EGF induces MMP-independent amoeboid migration in Hm cells. A: Hm cells were embedded in a three-dimensional collagen matrix and overlaid with starving medium containing EGF. The pictures are a detail magnification of Additional file 3, Movie S1 and show the migrative behaviour of a single cell that was photographed eight times consecutively with a time interval of 4 min between the pictures. The arrow indicates areas of dense matrix where the cell has to contract its cell body. B: Analysis of the speed of Hm cells migrating in a three-dimensional collagen gel. Cells were embedded into collagen in the presence of DMSO, AG1478, U0126 and a mixture of MMPI 9/13 and GM6001 (Ilomastat). Where indicated, cells were overlaid with EGF-containing medium. Graphs display the speed of single cells that was calculated from the time-lapse movies, and the mean speed for each condition is indicated. The following numbers of cells were examined: ctrl., EGF, EGF + U0126: n = 161 (for each); EGF + AG1478: n = 78; EGF + MMP inhibitors: n = 120. ***: p < 0.0001. C: Hm cells were embedded in collagen matrix and stimulated with EGF as described above. The supernatant contained DMSO, AG1478 or U0126, respectively. After 8 h, where maximal stimulation was seen before, whole collagen gels were used for RNA isolation and RT-PCR analysis of the indicated genes. In case of Mmp1a and -1b a lower, unspecific DNA band was seen, which was presumably due to oligonucleotide multimers that can form in the absence of specific template. The specific bands for MMP1a and -1b are indicated by an arrow.