Alterations in cellular metabolome after pharmacological inhibition of Notch in glioblastoma cells

Abstract

Notch signaling can promote tumorigenesis in the nervous system and plays important roles in stem-like cancer cells. However, little is known about how Notch inhibition might alter tumor metabolism, particularly in lesions arising in the brain. The gamma-secretase inhibitor MRK003 was used to treat glioblastoma neurospheres, and they were subdivided into sensitive and insensitive groups in terms of canonical Notch target response. Global metabolomes were then examined using proton magnetic resonance spectroscopy, and changes in intracellular concentration of various metabolites identified which correlate with Notch inhibition. Reductions in glutamate were verified by oxidation-based colorimetric assays. Interestingly, the alkylating chemotherapeutic agent temozolomide, the mTOR-inhibitor MLN0128, and the WNT inhibitor LGK974 did not reduce glutamate levels, suggesting that changes to this metabolite might reflect specific downstream effects of Notch blockade in gliomas rather than general sequelae of tumor growth inhibition. Global and targeted expression analyses revealed that multiple genes important in glutamate homeostasis, including glutaminase, are dysregulated after Notch inhibition. Treatment with an allosteric inhibitor of glutaminase, compound 968, could slow glioblastoma growth, and Notch inhibition may act at least in part by regulating glutaminase and glutamate.

A comparative pharmaco-metabolomic study of glutaminase inhibitors in glioma stem-like cells confirms biological effectiveness but reveals differences in target-specificity

“…Previous publications reported that genetic and pharmacological inhibition of GLS attenuates stemness properties in hepatocellular, colorectal, and prostate cancer 21,23,43 . Furthermore, our group showed that the prominent route of anti-GSC therapy using γ-secretase inhibitor MRK003 targets GSC growth, in part by reducing intracellular Glu as a consequence of GLS inhibition 56 .…”

Targeting Glutamine Addiction in Gliomas

“…Another recently published study demonstrated that treatment with a GLS-selective inhibitor, compound 968, suppressed the growth of patient-derived GBM cells with an inhibited Notch pathway. Notch blockade diminished the expression of GLS, as well as levels of glutamine and glutamate, indicating that the antiproliferative effect of Notch inhibition might be partially mediated by alterations in the glutamine/glutamate cycle [83].…”

Clinically Actionable Insights into Initial and Matched Recurrent Glioblastomas to Inform Novel Treatment Approaches

“…Many IDH WT tumours had alterations impacting WNT [59][60][61][62][63] signalling pathway genes (58%) including CREBBP(4), KLF4 (2) [64,65], TERT(2) [17], and APC(3) [66][67][68][69][70]; however, targeting this pathway is currently challenging. Initial IDH WT tumours also showed predicted pathogenic variation in NOTCH (11%) [71] and SHH (13%) pathways [72] including PTCH1 (PATCHED-1) and SMO (Smoothened) [73][74][75]. e Hedgehog antagonist GDC-0449 (vismodegib) has been trialled in recurrent GBM (NCT00980343) and childhood brain tumours with varying success to date.…”