Both natural and synthetic cannabinoids have been shown to suppress the growth of tumor cells in culture and in animal models by affecting key signaling pathways including angiogenesis, a pivotal step in tumor growth, invasion, and metastasis. In our search for cannabinoid-like anticancer agents devoid of psychoactive side effects, we synthesized and evaluated the anti-angiogenic effects of a novel series of hexahydrocannabinol analogs. Among these, two analogs LYR-7 [(9S)-3,6,6,9-tetramethyl-6a,7,8,9,10,10a-hexahydro-6H-benzo[c]chromen-1-ol] and LYR-8 [(1-((9S)-1-hydroxy-6,6,9-trimethyl-6a,7,8,9,10,10a-hexahydro-6H-benzo[c]chromen-2-yl)ethanone)] were selected based on their anti-angiogenic activity and lack of binding affinity for cannabinoid receptors. Both LYR-7 and LYR-8 inhibited VEGF-induced proliferation, migration, and capillary-like tube formation of HUVECs in a concentration-dependent manner. The inhibitory effect of the compounds on cell proliferation was more selective in endothelial cells than in breast cancer cells (MCF-7 and tamoxifen-resistant MCF-7). We also noted effective inhibition of VEGF-induced new blood vessel formation by the compounds in the in vivo chick chorioallantoic membrane (CAM) assay. Furthermore, both LYR analogs potently inhibited VEGF production and NF-κB transcriptional activity in cancer cells. Additionally, LYR-7 or LYR-8 strongly inhibited breast cancer cell-induced angiogenesis and tumor growth. Together, these results suggest that novel synthetic hexahydrocannabinol analogs, LYR-7 and LYR-8, inhibit tumor growth by targeting VEGF-mediated angiogenesis signaling in endothelial cells and suppressing VEGF production and cancer cell growth.
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