Galectin-9 expression on tumour-associated immune cells is associated with favourable clinicopathological features and better outcomes in oral squamous cell carcinoma.

Introduction: Galectin-9, a β-galactoside-binding protein, might be a potential target in cancer personalized therapy, but contradicting data exist regarding its prognostic significance in malignancy. Previous studies showed low or absent expression of galectin-9 on tumour cells of oral squamous cell carcinoma (OSCC); thus, we aimed to assess the prognostic impact of its expression on tumour-associated immune cells (TAICs). Material and methods: A retrospective analysis was conducted on 62 patients with OSCC. Tissue microarrays were constructed with chemo- and radiotherapy-naïve tissue samples and stained with anti-galectin-9 antibody. Cytoplasmic reactions in TAICs were counted as positive, and the percentage of galectin-9-positive cells was calculated. Results: The expression of galectin-9 was not associated with any demographic factors, other than diabetes mellitus type 2, for which there were lower levels of expression (p = 0.029). Higher levels of galectin-9 were associated with less locally advanced tumours (p = 0.023) and lack of nodal metastases (p = 0.014). Galectin-9 expression positively correlated with PD-L1 expression on TAICs (p = 0.009). Patients with > 50% galectin-9-positive cells were determined to have a superior 5-year overall survival ( Conclusions: Future studies are necessary to investigate the effects of galectin-9 on the tumour micro-environment, and galectin-9-targeted treatment may be considered, especially with its correlation to PD-L1 in OSCC.