CSIG-23. PRIMARY CILIA DISRUPTION ALTERS THE TRANSCRITOME OF HUMAN GLIOBLASTOMA CELLS AND SUGGESTS NOVEL THERAPEUTIC STRATEGIES

Abstract

Abstract BACKGROUND Glioblastoma is the most common malignant primary brain tumor. Despite standard-of-care therapy with maximal safe resection, concomitant chemoradiation followed by adjuvant chemotherapy, median survival is 18 months, and 5-year survival is 6.8%. The genetic complexity, ability to suppress host immune surveillance, and the blood-brain-barrier all contribute to the uniform fatality of the disease. Primary cilia are microtubule-based organelles that protrudes from the apical surface of all mammalian cells. They regulate several canonical signal transduction cascades important for development and pathogenesis. Glioblastoma cells are ciliated although the tumor downregulate genes associated with cilia formation and function. Contemporary studies suggest that the regulation of ciliogenesis is an important prognostic consideration. In this study, human glioblastoma cells were modified through stable lentiviral transduction to downregulate KIF3A (a gene required for ciliogenesis), or AURKA (a component of the ciliary disassembly complex). We then performed deep transcriptomic sequencing to determine how the overall transcriptome of human glioblastoma cells change in response to cilia-targeted genetic manipulation. RESULTS High-resolution confocal microscopy demonstrated that cilia were absent in KIF3A knockdown cells but abundant following loss of AURKA. Functional loss of primary cilia was confirmed with Gli2A RT-PCR following treatment with SAG (SHH pathway activator). There appeared to be rearrangement of the transcriptome with ciliary loss. Ingenuity Pathway Analysis demonstrated that ciliary loss resulted in the activation of pathways of glioblastoma and other cancer signaling pathways, tumor immune microenvironment pathways, cytokine signaling, and actin cytoskeletal rearrangement among several others. CONCLUSION Loss of primary cilia in glioblastomas activate several pro-cancer and immunosuppressive pathways. This suggests that targeting of primary cilia may lead to simultaneous loss of multiple glioblastoma phenotypes that contribute to the tumor’s evolutionary advantage. This may result in a novel paradigm of ‘ciliotherapeutics’ for glioblastomas and other cancers.