Surgery (Austin & Northern Health) - Theses
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ItemThe effects of cannabinoid derivatives on pancreatic cancer( 2019)Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignant solid tumours and its treatment has not been efficiently improved during the last decade. The overall 5-year survival rate of pancreatic cancer is 9%, which is expected to become the second major cause of cancer-related mortality by 2030. Chemotherapy has been used as the main treatment of choice in the majority of patients bearing either locally advanced or metastatic tumours. Gemcitabine alone or gemcitabine-based combination chemotherapy is commonly used worldwide for the treatment of pancreatic cancer. The poor treatment response to chemotherapy might be related to a dense stroma that is associated with these cancers. However, more effective treatment techniques and novel targets are urgently needed to improve the treatment response. Plant-derived cannabinoids have been used for medical purposes for over a thousand years. The main active cannabinoid components are tetrahydrocannabinol (THC) and cannabidiol (CBD) that are obtained from Cannabis sativa and Cannabis indica. THC exerts its effects via a receptor dependent mechanism, while CBD can act through a receptor and receptor independent mechanisms. CBD can modulate the adverse effects of THC such as its psychoactive effects. To date, three cannabinoids receptors have been identified, CB1, CB2, and GPR55, which are located on the cell membrane and members of the G-protein coupled receptor (GPCR) family. Cannabinoid receptors play an important role in biological and pathological activities such as inflammation, oxidative stress, metabolism, fibrosis, appetite control, memory and emotion. The main aims of this study were to look at the expression of cannabinoid receptors in pancreatic cancer cell lines and pancreatic cancer specimens, detect the correlation of cannabinoid receptors expression with patient’s outcome, determine the effect of cannabinoids alone or in combination with chemotherapy on pancreatic cancer cells in vivo and in vitro. Methods: Western blot assay, SRB-assay, immunohistochemistry staining, wound healing assay and an animal model were the main methods used in this study. Results: The expression of CB1 and CB2 receptors were shown in all the human and murine pancreatic cancer cell lines, stellate cells, and the gemcitabine resistant cell lines. The significant correlation between high expression of GPR55 and worsened PDAC patients’ outcome were demonstrated. In addition, the positive surgical margin and moderate to dense stromal status are associated with a poorer and prolonged survival in patients, respectively. Both CBD and THC dose-dependently inhibited cell proliferation of pancreatic cancer cells, although CBD was more effective than THC. All the different combination ratios of CBD to THC showed significant effects on the inhibition of cancer cell proliferation compared with a single treatment of drugs, although a 1:1 ratio of THC to CBD demonstrated the maximal inhibitory effect on cell proliferation and migration. Synergistic inhibition was observed for combined THC and CBD treatments, and when THC/CBD was combined. with gemcitabine (combination index < 1; using the Chou-Talalay method). In this study, cannabis oil, which contained a 1:1 ratio of CBD to THC and other cannabinoid components has been used for in vitro and in vivo experiments. The effects of this oil on pancreatic cancer cell proliferation and migration was less than either the pure CBD or THC alone. Moreover, cannabis oil alone or in combination with gemcitabine did not significantly inhibit tumour growth in a xenograft model. Bioavailability and absorption patterns of this oil are unknown and further studies are required. Conclusion: Cannabinoid receptors are highly expressed in pancreatic cancer cell lines. The high intensity of GPR55 was correlated with poor patients’ outcome. The 1:1 ratio of THC to CBD provided a significant inhibitory effect on pancreatic cancer proliferation and migration. Combination of cannabinoids with gemcitabine had a synergistic effect on pancreatic cancer inhibition in in vitro study. The cannabis oil used in our in vitro study showed a lesser effect on blocking proliferation and migration of cancer cells than purified THC and CBD. We could not determine the clinically significant effect on pancreatic cancer in our in vivo study using cannabis oil. No absorption characteristics of studied cannabis oil have been reported, therefore more in vivo bioavailability studies are required for the future work.