Autocrine growth loops dependent on peptidyl alpha-amidating enzyme as targets for novel tumor cell growth inhibitors.
Many small cell lung tumors are dependent in vitro and in vivo on autocrine growth loops. The prototypical small cell lung cancer autocrine growth factor, gastrin-releasing peptide (GRP), is one of many peptide hormones which require post-translational carboxy-terminal alpha-amidation for bioactivity. We have reported that neuroendocrine human lung tumor cell lines express the bifunctional enzyme PAM which catalyzes the biosynthesis of alpha-amidated peptides in a two-step process, and have recently shown that non-small cell lung cancer cell lines and tumors, generally considered to be non-endocrine in nature, also express PAM. We have also shown that two chemical classes of PAM inhibitors, substrate analogues and specific copper chelators, inhibit amidating enzyme activity in cell-free extracts. Here we demonstrate in vitro growth inhibition of lung cancer tumor cell lines by both these classes of PAM inhibitors using the MTT assay and the clonogenic assay. Growth inhibition in a small cell lung cancer cell line can be overcome by exogenous addition of synthetic alpha-amidated GRP. Similar growth-suppressive effects are seen in cell lines stably transfected with a vector expressing antisense PAM RNA. These data support the mechanism of inhibition for a new type of chemotherapeutic/intervention agent, directed at synthesis and activation of peptide growth factors, and support our postulate that alpha-amidated peptide hormones are a common component in lung tumor autocrine growth biology which can be inhibited by targeting the biochemical mechanisms necessary for growth factor synthesis.
Iwai
N
N
Department of Cell and Cancer Biology, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, Bethesda, MD 20892, USA.
Martínez
A
A
Miller
M J
MJ
Vos
M
M
Mulshine
J L
JL
Treston
A M
AM
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects*; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002934:Cinnamates; D017077:Culture Media, Conditioned / Q000378:metabolism; D004050:Ditiocarb / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D006131:Growth Inhibitors / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D006921:Hygromycin B / Q000031:analogs & derivatives / Q000494:pharmacology; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009097:Multienzyme Complexes; D016376:Oligonucleotides, Antisense / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002934:Cinnamates; D017077:Culture Media, Conditioned; D005229:Fatty Acids, Monounsaturated; D006131:Growth Inhibitors; D009097:Multienzyme Complexes; D016376:Oligonucleotides, Antisense; C064180:4-phenyl-3-butenoic acid; D006921:Hygromycin B; C026273:hygromycin A; D004050:Ditiocarb; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase