Endogenous

CD13/APN is induced in response to serum concentration and angiogenic factors. Expression of CD13/APN protein (A) or mRNA (B) in KS1767 cells is dependent on serum concentration. Serum-starved cells were stimulated with the indicated concentrations of FBS or left untreated (no fetal calf serum [FCS]) for 24 hours. CD13/APN protein expression was measured by flow cytometry; relative transcript levels in total RNA were assayed by Northern blot analysis. (C) bFGF and VEGF induce time-dependent increases inCD13/APN mRNA expression in KS1767 cells similar to that seen with the angiogenic marker, β3 integrin. Total RNA was isolated at the indicated time intervals after addition of bFGF (50 ng/mL) or VEGF (25 ng/mL) to serum-starved cells and hybridized with the indicated probes.