Construction of a star-shaped copolymer as a vector for FGF receptor-mediated gene delivery in vitro and in vivo.

The success of cancer gene therapy highly relies on the gene delivery vector with high transfection activity and low toxicity. In the present study, eight-armed polyethylene glycol (EAP) and low molecular weight (LMW) polyethylenimine (PEI) were used as basic units to construct the architecture of a new star-shaped EAP-PEI copolymer (EAPP). MC11, a peptide capable of selectively binding fibroblast growth factor receptor (FGFR) on tumor cell membranes, was further conjugated to EAPP to produce the vector EAPP-MC11 (EAPPM) to enhance tumor targetability. This tumor-targeting vector EAPPM was observed to retard the plasmids mobility at a nitrogen/phosphorus (N/P) ratio of 3. The vector could efficiently condense plasmids within 300 nm nanoparticles with a positive zeta potential at the N/P ratio of 20 or above. While the cytotoxicity of EAPPM polyplexes was similar to that of LMW PEI, it was significantly lower than that of PEI (25 kDa) in HepG2 and PC3 cell lines. In vitro gene transfection with pDNA mediated by EAPPM showed that the transfection efficiency increased 15 times in HepG2 cells but remained at a similar level in PC3 cells in comparison with that of EAPP. By systemic injection of EAPPM/pDNA complexes into a HepG2-bearing mice model, luciferase expression detected in lung, liver, and tumor tissues demonstrated EAPPM could deliver in a targeted manner a reporter gene into tumor tissues, where the luciferase expression of EAPPM was 4 times higher than that of EAPP and even 23 times higher than that of PEI (25 kDa). Furthermore, it was found that the systemic delivery of EAPPM/pCSK-α-interferon complexes in vivo were much more effective in inhibiting tumor growth than EAPP or PEI (25 kDa). These results clearly show that EAPPM is an efficient and safe vector for FGFR-mediated targeted gene delivery both in vitro and in vivo. With low cytotoxicity and high targetability, EAPPM may have great potential as a delivery vector for future cancer gene therapy applications.