In this regard, the role of Hsp90 seems to be particularly important, since it has been demonstrated to modulate the expression of programmed cell death ligand 1 (PD-L1) and 2 (PD-L2) on the surface of cancer cells and macrophages via STAT3 activation, and the upregulation of the c-Myc oncogene, enabling cancer cells to avoid T-cell-mediated cytotoxicity [277]. This evidence concerns the gene STAT3 and cancer.