To establish proof that systemically administered siRNAs could elicit RNAi-mediated anticancer efficacy in the absence of significant immune activation the authors selected two cell cycle protein kinases known to be cancer targets with well characterized mechanisms for direct tumor cell killing: kinesin spindle protein (KSP) and polo-like kinase 1 (PLK1) [129]. The gene discussed is PLK1; the disease is neoplasm.