CTLA4 and cancer: For instance, the main contributor of CTLA-4 and TIGHT were Tregs across all groups, the CD8+ T subgroups showed decreased expression of PD-1 in KRAS/TP53 dual mutant tumors, and the main contributors of PD-1 in the mutant cancer appeared to be Follicular helper T cells (Tfh cells) (Figure 3G).