Effect of CBD on anti-tumor immune response and interaction with GPR55 on MAPK signaling in head and neck squamous cell carcinoma.

Abstract

6060 Background: Head and neck squamous cell carcinoma (HNSCC) is a lethal malignancy and comprises two distinct etiology: human papillomavirus (HPV)+ve and -ve. Marijuana use is associated with HPV+ oropharyngeal infection and conflicting data show positive and negative associations of daily marijuana use with HPV+ and tobacco-associated HPV- HNSCC. However, cannabinoid use continues to increase in the US general population for recreational purposes as well as in cancer patients for palliative care. G-protein coupled receptors (GPCRs), including cannabinoid GPCRs, stimulated by specific ligands interact with multiple G proteins creating diversity and complexity of signaling. In this study, we aimed to investigate the CBD-induced GPCR coupling and its effect on anti-tumor activity by modulating immune response in HNSCC by using pre-clinical models. Methods: The anti-cancer effect of CBD was measured by cell proliferation, apoptosis and migration analysis. Next, TGF-α shedding assay was performed to identify the CBD-induced GPCR coupling with different cannabinoid receptors. The cannabinoid receptor GPR55 was subjected to silencing by siRNA and western blot analysis was performed to evaluate its role in activation of p38 MPAK pathway. Next, the anti-tumor immune response of CBD was evaluated by using an immunocompetent syngeneic C57BL/6 mEER RasG12D+/- HPV E6/E7 transformed tongue epithelial cell model that serves as a model for HPV+ HNSCC and the 4MOSC1 orthotopic, syngeneic, 4NQO (4-nitroquinoline-1 oxide)-induced murine oral tongue squamous cell carcinoma C57BL/6 mouse model that serve as HPV- HNSCC model as well as in immune-deficient Rag1 -/- and athymic nude mouse followed by measurement of immune cell infiltration by IHC analysis. Results: We found that 10μM of CBD treatment inhibited cell proliferation and migration in HNSCC cells by promoting apoptosis. Interestingly, we observed that CBD resulted in GPCR coupling for Gαi with GPR55 and Gαq/o and Gαq/s for CNR1, CNR2 and GPR55. Furthermore, we silenced GPR55 and observed that 10μM of CBD treatment inhibits the activation of p38 MAPK pathway whereas it promotes activation in non-silenced HNSCC cells. Next, we observed that treatment with 10μM of CBD significantly inhibited tumor growth compared to control in both HPV- and HPV+ models in immune-intact animals whereas, no significant difference in the tumor growth was observed in immune-deficient (Rag1 -/- and athymic nude) mouse, indicating role of CBD in modulating tumor immune microenvironment. We also observed CBD treatment enhanced CD4+ and CD8+ T cell infiltration into the primary tumors of HPV+ and HPV- mice models, implicating a downstream cytotoxic T cell response. Conclusions: Our study suggests that CBD promotes anti-tumor activity by modulating the immune microenvironment and interacts with GPR55 to activate intrinsic MAPK signaling pathway.