Background: High-grade gliomas are malignant brain tumors characterized by aggressiveness and resistance to chemotherapy. Prognosis remains dismal, highlighting the need to identify novel molecular dependencies and targets. Ribosome biogenesis (RiBi), taking place in the nucleolus, represents a promising target as several cancer types rely on high RiBi rates to sustain proliferation. Publicly available transcriptomics data of glioma patients revealed a positive correlation between RiBi rates and histological grades. We, therefore, hypothesized that glioma cells could be susceptible to RiBi inhibition.
Methods: Transcriptomics data from glioma patients were analyzed for RiBi-related processes. BMH-21, a small molecule inhibitor of RNA pol I transcription, was tested in adult and pediatric high-grade glioma cell lines and a zebrafish transplant model. Cellular phenotypes were evaluated by transcriptomics, cell cycle analysis, and viability assays. A chemical synergy screen was performed to identify drugs potentiating BMH-21-mediated effects.
Results: BMH-21 reduced glioma cell viability, induced apoptosis, and impaired the growth of transplanted glioma cells in zebrafish. Combining BMH-21 with TMZ potentiated cytotoxic effects. Moreover, BMH-21 synergized with Fibroblast Growth Factor Receptor (FGFR) inhibitor (FGFRi) Erdafitinib, a top hit in the chemical synergy screen. RiBi inhibition using BMH-21, POLR1A siRNA, or Actinomycin D revealed engagement of the FGFR-FGF2 pathway. BMH-21 downregulated FGFR1 and SOX2 levels, whereas FGF2 was induced and released from the nucleolus.
Conclusions: This study conceptualizes the implementation of RiBi inhibition as a viable future therapeutic strategy for glioma and reveals an FGFR connection to the cellular response upon RiBi inhibition with potential translational value.
Keywords: FGFR1/FGF2 signaling; RNA polymerase I; combination therapy; glioblastoma; ribosome biogenesis.
© The Author(s) 2022. Published by Oxford University Press on behalf of the Society for Neuro-Oncology.