CD39 expression as a predictive biomarker for neoadjuvant treatment in muscle-invasive bladder cancer.

850 Background: Neoadjuvant therapy before radical cystectomy (RC) is the the standard treatment for muscle-invasive bladder cancer (MIBC). However, a significant number of patients do not respond to these therapies. Identifying biomarkers predictive of treatment response and developing novel therapeutic strategies are crucial to improving patient management and survival. This study aims to investigate non-invasive biomarkers that can predict response to neoadjuvant therapy in MIBC patients and explore their potential use in the design of new therapies. Methods: Immunophenotyping was performed on blood and bladder tissue samples from MIBC patients at pre-treatment (transurethral tumor resection (TUR); n=17; chemotherapy n=13 and immunotherapy n=4) and post-neoadjuvant treatment (RC, n=21; chemotherapy n=18 and immunotherapy n=3). Plasma soluble CD39 (sCD39) and adenosine levels were measured by ELISA and an enzymatic assay, respectively. Treatment response was evaluated at RC, and patients were classified as non responders (³ypT2³N1) or responders (<ypT2ypN0). Results: Non responder patients exhibited a significant higher percentage of CD39 + cells in circulating total and different maturation CD4 + T cells subsets, particularly at TUR, suggesting a potential role in treatment resistance. CD39 + CD4 + T cells showed elevated PD-1 expression, decreased levels of Granzyme-B and Perforin, and strong correlations with the regulatory T cell marker FoxP3 and the checkpoint inhibitor TIGIT. Intratumoral CD39 + CD4 + T cells were also more frequent in non responder patients, correlating positively with the expression of tumor checkpoint inhibitors TIGIT and ICOS and the regulatory marker FoxP3. In blood, CD39 + CD4 + T cell frequencies correlated with sCD39 levels, which in turn were associated with adenosine concentration in plasma. Conclusions: CD39 expression in CD4 + T cells and its plasma levels emerge as promising biomarkers for predicting response to neoadjuvant treatment in MIBC. Targeting CD39 may offer a novel therapeutic strategy to overcome treatment resistance, potentially improving outcomes in MIBC patients.