SFRP4 and neoplasm: These inhibitory chromatin modifications help transcriptional silencing of tumor suppressor genes (e.g., E-cadherin (CDH1), WNT inhibitory factor 1 (WIF1), TIMP metallopeptidase inhibitor 2 (TIMP2), TIMP metallopeptidase inhibitor 3 (TIMP3), mutL homolog 1 (MLH1), cyclin-dependent kinase inhibitor 2A (CDKN2A), secreted frizzled related protein 4 (SFRP4), and secreted frizzled related protein 5 (SFRP5)) [86], which may explain tumor initiation by chronic oxidative stress.