GSK3B and breast cancer: Since GSK3β-mediated phosphorylation of EZH2 did not affect EZH2 expression level but reduce H3K27 trimethylation, and it is known that Ser9 phosphorylation can inactivate GSK3β activity and the measurement of Ser9 phosphorylation can be used to determine GSK3β inactivation [25], we compared expression of H3K27 trimethylation with level of GSK3β phosphorylation at Ser9 in tumor tissue samples from 110 breast cancer patients.