Given the presence of a conserved JmjC domain in its amino acid sequence, mdig was first assumed to be a histone demethylase.4 However, both cellular experiments and test tube reactions revealed that mdig has very marginal histone demethylase activity toward H3K9me3.9,23 Even in breast cancer cells presented in this report, silencing mdig only achieved limited enhancement of H3K9me3. Here, RIOX2 is linked to breast cancer.