LAG-3 expression in tumor microenvironment of triple-negative breast cancer

Background: This study aimed to evaluate the expression of lymphocyte activation gene-3 (LAG-3) and its relationship with programmed cell death ligand-1 (PD-L1) in triple-negative breast cancer (TNBC).

Methods: : LAG-3 and PD-L1 was evaluated in tumor-infiltrating lymphocytes (TILs) using immunohistochemistry (IHC). The chi-square test was used to estimate the associations between LAG-3, PD-L1 and clinicopathological characteristics. Correlation between LAG-3 stromal TIL (sTIL), LAG-3 intraepitelial TIL (iTIL) and PD-L1 was assessed with using the Spearman's correlation coefficient. Survival analysis was performed using the Kaplan-Meier method.

Results: The percentages of LAG-3 sTIL+, LAG-3 iTIL+, PD-L1+ tumor cells and PD-L1+ inflammatory cells were 52%, 42%, 14% and 70%, respectively. A strong positive correlation between LAG-3 sTIL and LAG-3 iTIL (r = 0.874, p < 0.001) and a moderate positive correlation between LAG-3 sTIL and PD-L1 (r = 0.584, p < 0.001) were found. LAG-3 and PD-L1 status did not significantly affect overall survival (OS) (HR: 0.56 (95% CI: 0.15-2.11) (p = 0.397), HR: 2.70 (95% CI: 0.56-13.02) (p = 0.215), respectively).

Discussion: High levels of LAG-3 and PD-L1 expression were detected in patients with TNBC. Although their contribution to survival could not be determined, the high expression rates of PD-L1 and LAG-3 may help identify the subgroup of TNBC that would benefit from immunotherapy.