Interestingly, we have found that Bmi-1 is negatively regulated by Mel-18 and expression of Mel-18 negatively correlates with Bmi-1 in breast tumors, and Mel-18 overexpression in breast cancer cell line MCF7 results in downregulation of Bmi-1 and reduction of transformed phenotype [38]. This evidence concerns the gene PCGF2 and breast neoplasm.