Development of a gene/drug dual delivery system for brain tumor therapy: potent inhibition via RNA interference and synergistic effects.

Malignant brain tumors are characterized by three major physiological processes: proliferation, angiogenesis, and invasion. Traditional cytotoxic chemotherapies (e.g. Paclitaxel) control the tumor by blocking growth and proliferation mechanisms, but leave angiogenesis and invasion unchecked. We identified Matrix metalloproteinase-2 (MMP-2), an essential proteinase regulating brain tumor invasion and angiogenesis, as one of the therapeutic target. A designer RNAi plasmid was developed, and complexed with the gene carrier polyethylenimine (PEI), in an effort to specifically suppress MMP-2 expression in tumor cells. The gene and a cytotoxic drug Paclitaxel were then dual-encapsulated in PLGA based submicron implants to achieve a sustained release of both agents. Potent inhibition effects on MMP-2 mRNA and protein expression, in vitro cell angiogenesis and invasion were demonstrated both on the PEI/DNA nanoparticles alone, and on the PEI/DNA nanoparticles embedded in microfibers. Most importantly, through in vivo test on intracranial xenograft tumor model in BALB/c nude mice, it was proved that the gene/drug dual delivery microfibers are able to impose significant tumor regression compared with single drug delivery microfibers and commercial drug treatment, showing evidence for synergistic therapeutic efficacy.