PLXNB3 and neoplasm: To investigate the low tumor burden with the loss of Plexin-B3 at the molecular level, we performed an IHC of proliferation marker Ki-67 and observed a lower number of Ki-67-positive cells in tumors of mice injected with T3M-4- and CD18/HPAF-shPlexin-B3 in comparison with mice injected with T3M-4- and CD18/HPAF-Control cells (Figure 4D).