GSK3 acts as a switch for transcriptional programs in a model of low-grade gliomagenesis

Mutations in isocitrate dehydrogenase (IDH)-1/2 are defining drivers of low-grade gliomagenesis. However, mutant IDH alone is not sufficient for malignant transformation, and additional events are required for the development of low-grade glioma. While specific genetic lesions have been identified to contribute to low-grade gliomagenesis, less is known about the signaling pathways involved in acquiring malignancy. To identify prerequisites of IDH mutant tumorigenesis, we modulated pathways previously implicated in glioma initiation using a tractable in vitro model system for early IDH1R132H-dependent gliomagenesis. Through the use of chemical compounds, we targeted WNT/GSK3, TGF-ß and NOTCH-signaling, assessing their functional, transcriptional, and translational impacts. Expression of LGG-related marker L1CAM was affected by perturbation of all pathways, though only modulation of WNT/GSK3-signaling resulted in profound molecular transformation, including glioma-associated genes and programs regulating cellular architecture and cell replication. This was accompanied by altered cell morphology, migration capacity, and enhanced proliferation. Transcription factor RUNX2 was identified as a potential downstream effector, whose inhibition abrogated cell proliferation. Disrupted WNT/GSK3 signaling in a model system of early low-grade gliomagenesis fundamentally impacted cell fate, as demonstrated by a reshaped transcriptional landscape, aberrant transcription factor activity, ECM restructuring, and altered proliferation capacity. Our data suggests that GSK3 may play a central role during low-grade gliomagenesis, warranting further investigation. Overall design: RNA-seq profiling of immortalized IDH1R132H human astrocytes treated with CHIR99021, Repsox or YO-01027 resp. mock and RNA-seq profiling of immortalized IDH1R132H human astrocytes treated with CHIR99021 and siRUNX2 or siControl