P12.08.A DECIPHERING WNT6-DRIVEN MECHANISMS OF AGGRESSIVENESS AND RESISTANCE TO CHEMOTHERAPY IN HUMAN GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is among the deadliest human cancers, characterized by high heterogeneity that renders standardized treatments largely ineffective. The identification of biomarkers predictive of therapy response, and elucidating their underlying mechanisms, could unveil novel therapeutic opportunities and advance precision medicine strategies. We recently demonstrated that WNT6, a key WNT signaling activator, acts as an oncogenic driver and has prognostic value in GBM, but the molecular mechanisms by which WNT6 influences GBM aggressiveness and its impact on therapy response remain elusive. METHODS RNA sequencing of two matched GBM in vitro models with differential WNT6 expression provided a comprehensive transcriptomic profile. Bioinformatics analyses, including functional annotation, gene-set enrichment, and ingenuity pathways analysis, identified WNT6-driven biological processes. Functional and molecular assays, along with an in vivo orthotopic experiment, evaluated WNT6’s impact on temozolomide (TMZ) sensitivity, the standard GBM chemotherapy. Clinical data analyses assessed the prognostic significance of WNT6 in TMZ-treated GBM patients. RESULTS The WNT6 transcriptome was enriched in processes and pathways that suggest a potential role for WNT6 in therapy resistance. In vitro, WNT6 expression reduced TMZ efficacy across multiple oncogenic features, which was further supported in vivo, where WNT6-high tumors showed decreased responsiveness to TMZ in comparison to WNT6-low tumors. WNT6 expression was also associated with the differential activation of DNA repair pathways critical for TMZ response, including base excision repair, mismatch repair, and MGMT-mediated repair. Among TMZ-treated GBM patients, WNT6 was found to be an independent predictor of reduced survival. CONCLUSION This study suggests that WNT6 is predictive of TMZ response in GBM, and sheds light on the molecular mechanisms by which WNT6 may be operating. Collectively, these findings position WNT6 as a promising candidate for future therapeutic strategies in precision medicine, including combination therapies targeting WNT6 and its associated resistance pathways to improve TMZ efficacy. SUPPORT/DISCLOSURE Financial support was provided by grants and projects from FCT (https: //doi.org/10.54499/2022.04859.PTDC to B.M.C. and E.P.M.; https: //doi.org/10.54499/2021.02600.CEECIND/CP1664/CT0015 to C.S.G; and 2024.00785.BD to J.M.F.) and by National funds https: //doi.org/10.54499/UIDB/50026/2020, and https: //doi.org/10.54499/UIDP/50026/2020, https: //doi.org/10.54499/LA/P/0050/2020, and by the project NORTE-01-0145-FEDER-000055, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).