PDCD1 and cancer: In most cancers, except DLBC, ESCA, READ, SARC and UCS, ACTB expression was significantly correlated with the expression levels of known immune checkpoints including lymphocyte-activation gene 3 (LAG3), CD40, cytotoxic T-lymphocyte-associated protein 4 (CTLA4), CD80, programmed cell death 1 (PDCD1), programmed cell death 1 ligand 2 (PDCD1LG2), T cell immunoreceptor with Ig and ITIM domains (TIGIT), CD86 and tumor necrosis factor receptor superfamily, member 9 (TNFRSF9) (Figure 6(a)), indicating a possible cooperation of ACTB with recognized immune checkpoints.