Since Fra-1 and c-Fos physically associate with CDS1 through their N-terminus domain and activate it through their BD domain, and both are overexpressed in breast tumor tissues in comparison with their undetectable levels in normal tissue (20), we hypothesized that the NA domains of both proteins, could function as negative dominants of the cytoplasmic activity of c-Fos and Fra-1 by associating with the enzymes that the full-length proteins activate, but without activating them. Here, FOS is linked to breast neoplasm.