virus cellular receptor 2 (HAVCR2), is a negative immune checkpoint mole cule expressed on a variety of immune cells including T cells [5], dendritic cells [6], and macrophages [7]. Accumulating evidence demonstrate that Tim-3 can reduce cell proliferation, decrease the production of effective cytokines and increase apoptosis of effector T cells, through interaction with its ligands including galectin-9, high mobility group protein B1 (HMGB1), carcinoembryonic antigen related cell adhesion molecule 1 (CEACAM-1) and phosphatidylserine [8,9].Tim-3 is now considered as a critical mediator in cancer pro gression and attracts considerable attention as a therapeutic target. Blocking Tim-3 indeed shows some promising results in multiple preclinical cancer models [10]. More importantly, there is evidence suggesting that resistance to anti-CTLA-4 (cytotoxic T-lymphocyte-associated antigen 4) or anti-PD-1/PD-L1 inhibitors is partially by compensatory upregulation of additional immune checkpoints including Tim-3 [11]. And co-blockade of PD-1 and Tim-3 shows a significant survival advantage in a lung cancer mouse model [12]. These findings support the view that Tim-3 may be a potential target for tumour therapy.Interestingly, Tim-3 is not only expressed on immune cells but also overexpressed on many types of malignant tumours. In vitro findings revealed that Tim-3 promoted metastasis of esophageal squamous cell carcinoma (ESCC) by inducing epithelial-mesenchymal transition (EMT) via the Akt/GSK-3/Snail signalling pathway. Tim-3 knockdown markedly inhibited proliferation, migration, and invasion of ESCC cell lines [13]. Additionally, Interfering Tim-3 expression can significantly suppress osteosarcoma cell proliferation and metastasis via the NF-κB/Snail signalling pathway and EMT [14].Recently, a study in liver cancer indicated that tumour cell-intrinsic Tim-3 promotes cell proliferation via the NF-κB/IL-6/STAT3 cascade signalling axis [15]. Clinically, The ectopic expression of Tim-3 in tumour cells were correlated with more advanced pathologic T classification in non-small-cell lung carcinoma [16], lymph-vascular invasion in gastric cancer [17], lung metastasis in clear cell renal cell carcinoma [18], and lymphatic metastasis in colon cancer [9]. A meta-analysis revealed that higher expression of Tim-3 in solid tumours had significantly shorter overall survival [19]. Therefore, Tim-3 has been depicted as a prognostic indicator for those cancer patients. But contradictory results were also reported in terms of the role of Tim-3. Down-regulated Tim-3 promotes invasion and metastasis