Exploration of Alternative Approaches to Citron Kinase Inhibition for Glioblastoma Treatment

Glioblastoma (GBM) remains a highly aggressive brain tumor with limited therapeutic options, highlighting the need to identify novel tumor vulnerabilities. Citron kinase (CITK), a protein involved in cytokinesis and genome stability, is required for the proliferation and survival of neural progenitors and has previously emerged as a potential therapeutic target in medulloblastoma (MB). Here, we investigated the effects of CITK depletion and pharmacological inhibition in two patient-derived GBM stem cell models. CITK was depleted by siRNA or pharmacologically targeted using the first selective kinase inhibitor so far described, C3TD879 (c879). We also explored the polypharmacological inhibitor Lestaurtinib. Effects on spheroid growth, cytokinesis, cytotoxicity, DNA damage-associated proteins, apoptotic markers, and cell-cycle regulators were assessed. CITK depletion partially impaired spheroid growth, slightly increased multinucleation, and led to cytotoxicity in both GBM models, while effects on DNA damage-associated proteins were cell-line dependent. Selective CITK inhibition with c879 slightly reduced spheroid growth and only partially recapitulated the cellular and molecular effects of CITK depletion. Lestaurtinib produced stronger spheroid growth inhibition and cytokinesis defects, while inducing limited cytotoxicity and heterogeneous molecular responses. In summary, the tested GBM models were shown to be moderately sensitive to CITK depletion and selective catalytic inhibition, while Lestaurtinib showed the strongest effects, which mimicked only in part the effects of CITK loss.