CD28 and neoplasm: Many downregulated genes in tumour‐infiltrating peripheral CD8+ T cells are associated with classical IFN responses (IFI6, IFI27, MX1, STAT1, EPSTI1 PARP9, ISG15), cell proliferation (STMN1, CENPF, HELLS, NUSAP1, and DNPH1), and T cell costimulation (CD28, TMIGD2, TNFRSF4, CD27, and TNFRSF18).