ANGI-14. DRUGGABLE GENOME CRISPR SCREEN IN 3D HYDROGEL DEVICES REVEALS TARGETABLE KINASES AND PHOSPHATASES IMPLICATED IN CYTOSKELETAL REORGANIZATION IN INVADING GBM CELLS

Abstract The invasive nature of glioblastoma cells into adjacent brain tissues is a key factor in its unfavorable prognosis. To decipher the mechanisms driving glioblastoma invasion, we developed microdissectable biomimetic 3D hydrogel invasion devices containing hyaluronic acid hydrogels decorated with integrin-binding peptides (RGD) and crosslinked with protease-cleavable crosslinkers. The ability to disassemble these devices and interrogate cells in the core vs. invasive fraction allows for high throughput screens. We thus performed a screen in GBM43 cells expressing CRISPR/Cas9 and a 13,250 gRNA library targeting the 2550 genes in the druggable human genome. Of seven initial hits from this screen, only two could be validated by single gene CRISPR and use of a drug to target the hit - ACP1 (also known as LMW-PTP) and Aurora Kinase B (AURKB). Integration of ChIP-seq and RNA-seq revealed no plausible transcriptional targets of ACP1 and AURKB that could drive invasion. Proximity labeling with the TurboID system identified CTTN (cortactin), an actin binding protein whose phosphorylation is integral to the formation of lamellipodia and invadopodia, as phosphorylated by AURKB and Ephrin A2 (EPHA2), whose dephosphorylation controls cell morphology, adhesion, migration and invasion by modifying the organization of the actin cytoskeleton and influencing the activities of integrins and intercellular adhesion molecules, as dephosphorylated by ACP1. These findings underscore the delicate balance between kinase and phosphatase activities in regulating the actin cytoskeleton broadly and at the cell’s front or “leading edge,” offering new therapeutic targets to disrupt the invasion that is a hallmark of glioblastoma.