CD28 and cancer: We observed a male-biased pattern for patients with kidney renal clear cell carcinoma (KIRC) in TCGA based on immune checkpoints (e.g., CD28 and CD86) and immune cell populations (e.g., active CD4+ T cells) and confirmed this pattern for patients with the same cancer, labeled ccRCC, in one independent data set31 (Supplementary Fig. 7b).