Expression and clinical significance of LAG-3, FGL1, PD-L1 and CD8+T cells in hepatocellular carcinoma using multiplex quantitative analysis

Background Fibrinogen-like protein 1 (FGL1)-Lymphocyte activating gene 3 (LAG-3) pathway is a promising immunotherapeutic target and has synergistic effect with programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1). However, the prognostic significance of FGL1-LAG-3 pathway and the correlation with PD-L1 in hepatocellular carcinoma (HCC) remain unknown. Methods The levels of LAG-3, FGL1, PD-L1 and cytotoxic T (CD8(+)T) cells in 143 HCC patients were assessed by multiplex immunofluorescence. Associations between the marker's expression and clinical significances were studied. Results We found FGL1 and LAG-3 densities were elevated while PD-L1 and CD8 were decreased in HCC tissues compared to adjacent normal liver tissues. High levels of FGL1 were strongly associated with high densities of LAG-3(+)cells but not PD-L1. CD8(+)T cells densities had positive correlation with PD-L1 levels and negative association with FGL1 expression. Elevated densities of LAG-3(+)cells and low levels of CD8(+)T cells were correlated with poor disease outcome. Moreover, LAG-3(+)cells deteriorated patient stratification based on the abundance of CD8(+)T cells. Patients with positive PD-L1 expression on tumor cells (PD-L1 TC+) tended to have an improved survival than that with negative PD-L1 expression on tumor cells (PD-L1 TC-). Furthermore, PD-L1 TC(-)in combination with high densities of LAG-3(+)cells showed the worst prognosis, and PD-L1 TC(+)patients with low densities of LAG-3(+)cells had the best prognosis. Conclusions LAG-3, FGL1, PD-L1 and CD8 have distinct tissue distribution and relationships with each other. High levels of LAG-3(+)cells and CD8(+)T cells represent unfavorable and favorable prognostic biomarkers for HCC respectively.