HMGA1 and breast carcinoma: Indeed, HMGA1 over-expression in nonaggressive, nontumorigenic human breast epithelial cells leads to the acquisition of a transformed and aggressive phenotype (10), whereas HMGA1 silencing in highly aggressive, metastatic human breast cancer cell lines leads to reversion of the tumorigenic phenotype, as assessed both by in vitro and in vivo approaches (9, 12, 14, 15).