As the expression level of the ICOS, TIGIT, TNFRSF8, and CD8A genes were decreased in the ovarian cancer samples (Figure 1, Supplementary S2), the researchers categorized patients into the high-expression (H) and low-expression (L) groups based on the density distribution of the gene expression levels (Supplementary S5), considering the deviation from the first main distribution interval (i.e., density peak) as a threshold (red vertical line in Supplementary S5) for categorizing the genes into the high- (H-) and low- (L-) expression groups. Here, ICOS is linked to ovarian cancer.