Role of JMJD6 in Breast Tumourigenesis

Protein arginine methylation is a common post translational modification that regulates protein properties. This modification is carried out by a family of nine arginine methyltransferases (PRMTs). Arginine methylation has already been linked to tumourigenesis as overexpression of these enzymes was associated with various cancers, notably in breast cancers. Since the Jumonji Domain Containing 6 protein (JMJD6) possesses an arginine demethylase activity able to remove the methyl mark, we wanted to assess its potential role in breast tumourigenesis. The expression of the protein by tissue microarray immunohistochemical staining was performed on a cohort of 133 breast tumours. Using cell lines stably overexpressing or knocked down for JMJD6, we evaluated its role on cell proliferation, cell migration, colony formation and mice tumour xenografts. The analysis of JMJD6 expression in a cohort of breast tumour samples indicates that JMJD6 was highly expressed in aggressive breast tumours. Moreover, high expression of JMJD6 was associated with poor disease-free survival of patients in this cohort. JMJD6 silencing in breast tumoural cells promotes certain characteristics of tumourigenesis including proliferation, migration in vitro, and tumour growth in vivo. These effects are dependent on its demethylase activity as an enzymatic dead mutant lost these properties. Although JMJD6 displays anti-tumoral properties in cell lines, its expression in breast tumours may be a marker of poor prognosis, suggesting that its function could be altered in breast cancer.