Enhancement of Aminopeptidase A Expression during Angiotensin II-Induced Choriocarcinoma Cell Proliferation through AT₁Receptor Involving Protein Kinase C- and Mitogen-Activated Protein Kinase-Dependent Signaling Pathway

Abstract

Angiotensin II (Ang II) is a bioactive peptide of the renin-angiotensin system, exerting its actions not only as a vasoconstrictor, but also as a growth promoter. In human placenta, type 1 Ang II receptors (AT(1)R) are predominantly expressed in trophoblasts, and we previously reported that aminopeptidase A (APA), a cell surface peptidase that converts Ang II to Ang III, is also expressed in both normal and neoplastic trophoblasts. However, the roles of Ang II and APA in trophoblast function remain to be clarified. In the present study we examined the effects of Ang II on proliferation and APA expression in trophoblast-like BeWo choriocarcinoma cells. Treatment of BeWo cells with Ang II significantly increased DNA synthesis in a dose-dependent manner. Ang II also enhanced APA mRNA and cell surface expression in BeWo cells analyzed by Northern blotting, flow cytometry, and enzyme activity assay. The Ang II-induced proliferation and APA up-regulation were blocked by the AT(1)R antagonist candesartan, but not by the AT(2)R antagonist PD123319. Furthermore, these Ang II effects were abolished by the protein kinase C inhibitor bisindolylmaleimide I and the MAPK inhibitor PD98059. Immunohistochemistry using choriocarcinoma tissues demonstrated that APA was expressed on the cell surface of AT(1)R-positive cytotrophoblastic cells in vivo. With these findings we demonstrate that Ang II stimulates the proliferation of trophoblastic cells via AT(1)R that are linked to protein kinase C /MAPK-dependent signaling pathways, and that the Ang II-degrading enzyme APA is up-regulated during Ang II-induced cell proliferation. These observations suggest the possible regulatory mechanism by the local renin-angiotensin system, especially the Ang II-AT(1)R-APA system, for the growth of human choriocarcinoma cells.

Angiotensin II type 1 receptor expression in ovarian cancer and its correlation with tumour angiogenesis and patient survival

“…As a negative control, the primary antibody was replaced with normal rabbit IgG or mouse IgG at an appropriate dilution. As positive immunohistochemical controls, marked immunoreactivity of AT 1 R and VEGF in placental trophoblastic tissues was confirmed as reported previously (Shiraishi et al, 1996;Ino et al, 2003). The immunostaining intensity for AT 1 R and VEGF was scored semiquantitatively based on the percent positivity of stained cells on a three-tiered scale as follows: À, negative (no positive cells); þ , focally or weakly positive (o50% positive cells); þ þ , diffusely or strongly positive (450% positive cells).…”

“…It has been reported that AT 1 R is involved in the proliferation of various cancers in vitro and in vivo (Fujimoto et al, 2001;Rivera et al, 2001;Muscella et al, 2002;Ino et al, 2003;Uemura et al, 2003). However, our immunohistochemical study showed that the AT 1 R expression score did not significantly correlate with the positivity of the cellular proliferation marker PCNA in ovarian cancer tissues.…”

Angiotensin II receptor type 1 blockers suppress the cell proliferation effects of angiotensin II in breast cancer cells by inhibiting AT1R signaling

“…Previous studies assessing the relationship between RAS and tumor development have shown that AT1R expression is higher in some tumor types compared to normal tissue (22,23). Other studies have shown that the expression of AT1R is upregulated in several tumor types, including laryngeal, prostate, ovarian, keratoacanthoma, glioma, squamous cell carcinoma, cervical, bladder, choriocarcinoma, pancreatic, endometrial, gastric, and others (5)(6)(7)14,15,(24)(25)(26)(27)(28). In addition, Ang II has been shown to be an important factor in tumor growth and angiogenesis through the activation of AT1R (6,29).…”

“…After combining with AT1R, Ang II can interact with several genes (9)(10)(11)(12) that promote the division and proliferation of tumor cells and inhibit cell differentiation (10,(13)(14)(15). In addition, it has been shown that local Ang II can promote the proliferation of tumor cells (16)(17)(18).…”

Expression of AT1 and AT2 angiotensin receptors in astrocytomas is associated with poor prognosis

“…The polyclonal antirabbit AT1 receptor antibody (306, catalogue SC579) is specific for AT1 and is mouse, rat, and human reactive; it does not show cross-reactivity with AT2 (Lu et al, 1998;Ino et al, 2003Ino et al, , 2006, and AT-2 (Goat polyclonal IgG Santa Cruz Biotechnology Inc.) was 1 : 300 in BSA 1% in PBS.…”