Interestingly, we found previously that PLAC1 is a critical factor for breast cancer progression, as RNAi-mediated silencing of PLAC1 in MCF-7 and BT-549 breast cancer cells results in decreased cyclin D1 levels and induces a G1-S cell cycle block with nearly complete abrogation of proliferation[1]. This evidence concerns the gene CCND1 and breast carcinoma.