Cannabidiol Induces Apoptosis and Perturbs Mitochondrial Function in Human and Canine Glioma Cells

Abstract

Cannabidiol (CBD), the major non-psychoactive compound found in cannabis, is frequently used both as a nutraceutical and therapeutic. Despite anecdotal evidence as an anticancer agent, little is known about the effect CBD has on cancer cells. Given the intractability and poor prognoses of brain cancers in human and veterinary medicine, we sought to characterize the in vitro cytotoxicity of CBD on human and canine gliomas. Glioma cells treated with CBD showed a range of cytotoxicity from 4.9 to 8.2 μg/ml; canine cells appeared to be more sensitive than human. Treatment with >5 μg/ml CBD invariably produced large cytosolic vesicles. The mode of cell death was then interrogated using pharmacologic inhibitors. Inhibition of apoptosis was sufficient to rescue CBD-mediated cytotoxicity. Inhibition of RIPK3, a classical necroptosis kinase, also rescued cells from death and prevented the formation of the large cytosolic vesicles. Next, cellular mitochondrial activity in the presence of CBD was assessed and within 2 hours of treatment CBD reduced oxygen consumption in a dose dependent manner with almost complete ablation of activity at 10 μg/ml CBD. Fluorescent imaging with a mitochondrial-specific dye revealed that the large cytosolic vesicles were, in fact, swollen mitochondria. Lastly, calcium channels were pharmacologically inhibited and the effect on cell death was determined. Inhibition of mitochondrial channel VDAC1, but not the TRPV1 channel, rescued cells from CBD-mediated cytotoxicity. These results demonstrate the cytotoxic nature of CBD in human and canine glioma cells and suggest a mechanism of action involving dysregulation of calcium homeostasis and mitochondrial activity.

Clinical and Biological Significance of a Necroptosis-Related Gene Signature in Glioma

“…This result effectively explains the phenomenon of the high-risk population having a higher immune infiltration score and a poorer prognosis. Although previous experimental research revealed that necroptosis kills cancer cells and exerts antitumor effects in glioma ( 37 – 40 ), necroptosis did not improve the glioma patients’ prognosis and some research showed that necroptosis-related genes were unfavorable prognostic markers in gliomas ( 26 , 41 ). We believed that necroptosis exerted an anti-tumor effect to promote glioma cells’ death, conversely, tumor cells released a variety of immunosuppressive cytokines and chemokines and necrotic tumor cells also attracted a variety of immune cells infiltrating.…”

Influence of Inhibition of COX-2-Dependent Lipid Metabolism on Regulation of UVB-Induced Keratinocytes Apoptosis by Cannabinoids

“…In addition, the same factor may act in a pro-apoptotic way in one case, while in another the action may be anti-apoptotic. This situation applies, inter alia, to cannabinoids that induce apoptosis in some cases and act cytoprotectively in others [ 33 , 34 , 35 ]. It is believed that this may be due to the different expression of the receptors as well as the different activities of enzymes and regulatory proteins in different cells.…”

“…On the other hand, exocannabinoids are believed to be potential medicinal agents used in the therapy of diseases in which apoptosis is dysregulated. Still, both endo- and exocannabinoids may act in a pro- or an anti-apoptotic manner, depending on the targeted cells [ 33 , 34 , 35 ]. It is believed that this may be due to the different expression of receptors as well as the different activities of enzymes such as COX-2 and the regulatory proteins in different cells.…”

Cannabidiol and Other Phytocannabinoids as Cancer Therapeutics

“…The highest number of in vitro studies have been performed on tumour cells of the nervous system, followed by tests on breast cancer cell lines. IC 50 values of pure CBD varied widely from about 0.6 µM to more than 22 µM for tumours of the nervous system, and were more effective than CBD-E, THC or CBG [15][16][17][18][19][20]. In ependymoma cell lines, CBD and THC were similarly effective, whereas CBD was more potent in medulloblastoma [20].…”

“…Even small differences in the composition can have a pronounced impact on cytotoxicity. A recent study compared pure CBD (>99.9%) with almost pure CBD-E (96%) and found that all four glioma cell lines tested (two human glioma cell lines U87MG and U373MG; two canine glioma cell lines J3TBG and SDT3G) were marginally more sensitive to pure herbal CBD than to CBD-E [15].…”