CB-08 * KIF3A IS ESSENTIAL FOR CILIOGENESIS, CILIA FUNCTION AND PROMOTES GLIOBLASTOMA PROGRESSION

Abstract

Despite recent findings that cilia transduce diverse signaling pathways affecting cell proliferation, migration and survival, little is known about the influence of cilia or cilia-associated proteins in glioblastoma multiforme (GBM). We recently showed that primary cilia project from subsets of cells in GBM patient biopsies and derived cell lines. To determine if cilia contribute to GBM growth, we blocked ciliogenesis using a lentivirus expressing a dominant negative form of KIF3A, an essential ciliogenesis protein. We generated stable GBM cell lines (L0 and S3; representing different molecular subclasses) whereby dnKIF3A+ cells exhibited virtual complete loss of cilia compared to controls (confirmed by immunostaining and EM). Canonically, secreted Sonic hedgehog (SHH) ligand binds and activates receptor signaling cascades (e.g., smoothened (SMO)) within cilia to promote normal cell proliferation and tumor cell growth in specific developmental and pathological contexts, respectively. To examine the role of SHH in GBM proliferation, we exposed control and dnKIF3A+ L0 and S3 cells to saline or recombinant SHH. We found the number of L0 control cells significantly increased after SHH compared to saline, an effect blocked by pretreatment with cyclopamine (SMO inhibitor). However, SHH did not increase the number of L0 dnKIF3A+ cells. Interestingly, SHH exposure had no effect on S3 control cell numbers, despite observations that SHH signaling components (SMO and Gli3) were recruited to their cilia in response to SHH. This suggests GBM cilia are SHH-responsive but the downstream consequences of ciliary signaling may differ between cell lines. Notably, mice intracranially xenografted with L0 cells expressing dnKIF3A survived significantly longer than mice receiving control cells, and retained the loss of cilia phenotype in the tumors. Collectively, these data suggest KIF3A promotes GBM tumor progression, but the extent to which the effects are mediated by cilia and the heterogeneity of SHH-dependence across GBM subtypes requires further investigation.