Endothelin-1 protects ovarian carcinoma cells against paclitaxel-induced apoptosis: requirement for Akt activation

Restoration of miR-648 overcomes 5-FU-resistance through targeting ET-1 in gastric cancer cells in-vitro

BACKGROUND

Endothelin-1 (ET-1) is a peptide overexpressed in gastric cancer (GC) and linked to carcinogenesis and resistance to chemotherapy. Applying microRNAs (miRNAs/miRs) to downregulate ET-1 and reverse resistance to commonly used chemotherapy drugs such as 5-fluorouracil (5-FU) is practical.

METHODS

The current study sought to evaluate the miR-648 expression in GC and any plausibility of its replacement, either with or without the combination of chemo agents to downregulate ET-1 expression through interaction with its target gene. To this end, miR-648 and ET-1 expression levels were assessed in GC tissues and adjacent non-tumor tissues driven from 65 patients who had already undergone surgery, fifteen of which had received 5-FU before surgery. The impact of miR-648 and chemo agents on ET-1 expression was measured using qPCR and Western blotting. Further, an MTT assay was conducted to assess its association with cell viability. Ultimately, the association of miR-648 and ET-1 with clinicopathological characteristics was evaluated.

RESULTS

The current study revealed that miR-648 was considerably down-regulated, while ET-1 was substantially up-regulated in patients with GC. The 5-FU caused a significant increase in miR-648 and reduced ET-1 expression. It was also determined that overexpression of miR-648 suppressed ET-1 production, notably when combined with 5-FU, leading to survival reduction. These results further showed that miR-648 replacement could sensitize chemoresistant GC cells. Besides, a significant association between ET-1 and miR-648 with clinicopathological features was discovered CONCLUSIONS: miR-648 replacement may serve as a potential oncosuppressive therapeutic approach that warrants further investigation to translate into an effective GC treatment.

Patient-Derived Ovarian Cancer Organoids Mimic Clinical Response and Exhibit Heterogeneous Inter- and Intrapatient Drug Responses

There remains an unmet need for preclinical models to enable personalized therapy for ovarian cancer (OC) patients. Here we evaluate the capacity of patient-derived organoids (PDOs) to predict clinical drug response and functional consequences of tumor heterogeneity. We included 36 whole-genome-characterized PDOs from 23 OC patients with known clinical histories. OC PDOs maintain the genomic features of the original tumor lesion and recapitulate patient response to neoadjuvant carboplatin/paclitaxel combination treatment. PDOs display inter- and intrapatient drug response heterogeneity to chemotherapy and targeted drugs, which can be partially explained by genetic aberrations. PDO drug screening identifies high responsiveness to at least one drug for 88% of patients. PDOs are valuable preclinical models that can provide insights into drug response for individual patients with OC, complementary to genetic testing. Generating PDOs of multiple tumor locations can improve clinical decision making and increase our knowledge of genetic and drug response heterogeneity.

Endothelin-1 induces cellular senescence and fibrosis in cultured myoblasts. A potential mechanism of aging-related sarcopenia

Endothelial dysfunction, with increased endothelin-1 (ET-1) synthesis, and sarcopenia, characterized by the loss of muscular mass and strength, are two aging–related conditions. However, a relationship between them has not been already established. The aim of this study was to determine whether ET-1 induces senescence and fibrosis in cultured murine myoblasts, which could be involved in the development of sarcopenia related to aging. For this purpose, myoblasts were incubated with ET-1 to assess cellular senescence, analyzed by senescence associated β-galactosidase activity and p16 expression; and fibrosis, assessed by fibronectin expression. ET-1 induced myoblast senescence and fibrosis through ET_A receptor. The use of antioxidants and several antagonists revealed that ET-1 effect on senescence and fibrosis depended on ROS production and activation of PI₃K-AKT-GSK pathway. To stress the in vivo relevance of these results, circulating ET-1, muscular strength, muscular fibrosis and p16 expression were measured in male C57Bl6 mice from 5-18-24-months-old. Old mice shown high levels of ET-1 correlated with muscular fibrosis, muscular p16 expression and loss of muscle strength. In conclusion, ET-1 promotes fibrosis and senescence in cultured myoblasts, similar results were found in old mice, suggesting a potential role for ET-1 in the development of sarcopenia related to aging.

Human Cardiac Progenitor Cells Enhance Exosome Release and Promote Angiogenesis Under Physoxia

Studies on cardiac progenitor cells (CPCs) and their derived exosomes therapeutic potential have demonstrated only modest improvements in cardiac function. Therefore, there is an unmet need to improve the therapeutic efficacy of CPCs and their exosomes to attain clinically relevant improvement in cardiac function. The hypothesis of this project is to assess the therapeutic potential of exosomes derived from human CPCs (hCPCs) cultured under normoxia (21% O₂), physoxia (5% O₂) and hypoxia (1% O₂) conditions. hCPCs were characterized by immunostaining of CPC-specific markers (NKX-2.5, GATA-4, and c-kit). Cell proliferation and cell death assay was not altered under physoxia. A gene expression qPCR array (84 genes) was performed to assess the modulation of hypoxic genes under three different oxygen conditions as mentioned above. Our results demonstrated that very few hypoxia-related genes were modulated under physoxia (5 genes upregulated, 4 genes down regulated). However, several genes were modulated under hypoxia (23 genes upregulated, 9 genes downregulated). Furthermore, nanoparticle tracking analysis of the exosomes isolated from hCPCs under physoxia had a 1.6-fold increase in exosome yield when compared to normoxia and hypoxia conditions. Furthermore, tube formation assay for angiogenesis indicated that exosomes derived from hCPCs cultured under physoxia significantly increased tube formation as compared to no-exosome control, 21% O₂, and 1% O₂ groups. Overall, our study demonstrated the therapeutic potential of physoxic oxygen microenvironment cultured hCPCs and their derived exosomes for myocardial repair.

Fine-mapping of a novel premenopausal breast cancer susceptibility locus at Chr4q31.22 in Caucasian women and validation in African and Chinese women

We previously identified a novel breast cancer susceptibility variant on chromosome 4q31.22 locus (rs1429142) conferring risk among women of European ancestry. Here, we report replication of findings, validation of the variant in diverse populations and fine-mapping of the associated locus in Caucasian population. The SNP rs1429142 (C/T, minor allele frequency 18%) showed association for the overall breast cancer risk in Stages 1-4 (n = 4,331 cases/4271 controls; p = 4.35 × 10^-8 ; odds ratio, OR_C-allele ,1.25), and an elevated risk among premenopausal women (n = 1,503 cases/4271 controls; p = 5.81 × 10^-10 ; OR_C-allele 1.40) in European populations. SNP rs1429142 was associated with premenopausal breast cancer risk in women of African (T/C; p-value 1.45 × 10^-02 ; OR_C-allele 1.2) but not from Chinese ancestry. Fine-mapping of the locus revealed several potential causal variants which are present within a single association signal, revealed from the conditional regression analysis. Functional annotation of the potential causal variants revealed three putative SNPs rs1366691, rs1429139 and rs7667633 with active enhancer functions inferred based on histone marks, DNase hypersensitive sites in breast cell line data. These putative variants were bound by transcription factors (C-FOS, STAT1/3 and POL2/3) with known roles in inflammatory pathways. Furthermore, Hi-C data revealed several short-range interactions in the fine-mapped locus harboring the putative variants. The fine mapped locus was predicted to be within a single topologically associated domain, potentially facilitating enhancer-promoter interactions possibly leading to the regulation of nearby genes.

Endothelin-1 Augments Therapeutic Potency of Human Mesenchymal Stem Cells via CDH2 and VEGF Signaling

In our previous study, we identified differences in the levels of CDH2 and vascular endothelial growth factor (VEGF) between effective and ineffective clones of human umbilical cord blood (hUCB) mesenchymal stem cells (MSCs), with regard to the infarcted rat myocardium. In this study, we compared gene expression profiles between the effective and ineffective clones and identified that endothelin-1 (EDN1) is enriched in the effective clone. In the mechanistic analyses, EDN1 significantly increased expression of CDH2 and VEGF through endothelin receptor A (EDNRA), which was prevented by EDNRA blocker, BQ123. To decipher how EDN1 induced gene expression of CDH2, we performed a promoter activity assay and identified GATA2 and MZF1 as inducers of CDH2. EDN1 significantly enhanced the promoter activity of the CDH2 gene, which was obliterated by the deletion or point mutation at GATA2 or MZF1 binding sequence. Next, therapeutic efficacy of EDN1-priming of hUCB-MSCs was tested in a rat myocardial infarction (MI) model. EDN1-primed MSCs were superior to naive MSCs at 8 weeks after MI in improving myocardial contractility (p < 0.05), reducing fibrosis area (p < 0.05), increasing engraftment efficiency (p < 0.05), and improving capillary density (p < 0.05). In conclusion, EDN1 induces CDH2 and VEGF expression in hUCB-MSCs, leading to the improved therapeutic efficacy in rat MI, suggesting that EDN1 is a potential priming agent for MSCs in regenerative medicine.

Lipopolysaccharide-Induced Necroptosis of Brain Microvascular Endothelial Cells Can Be Prevented by Inhibition of Endothelin Receptors

Over activation of the endothelin-1 (ET-1) system in disease states contributes to endothelial dysfunction. On the other hand, ET-1 promotes proliferation and survival of endothelial cells. Regulation of programmed cell death (PCD) pathways is critical for cell survival. Recently discovered necroptosis (regulated necrosis) is a pathological PCD mechanism mediated by the activation of toll like receptor 4 (TLR4), which also happens to stimulate ET-1 production in dendritic cells. To establish the effect of ET-1 on PCD and survival of human brain microvascular endothelial cells (BMVECs) under control and inflammatory conditions, BMVECs were treated with ET-1 (10 nM, 100 nM and 1 µM) or lipopolysaccharide (LPS, 100 ng/ml). ET receptors were blocked with bosentan (10 µM). Under normal growth conditions, exogenous ET-1 reduced BMVEC viability and migration at a relatively high concentration (1 µM). This was accompanied with activation of necroptosis and apoptosis marker genes. LPS decreased endogenous ET-1 secretion, increased ETB receptor expression and activated necroptosis. Even though ET-1 levels were low (less than 10 nM levels used under normal growth conditions), blocking of ET receptors with bosentan inhibited the necroptosis pathway and improved the cell migration ability of BMVECs, suggesting that under inflammatory conditions, ET-1 activates PCD pathways in BMVECs even at physiological levels.

Cisplatin suppresses proliferation, migration and invasion of nasopharyngeal carcinoma cells in vitro by repressing the Wnt/β-catenin/Endothelin-1 axis via activating B cell translocation gene 1

PURPOSE

Nasopharyngeal carcinoma (NPC) is one of the most commonly diagnosed cancers worldwide with significantly high prevalence in Southern China. Chemoprevention of cancer with alkylating agent compounds could potentially reverse, suppress, or prevent cancer progression. Cisplatin (CIS) is an antineoplastic or cytotoxic platinum-based drug used for chemotherapy of different types of human cancers such as NPC. Nevertheless, the effects of CIS on the migration and invasion of human NPC cells and the underlying molecular mechanisms have not yet been fully scrutinized.

METHODS

In this work, we tested the effect of CIS on the proliferation, migration and invasion of NPC cells. The results exhibited that this drug exerts remarkable inhibitory effects on the proliferation, migration and invasion of NPC cells in a dose-dependent manner. Western blotting and real time RT-PCR were used for expression analyses.

RESULTS

We found that CIS treatment led to a dose-dependent inhibition of Endothelin-1 (ET1) expression, at protein as well as mRNA levels in NPC cells. CIS was also found to activate the expression of BTG1 in NPC cells. Moreover, mechanistic analyses revealed that CIS increased the expression of B cell translocation gene 1 (BTG1) to suppress the expression of ET1. Furthermore, we show that ET1 could not be induced in CIS-resistant cells with suppressed BTG1 expression, and subsequently demote the proliferation, migration and invasion of NPC cells.

CONCLUSIONS

These findings provided compelling evidence of the role of CIS in suppressing NPC metastasis and its underlying molecular mechanisms.

Macitentan, a double antagonist of endothelin receptors, efficiently impairs migration and microenvironmental survival signals in chronic lymphocytic leukemia

The crosstalk between chronic lymphocytic leukemia (CLL) cells and tumor microenvironment is essential for leukemic clone maintenance, supporting CLL cells survival, proliferation and protection from drug-induced apoptosis. Over the past years, the role of several soluble factors involved in these processes has been studied. CLL cells express higher levels of endothelin 1 (ET-1) and ET_A receptor as compared to normal B cells. Upon ET-1 stimulation, CLL cells improve their survival and proliferation and reduce their sensitivity to the phosphoinositide-3-kinase δ inhibitor idelalisib and to fludarabine. Here, we demonstrate that CLL cells express not only ET_A receptor but also ET_B receptor. ET-1 acts as a homing factor supporting CLL cells migration and adhesion to microenvironmental cells. In addition, ET-1 stimulates a pro-angiogenic profile of CLL cells increasing VEGF expression through hypoxia-inducible factor-1 (HIF-1α) accumulation in CLL cells. Macitentan, a specific dual inhibitor of ET_A and ET_B receptors, targets CLL cells affecting leukemic cells migration and adhesion and overcoming the pro-survival and proliferation signals mediated by microenvironment. Furthermore, macitentan cooperates with ibrutinib inhibiting the BCR pathway and with ABT-199 disrupting BCL2 pathway. Our data describe the biological effects of a new drug, macitentan, able to counteract essential processes in CLL pathobiology as survival, migration, trafficking and drug resistance. These findings envision the possibility to interfere with ET receptors activity using macitentan as a possible novel therapeutic strategy for CLL patients.

Effects of silencing endothelin-1 on invasion and vascular formation in lung cancer

Endothelin-1 (ET-1), which exists not only in the vascular endothelium but is also widely present in various tissues and cells, is an important cardiovascular regulatory factor that serves an important role in maintaining the basal vascular tone and homeostasis in the cardiovascular system. In the present study, the ET-1 gene was silenced by RNA interference, and the effects on lung cancer cell proliferation and tumor cell invasion were then detected by Cell Counting kit-8 and Transwell assays. In addition, the expression of apoptosis, growth and invasion-associated proteins, including RhoA/C, vascular endothelial growth factor, pigment epithelium-derived factor, AKT, E-cadherin and cyclooxygenase-2 was evaluated by western blotting upon silencing ET-1. In the present study, Endostar, a recombinant human endostatin injectable drug, was also used, and it was assessed whether the sensitivity of tumor cells to this drug could be increased by silencing ET-1. Both in vivo and in vivo tests were carried out in the present study. The experimental data indicated that ET-1 silencing can inhibit tumor cell proliferation and invasion, particularly in the presence of Endostar.

Photoperiodic modulation of local melatonin synthesis and its role in regulation of thymic homeostasis in Funambulus pennanti

The effect of photo-neuroendocrine system on the thymic (immune) functions is mediated by gonadal steroid and the pineal hormone melatonin. The present study explored the effect of photoperiod on the thymic melatonergic system and its role in protection of thymic T-cells from the testosterone induced seasonal oxidative stress and apoptosis. Exposure to long day-length (LD) was noted to decrease local (thymic) melatonin content and induce oxidative stress and apoptosis in the thymus. Increased peripheral level of testosterone upregulated the androgen receptor expression and, consequently reduced proliferation response of the thymocytes. Short day conditions (SD) however, reversed the effect of LD on the thymic physiology. Low level of testosterone was concomitant with diminished nitro-oxidative stress and decreased expression of redox sensitive factors (NF-κB, p53 and Bax/Bcl-2 ratio) in the thymus. SD retarded activation of caspase-3 resulting in procaspase-3 accumulation. Further, in vitro treatment of thymocytes with AR antagonist flutamide impaired the sensitivity of thymocytes to androgen and reversed the deleterious effects of testosterone on the proliferative and apoptotic responses of thymocytes. Therefore, it can be suggested that thymus derived melatonin protects thymic T-cells from testosterone induced seasonal oxidative stress, apoptosis and also acts as a potent paracrine factor for maintenance of redox status to ensure thymocyte survival.

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.

The Development of an Angiogenic Protein "Signature" in Ovarian Cancer Ascites as a Tool for Biologic and Prognostic Profiling

Advanced ovarian cancer (AOC) is one of the leading lethal gynecological cancers in developed countries. Based on the important role of angiogenesis in ovarian cancer oncogenesis and expansion, we hypothesized that the development of an "angiogenic signature" might be helpful in prediction of prognosis and efficacy of anti-angiogenic therapies in this disease. Sixty-nine samples of ascitic fluid- 35 from platinum sensitive and 34 from platinum resistant patients managed with cytoreductive surgery and 1st-line carboplatin-based chemotherapy- were analyzed using the Proteome ProfilerTM Human Angiogenesis Array Kit, screening for the presence of 55 soluble angiogenesis-related factors. A protein profile based on the expression of a subset of 25 factors could accurately separate resistant from sensitive patients with a success rate of approximately 90%. The protein profile corresponding to the "sensitive" subset was associated with significantly longer PFS (8 [95% Confidence Interval {CI}: 8-9] vs. 20 months [95% CI: 15-28]; Hazard ratio {HR}: 8.3, p<0.001) and OS (20.5 months [95% CI: 13.5-30] vs. 74 months [95% CI: 36-not reached]; HR: 5.6 [95% CI: 2.8-11.2]; p<0.001). This prognostic performance was superior to that of stage, histology and residual disease after cytoreductive surgery and the levels of vascular endothelial growth factor (VEGF) in ascites. In conclusion, we developed an "angiogenic signature" for patients with AOC, which can be used, after appropriate validation, as a prognostic marker and a tool for selection for anti-angiogenic therapies.

Macitentan blocks endothelin-1 receptor activation required for chemoresistant ovarian cancer cell plasticity and metastasis

AIMS

In epithelial ovarian cancer (EOC), activation of endothelin-1 (ET-1)/endothelin A receptor (ETAR) and ET-1/ETBR signaling is linked to many tumor promoting effects, such as proliferation, angiogenesis, invasion, metastasis and chemoresistance. Understanding how to hamper the distinct mechanisms that facilitate epithelial plasticity and propagation is therefore central for improving the clinical outcome for EOC patients.

MAIN METHODS

The phosphorylation status of Akt and MAPK was evaluated by immunoblotting in A2780 and 2008 EOC cell lines and their cisplatinum-resistant variants. Vasculogenic mimicry was analyzed by vascular tubules formation assay. Tumor growth and metastases inhibition was performed in chemoresistant EOC xenografts.

KEY FINDINGS

We found that the dual ETAR/ETBR antagonist macitentan was able to inhibit the ET-1-induced activation of Akt and MAPK signaling pathways in chemoresistant EOC cells. Moreover, chemoresistant EOC cells displayed higher capability to engage vasculogenic mimicry compared to sensitive cells that was inhibited after treatment with macitentan. Finally, the specific ETAR antagonist zibotentan was less efficacious compared to macitentan to suppress tumor growth in chemoresistant EOC xenografts and the co-treatment of macitentan and cisplatinum reduced the metastatic progression.

SIGNIFICANCE

Our findings better clarify the ET-1-induced molecular mechanisms underlying the aggressive behavior of chemoresistant EOC cells. These results also support the use of macitentan in combination with chemotherapy as a rational therapeutic strategy for circumventing drug resistance in EOC.

Deciphering mechanisms of drug sensitivity and resistance to Selective Inhibitor of Nuclear Export (SINE) compounds

BACKGROUND

Exportin 1 (XPO1) is a well-characterized nuclear export protein whose expression is up-regulated in many types of cancers and functions to transport key tumor suppressor proteins (TSPs) from the nucleus. Karyopharm Therapeutics has developed a series of small-molecule Selective Inhibitor of Nuclear Export (SINE) compounds, which have been shown to block XPO1 function both in vitro and in vivo. The drug candidate, selinexor (KPT-330), is currently in Phase-II/IIb clinical trials for treatment of both hematologic and solid tumors. The present study sought to decipher the mechanisms that render cells either sensitive or resistant to treatment with SINE compounds, represented by KPT-185, an early analogue of KPT-330.

METHODS

Using the human fibrosarcoma HT1080 cell line, resistance to SINE was acquired over a period of 10 months of constant incubation with increasing concentration of KPT-185. Cell viability was assayed by MTT. Immunofluorescence was used to compare nuclear export of TSPs. Fluorescence activated cell sorting (FACS), quantitative polymerase chain reaction (qPCR), and immunoblots were used to measure effects on cell cycle, gene expression, and cell death. RNA from naïve and drug treated parental and resistant cells was analyzed by Affymetrix microarrays.

RESULTS

Treatment of HT1080 cells with gradually increasing concentrations of SINE resulted in >100 fold decrease in sensitivity to SINE cytotoxicity. Resistant cells displayed prolonged cell cycle, reduced nuclear accumulation of TSPs, and similar changes in protein expression compared to parental cells, however the magnitude of the protein expression changes were more significant in parental cells. Microarray analyses comparing parental to resistant cells indicate that a number of key signaling pathways were altered in resistant cells including expression changes in genes involved in adhesion, apoptosis, and inflammation. While the patterns of changes in transcription following drug treatment are similar in parental and resistant cells, the extent of response was more robust in the parental cells.

CONCLUSIONS

These results suggest that SINE resistance is conferred by alterations in signaling pathways downstream of XPO1 inhibition. Modulation of these pathways could potentially overcome the resistance to nuclear export inhibitors.

Cre recombinase-regulated Endothelin1 transgenic mouse lines: novel tools for analysis of embryonic and adult disorders

Endothelin-1 (EDN1) influences both craniofacial and cardiovascular development and a number of adult physiological conditions by binding to one or both of the known endothelin receptors, thus initiating multiple signaling cascades. Animal models containing both conventional and conditional loss of the Edn1 gene have been used to dissect EDN1 function in both embryos and adults. However, while transgenic Edn1 over-expression or targeted genomic insertion of Edn1 has been performed to understand how elevated levels of Edn1 result in or exacerbate disease states, an animal model in which Edn1 over-expression can be achieved in a spatiotemporal-specific manner has not been reported. Here we describe the creation of Edn1 conditional over-expression transgenic mouse lines in which the chicken β-actin promoter and an Edn1 cDNA are separated by a strong stop sequence flanked by loxP sites. In the presence of Cre, the stop cassette is removed, leading to Edn1 expression. Using the Wnt1-Cre strain, in which Cre expression is targeted to the Wnt1-expressing domain of the central nervous system (CNS) from which neural crest cells (NCCs) arise, we show that stable chicken β-actin-Edn1 (CBA-Edn1) transgenic lines with varying EDN1 protein levels develop defects in NCC-derived tissues of the face, though the severity differs between lines. We also show that Edn1 expression can be achieved in other embryonic tissues utilizing other Cre strains, with this expression also resulting in developmental defects. CBA-Edn1 transgenic mice will be useful in investigating diverse aspects of EDN1-mediated-development and disease, including understanding how NCCs achieve and maintain a positional and functional identity and how aberrant EDN1 levels can lead to multiple physiological changes and diseases.

Endothelin A receptor/β-arrestin signaling to the Wnt pathway renders ovarian cancer cells resistant to chemotherapy

The high mortality of epithelial ovarian cancer (EOC) is mainly caused by resistance to the available therapies. In EOC, the endothelin-1 (ET-1, EDN1)-endothelin A receptor (ETAR, EDNRA) signaling axis regulates the epithelial-mesenchymal transition (EMT) and a chemoresistant phenotype. However, there is a paucity of knowledge about how ET-1 mediates drug resistance. Here, we define a novel bypass mechanism through which ETAR/β-arrestin-1 (β-arr1, ARRB1) links Wnt signaling to acquire chemoresistant and EMT phenotype. We found that ETAR/β-arr1 activity promoted nuclear complex with β-catenin and p300, resulting in histone acetylation, chromatin reorganization, and enhanced transcription of genes, such as ET-1, enhancing the network that sustains chemoresistance. Silencing of β-arr1 or pharmacologic treatment with the dual ETAR/ETBR antagonist macitentan prevented core complex formation and restored drug sensitivity, impairing the signaling pathways involved in cell survival, EMT, and invasion. In vivo macitentan treatment reduced tumor growth, vascularization, intravasation, and metastatic progression. The combination of macitentan and cisplatinum resulted in the potentiation of the cytotoxic effect, indicating that macitentan can enhance sensitivity to chemotherapy. Investigations in clinical specimens of chemoresistant EOC tissues confirmed increased recruitment of β-arr1 and β-catenin to ET-1 gene promoter. In these tissues, high expression of ETAR significantly associated with poor clinical outcome and chemoresistance. Collectively, our findings reveal the existence of a novel mechanism by which ETAR/β-arr1 signaling is integrated with the Wnt/β-catenin pathway to sustain chemoresistance in EOC, and they offer a solid rationale for clinical evaluation of macitentan in combination with chemotherapy to overcome chemoresistance in this setting.

Role of the endothelin axis in astrocyte- and endothelial cell-mediated chemoprotection of cancer cells

BACKGROUND

Recent evidence suggests that astrocytes protect cancer cells from chemotherapy by stimulating upregulation of anti-apoptotic genes in those cells. We investigated the possibility that activation of the endothelin axis orchestrates survival gene expression and chemoprotection in MDA-MB-231 breast cancer cells and H226 lung cancer cells.

METHODS

Cancer cells, murine astrocytes, and murine fibroblasts were grown in isolation, and expression of endothelin (ET) peptides and ET receptors (ETAR and ETBR) compared with expression on cancer cells and astrocytes (or cancer cells and fibroblasts) that were co-incubated for 48 hours. Type-specific endothelin receptor antagonists were used to evaluate the contribution of ETAR and ETBR to astrocyte-induced activation of the protein kinase B (AKT)/mitogen-activated protein kinase (MAPK) signal transduction pathways, anti-apoptotic gene expression, and chemoprotection of cancer cells. We also investigated the chemoprotective potential of brain endothelial cells and microglial cells.

RESULTS

Gap junction signaling between MDA-MB-231 cancer cells and astrocytes stimulates upregulation of interleukin 6 (IL-6) and IL-8 expression in cancer cells, which increases ET-1 production from astrocytes and ET receptor expression on cancer cells. ET-1 signals for activation of AKT/MAPK and upregulation of survival proteins that protect cancer cells from taxol. Brain endothelial cell-mediated chemoprotection of cancer cells also involves endothelin signaling. Dual antagonism of ETAR and ETBR is required to abolish astrocyte- and endothelial cell-mediated chemoprotection.

CONCLUSIONS

Bidirectional signaling between astrocytes and cancer cells involves upregulation and activation of the endothelin axis, which protects cancer cells from cytotoxicity induced by chemotherapeutic drugs.

Endothelin-1 promotes survival and chemoresistance in chronic lymphocytic leukemia B cells through ETA receptor

The endothelin axis, comprising endothelins (ET-1, ET-2 and ET-3) and their receptors (ET(A)R and ETBR), has emerged as relevant player in tumor growth and metastasis. Here, we investigated the involvement of ET-1/ET(A)R axis in chronic lymphocytic leukemia (CLL). CLL cells expressed higher levels of ET-1 and ETA receptor as compared to normal B cells. ET-1 peptide stimulated phosphoinositide-3-kinase and mitogen-activated protein kinase signaling pathways, improved survival and promoted proliferation of leukemic cells throughout ET(A)R triggering. Moreover, the blockade of ET(A)R by the selective antagonist BQ-123 inhibited the survival advantage acquired by CLL cells in contact with endothelial layers. We also found that blocking ET(A)R via BQ-123 interferes with ERK phosphorylation and CLL pro-survival effect mediated by B-cell receptor (BCR) activation. The pro-apoptotic effect of phosphoinositide-3-kinase δ inhibitor idelalisib and mitogen-activated protein kinase inhibitor PD98059 was decreased by the addition of ET-1 peptide. Then, ET-1 also reduced the cytotoxic effect of fludarabine on CLL cells cultured alone or co-cultured on endothelial layers. ET(A)R blockade by BQ-123 inhibited the ET-1-mediated protection against drug-induced apoptosis. Lastly, higher plasma levels of big ET-1 were detected in patients (n = 151) with unfavourable prognostic factors and shorter time to first treatment. In conclusion, our data describe for the first time a role of ET-1/ET(A)R signaling in CLL pathobiology. ET-1 mediates survival, drug-resistance, and growth signals in CLL cells that can be blocked by ET(A)R inhibition.

Clinical pharmacology of an atrasentan and docetaxel regimen in men with hormone-refractory prostate cancer

PURPOSE

This study was conducted to evaluate potential pharmacokinetic interactions between docetaxel and atrasentan as part of a phase I/II clinical trial.

METHODS

Patients with prostate cancer were treated with intravenous docetaxel (60-75 mg/m(2)) every 3 weeks and oral atrasentan (10 mg) daily starting on day 3 of cycle 1 and then given continuously. The pharmacokinetics of both drugs were evaluated individually (cycle 1, day 1 for docetaxel; day 21 for atrasentan) and in combination (cycle 2, day 1 for both drugs). Pharmacogenomics of alpha-1-acid glycoprotein (AAG) were also explored.

RESULTS

Paired pharmacokinetic data sets for both drugs were evaluable in 21 patients. Atrasentan was rapidly absorbed and plasma concentrations varied over a fourfold range at steady state within a typical patient. The median apparent oral clearance of atrasentan was 17.4 L/h in cycle 1 and was not affected by docetaxel administration (p = 0.9). Median systemic clearance of docetaxel was 51.1 L/h on the first cycle and significantly slower (p = 0.01) compared with that obtained during co-administration of atrasentan, 61.6 L/h. Docetaxel systemic clearance in cycle 1 was 70.0 L/h in patients homozygous for a variant allele in AAG compared with 44.5 L/h in those with at least one wild-type allele (p = 0.03).

CONCLUSION

Genetic polymorphism in AAG may explain some inter-patient variability in docetaxel pharmacokinetics. The systemic clearance of docetaxel is increased by approximately 21 % when given concomitantly with atrasentan; however, atrasentan pharmacokinetics does not appear to be influenced by docetaxel administration.

Endothelin 1 in cancer: biological implications and therapeutic opportunities

Activation of autocrine and paracrine signalling by endothelin 1 (ET1) binding to its receptors elicits pleiotropic effects on tumour cells and on the host microenvironment. This activation modulates cell proliferation, apoptosis, migration, epithelial-to-mesenchymal transition, chemoresistance and neovascularization, thus providing a strong rationale for targeting ET1 receptors in cancer. In this Review, we discuss the advances in our understanding of the diverse biological roles of ET1 in cancer and describe the latest preclinical and clinical progress that has been made using small-molecule antagonists of ET1 receptors that inhibit ET1-driven signalling.

The independent, unfavorable prognostic factors endothelin A receptor and chemokine receptor 4 have a close relationship in promoting the motility of nasopharyngeal carcinoma cells via the activation of AKT and MAPK pathways

Background

Recent studies have indicated that the expression of endothelin A receptor (ETAR) and chemokine receptor 4 (CXCR4) could be used as an indicator of the metastatic potential of nasopharyngeal carcinoma (NPC). The aim of this study was to determine the prognostic value of ETAR and CXCR4 in NPC patients and to reveal the interplay of the endothelin-1 (ET-1)/ETAR and stromal-derived factor-1(SDF-1)/CXCR4 pathways in promoting NPC cell motility.

Methods

Survival analysis was used to analyze the prognostic value of ETAR and CXCR4 expression in 153 cases of NPC. Chemotaxis assays were used to evaluate alterations in the migration ability of non-metastatic 6-10B and metastatic 5-8F NPC cells. Real-time PCR, immunoblotting, and flow cytometric analyses were used to evaluate changes in the expression levels of CXCR4 mRNA and protein induced by ET-1.

Results

The expression levels of ETAR and CXCR4 were closely related to each other and both correlated with a poor prognosis. A multivariate analysis showed that the expression levels of both ETAR and CXCR4 were independent prognostic factors for overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS). The migration of 6-10B and 5-8F cells was elevated by ET-1 in combination with SDF-1α. The knockdown of ETAR protein expression by siRNA reduced CXCR4 protein expression in addition to ETAR protein expression, leading to a decrease in the metastatic potential of the 5-8F cells. ET-1 induced CXCR4 mRNA and protein expression in the 6-10B NPC cells in a time- and concentration-dependent fashion and was inhibited by an ETAR antagonist and PI3K/AKT/mTOR and MAPK/ERK1/2 pathway inhibitors.

Conclusions

ETAR and CXCR4 expression levels are potential prognostic biomarkers in NPC patients. ETAR activation partially promoted NPC cell migration via a mechanism that enhanced functional CXCR4 expression.

edn1 and hand2 Interact in early regulation of pharyngeal arch outgrowth during zebrafish development

Endothelin-1 (Edn1) signaling provides a critical input to development of the embryonic pharygneal arches and their skeletal derivatives, particularly the articulating joints and the ventral skeleton including the lower jaw. Previous work in zebrafish has mostly focused on the role of Edn1 in dorsal-ventral (DV) patterning, but Edn1 signaling must also regulate tissue size, for with severe loss of the pathway the ventral skeleton is not only mispatterned, but is also prominently hypoplastic – reduced in size. Here we use mutational analyses to show that in the early pharyngeal arches, ventral-specific edn1-mediated proliferation of neural crest derived cells is required for DV expansion and outgrowth, and that this positive regulation is counterbalanced by a negative one exerted through a pivotal, ventrally expressed Edn1-target gene, hand2. We also describe a new morphogenetic cell movement in the ventral first arch, sweeping cells anterior in the arch to the region where the lower jaw forms. This movement is negatively regulated by hand2 in an apparently edn1-independent fashion. These findings point to complexity of regulation by edn1 and hand2 at the earliest stages of pharyngeal arch development, in which control of growth and morphogenesis can be genetically separated.

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.

FOXO1 mediates the autocrine effect of endothelin-1 on endothelial cell survival

Chronic hyperglycemia exerts a deleterious effect on endothelium, contributing to endothelial dysfunction and microvascular complications in poorly controlled diabetes. To understand the underlying mechanism, we studied the effect of endothelin-1 (ET-1) on endothelial production of Forkhead box O1 (FOXO1), a forkhead transcription factor that plays an important role in cell survival. ET-1 is a 21-amino acid peptide that is secreted primarily from endothelium. Using adenovirus-mediated gene transfer approach, we delivered FOXO1 cDNA into cultured human aorta endothelial cells. FOXO1 was shown to stimulate B cell leukemia/lymphoma 2-associated death promoter (BAD) production and promote cellular apoptosis. This effect was counteracted by ET-1. In response to ET-1, FOXO1 was phosphorylated and translocated from the nucleus to cytoplasm, resulting in inhibition of BAD production and mitigation of FOXO1-mediated apoptosis. Hyperglycemia stimulated FOXO1 O-glycosylation and promoted its nuclear localization in human aorta endothelial cells. This effect accounted for unbridled FOXO1 activity in the nucleus, contributing to augmented BAD production and endothelial apoptosis under hyperglycemic conditions. FOXO1 expression became deregulated in the aorta of both streptozotocin-induced diabetic mice and diabetic db/db mice. This hyperglycemia-elicited FOXO1 deregulation and its ensuing effect on endothelial cell survival was corrected by ET-1. Likewise, FoxO1 deregulation in the aorta of diabetic mice was reversible after the reduction of hyperglycemia by insulin therapy. These data reveal a mechanism by which FOXO1 mediated the autocrine effect of ET-1 on endothelial cell survival. FOXO1 deregulation, resulting from an impaired ability of ET-1 to control FOXO1 activity in endothelium, may contribute to hyperglycemia-induced endothelial lesion in diabetes.

Molecular targeted therapy in ovarian cancer: what is on the horizon?

Over the past two decades, empirical optimization of cytotoxic chemotherapy combinations and surgical debulking procedures have improved outcomes and survival in epithelial ovarian cancer. Yet, this disease remains the fifth leading cause of cancer-related deaths in the US, as cure rates seem to have reached a plateau at approximately 20% with conventional chemotherapy. Novel high-throughput genomic and proteomic analyses have improved the molecular understanding of ovarian carcinogenesis, thereby providing a vast array of new potential drug targets with complex signalling interactions. In order to yield the most significant impact on disease outcome, it is necessary to carefully select, and subsequently target, the driving molecular pathway(s) within a tumour or tumour subtype, which are most likely to correspond to high-frequency mutations and genomic aberrations. The identification of biomarkers predictive of response to targeted therapy is essential to avoid poor responses to potentially useful drugs in unselected trial populations. With some promising, albeit early, phase III data on the angiogenesis inhibitor bevacizumab, exciting new opportunities lie ahead with the ultimate goal of personalizing therapies to individual tumour profiles.

Expression patterns of endothelin-1 and its receptors in colorectal cancer

BACKGROUND AND OBJECTIVES

Endothelin-1 (ET-1), a potent vasoconstricting peptide, plays an important role in carcinogenesis. Previous in vitro studies have shown that colorectal cancer cells produce ET-1.

METHODS

ET-1 and its receptors ET-A (ET(A) R) and ET-B (ET(B) R) were analyzed in colorectal cancer cell lines and tumors by Western blot and immunohistochemistry. Also, ET-1 levels were measured by ELISA in blood samples collected before and after tumor resection.

RESULTS

ET-1 was immunohistochemically expressed by tumor cells at a variable level in 39 cases tested. The adjacent normal mucosa was negative for ET-1 expression. Strong ET(A) R expression observed in the deeper infiltrating areas at the periphery of neoplastic tissue correlated significantly with tumor stage. ET(B) R levels were very low or undetectable. Western blot analysis in paired (normal, tumor) fresh-frozen samples of colorectal cancers and in four colon carcinoma cell lines confirmed these findings. In addition, lower levels of ET-1 in the peripheral circulation after the tumor resection were found by ELISA as compared to those observed before surgery.

CONCLUSIONS

ET-1 and ET(A) R, but not ET(B) R, are expressed at a higher level in primary and cultured colon carcinoma cells as compared to normal colon mucosa cells. Further functional studies are needed to explore the role of ET-1/ET(A) R axis in colon carcinogenesis.

Polymorphisms in the endothelin-1 and endothelin a receptor genes and survival in patients with locoregionally advanced nasopharyngeal carcinoma

PURPOSE

We aimed to investigate the prognostic role of endothelin-1 (EDN1) and endothelin A receptor (EDNRA) gene polymorphisms in patients with locoregionally advanced nasopharyngeal carcinoma (NPC).

EXPERIMENTAL DESIGN

Two hundred three consecutive patients with locoregionally advanced NPC were enrolled. Seven potentially functional polymorphisms in the EDN1 and EDNRA genes were determined by ligase detection reaction-PCR method from prospectively collected blood samples. The influence of the genetic polymorphisms on patient overall survival (OS) was analyzed using Cox proportional hazards model, Kaplan-Meier method, and the log-rank test.

RESULTS

The 5-year OS in patients with EDNRA/H323H TT, TC, and CC genotypes were 81.3%, 62.1%, and 75.0%, respectively (P = 0.004). Patients carrying the heterozygous (TC) or homozygous variant (CC) genotype in EDNRA/H323H were combined for analysis, which revealed that the 5-year OS in patients with TC/CC genotypes was significantly lower than those with the wild-type TT genotype (63.2% vs. 81.3%; P = 0.002). Multivariate analysis showed that EDNRA/H323H polymorphism (HR: 1.95; 95% CI: 1.18-3.23; P = 0.009) and N classification (HR: 1.35; 95% CI: 1.03-1.79; P = 0.03) were independent significant prognostic factors for OS in patients with locoregionally advanced NPC. In contrast, the EDN1 polymorphisms revealed no prognostic value.

CONCLUSIONS

The EDNRA/H323H polymorphism was a novel and independent prognostic marker for patients with locoregionally advanced NPC. The analysis of EDNRA/H323H polymorphism may help identify patient subgroups at high risk for poor disease outcome.

Combination therapy of zibotentan with cisplatinum and paclitaxel is an effective regimen for epithelial ovarian cancer

In human ovarian carcinoma, the endothelin-1 (ET-1) / endothelin A receptor (ETAR) axis is overexpressed, correlating with tumor grade. Moreover, ETAR activation by ET-1 affects cell proliferation, survival, angiogenesis, and invasion. ETAR blockade with zibotentan (ZD4054), a specific ETAR antagonist, significantly inhibits ovarian cancer growth in vitro and in vivo, underscoring the relevance of this pathway as a target for cancer therapy. Since clinical trial results have defined the combination of platinum and taxane as the standard of care in the management of ovarian cancer, here we explored the therapeutic efficacy of the integration of zibotentan with cytotoxic drugs having different modes of action. We found that the combination of zibotentan with cisplatinum as well as zibotentan with paclitaxel was more effective at inhibiting ovarian cancer HEY cell proliferation induced by endogenous ET-1 than were the single agents alone. However, a significantly enhanced efficacy was observed when we combined zibotentan, cisplatinum, and paclitaxel. Accordingly, in HEY xenografts the coadministration of zibotentan with cisplatinum enhanced the efficacy of the cytotoxic drug alone in controlling tumor growth, associated with reduction in proliferation index and microvessel density. Remarkably, the combination of zibotentan with both cisplatinum and paclitaxel was very effective in inhibiting tumor growth, neovascularization, and cell proliferation, representing a preclinical endpoint to guide combination therapy in clinical trials.

Beta-arrestin-1 mediates the endothelin-1-induced activation of Akt and integrin-linked kinase

The contribution of the endothelin-1 (ET-1)/ET A receptor (ETAR) axis in tumor growth and progression is investigated in many tumor types, including ovarian carcinoma. In ovarian cancer cells, ET-1 acts as an autocrine growth factor selectively through the ETAR triggering the concomitant activation of multiple pathways. In these cells, the involvement of beta-arrestin-1 as signal transducer in ET-1-dependent signalling pathways has been recently highlighted. Because several G protein-coupled receptors have been shown to activate signalling pathways in a beta-arrestin-dependent manner, in this study we explored whether beta-arrestin-1 is involved in a distinct signalling mechanism linking the ETAR to phosphoinositide 3-kinase (PI3K)/integrin-linked kinase (ILK)/Akt in HEY ovarian cancer cells. The inhibitory effects of ZD4054 (zibotentan), a specific ETAR antagonist, in ET-1-dependent phosphorylation of ILK, Akt, and glycogen synthase kinase (GSK-3beta) demonstrated the involvement of the ETAR in these effects. By using a kinase assay, we demonstrate that beta-arrestin-1 silencing inhibits the ET-1-induced ILK activity in a time-dependent manner and downstream Akt and GSK-3beta phosphorylation. These results reveal that beta-arrestin-1 is implicated as an ETAR-transducer in the activation of ILK and Akt and in the inactivation of GSK-3beta in response to ET-1 and further support the role of beta-arrestin-1 as a multifunctional adaptor facilitating interprotein interactions critically involved in ETAR-mediated signalling that regulate invasive and metastatic behaviour of ovarian cancer.

Acquisition of chemoresistance and EMT phenotype is linked with activation of the endothelin A receptor pathway in ovarian carcinoma cells

PURPOSE

Emerging evidence suggests molecular and phenotypic association between chemoresistance and epithelial-mesenchymal transition (EMT) in cancer. Endothelin-1 (ET-1)/endothelin A receptor (ET(A)R) axis is implicated in the pathobiology of epithelial ovarian cancer (EOC) by driving tumor-promoting effects, including EMT. Here, we analyzed how ET(A)R regulates chemoresistance and EMT in EOC.

EXPERIMENTAL DESIGN

The effects of ET-1 axis on cell proliferation, drug-induced apoptosis, invasiveness, and EMT were analyzed in cultured EOC cells sensitive and resistant to cisplatinum and taxol. Tumor growth in response to ET(A)R antagonist was examined in EOC xenografts. ET(A)R expression was examined in 60 human EOC tumors by immunohistochemistry and correlated with chemoresistance and EMT.

RESULTS

In resistant EOC cells ET-1 and ET(A)R are upregulated, paralleled by enhanced mitogen activated protein kinase (MAPK) and Akt phosphorylation and cell proliferation. Moreover, in these cells the expression of E-cadherin transcriptional repressors, including Snail, Slug, and Twist, as well as of mesenchymal markers, such as vimentin and N-cadherin, were upregulated and linked with enhanced invasive behavior. Interestingly, ET(A)R blockade with zibotentan, a specific ET(A)R antagonist, or its silencing, downregulated Snail activity, restored drug sensitivity to cytotoxic-induced apoptosis, and inhibited the invasiveness of resistant cells. In vivo, zibotentan inhibited tumor growth of sensitive and resistant EOC xenografts, and sensitized to chemotherapy. Analysis of EOC human tissues revealed that ET(A)R is overexpressed in resistant tumors and is associated with EMT phenotype.

CONCLUSIONS

Our data provide the first evidence that blockade of ET(A)R-driven EMT can overcome chemoresistance and inhibit tumor progression, improving the outcome of EOC patients' treatment.

Endothelin axis induces metalloproteinase activation and invasiveness in human lymphatic endothelial cellsThis article is one of a selection of papers published in the two-part special issue entitled 20 Years of Endothelin Research

The molecular mechanisms involved in lymphangiogenesis were unknown until recently. We previously demonstrated that the endothelin-1 (ET-1) axis stimulates lymphatic endothelial cells (LEC) and lymphatic vessels to grow and invade. Here we further investigated the effect of ET-1 on lymphatic vessels and evaluated whether ET-1 actions result in the functional activation of lymphangiogenesis. Using highly purified human LEC, characterized for the expression of ET-1 axis members by quantitative real-time PCR, we found that the endothelin B receptor (ETB), upon activation by ET-1, induced matrix-metalloproteinase activation, demonstrating that ET-1 influenced the activity of the proteolytic enzymes required for LEC invasion. Functional assays performed by using intradermal lymphangiography demonstrated that ET-1 promoted the formation of lymphatic vessels and that these vessels were capable of lymphatic flow. ETB blockade with the specific antagonist BQ788 inhibited matrix-metalloproteinase activation and dye transport within the lymphatic vessels, demonstrating that ETB is involved in the regulation of the growth of and in the formation of functional vessels upon activation by ET-1. Our results suggest that ET-1 is a lymphangiogenic mediator and that targeting pharmacologically ETB may be therapeutically exploited in a variety of diseases, including cancer.

Emerging drugs for ovarian cancer

IMPORTANCE OF THE FIELD

Ovarian cancer has the highest mortality of all female reproductive tract cancers, which reflects both the absence of proven ovarian cancer screening tests and the development of drug-resistant cancer cell. Apart from varying the dosages, schedules, mode of delivery and combinations of existing drugs, efforts must continue to identify signaling pathways in tumor cells sufficiently different from normal cells that can be a target for maximizing tumor kill and minimizing toxicity.

AREAS COVERED IN THIS REVIEW

Some of the most important cellular pathways are analyzed and discussed and the most interesting clinical trials, both closed and ongoing, described.

WHAT THE READER WILL GAIN

The reader will gain a panoramic vision of all the most active drugs in clinical investigations in ovarian cancer. The reader will also better understand what the unresolved problems of molecular research are and how complicated the process 'from the bench to the bedside' is.

TAKE HOME MESSAGE

It is only with a strong commitment, cooperation and collaboration from the international ovarian cancer community that significant improvement in patient outcomes can be attained beyond the marginal gains achieved so far.

The importance of endothelin axis in initiation, progression, and therapy of ovarian cancer

The endothelin-1 (ET-1)/ET A receptor (ET(A)R) axis is involved in the pathobiology of different tumors, including ovarian carcinoma. Acting selectively on ET(A)R, ET-1 regulates, through multiple signaling pathways, mitogenesis, cell survival, angiogenesis, lymphangiogenesis, invasion, and metastatic dissemination. Moreover, ET-1/ET(A)R axis appears to be critical in epithelial-to-mesenchymal transition (EMT), providing a mechanism of escape to a new, less adverse niche, in which resistance to apoptosis ensures cell survival in conditions of stress in the primary tumor, and acquisition of "stemness" ensures generation of the critical mass required for tumor progression. Emerging experimental and preclinical data demonstrate that interfering with ET(A)R pathways provides an opportunity for the development of new mechanism-based antitumor strategies by using ET(A)R antagonists alone and in combination with cytotoxic drugs or molecular inhibitors. A specific ET(A)R antagonist in combination with standard chemotherapy is currently evaluated in clinical and translational studies to provide us with new options to treat ovarian cancer and to predict response to therapy. Deeper understanding of molecular mechanism activated by ET(A)R in ovarian cancer will be of paramount importance in the study of ET(A)R-targeted therapy that, regulating EMT and other tumor-associated processes, represents an attractive but challenging approach to improve clinical management of ovarian cancer.

Atrasentan (ABT-627) enhances perfusion and reduces hypoxia in a human tumor xenograft model

The endothelin-1 antagonist, Atrasentan (ABT-627) was used to modify perfusion in the human tumor xenograft model, HT29, growing in nude mice. Atrasentan produced a significant increase in perfusion, as measured in vivo by Gd-DTPA DCE-MRI. Changes in tumor hypoxia were assessed by comparing the binding of two hypoxia tracers, pimonidazole and EF5 given before and after Atrasentan administration. In vehicle-treated controls, the distribution of EF5 and pimonidazole was very similar. However, Atrasentan treatment was associated with decreased uptake of the second hypoxia tracer (EF5), relative to the first (pimonidazole). Although Atrasentan had no independent effect on the growth of HT29 tumors, Atrasentan combined with 20 Gy radiation led to a modest but significant increase in tumor growth delay compared to radiation alone.

COOPERATIVE GROUP TRIALS - SOUTHWEST ONCOLOGY GROUP (SWOG) INNOVATIONS IN ADVANCED PROSTATE CANCER

The major goals of the SWOG-GU committee in the area of advanced prostate cancer are to improve the survival and quality of life of patients with advanced prostate cancer. SWOG trials have examined the role of combined androgen blockade, intermittent androgen deprivation, and the early application of chemotherapy in castration-naïve disease. In addition, they have contributed to advancing the current chemotherapy standard of docetaxel plus prednisone, and ongoing trials seek to improve upon that standard. Finally, surrogate endpoints have been identified and markers of treatment response or resistance with novel technology are under active investigation. This review highlights findings from recent SWOG clinical trials for advanced prostate cancer, emphasizing the clinical impact and future applications of the data.

Endothelin-1 stimulates lymphatic endothelial cells and lymphatic vessels to grow and invade

The lymphatic vasculature is essential for tissue fluid homeostasis and cancer metastasis, although the molecular mechanisms involved remain poorly characterized. Endothelin-1 (ET-1) axis plays a crucial role in angiogenesis and tumorigenesis. Here, we first report that ET-1 acts as a lymphangiogenic mediator. We performed in vitro and in vivo studies and show that lymphatic endothelial cells produce ET-1, ET-3, and express the endothelin B receptor (ET(B)R). In these cells, ET-1 promotes proliferation, invasiveness, vascular-like structures formation, and phosphorylation of AKT and p42/44 mitogen-activated protein kinase through ET(B)R. In normoxic conditions, ET-1 is also able to up-regulate the expression of vascular endothelial growth factor (VEGF)-C, VEGF receptor-3, and VEGF-A, and to stimulate hypoxia-inducible factor (HIF)-1alpha expression similarly to hypoxia. Moreover, HIF-1alpha silencing by siRNA desensitizes VEGF-C and VEGF-A production in response to ET-1 or hypoxia, implicating HIF-1alpha/VEGF as downstream signaling molecules of ET-1 axis. Double immunofluorescence analysis of human lymph nodes reveals that lymphatic vessels express ET(B)R together with the lymphatic marker podoplanin. Furthermore, a Matrigel plug assay shows that ET-1 promotes the outgrowth of lymphatic vessels in vivo. ET(B)R blockade with the specific antagonist, BQ788, inhibits in vitro and in vivo ET-1-induced effects, demonstrating that ET-1 through ET(B)R directly regulates lymphatic vessel formation and by interacting with the HIF-1alpha-dependent machinery can amplify the VEGF-mediated lymphatic vascularization. Our results suggest that ET-1 axis is indeed a new player in lymphangiogenesis and that targeting pharmacologically ET(B)R and related signaling cascade may be therapeutically exploited in a variety of diseases including cancer.

Beta-arrestin links endothelin A receptor to beta-catenin signaling to induce ovarian cancer cell invasion and metastasis

The activation of endothelin-A receptor (ET(A)R) by endothelin-1 (ET-1) has a critical role in ovarian tumorigenesis and progression. To define the molecular mechanism in ET-1-induced tumor invasion and metastasis, we focused on beta-arrestins as scaffold and signaling proteins of G protein-coupled receptors. Here, we demonstrate that, in ovarian cancer cells, beta-arrestin is recruited to ET(A)R to form two trimeric complexes: one through the interaction with Src leading to epithelial growth factor receptor (EGFR) transactivation and beta-catenin Tyr phosphorylation, and the second through the physical association with axin, contributing to release and inactivation of glycogen synthase kinase (GSK)-3beta and beta-catenin stabilization. The engagement of beta-arrestin in these two signaling complexes concurs to activate beta-catenin signaling pathways. We then demonstrate that silencing of both beta-arrestin-1 and beta-arrestin-2 inhibits ET(A)R-driven signaling, causing suppression of Src, mitogen-activated protein kinase (MAPK), AKT activation, as well as EGFR transactivation and a complete inhibition of ET-1-induced beta-catenin/TCF transcriptional activity and cell invasion. ET(A)R blockade with the specific ET(A)R antagonist ZD4054 abrogates the engagement of beta-arrestin in the interplay between ET(A)R and the beta-catenin pathway in the invasive program. Finally, ET(A)R is expressed in 85% of human ovarian cancers and is preferentially co-expressed with beta-arrestin-1 in the advanced tumors. In a xenograft model of ovarian metastasis, HEY cancer cells expressing beta-arrestin-1 mutant metastasize at a reduced rate, highlighting the importance of this molecule in promoting metastases. ZD4054 treatment significantly inhibits metastases, suggesting that specific ET(A)R antagonists, by disabling multiple signaling activated by ET(A)R/beta-arrestin, may represent new therapeutic opportunities for ovarian cancer.

Endothelin-1 and transforming growth factor-beta1 independently induce fibroblast resistance to apoptosis via AKT activation

Myofibroblast apoptosis is critical for the normal resolution of wound repair responses, and impaired myofibroblast apoptosis is associated with tissue fibrosis. Lung expression of endothelin (ET)-1, a soluble peptide implicated in fibrogenesis, is increased in murine models of pulmonary fibrosis and in the lungs of humans with pulmonary fibrosis. Mechanistically, ET-1 has been shown to induce fibroblast proliferation, differentiation, contraction, and collagen synthesis. In this study, we examined the role ET-1 in the regulation of lung fibroblast survival and apoptosis. ET-1 rapidly activates the prosurvival phosphatidylinositol 3'-OH kinase (PI3K)/AKT signaling pathway in normal and fibrotic human lung fibroblasts. ET-1-induced activation of PI3K/AKT is dependent on p38 mitogen-activated protein kinase (MAPK), but not extracellular signal-regulated kinase (ERK) 1/2, JNK, or transforming growth factor (TGF)-beta1. Activation of the PI3K/AKT pathway by ET-1 inhibits fibroblast apoptosis, and this inhibition is reversed by blockade of p38 MAPK or PI3K. TGF-beta1 has been shown to attenuate myofibroblast apoptosis through the p38 MAPK-dependent secretion of a soluble factor, which activates PI3K/AKT. In this study, we show that, although TGF-beta1 induces fibroblast synthesis and secretion of ET-1, TGF-beta1 activation of PI3K/AKT is not dependent on ET-1. We conclude that ET-1 and TGF-beta1 independently promote fibroblast resistance to apoptosis through signaling pathways involving p38 MAPK and PI3K/AKT. These findings suggest the potential for novel therapies targeting the convergence of prosurvival signaling pathways activated by these two profibrotic mediators.

Targeting the endothelin system: novel therapeutic options in gynecological, urological and breast cancers

The endothelin system comprises the three peptide hormones endothelin (ET)-1, -2, -3, their G protein-coupled receptors, endothelin-A-receptor (ET(A)R) and endothelin-B-receptor (ET(B)R), and the enzymes of endothelin biosynthesis and degradation. In the past two decades, an impressive amount of data has been accumulated investigating the role of the endothelin system in a variety of malignancies. In many cancers, ET-1/ET(A)R interaction induces proliferation, angiogenesis, antiapoptosis and resistance to chemotherapy. Data indicate a pivotal role of the endothelin system in tumorigenesis, local progression and metastasis. Subsequently, novel drugs have been designed inhibiting ET-1 biosynthesis or ET(A)R interaction. A wide range of preclinical data is available on the role of ET(A)R antagonists in gynecological, urological and breast cancers providing evidence for their antiangiogenic, proapoptotic and growth inhibitory effects. Of particular interest is the anti-invasive and antimetastatic efficacy of ET(A)R antagonists and synergism when co-administered with established cancer therapies. Data indicate a future role of ET(A)R antagonists in oncologic therapies.

Elevation of circulating big endothelin-1: an independent prognostic factor for tumor recurrence and survival in patients with esophageal squamous cell carcinoma

BACKGROUND

Endothelin(ET) axis plays a key role in many tumor progression and metastasis via various mechanisms such as angiogenesis, mediating extracellular matrix degradation and inhibition of apoptosis. However, there is limited information regarding the clinical significance of plasma big ET-1 levels in esophageal cancer patients. Circulating plasma big ET-1 levels were measured in patients with esophageal squamous cell carcinoma(ESCC) to evaluate the value of ET-1 as a biomarker for predicting tumor recurrence and patients survival.

METHODS

Preoperative plasma big ET-1 concentrations were measured by an enzyme linked immunosorbent assay(ELISA) in 108 ESCC patients before surgery, and then again at 1,2,3,10 and 30 days after curative radical resection for ESCC. The association between preoperative plasma big ET-1 levels and clinicopathological features, tumor recurrence and patient survival, and their changes following surgery were evaluated.

RESULTS

The preoperative plasma big ET-1 levels in ESCC patients were significantly higher than those in controls. And there was a significant association between plasma big ET-1 levels and disease stage, as well as invasion depth of the tumor and lymph node status. Furthermore, plasma big ET-1 levels decreased significantly after radical resection of the primary tumor and patients with postoperative recurrence had significantly higher plasma big ET-1 levels than that of patients without recurrence. Finally, the survival rate of patients with higher plasma big ET-1 concentrations (>4.3 pg/ml) was significantly lower than that of patients with lower level (< or = 4.3 pg/ml). Multivariate regression analysis showed that plasma big ET-1 level is an independent prognostic factor for survival in patients with ESCC.

CONCLUSION

Plasma big ET-1 level in ESCC patients may reflect malignancy and predict tumor recurrence and patient survival. Therefore, the preoperative plasma big ET-1 levels may be a clinically useful biomarker for choice of multimodality therapy in ESCC patients.

The endothelin axis in cancer: the promise and the challenges of molecularly targeted therapy

The endothelin (ET) axis, which includes ET-1, ET-2, ET-3, and 2 G protein-coupled receptor subtypes, ET AR and ET BR, promotes growth and progression of a variety of tumors, such as prostatic, ovarian, renal, pulmonary, colorectal, cervical, breast, lung, bladder, endometrial carcinoma, Kaposi's sarcoma, brain tumors, and melanoma. Acting on selective receptors, ET-1 regulates mitogenesis, cell survival, angiogenesis, bone remodeling, stimulation of nociceptors, tumor-infiltrating immune cells, epithelial-to-mesenchymal transition, invasion, and metastatic dissemination. At the molecular level, endothelin receptor antagonists, besides providing ideal tools for dissecting the ET axis, have demonstrated their potential in developing novel therapeutic strategies. Emerging experimental and clinical data demonstrate that interfering with endothelin receptors provides an opportunity for the development of rational combinatorial approaches using endothelin receptor antagonists in combination with chemotherapy or molecularly targeted therapy.