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

Purpose: The aim of this study was to evaluate inflammation and tumour imaging with a vascular adhesion protein 1 (VAP-1) targeting peptide super(68)Ga-DOTAVAP-P1 in comparison with super(18)F-FDG. Methods: 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. Results: super(68)Ga-DOTAVAP-P1 delineated acute, sterile inflammation comparable with super(18)F-FDG. However, the tumour uptake of super(68)Ga-DOTAVAP-P1 was low in contrast to prominent super(18)F-FDG uptake. The standardised uptake values of inflammation and tumours by PET were 1.1 plus or minus 0.4 (mean plus or minus SEM) and 0.4 plus or minus 0.1 for super(68)Ga-DOTAVAP-P1 and 2.0 plus or minus 0.5 and 1.6 plus or minus 0.8 for super(18)F-FDG, respectively. In addition, PET studies showed inflammation to muscle and tumour to muscle ratios of 5.1 plus or minus 3.1 and 1.7 plus or minus 0.3 for super(68)Ga-DOTAVAP-P1 and 6.2 plus or minus 0.7 and 4.6 plus or minus 2.2 for super(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 Conclusion: The super(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.