The expression of MDIG may play a key role in cell proliferation.11, 12, 13, 14, 15 Several reports suggest that MDIG is overexpressed in a variety of human cancers,16, 17, 18, 19, 20 including glioblastoma,21 oesophageal squamous cell carcinoma,22 colon cancer,23 lung cancer,24 gastric cancer25, 26 and cholangiocarcinoma.27, 28 In addition, the forced expression of MDIG in NIH/3T3 cells induces cell transformation and produces tumours in nude mice,29 whereas the targeted silencing of MDIG delays cell cycle progression and inhibits cell proliferation. The gene discussed is RIOX2; the disease is cholangiocarcinoma.