Single-cell analyses reveal cannabidiol rewires tumor microenvironment via inhibiting alternative activation of macrophage and synergizes with anti-PD-1 in colon cancer

Colorectal tumors often create an immunosuppressive microenvironment that prevents them from responding to immunotherapy.Cannabidiol(CBD)is a non-psychoactive natural active ingredient from the cannabis plant that has various pharmacological effects,including neuroprotective,antiemetic,anti-inflammatory,and antineoplastic activities.This study aimed to elucidate the specific anticancer mechanism of CBD by single-cell RNA sequencing(scRNA-seq)and single-cell ATAC sequencing(scATAC-seq)technologies.Here,we report that CBD inhibits colorectal cancer progression by modulating the suppressive tumor microenvironment(TME).Our single-cell transcriptome and ATAC sequencing results showed that CBD suppressed M2-like macrophages and promoted M1-like macrophages in tumors both in strength and quantity.Furthermore,CBD significantly enhanced the interaction between M1-like macrophages and tumor cells and restored the intrinsic anti-tumor properties of macrophages,thereby preventing tumor progression.Mechanistically,CBD altered the metabolic pattern of macrophages and related anti-tumor signaling pathways.We found that CBD inhibited the alternative activation of macrophages and shifted the metabolic process from oxidative phosphorylation and fatty acid oxidation to glycolysis by inhibiting the phosphatidylinositol 3-kinase-protein kinase B signaling pathway and related downstream target genes.Furthermore,CBD-mediated macrophage plasticity enhanced the response to anti-programmed cell death protein-1(PD-1)immunotherapy in xenografted mice.Taken together,we provide new insights into the anti-tumor effects of CBD.