Although the drugs used are likely to impact processes other than proliferation, which might lead to confounding effects on H3K27me3 homeostasis, these data suggest that, in spite of higher EZH2 levels, the PRC2 complex might not be able to match the abnormally high proliferation of breast cancer cells, leading to down-regulation of H3K27me3. This evidence concerns the gene EZH2 and breast carcinoma.