Altogether, these results demonstrate that the expression of CD13 is necessary but not sufficient for the binding of CNGRC-containing peptides and confirm that the in vitro expression of the CNGRC-binder isoform of the CD13 is restricted to the cells that form the tumor vasculature (i.e., endothelial cells and pericytes) and to some tumor cell lines. Here, ANPEP is linked to neoplasm.