Lymphocyte-activated gene-3 (LAG3) protein expressed in tumor-infiltrating lymphocytes of colorectal cancer.

Immunotherapy can reverse tumor immune escape by suppressing immune checkpoints. Lymphocyte activation gene 3 (LAG3) is an important checkpoint and its role in colorectal cancer is not clear. In this study, we investigated LAG3 protein expression and its correlation with clinicopathologic parameters. The expression of LAG3 protein was assessed in 150 surgically resected colorectal cancer tissue samples by immunohistochemistry. The relationship between LAG3 expression and clinicopathological parameters, MSI status and survival was statistically analyzed. LAG3 protein was not expressed in colorectal cancer cells, and was expressed on the tumor-infiltrating lymphocytes (TILs) in 31 out of 150 (20.7%) colorectal cancer samples. Positive expression of LAG3 in TILs is associated with lymph node metastasis (p < 0.001), TNM stage (p = 0.024) and MSI-H (p = 0.035). No significant relationship was found between LAG3 expression and gender, age, tumor location, tumor invasion depth, and differentiation. LAG3 expression is associated with longer overall survival (p = 0.045). Our data show LAG3 expression on TILs in parts of CRC tissue. Positive expression of LAG3 was associated with advanced tumor stage, MSI-H and a poor prognosis. We conclude that LAG3 is an important checkpoint gene in CRC and may be a potential marker for prognosis of CRC.