Nucleic acid modulation of gene expression: Approaches for nucleic acid therapeutics against cancer

Most cancers are characterized by abnormal gene expression, which is thought to contribute to the pathogenesis and maintenance of the malignant phenotype; abnormal proliferation, maturation, and apoptosis. Silencing such genes would appear to be a rational approach to the therapy of cancer, and some preliminary clinical studies support this concept. Of the strategies available, the anti-mRNA gene silencing approach has attracted much attention and is the focus of this review. This strategy includes three types of agents: (1) single-stranded antisense ohgonudeotides; (2) catalytically active oligonucleotides, such as ribozymes, and DNAzymes that possess inherent RNA cleaving activity, and (3) small interfering RNA (siRNA) molecules that induce RNA interference (RNAi). Among these agents, antisense ohgonudeotides, especially phosphorothioate (PS) oligonucleotides, have been the most frequently used in clinical trials. In this article, we provide an overview of anti-mRNA gene silencing agents and their development for use as cancer therapeutics.