CD99 and neoplasm: Specifically, Ackermann et al. reported that CD99-expressing tumor cells contribute to endothelial cell formation in a xenograft model of EwS [41], which implies that GD2-specific CAR T cells are highly likely to interact with tumor cells (and release tTF-NGR) also on the luminal side of neovessels, the main location of the pro-coagulatory activity of tTF-NGR.