AT1 receptor and ACE mRNA are increased in chemically induced carcinoma of rat mammary gland

Association between AT1 and AT2 angiotensin II receptor expression with cell proliferation and angiogenesis in operable breast cancer

Angiotensin II (ANGII) has been associated with vascular proliferation in tumor and non-tumor models through its receptors AT1 and AT2. Our objective was to determine AT1 and AT2 receptor expression in operable breast cancer and its association with tumor grade, vascular density, and cellular proliferation. Seventy-seven surgically malignant breast tumors with no distant metastasis were included, and 7 benign lesions were used as controls. AT1 and AT2 receptor expression was determined by RT-PCR and immunohistochemistry (IHC) in 68 out of the 77 malignant lesions and in the 7 benign lesions. AT1 and AT2 receptor expression was detected in 35.3 and 25 % of cases, in both RT-PCR and IHC. Tumors that express AT1 showed an increase in T3 stage (92.3 vs. 7.7 % p < 0.001), mitotic index (4 ± 1 vs 2 ± 1, p = 0.05), vascular density (15 ± 3 vs 8 ± 5, p = 0.05), and cellular proliferation (85 ± 18 vs 55 ± 10, p = 0.01) versus AT1-negative lesions. Non-differences between clinical-pathologic variables and AT2 expression were found. AT1 receptor expression was associated to enhance angiogenesis and cellular proliferation rate, but no relationship with AT2 was found. ANGII and its peptides might play a role in the development and pathophysiology of breast cancer, and this could be valuable in the in the development of targeted therapies.

AT1 receptor blockade delays postlactational mammary gland involution: a novel role for the renin angiotensin system

Angiotensin II (AngII), the main effector peptide of the renin-angiotensin system (RAS), participates in multiple biological processes, including cell growth, apoptosis, and tissue remodeling. Since AngII activates, in different cell types, signal transducing pathways that are critical for mammary gland postlactational regression, we investigated the role of the RAS during this process. We found that exogenous administration of AngII in mammary glands of lactating Balb/c mice induced epithelium apoptosis [2.9±0.5% (control) vs. 9.6±1.1% (AngII); P < 0.001] and activation of the proapoptotic factor STAT3, an effect inhibited by irbesartan, an AT(1) receptor blocker. Subsequently, we studied the expression kinetics of RAS components during involution. We found that angiotensin-converting enzyme (ACE) mRNA expression peaked 6 h after weaning (5.7-fold; P<0.01), while induction of angiotensinogen and AT(1) and AT(2) receptors expression was detected 96 h after weaning (6.2-, 10-, and 6.2-fold increase, respectively; P<0.01). To assess the role of endogenously generated AngII, mice were treated with losartan, an AT(1) receptor blocker, during mammary involution. Mammary glands from losartan-treated mice showed activation of the survival factors AKT and BCL-(XL), significantly lower LIF and TNF-α mRNA expression (P<0.05), reduced apoptosis [12.1±2.1% (control) vs. 4.8±0.7% (losartan); P<0.001] and shedding of epithelial cells, inhibition of MMP-9 activity in a dose-dependent manner (80%; P<0.05; with losartan IC(50) value of 6.9 mg/kg/d] and lower collagen deposition and adipocyte invasion causing a delayed involution compared to vehicle-treated mice. Furthermore, mammary glands of forced weaned AT(1A)- and/or AT(1B)-deficient mice exhibited retarded apoptosis of epithelial cells [6.3±0.95% (WT) vs. 3.3±0.56% (AT(1A)/AT(1B) DKO); P<0.05] with remarkable delayed postlactational regression compared to wild-type animals. Taken together, these results strongly suggest that AngII, via the AT(1) receptor, plays a major role in mouse mammary gland involution identifying a novel role for the RAS. angiotensin system.