A Large-Scale RNAi Screen Identifies SGK1 as a Key Survival Kinase for GBM Stem Cells

Abstract

Glioblastoma multiforme (GBM) is the most common type of primary malignant brain cancer and has a very poor prognosis. A subpopulation of cells known as GBM stem-like cells (GBM-SC) have the capacity to initiate and sustain tumor growth and possess molecular characteristics similar to the parental tumor. GBM-SCs are known to be enriched in hypoxic niches and may contribute to therapeutic resistance. Therefore, to identify genetic determinants important for the proliferation and survival of GBM stem cells, an unbiased pooled shRNA screen of 10,000 genes was conducted under normoxic as well as hypoxic conditions. A number of essential genes were identified that are required for GBM-SC growth, under either or both oxygen conditions, in two different GBM-SC lines. Interestingly, only about a third of the essential genes were common to both cell lines. The oxygen environment significantly impacts the cellular genetic dependencies as 30% of the genes required under hypoxia were not required under normoxic conditions. In addition to identifying essential genes already implicated in GBM such as , and, the screen also identified new genes that have not been previously implicated in GBM stem cell biology. The importance of the serum and glucocorticoid-regulated kinase 1 (SGK1) for cellular survival was validated in multiple patient-derived GBM stem cell lines using shRNA, CRISPR, and pharmacologic inhibitors. However, SGK1 depletion and inhibition has little effect on traditional serum grown glioma lines and on differentiated GBM-SCs indicating its specific importance in GBM stem cell survival. This study identifies genes required for the growth and survival of GBM stem cells under both normoxic and hypoxic conditions and finds SGK1 as a novel potential drug target for GBM. .

Multidisciplinary Role of Mesoporous Silica Nanoparticles in Brain Regeneration and Cancers: From Crossing the Blood–Brain Barrier to Treatment

“…Gliomas are tumors originating mostly from the brain glial cells that include the glioblastoma multiforme (GBM) (WHO grade IV gliomas) as well as other low‐grade gliomas. GBMs are the most frequent, malignant and aggressive subtypes of glioma, with exceedingly high relapse and poor prognosis, because GBM progenitor cells with tumor‐precursors are resistant to radiation and chemotherapy Devastating glioma cells show fast infiltration and hide in inaccessible areas of brain, which rules out the possibility of surgery, and radiation methods . Chemotherapy fails in most of the GBM patients since most drugs are incapable of crossing the BBB and arriving at tumor tissues .…”

SGK1 Signaling Promotes Glucose Metabolism and Survival in Extracellular Matrix Detached Cells

“…The unique capacity of SGK1 to promote enhanced glucose uptake during ECM-detachment suggests that SGK1 signaling may be disproportionately important when cells encounter distinct stresses. Indeed, recent studies have demonstrated that SGK1 can promote resistance to chemotherapies and contribute to oncogenic transformation (Castel et al, 2016;Kulkarni et al, 2018;Ma et al, 2019;Orlacchio et al, 2017) suggesting that SGK1 signaling is valuable for navigating stressful environments. 18 SGK1 has long been known to function as an effector of PI(3)K signaling in a fashion that can be analogous to Akt.…”

Glioblastoma Multiforme: Fewer Tumor Copy Number Segments of theSGK1Gene Are Associated with Poorer Survival

“…They found that SGK1 depletion and inhibition has little effect on serum grown glioma lines and on differentiated GBM stem-like cells, indicating its specific importance in GBM stem-like cell survival only on glioblastoma cells interacting with multiple other genes. Kulkarni et al validated SGK1 as critical for GBM stem-like cell proliferation and survival, using shRNA, CRISPR and an SGK1-specific inhibitor (5).…”

“…Kulkarni et al have reported that the serum and glucocorticoid-regulated kinase (SGK1) gene is required for the growth and survival of GBM stem-like cells under both normoxic and hypoxic conditions (5). In this analysis, we examined the role of the SGK1 gene in glioblastoma survival to determine if it might be a potential drug target.…”