Author: Chinonso Ibeagwa
Ibeagwa, Chinonso, 2025 The effects of medicinal cannabis on the sensitivity of glioblastoma cell lines to Chemotherapy, Flinders University, College of Medicine and Public Health
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Glioblastoma is the most lethal primary brain tumour in adults and remains a major challenge in neuro-oncology. Despite multimodal treatment involving maximal surgical resection, radiotherapy and temozolomide (TMZ) chemotherapy, GBM clinical outcomes remain poor due to extensive tumour heterogeneity, rapid proliferation, high invasiveness and acquired drug resistance. Therefore, there is a critical need to identify novel therapeutic agents capable of enhancing chemotherapy response and overcoming drug resistance mechanisms. Emerging evidence suggests that cannabinoids, including cannabidiol (CBD), cannabigerol (CBG), and Δ⁹-tetrahydrocannabinol (THC), may reduce tumour cell viability and enhance sensitivity to chemotherapeutic agents through endocannabinoidome-mediated signalling.
This study investigated the cytotoxic and chemosensitizing potential of seven purified cannabinoids and phytocannabinoid extracts obtained from ten cannabis strains in three established human GBM cell lines (U87, U251 and TMZ-resistant T98G). Phytochemical profiling using HPLC-MS/MS confirmed that the cannabis extracts differed significantly in their cannabinoid composition. Cell viability assays (Hoechst staining) revealed that both purified cannabinoids and extracts induced cytotoxicity in all three cell lines, with T98G showing notable sensitivity despite its TMZ-resistant phenotype. Among the purified cannabinoids tested, CBD and CBG demonstrated the greatest potency based on CC₅₀ values, while the Poddy Mouth and The Wife extracts showed the strongest cytotoxic effects among the cannabis extract treatments. Annexin-V/PI flow cytometry assay was further used to confirm that cannabinoid-induced cell death occurred primarily through apoptosis.
Differential responses between cell lines prompted analysis of key endocannabinoid-associated genes via RT-qPCR. All three cell lines exhibited low to undetectable CNR2 (CB2 receptor) expression, while CNR1 (CB1 receptor) was undetectable in T98G, potentially contributing to its altered drug sensitivity profile. Combination assays of the cannabinoids and extracts with TMZ demonstrated an increase in cytotoxicity across all cell lines, with the most pronounced enhancements observed in TMZ-resistant T98G cells, suggesting an additive chemosensitisation effect.
In conclusion, this study provides evidence that the purified cannabinoids and the phytocannabinoid-rich extracts exert anti-GBM activity and may enhance the cytotoxic effects of TMZ, including in TMZ-resistant models. Future research should focus on elucidating the precise mechanism of action of these cannabinoids down to the receptor level and also include pre-clinical models that take into consideration the complexity of the tumour microenvironment.
Keywords: Cannabinoids, Glioblastoma, Temozolomide, Chemotherapy, TMZ-resistant, Phytocannabinoids, Endocannabinoid system.
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2025
School: College of Medicine and Public Health
Supervisor: Simon Conn