Background: Cell and tissue-specific DNA delivery can be achieved by derivatizing vehicles with a targeting ligand for certain receptor. CXCR4 is a receptor of chemokine stromal cell-derived factor (SDF)-1 and viral protein viral macrophage inflammatory protein (vMIP)-II. It is expressed on some types of stem and cancer cells. The present study aimed to design and characterize the group of CXCR4 targeted peptides for receptor-mediated gene delivery. We focused on bifunctional peptide carriers: two derived from N-terminal sequences of SDF-1 and one from vMIP-II.
Methods: Three synthetic chemokine-derived peptides, designated long CDP (KPVSLSYRSPSRFFESH-K9-biotin), short CDP (KPVSLSYR-K9-biotin) and viral CDP (D-LGASWHRPDK-K9-biotin), were evaluated for gene delivery to CXCR4 positive and negative cells. Oligolysine K9-biotin was used as a control. The Lys 8 moiety binds DNA electrostatically, whereas C-terminal lysine was modified with biotin to study intracellular uptake of the peptides. Complex formation with DNA was monitored by ethidium bromide fluorescence quenching.
Results: All peptides condensed plasmid DNA. Gene delivery by CDP/DNA complexes is glycerol-dependent and the level of luciferase expression with signal modified carriers was comparable with the efficacy of polyethylenimine (PEI) in CXCR4 expressing cell lines (A172, HeLa) and was ten- to 50-fold higher compared to unmodified peptide. By contrast, CDP transfection efficacy on CXCR4-negative cells (chinese hamster ovary) was much lower than in PEI. Intracellular uptake analysis of biotin-labeled peptides indicated that CDPs entered cells more efficiently than oligolysine.
Conclusions: The small, bifunctional peptides reported in the present study may be useful in gene delivery to (and gene therapy of) the different tumors and other cells expressing CXCR4.