P10.10.B BIRC3 AS A PREDICTOR OF OUTCOME AND A NEW THERAPEUTIC TARGET IN TMZ RESISTANT GLIOBLASTOMA TUMORS

Abstract BACKGROUND Glioblastoma (GB) is the most aggressive malignant tumor of the central nervous system, with a highly unfavorable prognosis with a median survival of 15 months. The standard treatment consists of surgical resection, chemotherapy, and radiotherapy. Despite intense research, overall survival remains stagnant, with very few approved therapeutic agents. Understanding the mutational profile of a tumor is important to inform diagnosis and guide therapeutic options, as well as identify patients that may not respond to treatment. The key advantage of precision medicine in oncology is the ability to match the right drug to the right patient to help improve patient outcomes. Aside from MGMT promoter methylation and TMZ response, molecular biomarkers associated with therapeutic response or prognostic of survival are still lacking in GB. In a recent study, using NADH-fluorescence lifetime imaging (NADH-FLIM), as a new drug screening precision medicine ex-vivo approach, we perturbed IDH1/2 WT GB patients-derived vital tumors by TMZ treatment and obtained a stratification in TMZ sensitive (S) and non-sensitive (NS) tumors, identifying several genes differentially expressed between the two groups. MATERIAL AND METHODS In this study, we enlarged our previous glioblastoma case study by performing NADH-FLIM metabolic approach to test TMZ drug tumor response on several primary and recurrent ex-vivo live GB tumors. Transcriptome analysis was performed to molecularly characterize TMZ S and NS cases. Moreover, functional cellular experiments were carried on to explore biomarkers' efficiency. RESULTS The majority of the genes, found dysregulated in the previous study, showed the same directional regulation of expression and we confirmed, in TMZ-resistant samples, the statistically significant upregulation of BIRC3, a strong inhibitor of apoptosis. The large public TCGA data set provided an opportunity to fully assess the BIRC3 mRNA expression complementarity with the MGMT status as a predictor of outcome in several cohorts analyzed with different RNA analysis approaches. BIRC3 functioned as a prognostic factor of survival also in a French and Italian private glioblastoma cohort analyzed by RNAseq and RT-PCR, respectively. In addition, most importantly, we show that the drug AZD5582, which is a specific antagonist of BIRC3, combined with TMZ treatment, is able to revert TMZ resistance, by restoring apoptosis, in glioblastoma cell lines and in patients derived organoids that are non-sensitive to TMZ-treatment. Higher levels of BIRC3 mRNA expression are associated with AZD5582 efficacy. CONCLUSION Investigating the mRNA expression levels of BIRC3 in GB tumors can be used as a tool to predict survival and response to TMZ. Moreover, the presence of high levels of BIRC3 mRNA is indicative of a new therapeutic target in glioblastoma tumors that are resistant to standard TMZ therapy.