Four cardiac hormones eliminate 4-fold more human glioblastoma cells than the green mamba snake peptide

Natriuretic peptides: Another tool for the management of cancer?

The connection between heart failure (HF) and cancer through multiple pathways such as inflammation, oxidative stress, and neurohormonal activation, among others, is well established. As a consequence, increases in plasma levels of several biomarkers have been described in both disorders. The most consistent information is related to natriuretic peptides (NPs). Although they are known to be produced in the ventricles as a response to myocardial distension, and thus can be useful for the diagnosis and prognosis of HF, and also for the management of chemotherapy-induced myocardial damage, they are also produced by tumour cells. In this regard, increased plasma levels of NPs have been described in patients with multiple malignancies in the absence of volume overload. Natriuretic peptide levels have been shown to correlate directly with the extension of tumours and with poorer outcomes. Moreover, some data indicate that they may help in the detection of subclinical tumours. Given that these peptides have been described to have anti-proliferative and anti-angiogenic effects, a plausible hypothesis is that they may be produced by tumours as a negative feed-back mechanism to avoid tumour progression. This would lead to increased levels of NPs in plasma that could be potentially useful for early detection of malignancies as well as for a prognostic assessment. Nevertheless, since the sample size of many studies published so far is limited, more data are needed to provide consistent data in order to confirm or rule out this hypothesis.

C Type Natriuretic Peptide Receptor Activation Inhibits Sodium Channel Activity in Human Aortic Endothelial Cells by Activating the Diacylglycerol-Protein Kinase C Pathway

The C-type natriuretic peptide receptor (NPRC) is expressed in many cell types and binds all natriuretic peptides with high affinity. Ligand binding results in the activation or inhibition of various intracellular signaling pathways. Although NPRC ligand binding has been shown to regulate various ion channels, the regulation of endothelial sodium channel (EnNaC) activity by NPRC activation has not been studied. The objective of this study was to investigate mechanisms of EnNaC regulation associated with NPRC activation in human aortic endothelial cells (hAoEC). EnNaC protein expression and activity was attenuated after treating hAoEC with the NPRC agonist cANF compared to vehicle, as demonstrated by Western blotting and patch clamping studies, respectively. NPRC knockdown studies using siRNA's corroborated the specificity of EnNaC regulation by NPRC activation mediated by ligand binding. The concentration of multiple diacylglycerols (DAG) and the activity of protein kinase C (PKC) was augmented after treating hAoEC with cANF compared to vehicle, suggesting EnNaC activity is down-regulated upon NPRC ligand binding in a DAG-PKC dependent manner. The reciprocal cross-talk between NPRC activation and EnNaC inhibition represents a feedback mechanism that presumably is involved in the regulation of endothelial function and aortic stiffness.

Evaluation of the use of therapeutic peptides for cancer treatment

Cancer along with cardiovascular disease are the main causes of death in the industrialised countries around the World. Conventional cancer treatments are losing their therapeutic uses due to drug resistance, lack of tumour selectivity and solubility and as such there is a need to develop new therapeutic agents. Therapeutic peptides are a promising and a novel approach to treat many diseases including cancer. They have several advantages over proteins or antibodies: as they are (a) easy to synthesise, (b) have a high target specificity and selectivity and (c) have low toxicity. Therapeutic peptides do have some significant drawbacks related to their stability and short half-life. In this review, strategies used to overcome peptide limitations and to enhance their therapeutic effect will be compared. The use of short cell permeable peptides that interfere and inhibit protein-protein interactions will also be evaluated.

Natriuretic peptide receptor A as a novel target for cancer

The receptor for the cardiac hormone atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPR-A), has been reported to be expressed in lung cancer, prostate cancer and ovarian cancer. NPR-A expression and signaling is important for tumor growth; its deficiency protects C57BL/6 mice from lung, skin and ovarian cancers. This suggests that NPR-A is a new marker and a new target for cancer therapy. Recently, NPR-A has been demonstrated to be expressed in pre-implantation embryos and in embryonic stem cells, which has a novel role in the maintenance of self-renewal and pluripotency of embryonic stem cells. A nanoparticle-formulated interfering RNA for NPR-A attenuated B16 melanoma tumors in mice. Ectopic expression of a plasmid encoding NP73-102, the NH2-terminal peptide of the ANP prohormone which downregulates NPR-A expression, also suppressed lung metastasis of A549 cells in nude mice and tumorigenesis of Line 1 cells in immunocompetent BALB/c mice. These results suggest that NPR-A is involved in tumorigenesis and a new target for cancer therapy. This review focuses on structure, abnormal functions and carcinogenic mechanisms of NPR-A to investigate its role in tumorigenesis.

Cardiac hormones for the treatment of cancer

Four cardiac hormones, namely atrial natriuretic peptide, vessel dilator, kaliuretic peptide, and long-acting natriuretic peptide, reduce up to 97% of all cancer cells in vitro. These four cardiac hormones eliminate up to 86% of human small-cell lung carcinomas, two-thirds of human breast cancers, and up to 80% of human pancreatic adenocarcinomas growing in athymic mice. Their anticancer mechanisms of action, after binding to specific receptors on cancer cells, include targeting the rat sarcoma-bound GTP (RAS) (95% inhibition)-mitogen-activated protein kinase kinase 1/2 (MEK 1/2) (98% inhibition)-extracellular signal-related kinase 1/2 (ERK 1/2) (96% inhibition) cascade in cancer cells. They also inhibit MAPK9, i.e. c-Jun N-terminal kinase 2. They are dual inhibitors of vascular endothelial growth factor (VEGF) and its VEGFR2 receptor (up to 89%). One of the downstream targets of VEGF is β-catenin, which they reduce up to 88%. The WNT pathway is inhibited up to 68% and secreted frizzled-related protein 3 decreased up to 84% by the four cardiac hormones. AKT, a serine/threonine protein kinase, is reduced up to 64% by the cardiac hormones. STAT3, a final 'switch' that activates gene expression that leads to malignancy, is decreased by up to 88% by the cardiac hormones. STAT3 is specifically decreased as they do not affect STAT1. There is a cross-talk between the RAS-MEK 1/2-ERK 1/2 kinase cascade, VEGF, β-catenin, WNT, JNK, and STAT pathways and each of these pathways is inhibited by the cardiac hormones.

Transcriptome and Coexpression Network Analysis of the Human Glioma Cell Line Hs683 Exposed to Candoxin

OBJECTIVE: Gliomas are the most common primary tumours of the central nervous system. Snake venom, such as candoxin (CDX) isolated from Bungarus candidus, inhibits glioma cell proliferation. This study explored the gene regulation profile of CDX-treated human glioma Hs683 cells. METHODS: Using microarray technology and bioinformatics analyses the underlying molecular mechanism of action of CDX was evaluated by constructing gene regulation and protein—protein interaction coexpression networks. RESULTS: CDX treatment induced a large number of related genes at the transcriptional level. The MYC gene (v-myc myelocytomatosis viral oncogene homologue [avian]) had a key role in the response of Hs683 cells to CDX treatment. Activation of MYC upregulated NDRG1 (N-myc downstream regulated 1), WNT10B (wingless-type mouse mammary tumour virus integration site family, member 10B), CASP9 (caspase 9, apoptosis-related cysteine peptidase) and CDKN2A (cyclin-dependent kinase inhibitor 2A), and downregulated ID3 (inhibitor of DNA binding 3, dominant negative helix—loop—helix protein) and SLC1A4 (solute carrier family 1 [glutamate/neutral amino acid transporter], member 4). In addition, a subnetwork was constructed among SPP1 (secreted phosphoprotein 1), SDC1 (syndecan 1) and CD44 based on protein—protein interactions, and these genes were predicted to be involved in glioma cell invasion. CONCLUSION: These findings might provide novel therapeutic targets for glioma chemotherapy.

CAMTA1 is a novel tumour suppressor regulated by miR-9/9* in glioblastoma stem cells

Cancer stem cells or cancer initiating cells are believed to contribute to cancer recurrence after therapy. MicroRNAs (miRNAs) are short RNA molecules with fundamental roles in gene regulation. The role of miRNAs in cancer stem cells is only poorly understood. Here, we report miRNA expression profiles of glioblastoma stem cell-containing CD133(+) cell populations. We find that miR-9, miR-9(*) (referred to as miR-9/9(*)), miR-17 and miR-106b are highly abundant in CD133(+) cells. Furthermore, inhibition of miR-9/9(*) or miR-17 leads to reduced neurosphere formation and stimulates cell differentiation. Calmodulin-binding transcription activator 1 (CAMTA1) is a putative transcription factor, which induces the expression of the anti-proliferative cardiac hormone natriuretic peptide A (NPPA). We identify CAMTA1 as an miR-9/9(*) and miR-17 target. CAMTA1 expression leads to reduced neurosphere formation and tumour growth in nude mice, suggesting that CAMTA1 can function as tumour suppressor. Consistently, CAMTA1 and NPPA expression correlate with patient survival. Our findings could provide a basis for novel strategies of glioblastoma therapy.

Cardiac Hormones Target the Ras-MEK 1/2-ERK 1/2 Kinase Cancer Signaling Pathways

The heart is a sophisticated endocrine gland synthesizing the atrial natriuretic peptide prohormone which contains four peptide hormones, i.e., atrial natriuretic peptide, vessel dilator, kaliuretic peptide and long-acting natriuretic peptide, which decrease up to 97% of human pancreatic, breast, colon, prostate, kidney and ovarian carcinomas as well as small-cell and squamous cell lung cancer cells in cell culture. In vivo, these four cardiac hormones eliminate up to 80% of human pancreatic adenocarcinomas, two-thirds of human breast cancers, and up to 86% of human small-cell lung cancers growing in athymic mice. Their signaling in cancer cells includes inhibition of up to 95% of the basal activity of Ras, 98% inhibition of the phosphorylation of the MEK 1/2 kinases and 97% inhibition of the activation of basal activity of the ERK 1/2 kinases mediated via the intracellular messenger cyclic GMP. They also completely block the activity of mitogens such as epidermal growth factor's ability to stimulate ERK and Ras. They do not inhibit the activity of ERK in healthy cells such as human fibroblasts. The final step in their anticancer mechanism of action is that they enter the nucleus as demonstrated by immunocytochemical studies to inhibit DNA synthesis within cancer cells.

C-type natriuretic peptide receptor expression in pancreatic alpha cells

Atrial natriuretic peptide (ANP), brain type natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) comprise a family of natriuretic peptides that mediate their biological effects through three natriuretic peptide receptor subtypes, NPR-A (ANP, BNP), NPR-B (CNP) and NPR-C (ANP, BNP, CNP). Several reports have provided evidence for the expression of ANP and specific binding sites for ANP in the pancreas. The purpose of this study was to identify the ANP receptor subtype and to localize its expression to a specific cell type in the human pancreas. NPR-C immunoreactivity, but neither ANP nor NPR-A, was detected in human islets by immunofluorescent staining. No immunostaining was observed in the exocrine pancreas or ductal structures. Double-staining revealed that NPR-C was expressed mainly in the glucagon-containing alpha cells. NPR-C mRNA and protein were detected in isolated human islets by RT-PCR and Western blot analysis, respectively. NPR-C expression was also detected by immunofluorescent staining in glucagonoma but not in insulinoma. ANP, as well as BNP and CNP, stimulated glucagon secretion from perifused human islets (1,111 +/- 55% vs. basal [7.3 fmol/min]; P < 0.001). This response was mimicked by cANP(4-23), a selective agonist of NPR-C. In conclusion, the NPR-C receptor is expressed in normal and neoplastic human alpha cells. These findings suggest a role for natriuretic peptides in the regulation of glucagon secretion from human alpha cells.