gms | German Medical Science

Objective: Glioma stem-like cells (GSCs) are the cardinal drivers for glioblastoma (GBM) progression and emergence of therapy resistance. Compounds blocking the important stem cell pathway Notch such as inhibitors of γ-secretase inhibitor (GSIs) have proven to possess therapeutic potential by targeting GSCs, however, clinical translation has been challenging. We evaluated the effect of brontictuzumab (Bmab), a novel and highly receptor specific Notch blocking antibody on a series of GSCs to validate its biological effectivity in the context of brain tumor.

Methods: Spheroidal GSCs were treated with GSI MRK003 or Bmab and characterized by quantification of target gene expression, cellular growth by Titer blue assay and invasion by modified Boyden chamber assays. Results are verified by genetic models with blocked Notch1 receptor. Lastly, we investigated whether pharmacological Notch inhibition causes any deregulation in WNT pathway activation by quantification of target gene expression through highly sensitive TCF luciferase reporter system and SYBR green based mRNA assessments. Clinical significance of Notch1 was analyzed by assessing large patient data cohorts from Eastern (CGGA) and Western (TCGA) world.

Results: We designated our cell line models in resistant and sensitive towards Bmab. Base line Notch 1 activation predicts sensitivity towards the drug. Bmab can cause Notch pathway suppression in responder cell in lower molecular concentration than MRK003 control causing significant suppression of Hes1 and Hey1 transcription. Moreover, Notch1 blockade caused solid blockade of cellular invasion but had almost no effect on growth. Moreover, we noticed of induction of WNT pathway under both of the pharmacological treatments. High Notch 1 expression in GBMs is associated with IDH1 R132H mutation and with proneural subtype.

Conclusion: Bmab is potent to block Notch signaling in GBMs in vitro causing significant suppression of invasion. Given its highly specific target binding, Bmab may help to minimize off target problems observed when treating patients with pan-Notch blockers. High Notch1 expression may help to predict the sensitivity of GBMS towards Bmab which may be particularly beneficial for tumors with IDH1 mutation and of the proneural lineage. However, the active Notch-WNT crosstalk in GBMs potentially compensates the diminishment of one of the stem cell signals. Further studies in vivo are needed to validate the therapeutic potential of Bmab.