HOXD9 and cholangiocarcinoma: In total 23 genes (hMLH1, RIZ1, Trop2, ERBB2, EBF1, OPCML, HOXA9, HOXD9, HTATIP2, UCHL1, p14ARF, p15INK4b, p16INK4a, EZH2, SUZ12, H3K27, PTEN, H1C1, PRC2, DKK1, DCR1, HIC1, SFRP1) identified in Ov-CCA epigenetic alterations were subjected to gene set enrichment analysis (Fig 3A).