Multivalent dipeptidyl peptidase IV fragment-nanogold complex inhibits cancer metastasis by blocking pericellular fibronectin.

Inhibition of cancer metastasis is a fundamental challenge in cancer treatment. We have previously shown that metastasis of cancer cells in the lung is critically promoted by the interaction between the superficial dipeptidyl peptidase IV (DPP IV) expressed on lung endothelial cells and the pericellular polymeric fibronectin (polyFN) of circulating cancer cells. In the present study, we aimed to search for DPP IV fragments with high avidity to polyFN and develop FN-targeted gold nanoparticles (AuNPs) conjugated with DPP IV fragments for treating cancer metastasis. We first identified a DPP IV fragment encompassing amino acids 29-130 of DPP IV, designated DP4A, which contained FN-binding sites and could specifically bind to FN immobilized on gelatin agarose beads. Furthermore, we conjugated maltose binding protein (MBP)-fused DP4A proteins to AuNPs for fabricating a DP4A-AuNP complex and evaluated its FN-targeted activity in vitro and anti-metastatic efficacy in vivo. Our results show that DP4A-AuNP exhibited higher binding avidity to polyFN than DP4A by 9 folds. Furthermore, DP4A-AuNP was more potent than DP4A in inhibiting DPP IV binding to polyFN. In terms of polyFN-targeted effect, DP4A-AuNP interacted with FN-overexpressing cancer cells and was endocytosed into cells 10 to 100 times more efficiently than untargeted MBP-AuNP or PEG-AuNP with no noticeable cytotoxicity. Furthermore, DP4A-AuNP was superior to DP4A in competitive inhibition of cancer cell adhesion to DPP IV. Confocal microscopy analysis revealed that binding of DP4A-AuNP to pericellular FN induced FN clustering without altering its surface expression on cancer cells. Notably, intravenous treatment with DP4A-AuNP significantly reduced metastatic lung tumor nodules and prolonged the survival in the experimental metastatic 4T1 tumor model. Collectively, our findings suggest that the DP4A-AuNP complex with potent FN-targeted effects may have therapeutic potential for prevention and treatment of tumor metastasis to the lung.