The brain tumor glioblastoma (GB) is an incurable disease and only allows short lifespan after diagnosis. Standard therapeutic approaches that include surgical tumor removal, irradiation and chemotherapy are not very efficiently prolonguing the time of GB recurrence. One of the potential new options is the use of different types of cannabinoids (such as tetrahydrocannabinol and cannabidiol). From published studies it is evident that these substances induce apoptosis and inhibit angiogenesis and invasion of GB. The purpose of this work was to determine the expression of proteins and genes of cannabinoid receptors CB1 and CB2 in GB cells and tissues. Furthermore, we determined the influence of two types of cannabinoid extracts, that contain relatively higher amounts of either tetrahydrocannabinol or cannabidiol, on the viability of established GB cells, GB stem cells and the primary cultures of patient-derived cells. Our results show that different GB cell lines express both CB1 and CB2 receptor proteins, which are also expressed in normal astrocites. In GB stem cell lines, the expression of receptors was also determined by immunofluorescence, and we found significantly high contents of CB1 and CB2. The expression of the GB genes, i.e. CNR1 gene, was detected both in GB cells and in GB tissues. We have confirmed a decrease in the viability of GB cells when Cannabinoid resins were added. GB is a heterogenous tumor and it is possible that they as well differ in the content of cannabinoid receptors. If the levels of receptors coincide with the responsiveness of the patient's cells to the corresponding cannabinoids, a more informed personalized approach of their clinical use could be applied, related to the expression of their receptors.
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