SARI suppresses colitis-associated cancer development by maintaining MCP-1-mediated tumour-associated macrophage recruitment

SARI (suppressor of AP-1, regulated by IFN) impaired tumour growth by promoting apoptosis and inhibiting cell proliferation and tumour angiogenesis in various cancers. However, the role of SARI in regulating tumour-associated inflammation microenvironment is still elusive. In our study, the colitis-dependent and -independent primary model were established in SARI deficiency mice and immuno-reconstructive mice to investigate the functional role of SARI in regulating tumour-associated inflammation microenvironment and primary colon cancer formation. The results have shown that SARI deficiency promotes colitis-associated cancer (CAC) development only in the presence of colon inflammation. SARI inhibited tumour-associated macrophages (TAM) infiltration in colon tissues, and SARI deficiency in bone marrow cells has no observed role in the promotion of intestinal tumorigenesis. Mechanism investigations indicated that SARI down-regulates p-STAT1 and STAT1 expression in colon cancer cells, following inhibition of MCP-1/CCR2 axis activation during CAC development. Inverse correlations between SARI expression and macrophage infiltration, MCP-1 expression and p-STAT1 expression were also demonstrated in colon malignant tissues. Collectively, our results prove the inhibition role of SARI in colon cancer formation through regulating TAM infiltration.