Adhesive Interactions Figure 2. The alterations of motile behavior of transformed IAR-6-1 and IAR1170 cells in comparison with those of nontransformed IAR-2 cells. (A–C) Selected frames from the time-lapse sequences of sparse cultures showing cell behavior and cell-cell interactions. (A) Nontransformed IAR-2 cells form an island. Cell-cell contacts are stable during the entire period of observation (see also Video S1). (B) Transformed IAR-6-1 cells; (C) transformed IAR1170 cells (clone H5). In cultures of transformed IAR-6-1 and IAR1170 cells, significant alterations in cell-cell interactions are seen. Cells extend lamellipodia at different sites of the free edges and establish contacts with different neighboring cells (arrows). These contacts are unstable and often break (arrowheads). Cells could move in different directions (asterisks) (see also Video S2 and Video S3). Bar, 20 mm. doi:10.1371/journal.pone.0008027.g002 Neoplastic transformation modified the dynamics of cell-cell interactions in a narrow wound. After the establishment of the contact between two cells, transformed IAR-6-1 cells continued to form lamellipodia both at the site of the contact and at the free edges (Figure 4C and Video S5). The rates of lamellipodial protrusion and retraction did not change (Figure 4D and Figure S3). We did not see contact paralysis of protrusive activity at the site of the contact of IAR-6-1 cells (Figure 4D), and further analysis revealed significant overlapping in this zone (Figure 4E). While the mean overlapping area of contacting IAR-2 cells was 18.062.93 mm2 (mean6SEM, n = 12), the mean overlapping area of contacting IAR-6-1 cells was 76.5617.37 mm2 (n = 14) at 15 min after cell-cell contact establishment. The studies performed demonstrated the differences in cell behavior during the establishment of cell-cell contact by nontransformed and transformed cells. Cell-cell interactions of PLoS ONE | www.plosone.org 4 November 2009 | Volume 4 | Issue 11 | e8027