CD28 and cancer: The immune checkpoint stimulatory genes affect various TCGA cancer types among different clusters, including BLCA, BRCA, CESC, ESCA, GBM, HNSC, KIRP, KIRC, LGG, LUAD, LUSC, LIHC, OV, PRAD, PAAD, PCPG, READ, STAD, SKCM, THCA, TGCT, and UCEC; BTN3A1, BTN3A2, CD28, ENTPD1, HMGB1, and TLR4 are the most affected tumor types (Figure 7C).