 The other 10 cases of loss of PMS2 expression were likely due to epigenetic overexpression of the microRNA, miR-155, which down-regulates MLH1.In cancer epigenetics (see section Frequencies of epimutations in DNA repair genes), there is a partial listing of epigenetic deficiencies found in DNA repair genes in sporadic cancers.These include frequencies of between 13–100% of epigenetic defects in genes BRCA1, WRN, FANCB, FANCF, MGMT, MLH1, MSH2, MSH4, ERCC1, XPF, NEIL1 and ATM located in cancers including breast, ovarian, colorectal and head and neck.