In this week's PNAS Early Edition, investigators at the University of Edinburgh in the UK show that "transcriptionally repressed genes become aberrantly methylated and distinguish tumors of different lineages in breast cancer." More specifically, in its investigation of promoter methylation in 19 breast cancer cell lines and 47 primary breast tumors, the team found "120 genes that were significantly repressed in association with methylation," which "allowed the unsupervised segregation of cell lines into epithelial and mesenchymal lineages." The Edinburgh team says that aberrant