To obtain a double-stranded RNA (siRNA) capable of inhibiting expression of a Skp-2 gene, a double-stranded RNA expression cassette capable of expressing the double-stranded RNA, a double-stranded RNA expression vector containing the double-stranded RNA, and to provide a highly safe cancer-specific therapeutic agent or therapeutic method, molecular-targeting Skp-2 and for small cell lung, and the like.

The method comprises setting a plurality of target sequences of the RNAi on a plurality of sites in a protein translation region of a Skp-2 mRNA, structuring expression forms of the siRNA comprising a dsRNA which produces an RNAi effect on a lentivirus vector, preparing a recombinant virus vector, infecting various small cell lung cancer cell strains or small cell lung cancer, and confirming a cell growth inhibiting effect in vitro and a growth inhibiting effect in vivo.