G9a is an epigenetic regulator that methylate the lysine 9 of histone 3 and has a role in gene silencing. G9a generally causes repression of gene expression and participates in diverse cellular functions such as DNA repairing, proliferation and differentiation. This gene is overexpressed in some types of cancers include lung, colorectal, endometrial, head and neck cancers. The role of this gene in the basic processes can be used as a therapeutic goal. The purpose of this study was to evaluate the expression of G9a gene in various cancers and cancer related activities in this gene.