DDX5 and hepatocellular carcinoma: We also identified and validated ten candidate reference genes respectively for each cancer subtype including PAAD (FTL, OAZ1, FYB1, SERF2, SOD2, PCMTD1, ARPC2, NCOA4, HCLS1 and TYROBP), CRC (B2M, RPL41, SNCA, RPS9, BTF3, ADIPOR1, HEMGN, SOD2, PCMTD1 and NCOA4), and HCC (FTL, OAZ1, CD74, DDX5, PCMTD1, HCLS1, LSP1, RPL9, WIPF1 and H3F3AP4) as well (Suppl.