KIAA1199 drives immune suppression to promote colorectal cancer liver metastasis by modulating neutrophil infiltration

Abstract Background and Aims Metastasis is the primary cause of cancer mortality, and colorectal cancer (CRC) frequently metastasizes to the liver. Our previous studies demonstrated the critical role of KIAA1199 in tumor invasion and metastasis in CRC. In the present study, we described an immune regulatory effect of KIAA1199 that creates a permissive environment for metastasis. Approach and Results Flow cytometry was used to examine the effects of KIAA1199 on the infiltration of tumor immune cells. Neutrophils and T cells were isolated, stimulated, and/or cultured for in vitro function assays. In the patients with CRC, high expression levels of KIAA1199 were associated with an increased neutrophil infiltration into the liver. This result was further validated in mouse metastasis models. The increased influx of neutrophils contributed to the KIAA1199‐driven CRC liver metastasis. Mechanistically, KIAA1199 activated the TGFβ signaling pathway by interacting with the TGFBR1/2 to stimulate CXCL1 and CXCL3 production, thereby driving the aggregation of immunosuppressive neutrophils. Genetic blockade or pharmacologic inhibition of KIAA1199 restored tumor immune infiltration, impeded tumor progression, and potentiated response to immune checkpoint blockade (ICB). Conclusions These findings indicated that KIAA1199 could facilitate the liver infiltration of immunosuppressive neutrophils via the TGFβ–chemokine (C‐X‐C motif) ligand (CXCL)3/1–CXCR2 axis, which might be clinically targeted for the treatment of hepatic metastasis.