Since proliferation was found to be the main feature of retinoblastoma, we then performed functional enrichment analysis for each subgroup and found that the unique functions of subgroup c7, 8 were related to cell cycle (Fig. 3E), which was further supported by the specific expression of cell cycle genes: CCNA2 and CCNB1 (Fig. 3F). This evidence concerns the gene CCNA2 and retinoblastoma.