The SLC genes that demonstrated a significant correlation with PD-L1 (PD-L1-related SLC genes, denoted as PRSGs, |scc| > 0.3 and p < 0.05) were found to be specific to certain cancer types (Fig. S2), with 46 SLCs shared by at least 10 cancer types (Table S6). This evidence concerns the gene CCL21 and cancer.