Therapeutic microRNA

Therapeutic potentials of microRNA have often been discussed and several functional studies explore strategies using antisense RNA against tumorigenic microRNA or replacing it. One recent publication in the magatine Cell shows the power of gene therapy utilizing inhibitory microRNA (http://www.cell.com/abstract/S0092-8674(09)00446-2). A characteristic feature of common tumor models is upregulation of specific and downregulation of general miRNA levels. Using a murine model for inducible liver tumors and human Hepatocellular carcinoma (HCC) cells the team around Joshua Mendell took advantage of the fact, that abundance of microRNA miR-26a is almost twice as high in unaffected tissue than in tumorous liver tissue. Through retroviral vectors it is possible to force expression of miR-26a and thus increasing its endogenic concentration leading to cell cycle arrest of tumor cells. Cellular proliferation is inhibited because miR-26a directly represses the expression of cell cycle control proteins Cyclin D2 and Cyclin E2 which also induces tumor-specific apoptosis. All this sounds pretty impressive to me but as the authors stated it is still the beginning. More than likely several powerful tumor repressing microRNAs will be discovered in close future and once clinical studies investigate toxic consequences of therapeutic microRNA treatment we will be close to making a great leap in curing cancer.