To explore the APOL4 expression in 33 human cancers (The full names and abbreviations are in Supplementary Materials), we employed the TIMER database, and we found that APOL4 was upregulated in ACC, CHOL, HNSC, LIHC, STAD, and UCEC but downregulated in BRCA, KIRP, LUAD, and LUSC compared with normal tissues (Figure 1A). This evidence concerns the gene APOL4 and cancer.