(Tyr(0),Bpa(4))bombesin is a GRP receptor agonist

Bombesin peptide conjugated gold nanocages internalize via clathrin mediated endocytosis

The nature of interaction and mechanism of internalization of receptor-avid peptide nanoparticles with cells is not yet completely understood. This article describes the cellular internalization mechanism and intracellular trafficking of peptide conjugated receptor targeted porous Gold nanocages (AuNCs) in cancer cells. We synthesized and characterized a library of AuNCs conjugated with bombesin (BBN) peptide. Evidence of selective affinity of AuNC-BBN toward gastrin releasing peptide receptors (GRPR) was obtained using radiolabeled competitive cell binding assay. Endocytic mechanism was investigated using cell inhibitor studies and monitored using optical and transmission electron microscopy (TEM). Results show AuNC-BBN uptake in PC3 cells is mediated by clathrin mediated endocytosis (CME). Indeed, in the presence of CME inhibitors, AuNC-BBN uptake in cells is reduced up to 84%. TEM images further confirm CME characteristic clathrin coated pits and lysosomal release of AuNCs. These results demonstrate that peptide ligands conjugated to the surface of nanoparticles maintain their target specificity. This bolsters the case for peptide robustness and its persisting functionality in intracellular vehicular delivery systems.

Gastrin-releasing peptide receptor as a molecular target in experimental anticancer therapy

Over the last two decades, several lines of experimental evidence have suggested that the gastrin-releasing peptide (GRP) may act as a growth factor in many types of cancer. For that reason, gastrin-releasing peptide receptor (GRPR) antagonists have been developed as anticancer candidate compounds, exhibiting impressive antitumoral activity both in vitro and in vivo in various murine and human tumors. In this article, the GRPR cell surface expression profile in human malignancies is reviewed aiming at the identification of potential tumor types for future clinical trials with GRP analogues and antagonists. In this review, we summarize the current literature regarding the GRPR status in human malignancies. Source data were obtained by searching all published material available through Medline, PubMed and relevant articles from 1971 to 2006. The data available demonstrated a high expression of GRPRs in a large spectrum of human cancers, demonstrating the potential relevance of this intracellular signaling pathway in various human tumor models. The GRPR may be an interesting target for therapeutic intervention in human malignancies, as carriers for cytotoxins, immunotoxins or radioactive compounds, being also a potential tool for tumor detection.