MT1-MMP is required for lipid-induced invasion of HT1080 cells in 3D collagen gels. (A) HT1080 cells were transfected with control siRNAs (Luciferase, Lamin A/C, or a scrambled MT1-MMP), siRNAs targeting soluble MMP-2 or MMP-9, or siRNAs targeting MT1-MMP (MT1-C, MT1-SP). Cells were allowed to invade 3D collagen gels in response to LPA or S1P for 48 hours prior to fixation and quantification of invasion as in Fig. 2. Data are expressed as mean numbers of invading cells per HPF (20×) (± S.D.) from a minimum of 20 fields per condition. Statistical significance of means was determined using t-test where * = p < 0.01 relative to Luciferase control. si = siRNA; Luc = Luciferase, LMNA = Lamin A/C, MT1-C = custom MT1-MMP, MT1-SP = SMART pool® MT1-MMP, MT1-sc = scrambled MT1-MMP. (B) siRNA transfected HT1080 cells from panel A were imaged as in Fig. 2 to demonstrate tumor cell invasion. Magnification = 20×. Scale bars = 50 μm. Arrowheads indicate the position of the monolayer at initiation of invasion.