The participation of nuclear and cytoplasmic c-Fos in driving tumor cell proliferation and growth was examined in growing MDA-MB231 cells cultured in the presence or the absence of an AP-1 Nuclear Localization Sequence Peptide (NLSP) that blocks the nuclear import of c-Fos and Fra-1 as AP-1 dimers [42]. This evidence concerns the gene FOSB and neoplasm.