Cloning, expression, and mutation analysis of NOR1, a novel human gene down-regulated in HNE1 nasopharyngeal carcinoma cell line

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Combination therapy based on dual-target biomimetic nano-delivery system for overcoming cisplatin resistance in hepatocellular carcinoma

Strategies to overcome toxicity and drug resistance caused by chemotherapeutic drugs for targeted therapy against hepatocellular carcinoma (HCC) are urgently needed. Previous studies revealed that high oxidored-nitro domain-containing protein 1(NOR1) expression in HCC was associated with cisplatin (DDP) resistance. Herein, a novel dual-targeting nanocarrier system AR-NADR was generated for the treatment of DDP resistance in HCC. The core of the nanocarrier system is the metal-organic frameworks (MOF) modified with nuclear location sequence (NLS), which loading with DDP and NOR1 shRNA (R). The shell is an A54 peptide inserted into the erythrocyte membrane (AR). Our results show that AR-NADR efficiently internalized by tumor cells due to its specific binding to the A54 receptors that are abundantly expressed on the surface of HCC cells and NLS peptide-mediated nuclear entry. Additionally, DDP is more likely to be released due to the degradation of Ag-MOF in the acidic tumor microenvironment. Moreover, by acting as a vector for gene delivery, AR-NADR effectively inhibits tumor drug resistance by suppressing the expression of NOR1, which induces intracellular DDP accumulation and makes cells sensitive to DDP. Finally, the anti-HCC efficacy and mechanisms of AR-NADR were systematically elucidated by a HepG2/DDP cell model as well as a tumor model. Therefore, AR-NADR constitutes a key strategy to achieve excellent gene silencing and antitumor efficacy, which provides effective gene therapy and precise treatment strategies for cisplatin resistance in HCC.

The Paradoxical Roles of Orphan Nuclear Receptor 4A (NR4A) in Cancer

The three-orphan nuclear receptor 4A genes are induced by diverse stressors and stimuli, and there is increasing evidence that NR4A1 (Nur77), NR4A2 (Nurr1), and NR4A3 (Nor1) play an important role in maintaining cellular homeostasis and in pathophysiology. In blood-derived tumors (leukemias and lymphomas), NR4A expression is low and NR4A1^-/-/NR4A3^-/- double knockout mice rapidly develop acute myelocytic leukemia, suggesting that these receptors exhibit tumor suppressor activity. Treatment of leukemia and most lymphoma cells with drugs that induce expression of NR4A1and NR4A3 enhances apoptosis, and this represents a potential clinical application for treating this disease. In contrast, most solid tumor-derived cell lines express high levels of NR4A1 and NR4A2, and both receptors exhibit pro-oncogenic activities in solid tumors, whereas NR4A3 exhibits tumor-specific activities. Initial studies with retinoids and apoptosis-inducing agents demonstrated that their cytotoxic activity is NR4A1 dependent and involved drug-induced nuclear export of NR4A1 and formation of a mitochondrial proapoptotic NR4A1-bcl-2 complex. Drug-induced nuclear export of NR4A1 has been reported for many agents/biologics and involves interactions with multiple mitochondrial and extramitochondrial factors to induce apoptosis. Synthetic ligands for NR4A1, NR4A2, and NR4A3 have been identified, and among these compounds, bis-indole derived (CDIM) NR4A1 ligands primarily act on nuclear NR4A1 to inhibit NR4A1-regulated pro-oncogenic pathways/genes and similar results have been observed for CDIMs that bind NR4A2. Based on results of laboratory animal studies development of NR4A inducers (blood-derived cancers) and NR4A1/NR4A2 antagonists (solid tumors) may be promising for cancer therapy and also for enhancing immune surveillance.

CircRNA_101505 sensitizes hepatocellular carcinoma cells to cisplatin by sponging miR-103 and promotes oxidored-nitro domain-containing protein 1 expression

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and a leading cause of cancer-related deaths worldwide. Emerging studies have shown that circular RNAs (circRNAs) are differentially expressed in HCC and play an important role in HCC pathogenesis and metastasis. However, the mechanism of circRNA in the chemoresistance of HCC remains unclear. In this study, we aimed to investigate the role of circRNA in cisplatin resistance of HCC. We identified a novel circRNA circRNA_101505 that was decreased in cisplatin-resistant HCC tissues and cell lines, and associated with a poor survival outcome. Gain-of-function investigations showed that overexpression of circRNA_101505 suppressed cancer cell growth in vivo and in vitro, and enhanced cisplatin toxicity in HCC cells. Mechanistic studies found that circRNA_101505 could sensitize HCC cells to cisplatin by sponging miR-103, and thereby promoting oxidored-nitro domain-containing protein 1 (NOR1) expression. In conclusion, the significant inhibitory effects indicate circRNA_101505 to be a potential therapeutic target for HCC treatment. Our findings provide significant evidence to further elucidate the therapeutic use of circRNA in HCC.

CiliaCarta: An integrated and validated compendium of ciliary genes

The cilium is an essential organelle at the surface of mammalian cells whose dysfunction causes a wide range of genetic diseases collectively called ciliopathies. The current rate at which new ciliopathy genes are identified suggests that many ciliary components remain undiscovered. We generated and rigorously analyzed genomic, proteomic, transcriptomic and evolutionary data and systematically integrated these using Bayesian statistics into a predictive score for ciliary function. This resulted in 285 candidate ciliary genes. We generated independent experimental evidence of ciliary associations for 24 out of 36 analyzed candidate proteins using multiple cell and animal model systems (mouse, zebrafish and nematode) and techniques. For example, we show that OSCP1, which has previously been implicated in two distinct non-ciliary processes, causes ciliogenic and ciliopathy-associated tissue phenotypes when depleted in zebrafish. The candidate list forms the basis of CiliaCarta, a comprehensive ciliary compendium covering 956 genes. The resource can be used to objectively prioritize candidate genes in whole exome or genome sequencing of ciliopathy patients and can be accessed at http://bioinformatics.bio.uu.nl/john/syscilia/ciliacarta/.

Abberent expression of NOR1 protein in tumor associated macrophages contributes to the development of DEN-induced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary tumor of the liver and the sixth most common lethal cancer worldwide. Recent evidences demonstrated that oxidored nitro domain containing protein 1 (NOR1), a putative tumor suppressor gene, is overexpressed in human HCC tissues. However, the role of NOR1 in HCC development remains unclear. Here, we described that NOR1 protein level is elevated in HCC and is associated with poorer clinical outcome. However, ecotopic overexpression of NOR1 protein in human HCC cell line HepG2 cells had no effect on cells proliferation, migration, and clonality. Immunofluoresence assay indicates NOR1 protein is mainly expressed at CD163 positive M2 tumor associated macrophages (TAMs). To explore the role of NOR1 in the development of HCC, we interrogated the susceptibility of mice lacking the NOR1 gene to DEN-induced hepatocarcinogenesis. NOR1 deficient mice displayed resistance to DEN-induced HCC. We also demonstrate that mNOR1 protein is enriched in F4/80 positive Kupffer cells (KCs) infiltrated in DEN induced murine HCC tissues. Loss of NOR1 led to increase of iNOS whereas decrease of Arg1, Ym1 expression in KCs. Overexpression of NOR1 in THP-1 macrophages led to decrease of iNOS but increase of Arg1. Mechanistic investigations showed that inflammatory cytokines IL-6, TNF-α production, and NF-κB activation were also decreased in NOR1 knockout mice exposed to DEN treatment. Our data suggested that NOR1 is overexpressed in HCC associated TAMs and promotes M2 alternative polarization. Genetic deletion of NOR1 in mice leads to impairment of IL-6 production and NF-κB activation, which in turn attenuates DEN-induced HCC development.

Significance of the NOR1-FOXA1/HDAC2-Slug regulatory network in epithelial-mesenchymal transition of tumor cells

The epithelial-mesenchymal transition (EMT) process is believed to play a crucial role in nasopharyngeal carcinoma (NPC) progression, a squamous cell carcinoma of the head and neck with the tendency to metastasize early. At present, much attention has been given to the inducer of EMT involved in NPC progression, while antagonists have been less intensively characterized. In this study, unbiased analysis of EMT-associated gene expression patterns was performed using data mining of global gene expression profiles derived from NPC samples, leading to the successful identification of NOR1, FOXA1, and Slug, all of which showed aberrant expression during NPC progression. The effect of tumor suppressor NOR1 on Slug-induced NPC cells during the EMT process was investigated by use of ectopic expression and RNA interference methods. The molecular mechanisms underlying the tumor-suppressing effect of NOR1 on Slug-induced EMT were thought to be dependent on the cooperation of NOR1 with the FOXA1-HDAC2 complex. We also showed that FOXA1 and HDAC2 bind the slug promoter and directly repress its transcription. Our data revealed a previously unrecognized role of the NOR1-FOXA1/HDAC2-Slug network in the regulation of the EMT process and aggressiveness of NPC.

Oxidored-nitro domain-containing protein 1 promotes liver fibrosis by activating the Wnt/β-catenin signaling pathway in vitro

Hepatic fibrosis is a characteristic of various types of chronic liver diseases, and may further develop into liver cirrhosis and liver cancer. Oxidored‑nitro domain‑containing protein 1 (NOR1) expression levels are greater in hepatitis, cirrhosis and hepatocellular carcinoma samples compared with from normal liver samples. However, the importance of NOR1 in liver fibrosis remains to be elucidated. The present study aimed to investigate the effect of NOR1 on the proliferation and matrix expression of human hepatic stellate cells (HSCs) in vitro. Additionally, the molecular mechanisms underlying the role of NOR1 in the activation of HSCs was investigated. The present study determined that transforming growth factor β1 (TGF‑β1) may induce NOR1 expression in HSCs in a dose‑dependent manner, as determined by reverse transcription‑quantitative polymerase chain reaction and western blot analysis. NOR1‑small hairpin (sh)RNA was transfected into TGF‑β1‑treated HSCs to knock down NOR1. The MTT assay revealed that TGF‑β1‑induced cell proliferation was significantly inhibited in the NOR1‑shRNA group. In addition, NOR1 knockdown significantly inhibited TGF‑β1‑induced protein expression of fibrosis indexes, including collagen 1, 3 and α‑smooth muscle actin (α‑SMA). Subsequently, NOR1‑pcDNA3.1 was transfected into HSCs to overexpress NOR1. It was revealed that NOR1 overexpression may activate the Wnt/β‑catenin pathway in HSCs. The gain‑of function experiments demonstrated that NOR1 overexpression promoted cell proliferation and the expression of fibrosis indexes; however, these effects may be attenuated by dickkopf‑1, an inhibitor of the Wnt/β‑catenin signaling pathway. In conclusion, the present study demonstrated that NOR1 activates HSCs and contributes to liver fibrosis in vitro and this effect was achieved through the activation of the Wnt/β‑catenin pathway. Therefore, the current study may provide a novel target for the treatment of chronic liver diseases.

NOR1 Suppresses Cancer Stem-Like Cells Properties of Tumor Cells via the Inhibition of the AKT-GSK-3β-Wnt/β-catenin-ALDH1A1 Signal Circuit

Cancer stem cells (CSCs) play a key role in tumor radiotherapy and chemotherapy resistance, relapse, and metastasis, and are primarily maintained in a resting state in vivo. The failure of conventional therapies to target CSCs is the main cause of treatment failure. The discovery of CSCs in nasopharyngeal carcinoma (NPC) tumors is becoming more prevalent; however, the understanding of the mechanisms underlying the maintenance of tumor stemness is still limited. We previously cloned NOR1, a tumor suppressor gene downregulated in NPC cell lines and tissues. In this study, we demonstrate that Wnt/β-catenin and ALDH1A1 form a signal circuit and that NOR1 antagonizes the tumor stem cell-like phenotype in NPC cell lines: the ectopic overexpression of NOR1 reduced β-catenin and ALDH1A1 expression; β-catenin/TCF4 targeted the regulation of ALDH1A1 transcription in NPC cells; silencing ALDH1A1 reduced AKT (total and phosphorylated) and GSK-3β (phosphorylated) expression; and eventually feedback decreased β-catenin expression levels. We also found that NOR1 expression decreased cancer stem-like cell properties of NPC cells, reduced their ability to form tumor spheroids in vitro, reduced tumorigenicity in nude mice in vivo, and increased sensitivity to chemotherapy agents. Taken together, our findings illustrated a new function of NOR1 that suppresses cancer stem-like cell properties in tumor cells by inhibiting the AKT-GSK-3β-Wnt/β-catenin-ALDH1A1 signal circuit. The study suggests that NOR1 deletion expression in NPC cells may be a potential molecular target for cancer stem cell therapy. J. Cell. Physiol. 232: 2829-2840, 2017. © 2016 Wiley Periodicals, Inc.

The NOR1/OSCP1 proteins in cancer: from epigenetic silencing to functional characterization of a novel tumor suppressor

NOR1 (Oxidored-nitro domain-containing protein 1), also known as OSCP1, was first identified in nasopharyngeal carcinoma (NPC) cells in 2003. NOR1 is evolutionarily conserved among species with its expression is restricted to brain, testis and respiratory epithelial cells. NOR1 was downregulated in NPC and the downregulation associates with poor prognosis. Previous study demonstrated that hypermethylation of NOR1 promoter was observed in NPC and hematological malignancies, which has been believed to be the main epigenetic cause for NOR1 silencing in these cancers. Recently, the NOR1 tumor suppressor status has been fully established. NOR1 inhibited cancer cell growth by disturbing tumor cell energe metabolism. NOR1 also promote tumor cells apoptosis in oxidative stress and hypoxia by inhibition of stress induced autophagy. Moreover, NOR1 suppressed cancer cell epithelial-mesenchymal transition, invasion and metastasis via activation of FOXA1/HDAC2-slug regulatory network. Deciphering the molecular mechanisms underlying NOR1 mediated tumor suppressive role would be helpful to a deeper understanding of carcinogenesis and, furthermore, to the development of new therapeutic approaches. Here we summarize the current knowledge on NOR1 focusing on its expression pattern, epigenetic and genetic association with human cancers and its biological functions. This review will also elucidate the potential application of NOR1/OSCP1 for some human malignancies.

Oxidored-nitro domain-containing protein 1 expression is associated with the progression of hepatocellular carcinoma

Hepatocarcinogenesis is a stepwise process during which multiple genes are altered. Understanding the molecular mechanisms that induce hepatocarcinogenesis may improve the screening, prevention and treatment of patients with hepatocellular carcinoma (HCC). In recent years, the oxidored-nitro domain-containing protein 1 (NOR1) gene has been identified to have an important role in the development of HCC in vitro experiments. The current study aimed to examine the expression of NOR1 mRNA and protein expression in specimens of normal liver, hepatitis, cirrhosis and HCC, together representing the process of HCC development. Furthermore, the association between NOR1 expression and clinicopathological parameters of HCC patients was analyzed. Tissue microarrays containing the specimens of human normal liver, hepatitis, cirrhosis and HCC were purchased, and in situ hybridization and immunohistochemistry were used to detect the expression of NOR1 mRNA and protein expression, respectively. It was revealed that the positive rate of NOR1 protein and mRNA expression in the specimens of hepatitis and cirrhosis were not significantly different from that in the normal liver samples. However, the specimens of HCC exhibited an increased positive rate of NOR1 protein and mRNA expression in comparison with the normal liver samples. In addition, a higher positive rate of NOR1 protein expression was observed in HCC patients with a poor pathological differentiation grade and high tumor node metastasis (TNM) stage. In conclusion, the present study provides evidence, for the first time, of the increased expression of NOR1 in human HCC tissues, and its correlation with the pathological stage and TNM status. These findings indicate that NOR1 may be involved in the progression of HCC and it could be employed as a predictive biomarker in HCC development.

Nuclear receptor 4A (NR4A) family - orphans no more

The orphan nuclear receptors NR4A1, NR4A2 and NR4A3 are immediate early genes induced by multiple stressors, and the NR4A receptors play an important role in maintaining cellular homeostasis and disease. There is increasing evidence for the role of these receptors in metabolic, cardiovascular and neurological functions and also in inflammation and inflammatory diseases and in immune functions and cancer. Despite the similarities of NR4A1, NR4A2 and NR4A3 and their interactions with common cis-genomic elements, they exhibit unique activities and cell-/tissue-specific functions. Although endogenous ligands for NR4A receptors have not been identified, there is increasing evidence that structurally-diverse synthetic molecules can directly interact with the ligand binding domain of NR4A1 and act as agonists or antagonists, and ligands for NR4A2 and NR4A3 have also been identified. Since NR4A receptors are key factors in multiple diseases, there are opportunities for the future development of NR4A ligands for clinical applications in treating multiple health problems including metabolic, neurologic and cardiovascular diseases, other inflammatory conditions, and cancer.

Tumor suppressor gene OSCP1/NOR1 regulates apoptosis, proliferation, differentiation, and ROS generation during eye development of Drosophila melanogaster

OSCP1/NOR1 (organic solute carrier partner 1/oxidored nitrodomain-containing protein 1) is a known tumor suppressor protein. OSCP1 has been reported to mediate transport of various organic solutes into cells; however, its role during development has not yet been addressed. Here we report the results of studies on dOSCP1 (the Drosophila ortholog of hOSCP1) to elucidate the role of OSCP1/NOR1 during development. Knockdown of dOSCP1 in the eye imaginal discs induced a rough-eye phenotype in adult flies. This phenotype resulted from induction of caspase-dependent apoptosis followed by a compensatory cell proliferation and generation of reactive oxygen species in eye imaginal discs. The induction of apoptosis appears to be associated with down-regulation of the anti-apoptotic Buffy gene and up-regulation of the pro-apoptotic Debcl gene. These effects of knockdown of dOSCP1 lead to mitochondrial fragmentation, degradation, and a shortfall in ATP production. We also found that knockdown of dOSCP1 causes a defect in cone cell and pigment cell differentiation in pupal retinae. Moreover, mutations in epidermal growth factor receptor pathway-related genes, such as Spitz and Drk, enhanced the rough-eye phenotype induced by dOSCP1 knockdown. These results suggest that dOSCP1 positively regulates the epidermal growth factor receptor signaling pathway. Overall, our findings indicate that dOSCP1 plays multiple roles during eye development in Drosophila.

Genetic polymorphism of the human organic solute carrier protein 1 (hOSCP1) gene in Japanese patients with non-viral liver carcinoma

Human organic solute carrier protein 1 (hOSCP1) is a Na⁺-independent multispecific organic solute transporter. To date, several studies have revealed that gene mutations of the transporters are likely to be associated with some diseases; however, there are no data concerning the genetic polymorphism of the hOSCP1 gene in Japanese patients with non-viral liver carcinoma (LC). In the present study, we isolated genomic DNA from a normal portion of LC, and analyzed 41 single nucleotide polymorphisms (SNPs) chosen from a database of SNPs (dbSNPs). We found genotype frequencies for 2 non-synonymous SNPs [rs34409118 (Thr¹³¹ → Ala) and rs1416840 (Ile²¹⁹ → Thr)] and 1 synonymous SNP [rs16822954 (Ser¹⁹³ → Ser)] to be statistically significant when compared with dbSNPs. No statistical significance was observed in rs2275477 (Gly³⁰⁷ → Arg) in the hOSCP1 gene. With respect to the allele frequency, we also observed rs34409118 to be statistically significant. Interestingly, we found that non-viral LC patients do not carry heterozygous mutations in rs1416840 (A/G) and rs16822954 (A/G), suggesting that a non-carrier of heterozygous mutations in these two SNPs might be a biomarker for susceptibility for non-viral LC in Japanese. Further analyses of patients with hOSCP1 variants may elucidate the relationship between the hOSCP1 gene and susceptibility of non-viral LC in Japanese patients.

Overexpression of oxidored-nitro domain containing protein 1 induces growth inhibition and apoptosis in human prostate cancer PC3 cells

Previous studies have reported that oxidored-nitro domain containing protein 1 (NOR1) is a novel tumor suppressor gene identified in various types of cancer, such as nasopharyngeal carcinoma and cervical cancer. Recent studies have shown that NOR1 expression is lower in prostate cancer compared with normal prostate tissue. However, the specific function and exact mechanism of NOR1 in prostate cancer remains to be clarified. The present study aimed to investigate the function and mechanism of NOR1 in prostate cancer PC3 cells. DU145 and PC3 cells were transduced with a vector and cell viability, proliferation and apoptosis were determined. As predicted, NOR1 overexpression significantly inhibited growth and apoptosis in PC3 cells. NOR1 overexpression decreased the expression of the anti-apoptotic genes Bcl-2 and Bcl-xl and increased the level of the pro-apoptotic genes Bax and Bak in PC3 cells. Further investigation demonstrated that NOR1 overexpression activates caspase-3. Silencing of NOR1 did not inhibit growth or induce apoptosis in PC3 cells. Moreover, NOR1 inhibited proliferation and induced apoptosis via the activation of MAPK. The overexpression of NOR1 significantly inhibited tumor growth in PC3 tumor-bearing nude mice. The results suggest that the upregulated NOR1 expression was able to inhibit the progression of prostate cancer. Thus, NOR1 may be an ideal target for the treatment of prostate cancer.

Structural characterization and subcellular localization of Drosophila organic solute carrier partner 1

Background

Organic solute carrier partner 1 (OSCP1) is known to facilitate the transport of various organic solutes into cells and reported to play a role in cell growth and cell differentiation. Moreover, OSCP1 is known as a tumor suppressor gene that is frequently down-expressed in nasopharyngeal carcinomas and acute myeloid leukemia. However, the underlying mechanisms of action remain unclear and the subcellular localization of OSCP1 has yet to be determined in detail.

Results

Drosophila contains a single orthologue of OSCP1 (dOSCP1) that shares 58% homology with its human counterpart. To study the expression pattern and subcellular localization of dOSCP1, we prepared a specific antibody. Subcellular localization analyses of dOSCP1 with these revealed localization in the plasma membrane, endoplasmic reticulum, Golgi apparatus and mitochondria, but no detection in cytosol. dOSCP1 signals were also detected in the nucleus, although at weaker intensity than in plasma membranes and subcellular organelles. In addition, native polyacrylamide gel electrophoresis analysis with and without β-mercaptoethanol treatment revealed that recombinant dOSCP1 forms dimers and trimers in solution. The dimer form of dOSCP1 could also be detected by Western immunoblot analyses in third instar larval extracts.

Conclusions

The data revealed that dOSCP1 localizes not only in the plasma membrane but also in the nucleus, ER, Golgi apparatus and mitochondria. It is therefore conceivable that this protein may interact with various partners or form multimeric complexes with other proteins to play multiple roles in cells, providing clues to understanding the functions of dOSCP1 during Drosophila development.

Expression of oxidored nitro domain-containing protein 1(NOR1) impairs nasopharyngeal carcinoma cells adaptation to hypoxia and inhibits PDK1 expression

Hypoxia is a characteristic pathophysiological property of locally advanced solid tumors and a relevant factor of the tumor (patho-)physiome since it can promote tumor progression and resistance to therapy. Tumors alter their metabolic pathways to survive in nutrient and oxygen poor microenvironments by a process known as the "Warburg Effect." The current studies identify a novel tumor suppressor gene, termed oxidored nitro domain-containing protein 1 (NOR1) which alters hypoxia cellular response in nasopharyngeal carcinoma. NOR1 expression causes apoptosis of tumor cells in hypoxia by altering the expression of PDK1 expression and mitochondrial Bax-Bcl2 balance thus suppress tumor cell adaptation to hypoxia. Although the importance of hypoxia cellular response is well documented in tumor progression, this is the first demonstration of a human tumor suppressor which functions by regulating mitochondrial apoptotic pathways to suppress tumor survival in oxygen poor microenvironments.

Oxidored-nitro domain containing protein 1 (NOR1) expression suppresses slug/vimentin but not snail in nasopharyngeal carcinoma: Inhibition of EMT in vitro and in vivo in mice

Oxidored-nitro domain containing protein 1 (NOR1) is a putative tumor suppressor gene. In this study, NOR1 expression was detected in NPC tissues and non-cancerous nasopharyngeal epithelium. The data showed that NOR1 protein was decreased in NPC tissues. Lost expression NOR1 protein was associated with poor overall and event-free survival of NPC patients. Overexpression of NOR1 in NPC cells resulted in a significant morphological change and decreased expression of epithelial-to-mesenchymal transition (EMT) mediators (e.g., slug and vimentin), but induced cytokeratin 13 expression. A nude mouse metastasis assay revealed that overexpression of NOR1 decreased NPC tumor cells metastasis capacity in vivo. Knockdown of NOR1 expression in HeLa cells was sufficient to abrogate epithelial traits and to enhance cell migration and invasion. Concomitant inhibition of slug or vimentin alleviated induction of EMT, migration or invasion by NOR1 siRNA in HeLa cells in vitro. In conclusion, the data from the current study suggest, for the first time, that NOR1 plays an important role in NPC in ex vivo, in vitro, and in vivo.

Tumor suppressor gene Oxidored-nitro domain-containing protein 1 regulates nasopharyngeal cancer cell autophagy, metabolism, and apoptosis in vitro

Autophagy is a cellular survival mechanism that involves the catabolic degradation of damaged proteins and organelles during stress. It is particularly required for tumor cell survival during starvation and tumorigenesis. NOR1 is a putative tumor suppressor gene. This study investigated in vitro the effects of NOR1 on the regulation of nasopharyngeal carcinoma autophagy, metabolism, and apoptosis. The data showed that acute oxidative stress induced the expression of NOR1 in normal human cells and tumor cells. Restoration of NOR1 expression downregulated basal autophagy, assessed by autophagy marker LC3 conversion and transmission electron microscopy. In NOR1-expressing tumor cells, reduced autophagy inhibited mitochondrial respiration and energy metabolism. Restoration of NOR1 expression in nasopharyngeal carcinoma cells enhanced apoptosis after induction of oxidative stress. NOR1 expression upregulated Bax expression, Bax translocation to the mitochondria, Smac/DIABLO release from the mitochondria, and activation of caspase-9, and -3, and PARP. In contrast, knockdown of NOR1 expression using NOR1 RNAi resulted in an increase in autophagy and attenuated hydrogen peroxide-induced cell death in HeLa cells. In addition, expression of NOR1 significantly inhibited cisplatin-induced autophagy, resulting in increased cisplatin cytotoxicity and apoptosis. These data revealed novel aspects of the interplay between autophagy and apoptosis in nasopharyngeal carcinoma cells, which underlies the tumor suppression function of NOR1. This work may provide novel insights to contribute to the development of a combinatorial therapy for nasopharyngeal carcinoma.

Overexpression of oxidored-nitro domain containing protein 1 inhibits human nasopharyngeal carcinoma and cervical cancer cell proliferation and induces apoptosis: Involvement of mitochondrial apoptotic pathways

Oxidored-nitro domain containing protein 1 (NOR1) is a novel member of the nitroreductase family that was first isolated as a tumor suppressor gene from human nasopharyngeal carcinoma (NPC). However, the role of NOR1 gene dysfunction in human cancers has not been addressed. We analyzed the expression of NOR1 in various human cancer and benign tissue specimens and found significant downregulation in nine types of cancer compared with corresponding non-tumor tissues. The recombinant expression vector pCDNA3.1-myc-his-NOR1 was constructed and transfected into human NPC 6-10B nasopharyngeal cancer and HeLa cervical cancer (CCA) cells. We found that stable NOR1 overexpression resulted in suppression of 6-10B and HeLa cell proliferation and led to S phase cell cycle arrest. In addition, NOR1 upregulation enhanced apoptosis in pCDNA3.1-myc-his-NOR1 stably transfected cells, and it also altered the expression of proteins involved in the mitochondria-dependent apoptotic pathway. Furthermore, we also found that the NOR1 protein is a cytoplasmic protein that is partially localized in the mitochondria and endoplasmic reticulum. Therefore, NOR1 is an important tumor suppressor gene associated with NPC and CCA and may play antitumor roles by inhibiting proliferation, preventing colony formation, and promoting the apoptosis of tumor cells via the mitochondrial-dependent apoptotic pathway. However, the precise mechanism behind the NOR1 antitumor effects needs to be investigated further.

Inhibition of Grb2-mediated activation of MAPK signal transduction suppresses NOR1/CB1954-induced cytotoxicity in the HepG2 cell line

The nitroreductase oxidored-nitro domain containing protein 1 (NOR₁) gene may be involved in the chemical carcinogenesis of hepatic cancer and nasopharyngeal carcinoma (NPC). We have previously demonstrated that NOR₁ overexpression is capable of converting the monofunctional alkylating agent 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) into a toxic form by reducing the 4-nitro group of CB1954. Toxic CB1954 is able to enhance cell killing in the NPC cell line CNE₁; however, the underlying mechanisms remain unknown. Using cDNA microarrays and quantitative real-time PCR, we previously discovered that NOR₁ increases the expression of growth factor receptor-bound protein 2 (Grb2) mRNA by 4.8-fold in the human hepatocellular carcinoma cell line HepG2. In the present study, we revealed that NOR₁ increased Grb2 protein expression by 3-fold in HepG2 cells. Additionally, we demonstrated that NOR₁ enhanced CB1954-induced cell killing in HepG2 cells, and cell cytotoxicity was inhibited with the tyrosine kinase inhibitor genistein, or by stable transfection of Grb2 small hairpin RNA (shRNA) pU6⁺²⁷-shGrb2 to silence the expression of Grb2. Western blot analysis revealed that Grb2 downregulation may reduce the activity of the mitogen-activated protein kinase (MAPK). Inhibiting the activation of MAPK using the methyl ethyl ketone (MEK) inhibtor PD98059 suppressed CB1954-induced cell killing. These results suggested that the NOR₁ gene enhances CB1954-mediated cell cytotoxicity through the upregulation of Grb2 expression and the activation of MAPK signal transduction in the HepG2 cell line.

Literature and patent analysis of the cloning and identification of human functional genes in China

The Human Genome Project was launched at the end of the 1980s. Since then, the cloning and identification of functional genes has been a major focus of research across the world. In China too, the potentially profound impact of such studies on the life sciences and on human health was realized, and relevant studies were initiated in the 1990s. To advance China's involvement in the Human Genome Project, in the mid-1990s, Committee of Experts in Biology from National High Technology Research and Development Program of China (863 Program) proposed the "two 1%" goal. This goal envisaged China contributing 1% of the total sequencing work, and cloning and identifying 1% of the total human functional genes. Over the past 20 years, tremendous achievement has been accomplished by Chinese scientists. It is well known that scientists in China finished the 1% of sequencing work of the Human Genome Project, whereas, there is no comprehensive report about "whether China had finished cloning and identifying 1% of human functional genes". In the present study, the GenBank database at the National Center of Biotechnology Information, the PubMed search tool, and the patent database of the State Intellectual Property Office, China, were used to retrieve entries based on two screening standards: (i) Were the newly cloned and identified genes first reported by Chinese scientists? (ii) Were the Chinese scientists awarded the gene sequence patent? Entries were retrieved from the databases up to the cut-off date of 30 June 2011 and the obtained data were analyzed further. The results showed that 589 new human functional genes were first reported by Chinese scientists and 159 gene sequences were patented (http://gene.fudan.sh.cn/introduction/database/chinagene/chinagene.html). This study systematically summarizes China's contributions to human functional genomics research and answers the question "has China finished cloning and identifying 1% of human functional genes?" in the affirmative.

NOR1 is an HSF1- and NRF1-regulated putative tumor suppressor inactivated by promoter hypermethylation in nasopharyngeal carcinoma

Promoter hypermethylation-mediated silencing of tumor suppressor genes (TSGs) is a hallmark of oncogenesis. Oxidored-nitro domain-containing protein 1 (NOR1) is a candidate TSG that is downregulated in nasopharyngeal carcinoma (NPC). In the present study, we identified a functional NOR1 promoter that is regulated by heat shock factor 1 and nuclear respiratory factor 1. The promoter is located within a CpG island. Hypermethylation of this CpG island was found in NPC tissue samples and cancer cell lines, whereas no aberrant promoter methylation was detected in non-cancerous nasopharyngeal tissue samples or normal nasopharyngeal epithelial cells. Treatment of NPC 6-10B cells and leukemia HL60 cells with 5'-aza-2'-deoxycytidine increased endogenous levels of NOR1 messenger RNA. Ectopic expression of NOR1 in NPC HNE1 cells inhibited tumor cell colony formation and viability. These findings suggest that promoter hypermethylation may participate in transcriptional inactivation of the NOR1 gene in NPC. Frequent epigenetic inactivation of the NOR1 gene in NPC suggests that it may be a critical tumor suppressor involved in the development of NPC.

Aberrant DNA methylation is associated with disease progression, resistance to imatinib and shortened survival in chronic myelogenous leukemia

The epigenetic impact of DNA methylation in chronic myelogenous leukemia (CML) is not completely understood. To elucidate its role we analyzed 120 patients with CML for methylation of promoter-associated CpG islands of 10 genes. Five genes were identified by DNA methylation screening in the K562 cell line and 3 genes in patients with myeloproliferative neoplasms. The CDKN2B gene was selected for its frequent methylation in myeloid malignancies and ABL1 as the target of BCR-ABL translocation. Thirty patients were imatinib-naïve (mostly treated by interferon-alpha before the imatinib era), 30 were imatinib-responsive, 50 were imatinib-resistant, and 10 were imatinib-intolerant. We quantified DNA methylation by bisulfite pyrosequencing. The average number of methylated genes was 4.5 per patient in the chronic phase, increasing significantly to 6.2 in the accelerated and 6.4 in the blastic phase. Higher numbers of methylated genes were also observed in patients resistant or intolerant to imatinib. These patients also showed almost exclusive methylation of a putative transporter OSCP1. Abnormal methylation of a Src suppressor gene PDLIM4 was associated with shortened survival independently of CML stage and imatinib responsiveness. We conclude that aberrant DNA methylation is associated with CML progression and that DNA methylation could be a marker associated with imatinib resistance. Finally, DNA methylation of PDLIM4 may help identify a subset of CML patients that would benefit from treatment with Src/Abl inhibitors.

Preparation of polyclonal antibody specific for NOR1 and detection of its expression pattern in human tissues and nasopharyngeal carcinoma

Oxidored-nitro domain containing protein 1 (NOR1) gene is a novel nitroreductase gene first isolated from nasopharyngeal carcinoma (NPC). It plays an important role in the formation of chemical carcinogen and the carcinogenesis of NPC for its nitrosation function. Overexpression of the wild-type NOR1 gene in nasopharyngeal carcinoma cells is effective to inhibit cell growth and proliferation. In this study, for the first time, we generated a highly specific NOR1 antibody and analyzed NOR1 distribution in the human tissues and NPC biopsies. The results showed that NOR1 protein is predominantly expressed in human nasopharynx and tracheal tissues. Human heart, liver, spleen, stomach, colon, kidney, skeletal muscle, thymus, and pancreas are all deficient of NOR1 protein. More importantly, we performed immunohistochemistry assay of NOR1 protein expression in the NPC tissues, and the result showed that NOR1 protein is frequently down-expressed in NPC. These data shed light on the selectivity of potential physiological functions of NOR1 and provides an indispensable reference to the carcinogenesis process of NPC and to identify or validate tissue-specific drug targets.

Intratesticular localization of the organic solute carrier protein, OSCP1, in spermatogenic cells in mice

Organic solute carrier protein 1 (OSCP1) is a recently described human gene that facilitates the transport of various organic solutes into the cell, when expressed in frog eggs. In this study, we cloned a mouse ortholog of OSCP1 encoding 379 amino acid protein, with 94% homology to the human counterpart. The mouse OSCP1 mRNA was predominantly expressed in the testis, in which it was attributed to the spermatogenic cells, except the spermatogonia. Immunohistochemistry confirmed that OSCP1 protein is continuously expressed during spermatogenesis in a stage- and cell type-specific manner, in the leptotene spermatocytes at stage IX through step 15 spermatids. Subcellular fractionation of mouse testis homogenates indicated that OSCP1 is a 45-kDa cytosolic protein. Moreover, when green fluorescent protein-OSCP1 fusion constructs were transfected into cultured cells, the fluorescence localized evenly in the cytoplasm. These results suggest that mouse testis OSCP1 may indirectly mediate substrate uptake into meiotic and spermiogenic germ cells, within the cytosol.

Downregulated NM23-H1 expression is associated with intracranial invasion of nasopharyngeal carcinoma

Because the focus of nasopharyngeal carcinoma (NPC) is very close to intracranial organs, it often makes incursions into cranial cavity. Identification of intracranial invasion-associated indicators will provide potential therapeutic targets for NPC patients with intracranial invasion. In this regard, Human Xpro™ HC-plus cancer-related gene chip was utilised to screen intracranial invasion-associated genes for NPC from the biopsied primary focus tissue samples. In all, 8 upregulated and 23 downregulated genes were obtained. VEGF165 and MMP-9, the two upregulated genes, and NM23-H1, the downregulated one, were further confirmed by immunohistochemistry, quantitative real-time PCR and western blot. Invasion-associated cellular and nude mouse models were subsequently employed to study the biological properties of NM23-H1. NM23-H1 expression was significantly lower in 5-8F cells compared with that in 6-10B cells. Moreover, patch-clamp and transwell chamber were adopted to investigate the invading potential-associated biological dynamic mechanisms in the two cell lines, and Ca²⁺ current and motility were significantly elevated in 5-8F cells compared with that in 6-10B cells. Berberine, an inhibitor of Ca²⁺ current, could substantially increase the expression of NM23-H1 and decrease 5-8F cell motility. The specificity of berberine on NM23-H1 and cell motility was confirmed by RNAi assay.