Fig. 1.

Specific accumulation of lymphatic homing peptides in tumors. Mice bearing orthotopic MDA-MB-435 xenograft tumors were i.v. injected with fluorescein-conjugated LyP-1 (A)ora fluorescein-conjugated control peptide (ARALPSQRSR) (B). The mice were anesthetized 16–20 h later and examined for fluorescence under blue light. Tumor fluorescence of a LyP-1-injected tumor mouse is shown in A. No fluorescence was detected in tumors of mice injected with the control peptide (B). After the external examination, the mice were killed, and tumor, kidneys, spleen, and liver were excised and examined for fluorescence. LyP-1 produced intense fluorescence in the tumor, whereas no fluorescence was detectable in other organs (C). Even when imaged directly, no fluorescence was observed in the control peptide-injected tumor (D). The gallbladder is autofluorescent and appears as a green spot in C and D. E shows quantification of the imaging results for LyP-1 and for LyP-1b, which was analyzed in similar experiments. Mice that did not receive any fluorescent compound were used to determine the level of autofluorescence in tissues, and this background was subtracted from the experimental values. The graph shows a representative experiment of three. (F–H) Mice injected with peptides as in A and B were perfused through the heart, and their tumors were examined microscopically. Strong LyP-1 fluorescence is seen in the nuclei (visualized by 4′,6-diamidino-2-phenylindole staining) of tumor cells (F). No appreciable fluorescence from the control peptide is seen in tumor tissue (G), and all normal tissues tested were negative for all peptides (the result for LyP-1 in the brain is shown in H). T, tumor; B, brain; H, heart; Lu, lungs; Li, liver; S, spleen; K, kidneys. Magnification: F and G, ×100; H, ×200.