Expression of CD13/APN is induced during capillary tube formation in vitro and tumor progression in vivo.

(A) RT-PCR analysis of 10 μg total RNA from EOMA cells cultured for 24 hours with (+, lane 1) or without (−, lane 2) reconstituted basement membrane matrix (Matrigel) or NIH3T3 fibroblast positive control cells (lane 3) using primers specific for CD13/APN, β3-integrin and β-actin. (B) A representative experiment showing EOMA cells stably transfected with the indicated plasmid constructs cultured with (+ bm) or without (−bm) basement membrane matrix (Matrigel) to stimulate endothelial morphogenesis. Confocal images were acquired 18 to 24 hours after incubation. CMV-GFP (positive control line with GFP driven by the constitutive CMV promoter); null-GFP (promoterless negative control cell line); CD13-GFP (images of 2 independent cell lines containing the CD13/APN proximal promoter driving GFP expression). (C) Flow cytometric analysis of GFP-expressing cells in single-cell suspensions of EOMA xenografts. Data are expressed as percentage GFP-positive cells and numbers are representative of 2 independent experiments.