CTLA4 and cancer: Correspondingly, activities of Steps 1 (release of cancer cell antigens) and 4 (trafficking of immune cells tumors) were upregulated in cluster 1; however, activities of Steps 2 (cancer antigen presentation), 6 (recognition of cancer cells by T cells), and 7 (killing of cancer cells) were downregulated (Figure 2K), while the expression of most immune checkpoint genes, including PD-L1, PD-1, CTLA-4, LAG-3, TIGIT, TIM-3, CD80, CD200, and CD276, was markedly upregulated, but only the expression of PVR was downregulated in cluster 1 (Figure 2L).