WIF1 and neoplasm: In a gene expression profiling study of NPC initial tumor, the promoter of Wnt signalling inhibitor including secreted frizzled related protein 1 (SFRP1), SFRP2, SFRP4, SFRP5, Wnt inhibitory factor 1 (WIF1), and dickkopf WNT signalling pathway inhibitor 1 (DKK1) were turned off by DNA methylation, thus leading to abnormal activation of Wnt signalling and its downstream components [321].