TIGIT and melanoma: Dysfunctional CD8+ T cells are characterised by expressing different inhibitory molecules, such as LAG3, PDCD1 (encoding PD-1), CXCL13, HAVCR2 (encoding Tim3), ENTPD1 (encoding CD39), CTLA4, and TIGIT, which are all less expressed in memory-like T cells in melanoma [71,72].