Development of Secreted Protein and Acidic and Rich in Cysteine (SPARC) Targeted Nanoparticles for the Prognostic Molecular Imaging of Metastatic Prostate Cancer.

Prostate cancer is the most commonly diagnosed non-skin malignancy in the United States and presents with a wide range of aggressiveness from extremely slow-growing to highly aggressive. There is a clinical need to determine the metastatic potential of the primary tumor to design the most appropriate treatment plan ranging from watchful waiting to more aggressive, invasive surgical treatments. In this study we have developed a nanoparticle based imaging agent that targets SPARC (Secreted Protein Acidic Rich in Cysteine), a molecular marker of prostate cancer metastatic potential. Previous studies by this group used phage display to identify a peptide with high binding affinity and specificity for SPARC. In this study, the SPARC-targeted peptide sequence was used to design a biomaterial with improved pharmacokinetic properties by attaching it to a biocompatible nanoparticle that is also coupled to a fluorophore for in vivo imaging. Prostate cancer cell lines with varying degrees of SPARC expression were used to show the ability of the targeted nanoparticle to bind specifically to SPARC in vitro and in vivo including the clinically relevant bone and lung metastases. We show that in vivo imaging information correlates with the metastatic potential of the prostate tumor. This prognostic information could enable doctors to stratify patients and design personalized treatment strategies.