PET imaging of inflammation and adenocarcinoma xenografts using vascular adhesion protein 1 targeting peptide 68Ga-DOTAVAP-P1: comparison with 18F-FDG.

Abstract

The aim of this study was to evaluate inflammation and tumour imaging with a vascular adhesion protein 1 (VAP-1) targeting peptide (68)Ga-DOTAVAP-P1 in comparison with (18)F-FDG. Rats with both subcutaneous human pancreatic adenocarcinoma xenografts and turpentine oil-induced acute sterile inflammation were evaluated by dynamic positron emission tomography (PET) and by digital autoradiography of tissue cryosections. Subsequently, the autoradiographs were combined with histological and immunohistological analysis of the sections. (68)Ga-DOTAVAP-P1 delineated acute, sterile inflammation comparable with (18)F-FDG. However, the tumour uptake of (68)Ga-DOTAVAP-P1 was low in contrast to prominent (18)F-FDG uptake. The standardised uptake values of inflammation and tumours by PET were 1.1 +/- 0.4 (mean +/- SEM) and 0.4 +/- 0.1 for (68)Ga-DOTAVAP-P1 and 2.0 +/- 0.5 and 1.6 +/- 0.8 for (18)F-FDG, respectively. In addition, PET studies showed inflammation to muscle and tumour to muscle ratios of 5.1 +/- 3.1 and 1.7 +/- 0.3 for (68)Ga-DOTAVAP-P1 and 6.2 +/- 0.7 and 4.6 +/- 2.2 for (18)F-FDG, respectively. Immunohistochemistry revealed increased expression of luminal VAP-1 on the endothelium at the site of inflammation and low expression in the tumour The (68)Ga-DOTAVAP-P1 PET was able to visualise inflammation better than tumour, which was in accordance with the luminal expression of VAP-1 on vasculature in these experimental models.