Fátima Liliana Monteiro1, André Góis1,2, Inês Direito1, Tânia Melo2, Rosário Domingues2, and Luisa Helguero1
SETD7 is a lysine methyltransferase that targets many proteins with relevance to breast cancer and mammary epithelial biology such as ERα, E-cadherin, beta-catenin and STAT3. However, effects mediated by SETD7 in normal mammary epithelial cells (MEC) remain to be investigated. Our aim was to study SETD7 activity on cell proliferation, epithelial and lactogenic differentiation in two mouse MEC lines (HC11 and EpH4). HC11 and EpH4 were cultured to obtain functionally differentiated/lactogenic (DIF) cells. SETD7 catalytic inhibition was achieved using 8 nM of (R)-PFI-2 for 24h. Cell proliferation was evaluated by cell counting, epithelial cell differentiation by E-cadherin and beta-catenin levels and localization, lactogenic differentiation by qPCR of igfbp5, lactoferrin expression and by beta-casein levels, as well as TLC and GC-FID to characterize lipid composition. SETD7 mRNA and protein levels are induced upon lactogenic differentiation. In DIF cells, inhibition of SETD7 activity increased cell proliferation and downregulated E-cadherin and beta-catenin proteins as well as Lactoferrin, igfbp5 and beta-casein expression. Phospholipid metabolism related genes, Chpt1 and Pcyt2, were also affected by SETD7 inhibition resulting in altered lipidic profile different from the lipogenic phenotype of lactogenic cells. Altogether, the results suggest that inhibition of SETD7 catalytic activity impairs MECs lactogenic differentiation.