Primary Cilia Disruption Alters the Transcritome of Human Glioblastoma Cells by Changing Methylation Status

Introduction: Glioblastoma is the most common malignant primary brain tumor. Despite standard-of-care therapy, median survival is approximately 18 months. 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.

Methods: In this study, human glioblastoma cells were modified through stable lentiviral transduction to downregulate KIF3A and IFT88 (a gene required for ciliogenesis). We then performed deep transcriptomic sequencing to determine how the overall transcriptome of human glioblastoma cells change in response to cilia-targeted genetic manipulation. Furthermore, we also preformed methylation analysis to assess the correlation with transcriptome.

Results: The absence of primary cilia in KIF3A or IFT88 knockdown cells was demonstrated using high-resolution confocal microscopy, and functional loss of primary cilia was confirmed with the expression level of activated Gli1 by western blotting, that is one of the components of SHH signal pathway. There appeared to be rearrangement of the transcriptome and methylation status with ciliary loss. 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 cancer-related and immunosuppressive pathways. This suggests that genetic or pharmaceutical modification of primary cilia structure and/or function may lead to simultaneous loss of multiple glioblastoma phenotypes that contribute to tumorigenesis.