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). This evidence concerns the gene MAD2L1 and small cell osteogenic sarcoma.