HEK293 cells transfected with MT1-MMP cDNA invade 3D collagen gels in response to LPA. (A) Tumor cell lysates were prepared for Western blot analysis. Lysates were probed for MT1-MMP to assess protein expression in the four tumor cell lines. Lysates were probed for Actin as a loading control. (B) HEK293 cells were transfected with the pAdTrack-CMV plasmid as a control, or plasmids encoding MT1-MMP, MT2-MMP, or MT3-MMP cDNA 24 hours prior to placement in invasion assays. Cells were allowed to invade 2.0 mg/ml collagen gels in the presence or absence of 1 μM LPA. Data are expressed as mean numbers of invading cells per HPF (20×) (± S.D.) from a minimum of 20 fields. (C) Lysates from HEK293 cells transfected with cDNAs encoding the designated genes were prepared for Western blot analysis and probed for GFP, MT1-MMP, MT2-MMP, MT3-MMP, or Actin as a loading control. TRK = pAdTrack-CMV, MT1 = MT1-MMP, MT2 = MT2-MMP, MT3 = MT3-MMP.