The effect of HWF on invasive growth in Matrigel matrix. The cells were seeded in 90% Matrigel and 10% complete medium and left to form colonies. On day 0 the medium on top of the Matrigel matrix was changed to DMEM supplemented with 10% FBS, HS, or HWF. New medium was added every third day. The cells were photographed with a 10× objective.