Bauhinia purprea agglutinin‐modified liposomes for human prostate cancer treatment

Bauhinia purprea agglutinin (BPA) is a well‐known lectin that recognizes galactosyl glycoproteins and glycolipids. In the present study, we firstly found that BPA bound to human prostate cancer specimens but not to normal prostate ones. Therefore, we sought to develop BPA‐PEG‐modified liposomes (BPA‐PEG‐LP) encapsulating anticancer drugs for the treatment of prostate cancer. We examined the tumor targetability of BPA‐PEG‐LP with human prostate cancer DU145 cells, and observed that fluorescently labeled BPA‐PEG‐LP dominantly associated with the cells via the interaction between liposome‐surface BPA and cell‐surface galactosyl molecules. We also observed that BPA‐PEG‐LP accumulated in the prostate cancer tissue after the i.v. injection to DU145 solid cancer‐bearing mice, and strongly bound to the cancer cells. In a therapeutic study, DU145 solid cancer‐bearing mice were i.v. injected thrice with BPA‐PEG‐LP encapsulating doxorubicin (BPA‐PEG‐LPDOX, 2 mg/kg/day as the DOX dosage) or PEG‐modified liposomes encapsulating DOX (PEG‐LPDOX). As a result, BPA‐PEG‐LPDOX significantly suppressed the growth of the DU145 cancer cells, whereas PEG‐LPDOX at the same dosage as DOX showed little anti‐cancer effect. The present study suggested that BPA‐PEG‐LP could be a useful drug carrier for the treatment of human prostate cancers. BPA bound to human prostate cancer cells via the cell‐surface sugar chains terminating in galactose, resulting that BPA recognized to cancerous, but not to normal, human prostate tissue.