Abstract 142: cdk5 inhibition promotes neurogenesis while reducing self-renewal of brain tumor stem cells

Abstract

Abstract Cancer stem cells are biologically potent and support tumor growth, in part by deregulating asymmetric stem cell division. Asymmetric cell division of stem cells is a type of mitotic division where a stem cell generates one stem and one differentiated cell. Cancer stem cells, however, tend to generate more stem-like dividing cells to promote neoplasm. To uncover mechanisms and potential therapeutic targets relevant to self-renewal in human glioma stem cells (GSCs), we performed a genetic screen for kinases that reverse the tumor phenotype of our novel adult Drosophila brain tumor model and found that knockdown of the brain-specific dCdk5 was highly effective in suppressing the self-renewing stem cell components. A highly specific CDK5 inhibitor is promoting neurogenesis among these fly brain cancer stem cells. These cancer stem cells, although they express glial markers in tumors, do not differentiate into glia upon CDK5 suppression. Additionally, while the tumor generation in adult flies completely disrupts the mushroom body, the main cognitive center in adult fly brain, the CDK5 inhibition partially rescues the mushroom body and extends life span of these flies. dCdk5 and its human ortholog CDK5 (79% identity) are aberrantly activated in some forms of cancer. We demonstrate that GBMs highly express CDK5 mRNA and protein, likely related to copy number gains of chromosome 7, with strong positive correlation with stem cell markers and marked effect on tumor-propagating properties. Using human GSCs isolated from tumor spheres and mouse xenografts, we found that CDK5 directly phosphorylates CREB1 independent of cAMP and stops stem cell renewal. These data together show that CDK5 inhibition not only can attenuate self-renewal properties of brain tumor stem cells, but also can promote neurogenesis, which could potentially become a better treatment strategy for patients and improve their cognitive function as well. Citation Format: Subhas Mukherjee, Cheryl Olson, Daniel Brat. cdk5 inhibition promotes neurogenesis while reducing self-renewal of brain tumor stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 142.