Gene regulation of vasopressin and vasopressin receptors in cancer

Stress regulatory hormones and cancer: the contribution of epinephrine and cancer therapeutic value of beta blockers

The word "cancer" evokes myriad emotions, ranging from fear and despair to hope and determination. Cancer is aptly defined as a complex and multifaceted group of diseases that has unapologetically led to the loss of countless lives and affected innumerable families across the globe. The battle with cancer is not only a physical battle, but also an emotional, as well as a psychological skirmish for patients and for their loved ones. Cancer has been a part of our history, stories, and lives for centuries and has challenged the ingenuity of health and medical science, and the resilience of the human spirit. From the early days of surgery and radiation therapy to cutting-edge developments in chemotherapeutic agents, immunotherapy, and targeted treatments, the medical field continues to make significant headway in the fight against cancer. However, even after all these advancements, cancer is still among the leading cause of death globally. This urges us to understand the central hallmarks of neoplastic cells to identify novel molecular targets for the development of promising therapeutic approaches. Growing research suggests that stress mediators, including epinephrine, play a critical role in the development and progression of cancer by inducing neoplastic features through activating adrenergic receptors, particularly β-adrenoreceptors. Further, our experimental data has also shown that epinephrine mediates the growth of T-cell lymphoma by inducing proliferation, glycolysis, and apoptosis evasion via altering the expression levels of key regulators of these vital cellular processes. The beauty of receptor-based therapy lies in its precision and higher therapeutic value. Interestingly, the enhanced expression of β-adrenergic receptors (ADRBs), namely ADRB2 (β2-adrenoreceptor) and ADRB3 (β3-adrenoreceptor) has been noted in many cancers, such as breast, colon, gastric, pancreatic, and prostate and has been reported to play a pivotal role in facilitating cancer growth mainly by promoting proliferation, evasion of apoptosis, angiogenesis, invasion and metastasis, and chemoresistance. The present review article is an attempt to summarize the available findings which indicate a distinct relationship between stress hormones and cancer, with a special emphasis on epinephrine, considered as a key stress regulatory molecule. This article also discusses the possibility of using beta-blockers for cancer therapy.

The Vasopressin Receptor Antagonist Tolvaptan Counteracts Tumor Growth in a Murine Xenograft Model of Small Cell Lung Cancer

We have previously demonstrated that the vasopressin type 2 receptor (AVPR2) antagonist tolvaptan reduces cell proliferation and invasion and triggers apoptosis in different human cancer cell lines. To study this effect in vivo, a xenograft model of small cell lung cancer was developed in Fox1nu/nu nude mice through the subcutaneous inoculation of H69 cells, which express AVPR2. One group of mice (n = 5) was treated with tolvaptan for 60 days, whereas one group (n = 5) served as the control. A reduced growth was observed in the tolvaptan group in which the mean tumor volume was significantly smaller on day 60 compared to the control group. In the latter group, a significantly lower survival was observed. The analysis of excised tumors revealed that tolvaptan effectively inhibited the cAMP/PKA and PI3K/AKT signaling pathways. The expression of the proliferative marker proliferating cell nuclear antigen (PCNA) was significantly lower in tumors excised from tolvaptan-treated mice, whereas the expression levels of the apoptotic marker caspase-3 were higher than those in control animals. Furthermore, tumor vascularization was significantly lower in the tolvaptan group. Overall, these findings suggest that tolvaptan counteracts tumor progression in vivo and, if confirmed, might indicate a possible role of this molecule as an adjuvant in anticancer strategies.

Kidney collecting duct-derived vasopressin is not essential for appropriate concentration or dilution of urine

We have previously shown that kidney collecting ducts make vasopressin. However, the physiological role of collecting duct-derived vasopressin is uncertain. We hypothesized that collecting duct-derived vasopressin is required for the appropriate concentration of urine. We developed a vasopressin conditional knockout (KO) mouse model wherein Cre recombinase expression induces deletion of arginine vasopressin (Avp) exon 1 in the distal nephron. We then used age-matched 8- to 12-wk-old Avp fl/fl;Ksp-Cre(-) [wild type (WT)] and Avp fl/fl;Ksp-Cre(+) mice for all experiments. We collected urine, serum, and kidney lysates at baseline. We then challenged both WT and knockout (KO) mice with 24-h water restriction, water loading, and administration of the vasopressin type 2 receptor agonist desmopressin (1 µg/kg ip) followed by the vasopressin type 2 receptor antagonist OPC-31260 (10 mg/kg ip). We performed immunofluorescence and immunoblot analysis at baseline and confirmed vasopressin KO in the collecting duct. We found that urinary osmolality (UOsm), plasma Na+, K+, Cl-, blood urea nitrogen, and copeptin were similar in WT vs. KO mice at baseline. Immunoblots of the vasopressin-regulated proteins Na+-K+-2Cl- cotransporter, NaCl cotransporter, and water channel aquaporin-2 showed no difference in expression or phosphorylation at baseline. Following 24-h water restriction, WT and KO mice had no differences in UOsm, plasma Na+, K+, Cl-, blood urea nitrogen, or copeptin. In addition, there were no differences in the rate of urinary concentration or dilution as in WT and KO mice UOsm was nearly identical after desmopressin and OPC-31260 administration. We conclude that collecting duct-derived vasopressin is not essential to appropriately concentrate or dilute urine.NEW & NOTEWORTHY Hypothalamic vasopressin is required for appropriate urinary concentration. However, whether collecting duct-derived vasopressin is involved remains unknown. We developed a novel transgenic mouse model to induce tissue-specific deletion of vasopressin and showed that collecting duct-derived vasopressin is not required to concentrate or dilute urine.

Vasopressin induces apoptosis but does not enhance the antiproliferative effect of dynamin 2 or PI3K/Akt inhibition in luminal A breast cancer cells

Breast cancer cells abnormally express vasopressin (AVP) and its receptors. The effect of AVP is largely orchestrated through its downstream signaling and by receptor-mediated endocytosis (RME), in which Dynamin 2 (Dyn2) plays an integral role in vesicle closure. In this work, luminal A breast cancer cells were treated with AVP, and then Dynasore (DYN) was employed to inhibit Dyn2 to explore the combined effect of AVP and Dyn2 inhibition on the survival of breast cancer cells. The results revealed that DYN alone demonstrated a concentration-dependent cytotoxic effect in AVP untreated cells. Apoptosis developed in 29.7 and 30.3% of cells treated with AVP or AVP+DYN, respectively, compared to 32.5% in cells treated with Wortmannin (Wort, a selective PI3K pathway inhibitor). More apoptosis was observed when cells were treated with DYN+Wort in presence or absence of exogenous AVP. Besides, 2 or 4- fold increases in the expression of Bax and Caspase-3, were observed in cells exposed to AVP in absence or presence of DYN, respectively. This was associated with higher levels of the autophagy marker (LC3II protein). Meanwhile, the activation of Akt protein, sequentially decreased in the same pattern. Cell's invasion decreased when they were exposed to AVP alone or combined with DYN or/and Wort. Conclusively, although many reports suggested the proliferative effect of AVP, the results predict the antiproliferative and antimetastatic effects of 100 nM AVP in luminal A breast cancer cells. However, the hormone did not enhance the cytotoxic effect of Dyn 2 or PI3K pathway inhibition. Summary of the Dynamin 2 independent AVP antiproliferative effects. Breast cancer cells expresses AVP as a Prohormone (A). At high dose of AVP, the hormone is liganded with AVP receptor (B) to initiate RME, where the endosomed complex (C) is degraded through the endosome-lysosome system, as a part of signal management. These events consume soluble Dyn2 in neck closure and vesicle fission (D). This makes the cells more substitutable to the direct apoptotic effect of DYN (E). Alternatively, at lower AVP doses the liganded AVP may initiate cAMP-mediated downstream signaling (F) and cellular proliferation. In parallel, Wort inhibits PIP2-PIP3 conversion (G) and the subsequent inhibition of PI3K/Akt/mTOR pathway leading to cell death.

Kidney collecting duct cells make vasopressin in response to NaCl-induced hypertonicity

Vasopressin has traditionally been thought to be produced by the neurohypophyseal system and then released into the circulation where it regulates water homeostasis. The questions of whether vasopressin could be produced outside of the brain and if the kidney could be a source of vasopressin are raised by the syndrome of inappropriate antidiuretic hormone secretion (vasopressin). We found that mouse and human kidneys expressed vasopressin mRNA. Using an antibody that detects preprovasopressin, we found that immunoreactive preprovasopressin protein was found in mouse and human kidneys. Moreover, we found that murine collecting duct cells made biologically active vasopressin, which increased in response to NaCl-mediated hypertonicity, and that water restriction increased the abundance of kidney-derived vasopressin mRNA and protein expression in mouse kidneys. Thus, we provide evidence of biologically active production of kidney-derived vasopressin in kidney tubular epithelial cells.

Gαs and Gαq/11 protein coupling bias of two AVPR2 mutants (R68W and V162A) that cause nephrogenic diabetes insipidus

Loss-of-function mutations of the arginine vasopressin receptor 2 gene (AVPR2) cause Nephrogenic diabetes insipidus (NDI). AVPR2 is a kind of G protein coupled receptor (GPCR) and mainly couples with Gαs protein leading to cAMP accumulation in the cell as a secondary messenger. Recent studies showed that some AVPR2 mutations could cause biased Gαq/11 protein coupling rather than Gαs. Investigation into the characterization of biased receptors may give insights into the relationship between the conformational change of the receptor because of the mutation and related downstream signaling. In this study, R68W and V162A were analyzed to whether they show a bias to Gαs or Gαq/11 proteins. Their functionality in terms of cAMP production via Gαs protein coupling was decreased compared to the wild-type receptor. On the other hand, they showed the ability to couple with Gαq/11 protein and make Ca²⁺ mobilization at different levels in the cell. R68W showed bias to coupling with Gαq/11 protein rather than V162A and wild-type receptor. Studies about the Gα protein coupling bias of mutant AVPR2s may broaden our understanding of the relationship between the changed conformation of the receptor and consequently activated signaling pathways, and also may shed light on the development of more effective new therapeutics.

African Ancestry-Associated Gene Expression Profiles in Triple-Negative Breast Cancer Underlie Altered Tumor Biology and Clinical Outcome in Women of African Descent

Women of sub-Saharan African descent have disproportionately higher incidence of triple-negative breast cancer (TNBC) and TNBC-specific mortality across all populations. Population studies show racial differences in TNBC biology, including higher prevalence of basal-like and quadruple-negative subtypes in African Americans (AA). However, previous investigations relied on self-reported race (SRR) of primarily U.S. populations. Due to heterogeneous genetic admixture and biological consequences of social determinants, the true association of African ancestry with TNBC biology is unclear. To address this, we conducted RNA sequencing on an international cohort of AAs, as well as West and East Africans with TNBC. Using comprehensive genetic ancestry estimation in this African-enriched cohort, we found expression of 613 genes associated with African ancestry and 2,000+ associated with regional African ancestry. A subset of African-associated genes also showed differences in normal breast tissue. Pathway enrichment and deconvolution of tumor cellular composition revealed that tumor-associated immunologic profiles are distinct in patients of African descent.

SIGNIFICANCE

Our comprehensive ancestry quantification process revealed that ancestry-associated gene expression profiles in TNBC include population-level distinctions in immunologic landscapes. These differences may explain some differences in race-group clinical outcomes. This study shows the first definitive link between African ancestry and the TNBC immunologic landscape, from an African-enriched international multiethnic cohort. See related commentary by Hamilton et al., p. 2496. This article is highlighted in the In This Issue feature, p. 2483.

The V2 receptor antagonist tolvaptan counteracts proliferation and invasivity in human cancer cells

PURPOSE

Hyponatremia, the most frequent electrolyte alteration in clinical practice, has been associated with a worse prognosis in cancer patients. On the other hand, a better outcome has been related to serum sodium normalization. In vitro studies have shown that low extracellular sodium promotes cancer cells proliferation and invasiveness. Tolvaptan, a selective vasopressin receptor type 2 (V₂) antagonist, has been effectively used in the last decade for the treatment of hyponatremia secondary to the Syndrome of Inappropriate Antidiuresis. A few in vitro data suggested a direct role of tolvaptan in counteracting cancer progression, so far. The aim of this study was to evaluate the effect and the mechanism of action of tolvaptan in cell lines from different tumours [i.e. colon cancer (HCT-8), hepatocarcinoma (HepG2), neuroblastoma (SK-N-AS)].

METHODS AND RESULTS

First, we showed that these cell lines express the V₂ receptor. Tolvaptan significantly reduced cell proliferation with an IC₅₀ in the micromolar range. Accordingly, reduced levels of cAMP, of the catalytic α subunit of PKA, and a reduced pAKT/AKT ratio were observed. Tolvaptan effectively inhibited cell cycle progression, whereas it induced apoptotis. Furthermore, it reduced cell invasiveness. In particular, anchorage-independent growth and the activity of collagenases type IV were blunted in the three cell lines. Accordingly, tolvaptan counteracted the RhoA/ROCK1-2 pathway, which has a pivotal role in regulating cell movement.

CONCLUSIONS

Overall, these findings indicate that tolvaptan effectively inhibits tumour progression in vitro. Further studies should clarify whether the V₂ receptor might be considered a possible target in anti-cancer strategies in the future.

dDAVP Downregulates the AQP3-Mediated Glycerol Transport via V1aR in Human Colon HCT8 Cells

Vasopressin (AVP) plays a key function in controlling body water and salt balance through the activation of the vasopressin receptors V1aR and V2R. Abnormal secretion of AVP can cause the syndrome of inappropriate antidiuresis that leads to hyponatremia, which is an electrolyte disorder often observed in the elderly hospitalized and oncologic patients. Beyond kidneys, the colonic epithelium modulates water and salt homeostasis. The water channel AQP3, expressed in villus epithelial cells is implicated in water absorption across human colonic surface cells. Here, the action of dDAVP, a stable vasopressin analog, was evaluated on the AQP3 expression and function using human colon HCT8 cells as an experimental model. Confocal and Western Blotting analysis revealed that HCT8 cells express both V1aR and V2R. Long-term (72 h) treatment with dDAVP reduced glycerol uptake and cell viability. These effects were prevented by SR49059, a synthetic antagonist of V1aR, but not by tolvaptan, a specific V2R antagonist. Of note, the SR49059 action was impaired by DFP00173, a selective inhibitor of AQP3. Interestingly, compared to the normal colonic mucosa, in the colon of patients with adenocarcinoma, the expression of V1aR was significantly decreased. These findings were confirmed by gene expression analysis with RNA-Seq data. Overall, data suggest that dDAVP, through the V1aR dependent pathway, reduces AQP3 mediated glycerol uptake, a process that is reversed in adenocarcinoma, suggesting that the AVP-dependent AQP3 pathway may represent a novel target in colon diseases associated with abnormal cell growth.

Vasopressin and Its Analogues: From Natural Hormones to Multitasking Peptides

Human neurohormone vasopressin (AVP) is synthesized in overlapping regions in the hypothalamus. It is mainly known for its vasoconstricting abilities, and it is responsible for the regulation of plasma osmolality by maintaining fluid homeostasis. Over years, many attempts have been made to modify this hormone and find AVP analogues with different pharmacological profiles that could overcome its limitations. Non-peptide AVP analogues with low molecular weight presented good affinity to AVP receptors. Natural peptide counterparts, found in animals, are successfully applied as therapeutics; for instance, lypressin used in treatment of diabetes insipidus. Synthetic peptide analogues compensate for the shortcomings of AVP. Desmopressin is more resistant to proteolysis and presents mainly antidiuretic effects, while terlipressin is a long-acting AVP analogue and a drug recommended in the treatment of varicose bleeding in patients with liver cirrhosis. Recently published results on diverse applications of AVP analogues in medicinal practice, including potential lypressin, terlipressin and ornipressin in the treatment of SARS-CoV-2, are discussed.

Insulin-Regulated Aminopeptidase in Women with Breast Cancer: A Role beyond the Regulation of Oxytocin and Vasopressin

Simple Summary

Insulin-regulated aminopeptidase (IRAP) is a well-known enzyme involved mainly in the regulation of the peptide hormones, oxytocin and vasopressin. However, this enzyme activity has hardly been analyzed in breast cancer patients. Additionally, the influence of both the hormonal status (pre or postmenopause) and the administration of neoadjuvant chemotherapy have rarely been studied. We show that there is a weak association between IRAP activity and the circulating levels of peptide hormones with variations depending on the hormonal status and the neoadjuvant treatment, and propose a role beyond oxytocin and vasopressin regulation that is related to the local mammary renin-angiotensin system and glucose transportation to the cells.

Abstract

Insulin-regulated aminopeptidase (IRAP) is the only enzyme known to cleave oxytocin and vasopressin; however, it is also the high-affinity binding site for angiotensin IV (AngIV) receptor type 4 (AT4) ligands and it is related to insulin-dependent glucose transporters through the translocation of the glucose transporter type 4 (GLUT4). Previous studies have demonstrated an association between IRAP activity and the number and size of mammary tumors in an animal model of breast cancer (BC). Also, a highly significant increase in IRAP activity has been found in BC tissue from women patients. Here, we found no changes in circulating IRAP in premenopausal (preMP) women, but it increased significantly in postmenopausal (postMP) women not treated with neoadjuvant chemotherapy (NACH). However, in women treated with NACH, IRAP activity increased in both preMP and postMP women. Two years of follow-up indicated lower levels of IRAP activity in untreated preMP women, but a return to control levels in untreated postMP women, while IRAP activity returned to control levels in women treated with NACH. Circulating oxytocin decreased in both preMP and postMP women during the follow-up period. Differences in Oxytocin appeared between preMP and postMP women treated with NACH, but not in women who were not treated with NACH. On the contrary, circulating vasopressin increased in untreated and treated preMP and postMP women, with most of the differences related to the hormonal status as well as the neoadjuvant treatment during the two year follow-up We propose that IRAP is involved in mechanisms related not only to oxytocin and/or vasopressin regulation, but also to the local mammary RAS through AngIV and its role in glucose transportation through the IRAP/GLUT4 system.

Yohimbine as a Starting Point to Access Diverse Natural Product-Like Agents with Re-programmed Activities against Cancer-Relevant GPCR Targets

G protein-coupled receptors (GPCRs) constitute the largest protein superfamily in the human genome. GPCRs play key roles in mediating a wide variety of physiological events including proliferation and cancer metastasis. Given the major roles that GPCRs play in mediating cancer growth, they present promising targets for small molecule therapeutics. One of the principal goals of our lab is to identify complex natural products (NPs) suitable for ring distortion, or the dramatic altering of the inherently complex architectures of NPs, to rapidly generate an array of compounds with diverse molecular skeletal systems. The overarching goal of our ring distortion approach is to re-program the biological activity of select natural products and identify new compounds of importance to the treatment of disease, such as cancer. Described herein are the results from biological screens of diverse small molecules derived from the indole alkaloid yohimbine against a panel of GPCRs involved in various diseases. Several analogues displayed highly differential antagonistic activities across the GPCRs tested. We highlight the re-programmed profile of one analogue, Y7g, which exhibited selective antagonistic activities against AVPR2 (IC₅₀ = 459 nM) and OXTR (IC₅₀ = 1.16 µM). The activity profile of Y7g could correlate its HIF-dependent anti-cancer activity to its GPCR antagonism since these receptors are known to be upregulated in hypoxic cellular environments. Our findings demonstrate that the ring distortion of yohimbine can lead to the identification of new compounds capable of interacting with distinct cancer-relevant targets.

New drugs are not enough‑drug repositioning in oncology: An update

Drug repositioning refers to the concept of discovering novel clinical benefits of drugs that are already known for use treating other diseases. The advantages of this are that several important drug characteristics are already established (including efficacy, pharmacokinetics, pharmacodynamics and toxicity), making the process of research for a putative drug quicker and less costly. Drug repositioning in oncology has received extensive focus. The present review summarizes the most prominent examples of drug repositioning for the treatment of cancer, taking into consideration their primary use, proposed anticancer mechanisms and current development status.

Targeting the vasopressin type-2 receptor for renal cell carcinoma therapy

Arginine vasopressin (AVP) and its type-2 receptor (V2R) play an essential role in the regulation of salt and water homeostasis by the kidneys. V2R activation also stimulates proliferation of renal cell carcinoma (RCC) cell lines in vitro. The current studies investigated V2R expression and activity in human RCC tumors, and its role in RCC tumor growth. Examination of the cancer genome atlas (TCGA) database, and analysis of human RCC tumor tissue microarrays, cDNA arrays and tumor biopsy samples demonstrated V2R expression and activity in clear cell RCC (ccRCC). In vitro, V2R antagonists OPC31260 and Tolvaptan, or V2R gene silencing reduced wound closure and cell viability of 786-O and Caki-1 human ccRCC cell lines. Similarly in mouse xenograft models, Tolvaptan and OPC31260 decreased RCC tumor growth by reducing cell proliferation and angiogenesis, while increasing apoptosis. In contrast, the V2R agonist dDAVP significantly increased tumor growth. High intracellular cAMP levels and ERK1/2 activation were observed in human ccRCC tumors. In mouse tumors and Caki-1 cells, V2R agonists reduced cAMP and ERK1/2 activation, while dDAVP treatment had the reverse effect. V2R gene silencing in Caki-1 cells also reduced cAMP and ERK1/2 activation. These results provide novel evidence for a pathogenic role of V2R signaling in ccRCC, and suggest that inhibitors of the AVP-V2R pathway, including the FDA-approved drug Tolvaptan, could be utilized as novel ccRCC therapeutics.

Novel molecular mechanisms in the inhibition of adrenal aldosterone synthesis: Action of tolvaptan via vasopressin V2 receptor-independent pathway

BACKGROUND AND PURPOSE

We investigated the inhibitory effect and associated molecular mechanisms of tolvaptan on angiotensin II (AngII)-induced aldosterone production in vitro and in vivo.

EXPERIMENTAL APPROACH

In vitro, H295R human adrenocarcinoma cells were incubated with 1 μmol·L^-1 arginine vasopressin (AVP) or dDAVP, or tolvaptan (0.1, 1, and 3 μmol·L^-1 ) in the presence and absence of 100 nmol·L^-1 of AngII. In vivo, Sprague-Dawley rats were treated with tolvaptan 0.05% in the diet for 6 days in the presence and absence of 200 pmol·min^-1 AngII.

KEY RESULTS

Tolvaptan suppressed AngII-induced aldosterone production in a dose-dependent manner in H295R cells, whereas neither AVP nor dDAVP in the presence or absence of AngII altered aldosterone production, suggesting the vasopressin V₂ receptor was not involved in the inhibitory effect of tolvaptan on aldosterone synthesis. In addition, tolvaptan inhibited the AngII-induced increase in aldosterone synthase (CYP11B2) protein levels without suppressing CYP11B2 mRNA expression. Notably, tolvaptan increased the levels of unfolded protein response (UPR) marker DDIT3 and eIF2α phosphorylation (a UPR-induced event), which could block the translation of CYP11B2 mRNA into protein and thereby inhibit aldosterone production. In vivo, tolvaptan significantly inhibited AngII-induced increases in serum and adrenal aldosterone levels and CYP11B2 protein levels. This anti-aldosterone effect was associated with a reduction in the elevated systolic and diastolic BP.

CONCLUSIONS AND IMPLICATIONS

Tolvaptan inhibited AngII-stimulated aldosterone production via a V₂ receptor-independent pathway, which can counteract or even surpass its potential activating effect of diuresis-induced aldosterone secretion in certain aldosterone-mediated pathological conditions.

FoPA: identifying perturbed signaling pathways in clinical conditions using formal methods

BACKGROUND

Accurate identification of perturbed signaling pathways based on differentially expressed genes between sample groups is one of the key factors in the understanding of diseases and druggable targets. Most pathway analysis methods prioritize impacted signaling pathways by incorporating pathway topology using simple graph-based models. Despite their relative success, these models are limited in describing all types of dependencies and interactions that exist in biological pathways.

RESULTS

In this work, we propose a new approach based on the formal modeling of signaling pathways. Signaling pathways are formally modeled, and then model checking tools are applied to find the likelihood of perturbation for each pathway in a given condition. By adopting formal methods, various complex interactions among biological parts are modeled, which can contribute to reducing the false-positive rate of the proposed approach. We have developed a tool named Formal model checking based pathway analysis (FoPA) based on this approach. FoPA is compared with three well-known pathway analysis methods: PADOG, CePa, and SPIA on the benchmark of 36 GEO datasets from various diseases by applying the target pathway technique. This validation technique eliminates the need for possibly biased human assessments of results. In the cases that, there is no apriori knowledge of all relevant pathways, simulated false inputs (permuted class labels and decoy pathways) are chosen as a set of negative controls to test the false positive rate of the methods. Finally, to further evaluate the efficiency of FoPA, it is applied to a list of autism-related genes.

CONCLUSIONS

The results obtained by the target pathway technique demonstrate that FoPA is able to prioritize target pathways as well as PADOG but better than CePa and SPIA. Also, the false-positive rate of finding significant pathways using FoPA is lower than other compared methods. Also, FoPA can detect more consistent relevant pathways than other methods. The results of FoPA on autism-related genes highlight the role of "Renin-angiotensin system" pathway. This pathway has been supposed to have a pivotal role in some neurodegenerative diseases, while little attention has been paid to its impact on autism development so far.

Search of vasopressin analogs with antiproliferative activity on small-cell lung cancer: drug design based on two different approaches

AIM

Development of compounds with therapeutic application requires the interaction of different disciplines. Several tumors express vasopressin (AVP; arginine vasopressin) receptors with contrasting effects depending on receptor subtype. Desmopressin (dDAVP) is an AVP-selective analog with antiproliferative properties. In this work, an evolutionary approach and a rational strategy were applied in order to design novel AVP analogs.

RESULTS

We designed two novel analogs; dDInotocin (dDINT, insect analog), and [V⁴Q⁵]dDAVP, and demonstrated the importance of the dDAVP conformational loop for its antiproliferative activity. [V⁴Q⁵] dDAVP showed major cytostatic effect on lung cancer cells than dDAVP and its cytostatic effect was abolished by V2R blockade.

CONCLUSION

Combination of these strategies could provide the basis for future studies for the development of improved compounds with potential therapeutic applications.

Peptide Agonists of Vasopressin V2 Receptor Reduce Expression of Neuroendocrine Markers and Tumor Growth in Human Lung and Prostate Tumor Cells

Neuroendocrine tumors (NETs) comprise a heterogeneous group of malignancies that express neuropeptides as synaptophysin, chromogranin A (CgA), and specific neuronal enolase (NSE), among others. Vasopressin (AVP) is a neuropeptide with an endocrine, paracrine, and autocrine effect in normal and pathological tissues. AVP receptors are present in human lung, breast, pancreatic, colorectal, and gastrointestinal tumors. While AVP V1 receptors are associated with stimulation of cellular proliferation, AVP V2 receptor (V2r) is related to antiproliferative effects. Desmopressin (dDAVP) is a synthetic analog of AVP that acts as a selective agonist for the V2r, which shows antitumor properties in breast and colorectal cancer models. Recently, we developed a derivative of dDAVP named [V⁴Q⁵]dDAVP, which presents higher antitumor effects in a breast cancer model compared to the parental compound. The goal of present work was to explore the antitumor properties of the V2r agonist dDAVP and its novel analog [V⁴Q⁵]dDAVP on aggressive human lung (NCI-H82) and prostate cancer (PC-3) cell lines with neuroendocrine (NE) characteristics. We study the presence of specific NE markers (CgA and NSE) and V2r expression in NCI-H82 and PC-3. Both cell lines express high levels of NE markers NSE and CgA but then incubation with dDAVP diminished expression levels of both markers. DDAVP and [V⁴Q⁵]dDAVP significantly reduced proliferation, doubling time, and migration in both tumor cell cultures. [V⁴Q⁵]dDAVP analog showed a higher cytostatic effect than dDAVP, on cellular proliferation in the NCI-H82 cell line. Silencing of V2r using small interfering RNA significantly attenuated the inhibitory effects of [V⁴Q⁵]dDAVP on NCI-H82 cell proliferation. We, preliminarily, explored the in vivo effect of dDAVP and [V⁴Q⁵]dDAVP on NCI-H82 small cell lung cancer xenografts. Treated tumors (0.3 μg kg^-1, thrice a week) grew slower in comparison to vehicle-treated animals. In this work, we demonstrated that the specific agonists of V2r, dDAVP, and [V⁴Q⁵]dDAVP displays antitumor capacity on different human models of lung and prostate cancers with NE features, showing their potential therapeutic benefits in the treatment of these aggressive tumors.

Health effects of desalinated water: Role of electrolyte disturbance in cancer development

This review contends that "healthy" water in terms of electrolyte balance is as important as "pure" water in promoting public health. It considers the growing use of desalination (demineralization) technologies in drinking water treatment which often results in tap water with very low concentrations of sodium, potassium, magnesium and calcium. Ingestion of such water can lead to electrolyte abnormalities marked by hyponatremia, hypokalemia, hypomagnesemia and hypocalcemia which are among the most common and recognizable features in cancer patients. The causal relationships between exposure to demineralized water and malignancies are poorly understood. This review highlights some of the epidemiological and in vivo evidence that link dysregulated electrolyte metabolism with carcinogenesis and the development of cancer hallmarks. It discusses how ingestion of demineralized water can have a procarcinogenic effect through mediating some of the critical pathways and processes in the cancer microenvironment such as angiogenesis, genomic instability, resistance to programmed cell death, sustained proliferative signaling, cell immortalization and tumorigenic inflammation. Evidence that hypoosmotic stress-response processes can upregulate a number of potential oncogenes is well supported by a number studies. In view of the rising production and consumption of demineralized water in most parts of the world, there is a strong need for further research on the biological importance and protean roles of electrolyte abnormalities in promoting, antagonizing or otherwise enabling the development of cancer. The countries of the Gulf Cooperative Council (GCC) where most people consume desalinated water would be a logical place to start this research.

Arginine vasopressin (AVP): a review of its historical perspectives, current research and multifunctional role in the hypothalamo-hypophysial system

INTRODUCTION

This publication reviews the function of arginine vasopressin and focuses on the morphologic and functional correlation between the hormone and its effect on stress, the hypophysial-adrenocortical axis, neuroimmune responses, renal function and corticotroph pituitary tumors.

MATERIALS AND METHODS

A literature review was performed using various search engines for information regarding the morphology and the multifunctional role of arginine vasopressin.

RESULTS

Although a large number of studies were published discussing these interactions, there are several important areas that are still obscure.

CONCLUSION

The questions of how does arginine vasopressin affect the morphology and function of these various areas, and how does the secretion of ACTH and adrenocortical hormones influence the morphology of arginine vasopressin-producing cells and their hormone secretion requires further investigation.

Nephro-oncology: a link in evolution

A multidisciplinary approach represents the best method to interact with patients. Neoplastic and renal diseases are closely related to each other because of an increased risk of cancer among individuals with end-stage renal disease and because of the high prevalence of renal failure in cancer patients. Physicians should be able to know how to prevent and treat the possible complications which may appear during the course of neoplastic disease that may lead to kidney damage such as the Acute Tumor Lysis Syndrome, disorders of hydroelectrolitic balance, metabolic alterations in the calcium-phosphorus, anemia, interstitial and glomerular impairment due to chemotherapy. It is very important to know patients' renal function and directly monitor it, before and during treatment, using formulas for estimating glomerular filtration rate (GFR) and above all, specific biomarkers are more early and sensitive than the increase of creatinine, like neutrophil gelatinase-associated lipocalin. Additionally, physician should consider that alteration of GFR or substitutive renal treatments severely influence dosage of tumor markers and it could lead to wrong diagnosis of cancer. The aim of this article is to provide a review of problems related to cancer relevant in the development of renal failure and try to define the best therapeutic strategies to cope with possible kidney imbalances induced by cancer or its treatment.

The physiological and pathophysiological functions of renal and extrarenal vasopressin V2 receptors

The arginine vasopressin (AVP) type 2 receptor (V2R) is unique among AVP receptor subtypes in signaling through cAMP. Its key function is in the kidneys, facilitating the urine concentrating mechanism through the AVP/V2 type receptor/aquaporin 2 system in the medullary and cortical collecting ducts. Recent clinical and research observations strongly support the existence of an extrarenal V2R. The clinical importance of the extrarenal V2R spans widely from stimulation of coagulation factor in the endothelium to as yet untested potential therapeutic targets. These include V2R-regulated membranous fluid turnover in the inner ear, V2R-regulated mitogensis and apoptosis in certain tumor tissues, and numerous other cell types where the physiological role of V2Rs still requires further research. Here, we review current evidence on the physiological and pathophysiological functions of renal and extrarenal V2Rs. These functions of V2R are important, not only in rare diseases with loss or gain of function of V2R but also in relation to the recent use of nonpeptide V2R antagonists to treat hyponatremia and possibly retard the growth of cysts and development of renal failure in autosomal dominant polycystic kidney disease. The main functions of V2R in principal cells of the collecting duct are water, salt, and urea transport by modifying the trafficking of aquaporin 2, epithelial Na(+) channels, and urea transporters and vasodilation and stimulation of coagulation factor properties, mainly seen with pharmacological doses of 1-desamino-8-D-AVP. The AVPR2 gene is located on the X chromosome, in a region with high probability of escape from inactivation; this may lead to phenotypic sex differences, with females expressing higher levels of transcript than males.

Growth Impairment of Small-Cell Cancer by Targeting Pro-Vasopressin with MAG-1 Antibody

Previously we demonstrated that human small-cell lung cancer (SCLC) seems to universally express the vasopressin gene, and this leads to the presence of a cell surface marker representing the entire pro-hormone precursor. In this study, we show this marker can be targeted with MAG-1, a mouse monoclonal antibody against a C-terminal moiety on pro-vasopressin. In vitro targeting of cell lines derived from primary and recurrent disease demonstrates attachment of antibody to the cell surface followed by internalization. In vivo targeting with ⁹⁹Tc-labeled Fab fragments of MAG-1 shows selective attachment to xenografts. In vivo treatment of tumors from classical cell line, NCI H345, with either ~1.65 mCi (~1.65 mg)/kg body weight (BW) of ⁹⁰Yttrium-labeled MAG-1, or ~1.65 mg/kg BW native MAG-1, delivered every second day for 6 days produced similar reductions in the growth rate to ~50% (p < 0.03). When dosing with native MAG-1 was escalated to daily amounts of ~3.3 mg/kg BW over 16 days, tumor growth rates fell to ~33% of saline controls (p < 0.005). Examination of tumors treated with this higher dosing demonstrated the presence in several of extensive apoptosis. Normal tissues seemed to be unaffected. A larger dosage of MAG-1 (~6.6 mg/kg BW) given daily for 14 days was used to treat xenografts of the variant cell line NCI H82 representing recurrent disease. This treatment decreased the rate of increase in tumor size by half, and doubling time ~3-fold. Increases in cleaved PARP supported increased apoptosis with antibody treatment. We believe these data provide evidence that the growth rate of SCLC tumors can be extensively reduced by treatment with MAG-1 antibody, and that a humanized form of this antibody could, in future, be potentially used for targeting therapy onto recurrent SCLC in patients.

Metastasis: recent discoveries and novel perioperative treatment strategies with particular interest in the hemostatic compound desmopressin

Metastatic disease is responsible for most of cancer lethality. A main obstacle for therapy of advanced cancers is that the outcome of metastasis depends on a complex interplay between malignant and host cells. The perioperative period represents an underutilized window of opportunity for cancer treatment where tumor-host interactions can be modulated, reducing the risk of local recurrences and distant metastases. Blood-saving agents are attractive compounds to be administered during tumor surgery. Desmopressin (DDAVP) is a safe and convenient hemostatic peptide with proved antimetastastic properties in experimental models and veterinary clinical trials. The compound seems to induce a dual angiostatic and antimetastatic effect, breaking the cooperative function of cancer cells and endothelial cells during residual tumor progression. DDAVP is therefore an interesting lead compound to develop novel synthetic peptide analogs with enhanced antitumor properties.

Antiproliferative effect of 1-deamino-8-D-arginine vasopressin analogs on human breast cancer cells

BACKGROUND

Desmopressin (dDAVP), a synthetic nonapeptide derivative of arginine vasopressin, is a safe antidiuretic and hemostatic compound that acts as a selective agonist for the vasopressin V2 membrane receptor (V2R). It is known that dDAVP can inhibit progression of residual metastatic cells in preclinical models. Among other mechanisms, the compound induces an agonist effect on V2R present in tumor cells.

RESULTS/DISCUSSION

Looking for novel analogs with improved anti-tumor activity, positions 4 and 5, at the conformational peptide loop, were substituted. The analog [V(4)Q(5)]dDAVP ([4-valine 5-glutamine] desmopressin) exhibited a significantly higher antiproliferative effect than dDAVP in cultures of MCF-7, a V2R-expressing human breast carcinoma cell line. The chiral isomer of this analog and tetrapeptide fragments corresponding to the loop region were also assessed.

CONCLUSION

Preclinical evaluation of the anti-tumor activity of [V(4)Q(5)]dDAVP in animal models is warranted.

Native MAG-1 antibody almost destroys human breast cancer xenografts

A native form of mouse monoclonal IgG1 antibody called MAG-1, which recognizes an epitope on provasopressin, has been found to shrink and produce extensive necrosis of human breast tumor xenografts in nu/nu mice. We examined the ability of (90)Yttrium-labeled and native MAG-1 to affect the growth in nu/nu mice of cancer xenografts that were estrogen-responsive (from MCF-7 cells) and triple-negative (from MDA-MB231 cells). The growth rates of treated cells were compared to those receiving saline vehicle and those receiving (90)Yttrium-labeled and native forms of the ubiquitous antibody, MOPC21. Short-term treatments (4 doses over 6 days) not only with (90)Yttrium-MAG-1 but also native MAG-1 produced large reductions in size of rapidly growing tumors of both types, while both (90)Yttrium- MOPC21 and native MOPC21 had no effect. Native and (90)Yttrium-MAG-1 effects were similar, and arrested tumors recommenced growing soon after treatments stopped. Increasing native MAG-1 treatment to single dosing for 16 consecutive days shrank tumors of both types with no regrowth apparent over a 20-day post-treatment period of observation. Pathological examination of such tumors revealed they had undergone very extensive (>66%) necrosis.

Effect of adjuvant perioperative desmopressin in locally advanced canine mammary carcinoma and its relation to histologic grade

Desmopressin (DDAVP) is a vasopressin peptide analog with hemostatic properties that has been successfully used during surgery in patients with bleeding disorders. Recently published experimental and clinical data indicate that perioperative administration of DDAVP can minimize spread and survival of residual mammary cancer cells. The central aim of this study was to explore the effect of perioperative DDAVP and its relation to histologic grade in bitches with locally advanced mammary carcinoma. Of the 32 dogs initially recruited, 28 intact bitches with mammary carcinoma tumors stage III or IV were ultimately included. These dogs were randomized to receive DDAVP at intravenous doses of 1 μg/kg (n=18) or saline solution as placebo (n=10). En bloc mastectomy of the affected gland(s) was performed. Tumor malignancy was graded by the method of Elston and Ellis into well-differentiated (grade 1), moderately differentiated (grade 2), or poorly differentiated (grade 3). DDAVP therapy significantly prolonged the disease-free survival (P<0.001) and overall survival (P<0.01) in bitches with grade 2 or 3 carcinomas compared with bitches in the control group. No significant difference in disease-free period or overall survival was found between treatment groups in bitches with grade 1 tumors. The present data suggest that DDAVP may be an excellent candidate as a surgical adjuvant in the management of aggressive cancers in small animals. More research in this field is warranted.

Breast cancer expresses functional NMDA receptors

We demonstrate here that functional NMDAR1 and NMDAR2 receptors are expressed by Mcf-7 and SKBR3 breast cancer cell lines, and possibly by most or all high-grade breast tumors, and that these receptors are important for the growth of human breast cancer xenografts in mice. RT-PCR demonstrated mRNA for both NMDAR1 and NMDAR2 receptors are expressed in both Mcf-7 and SKBR3 cell lines, and these messages likely have sequences identical to those reported for human mRNAs. Proteins of the expected respective sizes 120 and 170 kD are generated from these mRNAs by the tumor cells. Cell growth was found to be significantly (P < 0.0001) impaired down to 10% of normal growth by the irreversible NMDAR1 antagonists MK-801 and memantine with IC 50s ranging from 600 to >800 microM and from 200 to 300 microM for the two lines. Paradoxically, memantine with a lower binding affinity had the greater influence of the two inhibitors on cell viability. Immunohistochemical examination of high-grade invasive ductal and lobular breast cancer with our polyclonal antibodies against a peptide (-Met-Ser-Ile-Tyr-Ser-Asp-Lys-Ser-Ile-His-) in the extracellular domain of the NMDAR1 receptor gave specific positive staining for the receptor in all 10 cases examined. Positive staining was chiefly concentrated at the membranes of these tumor tissues. No staining with these antibodies was found for normal breast and kidney tissues. When Mcf-7 cells were grown as tumor xenografts in nu/nu mice, the growth of these tumors was completely arrested by daily treatments with MK-801 over 5 days. All of these data point to active NMDAR receptors being expressed by most breast cancers, and having an important influence on their survival.

Design of peptide-targeted liposomes containing nucleic acids

Anticancer systemic gene silencing therapy has been so far limited by the inexistence of adequate carrier systems that ultimately provide an efficient intracellular delivery into target tumor cells. In this respect, one promising strategy involves the covalent attachment of internalizing-targeting ligands at the extremity of PEG chains grafted onto liposomes. Therefore, the present work aims at designing targeted liposomes containing nucleic acids, with small size, high encapsulation efficiency and able to be actively internalized by SCLC cells, using a hexapeptide (antagonist G) as a targeting ligand. For this purpose, the effect of the liposomal preparation method, loading material (ODN versus siRNA) and peptide-coupling procedure (direct coupling versus post-insertion) on each of the above-mentioned parameters was assessed. Post-insertion of DSPE-PEG-antagonist G conjugates into preformed liposomes herein named as stabilized lipid particles, resulted in targeted vesicles with a mean size of about 130 nm, encapsulation efficiency close to 100%, and a loading capacity of approximately 5 nmol siRNA/mumol of total lipid. In addition, the developed targeted vesicles showed increased internalization in SCLC cells, as well as in other tumor cells and HMEC-1 microvascular endothelial cells. The improved cellular association, however, did not correlate with enhanced downregulation of the target protein (Bcl-2) in SCLC cells. These results indicate that additional improvements need to be performed in the future, namely by ameliorating the access of the nucleic acids to the cytoplasm of the tumor cells following receptor-mediated endocytosis.

Targeting growth factors in lung cancer

Lung cancer causes more deaths than any other malignancy in the developed world. Advances in surgical techniques and chemotherapy/radiotherapy regimes have produced only minimal improvements in long-term survival. New therapeutic interventions are urgently required. Research has indicated that growth factor signaling may be an important novel target in lung cancer therapy. Preclinical studies have demonstrated the role of extracellular growth factors in lung cancer cell proliferation, metastasis, and resistance to cytotoxic therapy, and have elucidated the key molecular components of growth factor-signaling cascades. This has enabled the development of selective growth factor inhibitors, which have been evaluated in clinical trials and are now an accepted component of advanced lung cancer treatment. Further research is underway to improve the efficacy of this growth factor-targeted therapy. This article will outline the important aspects of this translational research indicating the growth factor-signaling pathways identified in lung cancer, clinical trials of anti-growth factor therapy, and potential future research directions.

Perioperative desmopressin prolongs survival in surgically treated bitches with mammary gland tumours: a pilot study

Desmopressin (1-deamino-8-d-arginine vasopressin, also known as DDAVP) is a safe haemostatic compound capable of inhibiting lymph node and lung metastasis in a mouse model of mammary tumour manipulation and surgical excision. The aim of this study was to test the efficacy and safety of perioperative DDAVP (1microg/kg) in surgically treated bitches with mammary gland tumours (MGT). Twenty-one, otherwise healthy, intact bitches, with malignant MGT stage III or IV were randomly allocated to DDAVP (n=11) or placebo (n=10) groups. En bloc mastectomy of the affected gland/s was performed. DDAVP had a significant beneficial effect on disease-free period (P<0.01) and overall survival time (P<0.05). No side effects were seen in any of the cases. Whatever the mechanism of action, it seems that DDAVP may have a novel use in cancer surgery to minimise spread or survival of residual malignant cells. Additional, large scale controlled trials are required to fully evaluate this adjuvant pharmacological protocol.

The V2 vasopressin receptor stimulates ERK1/2 activity independently of heterotrimeric G protein signalling

The V2 vasopressin receptor (V2R) activates the mitogen activated protein kinases (MAPK) ERK1/2 through a mechanism involving the scaffolding protein beta arrestin. Here we report that this activating pathway is independent of G alpha s, G alpha i, G alpha q or G betagamma and that the V2R-mediated activation of G alpha s inhibits ERK1/2 activity in a cAMP/PKA-dependent manner. In the HEK293 cells studied, the beta arrestin-promoted activation was found to dominate over the PKA-mediated inhibition of the pathway, leading to a strong vasopressin-stimulated ERK1/2 activation. Despite the strong MAPK activation and in contrast with other GPCR, V2R did not induce any significant increase in DNA synthesis, consistent with the notion that the stable interaction between V2R and beta arrestin prevents signal propagation to the nucleus. Beta arrestin was found to be essential for the ERK1/2 activation, indicating that the recruitment of the scaffolding protein is necessary and sufficient to initiate the signal in the absence of any other stimulatory cues. Based on the use of selective pharmacological inhibitors, dominant negative mutants and siRNA, we conclude that the beta arrestin-dependent activation of ERK1/2 by the V2R involves c-Src and a metalloproteinase-dependent trans-activation event. These findings demonstrate that beta arrestin is a genuine signalling initiator that can, on its own, engage a MAPK activation machinery upon stimulation of a GPCR by its natural ligand.

An L-RNA-based aquaretic agent that inhibits vasopressin in vivo

A class of diuretic/aquaretic agents based on mirror-image oligonucleotides (so-called Spiegelmers) has been identified. These molecules directly bind and inhibit the neuropeptide vasopressin (AVP). AVP is the major regulatory component of body fluid homeostasis mediated through binding to the renal V(2) receptor. Elevated plasma levels of AVP are implicated in several pathological conditions, mainly cardiovascular diseases. In congestive heart failure, AVP is part of a neuroendocrine imbalance that is responsible for progressive worsening of the disease. Employing in vitro selection techniques, RNA aptamers that bind to the unnatural d-configuration of AVP were isolated. The best aptamer displayed an affinity to d-AVP of approximately 560 pM at 37 degrees C. The corresponding Spiegelmer, a 38-mer mirror-image oligonucleotide (l-RNA) termed NOX-F37, inhibits vasopressin-dependent activation of V(1a) as well as V(2) receptors with IC(50) values of 6.1 nM and 1 nM, respectively. NOX-F37 administered to healthy rats effectively neutralized AVP and increased diuresis dose-dependently for 24 h. The mode of action was strictly aquaretic, i.e., the increase in urine volume was not accompanied by an increase in electrolytes. These results clearly prove the in vivo efficacy of NOX-F37 and points out its potential as a drug in the treatment of diseases that are associated with body fluid overload.

Immunohistochemical detection of NRSA on small cell lung cancer with a monoclonal antibody (MAG-1) that recognizes the carboxyl terminus of provasopressin

A single monoclonal antibody (MAG-1) directed against the C-terminal 18-amino acid region (VAGc18) of provasopressin was examined as an agent for recognizing the tumor-specific NRSA marker common to small cell lung cancer (SCLC) in formalin-fixed tissues with ABC immunohistochemistry. SCLC tumors were obtained from several tissue locations and included primary, metastatic, and recurrent disease. Positive staining was found in 91% of cases (53/58). All five of the unreactive tumors were of the lungs or chest wall, and there did not appear to be an association of this negativity with disease stage, age, or sex. Alternatively, almost all primary lesions, almost all metastatic lesions, and all recurrent lesions examined gave a positive reaction with MAG-1. For this study, vasopressin-producing cells of the human anterior hypothalamus served as a positive control, while negative controls comprised normal lung tissue, tumor that received MAG-1 in the presence of an excess of antigen (VAGc18 peptide), or tumor reacted with a commercial IgG1 isotype as primary antibody. All of the results indicate that MAG-1 can be effectively used to selectively identify the NRSA marker on almost all SCLC tumors, at all disease stages, and at all locations. Since all four tumors tested showing no reactivity with MAG-1 gave a positive reaction for synaptophysin, it is proposed that a combined use of MAG-1 with synaptophysin antibodies could allow all SCLC tumors to be detected by ABC immunohistochemistry.

Oxytocin receptor pattern of expression in primary lung cancer and in normal human lung

In order to assess if oxytocin- and vasopressin-induced mitogenic effects detected on small-cell lung carcinoma (SCLC) cell lines could be transposed on primary SCLC, the aim of the present work was to identify mediators of these mitogenic actions on primary tumours samples. This was addressed on normal human lung tissue, on SCLC and on non-SCLC (NSCLC). Herein, we observe, in normal human lung, that OTR is colocalized with vascular endothelial cells of the lung and is not expressed by lung cells of epithelial nature. We detected mRNA amplification of V1aR, V2R and of a V2R variant. We observed that 86% of SCLC biopsies analyzed expressed at least the OTR and that 71% expressed the OTR, the V1aR and the V2R altogether. Comparatively, 50% of NSCLC biopsies tested expressed at least the OTR and 32% expressed the OTR, the V1aR and the V2R altogether. The occurrence of the V1bR/V3R is of 28 and 18% for SCLC and NSCLC, respectively. Nevertheless, for the SCLC biopsies analyzed in this study, V1bR/V3R expression correlates, in all cases, with the expression of all the other neurohypophysial peptide receptors. Our results suggest that neurohypophysial peptide antagonists may offer promise as a potential new therapeutic modality for the treatment of lung cancer expressing at least one of the neurhypophysial peptide receptor subtypes.

Expression of V1A and GRP receptors leads to cellular transformation and increased sensitivity to substance-P analogue-induced growth inhibition

Small-cell lung cancer (SCLC) is a particularly aggressive cancer, which metastasises early. Despite initial sensitivity to radio- and chemo-therapy, it invariably relapses, so that the 2-year survival remains less than 5%. Neuropeptides particularly arginine vasopressin (AVP) and gastrin-releasing peptide (GRP) act as autocrine and paracrine growth factors and the expression of these and their receptors are a hallmark of the disease. Substance-P analogues including [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-substance-P (SP-D) and [Arg6,D-Trp7,9,NmePhe8]-substance-P (6-11) (SP-G) inhibit the growth of SCLC cells by modulating neuropeptide signalling. We show that GRP and V1A receptors expression leads to the development of a transformed phenotype. Addition of neuropeptide provides some protection from etoposide-induced cytotoxicity. Receptor expression also leads to an increased sensitivity to substance-P analogue-induced growth inhibition. We show that SP-D and SP-G act as biased agonists at GRP and V1A receptors causing blockade of Gq-mediated Ca2+ release while directing signalling to activate ERK via a pertussis toxin-sensitive pathway. This is the first description of biased agonism at V1A receptors. This unique pharmacology governs the antiproliferative properties of these agents and highlights their potential therapeutic potential for the treatment of SCLC and particularly in tumours, which have developed resistance to chemotherapy.

N-Terminal Sugar Conjugation and C-Terminal Thr-for-Thr(ol) Exchange in Radioiodinated Tyr3-octreotide: Effect on Cellular Ligand Trafficking in Vitro and Tumor Accumulation in Vivo

For effective targeting of somatostatin receptor (sst) expressing tumors by radiolabeled octreotide analogues, high ligand uptake into sst-positive cells is mandatory. To optimize it, two modifications have been introduced into [(125)I]Tyr(3)-octreotide ([(125)I]TOC): C-terminal Thr-for-Thr(ol) exchange (leading to Tyr(3)-octreotate (TOCA)) and N-terminal derivatization with different carbohydrates. Both have significant impact on radioligand uptake into sst(2)-expressing cells in vitro and in vivo. Glucose conjugation via Amadori reaction by itself led to improved tumor uptake of [(123)I]Gluc-TOC in vivo, which is based on an enhancement of peptide internalization despite a reduction in receptor affinity. In the case of the doubly modified analogues [(123)I]Gluc-TOCA, [(123)I]Gluc-S-TOCA, and [(123)I]Gal-S-TOCA, a cumulative effect of both structural modifications was observed, leading up to a 5-fold increased uptake of these compounds in sst-expressing tumors compared to [(125)I]TOC. Thus, glycosylation with small carbohydrates was found to be a suitable tool to enhance receptor-mediated uptake of radiolabeled octreotide analogues into sst-positive malignancies, leading to tracers with excellent characteristics for in vivo sst-imaging applications.

Role of the thymus in the development of tolerance and autoimmunity towards the neuroendocrine system

The thymus is the unique lymphoid organ inside which a confrontation occurs throughout life between neuroendocrine self-antigens and a recently evolved system with original recombination machinery driving random generation of immune response diversity. Through transcription of neuroendocrine genes in the thymus stromal network and expression of cognate receptors by immature T cells, the neuroendocrine system regulates early T cell differentiation. In addition and more specifically, intrathymic presentation of neuroendocrine self-antigens by, or in close association with, major histocompatibility complex (MHC) proteins is responsible for the establishment of central immune self-tolerance of neuroendocrine principles. All members of the insulin gene (INS) family are expressed in the thymus stroma according to a precise hierarchy and cell topography: IGF2 (thymic epithelial cells) > IGF1 (thymic macrophages) >> INS (thymic medullary epithelial cells and/or dendritic cells). Given this hierarchical pattern in gene expression, the protein IGF-2 is more tolerated than INS. Igf2 transcription is defective in the thymus of bio-breeding (BB) rat, one animal model of type 1 diabetes (T1DM). This thymus-specific defect in Igf2 expression may explain both the absence of central tolerance to INS-secreting beta cells and the lymphopenia (including lack of regulatory RT6(+) T cells) in diabetes-prone BB rats. INS B:9-23 and the homologous sequence of IGF-2 compete for binding to DQ8, an MHC class II allele conferring major susceptibility to T1DM. In young DQ8(+) T1DM patients, INS B:9-23 presentation by DQ8 elicits a dominant IFN-gamma secretion by isolated PBMCs, whereas presentation of the IGF-2 self-antigen promotes a dominant regulatory interleukin-10 secretion. These data demonstrate that opposite immune responses are driven by MHC presentation of a self-antigen (here, IGF-2) and an autoantigen (INS, as "altered" self). The important tolerogenic properties of thymic self-antigens deserve now to be exploited for prevention and/or cure of devastating autoimmune diseases such as T1DM.

Upstream stimulatory factor activates the vasopressin promoter via multiple motifs, including a non-canonical E-box

We have described previously a complex E-box enhancer (-147) of the vasopressin promoter in small-cell lung cancer (SCLC) extracts [Coulson, Fiskerstrand, Woll and Quinn, (1999) Biochem. J. 344, 961-970]. Upstream stimulatory factor (USF) heterodimers were one of the complexes binding to this site in vitro. We now report that USF overexpression in non-SCLC (NSCLC) cells can functionally activate vasopressin promoter-driven reporters that are otherwise inactive in this type of lung cancer cell. Site-directed mutagenesis and electrophoretic mobility-shift analysis demonstrate that although the -147 E-box contributes, none of the previously predicted E-boxes (-147, -135, -34) wholly account for this USF-mediated activation in NSCLC. 5' Deletion showed the key promoter region as -52 to +42; however, USF-2 binding was not reliant on the -34 E-box, but on a novel adjacent CACGGG non-canonical E-box at -42 (motif E). This mediated USF binding in both SCLC and USF-2-transfected NSCLC cells. Mutation of motif E or the non-canonical TATA box abolished activity, implying both are required for transcriptional initiation on overexpression of USF-2. Co-transfected dominant negative USF confirmed that binding was required through motif E for function, but that the classical activation domain of USF was not essential. USF-2 bound motif E with 10-fold lower affinity than the -147 E-box. In NSCLC, endogenous USF-2 expression is low, and this basal level appears to be insufficient to activate transcription of arginine vasopressin (AVP). In summary, we have demonstrated a novel mechanism for USF activation, which contributes to differential vasopressin expression in lung cancer.

Thymic neuroendocrine self-antigens. Role in T-cell development and central T-cell self-tolerance

The repertoire of thymic neuroendocrine precursors plays a dual role in T-cell differentiation as the source of either cryptocrine accessory signals in T-cell development or neuroendocrine self-antigens presented by the thymic major histocompatibility complex (MHC) machinery. Thymic neuroendocrine self-antigens usually correspond to peptide sequences highly conserved during the evolution of one family. The thymic presentation of some neuroendocrine self-antigens is not restricted by MHC alleles. Oxytocin (OT) is the dominant peptide of the neurohypophysial family. It is expressed by thymic epithelial and nurse cells (TEC/TNCs) of different species. Ontogenetic studies have shown that the thymic expression of the OT gene precedes the hypothalamic one. Both OT and VP stimulate the phosphorylation of p125FAK and other focal adhesion-related proteins in murine immature T cells. These early cell activation events could play a role in the promotion of close interactions between thymic stromal cells and developing T cells. It is established that such interactions are fundamental for the progression of thymic T-cell differentiation. Insulin-like growth factor 2 (IGF-2) is the dominant thymic polypeptide of the insulin family. Using fetal thymic organ cultures (FTOCs), the inhibition of thymic IGF-2-mediated signaling was shown to block the early stages of T-cell differentiation. The treatment of FTOCs with an mAb anti-(pro)insulin had no effect on T-cell development. In an animal model of autoimmune type 1 diabetes (BB rat), thymic levels of (pro)insulin and IGF-1 mRNAs were normal both in diabetes-resistant and diabetes-prone BB rats. IGF-2 transcripts were clearly identified in all thymuses from diabetes-resistant adult (5-week) and young (2- and 5-days) BB rats. In marked contrast, the IGF-2 transcripts were absent and the IGF-2 protein was almost undetectable in +/- 80% of the thymuses from diabetes-prone adult and young BB rats. These data show that a defect of the thymic IGF-2-mediated tolerogenic function might play an important role in the pathophysiology of autoimmune Type 1 diabetes.