Fig. 4.

In vitro characterization reveals role for Axl in mediating glioma cell migration and invasion. (A) Analysis of morphology and in vitro behavior of cell clones under nonconfluent conditions. (B) Migration assay with multicellular aggregates of transfected cell clones. Migratory activity of tumor cells is illustrated for AXL-WT and AXL-DN cells at 72 h after plating (Left) and is analyzed quantitatively over 7 days (Right). Area of migration was analyzed planimetrically by means of an image analysis system. Experiments were performed in triplicate. The mean ± SD values are represented. ∗, P < 0.05 vs. mock-transfected cells. (C) Analysis of tumor cell invasion by 48-h confrontation of AXL-WT tumor cell spheroids (Upper) or AXL-DN tumor cell spheroids (Lower) with fetal rat brain cell aggregates. Note clear border between AXL-DN tumor cell spheroid and brain cell aggregate, whereas the AXL-WT spheroid has merged with the brain aggregate, indicating lack of invasiveness after inhibition of Axl signaling. B, brain cell aggregate; S, tumor spheroid. Experiments were performed in quadruplicate.