With-no-lysine (WNK) kinases are highly expressed along the mammalian distal nephron. Mutations in either WNK1 or WNK4 cause familial hyperkalemic hypertension (FHHt), suggesting that the protein products converge on a final common pathway. We showed previously that WNK4 downregulates thiazide-sensitive NaCl cotransporter (NCC) activity, an effect suppressed by WNK1. Here we investigated the mechanisms by which WNK1 and WNK4 interact to regulate ion transport. We report that WNK1 suppresses the WNK4 effect on NCC activity and associates with WNK4 in a protein complex involving the kinase domains. Although a kinase-dead WNK1 also associates with WNK4, it fails to suppress WNK4-mediated NCC inhibition; the WNK1 kinase domain alone, however, is not sufficient to block the WNK4 effect. The carboxyterminal 222 amino acids of WNK4 are sufficient to inhibit NCC, but this fragment is not blocked by WNK1. Instead, WNK1 inhibition requires an intact WNK4 kinase domain, the region that binds to WNK1. In summary, these data show that: (a) the WNK4 carboxyl terminus mediates NCC suppression, (b) the WNK1 kinase domain interacts with the WNK4 kinase domain, and (c) WNK1 inhibition of WNK4 is dependent on WNK1 catalytic activity and an intact WNK1 protein. These findings provide insight into the complex interrelationships between WNK1 and WNK4 and provide a molecular basis for FHHt. IntroductionFamilial hyperkalemic hypertension (FHHt; also known as pseudohypoaldosteronism type II; Online Mendelian Inheritance in Man reference number #145260) is an autosomal dominant disease characterized by hypertension, hyperkalemia, and sensitivity to thiazide diuretics. Wilson and colleagues (1) reported that mutations in 2 genes encoding homologous proteins, WNK1 (PRKWNK1) and WNK4 (PRKWNK4), can cause FHHt. The with-no-lysine (WNK) kinases are novel serine/threonine kinases that were named because they lack lysine at a location previously thought to be essential for kinase activity (2). Both WNK1 and WNK4 are highly expressed in the kidney. The FHHt-causing WNK1 mutations are deletions within the first intron. These mutations increase WNK1 expression in leukocytes and were postulated to be gain-of-function mutations (1). Recently, heterozygous WNK1-deficient mice were shown to exhibit lower blood pressure than wild-type controls (3), supporting the hypothesis that WNK1 exerts a positive effect on blood pressure. The WNK4 mutations that cause FHHt are discrete missense mutations in 2 areas of the coding region (1). These mutations cause phenotypic features similar to those that result from WNK1 intron mutations (1), but the mechanisms involved may be different.We showed previously that WNK4 inhibits the thiazide-sensitive NaCl cotransporter (NCC, gene symbol SLC12A3) when expressed in Xenopus oocytes (4); similar results were obtained by others (5).

With-no-lysine (WNK) kinases are highly expressed along the mammalian distal nephron. Mutations in either WNK1 or WNK4 cause familial hyperkalemic hypertension (FHHt), suggesting that the protein products converge on a final common pathway. We showed previously that WNK4 downregulates thiazide-sensitive NaCl cotransporter (NCC) activity, an effect suppressed by WNK1. Here we investigated the mechanisms by which WNK1 and WNK4 interact to regulate ion transport. We report that WNK1 suppresses the WNK4 effect on NCC activity and associates with WNK4 in a protein complex involving the kinase domains. Although a kinase-dead WNK1 also associates with WNK4, it fails to suppress WNK4-mediated NCC inhibition; the WNK1 kinase domain alone, however, is not sufficient to block the WNK4 effect. The carboxyterminal 222 amino acids of WNK4 are sufficient to inhibit NCC, but this fragment is not blocked by WNK1. Instead, WNK1 inhibition requires an intact WNK4 kinase domain, the region that binds to WNK1. In summary, these data show that: (a) the WNK4 carboxyl terminus mediates NCC suppression, (b) the WNK1 kinase domain interacts with the WNK4 kinase domain, and (c) WNK1 inhibition of WNK4 is dependent on WNK1 catalytic activity and an intact WNK1 protein. These findings provide insight into the complex interrelationships between WNK1 and WNK4 and provide a molecular basis for FHHt. IntroductionFamilial hyperkalemic hypertension (FHHt; also known as pseudohypoaldosteronism type II; Online Mendelian Inheritance in Man reference number #145260) is an autosomal dominant disease characterized by hypertension, hyperkalemia, and sensitivity to thiazide diuretics. Wilson and colleagues (1) reported that mutations in 2 genes encoding homologous proteins, WNK1 (PRKWNK1) and WNK4 (PRKWNK4), can cause FHHt. The with-no-lysine (WNK) kinases are novel serine/threonine kinases that were named because they lack lysine at a location previously thought to be essential for kinase activity (2). Both WNK1 and WNK4 are highly expressed in the kidney. The FHHt-causing WNK1 mutations are deletions within the first intron. These mutations increase WNK1 expression in leukocytes and were postulated to be gain-of-function mutations (1). Recently, heterozygous WNK1-deficient mice were shown to exhibit lower blood pressure than wild-type controls (3), supporting the hypothesis that WNK1 exerts a positive effect on blood pressure. The WNK4 mutations that cause FHHt are discrete missense mutations in 2 areas of the coding region (1). These mutations cause phenotypic features similar to those that result from WNK1 intron mutations (1), but the mechanisms involved may be different.We showed previously that WNK4 inhibits the thiazide-sensitive NaCl cotransporter (NCC, gene symbol SLC12A3) when expressed in Xenopus oocytes (4); similar results were obtained by others (5).

Emodin, a tyrosine kinase inhibitor, is a natural anthraquinone derivative found in the roots and rhizomes of numerous plants. The inhibitory effect of emodin on mammalian cell cycle modulation in specific oncogene-overexpressing cells has formed the basis for using this compound as an anticancer drug. Previous reviews have summarized the antitumor properties of emodin. However, the specific molecular mechanisms of emodin-mediated tumor inhibition have not been completely elucidated over the last 5 years. Recently, there has been great progress in the preclinical study of the anticancer mechanisms of emodin. Our recent study revealed that emodin has therapeutic effects on pancreatic cancer through various antitumor mechanisms. Notably, the therapeutic efficacy of emodin in combination with chemotherapy was found to be higher than the comparable single chemotherapeutic regime, and the combination therapy also exhibited fewer side-effects. Despite these encouraging results, further investigation is warranted as emodin has been shown to modulate one or more key regulators of cancer growth. This review provides an overview of the distinct mechanisms of anticancer action of emodin in different body systems identified over the past 5 years. These new breakthrough findings may have important implications for targeted cancer therapy and for the future clinical use of emodin.

BackgroundEmodin has been showed to induce apoptosis of pancreatic cancer cells and inhibit tumor growth in our previous studies. This study was designed to investigate whether emodin could inhibit the angiogenesis of pancreatic cancer tissues and its mechanism.Methodology/Principal FindingIn accordance with our previous study, emodin inhibited pancreatic cancer cell growth, induced apoptosis, and enhanced the anti-tumor effect of gemcitabine on pancreatic caner cells in vitro and in vivo by inhibiting the activity of NF-κB. Here, for the first time, we demonstrated that emodin inhibited tumor angiogenesis in vitro and in implanted pancreatic cancer tissues, decreased the expression of angiogenesis-associated factors (NF-κB and its regulated factors VEGF, MMP-2, MMP-9, and eNOS), and reduced eNOS phosphorylation, as evidenced by both immunohistochemistry and western blot analysis of implanted tumors. In addition, we found that emodin had no effect on VEGFR expression in vivo.Conclusions/SignificanceOur results suggested that emodin has potential anti-tumor effect on pancreatic cancer via its dual role in the promotion of apoptosis and suppression of angiogenesis, probably through regulating the expression of NF-κB and NF-κB-regulated angiogenesis-associated factors.

Evodiamine has therapeutic potential against cancers. This study was designed to investigate whether combination therapy with gemcitabine and evodiamine enhanced antitumor efficacy in pancreatic cancer. In vitro application of the combination therapy triggered significantly higher frequency of pancreatic cancer cells apoptosis, inhibited the activities of PI3K, Akt, PKA, mTOR and PTEN, and decreased the activation of NF-κB and expression of NF-κB-regulated products. In vivo application of the combination therapy induced significant enhancement of tumor cell apoptosis, reductions in tumor volume, and inhibited activation of mTOR and PTEN. In conclusion, evodiamine can augment the therapeutic effect of gemcitabine in pancreatic cancer through direct or indirect negative regulation of the PI3K/Akt pathway.

Oxymatrine, the main alkaloid component in the traditional Chinese herbal medicine Sophora japonica (Sophora flavescens Ait), has been reported to have antitumor properties. However, the mechanisms of action in human pancreatic cancer are not well established to date. In the present study, we investigated the antiangiogenic effects of oxymatrine on human pancreatic cancer as well as the possible mechanisms involved. The results of the cell viability assay showed that treatment of PANC-1 pancreatic cancer cells with oxymatrine resulted in cell growth inhibition in a dose- and time-dependent manner. To investigate the possible mechanisms involved in these events, we performed western blotting and reverse transcription-polymerase chain reaction (RT-PCR) analysis. The results revealed that oxymatrine decreased the expression of angiogenesis-associated factors, including nuclear factor κB (NF-κB) and vascular endothelial growth factor (VEGF). Finally, the antiproliferative and antiangiogenic effects of oxymatrine on human pancreatic cancer were further confirmed in pancreatic cancer xenograft tumors in nude mice. In conclusion, our studies for the first time suggest that oxymatrine has potential antitumor effects on pancreatic cancer via suppression of angiogenesis, probably through regulation of the expression of the NF-κB-mediated VEGF signaling pathway.

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Ginsenoside Rg3 (Rg3), a trace tetracyclic triterpenoid saponin, is extracted from ginseng and shown to have anticancer activity against several types of cancers. This study explored the effect of Rg3 on pancreatic cancer vasculogenic mimicry. Altered vasculogenic mimicry formation was assessed using immunohistochemistry and PAS staining and associated with the expression of vascular endothelial-cadherin (VE-cadherin), epithelial cell kinase (EphA2), matrix metalloproteinase (MMP)-2 and MMP-9. The effect of Rg3 on the regulation of pancreatic cancer vasculogenic mimicry was evaluated in vitro and in vivo. The data showed vasculogenic mimicry in pancreatic cancer tissues. In addition, the expression of VE-cadherin, EphA2, MMP-2 and MMP-9 proteins associated with formation of pancreatic cancer vasculogenic mimicry. Rg3 treatment reduced the levels of vasculogenic mimicry in nude mouse xenografts in vitro and in vivo, while the expression of VE-cadherin, EphA2, MMP-2 and MMP-9 mRNA and proteins was downregulated by Rg3 treatment in vitro and in tumor xenografts. In conclusion, ginsenoside Rg3 effectively inhibited the formation of pancreatic cancer vasculogenic mimicry by downregulating the expression of VE-cadherin, EphA2, MMP9 and MMP2. Further studies are required to evaluate ginsenoside Rg3 as an agent to control pancreatic cancer.