By using rat models of acute myelogenous leukemia, researchers found that Gal-9 knock-out decreased the accumulation of Tregs and promoted PD-1 and TIM-3 level on CD8(+) lymphocytes.49 In breast cancer cell lines, cell adhesion was promoted by Gal-9, from which Gal-9 showed its function in anti-metastasis.50 51 Moreover, Gal-9 exhibited its function in activating apoptosis of tumor cells by complicated signaling pathways. Here, HAVCR2 is linked to breast cancer.