CS-11 * AN RNAi KINOME SCREEN OF GLIOBLASTOMA STEM CELLS UNDER NORMOXIA AND HYPOXIA

Abstract

Glioblastoma stem like cells are known to have phenotypes and gene expression patterns distinct from traditional glioma cell lines grown in serum. They also may have increased resistance to drugs and radiation and are likely to be responsible for tumor recurrence following therapy. As a result, it is important to identify therapeutic targets for these cells. To do this, we have conducted RNAi screens in glioblastoma stem cells against the human kinome since kinases are druggable targets and many kinase inhibitors are known. In addition, glioblastomas often have significant regions of hypoxia and glioblastoma stem cells tend to be resistant to hypoxia. We have therefore conducted shRNA screens in both normoxic and hypoxic conditions. We have screened 2 independent cell lines to date and are working on others. Defining a hit as a gene that has at least 2 independent shRNAs that give at least 50% growth inhibition as compared to controls, we found that 79 and 84 of (501 kinase genes) are hits under either normoxia or hypoxia for the GS6-22 and GS7-2 stem-like cell lines, respectively. We found that 56 and 63 kinases were hits under both conditions. 15 and 16 genes gave preferential inhibition under normoxia and 8 and 4 genes preferentially inhibited under hypoxia. 31 kinases were inhibitory in both cell lines. Thus, there is considerable variation between cell lines. Several of the identified hits are well known to have a role in glioblastoma such as EGFR and CDK4, and were inhibitory in both cell lines. About a third of the hits have previously been implicated in glioblastoma. One of the hits we have independently validated is the SMG1 kinase is preferentially inhibitory in hypoxia in only one of the cell lines. Together, these data give support to the idea of developing personalized therapies for glioblastoma.