NEOANTIGEN LOAD OF NMIBC TUMOR SAMPLES PREDICTS BCG RESPONSE BETTER THAN NEOANTIGEN QUALITY AND TCR DIVERSITY

About 70-80% of bladder cancer cases correspond to non-invasive forms (NMIBC). The treatment of NMIBC is surgical (transurethral resection of the bladder tumor), followed by adjuvant immunotherapy with BCG intravesical applications (Bacillus Calmette-Guérin) in cases classified as high or intermediate risk of disease recurrence. Approximately 30-40% of patients do not respond to treatment with BCG and relapse; also 1025% progress to invasive forms. The immune system is a protagonist in controlling tumor evolution, which explains the success of immunotherapies for the treatment of NMIBC with BCG and metastatic MIBC with immune checkpoint inhibitors. The formation of a specific immune response against a tumor depends on mutation expression and neoantigen formation, presentation and subsequent recognition by CD8+ T-cell receptors (TCRs). TCRs are unique sequences specific to each antigen, which are expressed in T-lymphocytes. After encountering neoantigens, T-cells undergo clonal expansion, increasing the clonality of specific TCRs that recognize these neoantigens and, consequently, decreasing the diversity of the repertoire of TCR sequences present in the tumor-infiltrating lymphocytes (TIL) of patients. We believe that a higher quantity and a higher quality of neoantigens (measured by its similarity with pathogen epitopes), as well as a lower diversity (due to a greater clonality) of TCR sequences of CD8+ lymphocytes in TIL are evidences of the activation of a specific immune response against neoantigens, directly interfering in the response to treatment with immunotherapies. In this work, using data from somatic mutations of NMIBC tumors, we performed the prediction of neoantigens and evaluated the importance of the probability of these epitopes being recognized by TCRs (neoantigens quality) in the context of response to BCG. We found a significant association between a greater amount of neoantigens and a better response to BCG (Wilcoxon rank-sum test, p=0,0406), as well as longer survival (Log-rank test, p=0,04). Higher numbers of neoantigens with quality greater than zero had a tendency of being associated with longer survival (Log-rank test, p=0,071). We also investigated whether the TCR diversity is associated with the response to BCG. We performed TCR-seq of NMIBC tumors, but didn□t find statistically significant differences, only a tendency of association between higher TCR diversities and longer survival (Log- rank test, p=0,1).