title: Saporin toxin-conjugated monoclonal antibody targeting prostate-specific membrane antigen has potent anticancer activity.
abstract: BACKGROUND
  Prostate-specific membrane antigen (PSMA) provides an attractive target for monoclonal antibody targeted therapies in the treatment of prostate cancer (PC). In this study, we generated an immunotoxin by linking a humanized anti-PSMA monoclonal antibody (hJ591) to the ribosome-inactivating protein toxin saporin. The hJ591-saporin immunoconjugate was evaluated for antitumor activity against PC cells.
  
  
  METHODS
  PSMA-positive cell lines, LNCaP and CWR22Rv1 and a PSMA-negative cell line, PC-3, were used in these experiments. The hJ591 was biotinylated and mixed with streptavidin-saporin (SAZAP). The binding ability of hJ591-SAZAP and the extent of internalization into the cells were tested. The viability of cells treated with hJ591-SAZAP was also examined and the apoptotic cells were measured. Lastly, the anticancer effect of hJ591-SAZAP was investigated in vivo.
  
  
  RESULTS
  The binding ability of hJ591-SAZAP to PSMA was equivalent to that of unconjugated J591. Internalization of hJ591-SAZAP was clearly detected in PSMA-positive, but not in PSMA-negative cell lines. IC(50) of hJ591-SAZAP was 0.14 nM, 1.99 nM, and more than 100 nM in LNCaP, CWR22Rv1, and PC-3 cells, respectively. After 72 hr of hJ591-SAZAP treatment, the percentage of apoptotic cells was 60.29% and 40.73% in LNCaP and CWR22Rv1 cells, respectively, compared to 4.70% in PC-3 cells. The hJ591-SAZAP also had anticancer activity in a LNCaP xenograft model.
  
  
  CONCLUSIONS
  Our findings show that hJ591-SAZAP conjugate has potent and selective antitumor effects on PSMA-positive PC cells in vitro and in vivo. This study supports development of PSMA antibody-toxin conjugates for therapy of PC.
authors.affiliation: Department of Urology, National Defense Medical College, Tokorozawa, Saitama, Japan. kksmy@sa2.so-net.ne.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Kuroda
authors.forename: He
authors.initials: H
authors.lastname: Liu
authors.forename: Sae
authors.initials: S
authors.lastname: Kim
authors.forename: Ming
authors.initials: M
authors.lastname: Guo
authors.forename: Vincent
authors.initials: V
authors.lastname: Navarro
authors.forename: Neil H
authors.initials: NH
authors.lastname: Bander
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D019921:Biotinylation; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009919:Orchiectomy; D017430:Prostate-Specific Antigen / Q000276:immunology*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000453:epidemiology / Q000276:immunology* / Q000401:mortality / Q000601:surgery; D054789:Ribosome Inactivating Proteins, Type 1 / Q000276:immunology*; D000076985:Saporins; D014183:Transplantation, Heterologous; D014481:United States / Q000453:epidemiology
chemical_list: D000911:Antibodies, Monoclonal; D000972:Antineoplastic Agents, Phytogenic; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D017430:Prostate-Specific Antigen