Quantitative real-time PCR revealed that BRCA1, RAD51, BIRC5, CDC6, E2F1, MCM4, CDC20, TUBA4A, TUBG1, CCNA1, CCNB1, CCNA2, CHEK1, TOPBP1, MAD2L1, CDT1, HIST3H3, CDK1, BLM, CCNE1, and UBE2C were significantly downregulated in patients with SCOS, compared with normal patients (Fig. 3A). The gene discussed is CCNA1; the disease is small cell osteogenic sarcoma.