The present invention provides compositions comprising interfering RNA (e.g., siRNA, aiRNA, miRNA) that target polo-like kinase 1 (PLK-1) expression and methods of using such compositions to silence PLK-1 expression. More particularly, the present invention provides unmodified and chemically modified interfering RNA molecules which silence PLK-1 expression and methods of use thereof. The present invention also provides serum-stable nucleic acid-lipid particles (e.g., SNALP) comprising an interfering RNA molecule described herein, a cationic lipid, and a non-cationic lipid, which can further comprise a conjugated lipid that inhibits aggregation of particles. The present invention further provides methods of silencing PLK-1 gene expression by administering an interfering RNA molecule described herein to a mammalian subject. The present invention additionally provides methods of identifying and/or modifying PLK-1 interfering RNA having immunostimulatory properties. Methods for sensitizing a cell such as a cancer cell to the effects of a chemotherapy drug comprising sequentially delivering PLK-1 interfering RNA followed by the chemotherapy drug are also provided.
