A20 promotes colorectal cancer immune evasion by upregulating STC1 expression to block "eat-me" signal.

Immune checkpoint inhibitors (ICIs) have induced durable clinical responses in a subset of patients with colorectal cancer (CRC). However, the dis-satisfactory response rate and the lack of appropriate biomarkers for selecting suitable patients to be treated with ICIs pose a major challenge to current immunotherapies. Inflammation-related molecule A20 is closely related to cancer immune response, but the effect of A20 on "eat-me" signal and immunotherapy efficacy remains elusive. We found that A20 downregulation prominently improved the antitumor immune response and the efficacy of PD-1 inhibitor in CRC in vitro and in vivo. Higher A20 expression was associated with less infiltration of immune cells including CD3 (+), CD8 (+) T cells and macrophages in CRC tissues and also poorer prognosis. Gain- and loss-A20 functional studies proved that A20 could decrease the "eat-me" signal calreticulin (CRT) protein on cell membrane translocation via upregulating stanniocalcin 1 (STC1), binding to CRT and detaining in mitochondria. Mechanistically, A20 inhibited GSK3β phosphorylating STC1 at Thr86 to slow down the degradation of STC1 protein. Our findings reveal a new crosstalk between inflammatory molecule A20 and "eat-me" signal in CRC, which may represent a novel predictive biomarker for selecting CRC patients most likely to benefit from ICI therapy.