title: Inhibition of proliferation of small intestinal and bronchopulmonary neuroendocrine cell lines by using peptide analogs targeting receptors.
abstract: BACKGROUND
  Currently, no consistently effective therapy is available to inhibit cell proliferation or metastasis of neuroendocrine tumor (NET) disease. The effects of 4 novel peptides were analyzed: a targeted cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH) analog (AN-152), a targeted cytotoxic analog of somatostatin (AN-238), and 2 antagonists of growth hormone-releasing hormone (GH-RH) on 3 NET (carcinoid) cell lines that expressed respective peptide receptors.
  
  
  METHODS
  The effects of the compounds were evaluated on cell proliferation in vitro using MTT uptake and Ki67 expression, apoptosis (caspase 3 expression and activity), and cell cycle parameters (DNA distribution).
  
  
  RESULTS
  Proliferation of the LH-RH receptor-expressing lung NET, NCI-H720 line, was inhibited 2-fold by AN-152 containing doxorubicin compared with the chemotherapy alone (IC50 of 9.1 nM vs 24 nM). This was associated with a reduction in Ki67 transcript and an increase in both caspase 3 mRNA levels and activity. Proliferation of the GH-RH receptor expressing lung NET, NCI-H727 line, was inhibited by both GH-RH antagonists, the effects being mediated through changes in Ki67 expression, but not in caspase 3-mediated apoptosis. The small intestinal NET, KRJ-I line, was 8x more sensitive to inhibition by AN-238 than to 2-pyrolino-doxorubicin, reflected by increased caspase 3 transcript as well as activity. AN-238-mediated growth inhibition culminated in complete G1 arrest.
  
  
  CONCLUSIONS
  The data demonstrate GH-RH antagonists or peptide-linked antineoplastic agents such as AN-152 and AN-238 are effective inhibitors of NET proliferation in vitro. Because peptide receptors such as those for GH-RH, LH-RH, and SST subtypes are commonly expressed by NETs, the development of antineoplastic agents targeted to specific tumor receptors may provide a more efficacious strategy than systemic chemotherapeutic agents currently in use.
authors.affiliation: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, New Haven, Connecticut 06520-8062, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Kidd
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Schally
authors.forename: Roswitha
authors.initials: R
authors.lastname: Pfragner
authors.forename: Maximillian V
authors.initials: MV
authors.lastname: Malfertheiner
authors.forename: Irvin M
authors.initials: IM
authors.lastname: Modlin
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001984:Bronchial Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002276:Carcinoid Tumor / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D003603:Cytotoxins / Q000494:pharmacology; D004317:Doxorubicin / Q000031:analogs & derivatives / Q000494:pharmacology; D005434:Flow Cytometry; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors*; D006801:Humans; D007414:Intestinal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D019394:Ki-67 Antigen / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011758:Pyrroles / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011966:Receptors, LHRH / Q000037:antagonists & inhibitors; D017481:Receptors, Somatostatin / Q000037:antagonists & inhibitors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: C110845:AN 238; D003603:Cytotoxins; D019394:Ki-67 Antigen; D011758:Pyrroles; D012333:RNA, Messenger; D011966:Receptors, LHRH; D017481:Receptors, Somatostatin; C080883:LHRH, lysine(6)-doxorubicin; D007987:Gonadotropin-Releasing Hormone; D004317:Doxorubicin; D013007:Growth Hormone-Releasing Hormone; D053148:Caspase 3