Suppression of proHB-EGF carboxy-terminal fragment nuclear translocation: a new molecular target therapy for gastric cancer.
OBJECTIVE
Inactivation of epidermal growth factor (EGF) receptor (EGFR) represents a promising strategy for the development of selective therapies against epithelial cancers and has been extensively studied as a molecular target for cancer therapy. However, little attention has been paid to remnant cell-associated domains created by cleavage of EGFR ligands. The present study focused on recent findings that cleavage of membrane-anchored heparin-binding EGF-like growth factor (proHB-EGF), an EGFR ligand, induces translocation of the carboxyl-terminal fragment (CTF) of HB-EGF from the plasma membrane to the nucleus and regulates cell cycle.


METHODS
Two gastric cancer cell lines, MKN28 and NUGC4, were used. KB-R7785, an inhibitor of proHB-EGF shedding, was used to suppress HB-EGF-CTF nuclear translocation with cetuximab, which inhibits EGFR phosphorylation. Cell growth was analyzed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay, apoptosis was evaluated by assay of caspase-3 and caspase-7, and cell cycle was investigated by flow cytometry.


RESULTS
Immunofluorescence study confirmed that KB-R7785 inhibited HB-EGF-CTF nuclear translocation under conditions of proHB-EGF shedding induction by 12-O-tetradecanoylphorbol-13-acetate in gastric cancer cells. KB-R7785 inhibited cell growth in a dose-dependent manner and high-dose KB-R7785 induced apoptosis. Moreover, KB-R7785 induced cell cycle arrest and increased sub-G1 DNA content. KB-R7785 suppressed cyclin A and c-Myc expression. All effects of KB-R7785 were reinforced by combination with cetuximab.


CONCLUSIONS
These results suggest that both inhibition of EGFR phosphorylation and inhibition of HB-EGF-CTF nuclear translocation play crucial roles in inhibitory regulation of cancer cell growth. Suppression of HB-EGF-CTF nuclear translocation might offer a new strategy for treating gastric cancer.
Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
Takaya
T
Shimura
Hiromi
H
Kataoka
Naotaka
N
Ogasawara
Eiji
E
Kubota
Makoto
M
Sasaki
Satoshi
S
Tanida
Takashi
T
Joh
D051722:ADAM Proteins / Q000378:metabolism; D000072199:ADAM12 Protein; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D000068818:Cetuximab; D016503:Drug Delivery Systems; D004353:Drug Evaluation, Preclinical; D066246:ErbB Receptors / Q000378:metabolism; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D010446:Peptide Fragments / Q000378:metabolism; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000473:pathology
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D006877:Hydroxamic Acids; D036341:Intercellular Signaling Peptides and Proteins; C107086:KB R7785; D051741:Kruppel-Like Transcription Factors; D008565:Membrane Proteins; D010446:Peptide Fragments; D000075722:Promyelocytic Leukemia Zinc Finger Protein; C092037:ZBTB16 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C000606480:ADAM12 protein, human; D000068818:Cetuximab; D005998:Glycine