Exploring GBM vulnerabilities by a combinational approach of inhibiting ARHGAP activity and inducing synergetic effects with plant-derived therapeutics

Temozolomide (TMZ) remains the sole cytotoxic chemotherapeutic option in the management of Glioblastoma (GBM), with tumours eventually developing resistance. We recently reported on members of the ARHGAPs, RhoGTPase-activating proteins, and a role in cell plasticity as potential contributors to therapeutic resistance in GBM with clinical relevance for tumour recurrence (Cheng et al, Cell Reports, 2025). We also demonstrated anti-migratory activity of plant-derived compounds in another study leading to disruption of the GBM cytoskeletal architecture (Thompson et al, JoX, 2024). Here, we explored ARHGAP signaling as a vulnerability in GBM to examine how its modulation could enhance TMZ efficacy, while also highlighting the potential for synergy with plant-derived agents. ARHGAP activity and effect on TMZ potentiation with or without the inclusion of a panel of plant-derived compounds was profiled in previously generated stable GBM knockdown cells targeting ARHGAP 12 and 29. The panel of selected plant-derived compounds included curcumin, senna, black cumin, sulforaphane, hesperidin, EGCG, quercetin and tryptanthrin with selective anti-migratory activity. Established 2D and 3D in vitro methodology allowed investigations of effects on proliferation, migration and subcellular cytoskeletal arrangements. ARHGAP activity correlated with TMZ resistance. Knockdown of ARHGAP 12 or 29 sensitized resistant cells to TMZ, leading to a 10-fold increase in sensitivity. Co-treatment with TMZ and plant-derived compounds in particular curcumin enhanced TMZ activity with distinct cytoskeletal effects observed in 3D spheroids in ARHGAP 12 kd spheroids. ARHGAP inhibition in combination with curcumin disrupted actin dynamics supporting a role for the ARHGAPs in resistance pathways. ARHGAP signaling is a functional vulnerability in GBM that contributes to TMZ resistance. Its inhibition potentiates TMZ efficacy and may synergize with selective plant-derived therapeutics. These findings support the rationale for novel combination strategies integrating selective targeting of the cytoskeleton with RhoGTPase modulators and selective inhibitors to overcome GBM therapy resistance.