Nongenomic oestrogen signalling in oestrogen receptor negative breast cancer cells: a role for the angiotensin II receptor AT1

Breast cancer and the renin-angiotensin system (RAS): Therapeutic approaches and related metabolic diseases

The Renin-Angiotensin System (RAS) is classically recognized for regulating blood pressure and fluid balance. Recently, this role has extended to other areas including inflammation, obesity, diabetes, as well as breast cancer. RAS components are expressed in normal and cancerous breast tissues, and downregulation of RAS inhibits metastasis, proliferation, angiogenesis, and desmoplasia in the tumor microenvironment. Therefore, RAS inhibitors (Angiotensin receptor blockers, ARBs, or angiotensin converting enzyme inhibitors, ACE-I) may be beneficial as preventive adjuvant therapies to thwart breast cancer development and improve outcomes, respectively. Given the beneficial effects of RAS inhibitors in metabolic diseases, which often co-exist in breast cancer patients, combining RAS inhibitors with other breast cancer therapies may enhance the effectiveness of current treatments. This review scrutinizes above associations, to advance our understanding of the role of RAS in breast cancer and its potential for repurposing of RAS inhibitors to improve the therapeutic approach for breast cancer patients.

Nongenetic engineering strategies for regulating receptor oligomerization in living cells

Nongenetic strategies for regulating receptor oligomerization in living cells based on DNA, protein, small molecules and physical stimuli.

Correction to: Nongenomic oestrogen signalling in oestrogen receptor negative breast cancer cells: a role for the angiotensin II receptor AT1

After the publication of this work [1] errors were noticed in the total protein loading controls for Figs. 1C, 2B, 3B and 4B.

A Rat Model to Study the Effects of Diet-Induced Obesity on Radiation-Induced Mammary Carcinogenesis

A detailed understanding of the relationship between radiation-induced breast cancer and obesity is needed for appropriate risk management and to prevent the development of a secondary cancer in patients who have been treated with radiation. Our goal was to develop an animal model to study the relationship by combining two existing Sprague-Dawley rat models of radiation-induced mammary carcinogenesis and diet-induced obesity. Female rats were fed a high-fat diet for 4 weeks and categorized as obesity prone or obesity resistant based on their body weight at 7 weeks of age, at which time the rats were irradiated with 4 Gy. Control rats were fed a standard diet and irradiated at the same time and in the same manner. All rats were maintained on their initial diets and assessed for palpable mammary cancers once a week for the next 30 weeks. The obesity-prone rats were heavier than those in the other groups. The obesity-prone rats were also younger than the other animals at the first detection of mammary carcinomas and their carcinoma weights were greater. A tendency toward higher insulin and leptin blood levels were observed in the obesity-prone rats compared to the other two groups. Blood angiotensin II levels were elevated in the obesity-prone and obesity-resistant rats. Genes related to translation and oxidative phosphorylation were upregulated in the carcinomas of obesity-prone rats. Expression profiles from human breast cancers were used to validate this animal model. As angiotensin is potentially an important factor in obesity-related morbidities and breast cancer, a second set of rats was fed in a similar manner, irradiated and then treated with an angiotensin-receptor blocker, losartan and candesartan. Neither blocker altered mammary carcinogenesis; analyses of losartan-treated animals indicated that expression of renin in the renal cortex and of Agtr1a (angiotensin II receptor, type 1) in cancer tissue was significantly upregulated, suggesting the presence of compensating mechanisms for blocking angiotensin-receptor signaling. Thus, obesity-related elevation of insulin and leptin blood levels and an increase in available energy may facilitate sustained protein synthesis in cancer cells, which is required for rapid cancer development.

ERK/CANP rapid signaling mediates 17β-estradiol-induced proliferation of human breast cancer cell line MCF-7 cells

OBJECTIVE

17β-estradiol (E2) exerts its functions through both genomic and non-genomic signaling pathways. Because E2 is important in breast cancer development, we investigated whether its actions in promoting breast cancer cell proliferation occur through the non-genomic signaling pathway via extracellular signal-regulated kinase 1/2 (ERK1/2)/calcium-activated neutral protease (CANP).

METHODS

MCF-7 breast cancer cells were treated with ERKl/2 inhibitor (PD98059) or CANP inhibitor (calpeptin) before exposure to 1×10(-8) M E2. MTT colorimetry and flow cytometry were used to analyze effects on cell proliferation and cell cycle progression, respectively. Expression of phosphorylated-ERK (p-ERK), total ERK, and Capn4 proteins were assessed by Western blotting.

RESULTS

Cell proliferation increased in cells treated with E2 for 24 h (P<0.05), and the proportion of cells in G0/G1 was decreased, accompanied by accelerated G1/S. Calpeptin pre-treatment significantly inhibited the E2-induced proliferation of MCF-7 cells (P<0.05), while also ameliorating the effects of E2 on cell cycle progression. Further, expression of p-ERK was rapidly up-regulated (after 10 min) by E2 (P<0.05), an effect that persisted 16 h after E2 exposure but which was significantly inhibited by PD98059 (P<0.05).

CONCLUSIONS

Finally, expression of Capn4 protein was rapidly up-regulated in E2-exposed cells (P<0.05), but this change was significantly inhibited by PD98059 or calpeptin (P<0.05) pre-treatment. Thus, the rapid, non-genomic ERK/CANP signaling pathway mediates E2-induced proliferation of human breast cancer cells.

The renin-angiotensin system in the breast and breast cancer

Much evidence now suggests that angiotensin II has roles in normal functions of the breast that may be altered or attenuated in cancer. Both angiotensin type 1 (AT1) and type 2 (AT2) receptors are present particularly in the secretory epithelium. Additionally, all the elements of a tissue renin-angiotensin system, angiotensinogen, prorenin and angiotensin-converting enzyme (ACE), are also present and distributed in different cell types in a manner suggesting a close relationship with sites of angiotensin II activity. These findings are consistent with the concept that stromal elements and myoepithelium are instrumental in maintaining normal epithelial structure and function. In disease, this system becomes disrupted, particularly in invasive carcinoma. Both AT1 and AT2 receptors are present in tumours and may be up-regulated in some. Experimentally, angiotensin II, acting via the AT1 receptor, increases tumour cell proliferation and angiogenesis, both these are inhibited by blocking its production or function. Epidemiological evidence on the effect of expression levels of ACE or the distribution of ACE or AT1 receptor variants in many types of cancer gives indirect support to these concepts. It is possible that there is a case for the therapeutic use of high doses of ACE inhibitors and AT1 receptor blockers in breast cancer, as there may be for AT2 receptor agonists, though this awaits full investigation. Attention is drawn to the possibility of blocking specific AT1-mediated intracellular signalling pathways, for example by AT1-directed antibodies, which exploit the possibility that the extracellular N-terminus of the AT1 receptor may have previously unsuspected signalling roles.

The renin-angiotensin system and cancer: old dog, new tricks

For cancers to develop, sustain and spread, the appropriation of key homeostatic physiological systems that influence cell growth, migration and death, as well as inflammation and the expansion of vascular networks are required. There is accumulating molecular and in vivo evidence to indicate that the expression and actions of the renin-angiotensin system (RAS) influence malignancy and also predict that RAS inhibitors, which are currently used to treat hypertension and cardiovascular disease, might augment cancer therapies. To appreciate this potential hegemony of the RAS in cancer, an expanded comprehension of the cellular actions of this system is needed, as well as a greater focus on translational and in vivo research.

Expression of estrogenicity genes in a lineage cell culture model of human breast cancer progression

TaqMan Gene Expression assays were used to profile the mRNA expression of estrogen receptor (ERalpha and ERbeta) and estrogen metabolism enzymes including cytosolic sulfotransferases (SULT1E1, SULT1A1, SULT2A1, and SULT2B1), steroid sulfatase (STS), aromatase (CYP19), 17beta-hydroxysteroid dehydrogenases (17betaHSD1 and 2), CYP1B1, and catechol-O-methyltransferase (COMT) in an MCF10A-derived lineage cell culture model for basal-like human breast cancer progression and in ERalpha-positive luminal MCF7 breast cancer cells. Low levels of ERalpha and ERbeta mRNA were present in MCF10A-derived cell lines. SULT1E1 mRNA was more abundant in confluent relative to subconfluent MCF10A cells, a non-tumorigenic proliferative breast disease cell line. SULT1E1 was also expressed in preneoplastic MCF10AT1 and MCF10AT1K.cl2 cells, but was markedly repressed in neoplastic MCF10A-derived cell lines as well as in MCF7 cells. Steroid-metabolizing enzymes SULT1A1 and SULT2B1 were only expressed in MCF7 cells. STS and COMT were widely detected across cell lines. Pro-estrogenic 17betaHSD1 mRNA was most abundant in neoplastic MCF10CA1a and MCF10DCIS.com cells, while 17betaHSD2 mRNA was more prominent in parental MCF10A cells. CYP1B1 mRNA was most abundant in MCF7 cells. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) induced SULT1E1 and CYP19 mRNA but suppressed CYP1B1, STS, COMT, 17betaHSD1, and 17betaHSD2 mRNA in MCF10A lineage cell lines. In MCF7 cells, TSA treatment suppressed ERalpha, CYP1B1, STS, COMT, SULT1A1, and SULT2B1 but induced ERbeta, CYP19 and SULT2A1 mRNA expression. The results indicate that relative to the MCF7 breast cancer cell line, key determinants of breast estrogen metabolism are differentially regulated in the MCF10A-derived lineage model for breast cancer progression.

Ecdysteroids, juvenile hormone and insect neuropeptides: Recent successes and remaining major challenges

In the recent decade, tremendous progress has been realized in insect endocrinology as the result of the application of a variety of advanced methods in neuropeptidome- and receptor research. Hormones of which the existence had been shown by bioassays four decades ago, e.g. bursicon (a member of the glycoprotein hormone family) and pupariation factor (Neb-pyrokinin 2, a myotropin), could be identified, along with their respective receptors. In control of diurnal rhythms, clock genes got company from the neuropeptide Pigment Dispersing Factor (PDF), of which the receptor could also be identified. The discovery of Inka cells and their function in metamorphosis was a true hallmark. Analysis of the genomes of Caenorhabditis elegans, Drosophila melanogaster and Apis mellifera yielded about 75, 100 and 200 genes coding for putative signaling peptides, respectively, corresponding to approximately 57, 100 and 100 peptides of which the expression could already be proven by means of mass spectrometry. The comparative approach invertebrates-vertebrates recently yielded indications for the existence of counterparts in insects for prolactin, atrial natriuretic hormone and Growth Hormone Releasing Hormone (GRH). Substantial progress has been realized in identifying the Halloween genes, a membrane receptor(s) for ecdysteroids, a nuclear receptor for methylfarnesoate, and dozens of GPCRs for insect neuropeptides. The major remaining challenges concern the making match numerous orphan GPCRs with orphan peptidic ligands, and elucidating their functions. Furthermore, the endocrine control of growth, feeding-digestion, and of sexual differentiation, in particular of males, is still poorly understood. The finding that the prothoracic glands produce an autocrine factor with growth factor-like properties and secrete proteins necessitates a reevaluation of their role in development.

Estradiol stimulates transcription of nuclear respiratory factor-1 and increases mitochondrial biogenesis

Estrogen has direct and indirect effects on mitochondrial activity, but the mechanisms mediating these effects remain unclear. Others reported that long-term estradiol (E(2)) treatment increased nuclear respiratory factor-1 (NRF-1) protein in cerebral blood vessels of ovariectomized rats. NRF-1 is a transcription factor that regulates the expression of nuclear-encoded mitochondrial genes, e.g. mitochondrial transcription factor A (TFAM), that control transcription of the mitochondrial genome. Here we tested the hypothesis that E(2) increases NRF-1 transcription resulting in a coordinate increase in the expression of nuclear- and mitochondrial- encoded genes and mitochondrial respiratory activity. We show that E(2) increased NRF-1 mRNA and protein in MCF-7 breast and H1793 lung adenocarcinoma cells in a time-dependent manner. E(2)-induced NRF-1 expression was inhibited by the estrogen receptor (ER) antagonist ICI 182,780 and actinomycin D but not by phosphoinositide-3 kinase and MAPK inhibitors, indicating a genomic mechanism of E(2) regulation of NRF-1 transcription. An estrogen response element (ERE) in the NRF-1 promoter bound ER alpha and ER beta in vitro, and E(2) induced ER alpha and ER beta recruitment to this ERE in chromatin immunoprecipitation assays in MCF-7 cells. The NRF-1 ERE activated reporter gene expression in transfected cells. Small interfering RNA to ER alpha and ER beta revealed that ER alpha mediates E(2)-induced NRF-1 transcription. The E(2)-induced increase in NRF-1 was followed by increased TFAM and the transcription of Tfam-regulated mitochondrial DNA-encoded COI and NDI genes and increased mitochondrial biogenesis. Knockdown of NRF-1 blocked E(2) stimulation of mitochondrial biogenesis and activity, indicating a mechanism by which estrogens regulate mitochondrial function by increasing NRF-1 expression.

IGF-I plus E2 induces proliferation via activation of ROS-dependent ERKs and JNKs in human breast carcinoma cells

Induction of 17beta-estradiol (E2) and insulin-like growth factor-I (IGF-I) has been detected in breast carcinoma, however the interaction between E2 and IGF-I in the proliferation of breast carcinoma cells is still unclear. In the present study, we found that IGF-I enhances the E2-induced proliferation in MCF-7 human breast carcinoma cells in accordance with stimulation of colony formation via a soft agar assay. Activation of insulin receptor substrate-1 (IRS-1) protein and extracellular signal-related kinases (ERKs) and c-Jun N-terminal kinases (JNKs), but not p38 mitogen-activated protein kinase (MAPK), via phosphorylation induction was detected in MCF-7 cells treated with IGF-I plus E2 (E2/IGF-I). E2/IGF-I-induced proliferation was blocked by chemical inhibitors of ERKs (PD98059) and JNKs (SP600125). An increase in the expression of c-Jun protein was detected in E2/IGF-I-treated MCF-7 cells, and this was inhibited by PD98059 and SP600125. Transfection of the dominant negative MEKK and JNK plasmids significantly reduced E2/IGF-I-induced proliferation with suppression of c-Jun protein expression. An increase in peroxide production was detected in E2/IGF-I-treated cells, and N-acetyl-L-cysteine (NAC) and Tiron (TIR) addition significantly inhibited E2/IGF-I-induced cell proliferation with blocking of the phosphorylation of ERKs and JNKs, and the expression of c-Jun protein. Additionally, 3-OH flavone, baicalein, and quercetin showed effective inhibitory activities against E2/IGF-I-induced proliferation through suppressing proliferative events such as phosphorylation of IRS-1, ERKs, and JNKs proteins, and induction of c-Jun protein and colony formation. These results indicate that IGF-I interacts with E2 to promote the proliferation of breast carcinoma cells via ROS-dependent MAPK activation and c-Jun protein expression. The structure-related inhibition of E2/IGF-I-induced proliferative events by flavonoids is elucidated.

Characterisation of the fibrinogenolytic properties of the buccal gland secretion from Lampetra japonica

Lampetra japonica is representative of the ancient cyclostomota class of animals, and its buccal gland secretion (called lamphredin) is known to act as an anticoagulant. In this study, it was observed by both native-PAGE and SDS-PAGE that the secretion mainly contained two protein bands, buccal gland secretion protein-1 (BGSP-1, 159,909 Da) and buccal gland secretion protein-2 (BGSP-2, 25,660 Da). The N-terminal amino acids of BGSP-1 (EAESF QNLKT RICGG LNGLG) and BGSP-2 (TSVND WKLLD TKLSA NRKVI) were sequenced. Using a Sephadex G-75 column, we isolated BGSP-1, BGSP-2 and small peptides from the buccal gland secretion, but found only BGSP-1 showed fibrinogenolytic activity. BGSP-1 and lamphredin were found to rapidly degrade the alpha chain of human fibrinogen, slowly degrade the beta chain and hardly degrade the gamma chain. BGSP-1 and lamphredin showed a similar map by SDS-PAGE for the degradation of fibrinogen by cleavage at Ala(10)-Glu(11) and His(368)-Ser(369). BGSP-1 was also found to hydrolyze neuronal protein tau at Glu(12)-Asp(13) and Gln(244)-Thr(245). Further study showed that lamphredin and BGSP-1 were inactivated in the presence of a metal chelating agent EDTA. However, addition of Ca(2+) or Mg(2+) but not Zn(2+) restored the fibrinogenolytic activity. This suggests that BGSP-1 acts in the buccal gland as a metalloproteinase with a broad substrate specificity. Furthermore, the secretion showed cytolytic properties towards human SH-SY5Y and HeLa cells in culture, and lamphredin at a 50-fold dilution induced cell death.