Cannabidivarin directly targets the immunosuppressive activity of regulatory myeloid cells in tumors

Immunosuppression within the tumor microenvironment (TME) is a major obstacle for effective cancer immunotherapy. This is largely driven by myeloid suppressor cells, specifically Myeloid-Derived Suppressor Cells (MDSCs) and Tumor-Associated Macrophages (TAMs), which create an environment that inhibits the immune response. The presence of these cells is strongly correlated with poor patient outcomes and resistance to treatment, highlighting the need for new strategies to mitigate their effects. In this study, we investigated the therapeutic potential of Cannabidivarin (CBDV), a less-studied non-psychoactive cannabinoid, to reprogram these immunosuppressive cells. We found that CBDV directly targets myeloid suppressor cells, significantly impairing their immunosuppressive function both in vitro and in vivo. Mechanistically, CBDV reduces the key immunosuppressive markers inducible, Nitric Oxide Synthase (iNOS) and Arginase-1 (Arg-1) in murine MDSCs and promotes the differentiation of TAMs into M1-like macrophages. This shift in myeloid cell function leads to restored CD8 + T-cell proliferation and activation. Furthermore, our results show that CBDV treatment in tumor-bearing mice reduces tumor progression and improves the anti-tumor immune response within the TME. We also confirmed the clinical relevance of our findings, demonstrating that CBDV effectively reduces the immunosuppressive phenotype of human-derived myeloid cells. Altogether, these results establish CBDV as a new immunotherapeutic agent that directly neutralizes myeloid suppressor cells, thereby enhancing the immune system's response against cancer.