Wnt signaling inhibits Forkhead box O3a-induced transcription and apoptosis through up-regulation of serum- and glucocorticoid-inducible kinase 1

Solid pseudopapillary neoplasm (SPN) of the pancreas: current understanding on its malignant potential and management

Solid pseudopapillary neoplasms (SPN) of the pancreas are presently recognized as low-grade malignant tumors that are frequently observed in young females. This tumor has a low incidence and is associated with an excellent prognosis following surgical resection. Typical SPNs primarily affect the pancreas and tend to have moderate or asymptomatic manifestations. Based on retrospective research, it is anticipated that patients with SPN can achieve disease-free survival, even in cases when metastasis is detected during inspection. However, the incidence of malignant SPN has been consistently underestimated, as evidenced by recent research findings. Malignancy of SPN primarily encompasses invasion and infiltration, metastasis, and recurrence after R0 resection. Imaging technologies such as Ultrasound, Computed Tomography, Magnetic Resonance Imaging, and Position Emission Tomography are capable of preliminarily identifying malignant SPN, which is primarily based on its invasive clinical features. Research on risk factors of malignant SPN revealed that larger tumor size, Ki-67 index, and several other parameters had significant correlations with invasive tumor behavior. Pathologic features of malignant SPNs overlay other pancreatic tumors, nevertheless they can provide valuable assistance in the process of diagnosis. Several confirmed specific pathologic biomarkers are related to its cellular origin, characteristic gene mutation, and cell proliferation. Considering the invasiveness of malignant SPN, it is imperative to enhance the comprehensiveness of its therapy. Tumor resection remains a suggested course of action in line with typical SPN, and additional lymph node dissection is seen as reasonable. Compared to benign SPNs, malignant SPNs have worse prognosis, underscoring the necessity of early identification and treatment in comprehensive medical centers to get improved clinical outcomes.

MicroRNAs as the Critical Regulators of Forkhead Box Protein Family in Pancreatic, Thyroid, and Liver Cancers

The metabolism of human body is mainly regulated by the pancreas, liver, and thyroid using the hormones or exocrine secretions that affect the metabolic processes from food digestion to intracellular metabolism. Therefore, metabolic organ disorders have wide clinical symptoms that severely affect the quality of patient's life. The pancreatic, liver, and thyroid cancers as the main malignancies of the metabolic system have always been considered as one of the serious health challenges worldwide. Despite the novel therapeutic modalities, there are still significant high mortality and recurrence rates, especially in liver and pancreatic cancer patients which are mainly related to the late diagnosis. Therefore, it is required to assess the molecular bases of tumor progressions to introduce novel early detection and therapeutic markers in these malignancies. Forkhead box (FOX) protein family is a group of transcription factors that have pivotal roles in regulation of cell proliferation, migration, and apoptosis. They function as oncogene or tumor suppressor during tumor progression. MicroRNAs (miRNAs) are also involved in regulation of cellular processes. Therefore, in the present review, we discussed the role of miRNAs during pancreatic, thyroid, and liver tumor progressions through FOX regulation. It has been shown that miRNAs were mainly involved in tumor progression via FOXM and FOXO targeting. This review paves the way for the introduction of miR/FOX axis as an efficient early detection marker and therapeutic target in pancreatic, thyroid, and liver tumors.

Low-dose dexamethasone promotes osteoblast viability by activating autophagy via the SGK1/FOXO3a signaling pathway

Autophagy contributes to bone homeostasis and development under physiological conditions. Although previous studies have demonstrated the induction of the autophagy machinery by endogenous glucocorticoids (GCs), the precise mechanisms involved have not yet been clarified. The current study aimed to explore the effect of a low dose of GC (10^-8 M dexamethasone, Dex) on autophagy in mouse embryonic osteoblastic precursor cells (MC3T3-E1 cells) and the potential mechanisms. The results showed that 10^-8 M Dex induced significant time-dependent increases in the expression and activation of serum- and glucocorticoid-induced kinase-1 (SGK1) in MC3T3-E1 cells and that these effects were accompanied by increased cell viability and decreased apoptosis. The autophagy inhibitor 3-MA significantly inhibited Dex-mediated promotion of viability. Moreover, Dex increased LC3II and Beclin-1 levels and decreased SQSTM/p62 levels in a time-dependent manner, and these effects were attenuated by pretreatment with 3-MA. Transfection of Dex-treated MC3T3-E1 cells with shRNA-SGK1 resulted in a significant reduction in cell viability and an increase in apoptosis. 3-MA further exacerbated these effects of SGK1 inhibition. Knocking down SGK1 before Dex exposure significantly reduced the phosphorylated forkhead box O3a (p-FOXO3a)/FOXO3 ratio, suppressed LC3II and Beclin-1 levels, and increased SQSTM/p62 levels in MC3T3-E1 cells, and these effects were amplified by 3-MA. In conclusion, the results revealed that low-dose GC treatment increased osteoblast viability by activating autophagy via the SGK1/FOXO3a pathway.

The complex network of transcription factors, immune checkpoint inhibitors and stemness features in colorectal cancer: A recent update

Cancer immunity is regulated by several mechanisms that include co-stimulatory and/or co-inhibitory molecules known as immune checkpoints expressed by the immune cells. In colorectal cancer (CRC), CTLA-4, LAG3, TIM-3 and PD-1 are the major co-inhibitory checkpoints involved in tumor development and progression. On the other hand, the deregulation of transcription factors and cancer stem cells activity plays a major role in the development of drug resistance and in the spread of metastatic disease in CRC. In this review, we describe how the modulation of such transcription factors affects the response of CRC to therapies. We also focus on the role of cancer stem cells in tumor metastasis and chemoresistance and discuss both preclinical and clinical approaches for targeting stem cells to prevent their tumorigenic effect. Finally, we provide an update on the clinical applications of immune checkpoint inhibitors in CRC and discuss the regulatory effects of transcription factors on the expression of the immune inhibitory checkpoints with specific focus on the PD-1 and PD-L1 molecules.

The Mechanistic Roles of Sirtuins in Breast and Prostate Cancer

Simple Summary

There are diverse reports of the dual role of sirtuin genes and proteins in breast and prostate cancers. This review discusses the current information on the tumor promotion or suppression roles of SIRT1–7 in breast and prostate cancers. Precisely, we highlight that sirtuins regulate various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of both breast and prostate cancer. We also provide evidence of the direct regulation of sirtuins by miRNAs, highlighting the consequences of this regulation in breast and prostate cancer. Overall, this review reveals the potential value of sirtuins as biomarkers and/or targets for improved treatment of breast and prostate cancers.

Abstract

Mammalian sirtuins (SIRT1–7) are involved in a myriad of cellular processes, including apoptosis, proliferation, differentiation, epithelial-mesenchymal transition, aging, DNA repair, senescence, viability, survival, and stress response. In this review, we discuss the current information on the mechanistic roles of SIRT1–7 and their downstream effects (tumor promotion or suppression) in cancers of the breast and prostate. Specifically, we highlight the involvement of sirtuins in the regulation of various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of breast and prostate cancer. Additionally, we highlight the available information regarding SIRT1–7 regulation by miRNAs, laying much emphasis on the consequences in the progression of breast and prostate cancer.

FoxO3 might be involved in the inflammatory response of human monocytes to lipopolysaccharide through regulating expression of toll like receptor 4

OBJECTIVE

Previous studies have found that forkhead box o3 S574 phosphorylation status can regulate inflammation by inducing monocytes/macrophages apoptosis, and whether it directly affects the inflammatory response of monocytes has not been demonstrated. The aim of this study was to investigate the role of forkhead box o3 in inflammatory response of monocytes against lipopolysaccharide.

METHODS

THP-1 cells were used to knock down or overexpress forkhead box o3 and its mutants, and then detect the activation of inflammatory cytokines expression and activation of nuclear factor kappa B after lipopolysaccharide treatment.

RESULTS

The present study demonstrated that lipopolysaccharide can up-regulate forkhead box o3 protein expression, especially the non-phosphorylated form at S574, in a post-transcriptional way. Knockdown of forkhead box o3 attenuated lipopolysaccharide mediated nuclear factor kappa B activation and downstream inflammatory cytokines expression. When overexpressing forkhead box o3, only non-phosphorylated S574A forkhead box o3 mutant enhanced lipopolysaccharide induced nuclear factor kappa B activation and inflammatory cytokines expression. Further studies have found that S574A forkhead box o3 may promote toll like receptor 4 expression through binding and accelerating its transcriptional activity from promoter.

CONCLUSION

There might be a positive feedback loop between lipopolysaccharide and forkhead box o3 in monocytes to promote the lipopolysaccharide mediated inflammatory response.

SGK1, a Serine/Threonine Kinase, Inhibits Prototype Foamy Virus Replication

Foamy viruses (FVs) are complex retroviruses belonging to the Spumaretrovirinae subfamily of the Retroviridae family. In contrast to human immunodeficiency virus (HIV), another member of the Retroviridae family, FVs are nonpathogenic in their natural hosts or in experimentally infected animals. Prototype foamy virus (PFV) is the only foamy virus that can infect humans through cross-species transmission and does not show any pathogenicity after infection. Consequently, PFV is considered a safe and efficient gene transfer vector. Understanding the host proteins involved in the replication of PFV and the mechanism of interaction between the host and the virus might lead to studies to improve the efficiency of gene transfer. To date, only a few host factors have been identified that affect PFV replication. In the present study, we report that PFV infection enhances the promoter activity of SGK1 (encoding serum/glucocorticoid regulated kinase 1) via the Tas protein signaling pathway, and then upregulates the mRNA and protein levels of SGK1. Overexpression of SGK1 reduced PFV replication, whereas its depletion using small interfering RNA increased PFV replication. SGK1 inhibits PFV replication by impairing the function of the PFV Tas activation domain in a kinase-independent manner and reducing the stability of the Gag protein in a kinase-dependent manner. In addition, both human and bovine SGK1 proteins inhibit the replication of bovine foamy virus (BFV) and PFV. These findings not only improved our understanding of the function of SGK1 and its relationship with foamy viruses, but also contributed to determining the antiviral mechanism of the host.

IMPORTANCE Foamy viruses can integrate into the host chromosome and are nonpathogenic in natural hosts or in experimentally infected animals. Therefore, foamy viruses are considered to be safe and efficient gene transfer vectors. Persistent infection of foamy viruses is partly caused by the restrictive effect of host factors on the virus. However, only a few cellular proteins are known to influence the replication of foamy viruses. In this study, we report that SGK1 inhibits the replication of prototype foamy virus by affecting the function of the transcription activator, Tas, and reducing the stability of the structural protein, Gag. These results will increase our understanding of the interaction between the virus and host factors, deepening our perception of host antiviral defenses and the function of SGK1, and could improve the gene transfer efficiency of foamy viruses.

Intestinal Wnt in the transition from physiology to oncology

Adult stem cells are necessary for self-renewal tissues and regeneration after damage. Especially in the intestine, which self-renews every few days, they play a key role in tissue homeostasis. Therefore, complex regulatory mechanisms are needed to prevent hyperproliferation, which can lead in the worst case to carcinogenesis or under-activation of stem cells, which can result in dysfunctional epithelial. One main regulatory signaling pathway is the Wnt/β-catenin signaling pathway. It is a highly conserved pathway, with β-catenin, a transcription factor, as target protein. Translocation of β-catenin from cytoplasm to nucleus activates the transcription of numerous genes involved in regulating stem cell pluripo-tency, proliferation, cell differentiation and regulation of cell death. This review presents a brief overview of the Wnt/β-catenin signaling pathway, the regulatory mechanism of this pathway and its role in intestinal homeostasis. Additionally, this review highlights the molecular mechanisms and the histomorphological features of Wnt hyperactivation. Furthermore, the central role of the Wnt signaling pathway in intestinal carcinogenesis as well as its clinical relevance in colorectal carcinoma are discussed.

Targeting autophagy in prostate cancer: preclinical and clinical evidence for therapeutic response

Prostate cancer is a leading cause of death worldwide and new estimates revealed prostate cancer as the leading cause of death in men in 2021. Therefore, new strategies are pertinent in the treatment of this malignant disease. Macroautophagy/autophagy is a “self-degradation” mechanism capable of facilitating the turnover of long-lived and toxic macromolecules and organelles. Recently, attention has been drawn towards the role of autophagy in cancer and how its modulation provides effective cancer therapy. In the present review, we provide a mechanistic discussion of autophagy in prostate cancer. Autophagy can promote/inhibit proliferation and survival of prostate cancer cells. Besides, metastasis of prostate cancer cells is affected (via induction and inhibition) by autophagy. Autophagy can affect the response of prostate cancer cells to therapy such as chemotherapy and radiotherapy, given the close association between autophagy and apoptosis. Increasing evidence has demonstrated that upstream mediators such as AMPK, non-coding RNAs, KLF5, MTOR and others regulate autophagy in prostate cancer. Anti-tumor compounds, for instance phytochemicals, dually inhibit or induce autophagy in prostate cancer therapy. For improving prostate cancer therapy, nanotherapeutics such as chitosan nanoparticles have been developed. With respect to the context-dependent role of autophagy in prostate cancer, genetic tools such as siRNA and CRISPR-Cas9 can be utilized for targeting autophagic genes. Finally, these findings can be translated into preclinical and clinical studies to improve survival and prognosis of prostate cancer patients.

• Prostate cancer is among the leading causes of death in men where targeting autophagy is of importance in treatment;

• Autophagy governs proliferation and metastasis capacity of prostate cancer cells;

• Autophagy modulation is of interest in improving the therapeutic response of prostate cancer cells;

• Molecular pathways, especially involving non-coding RNAs, regulate autophagy in prostate cancer;

• Autophagy possesses both diagnostic and prognostic roles in prostate cancer, with promises for clinical application.

GSK3ß inhibitor CHIR 99021 modulates cerebral organoid development through dose-dependent regulation of apoptosis, proliferation, differentiation and migration

Cerebral organoids generated from human pluripotent stem cells (hiPSCs) are unique in their ability to recapitulate human-specific neurodevelopmental events. They are capable of modeling the human brain and its cell composition, including human-specific progenitor cell types; ordered laminar compartments; and both cell-specific transcriptional signatures and the broader telencephalic transcriptional landscape. The serine/threonine kinase, GSK3β, plays a critical role in neurodevelopment, controlling processes as varied as neurogenesis, morphological changes, polarization, and migration. In the generation of cerebral organoids, inhibition of GSK3β at low doses has been used to increase organoid size and decrease necrotic core. However, little is known of the effects of GSK3β inhibition on organoid development. Here, we demonstrate that while low dose of GSK3β inhibitor CHIR 99021 increases organoid size, higher dose actually reduces organoid size; with the highest dose arresting organoid growth. To examine the mechanisms that may contribute to the phenotypic size differences observed in these treatment groups, we show that low dose of CHIR 99021 increases cell survival, neural progenitor cell proliferation and neuronal migration. A higher dose, however, decreases not only apoptosis but also proliferation, and arrests neural differentiation, enriching the pool of neuroepithelial cells, and decreasing the pools of early neuronal progenitors and neurons. These results reveal new mechanisms of the pleiotropic effects of GSK3β during organoid development, providing essential information for the improvement of organoid production and ultimately shedding light on the mechanisms of embryonic brain development.

SGK1 in Human Cancer: Emerging Roles and Mechanisms

Serum and glucocorticoid-induced protein kinase 1 (SGK1) is a member of the "AGC" subfamily of protein kinases, which shares structural and functional similarities with the AKT family of kinases and displays serine/threonine kinase activity. Aberrant expression of SGK1 has profound cellular consequences and is closely correlated with human cancer. SGK1 is considered a canonical factor affecting the expression and signal transduction of multiple genes involved in the genesis and development of many human cancers. Abnormal expression of SGK1 has been found in tissue and may hopefully become a useful indicator of cancer progression. In addition, SGK1 acts as a prognostic factor for cancer patient survival. This review systematically summarizes and discusses the role of SGK1 as a diagnostic and prognostic biomarker of diverse cancer types; focuses on its essential roles and functions in tumorigenesis, cancer cell proliferation, apoptosis, invasion, metastasis, autophagy, metabolism, and therapy resistance and in the tumor microenvironment; and finally summarizes the current understanding of the regulatory mechanisms of SGK1 at the molecular level. Taken together, this evidence highlights the crucial role of SGK1 in tumorigenesis and cancer progression, revealing why it has emerged as a potential target for cancer therapy.

Transcription factors in colorectal cancer: molecular mechanism and therapeutic implications

Colorectal cancer (CRC) is a major cause of cancer mortality worldwide, however, the molecular mechanisms underlying the pathogenesis of CRC remain largely unclear. Recent studies have revealed crucial roles of transcription factors in CRC development. Transcription factors essential for the regulation of gene expression by interacting with transcription corepressor/enhancer complexes and they orchestrate downstream signal transduction. Deregulation of transcription factors is a frequent occurrence in CRC, and the accompanying drastic changes in gene expression profiles play fundamental roles in multistep process of tumorigenesis, from cellular transformation, disease progression to metastatic disease. Herein, we summarized current and emerging key transcription factors that participate in CRC tumorigenesis, and highlighted their oncogenic or tumor suppressive functions. Moreover, we presented critical transcription factors of CRC, emphasized the major molecular mechanisms underlying their effect on signal cascades associated with tumorigenesis, and summarized of their potential as molecular biomarkers for CRC prognosis therapeutic response, as well as drug targets for CRC treatment. A better understanding of transcription factors involved in the development of CRC will provide new insights into the pathological mechanisms and reveal novel prognostic biomarkers and therapeutic strategies for CRC.

The Enigmatic Role of Serum & Glucocorticoid Inducible Kinase 1 in the Endometrium

The serum- and glucocorticoid-inducible kinase 1 (SGK1) is subject to genetic up-regulation by diverse stimulators including glucocorticoids, mineralocorticoids, dehydration, ischemia, radiation and hyperosmotic shock. To become active, the expressed kinase requires phosphorylation, which is accomplished by PI3K/PDK1 and mTOR dependent signaling. SGK1 enhances the expression/activity of various transport proteins including Na⁺/K⁺-ATPase as well as ion-, glucose-, and amino acid- carriers in the plasma membrane. SGK1 can further up-regulate diverse ion channels, such as Na⁺-, Ca²⁺-, K⁺- and Cl^– channels. SGK1 regulates expression/activity of a wide variety of transcription factors (such as FKHRL1/Foxo3a, β-catenin, NFκB and p53). SGK1 thus contributes to the regulation of transport, glycolysis, angiogenesis, cell survival, immune regulation, cell migration, tissue fibrosis and tissue calcification. In this review we summarized the current findings that SGK1 plays a crucial function in the regulation of endometrial function. Specifically, it plays a dual role in the regulation of endometrial receptivity necessary for implantation and, subsequently in pregnancy maintenance. Furthermore, fetal programming of blood pressure regulation requires maternal SGK1. Underlying mechanisms are, however, still ill-defined and there is a substantial need for additional information to fully understand the role of SGK1 in the orchestration of embryo implantation, embryo survival and fetal programming.

SGK1 mediates the hypotonic protective effect against H2O2-induced apoptosis of rat basilar artery smooth muscle cells by inhibiting the FOXO3a/Bim signaling pathway

Serum- and glucocorticoid-inducible kinease-1 (SGK1) is a serine/threonine kinase regulated by hypotonic stimuli, which is involved in regulation of cell cycle and apoptosis. Our previous study shows that activation of volume-regulated Cl^- channels (VRCCs) protects rat basilar artery smooth muscle cells (BASMCs) against hydrogen peroxide (H₂O₂)-induced apoptosis. In the present study, we investigated whether SGK1 was involved in the protective effect of VRCCs in BASMCs. We showed that hypotonic challenge significantly reduced H₂O₂-induced apoptosis, and increased SGK1 phosphorylation, but did not affect SGK1 protein expression. The protective effect of hypotonic challenge against H₂O₂-induced apoptosis was mediated through inhibiting mitochondria-dependent apoptotic pathway, evidenced by increased Bcl-2/Bax ratio, stabilizing mitochondrial membrane potential (MMP), decreased cytochrome c release from the mitochondria to the cytoplasm, and inhibition of the activation of caspase-9 and caspase-3. These protective effects of hypotonic challenge against H₂O₂-induced apoptosis was diminished and enhanced, respectively, by SGK1 knockdown and overexpression. We further revealed that SGK1 activation significantly increased forkhead box O3a (FOXO3a) phosphorylation, and then inhibited the translocation of FOXO3a into nucleus and the subsequent expression of Bcl-2 interacting mediator of cell death (Bim). In conclusion, SGK1 mediates the protective effect of VRCCs against H₂O₂-induced apoptosis in BASMCs via inhibiting FOXO3a/Bim signaling pathway. Our results provide compelling evidences that SGK1 is a critical link between VRCCs and apoptosis, and shed a new light on the treatment of vascular apoptosis-associated diseases, such as vascular remodeling, angiogenesis, and atherosclerosis.

Wnt Signaling Protects against Paclitaxel-Induced Spiral Ganglion Neuron Damage in the Mouse Cochlea In Vitro

It has been reported that paclitaxel administration could cause sensorineural hearing loss, and Wnt activation is important for the development and cell protection of mouse cochlea. However, the effect of Wnt signaling in spiral ganglion neurons (SGNs) damage induced by paclitaxel has not yet been elucidated. In this study, we explored the effect of paclitaxel on SGNs in the mouse cochlea and the neuroprotective effects of Wnt signaling pathway against paclitaxel-induced SGN damage by using Wnt agonist/antagonists in vitro. We first found that paclitaxel treatment resulted in a degenerative change and reduction of cell numbers in SGNs and induced caspase-mediated apoptosis in SGNs. The expression levels of β-catenin and C-myc were increased, thus indicating Wnt signaling was activated in SGNs after paclitaxel treatment. The activation of Wnt signaling pathway protected against SGN loss after exposure to paclitaxel, whereas the suppression of Wnt signaling in SGNs made them more vulnerable to paclitaxel treatment. We also showed that activation of Wnt signaling in SGNs inhibited caspase-mediated apoptosis. Our findings demonstrated that Wnt signaling had an important role in protecting SGNs against paclitaxel-induced damage and thus might be an effective therapeutic target for the prevention of paclitaxel-induced SGN death.

Radiation-induced glucocorticoid receptor promotes CD44+ prostate cancer stem cell growth through activation of SGK1-Wnt/β-catenin signaling

We observed cancer stem cell (CSC) population increase in radioresistant LNCaP (LNCaPR18) and C4-2 (C4-2R26) prostate cancer (PCa) cells compared with respective parental cells. Since the CD44 level increase was most significant in radioresistant PCa cells compared with parental cells among CSC markers tested, we isolated the CD44+ population from LNCaP/LNCaPR18 and C4-2/C4-2R26 cell sets via the immunomagnetic separation method and used them as CSC sources. We detected lower AR level, but higher glucocorticoid receptor (GR) level in CD44+ CSCs than CD44- non-CSCs. Higher GR level in CD44+ CSCs than CD44- cells was also detected when cells were isolated from mouse tumor tissues of LNCaPR18 cell and C4-2R26 cell-derived human xenografts and grown in culture. We then found blocking the GR signaling by adding the anti-GR agent mifepristone into the cell culture inhibited the CD44+ CSC growth while the addition of the anti-AR agent enzalutamide enhanced the CSC growth. In xenograft mouse studies in which tumors were developed from the injection of CD44+ CSCs of LNCaPR18 or C4-2R26 cell lines, retarded tumor growth in mifepristone-injected mice was observed compared with vehicle-treated mice. We next discovered the GR regulation of Wnt/β-catenin signaling pathway. We further found that the serum/glucocorticoid regulated kinase 1 (SGK1) is the GR downstream molecule that mediates Wnt/β-catenin signaling activation. Therefore, inhibition of either SGK1 or Wnt/β-catenin signaling impaired the in vitro CD44+ CSC growth. From these results, we suggest that blocking GR signaling or its downstream SGK1-Wnt/β-catenin signaling axis may suppress the radiation-induced CSC increase in PCa. KEY MESSAGES: Higher CSC population exists in radioresistant PCa cells than parental cells. Higher GR levels (and lower AR level) in CD44+ CSCs than CD44- non-CSCs. Use of anti-GR agent blocked the growth of CD44+ CSCs in in vitro/in vivo tests. GR downstream SGK1-Wnt/β-catenin signaling axis mediates the CSC increase. Targeting this signaling axis may enhance the radiotherapy efficacy in treating PCa.

Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the sirtuin 3-Forkhead box O3a axis in human small-cell lung cancer

Background

Small‐cell lung cancer (SCLC), a malignant tumor, is usually widely metastatic when diagnosed. The lack of important therapeutic clinical advances makes it difficult to treat. Previous studies showed that Adjudin had anticancer effects in many other human cancers, and it was synergetic with cisplatin in non‐small cell lung cancer. However, the mechanism on SCLC was unclear.

Methods

We investigated the potential mechanism and effect of Adjudin on SCLC both in vitro and in vivo.

Results

An SCLC xenograft model showed that Adjudin inhibited tumor growth and was significantly synergetic with paclitaxel (in vitro as well). Cell Counting Kit‐8 assays, flow cytometric analysis and western blotting showed that Adjudin effectively suppressed SCLC cell proliferation by inducing S phase arrest and caspase‐dependent apoptosis. Moreover, Transwell and scratch assays showed that Adjudin also effectively inhibited migration and invasion. Furthermore, Adjudin activated the sirtuin 3 (SIRT3)–Forkhead box O3a (FOXO3a) pathway. Downregulating SIRT3 or FOXO3a significantly attenuated Adjudin‐induced anticancer effects. Furthermore, higher expression of SIRT3 and FOXO3a were positively correlated, and both were associated with longer survival in lung cancer patients.

Conclusion

Overall, the present study is the first to show that Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the SIRT3–FOXO3a axis in SCLC; thus, Adjudin has great potential to be an anticancer agent.

The forkhead-box family of transcription factors: key molecular players in colorectal cancer pathogenesis

Colorectal cancer (CRC) is the third most commonly occurring cancer worldwide and the fourth most frequent cause of death having an oncological origin. It has been found that transcription factors (TF) dysregulation, leading to the significant expression modifications of genes, is a widely distributed phenomenon regarding human malignant neoplasias. These changes are key determinants regarding tumour’s behaviour as they contribute to cell differentiation/proliferation, migration and metastasis, as well as resistance to chemotherapeutic agents. The forkhead box (FOX) transcription factor family consists of an evolutionarily conserved group of transcriptional regulators engaged in numerous functions during development and adult life. Their dysfunction has been associated with human diseases. Several FOX gene subgroup transcriptional disturbances, affecting numerous complex molecular cascades, have been linked to a wide range of cancer types highlighting their potential usefulness as molecular biomarkers. At least 14 FOX subgroups have been related to CRC pathogenesis, thereby underlining their role for diagnosis, prognosis and treatment purposes.

This manuscript aims to provide, for the first time, a comprehensive review of FOX genes’ roles during CRC pathogenesis. The molecular and functional characteristics of most relevant FOX molecules (FOXO, FOXM1, FOXP3) have been described within the context of CRC biology, including their usefulness regarding diagnosis and prognosis. Potential CRC therapeutics (including genome-editing approaches) involving FOX regulation have also been included. Taken together, the information provided here should enable a better understanding of FOX genes’ function in CRC pathogenesis for basic science researchers and clinicians.

Serum- and glucocorticoid-inducible kinase 1 and the response to cell stress

Expression of the serum- and glucocorticoid-inducible kinase 1 (SGK1) is up-regulated by several types of cell stress, such as ischemia, radiation and hyperosmotic shock. The SGK1 protein is activated by a signaling cascade involving phosphatidylinositide-3-kinase (PI3K), 3-phosphoinositide-dependent kinase 1 (PDK1) and mammalian target of rapamycin (mTOR). SGK1 up-regulates Na⁺/K⁺-ATPase, a variety of carriers including Na⁺-,K⁺-,2Cl⁻- cotransporter (NKCC), NaCl cotransporter (NCC), Na⁺/H⁺ exchangers, diverse amino acid transporters and several glucose carriers such as Na⁺-coupled glucose transporter SGLT1. SGK1 further up-regulates a large number of ion channels including epithelial Na⁺ channel ENaC, voltagegated Na⁺ channel SCN5A, Ca²⁺ release-activated Ca²⁺ channel (ORAI1) with its stimulator STIM1, epithelial Ca²⁺ channels TRPV5 and TRPV6 and diverse K⁺ channels. Furthermore, SGK1 influences transcription factors such as nuclear factor kappa-B (NF-κB), p53 tumor suppressor protein, cAMP responsive element-binding protein (CREB), activator protein-1 (AP-1) and forkhead box O3 protein (FOXO3a). Thus, SGK1 supports cellular glucose uptake and glycolysis, angiogenesis, cell survival, cell migration, and wound healing. Presumably as last line of defense against tissue injury, SGK1 fosters tissue fibrosis and tissue calcification replacing energy consuming cells.

Overexpression of FOXS1 in gastric cancer cell lines inhibits proliferation, metastasis, and epithelial-mesenchymal transition of tumor through downregulating wnt/β-catenin pathway

BACKGROUND

Expression of forkhead box (FOX) superfamily members has been shown to be decreased in cancer, which was linked to poor prognosis of patients. The aim of this study was to investigate the expression of a new FOX superfamily member, FOXS1, in gastric cancer, and the influence of FOXS1 overexpression on the tumorigenesis of gastric cancer cells. The underlying molecular mechanism was also investigated.

MATERIALS AND METHODS

FOXS1 expression levels were firstly measured in 15 paired gastric cancer and peritumor tissue using quantitative polymerase chain reaction or immunohistochemistry. Secondly, FOXS1 overexpression models were established in two gastric cancer cell lines (SNU-216 and AGS) and FOXS1 knockdown model was established in SNU-638 gastric cancer cell line. Markers for cell proliferation, metastasis, cell cycle status, and wnt/β-catenin pathway were evaluated. Influence of FOXS1 overexpression on tumorigenesis was further evaluated in xenograft model.

RESULTS

Expression of FOXS1 was significantly decreased in gastric cancer tissue in both messenger RNA and protein levels, compared with peritumor tissue. Our results showed that compared to cell lines transfected with negative control, gastric cancer cell lines with FOXS1 overexpression showed suppressed cell proliferation, metastasis, and increased ratio of G0/G1 phase. Xenograft model also showed suppressed tumor growth in FOXS1 overexpression group. Epithelial-mesenchymal transition was also inhibited when FOXS1 was overexpressed, which was indicated by an increase of E-cadherin expression and decrease in vimentin expression. Further investigation showed that expression of β-catenin was decreased, together with decreased expression in downstream signaling factors, c-Myc and cyclin-D1 in FOXS1 overexpression cell lines. On the other hand, knockdown of FOXS1 showed opposite trends in the changes of those markers for cell proliferation, metastasis, cell cycle status, and wnt/β-catenin pathway, compared with FOXS1 overexpression.

CONCLUSION

In conclusion, the present study showed that FOXS1 expression is downregulated in most GC cases in our cohort, and this loss of expression may promote cell proliferation and metastasis through upregulation of wnt/β-catenin pathway.

Activated β-catenin in Foxp3+ regulatory T cells links inflammatory environments to autoimmunity

Foxp3⁺ regulatory T cells (T_reg cells) are the central component of peripheral immune tolerance. While dysregulated T_reg cytokine signature has been observed in autoimmune diseases, the regulatory mechanisms underlying pro- and anti-inflammatory cytokine production are elusive. Here, we identify imbalance between IFN-γ and IL-10 as a shared T_reg signature, present in patients with multiple sclerosis (MS) and under high salt conditions. RNA-sequencing analysis on human T_reg subpopulations reveals β-catenin as a key regulator of IFN-γ and IL-10 expression. The activated β-catenin signature is enriched in human IFN-γ⁺ T_reg cells, which is confirmed in vivo with T_reg specific β-catenin-stabilized mice exhibiting lethal autoimmunity with a dysfunctional T_reg phenotype. Moreover, we identify prostaglandin E receptor 2 (PTGER2) as a regulator for IFN-γ and IL-10 production under high salt environment, with skewed activation of the β-catenin-SGK1-Foxo axis. Our findings reveal a novel PTGER2-β-catenin loop in T_reg cells linking environmental high salt conditions to autoimmunity.

Further information on experimental design is available in the Nature Research Reporting Summary linked to this article.

To die or not to die SGK1-sensitive ORAI/STIM in cell survival

The pore forming Ca²⁺ release activated Ca²⁺ channel (CRAC) isoforms ORAI1-3 and their regulators STIM1,2 accomplish store operated Ca²⁺ entry (SOCE). Activation of SOCE may lead to cytosolic Ca²⁺ oscillations, which in turn support cell proliferation and cell survival. ORAI/STIM and thus SOCE are upregulated by the serum and glucocorticoid inducible kinase SGK1, a kinase under powerful genomic regulation and activated by phosphorylation via the phosphoinositol-3-phosphate pathway. SGK1 enhances ORAI1 abundance partially by phosphorylation of Nedd4-2, an ubiquitin ligase priming the channel protein for degradation. The SGK1-phosphorylated Nedd4-2 binds to the protein 14-3-3 and is thus unable to ubiquinate ORAI1. SGK1 further increases the ORAI1 and STIM1 protein abundance by activating nuclear factor kappa B (NF-κB), a transcription factor upregulating the expression of STIM1 and ORAI1. SGK1-sensitive upregulation of ORAI/STIM and thus SOCE is triggered by a wide variety of hormones and growth factors, as well as several cell stressors including ischemia, radiation, and cell shrinkage. SGK1 dependent upregulation of ORAI/STIM confers survival of tumor cells and thus impacts on growth and therapy resistance of cancer. On the other hand, SGK1-dependent upregulation of ORAI1 and STIM1 may support survival of neurons and impairment of SGK1-dependent ORAI/STIM activity may foster neurodegeneration. Clearly, further experimental effort is needed to define the mechanisms linking SGK1-dependent upregulation of ORAI1 and STIM1 to cell survival and to define the impact of SGK1-dependent upregulation of ORAI1 and STIM1 on malignancy and neurodegenerative disease.

SGK1 inhibition-induced autophagy impairs prostate cancer metastasis by reversing EMT

Background

Despite SGK1 has been identified and characterized as a tumor-promoting gene, the functions and underlying mechanisms of SGK1 involved in metastasis regulation have not yet been investigated in cancer.

Methods

We investigated the cellular responses to GSK650394 treatment and SGK1 silencing (or overexpression) in human prostate cancer (PCa) cell lines and PC3 xenografts by wound healing assay, migration and invasion assay, western blotting, immunofluorescence and immunohistochemistry.

Results

In the present study, we found that SGK1 expression positively correlates with human prostate cancer (PCa) progression and metastasis. We show that SGK1 inhibition significantly attenuates EMT and metastasis both in vitro and in vivo, whereas overexpression of SGK1 dramaticlly promoted the invasion and migration of PCa cells. Our further results suggest that SGK1 inhibition induced antimetastatic effects, at least partially via autophagy-mediated repression of EMT through the downregulation of Snail. Moreover, ectopic expression of SGK1 obviously attenuated the GSK650394-induced autophagy and antimetastatic effects. What’s more, dual inhibition of mTOR and SGK1 enhances autophagy and leads to synergistic antimetastatic effects on PCa cells.

Conclusions

Taken together, this study unveils a novel mechanism in which SGK1 functions as a tumor metastasis-promoting gene and highlights how co-targeting SGK1 and autophagy restrains cancer progression due to the amplified antimetastatic effects.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0743-1) contains supplementary material, which is available to authorized users.

SIRT3 inhibits prostate cancer metastasis through regulation of FOXO3A by suppressing Wnt/β-catenin pathway

SIRT3, a mitochondrial NAD⁺-dependent deacetylase, has been reported to restrain prostate cancer growth both in vitro and in vivo, however, its role in metastatic prostate cancer has not been revealed. In this study, we reported that SIRT3 inhibited the epithelial-mesenchymal transition (EMT) and migration of prostatic cancer cells in vitro and their metastasis in vivo. Consistently, based on analyses of tissue microarray and microarray datasets, lower SIRT3 expression level was correlated with higher prostate cancer Gleason scores, and SIRT3 expression were significantly decreased in metastatic tissues compared with prostate tumor tissues. Mechanistically, SIRT3 promoted FOXO3A expression by attenuating Wnt/β-catenin pathway, thereby inhibiting EMT and migration of prostate cancer cells. Indeed, SIRT3's inhibitory effect on EMT and migration of prostate cancer cells can be rescued after applying Wnt/β-catenin pathway activator LiCl, or boosted by wnt inhibitor XAV939. Together, this study revealed a novel mechanism for prostate cancer metastasis that involves SIRT3/ Wnt/β-catenin/ FOXO3A signaling to modulate EMT and cell migration.

miR-182-5p promotes hepatocellular carcinoma progression by repressing FOXO3a

BACKGROUND

High frequency of recurrence is the major cause of the poor outcomes for patients with hepatocellular carcinoma (HCC). microRNA (miR)-182-5p emerged as a high-priority miRNA in HCC and was found to be related to HCC metastasis. Whether the expression of miR-182-5p in tumor tissue correlated with early recurrence in HCC patients underwent curative surgery was unknown.

METHODS

Real-time PCR (RT-PCR) and in situ hybridization (ISH) were conducted to assess the expression of miR-182-5p in HCC cells and tissues. Cell Counting Kit-8 (CCK-8), transwell assays were performed to detected cells proliferation and migration ability. Flow cytometry assays were used to detect cell apoptosis rate, and xenograft model was employed to study miR-182-5p in HCC growth and lung metastasis. The target of miR-182-5p was validated with a dual-luciferase reporter assay and western blotting. Immunohistochemistry, immumoblotting, and immunoprecipitation were performed to test relative protein expression.

RESULTS

We showed that high expression of miR-182-5p in tumor tissues correlated with poor prognosis as well as early recurrence in HCC patients underwent curative surgery. miR-182-5p enhanced motility and invasive ability of HCC cells both in vitro and in vivo. miR-182-5p directly targets 3'-UTR of FOXO3a and repressed FOXO3a expression, activating AKT/FOXO3a pathway to promote HCC proliferation. Notably, miR-182-5p activated Wnt/β-catenin signaling by inhibiting the degradation of β-catenin and enhancing the interaction between β-catenin and TCF4 which was mediated by repressed FOXO3a.

CONCLUSIONS

Consistently, miR-182-5p can be a potential predictor of early recurrence for HCC patients underwent curative surgery, and FOXO3a plays a key mediator in miR-182-5p induced HCC progression.

SGK1 inhibition induces autophagy-dependent apoptosis via the mTOR-Foxo3a pathway

BACKGROUND

Although inhibition of SGK1 has been shown to delay cancer progression, the underlying mechanisms have not yet been elucidated.

METHODS

We investigated the cellular responses to GSK650394 treatment and SGK1 silencing (or overexpression) in human prostate cancer (PCa) cell lines and PC3 xenografts by flow cytometry, western blotting, immunofluorescence, transmission electron microscopy and immunohistochemistry.

RESULTS

In the present study, we demonstrated that SGK1 inhibition, mediated by either GSK650394 or SGK1 shRNA, induced G2/M arrest, apoptosis and autophagy. Furthermore, 3MA-mediated autophagy inhibition attenuated SGK1 inhibition-induced apoptosis, suggesting that induction of autophagy precedes apoptosis. Moreover, ectopic expression of SGK1 significantly attenuated the GSK650394-induced effects. Suppression of mTOR and Foxo3a phosphorylation is critical for blockade of SGK1-induced autophagy and apoptosis, at least partially via pFoxo3a (S253)-LC3 and pFoxo3a (S253)-p27 interactions. Dual inhibition of mTOR and SGK1 enhances autophagy activation and leads to synergistic cytocidal effects in PCa cells.

CONCLUSIONS

In summary, our findings show that SGK1 inhibition exhibits significant antitumour effects against PCa in vitro and in vivo. This study uncovered a novel mechanism of SGK1 inhibition in PCa, which is mediated, at least in part, by inducing autophagy-dependent apoptosis via the mTOR-Foxo3a pathway.

Transcriptomic signatures for ovulation in vertebrates

The central roles of luteinizing hormone (LH), progestin and their receptors for initiating ovulation have been well established. However, signaling pathways and downstream targets such as proteases that are essential for the rupture of follicular cells are still unclear. Recently, we found anovulation in nuclear progestin receptor (Pgr) knockout (Pgr-KO) zebrafish, which offers a new model for examining genes and pathways that are important for ovulation and fertility. In this study, we examined expression of all transcripts using RNA-Seq in preovulatory follicular cells collected following the final oocyte maturation, but prior to ovulation, from wild-type (WT) or Pgr-KO fish. Differential expression analysis revealed 3567 genes significantly differentially expressed between WT and Pgr-KO fish (fold change⩾2, p<0.05). Among those, 1543 gene transcripts were significantly more expressed, while 2024 genes were significantly less expressed, in WT than those in Pgr-KO. We then retrieved and compared transcriptional data from online databases and further identified 661 conserved genes in fish, mice, and humans that showed similar levels of high (283 genes) or low (387) expression in animals that were ovulating compared to those with no ovulation. For the first time, ovulatory genes and their involved biological processes and pathways were also visualized using Enrichment Map and Cytoscape. Intriguingly, enrichment analysis indicated that the genes with higher expression were involved in multiple ovulatory pathways and processes such as inflammatory response, angiogenesis, cytokine production, cell migration, chemotaxis, MAPK, focal adhesion, and cytoskeleton reorganization. In contrast, the genes with lower expression were mainly involved in DNA replication, DNA repair, DNA methylation, RNA processing, telomere maintenance, spindle assembling, nuclear acid transport, catabolic processes, and nuclear and cell division. Our results indicate that a large set of genes (>3000) is differentially regulated in the follicular cells in zebrafish prior to ovulation, terminating programs such as growth and proliferation, and beginning processes including the inflammatory response and apoptosis. Further studies are required to establish relationships among these genes and an ovulatory circuit in the zebrafish model.

The SGK1 inhibitor SI113 induces autophagy, apoptosis, and endoplasmic reticulum stress in endometrial cancer cells

Endometrial cancer is often characterized by PI3K/AKT pathway deregulation. Recently it has been suggested that SGK1, a serine/threonine protein kinase that shares structural and functional similarities with the AKT family, might play a role in cancer, since its expression and/or activity has been found to be deregulated in different human tumors. However, the role of SGK1 in endometrial cancer has been poorly investigated. Here, we show that SGK1 expression is increased in tissue specimens from neoplastic endometrium. The SGK1 inhibitor SI113 induced a significant reduction of endometrial cancer cells viability, measured by the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. This effect was associated to the increase of autophagy, as revealed by the increase of the markers LC3B-II and beclin I, detected by both immunofluorescence and western blot analysis. SI113 treatment caused also apoptosis of endometrial cancer cells, evidenced by the cleavage of the apoptotic markers PARP and Caspase-9. Intriguingly, these effects were associated to the induction of endoplasmic reticulum stress markers GRP78 and CHOP evaluated by both Real-Time RT-PCR and Western Blot analysis. Increased expression of SGK1 in endometrial cancer tissues suggest a role for SGK1 in this type of cancer, as reported for other malignancies. Moreover, the efficacy of SI113 in affecting endometrial cancer cells viability, possibly via endoplasmic reticulum stress activation, identifies SGK1 as an attractive molecular target for new tailored therapeutic intervention for the treatment of endometrial cancer.

Expression of serum- and glucocorticoid-regulated kinase 1 and its association with clinicopathological factors and the survival of patients with adenocarcinoma of the esophagogastric junction

While the aberrant expression and the controversial results of serum- and glucocorticoid-regulated kinase (SGK1) have been reported in a number of malignancies, the expression of SGK1 and its possible association with the progression of adenocarcinoma in the esophagogastric junction (AEG) remain to be elucidated. To the best of our knowledge, the expression and localization of SGK1 was examined for the first time in the present study in cancerous and adjacent tissue from 60 patients with AEG, and compared with 20 healthy mucosa control tissue samples. Furthermore, the association between SGK1 expression and the clinicopathological characteristics, and prognosis of patients with AEG was statistically analyzed. The expression level of SGK1 was identified to be significantly higher (P<0.0001) in the cancerous AEG tissue samples (65%) compared with that of the adjacent tissue (31.7%) and healthy control (10%) samples. Enhanced SGK1 was primarily localized in the cytoplasm and the expression level of SGK1 was associated with the differentiation (P=0.045) and lymph node metastasis (P=0.006) of AEG. Notably, increased expression of SGK1 was demonstrated to be significantly correlated with poor overall survival (P=0.027). The results of the present study revealed the expression profile of SGK1 in AEG and demonstrated that SGK1 expression in cancerous tissue is an indicator for the progression of AEG. Thus, SGK1 may be a potential molecular marker for the diagnosis, interference therapy and prognosis of AEG.

Salt, aldosterone and extrarenal Na+ - sensitive responses in pregnancy

Outside of pregnancy excessive salt consumption is known to be harmful being linked to increased blood pressure and cardiovascular disease. However, pregnancy represents a major change to a woman's physiology resulting in an intimate adaptation to environmental conditions. It is now becoming apparent that salt is essential for a number of these changes during pregnancy including haematological, cardiac adaptations as well as directly influencing placental development and the uteroplacental immune environment. The present review discusses the important role that salt has during normal pregnancy and evidence will also be presented to show how the placenta may act as a salt sensing organ temporarily, yet substantially regulating maternal blood pressure.

•

The placenta may function as an extrarenal regulator of maternal blood pressure.

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Na⁺handling in pregnancy is completely different to the non-pregnant situation.

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Na⁺may actually lower blood pressure in pregnancy affected with pre-eclampsia.

•

Aldosterone is an important regulator of placental and fetal development.

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Na⁺ may compensate for aldosterone deficiency in pregnancy.

GSK3ß-dependent dysregulation of neurodevelopment in SPG11-patient induced pluripotent stem cell model

Objective

Mutations in the spastic paraplegia gene 11 (SPG11), encoding spatacsin, cause the most frequent form of autosomal‐recessive complex hereditary spastic paraplegia (HSP) and juvenile‐onset amyotrophic lateral sclerosis (ALS5). When SPG11 is mutated, patients frequently present with spastic paraparesis, a thin corpus callosum, and cognitive impairment. We previously delineated a neurodegenerative phenotype in neurons of these patients. In the current study, we recapitulated early developmental phenotypes of SPG11 and outlined their cellular and molecular mechanisms in patient‐specific induced pluripotent stem cell (iPSC)‐derived cortical neural progenitor cells (NPCs).

Methods

We generated and characterized iPSC‐derived NPCs and neurons from 3 SPG11 patients and 2 age‐matched controls.

Results

Gene expression profiling of SPG11‐NPCs revealed widespread transcriptional alterations in neurodevelopmental pathways. These include changes in cell‐cycle, neurogenesis, cortical development pathways, in addition to autophagic deficits. More important, the GSK3ß‐signaling pathway was found to be dysregulated in SPG11‐NPCs. Impaired proliferation of SPG11‐NPCs resulted in a significant diminution in the number of neural cells. The decrease in mitotically active SPG11‐NPCs was rescued by GSK3 modulation.

Interpretation

This iPSC‐derived NPC model provides the first evidence for an early neurodevelopmental phenotype in SPG11, with GSK3ß as a potential novel target to reverse the disease phenotype. Ann Neurol 2016;79:826–840

Wnt activation protects against neomycin-induced hair cell damage in the mouse cochlea

Recent studies have reported the role of Wnt/β-catenin signaling in hair cell (HC) development, regeneration, and differentiation in the mouse cochlea; however, the role of Wnt/β-catenin signaling in HC protection remains unknown. In this study, we took advantage of transgenic mice to specifically knockout or overactivate the canonical Wnt signaling mediator β-catenin in HCs, which allowed us to investigate the role of Wnt/β-catenin signaling in protecting HCs against neomycin-induced damage. We first showed that loss of β-catenin in HCs made them more vulnerable to neomycin-induced injury, while constitutive activation of β-catenin in HCs reduced HC loss both in vivo and in vitro. We then showed that loss of β-catenin in HCs increased caspase-mediated apoptosis induced by neomycin injury, while β-catenin overexpression inhibited caspase-mediated apoptosis. Finally, we demonstrated that loss of β-catenin in HCs led to increased expression of forkhead box O3 transcription factor (Foxo3) and Bim along with decreased expression of antioxidant enzymes; thus, there were increased levels of reactive oxygen species (ROS) after neomycin treatment that might be responsible for the increased aminoglycoside sensitivity of HCs. In contrast, β-catenin overexpression reduced Foxo3 and Bim expression and ROS levels, suggesting that β-catenin is protective against neomycin-induced HC loss. Our findings demonstrate that Wnt/β-catenin signaling has an important role in protecting HCs against neomycin-induced HC loss and thus might be a new therapeutic target for the prevention of HC death.

SGK-1 protects kidney cells against apoptosis induced by ceramide and TNF-α

Ceramide regulates several different cellular responses including mechanisms leading to apoptosis. Serum- and glucocorticoid-inducible protein kinase (SGK)-1 is a serine threonine kinase, which activates survival pathways in response to stress stimuli. Recently, we demonstrated an anti-apoptotic role of SGK-1 in human umbilical endothelial cells treated with high glucose. In the present study, since ceramide induces apoptosis by multiple mechanisms in diabetes and its complication such as nephropathy, we aimed to investigate whether SGK-1 may protect even against apoptosis induced by ceramide in kidney cells. Human embryonic kidney (HEK)-293 cells stable transfected with SGK-1 wild type (SGK-1wt) and its dominant negative gene (SGK-1dn) have been used in this study. Apoptotic stimuli were induced by C₂-ceramide and TNF-α to increase endogenous synthesis of ceramide. Upon activation with these stimuli, SGK-1wt transfected cells have a statistically significant reduction of apoptosis compared with SGK-1dn cells (P<0.001). This protection was dependent on activation of caspase-3 and Poly-ADP-ribose-polymerase-1 (PARP-1) cleavage. SGK-1 and AKT-1 two highly homologous kinases differently reacted to ceramide treatment, since SGK-1 increases in response to apoptotic stimulus while AKT-1 decreases. This enhancement of SGK-1 was dependent on p38-mitogen-activated-protein kinases (p38MAPK), cyclic-adenosine-monophosphate/protein kinase A (cAMP/PKA) and phosphoinositide-3-kinase (PI3K) pathways. Especially, by using selective LY294002 inhibitor, we demonstrated that the most involved pathway in the SGK-1 mediated process of protection was PI3K. Treatment with inhibitor of SGK-1 (GSK650394) significantly enhanced TNF-α-dependent apoptosis in HEK-293 cells overexpressing SGK-1wt. Caspase-3, -8 and -9 selective inhibitors confirmed that SGK-1 reduced the activation of caspase-dependent apoptosis, probably by both intrinsic and extrinsic pathways. In conclusion, we demonstrated that in kidney cells, overexpression of SGK-1 is protective against ceramide-induced apoptosis and the role of SGK-1 can be potentially explored as a therapeutic target in conditions like diabetes, where ceramide levels are increased.

Chromatin-Remodeling-Factor ARID1B Represses Wnt/β-Catenin Signaling

The link of chromatin remodeling to both neurodevelopment and cancer has recently been highlighted by the identification of mutations affecting BAF chromatin-remodeling components, such as ARID1B, in individuals with intellectual disability and cancer. However, the underlying molecular mechanism(s) remains unknown. Here, we show that ARID1B is a repressor of Wnt/β-catenin signaling. Through whole-transcriptome analysis, we find that in individuals with intellectual disability and ARID1B loss-of-function mutations, Wnt/β-catenin target genes are upregulated. Using cellular models of low and high Wnt/β-catenin activity, we demonstrate that knockdown of ARID1B activates Wnt/β-catenin target genes and Wnt/β-catenin-dependent transcriptional reporters in a β-catenin-dependent manner. Reciprocally, forced expression of ARID1B inhibits Wnt/β-catenin signaling downstream of the β-catenin destruction complex. Both endogenous and exogenous ARID1B associate with β-catenin and repress Wnt/β-catenin-mediated transcription through the BAF core subunit BRG1. Accordingly, mutations in ARID1B leading to partial or complete deletion of its BRG1-binding domain, as is often observed in intellectual disability and cancers, compromise association with β-catenin, and the resultant ARID1B mutant proteins fail to suppress Wnt/β-catenin signaling. Finally, knockdown of ARID1B in mouse neuroblastoma cells leads to neurite outgrowth through β-catenin. The data suggest that aberrations in chromatin-remodeling factors, such as ARID1B, might contribute to neurodevelopmental abnormalities and cancer through deregulation of developmental and oncogenic pathways, such as the Wnt/β-catenin signaling pathway.

Redox regulation of FoxO transcription factors

Transcription factors of the forkhead box, class O (FoxO) family are important regulators of the cellular stress response and promote the cellular antioxidant defense. On one hand, FoxOs stimulate the transcription of genes coding for antioxidant proteins located in different subcellular compartments, such as in mitochondria (i.e. superoxide dismutase-2, peroxiredoxins 3 and 5) and peroxisomes (catalase), as well as for antioxidant proteins found extracellularly in plasma (e.g., selenoprotein P and ceruloplasmin). On the other hand, reactive oxygen species (ROS) as well as other stressful stimuli that elicit the formation of ROS, may modulate FoxO activity at multiple levels, including posttranslational modifications of FoxOs (such as phosphorylation and acetylation), interaction with coregulators, alterations in FoxO subcellular localization, protein synthesis and stability. Moreover, transcriptional and posttranscriptional control of the expression of genes coding for FoxOs is sensitive to ROS. Here, we review these aspects of FoxO biology focusing on redox regulation of FoxO signaling, and with emphasis on the interplay between ROS and FoxOs under various physiological and pathophysiological conditions. Of particular interest are the dual role played by FoxOs in cancer development and their key role in whole body nutrient homeostasis, modulating metabolic adaptations and/or disturbances in response to low vs. high nutrient intake. Examples discussed here include calorie restriction and starvation as well as adipogenesis, obesity and type 2 diabetes.

Restoration of Wnt/β-catenin signaling attenuates alcoholic liver disease progression in a rat model

BACKGROUND & AIMS

Alcoholic liver disease (ALD) is characterized by the development of fatty liver, alcoholic hepatitis, fibrosis and cirrhosis. However, the underlying mechanism(s) associated with progression remains elusive. Pro-inflammatory cytokines have been implicated in ALD progression due to pro-apoptotic effects on hepatocytes. Wnt/β-catenin signaling recently has been shown to promote inflammation and apoptosis, suggesting that activation of this signaling pathway may modulate ALD progression. The current study was designed to test whether pharmacological activation of Wnt/β-catenin signaling altered ALD development and progression in a rat model.

METHODS

Adult male Long Evans rats were fed with isocaloric liquid diets containing 0% or 37% ethanol for 8 weeks, and also treated with Wnt agonist during the last 3 weeks of the feeding regimen. Liver and blood samples were subjected to histology, TUNEL assay, immunoblot analysis, real-time quantitative PCR, and alanine transaminase (ALT) assay.

RESULTS

Wnt/β-catenin signaling was negatively correlated with Foxo3A expression and reduced steatosis, cellular injury and apoptosis in ALD rats. Mutation experiments demonstrated that Foxo3A was critical for modulating these effects. Activation of Wnt/β-catenin signaling suppressed Foxo3A-induced apoptosis through upregulation of serum/glucocorticoid regulated kinase 1 (SGK1). Moreover, pharmacological restoration of Wnt/β-catenin signaling reduced ALD progression in vivo.

CONCLUSIONS

Wnt/β-catenin signaling plays a protective role in ALD progression via antagonizing Foxo3A-induced apoptosis, and activation of the Wnt/β-catenin signaling cascade attenuates ALD progression.

SGK1 inhibits cellular apoptosis and promotes proliferation via the MEK/ERK/p53 pathway in colitis

AIM: To investigate the role of serum-and-glucocorticoid-inducible-kinase-1 (SGK1) in colitis and its potential pathological mechanisms.

METHODS: SGK1 expression in mucosal biopsies from patients with active Crohn’s disease (CD) and normal controls was detected by immunohistochemistry. We established an acute colitis model in mice induced by 2,4,6-trinitrobenzene sulfonicacid, and demonstrated the presence of colitis using the disease activity index, the histologic activity index and hematoxylin and eosin staining. The cellular events and potential mechanisms were implemented with small interference RNA and an inhibitor of signaling molecule (i.e., U0126) in intestinal epithelial cells (IECs). The interaction between SGK1 and the signaling molecule was assessed by co-immunoprecipitation.

RESULTS: SGK1 expression was significantly increased in the inflamed epithelia of patients with active CD and TNBS-induced colitis model (0.58 ± 0.055 vs 0.85 ± 0.06, P < 0.01). At the cellular level, silencing of SGK1 by small interference RNA (siSGK1) significantly inhibited the phosphorylation of mitogen-activated protein kinase kinase 1 (MEK1) and the downstream molecule extracellular signal regulated protein kinase (ERK) 1/2, which induced the upregulation of p53 and Bcl-2-associated X protein, mediating the subsequent cellular apoptosis and proliferation in IECs. Cells treated with MEK1 inhibitor (i.e., U0126) before siSGK1 transfection showed a reversal of the siSGK1-induced cellular apoptosis.

CONCLUSION: Our data suggested that SGK1 may protect IECs in colitis from tumor necrosis factor-α-induced apoptosis partly by triggering MEK/ERK activation.

Enhanced Orai1 and STIM1 expression as well as store operated Ca2+ entry in therapy resistant ovary carcinoma cells

Mechanisms underlying therapy resistance of tumor cells include protein kinase Akt. Putative Akt targets include store-operated Ca²⁺-entry (SOCE) accomplished by pore forming ion channel unit Orai1 and its regulator STIM1. We explored whether therapy resistant (A2780cis) differ from therapy sensitive (A2780) ovary carcinoma cells in Akt, Orai1, and STIM1 expression, Ca²⁺-signaling and cell survival following cisplatin (100μM) treatment. Transcript levels were quantified with RT-PCR, protein abundance with Western blotting, cytosolic Ca²⁺-activity ([Ca²⁺]i) with Fura-2-fluorescence, SOCE from increase of [Ca²⁺]i following Ca²⁺-readdition after Ca²⁺-store depletion, and apoptosis utilizing flow cytometry. Transcript levels of Orai1 and STIM1, protein expression of Orai1, STIM1, and phosphorylated Akt, as well as SOCE were significantly higher in A2780cis than A2780 cells. SOCE was decreased by Akt inhibitor III (SH-6, 10μM) in A2780cis but not A2780 cells and decreased in both cell lines by Orai1 inhibitor 2-aminoethoxydiphenyl borate (2-ABP, 50μM). Phosphatidylserine exposure and late apoptosis following cisplatin treatment were significantly lower in A2780cis than A2780 cells, a difference virtually abolished by SH-6 or 2-ABP. In conclusion, Orai1/STIM1 expression and function are increased in therapy resistant ovary carcinoma cells, a property at least in part due to enhanced Akt activity and contributing to therapy resistance in those cells.

The neuronal-specific SGK1.1 (SGK1_v2) kinase as a transcriptional modulator of BAG4, Brox, and PPP1CB genes expression

The Serum- and Glucocorticoid-induced Kinase 1, SGK1, exhibits a broad range of cellular functions that include regulation of the number of ion channels in plasma membrane and modulation of signaling pathways of cell survival. This diversity of functions is made possible by various regulatory processes acting upon the SGK1 gene, giving rise to various isoforms: SGK1_v1–5, each with distinct properties and distinct aminotermini that serve to target proteins to different subcellular compartments. Among cellular effects of SGK1 expression is to indirectly modulate gene transcription by phosphorylating transcriptional factors of the FOXO family. Here we examined if SGK1.1 (SGK1_v2; NM_001143676), which associates primarily to the plasma membrane, is also able to regulate gene expression. Using a differential gene expression approach we identified six genes upregulated by SGK1.1 in HeLa cells. Further analysis of transcript and protein levels validated two genes: BCL2-associated athanogene 4 (BAG-4) and Brox. The results indicate that SGK1.1 regulates gene transcription upon a different set of genes some of which participate in cell survival pathways (BAG-4) and others in intracellular vesicular traffic (Brox).

Serum glucocorticoid inducible kinase (SGK)-1 protects endothelial cells against oxidative stress and apoptosis induced by hyperglycaemia

Diabetic hyperglycaemia causes endothelial dysfunction mainly by impairing endothelial nitric oxide (NO) production. Moreover, hyperglycaemia activates several noxious cellular pathways including apoptosis, increase in reactive oxygen species (ROS) levels and diminishing Na(+)-K(+) ATPase activity which exacerbate vascular damage. Serum glucocorticoid kinase (SGK)-1, a member of the serine/threonine kinases, plays a pivotal role in regulating NO production through inducible NO synthase activation and other cellular mechanisms. Therefore, in this study, we aimed to investigate the protective role of SGK-1 against hyperglycaemia in human umbilical endothelial cells (HUVECs). We used retrovirus to infect HUVECs with either SGK-1, SGK-1Δ60 (lacking of the N-60 amino acids-increase SGK-1 activity) or SGK-1Δ60KD (kinase-dead constructs). We tested our hypothesis in vitro after high glucose and glucosamine incubation. Increase in SGK-1 expression and activity (SGK-1Δ60) resulted in higher production of NO, inhibition of ROS synthesis and lower apoptosis in endothelial cell after either hyperglycaemia or glucosamine treatments. Moreover, in this study, we showed increased GLUT-1 membrane translocation and Na(+)-K(+) ATPase activity in cell infected with SGK-1Δ60 construct. These results suggest that as in endothelial cells, an increased SGK-1 activity and expression reduces oxidative stress, improves cell survival and restores insulin-mediated NO production after different noxae stimuli. Therefore, SGK-1 may represent a specific target to further develop novel therapeutic options against diabetic vascular disease.

Discovery of N-[4-(1H-Pyrazolo[3,4-b]pyrazin-6-yl)-phenyl]-sulfonamides as Highly Active and Selective SGK1 Inhibitors

From a virtual screening starting point, inhibitors of the serum and glucocorticoid regulated kinase 1 were developed through a combination of classical medicinal chemistry and library approaches. This resulted in highly active small molecules with nanomolar activity and a good overall in vitro and ADME profile. Furthermore, the compounds exhibited unusually high kinase and off-target selectivity due to their rigid structure.

Targeting serum glucocorticoid-regulated kinase-1 in squamous cell carcinoma of the head and neck: a novel modality of local control

Purpose

The inhibition of serum glucocorticoid-regulated kinase-1 (SGK-1) has been found to decrease growth of colon and prostate cancer cells. The purpose of this study is to evaluate the therapeutic effect of SGK-1 inhibition in head and neck squamous cell carcinoma (SCC).

Experimental Design

Human head and neck tumors (HTB41/43) were established in athymic mice. Growth rates between mice treated with vehicle (PBS) injection (group 1, n = 5), SGK-1 Inhibitor GSK 650394 (group 2, n = 6), systemic cisplatin (group 3, n = 6), and a combination of SGK-1 Inhibitor and cisplatin (group 4, n = 6) were compared using repeated measures one-way ANOVA with Newman-Keuls Multiple Comparison Test. Tumor cells were subsequently submitted to further analyses.

Results

At the end of the experiment mean tumor sizes were 122.33+/−105.86, 76.73+/−36.09, 94.52+/−75.92, and 25.76+/−14.89 mm² (mean +/− SD) for groups 1 to 4. Groups 2 and 3 showed decreased tumor growth compared to controls (p<0.001). Group 4 displayed even greater growth suppression (p<0.0001). Importantly, group 4 fared better than group 3 (p<0.001). CD44 expression was reduced in group 2 (p<0.05), and to an even greater extent in groups 3 and 4 (p<0.0025). A trend towards reduction of HER 2 expression was noted in group 4.

Conclusions

SGK-1 inhibition suppresses tumor growth, and in combination with systemic cisplatin exceeds the effect of cisplatin alone. Decreased expression of CD44 and HER 2 implies depletion of tumor stem cells, and less tumorigenicity. SGK-1 inhibition represents a potential modality of local control for palliation in advanced cases.

Sodium chloride, SGK1, and Th17 activation

The incidence of autoimmune diseases in Western civilizations is increasing rapidly, suggesting an influence of environmental factors, such as diet. The pathogenesis of several of these autoimmune diseases is characterized by aberrant activation of T helper 17 (Th17) cells. Recent reports have shown that the differentiation of Th17 cells is sensitive to changes in local microenvironments, in particular salt (NaCl) concentrations, in a molecular mechanism centered around the serum- and glucocorticoid-inducible kinase 1 (SGK1). In this review, we summarize the recently disclosed mechanisms by which salt has been shown to affect SGK1 and, subsequently, Th17 activation.

Cytotoxic effect of fluvastatin on MCF-7 cells possibly through a reduction of the mRNA expression levels of SGK1 and CAV1

Fluvastatin (FLU) prevents the conversion of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonic acid by inhibiting HMG-CoA reductase and decreases cholesterol level. Although the effects of FLU treatment on several cancer types through many mechanisms have been identified, its relationship with unfolded protein response and apoptosis has not been clearly understood. In this recent study, we aimed to investigate the cytotoxic effect of Fluvastatin on MCF-7 cells and define the transcriptional regulation of specific genes during the occurrence of this cytotoxic effect. We administered 0.62, 2.5, 5, and 40 μM FLU on MCF-7 cells singly and in combination with 2-deoxyglucose (2-DG), and we monitored cell viability and proliferation for 48 hours using real-time cell analyzer system (xCELLigence). At the same time, we measured the mRNA expression levels of glucose-regulated protein 78 (GRP78), CCAAT/enhancer binding protein, homologous protein (CHOP), caveolin-1 (CAV1), NDRG1 Variant 1 and Variant 2, HMOX1, SGK1, and prostate apoptosis response-4 (PAR4) genes using quantitative real-time polymerase chain reaction (LightCycler 480 II). We accepted GAPDH gene and control groups as the reference gene and calibrator, respectively. We performed relative gene expression analyses of the study groups using the QIAGEN 2009 Relative Expression Software Tool (REST). FLU revealed an antiproliferative and cytotoxic effect on MCF-7 cells, while causing the transcriptional regulation of many genes. Of these genes, the mRNA expressions of CHOP, heme oxygenase 1 (HMOX1), N-myc downstream-regulated gene 1 (NDRG1) V1, and NDRG1 V2 increased. On the other hand, the mRNA expression levels of SGK1 and CAV1 decreased. The antiproliferative effects of FLU may be related to the decreased expression levels of SGK1 and CAV1.

Wnt5a-induced Wnt1-inducible secreted protein-1 suppresses vascular smooth muscle cell apoptosis induced by oxidative stress

OBJECTIVE

Apoptosis of vascular smooth muscle cells (VSMCs) contributes to thinning and rupture of the atherosclerotic plaque fibrous cap and is thereby associated with myocardial infarction. Wnt protein activation of β-catenin regulates numerous genes that are associated with cell survival. We therefore investigated Wnt/β-catenin survival signaling in VSMCs and assessed the presence of this pathway in human atherosclerotic plaques at various stages of the disease process.

APPROACH AND RESULTS

Wnt5a induced β-catenin/T-cell factor signaling and retarded oxidative stress (H₂O₂)-induced apoptosis in mouse aortic VSMCs. Quantification of mRNA levels revealed a >4-fold (P<0.05; n=9) increase in the expression of the Wnt/β-catenin responsive gene, Wnt1-inducible secreted protein-1 (WISP-1), which was dependent on cAMP response element-binding protein and sustained in the presence of H₂O₂. Exogenous WISP-1 significantly reduced H₂O₂-induced apoptosis by 43% (P<0.05; n=3) and was shown using silencing small interfering RNA, to be important for Wnt5a-dependent survival responses to H₂O₂ (P<0.05; n=3). WISP-1 protein levels were significantly lower (≈50%) in unstable atherosclerosis compared with stable plaques (n=11 and n=14).

CONCLUSIONS

These results indicate for the first time that Wnt5a induces β-catenin survival signaling in VSMCs via WISP-1. The deficiency of the novel survival factor, WISP-1 in intimal VSMCs of unstable coronary plaques, suggests that there is altered Wnt/β-catenin/ T-cell factor signaling with progressive atherosclerosis, and restoration of WISP-1 protein might be an effective stabilization factor for vulnerable atherosclerotic plaques.

Clinical correlations with (18)FDG PET scan patterns in solid pseudopapillary tumors of the pancreas: still a surgical enigma?

BACKGROUND

There are limited numbers of PET studies of solid pseudopapillary tumors (SPT) of the pancreas.

MATERIALS AND METHODS

We reviewed the medical records of 37 patients who underwent resection of pancreatic SPT and had been preoperatively evaluated by (18)F-FDG PET or PET/CT scan. Immunohistochemical analysis of glucose transporter-1 (GLUT-1) and hexokinase II (HK-II) was performed.

RESULTS

SPT could be categorized into five types according to the morphologic characteristics observed in PET images. Type I (hot FDG uptake in the entire tumor portion) was the most frequent (13, 34.2%), followed by type IV (focal uptake, 12, 31.6%), II (focal defect, 8, 21.1%), III (multiple and geographic uptake, 3, 7.9%), and V (total defective type, 1, 2.6%). The SUVmax in the solid portion of the SPT was 5.3 ± 4.1. The clinical pattern of FDG uptake in SPT was not associated with histopathologic features suggesting malignant potential. The SUVmax of SPT followed a pattern according to pattern of FDG uptake (R(2) = 0.203, p = 0.055), and was significantly associated with adjusted tumor volume (p = 0.001). GLUT-1 was not expressed in SPT, and only eight patients (12.3%) showed mild to moderate expression of HK-II, which was associated with the clinical pattern of SPT in PET images (p < 0.05).

CONCLUSION

SPT of the pancreas could be categorized according to the morphologic patterns observed in PET images. The clinical significance of FDG uptake, glucose metabolism, and clinical usefulness of PET scan in SPT need to be further investigated, and thus this tumor remains a surgical enigma.

Serum and glucocorticoid-regulated kinase 1 promotes vascular smooth muscle cell proliferation via regulation of β-catenin dynamics

In response to arterial intimal injury vascular smooth muscle cells (VSMCs) within the vessel wall proliferate upon exposure to growth factors, accumulate, and form a neointima that can occlude the vessel lumen. Serum and glucocorticoid inducible kinase 1 (SGK1) is a growth factor-responsive kinase; however its role in VSMC proliferation is not fully understood. Here, we examined growth factor-dependent regulation of SGK1 and defined a molecular role for SGK1 in stimulation of VSMC proliferation. We found that stimulation of VSMCs with the pro-proliferative growth factor, platelet-derived growth factor BB (PDGF) significantly increased SGK1 mRNA, protein, and kinase activity in aortic VSMCs in vitro. To test the hypothesis that activation of SGK1 activity promotes VSMC proliferation, we examined the effects of stable expression of constitutively active (S422D) and kinase-defective (S422A) mutants of SGK1 on VSMC growth. We found that activation of SGK1 increased, whereas interference of SGK1 signaling inhibited VSMC growth in vitro. Consistent with these findings, expression of the S422D mutant augmented both basal and PDGF-induced BrdU uptake in VSMCs. Conversely, PDGF-induced BrdU uptake was attenuated in VSMCs expressing S422A. Furthermore, we determined that activated SGK1 enhanced basal and PDGF-dependent G1→S cell cycle transition, whereas dominant-negative SGK1 abrogated G1→S cell cycle transition under similar conditions. Downstream signaling by active SGK1 induced basal and PDGF-induced phosphorylation of glycogen synthase kinase 3β, an effect which was attenuated when SGK1 activity was blocked by expression of the kinase-defective mutant, S422A. We also found that transfection of S422D enhanced β-catenin-nuclear localization and activation of the TOP/Flash and cyclin D1 transcriptional reporters. These effects were significantly blunted in VSMCs transfected with the S422A mutant. Our results provide compelling evidence of a role for SGK1 in stimulation of arterial VSMC growth via regulation of β-catenin dynamics and implicate SGK1 in the progression of intimal narrowing following arterial injury. Hence, the findings presented here point to inhibition of SGK1 activity as a novel therapeutic approach for the treatment of occlusive vascular diseases.

Revealing the role of SGK1 in the dynamics of medulloblastoma using a mathematical model

Deregulation of signaling pathways and subsequent abnormal interactions of downstream genes very often results in carcinogenesis. In this paper, we propose a two-compartment model describing intricate dynamics of the target genes of the Wnt signaling pathway in medulloblastoma. The system of nine nonlinear ordinary differential equations accounts for the formation and dissociation of complexes as well as for the transcription, translation and transport between the cytoplasm and the nucleus. We focus on the interplay between MYC and SGK1 (serum and glucocorticoid-inducible kinase 1), which are the products of Wnt/β-catenin signaling pathway, and GSK3β (glycogen synthase kinase). Numerical simulations of the model solutions yield a better understanding of the process and indicate the importance of the SGK1 gene in the development of medulloblastoma, which has been confirmed in our recent experiments. The model is calibrated based on the gene expression microarray data for two types of medulloblastoma, characterized by monosomy and trisomy of chromosome 6q to highlight the difference between diagnoses.

Comprehensive analysis of β-catenin target genes in colorectal carcinoma cell lines with deregulated Wnt/β-catenin signaling

Background

Deregulation of Wnt/β-catenin signaling is a hallmark of the majority of sporadic forms of colorectal cancer and results in increased stability of the protein β-catenin. β-catenin is then shuttled into the nucleus where it activates the transcription of its target genes, including the proto-oncogenes MYC and CCND1 as well as the genes encoding the basic helix-loop-helix (bHLH) proteins ASCL2 and ITF-2B. To identify genes commonly regulated by β-catenin in colorectal cancer cell lines, we analyzed β-catenin target gene expression in two non-isogenic cell lines, DLD1 and SW480, using DNA microarrays and compared these genes to β-catenin target genes published in the PubMed database and DNA microarray data presented in the Gene Expression Omnibus (GEO) database.

Results

Treatment of DLD1 and SW480 cells with β-catenin siRNA resulted in differential expression of 1501 and 2389 genes, respectively. 335 of these genes were regulated in the same direction in both cell lines. Comparison of these data with published β-catenin target genes for the colon carcinoma cell line LS174T revealed 193 genes that are regulated similarly in all three cell lines. The overlapping gene set includes confirmed β-catenin target genes like AXIN2, MYC, and ASCL2. We also identified 11 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that are regulated similarly in DLD1 and SW480 cells and one pathway – the steroid biosynthesis pathway – was regulated in all three cell lines.

Conclusions

Based on the large number of potential β-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T cells as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study Wnt/β-catenin signaling and associated colorectal carcinogenesis. Furthermore, the confirmed and the newly identified potential β-catenin target genes are useful starting points for further studies.

Adenomatous polyposis coli (APC) membrane recruitment 3, a member of the APC membrane recruitment family of APC-binding proteins, is a positive regulator of Wnt-β-catenin signalling

The adenomatous polyposis coli (APC) membrane recruitment (Amer) family proteins Amer1/Wilms tumour gene on the X chromosome and Amer2 are binding partners of the APC tumour suppressor protein, and act as negative regulators in the Wnt signalling cascade. So far, nothing has been known about the third member of the family, Amer3. Here we show that Amer3 binds to the armadillo repeat domain of APC, similarly to Amer1 and Amer2. Amer3 also binds to the Wnt pathway regulator conductin/axin2. Furthermore, we identified Amer1 as binding partner of Amer3. Whereas Amer1 and Amer2 are linked to the plasma membrane by an N-terminal membrane localization domain, Amer3 lacks this domain. Amer3 localizes to the cytoplasm and nucleus of epithelial cells, and this is dependent on specific nuclear import and export sequences. Functionally, exogenous Amer3 enhances the expression of a β-catenin/T-cell factor-dependent reporter gene, and knockdown of endogenous Amer3 reduces Wnt target gene expression in colorectal cancer cells. Thus, Amer3 acts as an activator of Wnt signalling, in contrast to Amer1 and Amer2, which are inhibitors, suggesting a nonredundant role of Amer proteins in the regulation of this pathway. Our data, together with those of previous studies, provide a comprehensive picture of similarities and differences within the Amer protein family.