DNMT3A and breast cancer: To directly measure the effect of inducing DNA methylation on proliferation of ER-positive breast cancer cells, we used a panel of 7 breast cancer cell lines (4 ER-positive and 3 ER-negative) expressing SAM-DNMT3A or SAM-DNMT3A-inactive with no sgRNA or two AAVS1 targeting sgRNAs that induce global DNA methylation (Fig. 5B, C).