The protein, expressed on macrophages and tumor cells, is considered as an important target in oncology because, on the one hand, high Gal-9 expression correlates with poor prognosis in multiple human cancers and, on the other hand, an anti-Gal-9 antibody has been shown to selectively expand intratumoral TIM-3+ cytotoxic CD8 T cells and immunosuppressive regulatory T cells [117]. This evidence concerns the gene LGALS9 and cancer.