In vivo therapeutic activity of systemic tTF-NGR against CD13+ A549 tumor xenografts.

To investigate CD13 expression flow cytometry was performed with a monoclonal PE-labeled anti-CD13 antibody. CD13 expression was found in 47% of the A549 lung cancer cells (green, control; purple, CD13) (Fig. 3A). Following treatment with tTF-NGR (1 mg tTF-NGR/kg x4 (arrows); i.v.; n = 4 CD-1 nude mice) tumor growth of subcutaneous A549 xenotransplants was reduced as compared to the saline control group (n = 6) CD-1 nude mice (Fig. 3B). The CD13 expression in subcutaneous A549 xenotransplant is demonstrated by immunofluorescence; since the antibodies used for CD13 and CD31 staining are species-specific for human CD13 and CD31, vascular and perivascular staining were not assayed in the xenografts (Fig. 3C).