Loss of Trefoil Factor 1 Accelerates the Immune Response to Colorectal Cancer.

ABSTRACT

BACKGROUND/AIM: Recent studies suggest that PD-L1 expression in immune cells, rather than tumor cells, plays a key role in tumor immunity. Trefoil factor family 1 (TFF1) is a secreted protein expressed mainly by the gastrointestinal epithelium and is related to the development of malignant disease. This study investigated the effects of TFF1 on tumor immunity in a xenograft mouse model of colorectal cancer (CRC). MATERIALS AND METHODS: MC38 cells were implanted in wild-type (WT) and TFF1KO mice, and the tumor micro-environment was investigated using immunohistochemistry. The circulating immune cells were analyzed using flow cytometry. RESULTS: Tumor growth was suppressed in TFF1KO mice. In the tumor microenvironment, CD8- and CD4-positive T cells and CD11c-positive dendritic cells (DCs) were frequently found in TFF1KO mice. When an immune checkpoint inhibitor was administered to these mice, almost half of the tumors in TFF1KO mice showed a complete response. The number of circulating PD-L1/DCs was markedly associated with tumor volume, with TFF1 deletion accelerating this effect and its injection decreasing it. These findings indicate that loss of TFF1 activates tumor immunity via frequent T-cell priming by DCs, and eventually suppresses tumor growth in CRC. In addition, the number of circulating PD-L1/DCs was identified as a predictive marker of checkpoint-inhibiting therapy efficacy. CONCLUSION: Loss of TFF1 resulted in accelerated immune response to colorectal cancer. Further studies are needed to investigate the precise mechanisms of TFF1 in immunotolerance and develop a novel TFF1-inhibiting immunotherapeutic strategy for CRC.