JUN and neoplasm: Previous studies have also shown that TGF-β1 promotes the expression of matrix metalloproteinase-2 (MMP-2) via the binding of transcription factors c-Jun and c-Fos to the AP1 (Jun/Fos) site in the MMP-2 gene promoter, thereby stimulating the release of MMP-2 from the tumor and surrounding stromal cells (11).