Secondly, we and others have shown that Gal-9 concentrations are at a high level in malignant NPC cells in situ, especially in recurrent tumors, in NPC-derived PDX (patient-derived xenograft model) as well as in plasma exosomes from NPC patients12–14, suggesting a role of Gal-9 in tumor progression. This evidence concerns the gene LGALS9 and nasopharyngeal carcinoma.