Serum Galectin-9 mirrors immune-evasive microenvironment and predicts early recurrence in hepatocellular carcinoma.

Background: The precise role of Galectin-9, an immune checkpoint protein involved in immune responses, in hepatocellular carcinoma (HCC) remains elusive. Importantly, the prognostic value of serum Galectin-9 has not been clarified, and its association with infiltrating immune characteristics was unclear.

Methods: The association between serum Galectin-9 concentration and HCC recurrence was analyzed in two cohorts of HCC patients (training 133; validation 97) who received curative resection during 2018 and 2019. Bioinformatic analyses, including WGCNA, GSEA, GO, KEGG, Hallmark, CIBERSORT, QUANTISEQ, ssGSEA and TISIDB, were performed to systematically demonstrate the expression pattern, immunomodulation role, and prognostic value of Galectin-9 in HCC. These findings were further validated by immunohistochemistry staining.

Results: Patients with high serum Galectin-9 levels had significantly shorter time to tumor recurrence (TTR; P < 0.001) in both cohorts, and serum Galectin-9 was identified as an independent predictor of HCC recurrence, even in patients with low-AFP or early-stage. Bioinformatic analyzes revealed high Galectin-9 expression is involved in immune-evasive and inflammatory signaling pathways. It correlated with increased infiltration of exhausted CD8 + T cells, Tregs, TAMs and MDSCs. Interestingly, we found Galectin-9 was predominantly expressed on macrophages rather than malignant cells, and showed positively association with serum Galectin-9 concentration according to IHC results. Concordantly, high serum Galectin-9 levels also reflected an immune-evasive microenvironment composed by extensive CD163 + and FOXP3 + cell infiltrates.

Conclusions: Elevated serum Galectin-9 was a novel indicator for worse prognosis in HCC. The high expression of Galectin-9 may reflect the immunosuppressive environment by increasing CD163 + and FOXP3 + cell infiltrates.