Connexin43 (Cx43) enhances tumor cell diapedesis. HBL100 and HBL100v cells or cells expressing functional Cx43 (HBL100Cx43) were co-cultured with HMVEC monolayers for 1, 5 and 7 h. (a) Adherent cells in the process of diapedesis and cells that had completed transmigration were scored together as migrating. Compared to HBL100v or HBL100 wild-type cells a two-fold increase in diapedesis of HBL100Cx43 cells was seen at 1, 5 and 7 h. (b) At 7 h the relative proportion of cells at different stages of migration was evaluated. Compared to control cells, the observed two-fold increase in the number of transmigrating HBL100Cx43 cells correlated with a two-fold decrease in the number of HBL100Cx43 cells located on top of the monolayer. No significant difference in the proportion of cells underneath the endothelium was observed between the Cx43 expressing and non-expressing HBL100 cells. Data are expressed as the mean percentage ± SEM of three independent experiments performed in triplicate (*p < 0.05).