DSPE-PEG (2000)-Mannose is a mannose-containing lipid. DSPE-PEG (2000)-Mannose is used to prepare mannose-conjugated Liposome (Man-lipo) for siRNA delivery. Mannose-modified liposomes encapsulating IDO siRNA (Man-lipo-siIDO) preferentially knock down IDO expression in the draining lymph nodes and spleens of melanoma-bearing mice. Man-lipo-siIDO delays the onset time of melanoma and reduces tumor volume[1].