title: Targeted therapy with a cytotoxic somatostatin analog, AN-238, inhibits growth of human experimental endometrial carcinomas expressing multidrug resistance protein MDR-1.
abstract: BACKGROUND
  Chemoresistance mediated by membrane transporters such as multidrug resistance (MDR-1) glycoprotein remains a challenge in the chemotherapy treatment of advanced or recurrent endometrial carcinoma. Targeted chemotherapy might overcome this resistance. The cytotoxic somatostatin (SST) analog, AN-238, consists of a superactive derivative of doxorubicin (DOX), 2-pyrrolino-DOX (AN-201), linked to the SST analog carrier, RC-121. This conjugate binds strongly to SST receptor subtypes (sst) 2a (sst2(a)) and 5 (sst(5)) and can be targeted to tumors that express these receptors.
  
  
  METHODS
  The presence of sst2(a) and sst(5) was determined in 3 human endometrial carcinoma cell lines (HEC-1A, RL-95-2, and AN3CA). Nude mice bearing xenografts of these cancers were treated with AN-238 and its radical, AN-201. The antitumor effects and toxicity were compared. The authors studied the effects of AN-238 and AN-201 on the expression levels of MDR-1, multidrug resistance related protein (MRP-1), and breast carcinoma resistance protein (BCRP) by real-time polymerase chain reaction.
  
  
  RESULTS
  The authors demonstrated the presence of mRNA and receptor protein for sst(2a) and sst(5) on HEC-1A, RL-95-2, and AN3CA tumors. AN-238 significantly (P < 0.05) inhibited the growth of these tumors, whereas AN-201 had no effect. Blockade of SST receptors nullified the effects of AN-238. In all 3 endometrial carcinoma lines, AN-238 caused a weaker induction of MDR-1 than AN-201. No major induction of MRP-1 and BCRP occurred after treatment with AN-238 or AN-201.
  
  
  CONCLUSIONS
  Targeted chemotherapy with the cytotoxic SST analog, AN-238, inhibited powerfully the growth of endometrial carcinoma, which express SST receptors, regardless of their expression level of MDR-1.
authors.affiliation: Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center, New Orleans, LA 70112, USA.
authors.forename: Jorg B
authors.initials: JB
authors.lastname: Engel
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Schally
authors.forename: Gabor
authors.initials: G
authors.lastname: Halmos
authors.forename: Ben
authors.initials: B
authors.lastname: Baker
authors.forename: Attila
authors.initials: A
authors.lastname: Nagy
authors.forename: Gunhild
authors.initials: G
authors.lastname: Keller
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000368:Aged; D000818:Animals; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000009:adverse effects / Q000031:analogs & derivatives / Q000494:pharmacology / Q000627:therapeutic use; D016889:Endometrial Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D051379:Mice; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics; D009368:Neoplasm Transplantation; D011758:Pyrroles / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use; D012333:RNA, Messenger / Q000032:analysis; D017481:Receptors, Somatostatin / Q000032:analysis / Q000235:genetics; D013004:Somatostatin / Q000032:analysis / Q000235:genetics; D014183:Transplantation, Heterologous
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D004317:Doxorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D011758:Pyrroles; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; D013004:Somatostatin; C116614:ABCG2 protein, human; C110845:AN 238; C421109:multidrug resistance-associated protein 1