Preparation and characterization of a specific monoclonal antibody against CIAPIN1

Ribonucleotide reductase metallocofactor: assembly, maintenance and inhibition

Ribonucleotide reductase (RNR) supplies cellular deoxyribonucleotide triphosphates (dNTP) pools by converting ribonucleotides to the corresponding deoxy forms using radical-based chemistry. Eukaryotic RNR comprises α and β subunits: α contains the catalytic and allosteric sites; β houses a diferric-tyrosyl radical cofactor (FeIII2-Y•) that is required to initiates nucleotide reduction in α. Cells have evolved multi-layered mechanisms to regulate RNR level and activity in order to maintain the adequate sizes and ratios of their dNTP pools to ensure high-fidelity DNA replication and repair. The central role of RNR in nucleotide metabolism also makes it a proven target of chemotherapeutics. In this review, we discuss recent progress in understanding the function and regulation of eukaryotic RNRs, with a focus on studies revealing the cellular machineries involved in RNR metallocofactor biosynthesis and its implication in RNR-targeting therapeutics.

Crystal structure of the N-terminal methyltransferase-like domain of anamorsin

Anamorsin is a recently identified molecule that inhibits apoptosis during hematopoiesis. It contains an N-terminal methyltransferase-like domain and a C-terminal Fe-S cluster motif. Not much is known about the function of the protein. To better understand the function of anamorsin, we have solved the crystal structure of the N-terminal domain at 1.8 Å resolution. Although the overall structure resembles a typical S-adenosylmethionine (SAM) dependent methyltransferase fold, it lacks one α-helix and one β-strand. As a result, the N-terminal domain as well as the full-length anamorsin did not show S-adenosyl-L-methionine (AdoMet) dependent methyltransferase activity. Structural comparisons with known AdoMet dependent methyltransferases reveals subtle differences in the SAM binding pocket that preclude the N-terminal domain from binding to AdoMet. The N-terminal methyltransferase-like domain of anamorsin probably functions as a structural scaffold to inhibit methyl transfers by out-competing other AdoMet dependant methyltransferases or acts as bait for protein-protein interactions.

A monoclonal antibody against GPNMB

As a melanosome-associated transmembrane glycoprotein, GPNMB plays an important role in numerous cell types, as well as in tumors. Producing a high specificity and affinity monoclonal antibody against human GPNMB provides an important tool to study the function of GPNMB protein. In this study, monoclonal antibodies to GPNMB were obtained by immunizing BALB/c mice with purified GST-GPNMB emulsified in Freund's adjuvant. Three monoclonal antibodies with high specificity and affinity were obtained. The titers of anti-serum were 1:10,000, 1:8000, and 1:3000, respectively. Western blot and immunohistochemistry experiments were used to characterize the antibody. The anti-GPNMB antibodies G203 and F105 had high affinities (G203 around 2.7 × 10(-8) M and F105 around 1.6 × 10(-8) M, respectively) for the GPNMB antigen. However, M306 had a low binding activity to GPNMB. The results of Western blot and immunohistochemistry experiments showed that the antibodies could bind human GPNMB antigen. The monoclonal antibodies provided good tools for further studying functional characterization of GPNMB.

CIAPIN1 nuclear accumulation predicts poor clinical outcome in epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) is an aggressive disease with poor prognosis. The expression of cytokine-induced apoptosis inhibitor 1 (CIAPIN1) correlates with the malignant progression of several cancers. However, the relationship between the subcellular localization of CIAPIN1 and clinical characteristics in EOC remains unclear.

Methods

Immunohistochemistry was performed to detect CIAPIN1 expression in 108 EOC tissues. CIAPIN1 expressions in eight fresh EOC tissues were detected by Western blotting. The relationship between CIAPIN1 subcellular expression and patients’ clinicopathological features, including prognosis, was evaluated. Immunohistochemistry and immunofluorescence were employed to assess the CIAPIN1 subcellular localization in the EOC cell lines A2780 and HO8910. In addition, all patients were followed up to assess the prognostic value of CIAPIN1 in patients with EOC.

Results

CIAPIN1 is highly expressed in EOC, but is present at low levels in paired non-cancerous ovarian epithelial tissues. The results of Western blotting were in accordance with the immunohistochemical results. Poor differentiation of the tumors and EOC cell lines correlated with higher levels of CIAPIN1 nuclear expression. CIAPIN1 nuclear expression significantly correlated with the Federation International of Gynecology and Obstetrics (FIGO) stage and histological differentiation (P = 0.034 and P < 0.0001, respectively). Moreover, nuclear localization of CIAPIN1 was selected as an unfavorable prognostic factor by both univariate and multivariate analyses ( P < 0.001). However, no significant correlations were observed between cytoplasmic localization of CIAPIN1 and clinicopathological parameters.

Conclusions

CIAPIN1 might play a crucial role in the differentiation of EOC cells. Elevated expression of nuclear CIAPIN1 negatively correlated with the survival of EOC patients, suggesting that nuclear CIAPIN1 might serve as a prognostic biomarker for EOC patients.

Secretome Analysis of Skeletal Myogenesis Using SILAC and Shotgun Proteomics

Myogenesis, the formation of skeletal muscle, is a multistep event that commences with myoblast proliferation, followed by cell-cycle arrest, and finally the formation of multinucleated myotubes via fusion of mononucleated myoblasts. Each step is orchestrated by well-documented intracellular factors, such as cytoplasmic signalling molecules and nuclear transcription factors. Regardless, the key step in getting a more comprehensive understanding of the regulation of myogenesis is to explore the extracellular factors that are capable of eliciting the downstream intracellular factors. This could further provide valuable insight into the acute cellular response to extrinsic cues in maintaining normal muscle development. In this paper, we survey the intracellular factors that respond to extracellular cues that are responsible for the cascades of events during myogenesis: myoblast proliferation, cell-cycle arrest of myoblasts, and differentiation of myoblasts into myotubes. This focus on extracellular perspective of muscle development illustrates our mass spectrometry-based proteomic approaches to identify differentially expressed secreted factors during skeletal myogenesis.

Decreased expression of CIAPIN1 is correlated with poor prognosis in patients with esophageal squamous cell carcinoma

BACKGROUND

CIAPIN1, a newly identified antiapoptotic molecule, is a downstream effector of the receptor tyrosine kinase-Ras signaling pathway in the mouse Ba/F3 pro-B cell line. Neither CIAPIN1 expression nor its clinical significance has been previously examined in esophageal squamous cell carcinoma (ESCC), and the present immunohistochemical analysis is the first study on CIAPIN1 distribution in ESCC.

AIMS

To investigate the relationships between the expression of CIAPIN1 and clinicopathological characteristics of ESCC, and evaluate the relationship between the expression of this gene and prognosis in ESCC patients.

METHODS

The expression of CIAPIN1 was investigated in 112 surgically resected specimens of ESCC by immunohistochemistry using a specific monoclonal antibody. The relations of CIAPIN1 expression with clinicopathological characteristics and the postoperative survival rate were statistically analyzed.

RESULTS

We found that the expression of CIAPIN1 was statistically correlated with the degree of differentiation, depth of invasion, and lymph node metastasis of ESCC. Consistently, the survival rates of patients with CIAPIN1-negative tumors tended to be statistically lower than those with CIAPIN1-positive tumors. However, no significant difference was observed between CIAPIN1 expression and the patient age, sex, tumor location, and distant metastasis. Furthermore, multivariate analysis was performed by using Cox's proportional hazards model, and the results showed that lymph node metastases and CIAPIN1 expression were two independent prognostic factors.

CONCLUSIONS

CIAPIN1 might play an important role in esophageal carcinogenesis, and it could be considered as a valuable prognostic indicator in ESCC. Finally, functional enhancement of CIAPIN1 might lead to a novel strategy for the treatment of SCC in the esophagus.

CIAPIN1 inhibits the growth and proliferation of clear cell renal cell carcinoma

Our previous studies indicated a direct correlation with loss of CIAPIN1 and carcinogenesis of tumor in human gastric cancer. Here we presented that the expression of CIAPIN1 was absent or significantly decreased in 102 cases of clear cell renal cell carcinoma (CCRCC) tissues (P<0.05). Up-regulating CIAPIN1 by adenoviral vectors exhibited significant inhibition of CCRCC-derived cell growth in vitro and in vivo with G1 cell cycle arrest. Simultaneously, CIAPIN1-induced growth suppression was found partially to regulate various proteins, including inhibition of cyclinD1, cyclinE, cdk2, cdk4, p-Rb and VEGF, but up-regulation of p27Kip1 and Rb.

Identification of TRAK1 (Trafficking protein, kinesin-binding 1) as MGb2-Ag: a novel cancer biomarker

The present study aimed to describe the characterization of an antibody MGb2 that reacts with an epitope on gastric cancer cells, and identification of MGb2 antigen (MGb2-Ag). Immunostaining revealed its distribution in human tissues and demonstrated that the positive rate of MGb2-Ag was 81.48% in gastric cancer, 100% in gastric signet-ring cell carcinoma and mucinous adenocarcinoma, 13.16% in precancerous conditions, and 0% in chronic superficial gastritis. Using Western blotting, immunoprecipitation and MALDI-TOF MS (matrix assisted laser desorption/ionization time-of-flight mass spectrometry), MGb2-Ag was identified as TRAK1 (Trafficking protein, kinesin-binding 1), a new molecular gained limited recognition. Both MGb2 and commercial anti-TRAK1 Ab recognized prokaryotic expressed TRAK1. Immunostaining characteristics of TRAK1 were identical with MGb2-Ag in continuous sections of paraffin-embedded tissues of gastric tissues. This is the first report that TRAK1/MGb2-Ag is a promising diagnostic marker for gastric cancer and may help to detect signet-ring cell carcinoma and mucinous adenocarcinoma.

A new apoptosis inhibitor, CIAPIN1 (cytokine-induced apoptosis inhibitor 1), mediates multidrug resistance in leukemia cells by regulating MDR-1, Bcl-2, and Bax

We investigated the role of cytokine-induced apoptosis inhibitor 1 (CIAPIN1), a newly identified apoptosis inhibitor, in leukemia cell multidrug resistance (MDR) and its possible underlying mechanisms. CIAPIN1 was found to be overexpressed at the mRNA and protein levels in the vincristine-induced multidrug-resistant leukemia cell line HL-60/VCR, compared with HL-60, its parental cell line. In this study, we transfected HL-60 with a eukaryotic expression vector of CIAPIN1. In vitro drug sensitivity assays suggested that HL-60-CIAPIN1 cells conferred resistance to both P-glycoprotein (P-gp)-related and -unrelated drugs. Blocking CIAPIN1 expression in HL-60/VCR cells by CIAPIN1-specific small interfering RNA increased the cells' sensitivity to various chemotherapeutic drugs. Flow cytometry results suggested that CIAPIN1 expression could suppress adriamycin-induced apoptosis, accompanied by a decreased accumulation and increased release of adriamycin. Semiquantitative RT-PCR, Western blot analysis, and luciferase reporter assays suggested that CIAPIN1 could significantly upregulate the expression of MDR-1 and Bcl-2, the transcription of the MDR-1 gene, as well as downregulate the expression of Bax. Additionally, the inhibition of CIAPIN1 expression by RNA interference or P-gp inhibitor could partially reverse CIAPIN1-mediated MDR. Taken together, our findings suggest that downregulating CIAPIN1 could sensitize leukemia cells to chemotherapeutic drugs by downregulating MDR-1 and Bcl-2 and by upregulating Bax, yet not altering either glutathione-S-transferase activity or intracellular glutathione content in leukemia cells. Further study of CIAPIN1's function may reveal more of the mechanisms of leukemia MDR and result in the development of strategies to treat leukemia.

Adenovirus-delivered CIAPIN1 small interfering RNA inhibits HCC growth in vitro and in vivo

Hepatocellular carcinoma (HCC) is an aggressive cancer with a poor prognosis. The specific cellular gene alterations responsible for hepatocarcinogenesis are not well known. Cytokine-induced antiapoptotic molecule (CIAPIN1), a recently reported antiapoptotic molecule which plays an essential role in mouse definitive hematopoiesis, is considered a downstream effecter of the receptor tyrosine kinase–Ras signaling pathway. However, the exact function of this gene in tumors is not clear. In this study, we reported that CIAPIN1 is highly expressed in HCC as compared with non-tumor hepatic tissue (P < 0.05). We employed adenovirus-mediated RNA interference technique to knock down CIAPIN1 expression in HCC cells and observed its effects on HCC cell growth in vitro and in vivo. Among the four HCC and one normal human liver cell lines we analyzed, CIAPIN1 was highly expressed in HCC cells. Knock down of CIAPIN1 could inhibit HCC cell proliferation by inhibiting the cell cycle S-phase entry. Soft agar colony formation assay indicated that the colony-forming ability of SMMC-7721 cells decreased by ∼70% after adenovirus AdH1-small interfering RNA (siRNA)/CIAPIN1 infection. In vivo experiments showed that adenovirus AdH1-siRNA/CIAPIN1 inhibited the tumorigenicity of SMMC-7721 cells and significantly suppressed tumor growth when injected directly into tumors. These results suggest that knock down of CIAPIN1 by adenovirus-delivered siRNA may be a potential therapeutic strategy for treatment of HCC in which CIAPIN1 is overexpressed.

Successful expression and purification of human CIAPIN1 in baculovirus-insect cell system and application of this system to investigation of its potential methyltransferase activity

CIAPIN1 is a newly identified anti-apoptosis molecule which plays an important role in definitive haematopoiesis in mouse fetal liver and confers multidrug resistance in gastric cancer cells. However, the biophysical function of CIAPIN1 is far from elucidated. Bioinformatics predicts that CIAPIN1 may contain a generic methyltransferase motif and a Zn-ribbon-like motif. Based on these data, we postulated that CIAPIN1 might be a DNA or RNA methyltransferase. To substantiate this proposal, recombinant human CIAPIN1 (rhCIAPIN1) was expressed by a baculovirus-insect cell system and purified by Ni-NTA affinity chromatography. In vitro DNA and RNA methyltransferring tests, DNA demethylation test and S-adenosyl-l-[methyl-3H]methionine (3H-AdoMet) binding test were carried out. Our experiments failed to demonstrate that rhCIAPIN1 had any DNA, RNA methyltransferase activity, DNA demethylase activity, or had the capability of binding AdoMet in vitro. Further studies are needed to definitely clarify whether CIAPIN1 has methyltransferase activity.

Preparation and characterization of four novel monoclonal antibodies specific to N51(L6)C46 polypeptide simulating fusogenic core structure of GP41 subunit of HIV-1

We have generated monoclonal antibodies (MAbs) against the N51(L6)C46 polypeptide, which could stimulate the fusogenic core structure of the gp41 subunit of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein. Hybridomas were screened by indirect enzyme-linked immunosorbent assay (ELISA) using either N51(L6)C46 or N36(L6)C34 polypeptide. The MAb against N36(L6)C34, NC-1, was used as positive control, and N36 C34 peptides as negative controls. As a result, we generated four MAbs, three (1A2, 1A4, 1B9) against the polypeptide N51(L6)C46 monomer and one against the trimer, named 3A1. The four anti- N51(L6)C46 MAbs could bind N51(L6)C46 and N36(L6)C34 but not N36 or C34. The results of epitope analysis with competitive ELISA showed that the MAbs could recognize the similar epitopes, whereas the difference lie in that 3A1 could recognize the epitopes similar to NC-1s, whereas NC-1 could not recognize the epitopes similar to 3A1s. Taken together, these MAbs would be effective tools in selecting anti-HIV polypeptide and analyzing the characteristics of gp41 epitopes.

Subcellular localization of CIAPIN1

Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) is a newly identified anti-apoptotic molecule. Our previous studies have demonstrated that CIAPIN1 is ubiquitously expressed in normal fetal and adult human tissues and confers multidrug resistance in gastric cancer cells, possibly by upregulating the expression of multidrug resistance gene 1 and multidrug resistance-related protein 1. However, fundamental biological functions of CIAPIN1 have not been elucidated. In this study, we first predicted the subcellular localization of CIAPIN1 with bioinformatic approaches and then characterized the intracellular localization of CIAPIN1 in both human and mouse cells by a combination of techniques including (a)immunohistochemistry and immunofluorescence, (b) His-tagged CIAPIN1 expression, and (c)subcellular fractionation and analysis of CIAPIN1 in the fractions by Western blotting. All methods produced consistent results; CIAPIN1 was localized in both the cytoplasm and the nucleus and was accumulated in the nucleolus. Bioinformatic prediction disclosed a putative nuclear localization signal and a putative nuclear export signal within both human and mouse CIAPIN1. These findings suggest that CIAPIN1 may undergo a cytoplasm-nucleus-nucleolus translocation.

Distribution of CIAPIN1 in normal fetal and adult human tissues

CIAPIN1, a newly identified antiapoptotic molecule that plays an essential role in mouse definitive hematopoiesis, is considered a downstream effector of the receptor tyrosine kinase-Ras signaling pathway. Our previous studies have indicated that CIAPIN1 is involved in the development of multidrug resistance (MDR) in gastric cancer cells. However, the mechanism of CIAPIN1-mediated antiapoptosis and MDR has not been fully elucidated. To reveal the possible physiological role of CIAPIN1, we examined the expression and distribution of CIAPIN1 in fetal and adult human tissues using immunohistochemistry. We found that CIAPIN1 was ubiquitously distributed in fetal and adult tissues, and was localized in both the cytoplasm and the nucleus. The expression patterns of CIAPIN1 were similar in fetal and adult tissues, and was correlated with the previously described expression pattern of p21ras. These observations suggest that CIAPIN1 expression appears to be involved in cell differentiation, and that it might exert universal and possibly important physiological functions under the regulation of Ras in humans.