Patent ID: 8592572

Claim:
An antitumor agent, which comprises: short hairpin RNA (shRNA) capable of inhibiting expression of thymidylate synthase by RNAi action; and a PEG-modified cationic liposome, wherein the shRNA is bound to the surface of the PEG-modified cationic liposome and has an overhang comprising at least two nucleotides at the 3′ end and the PEG-modified cationic liposome comprises a catonic liposome composed of dioleoylphosphatidylethanolamine (DOPE), palmitoyloleoylglycerophosphocholine (POPC), cholesterol (CHOL), and O,O′-ditetradecanoyl-N-(α-trimethylammonioacetyl)diethanolaminechloride (DC-6-14) at a molar ratio of 3:2:3:2.