The present invention provides a pharmaceutical composition for treating cancer, comprising at least one selected from deoxyribonucleic acids (DNA) for encoding small interfering RNA (siRNA) which complementarily binds to the base sequence of the transcript (mRNA transcript) of the FLJ25416 gene, represented by sequence number 3, sequence number 5, and sequence number 7 to inhibit the intracellular expression of the FLJ25416 gene, antisense RNA which inhibits expression of the FLJ25416 gene, and short hairpin RNA (shRNA) which inhibits expression of the FLJ25416 gene. As the siRNA, which is complementary to the base sequence of the transcript (mRNA transcript) of the FLJ25416 gene, the antisense RNA, and the shRNA, according to the present invention, inhibit expression of the FLJ25416 gene which is known to be expressed in cancer cells, and thus kill cancer cells, the composition of the present invention can be used as a novel anti-cancer agent.