To assess the effect of galectin-9 in protecting breast cancer cells against cytotoxic cell-dependent killing we co-cultured MCF-7 cells (adherent) with cytotoxic ALL-derived TALL-104 CD8-positive T lymphocytes (we used these rather than NK cells since mainly T cells infiltrate solid tumors; as NK cells, TALL-104 cells express Tim-3, and not galectin-9) for 16 h at a ratio of 4 MCF-7 cells: 1 TALL-104 cells (Figure 5A—this ratio was selected experimentally to achieve moderate effects in order to be able to trace biochemical mechanisms). The gene discussed is LGALS9; the disease is acute lymphoblastic leukemia.