42% of patients experience recurrence and 13% progress to muscle-invasive disease. The immune system is shaped by lifelong virus exposures. Notably, 50-60% of adults in the United States are seropositive for Cytomegalovirus (CMV), a latent herpesvirus that undergoes periodic reactivation. Among CMV-seropositive individuals, 40-50% harbor a population of "adaptive" NKG2C+ NK cells that expand in response to CMV peptides presented by HLA-E. These cells may hold promise for overcoming treatment resistance in NMIBC. METHODS CMV antibody levels were assessed in plasma and urine from BCG-treated patients using ELISA. Bladder tissues were analyzed before, during and after BCG treatment in responders and non-responders using RNAscope and multiplexed imaging. Functional profiling and phenotyping of patient-derived NK cells were performed using mass cytometry on ex vivo samples (urine, bladder tissue) and in co-culture assays with tumor cells. RESULTS In a novel cohort of 90 BCG-treated NMIBC patients from Mount Sinai, CMV+ patients demonstrated significantly lower recurrence rates than CMV- patients. Notably, CMV+ patients with circulating adaptive NK cells exhibited complete responses to therapy and a heightened IFN-ɣ response following treatment. Adaptive NK cells in BCG-treated patients showed superior antibody-dependent cell cytotoxicity compared with conventional NK cells. Unique to the CMV+ patients, BCG therapy induced a strong humoral response marked by elevated IgG levels, underscoring the potential importance of ADCC in immune surveillance. Independent of treatment response, CMV was present within the bladder microenvironment, including infection of stromal, immune and even tumor cells. In CMV+ responders, adaptive NK cells were observed in close proximity to CMV-infected cells. BCG treatment further induced increased HLA-E expression in the bladder micro-environment, creating conditions favorable for activating NKG2C+ adaptive NK cells. To consider novel immunotherapy strategies, we evaluated approaches for expanding adaptive NK cells prior to BCG administration. Fresh bladder tumor biopsies were treated with CMV peptides to stimulate adaptive NK cells expansion. Additionally, we treated tumor-infiltrating NK cells with anti-NKG2C agonist antibodies to enhance their cytotoxicity and reinforce the adaptive NK cell response. CONCLUSION We present a mechanism shaping the response to BCG therapy in NMIBC, driven by CMV reactivation and expansion of adaptive NK cells. Our data indicate that lifelong CMV imprinting strongly affects tumor recurrence control during BCG treatment. We also outline strategies to improve therapeutic efficacy, including CMV peptide-based immune modulation and antibody immunotherapies, which offer promising avenues for improving patient outcomes and reducing recurrence in NMIBC. Citation Format: Bérengère Salomé, Igor Duquesne, Amber Barbini, Sonia Domingos Pereira, John C. Ingles, Quirin Hammer, Nina Bhardwaj, Matthew D. Galsky, Laurent Derré, John P. Sfakianos, Amir Horowitz. CMV-induced adaptive NK cell functions to improve bladder cancer patient outcomes [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr B060.