Gefitinib and the modulation of the signaling pathways downstream of epidermal growth factor receptor in human liver cancer cells.
BACKGROUND
The transforming growth factor-alpha (TGF-alpha)/epidermal growth factor receptor (EGFR) signaling pathway has been demonstrated to have a pivotal role in hepatocarcinogenesis. We examined whether abrogation of the TGF-alpha/EGFR signaling pathway with a selective EGFR tyrosine kinase inhibitor, gefitinib, could inhibit the proliferation of human hepatocellular carcinoma (HCC) cells.


METHODS
Cellular growth was monitored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Cell-cycle distribution was analyzed by flow cytometric analysis. Activities of signaling molecules were evaluated by Western blot analysis.


RESULTS
HCC cells expressed EGFR at variable levels; however, extracellular signal-regulated kinase (ERK)1/2 and AKT, key signaling molecules downstream of EGFR, were not constitutively active in the cells. When HCC cells were treated with TGF-alpha, cellular growth was accelerated in a manner dependent on activation of ERK1/2 and AKT. When the cells were co-treated with gefitinib and TGF-alpha, enhanced proliferation and activation of ERK1/2 and AKT were canceled, and the cell-cycle promotion by TGF-alpha was inhibited by co-treatment with gefitinib and TGF-alpha, independently of expression levels of EGFR. In contrast, gefitinib did not show an antiproliferative effect on HCC cells cultivated under the 10% serum condition.


CONCLUSIONS
The present data demonstrated that gefitinib exerted an antiproliferative action on HCC cells under a limited condition when signaling pathways downstream of EGFR were activated by TGF-alpha.
Second Department of Internal Medicine, Tottori University School of Medicine, 36-1 Nishi-cho, Yonago 683-8504, Japan.
Jun-Ichi
J
Okano
Kazuya
K
Matsumoto
Takakazu
T
Nagahara
Yoshikazu
Y
Murawaki
D066246:ErbB Receptors / Q000032:analysis / Q000502:physiology*; D000077156:Gefitinib; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077156:Gefitinib