Ectopic expression of LAG-3 in non-small-cell lung cancer cells and its clinical significance.

Background Lymphocyte activation gene 3 (LAG-3, also known as CD223) is an immune checkpoint molecule expressed on various types of lymphocytes, and it is mainly involved in maintaining immune homeostasis. However, there are currently no data on LAG-3 expression in non-small-cell lung cancer cells. Methods Human lung cancer cells were cultured using conventional methods. The expression of LAG-3 was measured by Western blot and flow cytometry. Between April 2018 and May 2019, we collected 52 surgical specimens of stage I-III non-small-cell lung cancer (NSCLC). Fourteen samples of benign lung tissue lesions were collected as the control group, and the expression levels of LAG-3 in the lung cancer cells and tissue samples were measured via immunohistochemistry. Results Western blots showed that LAG-3 was expressed in lung cancer cell lines. There was significant difference in the LAG-3 expression levels in the NSCLC cells and benign lung tissue (chi(2) = 13.055, P = .0003). The LAG-3 expression level was significantly associated with the NSCLC clinical stage, and LAG-3 expression was significantly higher in stage III patients (P < .05). Conclusion LAG-3 is expressed in NSCLC tumor cells. Furthermore, LAG-3 not only is expressed in tumor-infiltrating lymphocytes in NSCLC patients but also is ectopically expressed in tumor cells and associated with TNM stage.