Expression of endothelin-1 immunoreactivity in breast cancer

Deepening the Whole Transcriptomics of Bovine Liver Cells Exposed to AFB1: A Spotlight on Toll-like Receptor 2

Aflatoxin B1 (AFB1) is a food contaminant metabolized mostly in the liver and leading to hepatic damage. Livestock species are differently susceptible to AFB1, but the underlying mechanisms of toxicity have not yet been fully investigated, especially in ruminants. Thus, the aim of the present study was to better characterize the molecular mechanism by which AFB1 exerts hepatotoxicity in cattle. The bovine fetal hepatocyte cell line (BFH12) was exposed for 48 h to three different AFB1 concentrations (0.9 µM, 1.8 µM and 3.6 µM). Whole-transcriptomic changes were measured by RNA-seq analysis, showing significant differences in the expression of genes mainly involved in inflammatory response, oxidative stress, drug metabolism, apoptosis and cancer. As a confirmatory step, post-translational investigations on genes of interest were implemented. Cell death associated with necrosis rather than apoptosis events was noted. As far as the toxicity mechanism is concerned, a molecular pathway linking inflammatory response and oxidative stress was postulated. Toll-Like Receptor 2 (TLR2) activation, consequent to AFB1 exposure, triggers an intracellular signaling cascade involving a kinase (p38β MAPK), which in turn allows the nuclear translocation of the activator protein-1 (AP-1) and NF-κB, finally leading to the release of pro-inflammatory cytokines. Furthermore, a p38β MAPK negative role in cytoprotective genes regulation was postulated. Overall, our investigations improved the actual knowledge on the molecular effects of this worldwide relevant natural toxin in cattle.

Upregulation of Endothelin-1 May Predict Chemotherapy-Induced Cardiotoxicity in Women with Breast Cancer

As survival in breast cancer patients from newer therapies increases, concerns for chemotherapy-induced cardiotoxicity (CIC) have offset some of these benefits, manifesting as a decline in left ventricular ejection fraction (LVEF). Patients receiving anthracycline-based chemotherapy followed by trastuzumab are at risk for CIC. Previous research evaluating whether clinical biomarkers predict cardiotoxicity has been inconsistent. Recently, angiotensin II type 1 receptor (ATR1) and endothelin 1 (ET1) have been shown to play a role in breast tumor growth. We evaluated ATR1 and ET1 expression in breast cancer tissue and its association with CIC. A total of 33 paraffin-embedded breast tissue specimens from women with breast cancer treated with anthracycline-based chemotherapy and trastuzumab were analyzed by immunohistochemistry (IHC) and qRT-PCR. We found that ET1 expression was increased in patients with an LVEF ≤ 50% (p = 0.032) with a lower LVEF correlating with higher ET1 expression (r = 0.377, p = 0.031). In patients with a change in LVEF of greater than 10%, greater ET1 expression was noted compared to those without a change in LVEF (p = 0.017). Increased ET1 expression in breast tumor tissue is associated with reduced LVEF. Future studies need to examine whether ET1 may be a tissue biomarker that helps predict the risk of developing CIC in women with breast cancer.

Role of Endothelin 1 on Proliferation and Migration of Human MCF-7 Cells

Objective

The aim of this study was to explore the role of endothelin 1 (ET-1) in human breast cancer proliferation and migration and antagonism of endothelin receptor A (ETAR) and endothelin receptor B (ETBR) by using the non-selective dual ETA/ETB receptor antagonist bosentan and determine its anti-proliferative, anti-metastatic, and apoptotic effects demonstrated by nuclear factor kappa B (NF-kB), vascular endothelial growth factor (VEGF), Caspase 3 and Caspase 9 expression on endothelin-induced proliferation of MCF-7 cell line in vitro.

Materials and Methods

A total of 8,000 cells were seeded into e-plates 24 hours after the cells were incubated with or without 10-4 M BOS (1 hour before ET-1 treatment); 10-7, 10-8, and 10-9 M ET-1 for 1-4 days.

Results

Whether ET-1 is present or not in the tumor area, bosentan exerts anti-proliferative effect on breast cancer. However, ET-1 and bosentan group showed important inhibitory effect on tumor migration compared to bosentan alone, which can be attributed to increased activity of ET-1 axis in the presence of ET-1. The imbalance among the NF-kB, caspases, and VEGF, which are predictive factors of carcinogenesis significantly improved after bosentan administration.

Conclusion

Our study definitely demonstrated ET-1 and its critical role in cancer progression with apoptotic and anti-apoptotic pathways (NF-κB) and VEGF expression, and migration analyses were also performed. The second major finding was that bosentan inhibited ET-1-mediated effects on tumor proliferation and migration.

Endothelin-1 (ET-1) induces resistance to bortezomib in human multiple myeloma cells via a pathway involving the ETB receptor and upregulation of proteasomal activity

PURPOSE

Bortezomib (BTZ) is used for the treatment of multiple myeloma (MM). However, a significant proportion of patients may be refractory to the drug. This study aimed to investigate whether the endothelin (ET-1) axis may act as an escape mechanism to treatment with bortezomib in MM cells.

METHODS

NCI-H929 and RPMI-8226 (human MM cell lines) were cultured with or without ET-1, BTZ, and inhibitors of the endothelin receptors. ET-1 levels were determined by ELISA, while the protein levels of its receptors and of the PI3K and MAPK pathways' components by western blot. Effects of ET-1 on cell proliferation were studied by MTT and on the ubiquitin proteasome pathway by assessing the chymotryptic activity of the 20S proteasome in cell lysates.

RESULTS

Endothelin receptors A and B (ETAR and ETBR, respectively) were found to be expressed in both cell lines, with the RPMI-8226 cells that are considered resistant to BTZ, expressing higher levels of ETBR and in addition secreting ET-1. Treatment of the NCI-H929 cells with ET-1 increased proliferation, while co-incubation of these cells with ET-1 and BTZ decreased BTZ efficacy with concomitant upregulation of 20S proteasomal activity. Si-RNA silencing or chemical blockade of ETBR abrogated the protective effects of ET-1. Finally, data suggest that the predominant signaling pathway involved in ET-1/ETBR-induced BTZ resistance in MM cells may be the MAPK pathway.

CONCLUSION

Our data suggest a possible role of the ET-1/ETBR axis in regulating the sensitivity of MM cells to BTZ. Thus, combining bortezomib with strategies to target the ET-1 axis could prove to be a novel promising therapeutic approach in MM.

Expression of endothelin-1 and endothelin-1 receptor A in canine mammary tumours

Endothelins and their receptors have been implicated in numerous diseases and have recently emerged as relevant players in a variety of malignancies. Tumours overexpress the Endothelin-1 (ET-1) and the Endothelin-A receptors (ETAR) and their interaction enhances tumour growth and metastasis by promoting tumour cell survival, proliferation and angiogenesis. In this study we have evaluated the expression of ET-1 and ETAR in 50 canine mammary tumours, compared to normal controls. Results demonstrated a progressive increase in ET-1 and ETAR expression from benign tumour to grade 1 and to grade 2 malignant mammary tumours with a decrease of expression in grade 3 carcinomas. Co-localization of ET-1 and ETAR was observed in benign mammary tumours and in G1 and G2 carcinomas, while absent in G3 carcinomas. Concluding, ET-1/ETAR can be considered reliable markers for evaluating malignancy of canine mammary tumours and could have importance for the development of specific anticancer therapies.

Transcriptional alterations of ET-1 axis and DNA damage in lung tissue of a rat obesity model

Obesity has been implicated in the development of many cancers. This can lead to genome damage, especially in the form of double-strand break, the presence of which is now easily detected through nuclear phosphorylation of histone H2AX (γ-H2AX) focus assay. Recently, the endothelin (ET) axis has also been shown to have a role in the growth and progression of several tumors, including lung cancer. The aim of this study was to evaluate the ET-1 system transcriptional alterations and γ-H2AX in lung tissue of Zucker rats subdivided into obese (O, n=22) and controls (CO, n=18) rats: under either fasting conditions (CO(fc)-O(fc)) or acute hyperglycemia (CO(AH)-O(AH)). Significantly higher prepro-ET-1 (p=0.05) and ET-converting enzyme (ECE)-2 mRNA expression was observed in O with respect to CO. A significant positive association was observed between prepro-ET-1 and ET-A in the whole rat population (p=0.009) or in the obese group alone (p=0.007). The levels of γ-H2AX in O and in O(AH) rats were significantly higher (p=0.019) than in the corresponding CO and CO(AH) rats (p=0.038). The study shows an inappropriate secretion of ET-1 in O animals with a parallel DNA damage in their lungs, providing novel mechanisms by which ET receptor antagonist may exert organ protection.

The endothelin axis in urologic tumors: mechanisms of tumor biology and therapeutic implications

Endothelin (ET)-1 and its receptors ET-A and ET-B, referred to commonly as the endothelin axis, have been identified in various human cancers, especially gynecologic tumors, such as breast cancer or ovarian cancer, but also including urologic tumor entities. They play a key role in tumor growth and progression by influencing critical cancer pathways, such as apoptosis, angiogenesis and proliferation. In prostate cancer, overexpression of the ET-A receptor increases with tumor progression, and clinical trials with selective ET-A receptor antagonists, such as atrasentan (ABT-627), have shown promising early results. In preclinical models of bladder cancer, overexpression of the ET axis has been demonstrated and ET-targeting agents are under investigation. This paper reviews the role of the ET axis in human cancers and focuses on preclinical and clinical studies in urologic tumor entities to further define the role of ET-targeting agents as targeted molecular therapy.

Overexpression of endothelin 1 triggers hepatocarcinogenesis in zebrafish and promotes cell proliferation and migration through the AKT pathway

Hepatocarcinogenesis commonly involves the gradual progression from hepatitis to fibrosis and cirrhosis, and ultimately to hepatocellular carcinoma (HCC). Endothelin 1 (Edn1) has been identified as a gene that is significantly up-regulated in HBx-induced HCC in mice. In this study, we further investigated the role of edn1 in hepatocarcinogenesis using a transgenic zebrafish model and a cell culture system. Liver-specific edn1 expression caused steatosis, fibrosis, glycogen accumulation, bile duct dilation, hyperplasia, and HCC in zebrafish. Overexpression of EDN1 in 293T cells enhanced cell proliferation and cell migration in in vitro and xenotransplantation assays and was accompanied with up-regulation of several cell cycle/proliferation- and migration-specific genes. Furthermore, expression of the unfolded protein response (UPR) pathway-related mediators, such as spliced XBP1, ATF6, IRE1, and PERK, was also up-regulated at both the RNA and protein levels. In the presence of an EDN1 inhibitor or an AKT inhibitor, these increases were diminished and the EDN1-induced migration ability also was disappeared, suggesting that the EDN1 effects act through activation of the AKT pathway to enhance the UPR and subsequently activate the expression of downstream genes. Additionally, p-AKT is enhanced in the edn1 transgenic fish compared to the GFP-mCherry control. The micro RNA miR-1 was found to inhibit the expression of EDN1. We also observed an inverse correlation between EDN1 and miR-1 expression in HCC patients. In conclusion, our data suggest that EDN1 plays an important role in HCC progression by activating the PI3K/AKT pathway and is regulated by miR-1.

Endothelin-1 enriched tumor phenotype predicts breast cancer recurrence

Introduction. Breast cancer recurrence can develop years after primary treatment. Crosstalk between breast cancer cells and their stromal microenvironment may influence tumor progression. Our primary study aim was to determine whether endothelin-1 (ET-1) expression in tumor and stroma predicts breast cancer relapse. The secondary aim was to determine ET-1/endothelin receptor A (ETAR) role on signaling pathways and apoptosis in breast cancer. Experimental Design. Patients with histologically documented stages I-III invasive breast cancer were included in the study. ET-1 expression by immunohistochemistry (IHC) in tumor cells and stroma was analyzed. Association between ET-1 expression and clinical outcome was assessed using multivariate Cox proportional hazard model. Kaplan-Meier curves were used to estimate disease-free survival (DFS). In addition, the effect of ET-1/ETAR on signaling pathways and apoptosis was evaluated in MCF-7 and MDA-MB-231 breast cancer cells. Results. With a median followup of 7 years, ET-1 non-enriched tumor phenotype had a significant association with favorable disease-free survival (HR = 0.16; 95% CI 0.03-0.77; P value <0.02). ER negativity, advanced stage of disease and ET-1-enriched tumor phenotype were all associated with a higher risk for recurrence. Experimental study demonstrated that ET-1 stimulation promoted Akt activation in MCF-7 and MDA-MB-231 cells. Furthermore, silencing of ETAR induced apoptosis in both hormone receptor negative and hormone receptor positive breast cancer cells. Conclusions. We found ET-1 expression in tumor and stroma to be an independent prognostic marker for breast cancer recurrence. Prospective studies are warranted to examine whether ET-1 expression in tumor/stroma could assist in stratifying patients with hormone receptor positive breast cancer for adjuvant therapy.

Endothelin-2, the forgotten isoform: emerging role in the cardiovascular system, ovarian development, immunology and cancer

Endothelin-2 [ET-2; also known as vasoactive intestinal contractor (VIC), in rodents] differs from endothelin-1 (ET-1) by only two amino acids, and unlike the third isoform, endothelin-3 (ET-3), it has the same affinity as ET-1 for both ET(A) and ET(B) receptors. It is often assumed that ET-2 would mimic the actions of the more abundant ET-1 and current pharmacological interventions used to inhibit the ET system would also block the actions of ET-2. These assumptions have focused research on ET-1 with ET-2 studied in much less detail. Recent research suggests that our understanding of the ET family requires re-evaluation. Although ET-2 is very similar in structure as well as pharmacology to ET-1, and may co-exist in the same tissue compartments, there is converging evidence for an important and distinct ET-2 pathway. Specifically is has been demonstrated that ET-2 has a key role in ovarian physiology, with ET-2-mediated contraction proposed as a final signal facilitating ovulation. Furthermore, ET-2 may also have a pathophysiological role in heart failure, immunology and cancer. Comparison of ET-2 versus ET-1 mRNA expression suggests this may be accomplished at the level of gene expression but differences may also exist in peptide synthesis by enzymes such as endothelin converting enzymes (ECEs) and chymase, which may allow the two pathways to be distinguished pharmacologically and become separate drug targets. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

Endothelin receptor-A is required for the recruitment of antitumor T cells and modulates chemotherapy induction of cancer stem cells

BACKGROUND

The endothelin receptor-A (ETRA) plays an important role in tumor cell migration, metastasis, and proliferation. The endothelin receptor B (ETRB) plays a critical role in angiogenesis and the inhibition of anti-tumor immune cell recruitment. Thus dual blockade of ETRA and ETRB could have significant anti-tumor effects.

RESULTS

Dual ETRA/ETRB blockade with macitentan (or the combination of the ETRA and ETRB antagonists BQ123 and BQ788) did not enhance antitumor immune cell recruitment. In vitro studies demonstrate that ETRA inhibition prevents the induction of ICAM1 necessary for immune cell recruitment. When used as a single agent against human tumor xenografts, macitentan demonstrated non-significant anti-tumor activity. However, when used in combination with chemotherapy, macitentan specifically reduced tumor growth in cell lines with CD133+ cancer stem cells. We found that ETRA is primarily expressed on CD133+ CSC in both cell lines and primary human tumor cells. ETRA inhibition of CSC prevented chemotherapy induced increases in tumor stem cells. Furthermore, ETRA inhibition in combination with chemotherapy reduced the formation of tumor spheres.

METHODS

We tested the dual ETRA/ETRB antagonist macitentan in conjunction with (1) an anti-tumor vaccine and (2) chemotherapy, in order to assess the impact of dual ETRA/ETRB blockade on anti-tumor immune cell infiltration and ovarian tumor growth. In vitro murine and human cell line, tumor sphere assays and tumor xenograft models were utilized to evaluate the effect of ETRA/ETRB blockade on cell proliferation, immune cell infiltration and cancer stem cell populations.

CONCLUSIONS

These studies indicate a critical role for ETRA in the regulation of immune cell recruitment and in the CSC resistance to chemotherapy.

Permissive role of endothelin receptors in tumor metastasis

Metastasis remains the major driver of mortality in patients with cancer. The multistep metastatic process requires the concerted actions of several genes and involves tumor cell invasion, epithelial mesenchymal transition (EMT), shedding from primary tumor, intravasation, arrest, extravasation and colonization at a preferential site. Understanding this complex process would provide the basis for the development of molecularly targeted therapeutics aimed at the tumor cell or its interaction with the host microenvironment. The neuropeptide hormones endothelins (specially, ET-1) have been correlated with invasiveness and metastasis of several cancers and high ET-1 levels are associated with decreased disease-specific survival. The mechanism(s) by which ET-1 promotes metastasis are being gradually unraveled. Through preferential binding to cognate receptors (ET(A)R or ET(B)R), ET-1 triggers autocrine and paracrine signaling cascades in tumor, immune and stromal cells, at both primary and distant sites, supporting cancer progression and metastasis. In this review, we will summarize the role of the ET axis in metastasis of different cancers and potential targeting of ET receptors in the therapeutic setting.

The endothelin axis stimulates the expression of pro-inflammatory cytokines and pro-migratory molecules in breast cancer

We investigated the effects of the endothelin-1 (ET-1) receptor dual antagonist (Bosentan®) on the inflammatory cytokines and the chemoattractant molecules associated with breast cancer growth and the development of tumor infiltration in bone explants. Immunocompetent mice implanted with the murine mammary carcinoma 4T1 cells in a skin-fold chamber and treated with Bosentan® had reduced tumor growth (p < .05). ET-1 promoted the secretion of the anti-inflammatory soluble tumor necrosis factor (TNF) receptor and IL12 p40 in vitro. The Bosentan® treatment in vivo was associated with a local increase of the anti-inflammatory IL-1α cytokine concentration and decrease of the pro-inflammatory TNF-α and IL-17 cytokine concentrations (p < .05).

Endothelin receptor antagonism and cancer

The endothelin peptides have an important role in the cancer-stromal interactions that promote tumour growth. Endothelin-1 (ET-1), clinically the most investigated endothelin, is a vital agent in the growth and progression of several tumours including prostate, ovarian, colorectal, bladder, breast and lung carcinomas. ET-1 exerts its effects through the activation of two distinct receptors, ET(A) and ET(B). Once activated, these receptors transmit signals via numerous intracellular signalling pathways. The effects of ET receptor stimulation in cancer cells or cancer-associated cells include proliferation, resistance to apoptosis, angiogenesis, migration and subsequent invasion. At present, the manipulation of the endothelin axis within the pre-clinical setting is the subject of intense investigation. Recent studies into ET receptor antagonism have produced interesting results highlighting the fact that these receptors may provide novel targets for a new generation of chemotherapeutic agents in a variety of cancers.

Endothelin-1 expression correlates with atypical histological features in mammary phyllodes tumours

BACKGROUND AND AIMS

Endothelin-1 expression is increased in infiltrating duct carcinoma and is associated with larger tumour size, higher histological grade and lymphovascular permeation. This has not been evaluated in phyllodes tumours, which are uncommon fibroepithelial lesions with potential for local recurrences or distant metastasis. While the grading of phyllodes tumours depends on a combination of histological parameters, prediction of their behaviour remains difficult.

METHOD

A large series of 461 phyllodes tumours (291 benign, 115 borderline malignant and 55 frankly malignant) were evaluated for endothelin-1 expression in both the epithelial cells and stromal cells by immunohistochemistry; results were correlated with the tumour grade.

RESULTS

For benign phyllodes tumours, the epithelial staining of endothelin was negative, weak, moderate and strong in 6%, 26%, 15% and 53% of cases respectively; results were 4%, 18%, 19% and 59% respectively for borderline and 6%, 18%, 6% and 70% respectively for frankly malignant tumours. For the stromal staining, the negative, weak, moderate and strong staining was 32%, 19%, 18% and 31% respectively for benign phyllodes, 24%, 13%, 10% and 53% respectively for borderline and 8%, 16%, 17% and 59% respectively for frankly malignant tumours. There was correlation between epithelial and stromal staining, and the stromal staining correlated with histological features of stromal cellularity, stromal cell nuclear pleomorphism, margin status and stromal overgrowth.

CONCLUSION

These observations suggest a close relationship between the epithelial and stromal elements in phyllodes tumours; endothelin may play a significant role in the malignant progression of phyllodes tumours.

Expression of endothelin-1 is related to poor prognosis in non-small cell lung carcinoma

The endothelin (ET) system influences tumourigenesis and tumour progression by various mechanisms, including angiogenesis. The aim of this study was to determine whether the expression of endothelin-1 (ET-1) is related to the angiogenic phenomenon in lung cancer and whether it could be involved in its clinical behaviour. Expression of ET-1, endothelin-converting enzyme-1 (ECE-1) and endothelin-receptors ETA and ETB was examined in 201 non-small cell lung carcinoma (NSCLC) and corresponding normal tissues using real-time polymerase chain reaction (RT-PCR). Forty NSCLC were also analysed for vascular endothelial growth factor (VEGF) expression by a competitive-PCR approach to assess whether ET-1 expression was related to this angiogenic factor. A higher number of cases with ET-1, ECE-1 and ETA mRNA expression was observed in malignant lung tumours compared with normal lung tissues (45.7% versus 33% for ET-1 (P < 0.0001); 38.3% versus 16.5% for ECE-1 (P = 0.004); and 42.8% versus 28.5% for ETA (P < 0.0001)). On the other hand, ETB mRNA was higher in normal lung tissues than in tumour samples (58.5% versus 52.8% (P < 0.0001)). Immunohistochemical analysis was also performed in 78 cases, selected from among those with high ET-1 mRNA, to confirm the presence of ET-1 protein and to determine its distribution and localisation. Moreover, an interesting relationship was observed between ET-1 and VEGF mRNA levels (P = 0.02). At univariate analysis, clinical-pathological parameters, such as sex, nodal metastatic involvement and stage, and ET-1 expression were seen to be significant predictors of worse prognosis regarding both overall survival (P = 0.001, P = 0.0003, P = 0.001 and P = 0.03, respectively) and disease-free interval (P = 0.0005, P = 0.0007, P = 0.001 and P = 0.04, respectively). We conclude that ET-1 could be involved in angiogenic phenomena in NSCLC and may represent a further indicator of progression and poor prognosis in this type of cancer, with interesting therapeutic implications.

Expression of endothelin-A-receptor predicts unfavourable response to neoadjuvant chemotherapy in locally advanced breast cancer

Endothelin-1 (ET-1) and its receptors (ET_AR and ET_BR), referred to as the endothelin (ET) axis, are overexpressed in breast carcinomas and appear to influence tumour growth and progression. The objective of this study was to determine the effect of expression of the ET axis in breast carcinomas on response to cytotoxic chemotherapy. The study included 44 patients with locally advanced breast cancer participating in a prospective phase III study evaluating high-dose neoadjuvant chemotherapy of epirubicin and cyclophosphamide. Expression of ET-1, ET_AR and ET_BR was determined by semiquantitative immunohistochemical analysis of breast cancer tissue from prechemotherapy tru-cut biopsies. Immunohistochemical staining was positive for ET-1 in 61.5%, for ET_AR in 35% and for ET_BR in 35.9% of breast carcinomas. Pathological response to chemotherapy was significantly decreased in ET_AR-positive patients (P=0.002). In total, 50% of ET_AR-positive patients as compared to 7.7% of ET_AR-negative patients attained pathologically ‘no change’. Logistic regression confirmed ET_AR as an independent predictive marker for pathological response (P=0.009). These data indicate that increased expression of ET_AR in breast carcinomas is associated with resistance to chemotherapy. Determination of ET_AR status may serve as a predictive marker for identifying patients less likely to be responsive to conventional chemotherapy.

The endothelin system in Morris hepatoma-7777: an endothelin receptor antagonist inhibits growth in vitro and in vivo

1. Plasma concentrations of endothelin are increased in patients with hepatocellular cancer as well as in patients with liver metastasis. However, the impact of these findings remains uncertain. 2. We thus analyzed the endothelin system in a rat hepatoma model (Morris hepatoma 7777) in vitro and in vivo. 3. Our study revealed that tissue concentrations of endothelin-1 (ET-1) and big-ET-1, the precursor of ET-1, were significantly elevated in Morris hepatoma 7777 as compared to normal liver. The ETA receptor density was significantly elevated, whereas the density of the ETB receptor was decreased in Morris hepatoma 7777. 4. We could also demonstrate that hepatoma cells secrete ET-1. 5. Exogenously added ET-1 enhances hepatoma cell growth in a dose-dependent manner. Endothelin receptor antagonists (ETA and combined ETA/ETB receptor antagonists) inhibit tumor cell growth in vitro. Since the combined ETA/ETB receptor antagonist was more effective in vitro, we used this compound also for in vivo studies and could demonstrate that a combined ETA/ETB receptor antagonist is able to reduce hepatoma growth in vivo. 6. In conclusion, the endothelin system is activated in Morris hepatoma 7777 and contributes to hepatoma growth. Since endothelin receptor antagonists are well-tolerated upcoming clinically used drugs without major side effects, our data might provide a new pharmacological approach to reduce hepatoma growth in vivo.

Increased endothelin-1 in colorectal cancer and reduction of tumour growth by ET(A) receptor antagonism

Endothelin-1 (ET-1) is a vasoconstrictor peptide which stimulates proliferation in vitro in different cell types, including colorectal cancer cells. Raised ET-1 levels have been detected both on tissue specimens and in the plasma of patients with cancers. To investigate the role of ET-1 in colorectal cancer: (i) ET-1 plasma levels in patients with colorectal cancer were measured by radioimmunoassay: group 1 = controls (n = 22), group 2 = primary colorectal cancer only (n = 39), group 3 = liver metastases only (n = 26); (ii) ET-1 expression in primary colorectal cancer specimens (n =10) was determined immunohistochemically and (iii) the effect of intraportally infused antagonists to the two ET-1 receptors, ET(A) and ET(B), on the growth of liver metastases in a rat model was assessed. ET-1 plasma levels were significantly increased in both patients with primary tumour and patients with metastases, compared to controls (P < 0.01, 3.9 +/- 1.4, 4.5 +/- 1.5, vs. 2.75 +/- 1.37 pg/ml, respectively). Immunohistochemically, strong expression of ET-1 was found in the cytoplasm, stroma and blood vessels of cancers, unlike the normal colon where only the apical layer of the epithelium, vascular endothelial cells and surrounding stroma were positively stained. In the rat model, there was significant reduction in liver tumour weights compared to controls, following treatment with the ET(A) antagonist (BQ123) 30 min after the intraportal inoculation of tumour cells (P < 0.05). These results suggest ET-1 is produced by colorectal cancers and may play a role in the growth of colorectal cancer acting through ET(A) receptors. ET(A) antagonists are indicated as potential anti-cancer agents.

Augmented expression of endothelin-1, endothelin-3 and the endothelin-B receptor in breast carcinoma

AIMS

Endothelins (ETs) are peptides expressed in many tumours which may stimulate angiogenesis and desmoplasia. Because ETs have not been extensively studied mammary neoplasia, we assessed ET protein and mRNA expression and receptor mRNA expression in normal and neoplastic breast tissues.

METHODS AND RESULTS

Tissues from five normal breasts, six fibroadenomas, seven ductal carcinomas in situ (DCIS) and 25 invasive carcinomas were stained with anti-ET-1 and anti-ET-3 antibodies and analysed using a grading system. ET-1, ET-3, ETA and ETB mRNA expression was assessed by quantitative RT-PCR from eight carcinomas and five normals. Weak staining for ET-1 and ET-3 was detected in all normals. Moderate to strong staining was seen in 72% and 64% of carcinomas for ET-1 and ET-3, respectively. Most fibroadenomas showed weak positivity for ET-1 (83%) and ET-3 (67%). ET-1 and ET-3 mRNA levels were upregulated in carcinomas compared with normal breast. No ETA mRNA was not detected in any tissue. ETB mRNA was detected in normal breast and was increased in carcinomas.

CONCLUSION

These results suggest that the ET system is altered in breast carcinomas and this may be of importance in the progression from in-situ to invasive carcinoma.