In addition, ABO gene expression was positively correlated with NFYB (r = 0.38, p < 0.001) and inversely correlated with DNA methylation level of four CpG sites on ABO gene (cg11879188, r = − 0.3, p = 0.002; cg22535403, r = − 0.30, p = 0.002; cg13506600, r = − 0.22, p = 0.025; cg07241568, r = − 0.21, p = 0.049) in ovarian tumor tissues. The gene discussed is ABO; the disease is ovarian neoplasm.