CD27 and cancer: Through expression analysis, survival analysis, and correlation analysis, we built the upstream regulatory networks of CCNA2 in different cancer types (LINC00997/miR-27b-3p/CCNA2 ceRNA network in KIRC; SNHG16, GUSBP11, FGD5-AS1, LINC00630, CD27-AS1, and LINC00997/miR-22-3p/CCNA2 ceRNA network, miR-29b-3p/CCNA2, miR-29c-3p/CCNA2, and miR-204-5p/CCNA2 networks in LIHC; and miR-218-5p/CCNA2 and miR-204-5p/CCNA2 networks in LUAD).