Cannabis suppresses antitumor immunity by inhibiting JAK/STAT signaling in T cells through CNR2

The binding of checkpoint proteins on the surface of T cells to their partner proteins on healthy cells helps T cells recognise the healthy cells and prevents the immune system from destroying them. However, some cancer cells exploit this system and can also bind to the checkpoint proteins on T cells, stopping the T cells from attacking the cancer cells. Immune checkpoint blockade (ICB), a type of immunotherapy, uses monoclonal antibodies to target specific checkpoint proteins on T cells, helping the immune system recognise and attack cancer cells. Immunotherapy has been widely used with chemotherapy to improve cancer treatment. Δ9-Tetrahydrocannabinol (THC) is the principal component of cannabis that is used to treat the nausea and vomiting caused by chemotherapy. Because THC has been shown to exhibit anti-inflammatory properties, the researchers of the paper sought to investigate if THC interferes ICB treatment. Using mice with conditional knockout of CNR2 (Cnr2CKO) and FLAG tagged CNR2 (Cnr2GFP) in T cells, they showed that THC suppressed the antitumor immunity mediated by T cells through cannabinoid receptor 2 (CNR2) and decreased the efficacy of programmed cell death protein 1 (PD-1) blockade. To identify the signalling pathways regulated by CNR2 in T cells, the RNA sequencing of Cnr2CKO and Cnr2GFP CD8+ T cells was first performed after the activation by anti-CD3 and anti-CD28 antibodies. In Cnr2-deficient T cells, a strong activation of the Janus Kinase (JAK)-signal transducer and activator of transcription (STAT) signalling pathway was found. For example, upregulation of the target genes of the JAK-STAT signaling including Ifnγ, Ifngr1, Il2, Akt2, Ccnd1, Ccnd2, and Socs1 and downregulation of Il6, Il10, or Socs3 were observed. LC-MS/MS was performed to identify proteins that interact with CNR2. JAK1 was identified as one of the top proteins that bind to CNR2 inhibiting downstream STAT signalling, while other top proteins including Myh9, Flna, Alb, Myh10, Atp5o, Eif4b, and Coro1a belong to unspecific cell adhesion proteins. Taken together, this study suggests cannabis and cannabinoid-containing drugs should be avoided during immunotherapy.

How was PEAKS used?

To identify the proteins interacting with CNR2, LC–MS/MS analysis was performed on proteins that were only detected in the mice with FLAG-tagged CNR2. Raw mass spectra were searched against a Uniprot Mouse Database and all MS/MS statistical analyses were performed using PEAKS Studio 8.5.

Xiong X, Chen S, Shen J, You H, Yang H, Yan C, Fang Z, Zhang J, Cai X, Dong X, Kang T, Li W, Zhou P. Cannabis suppresses antitumor immunity by inhibiting JAK/STAT signaling in T cells through CNR2. Signal Transduct Target Ther. 2022 Apr 6;7(1):99. doi:10.1038/s41392-022-00918-y. PMID: 35383142; PMCID: PMC8983672.


The combination of immune checkpoint blockade (ICB) with chemotherapy significantly improves clinical benefit of cancer treatment. Since chemotherapy is often associated with adverse events, concomitant treatment with drugs managing side effects of chemotherapy is frequently used in the combination therapy. However, whether these ancillary drugs could impede immunotherapy remains unknown. Here, we showed that 9-tetrahydrocannabinol (THC), the key ingredient of drugs approved for the treatment of chemotherapy-caused nausea, reduced the therapeutic effect of PD-1 blockade. The endogenous cannabinoid anandamide (AEA) also impeded antitumor immunity, indicating an immunosuppressive role of the endogenous cannabinoid system (ECS). Consistently, high levels of AEA in the sera were associated with poor overall survival in cancer patients. We further found that cannabinoids impaired the function of tumor-specific T cells through CNR2. Using a knock-in mouse model expressing a FLAG-tagged Cnr2 gene, we discovered that CNR2 binds to JAK1 and inhibits the downstream STAT signaling in T cells. Taken together, our results unveiled a novel mechanism of the ECS-mediated suppression on T-cell immunity against cancer, and suggest that cannabis and cannabinoid drugs should be avoided during immunotherapy.