ROR1 facilitates glioblastoma growth via stabilizing GRB2 to promote c-Fos expression in glioma stem cells

BACKGROUND: Glioma stem cells (GSCs) are the root cause of tumorigenesis, recurrence, and therapeutic resistance in glioblastoma (GBM), the most prevalent and lethal type of primary adult brain malignancy. The exploitation of novel methods targeting GSCs is crucial for the treatment of GBM. In this study, we investigate the function of the novel ROR1-GRB2-c-Fos axis in GSCs maintenance and GBM progression. METHODS: The expression characteristics of ROR1 in GBM and GSCs were assessed by bioinformatic analysis, patient specimens, and patient-derived GSCs. Lentivirus-mediated gene knockdown and overexpression were conducted to evaluate the effect of ROR1 on GSCs proliferation and self-renewal both in vitro and in vivo. The downstream signaling of ROR1 in GSCs maintenance was unbiasedly determined by RNA-seq and validated both in vitro and in vivo. Finally, rescue assays were performed to further validate the function of the ROR1-GRB2-c-Fos axis in GSCs maintenance and GBM progression. RESULTS: ROR1 is upregulated in GBM and preferentially expressed in GSCs. Disruption of ROR1 markedly impairs GSC proliferation and self-renewal, and inhibits GBM growth in vivo. Moreover, ROR1 stabilizes GRB2 by directly binding and reducing its lysosomal degradation, and ROR1 knockdown significantly inhibits GRB2/ERK/c-Fos signaling in GSCs. Importantly, ectopic expression of c-Fos counteracts the effects caused by ROR1 silencing both in vitro and in vivo. CONCLUSIONS: ROR1 plays essential roles in GSCs maintenance through binding to GRB2 and activation of ERK/c-Fos signaling, which highlights the therapeutic potential of targeting the ROR1-GRB2-c-Fos axis.