Redox sensor NPGPx restrains ZAP70 activity and modulates T cell homeostasis.

Emerging evidences implicate the contribution of ROS to T cell activation and signaling. The tyrosine kinase, ζ-chain-associated protein of 70 kDa (ZAP70), is essential for T cell development and activation. However, it remains elusive whether a direct redox regulation affects ZAP70 activity upon TCR stimulation. Here, we show that deficiency of non-selenocysteine containing phospholipid hydroperoxide glutathione peroxidase (NPGPx), a redox sensor, results in T cell hyperproliferation and elevated cytokine productions. T cell-specific NPGPx-knockout mice reveal enhanced T-dependent humoral responses and are susceptible to experimental autoimmune encephalomyelitis (EAE). Through proteomic approaches, ZAP70 is identified as the key interacting protein of NPGPx through disulfide bonding. NPGPx is activated by ROS generated from TCR stimulation, and modulates ZAP70 activity through redox switching to reduce ZAP70 recruitment to TCR/CD3 complex in membrane lipid raft, therefore subduing TCR responses. These results reveal a delicate redox mechanism that NPGPx serves as a modulator to curb ZAP70 functions in maintaining T cell homeostasis.

TGF-ß1 secreted by Tregs in lymph nodes promotes breast cancer malignancy via up-regulation of IL-17RB.

Lymph node (LN) metastasis is commonly associated with systemic distant organ metastasis in human breast cancer and is an important prognostic predictor for survival of breast cancer patients. However, whether tumor-draining LNs (TDLNs) play a significant role in modulating the malignancy of cancer cells for distant metastasis remains controversial. Using a syngeneic mouse mammary tumor model, we found that breast tumor cells derived from TDLN have higher malignancy and removal of TDLNs significantly reduced distant metastasis. Up-regulation of oncogenic Il-17rb in cancer cells derived from TDLNs contributes to their malignancy. TGF-ß1 secreted from regulatory T cells (Tregs) in the TDLNs mediated the up-regulation of Il-17rb through downstream Smad2/3/4 signaling. These phenotypes can be abolished by TGF-ß1 neutralization or depletion of Tregs. Consistently, clinical data showed that the up-regulation of IL-17RB in cancer cells from LN metastases correlated with the increased prevalence of Tregs as well as the aggressive growth of tumors in mouse xenograft assay. Together, these results indicate that Tregs in TDLNs play an important role in modulating the malignancy of breast cancer cells for distant metastasis. Blocking IL-17RB expression could therefore be a potential approach to curb the process.

Adipocytes promote malignant growth of breast tumours with monocarboxylate transporter 2 expression via ß-hydroxybutyrate.

Adipocytes are the most abundant stromal partners in breast tissue. However, the crosstalk between breast cancer cells and adipocytes has been given less attention compared to cancer-associated fibroblasts. Here we find, through systematic screening, that primary mammary gland-derived adipocytes (MGDAs) promote growth of breast cancer cells that express monocarboxylate transporter 2 (MCT2) both in vitro and in vivo. We show that ß-hydroxybutyrate is secreted by MGDAs and is required to enhance breast cancer cells malignancy in vitro. Consistently, ß-hydroxybutyrate is sufficient to promote tumorigenesis of a mouse xenograft model of MCT2-expressing breast cancer cells. Mechanistically we observe that upon co-culturing with MGDAs or treatment with ß-hydroxybutyrate, breast cancer cells expressing MCT2 increase the global histone H3K9 acetylation and upregulate several tumour-promoting genes. These results suggest that adipocytes promote malignancy of MCT2-expressing breast cancer via ß-hydroxybutyrate potentially by inducing the epigenetic upregulation of tumour-promoting genes.

A High Circulating Tumor Cell Count in Portal Vein Predicts Liver Metastasis From Periampullary or Pancreatic Cancer: A High Portal Venous CTC Count Predicts Liver Metastases.

Circulating tumor cells (CTCs) released from a periampullary or pancreatic cancer can be more frequently detected in the portal than the systemic circulation and potentially can be used to identify patients with liver micrometastases. Aims of this study is to determine if CTCs count in portal venous blood of patients with nonmetastatic periampullary or pancreatic adenocarcinoma can be used as a predictor for subsequent liver metastases. CTCs were quantified in portal and peripheral venous blood samples collected simultaneously during pancreaticoduodenectomy in patients with presumed periampullary or pancreatic adenocarcinoma without image-discernible metastasis. Postoperatively patients were monitored for liver metastasis by abdominal magnetic resonance imaging or computed tomography every 3 months for 1 year. Sixty patients with a pathological diagnosis of periampullary or pancreatic adenocarcinoma were included in the study. Multivariate analysis indicated that portal CTC count was a significant predictor for liver metastases within 6 months after surgery. Eleven of 13 patients with a high portal CTCs count (defined as >112 CMx Platform estimated CTCs in 2 mL blood) developed liver metastases within 6 months after surgery. In contrast, only 6 of 47 patients with a low portal CTC count developed liver metastases (P < 0.0001). A value of 112 CMx Platform estimated CTCs had 64.7% sensitivity and 95.4% specificity to predict liver metastases within 6 months after surgery. We concluded that a high CTC count in portal venous blood collected during pancreaticoduodenectomy in patients with periampullary or pancreatic adenocarcinoma without metastases detected by currently available imaging tools is a significant predictor for liver metastases within 6 months after surgery.

NPGPx modulates CPEB2-controlled HIF-1α RNA translation in response to oxidative stress.

Non-selenocysteine-containing phospholipid hydroperoxide glutathione peroxidase (NPGPx or GPx7) is an oxidative stress sensor that modulates the antioxidative activity of its target proteins through intermolecular disulfide bond formation. Given NPGPx's role in protecting cells from oxidative damage, identification of the oxidative stress-induced protein complexes, which forms with key stress factors, may offer novel insight into intracellular reactive oxygen species homeostasis. Here, we show that NPGPx forms a disulfide bond with the translational regulator cytoplasmic polyadenylation element-binding protein 2 (CPEB2) that results in negative regulation of hypoxia-inducible factor 1-alpha (HIF-1α) RNA translation. In NPGPx-proficient cells, high oxidative stress that disrupts this bonding compromises the association of CPEB2 with HIF-1α RNA, leading to elevated HIF-1α RNA translation. NPGPx-deficient cells, in contrast, demonstrate increased HIF-1α RNA translation under normoxia with both impaired induction of HIF-1α synthesis and blunted HIF-1α-programmed transcription following oxidative stress. Together, these results reveal a molecular mechanism for how NPGPx mediates CPEB2-controlled HIF-1α RNA translation in a redox-sensitive manner.

GIT1 promotes lung cancer cell metastasis through modulating Rac1/Cdc42 activity and is associated with poor prognosis.

G-protein-coupled receptor kinase interacting protein 1 (GIT1) is participated in cell movement activation, which is a fundamental process during tissue development and cancer progression. GIT1/PIX forming a functional protein complex that contributes to Rac1/Cdc42 activation, resulting in increasing cell mobility. Although the importance of Rac1/Cdc42 activation is well documented in cancer aggressiveness, the clinical importance of GIT1 remains largely unknown. Here, we investigated the clinical significance of GIT1 expression in non-small-cell lung cancer (NSCLC) and also verified the importance of GIT1-Rac1/Cdc42 axis in stimulating NSCLC cell mobility. The result indicated higher GIT1 expression patients had significantly poorer prognoses in disease-free survival (DFS) and overall survival (OS) compared with lower GIT1 expression patients. Higher GIT1 expression was an independent prognostic factor by multivariate analysis and associated with migration/invasion of NSCLC cells in transwell assay. In vivo studies indicated that GIT1 promotes metastasis of NSCLC cells. Finally, GIT1 was found to stimulate migration/invasion by altering the activity of Rac1/Cdc42 in NSCLC cells. Together, the GIT1 expression is associated with poor prognosis in patients with NSCLC. GIT1 is critical for the invasiveness of NSCLC cells through stimulating the activity of Rac1/Cdc42.

Targeting IL-17B-IL-17RB signaling with an anti-IL-17RB antibody blocks pancreatic cancer metastasis by silencing multiple chemokines.

Pancreatic cancer has an extremely high mortality rate due to its aggressive metastatic nature. Resolving the underlying mechanisms will be crucial for treatment. Here, we found that overexpression of IL-17B receptor (IL-17RB) strongly correlated with postoperative metastasis and inversely correlated with progression-free survival in pancreatic cancer patients. Consistently, results from ex vivo experiments further validated that IL-17RB and its ligand, IL-17B, plays an essential role in pancreatic cancer metastasis and malignancy. Signals from IL-17B-IL-17RB activated CCL20/CXCL1/IL-8/TFF1 chemokine expressions via the ERK1/2 pathway to promote cancer cell invasion, macrophage and endothelial cell recruitment at primary sites, and cancer cell survival at distant organs. Treatment with a newly derived monoclonal antibody against IL-17RB blocked tumor metastasis and promoted survival in a mouse xenograft model. These findings not only illustrate a key mechanism underlying the highly aggressive characteristics of pancreatic cancer but also provide a practical approach to tackle this disease.

Squalene synthase induces tumor necrosis factor receptor 1 enrichment in lipid rafts to promote lung cancer metastasis.

RATIONALE: Metabolic alterations contribute to cancer development and progression. However, the molecular mechanisms relating metabolism to cancer metastasis remain largely unknown. OBJECTIVES: To identify a key metabolic enzyme that is aberrantly overexpressed in invasive lung cancer cells and to investigate its functional role and prognostic value in lung cancer. METHODS: The differential expression of metabolic enzymes in noninvasive CL1-0 cells and invasive CL1-5 cells was analyzed by a gene expression microarray. The expression of target genes in clinical specimens from patients with lung cancer was examined by immunohistochemistry. Pharmacologic and gene knockdown/overexpression approaches were used to investigate the function of the target gene during invasion and metastasis in vitro and in vivo. The association between the target gene expression and clinicopathologic parameters was further analyzed. Bioinformatic analyses were used to discover the signaling pathways involved in target gene-regulated invasion and migration. MEASUREMENTS AND MAIN RESULTS: Squalene synthase (SQS) was up-regulated in CL1-5 cells and in the tumor regions of the lung cancer specimens. Loss of function or knockdown of SQS significantly inhibited invasion/migration and metastasis in cell and animal models and vice versa. High expression of SQS was significantly associated with poor prognosis among patients with lung cancer. Mechanistically, SQS contributed to a lipid-raft-localized enrichment of tumor necrosis factor receptor 1 in a cholesterol-dependent manner, which resulted in the enhancement of nuclear factor-κB activation leading to matrix metallopeptidase 1 up-regulation. CONCLUSIONS: Up-regulation of SQS promotes metastasis of lung cancer by enhancing tumor necrosis factor-α receptor 1 and nuclear factor-κB activation and matrix metallopeptidase 1 expression. Targeting SQS may have considerable potential as a novel therapeutic strategy to treat metastatic lung cancer.

Deficiency of NPGPx, an oxidative stress sensor, leads to obesity in mice and human.

Elevated oxidative stress is closely associated with obesity. Emerging evidence shows that instead of being a consequence of obesity, oxidative stress may also contribute to fat formation. Nonselenocysteine-containing phospholipid hydroperoxide glutathione peroxidase (NPGPx) is a conserved oxidative stress sensor/transducer and deficiency of NPGPx causes accumulation of reactive oxygen species (ROS). In this communication, we show that NPGPx was highly expressed in preadipocytes of adipose tissue. Deficiency of NPGPx promoted preadipocytes to differentiate to adipocytes via ROS-dependent dimerization of protein kinase A regulatory subunits and activation of CCAAT/enhancer-binding protein beta (C/EBPß). This enhanced adipogenesis was alleviated by antioxidant N-acetylcysteine (NAC). Consistently, NPGPx-deficient mice exhibited markedly increased fat mass and adipocyte hypertrophy, while treatment with NAC ablated these phenotypes. Furthermore, single nucleotide polymorphisms (SNPs) in human NPGPx gene, which correlated with lower NPGPx expression level in adipose tissue, were associated with higher body mass index (BMI) in several independent human populations. These results indicate that NPGPx protects against fat accumulation in mice and human via modulating ROS, and highlight the importance of targeting redox homeostasis in obesity management.

Loss of corepressor PER2 under hypoxia up-regulates OCT1-mediated EMT gene expression and enhances tumor malignancy.

The circadian clock gene Period2 (PER2) has been suggested to be a tumor suppressor. However, detailed mechanistic evidence has not been provided to support this hypothesis. We found that loss of PER2 enhanced invasion and activated expression of epithelial-mesenchymal transition (EMT) genes including TWIST1, SLUG, and SNAIL. This finding was corroborated by clinical observation that PER2 down-regulation was associated with poor prognosis in breast cancer patients. We further demonstrated that PER2 served as a transcriptional corepressor, which recruited polycomb proteins EZH2 and SUZ12 as well as HDAC2 to octamer transcription factor 1 (OCT1) (POU2F1) binding sites of the TWIST1 and SLUG promoters to repress expression of these EMT genes. Hypoxia, a condition commonly observed in tumors, caused PER2 degradation and disrupted the PER2 repressor complex, leading to activation of EMT gene expression. This result was further supported by clinical data showing a significant negative correlation between hypoxia and PER2. Thus, our findings clearly demonstrate the tumor suppression function of PER2 and elucidate a pathway by which hypoxia promotes EMT via degradation of PER2.

Nitric oxide modulates mitochondrial activity and apoptosis through protein S-nitrosylation for preimplantation embryo development.

PURPOSE: Previous studies reported that patients with endometriosis had excess nitric oxide (NO) in the reproductive tract and poor embryo development in IVF cycles. This study aims to elucidate the effects of NO on early embryo development. METHODS: Zygotes from superovulated B6CBF1 mice were cultured to blastocysts in a variety of media. Sodium nitroprusside (SNP) and N(G)-nitro-L-arginine (LNA) were added to the culture medium as a NO donor and a NO synthase inhibitor, respectively. The localization and fluorescence intensity of S-nitrosylated (SNO) proteins within 2-cell stage embryos were analyzed with confocal microscopy. Apoptosis and ATP production in the blastocysts were measured. RESULT(S): Subsequent to NO exposure, the SNO proteins mainly colocalized with the mitochondria and endoplasmic reticulum and the intensity of SNO proteins increased. The addition of a quanylate cyclase inhibitor and a cyclic GMP mimic agent induced nonsignificant changes in SNO proteins, whereas addition of a superoxide scavenger or a reduced form of glutathione rescued the embryos from the effects of NO. However, superoxide scavenger supplementation resulted in decreased blastocyst ATP production. CONCLUSION(S): Elevated NO exerts deleterious effects on embryo development, possibly through protein S-nitrosylation in the mitochondria and endoplasmic reticulum. Including glutathione as a component in the culture medium might counteract this effect.

A cis-element with mixed G-quadruplex structure of NPGPx promoter is essential for nucleolin-mediated transactivation on non-targeting siRNA stress.

We reported that non-targeting siRNA (NT-siRNA) stress induces non-selenocysteine containing phospholipid hydroperoxide glutathione peroxidase (NPGPx) expression to cooperate with exoribonuclease XRN2 for releasing the stress [Wei,P.C., Lo,W.T., Su,M.I., Shew,J.Y. and Lee,W.H. (2011) Non-targeting siRNA induces NPGPx expression to cooperate with exoribonuclease XRN2 for releasing the stress. Nucleic Acids Res., 40, 323-332]. However, how NT-siRNA stress inducing NPGPx expression remains elusive. In this communication, we showed that the proximal promoter of NPGPx contained a mixed G-quadruplex (G4) structure, and disrupting the structure diminished NT-siRNA induced NPGPx promoter activity. We also demonstrated that nucleolin (NCL) specifically bonded to the G4-containing sequences to replace the originally bound Sp1 at the NPGPx promoter on NT-siRNA stress. Consistently, overexpression of NCL further increased NPGPx promoter activity, whereas depletion of NCL desensitized NPGPx promoter to NT-siRNA stress. These results suggest that the cis-element with mixed G4 structure at the NPGPx promoter plays an essential role for its transactivation mediated by NCL to release cells from NT-siRNA stress.

Loss of the oxidative stress sensor NPGPx compromises GRP78 chaperone activity and induces systemic disease.

NPGPx is a member of the glutathione peroxidase (GPx) family; however, it lacks GPx enzymatic activity due to the absence of a critical selenocysteine residue, rendering its function an enigma. Here, we show that NPGPx is a newly identified stress sensor that transmits oxidative stress signals by forming the disulfide bond between its Cys57 and Cys86 residues. This oxidized form of NPGPx binds to glucose-regulated protein (GRP)78 and forms covalent bonding intermediates between Cys86 of NPGPx and Cys41/Cys420 of GRP78. Subsequently, the formation of the disulfide bond between Cys41 and Cys420 of GRP78 enhances its chaperone activity. NPGPx-deficient cells display increased reactive oxygen species, accumulated misfolded proteins, and impaired GRP78 chaperone activity. Complete loss of NPGPx in animals causes systemic oxidative stress, increases carcinogenesis, and shortens life span. These results suggest that NPGPx is essential for releasing excessive ER stress by enhancing GRP78 chaperone activity to maintain physiological homeostasis.

Activation of Robo1 signaling of breast cancer cells by Slit2 from stromal fibroblast restrains tumorigenesis via blocking PI3K/Akt/ß-catenin pathway.

Tumor microenvironment plays a critical role in regulating tumor progression by secreting factors that mediate cancer cell growth. Stromal fibroblasts can promote tumor growth through paracrine factors; however, restraint of malignant carcinoma progression by the microenvironment also has been observed. The mechanisms that underlie this paradox remain unknown. Here, we report that the tumorigenic potential of breast cancer cells is determined by an interaction between the Robo1 receptor and its ligand Slit2, which is secreted by stromal fibroblasts. The presence of an active Slit2/Robo1 signal blocks the translocation of ß-catenin into nucleus, leading to downregulation of c-myc and cyclin D1 via the phosphoinositide 3-kinase (PI3K)/Akt pathway. Clinically, high Robo1 expression in the breast cancer cells correlates with increased survival in patients with breast cancer, and low Slit2 expression in the stromal fibroblasts is associated with lymph node metastasis. Together, our findings explain how a specific tumor microenvironment can restrain a given type of cancer cell from progression and show that both stromal fibroblasts and tumor cell heterogeneity affect breast cancer outcomes.

Breast cancer cells induce stromal fibroblasts to secrete ADAMTS1 for cancer invasion through an epigenetic change.

Microenvironment plays an important role in cancer development. We have reported that the cancer-associated stromal cells exhibit phenotypic and functional changes compared to stromal cells neighboring to normal tissues. However, the molecular mechanisms as well as the maintenance of these changes remain elusive. Here we showed that through co-culture with breast cancer cells for at least three to four passages, breast normal tissue-associated fibroblasts (NAFs) gained persistent activity for promoting cancer cell invasion, partly via up-regulating ADAM metallopeptidase with thrombospondin type 1 motif, 1 (ADAMTS1). Furthermore, we demonstrated that the DNA methylation pattern in the ADAMTS1 promoter has no alteration. Instead, the loss of EZH2 binding to the ADAMTS1 promoter and the resulting decrease of promoter-associated histone H3K27 methylation may account for the up-regulation of ADAMTS1. Importantly, the lack of EZH2 binding and the H3K27 methylation on the ADAMTS1 promoter were sustained in cancer cell-precocultured NAFs after removal of cancer cells. These results suggest that cancer cells are capable of inducing stromal fibroblasts to secrete ADAMTS1 persistently for their invasion and the effect is epigenetically inheritable.

Non-targeting siRNA induces NPGPx expression to cooperate with exoribonuclease XRN2 for releasing the stress.

Short interfering RNAs (siRNAs) target specific mRNAs for their degradation mediated by RNA-induced silencing complex (RISC). Persistent activation of siRNA-RISC frequently leads to non-targeting toxicity. However, how cells mediate this stress remains elusive. In this communication, we found that the presence of non-targeting siRNA selectively induced the expression of an endoplasmic reticulum (ER)-resident protein, non-selenocysteine containing phospholipid hydroperoxide glutathione peroxidase (NPGPx), but not other ER-stress proteins including GRP78, Calnexin and XBP1. Cells suffering from constant non-targeting siRNA stress grew slower and prolonged G1 phase, while NPGPx-depleted cells accumulated mature non-targeting siRNA and underwent apoptosis. Upon the stress, NPGPx covalently bound to exoribonuclease XRN2, facilitating XRN2 to remove accumulated non-targeting siRNA. These results suggest that NPGPx serves as a novel responder to non-targeting siRNA-induced stress in facilitating XRN2 to release the non-targeting siRNA accumulation.

Breast cancer cells induce cancer-associated fibroblasts to secrete hepatocyte growth factor to enhance breast tumorigenesis.

It has been well documented that microenvironment consisting of stroma affects breast cancer progression. However, the mechanisms by which cancer cells and fibroblasts, the major cell type in stroma, interact with each other during tumor development remains to be elucidated. Here, we show that the human cancer-associated fibroblasts (CAFs) had higher activity in enhancing breast tumorigenecity compared to the normal tissue-associated fibroblasts (NAFs) isolated from the same patients. The expression level of hepatocyte growth factor (HGF) in these fibroblasts was positively correlated with their ability to enhance breast tumorigenesis in mice. Deprivation of HGF using a neutralizing antibody reduced CAF-mediated colony formation of human breast cancer cells, indicating that CAFs enhanced cancer cell colony formation mainly through HGF secretion. Co-culture with human breast cancer MDA-MB-468 cells in a transwell system enhanced NAFs to secret HGF as well as promote tumorigenecity. The newly gained ability of these "educated" NAFs became irreversible after continuing this process till fourth passage. These results suggested that breast cancer cells could alter the nature of its surrounding fibroblasts to secrete HGF to support its own progression through paracrine signaling.

Regulation of IAPs gene family by interleukin-1 alpha and Epstein-Barr virus in nasopharyngeal carcinoma.

BACKGROUND: Inhibitors of apoptosis proteins (IAPs), which counteract apoptosis by potently inhibiting caspase activation, are promising targets of new anti-tumor therapy. However, their roles in the pathogenesis of nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-associated carcinoma, are not fully understood. Herein, we investigated the expression and regulation of IAPs in NPC. METHODS AND RESULTS: Using real-time quantitative polymerase chain reaction (PCR) analysis, we found that among the IAPs family only the transcription of survivin, HIAP-1, and HIAP-2 was consistently up-regulated in NPC and metastatic NPC tissues. Immunohistochemical staining showed that their proteins were more predominantly expressed in tumor cells nests. Noteworthy, these IAPs were upregulated by interleukin-1 alpha stimulation or EBV infection, and subsequently resulted in triggering rapid proliferation of NPC verified by strong Ki-67 staining. CONCLUSION: Survivin, HIAP-1, and HIAP-2 were distinctly upregulated in NPC, suggesting they may play significant roles in NPC tumorigenesis and serve as tumor markers with prognostic and therapeutic implications.

Decreased expression of UK114 is related to the differentiation status of human hepatocellular carcinoma.

Previous studies have identified that the expression of UK114 is tissue specific and the protein has been found to be most abundant in liver and kidney. However, the expression of UK114 in human hepatocellular carcinoma and its relationship to differentiation and transformation of hepatocellular carcinoma have not been studied. In this study, the expression of UK114 in human hepatocellular carcinoma was examined by Northern and Western blot analyses. We found that UK114 was significantly down-regulated in most of hepatocellular carcinoma tissues compared with adjacent nontumor tissues (72.7%) at both mRNA and protein levels. We looked into the possibility that this decreased expression of UK114 in the hepatocellular carcinoma tissues may play a role in the differentiation or tumorigenicity of hepatocellular carcinoma. Immunohistochemical staining showed that the reduced expression of UK114 in hepatocellular carcinoma tissues was correlated with the tumor differentiation status as graded by the Edmondson-Steiner classification. On the other hand, overexpression of UK114 was not able to suppress the proliferation of human hepatoma cells and tumorigenicity in nude mice. These results suggest that UK114 does not seem to act as a tumor suppressor gene; however, it may useful as a biomarker that will assist in the grading of the differentiation status of hepatocellular carcinoma samples.