Cimetidine inhibits epidermal growth factor-induced cell signaling.
BACKGROUND
Cimetidine, a histamine-2 (H2) receptor antagonist, has been demonstrated to have anticancer effects on colorectal cancer, melanoma and renal cell carcinoma. In the current study, we clarified that cimetidine inhibits both epidermal growth factor (EGF)-induced cell proliferation and migration in hepatocellular carcinoma (HCC) cell lines.


METHODS
HCC cell lines (Hep3B, HLF, SK-Hep-1, JHH-2, PLC/PRF/5 and HLE) were used and cell proliferation was assessed by [3H]-thymidine incorporation assay. Cell migration was measured by in vitro cell migration assay. Biological effects of cimetidine were assessed with human EGF receptor (EGFR)-expressing mouse fibroblast cells (NR6-WT). The autophosphorylation of EGFR and the activation of other downstream effectors were analyzed by immunoprecipitation and immunoblotting. The concentration of intracellular cyclic AMP (cAMP) was measured by competitive enzyme immunoassay.


RESULTS
Cimetidine inhibited both EGF-induced cell proliferation and migration in Hep3B, HLF, SK-Hep-1 and JHH-2, while cimetidine did not affect EGF-induced cell proliferation and migration in PLC/PRF/5 and HLE. Cimetidine was revealed to disrupt the EGF-induced autophosphorylation of EGFR and its downstream effectors, mitogen activated protein kinases and phospholipase C-gamma. To define the molecular basis of this negative regulation, we identified that cimetidine significantly decreased intracellular cAMP levels and that decrement of cAMP inhibited autophosphorylation of EGFR. The cell permeable cAMP analog, CPT-cAMPS reversed the cimetidine-induced inhibition of EGF-induced cell proliferation and cell migration by restoring autophosphorylation of EGFR.


CONCLUSIONS
Cimetidine inhibited EGF-induced cell proliferation and migration in HCC cell lines by decreasing the concentration of intracellular cAMP levels. Cimetidine may be a candidate chemopreventive agent for HCC.
Fujikawa
Tatsuya
T
Department of Medicine and Medical Science, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan. tfmty@yahoo.co.jp
Shiraha
Hidenori
H
Nakanishi
Yutaka
Y
Takaoka
Nobuyuki
N
Ueda
Naoki
N
Suzuki
Mayumi
M
Shiratori
Yasushi
Y
D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000473:pathology*; D002465:Cell Movement / Q000187:drug effects* / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects*; D002927:Cimetidine / Q000494:pharmacology* / Q000627:therapeutic use; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors* / Q000502:physiology*; D006635:Histamine H2 Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000473:pathology*; D014407:Tumor Cells, Cultured
D006635:Histamine H2 Antagonists; D004815:Epidermal Growth Factor; D002927:Cimetidine