It is widely expressed in epithelialand nonepithelial tissues and features prominently in type 2 diabetes.In cancer, its activity has been reported to correlate inversely tothe progression of carcinoma and melanoma; however, the expressionof PAP as a receptor for tumor-associated fibronectin on endothelialcells has been shown to promote tumor cell adhesion and metastasis.39 NIR-PAP (Figure 2) was the first NIR probe for monitoring PAP activity.40 The probe consists of an acryloylated fluorophoreAc–Hcy–OH and a cysteine-proline dipeptide. The gene discussed is FN1; the disease is neoplasm.