G9a, mainly catalyzes histone H3K9 methylation, is shown to be overexpressed in many types of cancers, including gastric cancer, ovarian cancer, head and neck cancer, etc. Higher G9a expression levels represent higher methylation levels, thus leading to the transcriptional repression of tumor-suppressor genes and are also associated with poor prognosis in patients25. This evidence concerns the gene EHMT2 and ovarian cancer.