CD274, LAG3, and IDO1 expressions in tumor-infiltrating immune cells as prognostic biomarker for patients with MSI-high colon cancer.

PURPOSE: This study attempted to reveal the prognostic impact of microsatellite instability-high (MSI-H) colon cancer with tumor-infiltrating immune cells (TIICs) and immune checkpoint protein expression, which are good candidates for immunotherapy.

MATERIALS AND METHODS: The study included 89 patients with MSI-H colon cancer who underwent curative surgery at Kyungpook National University Chilgok Hospital. The expression status of specific inhibitory receptors, such as CD274 (programmed death-ligand 1, PD-L1), PDCD1 (programmed cell death 1, PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), lymphocyte-activation gene 3 (LAG3), and indolamine 2'3'-dioxygenase 1 (IDO1), was retrospectively analyzed using immunohistochemistry (IHC).

RESULTS: Among the 89 patients, CD274, LAG3, and IDO1 expressions in TIICs were observed in 68.6% (61 cases), 13.5% (12), and 28.1% (25) of patients, respectively. Meanwhile, CD274, CTLA4, and IDO1 were expressed in tumor cells of 24.7% (22 cases), 4.5% (4), and 72.0% (64) of patients, respectively. During the median follow-up duration of 39 months, 14 (15.7%) patients experienced disease recurrence. Among the five immune checkpoint proteins, CD274, LAG3, and IDO1 expressions in TIICs were significantly associated with a better disease-free survival (DFS) in a univariate analysis (P = 0.028, 0.037, and 0.030 respectively). Moreover, co-expression of CD274, LAG3, and IDO1 in TIICs showed an even better survival for DFS (P = 0.010). In a multivariate survival analysis, CD274, LAG3, and IDO1 expressions in TIICs remained as independent prognostic factors for a better DFS.

CONCLUSION: CD274, LAG3, and IDO1 expressions in TIICs showed a better prognosis for patients with MSI-H colon cancer. Thus, the potential therapeutic implications of these immune checkpoint molecules should be further investigated.