Copyright information:Taken from "Fibroblast-derived MT1-MMP promotes tumor progression in vitro and in vivo"BMC Cancer 2006;6():52-52.Published online 6 Mar 2006PMCID:PMC1450297.Copyright © 2006 Zhang et al; licensee BioMed Central Ltd. Wild-type (WT) murine fibroblasts derived from the dermis of late-gestation embryos were cultured atop collagen and invasion assessed over a 6 day period in the presence or absence of TIMP-2 (10 nM) added to the culture daily (A). MMP-2 -/- and MMP-9 -/-, but not MT1-MMP -/- cells penetrate type I collagen over the 6 day culture period normalized for total cell number (B); the results are quantified by number of cells invading and depth of penetration (C). Experiments were conducted in DMEM with 10% WT, MMP-2 null or MMP-9 null serum. (Magnification as marked, bar = 100 μm)