MMP9 and neoplasm: CEACAM1-L expression mediates tumor development within tumor cells directly (colon [12], melanoma [13], non-small-cell lung cancer [14], thyroid [15], gastric [16]) as well as indirectly via cells in the stromal compartment (endothelial cells [7, 17], CD11b+Gr1+ immature myeloid cells [18, 19], matrix metalloproteinase 9-positive leukocytes [20], tumor-associated macrophages [21] and activated T cells [8]).