ANPEP and breast adenocarcinoma: In vitro fluorescence microscopy studies of an Oregon Green (OG) labeled c[KNGRE]-NH2 (OG attached to the side chain of Lys) revealed selective binding to CD13-receptor positive (CD13+) HT-1080 human fibrosarcoma cells and minimal binding to receptor negative (CD13−) MCF-7 human breast adenocarcinoma cells [15].