Cationic lipid-mediated gene transfer: current concepts

Infectious disease, heart disease, cancer, autoimmunity, genetic defects and even traumatic injury may someday be treated with gene therapy and gene transfer strategies. The potential impact of this new technology on human disease has produced optimism and expectation for scientists and lay people alike. As more effort is directed at harvesting the potential of this technology it has become clear that the success or failure of gene therapy will hinge on our ability to manipulate and control the process of gene transfer in somatic cells. Today, somatic gene transfer is accomplished using either viral or non-viral gene transfer methods. The benefits and limitations of each system are aggressively being investigated to determine which characteristics are most compatible with safe and reliable gene transfer. Gene transfer with cationic lipid/plasmid DNA complexes (cationic lipoplexes) has become a popular means of delivering therapeutic genes and is being tested in preclinical and clinical trials. Cationic lipoplexes are easy and inexpensive to produce, they are composed of non-toxic and non-immunogenic precursor, and they have the potential of delivering large polynucleotides into somatic cells. Additionally, these reagents are easily manipulated in the laboratory to incorporate novel biological functions or to produce new formulations that can be screened for in vivo gene transfer activity. The last few years has seen many advances in our understanding of molecular and biological factors that influence cationic lipid-mediated gene transfer. In this review we discuss recent developments in the field of cationic lipid-mediated gene transfer with emphasis on in vivo application where possible. We will consider new discoveries concerning the molecular and cellular events that control the uptake, transit and expression of lipoplexes in somatic cells. Recent biodistribution and pharmacokinetic studies and current concepts regarding the toxicity and immunogenicity of cationic lipoplexes will also be discussed. We also survey some of the many preclinical and clinical trials using cationic lipid-mediated gene transfer, with emphasis on cancer applications.