Angiotensin II and epidermal growth factor receptor cross-talk mediated by a disintegrin and metalloprotease accelerates tumor cell proliferation of hepatocellular carcinoma cell lines.
OBJECTIVE
The cross-talk pathway between angiotensin II (AngII) and the epidermal growth factor receptor (EGFR) mediated by epidermal growth factor (EGF)-like ligands cleaved by a disintegrin and metalloprotease (ADAM) has been elucidated in several cell types. Even though the liver is a representative angiotensinogen-producing organ, such cross-talk has never been elucidated in hepatocellular carcinomas (HCCs). We investigated whether AngII exerted a mitogenic effect on HCC cell lines through the AngII-EGFR cross-talk pathway.


METHODS
We determined the expression and/or phosphorylation status of AngII receptor type 1 (AGTR1), ADAM9, ADAM17, ERK1/2, STAT3, AKT and EGFR in five HCC cell lines using Western blotting. Proliferation and invasion activities were measured by ATP and Matrigel invasion assays, respectively.


RESULTS
AGTR1 was expressed ubiquitously in HCC cell lines. EGFR expression in HepG2 was relatively weaker than that in the remaining HCC cell lines. The phosphorylation status of EGFR, ERK1/2, STAT3 and AKT was upregulated by AngII treatment in two EGFR-overexpressing cell lines (Huh7 and PLC/PRF/5), but not in HepG2 (showing weak EGFR expression). AngII stimulation significantly accelerated proliferation and invasion activities in Huh7 and PLC/PRF/5, and was inhibited by pretreatment with an ADAM inhibitor. A selective AGTR1 blocker significantly repressed proliferation activity in both cell lines, but did not significantly repress the invasion activity. Both chemical agents and neutralizing antibodies against ADAMs (ADAM9 and ADAM17) and EGF-like ligands suppressed EGFR transactivation and/or subsequent phosphorylation of ERK1/2, STAT3 and AKT.


CONCLUSIONS
These results suggest that AngII-EGFR cross-talk signaling mediated by ADAMs is involved in the proliferation and invasion activities of several HCC cell lines.
Itabashi
Hidenori
H
Departments of Pathology and Surgery, School of Medicine, Iwate Medical University, Morioka, Japan.
Maesawa
Chihaya
C
Oikawa
Hiroki
H
Kotani
Koji
K
Sakurai
Eiichi
E
Kato
Kuniyuki
K
Komatsu
Hideaki
H
Nitta
Hiroyuki
H
Kawamura
Hidenobu
H
Wakabayashi
Go
G
Masuda
Tomoyuki
T