Overexpression of SUV420H1 and SUV420H2 represses breast cancer cell invasion. (A) SUV420H1 and SUV420H2 mRNA expression levels in a several normal and breast cancer cell lines were examined by real-time PCR. The relative levels of SUV420H1 and SUV420H2 mRNA were normalized against the level of GAPDH mRNA. Average values with standard deviation are shown. (B) To assess the effects of SUV420H1 and SUV420H2 overexpression on the level of H4K20me3, MDA-MB-231 cells were transfected with GFP-tagged SUV420H1 and SUV420H2. pEGFPC1, which carries GFP alone, was used as the empty-vector (negative) control. Cells were fixed, visualized by GFP fluorescence, and simultaneously stained with anti-H4K20me3 mAb. Cells were counterstained with DAPI. Histone H4K20 trimethylation was increased by SUV420H1 and SUV420H2 expression. Arrowheads indicate SUV420H1- or SUV420H2-transfected cells. Bar: 20 μm. (C) MDA-MB-231 cells were transfected with the indicated plasmids. The intensity of GFP and H4K20me3 staining were measured (n = 200) using MetaMorph version 7.1. X axis shows GFP intensity. Y axis shows H4K20me3 intensity. (D) Overexpression of SUV420H1 and SUV420H2 represses breast cancer cell invasion. GFP, GFP-SUV420H1, or GFP-SUV420H2 were transfected into MDA-MB-231 or BT-474 cells, and invasive capacities were measured using matrigel-coated Chemotaxicells. Results are presented as means ± standard deviation (SD). * and ** indicate significant differences (P <0.05 and P <0.01, respectively) relative to the mock transfectant.