Nanog, as a key cancer stem cell marker in tumor progression

Cancer stem cells (CSCs) are a small population of malignant cells that induce tumor onset and development. CSCs share similar features with normal stem cells in the case of self-renewal and differentiation. They also contribute to chemoresistance and metastasis of cancer cells, leading to therapeutic failure. To identify CSCs, multiple cell surface markers have been characterized, including Nanog, which is found at high levels in different cancers. Recent studies have revealed that Nanog upregulation has a substantial association with the advanced stages and poor prognosis of malignancies, playing a pivotal role through tumorigenesis of multiple human cancers, including leukemia, liver, colorectal, prostate, ovarian, lung, head and neck, brain, pancreatic, gastric and breast cancers. Nanog through different signaling pathways, like JAK/STAT and Wnt/β-catenin pathways, induces stemness, self-renewal, metastasis, invasiveness, and chemoresistance of cancer cells. Some of these signaling pathways are common in various types of cancers, but some have been found in one or two cancers. Therefore, this review aimed to focus on the function of Nanog in multiple cancers based on recent studies surveying the suitable approaches to target Nanog and inhibit CSCs residing in tumors to gain favorable results from cancer treatments.

Using machine learning to predict ovarian cancer

OBJECTIVE

Ovarian cancer (OC) is one of the most common types of cancer in women. Accurately prediction of benign ovarian tumors (BOT) and OC has important practical value.

METHODS

Our dataset consists of 349 Chinese patients with 49 variables including demographics, blood routine test, general chemistry, and tumor markers. Machine learning Minimum Redundancy - Maximum Relevance (MRMR) feature selection method was applied on the 235 patients' data (89 BOT and 146 OC) to select the most relevant features, with which a simple decision tree model was constructed. The model was tested on the rest of 114 patients (89 BOT and 25 OC). The results were compared with the predictions produced by using the risk of ovarian malignancy algorithm (ROMA) and logistic regression model.

RESULTS

Eight notable features were selected by MRMR, among which two were identified as the top features by the decision tree model: human epididymis protein 4 (HE4) and carcinoembryonic antigen (CEA). Particularly, CEA is a valuable marker for OC prediction in patients with low HE4. The model also yields better prediction result than ROMA.

CONCLUSION

Machine learning approaches were able to accurately classify BOT and OC. Our goal is to derive a simple predictive model which also carries a good performance. Using our approach, we obtained a model that consists of just two biomarkers, HE4 and CEA. The model is simple to interpret and outperforms the existing OC prediction methods. It demonstrates that the machine learning approach has good potential in predictive modeling for the complex diseases.

Peri-Transplant Change in AFP Level: a Useful Predictor of Hepatocellular Carcinoma Recurrence Following Liver Transplantation

Pretransplant alpha-fetoprotein (AFP) is a useful tumor marker predicting recurrence of hepatocellular carcinoma (HCC). Little is known, however, about the relationship between changes in AFP concentration and prognosis. This study investigated the clinical significance of change in peri-transplant AFP level as a predictor of HCC recurrence. Data from 125 HCC patients with elevated pretransplant AFP level who underwent liver transplantation (LT) between February 2000 and December 2010 were retrospectively reviewed. Patients with AFP normalization within 1 month after LT were classified into the rapid normalization group (n = 97), with all other patients classified into the non-rapid normalization group (n = 28). Tumor recurrence was observed in 17 of the 97 patients (17.5%) with rapid normalization; of these, 11 patients had high AFP levels and six had normal levels at recurrence. In contrast, tumor recurrence was observed in 24 of the 28 patients (85.7%) without rapid normalization, with all 24 having high AFP levels at recurrence. Multivariate analysis showed that non-rapid normalization (harzard ratio [HR], 4.41, P < 0.001), sex (HR, 3.26, P = 0.03), tumor size (HR, 1.15, P = 0.001), and microvascular invasion (HR, 2.65, P = 0.005) were independent risk factors for recurrence. In conclusion, rapid normalization of post-LT AFP level at 1 month is a useful clinical marker for HCC recurrence. Therefore, an adjuvant strategy and/or intensive screening are needed for patients who do not show rapid normalization.

Diagnostic value of combined detection of serum C-reactive protein and tumor markers in elderly patients with gastrointestinal tumors

AIM: To investigate the diagnostic value of C-reactive protein (CRP) and tumor markers in elderly patients with gastrointestinal tumors.

METHODS: CRP, carcino-embryonic antigen (CEA), antigen 125 (CA 125), antigen 19-9 (CA19-9), and alpha-fetoprotein (AFP) were detected in 79 elderly gastrointestinal tumor patients and 30 healthy controls. The diagnostic sensitivity and specificity of these indexes, alone or combination of any two, were calculated.

RESULTS: Serum levels of CRP, CEA, CA19-9, CA125, and AFP in gastrointestinal tumor patients were significantly higher than those in the normal control group. The sensitivities of CRP, CEA, CA19-9, CA125, and AFP were 64.56%, 26.58%, 49.37%, 37.97%, and 12.70%, respectively. The sensitivities of combined assay of CRP and CEA, CRP and CA125, and CRP and AFP were 73.98%, 78.00% and 67.3%, respectively, which were higher than those of any single tumor markers.

CONCLUSION: The detection of CRP, combined with other tumor markers, plays an important role in the early diagnosis of gastrointestinal tumors in elderly patients.

Preoperative CA 125 is significant indicator of curative resection in gastric cancer patients

AIM: To investigate the correlation among tumor markers, curative resection, and recurrence in gastric cancer.

METHODS: The patients with preoperative tumor makers [Carcinoembryonic antigen, Carbohydrate antigen (CA) 19-9, and CA 125] and elective gastrectomy between January 2000 and December 2009 at Chungbuk National University Hospital were enrolled in this study. We analyzed the relationship among the tumor makers, curative resection and recurrence, retrospectively.

RESULTS: Among the 679 patients with gastric cancer, curative resection was 93.6% (n = 636) and non-curative resection was 6.4% (n = 43). The independent risk factors for the non-curative resection were tumor location and the positivity of preoperative serum CA 19-9 and CA 125 levels. After curative resection, the independent prognostic risk factors for recurrence in curative resection were gender, stage, and preoperative increased serum CA 125 level (HR = 2.431, P =0.020), in a multivariate analysis.

CONCLUSION: Preoperative CA 125 is a useful predictive biomarker for curative resection and prognostic biomarker for recurrence in gastric cancer patients.

A unified mechanism for aminopeptidase N-based tumor cell motility and tumor-homing therapy

Tumor cell surface aminopeptidase N (APN or CD13) has two puzzling functions unrelated to its enzymatic activity: mediating tumor cell motility and serving as a receptor for tumor-homing peptides (peptides that bring anti-cancer drugs to tumor cells). To investigate APN-based tumor-homing therapy, we determined the crystal structure of APN complexed with a tumor-homing peptide containing a representative Asn-Gly-Arg (NGR) motif. The tumor-homing peptide binds to the APN enzymatic active site, but it resists APN degradation due to a distorted scissile peptide bond. To explore APN-based tumor cell motility, we examined the interactions between APN and extracellular matrix (ECM) proteins. APN binds to, but does not degrade, NGR motifs in ECM proteins that share similar conformations with the NGR motif in the APN-bound tumor-homing peptide. Therefore, APN-based tumor cell motility and tumor-homing therapy rely on a unified mechanism in which both functions are driven by the specific and stable interactions between APN and the NGR motifs in ECM proteins and tumor-homing peptides. This study further implicates APN as an integrin-like molecule that functions broadly in cell motility and adhesion by interacting with its signature NGR motifs in the extracellular environment.

Translationally controlled tumor protein is a novel biological target for neurofibromatosis type 1-associated tumors

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease that predisposes individuals to develop benign neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs). Due to the lack of information on the molecular mechanism of NF1-associated tumor pathogenesis or biomarkers/therapeutic targets, an effective treatment for NF1 tumors has not been established. In this study, the novel NF1-associated protein, translationally controlled tumor protein (TCTP), was identified by integrated proteomics and found to be up-regulated via activated MAPK/PI3K-AKT signaling in response to growth factors in NF1-deficient Schwann cells. Immunohistochemical analysis of NF1-associated tumors revealed that the TCTP expression level correlated with tumorigenicity. In NF1-deficient MPNST cells, TCTP protein but not mRNA was down-regulated by NF1 GTPase-activating protein-related domain or MAPK/PI3K inhibitors, and this correlated with suppression of mammalian target of rapamycin (mTOR) signaling. mTOR inhibition by rapamycin also down-regulated TCTP protein expression, whereas knockdown or overexpression of TCTP suppressed or activated mTOR signaling, respectively, and affected cell viability. These results suggest that a positive feedback loop between TCTP and mTOR contributes to NF1-associated tumor formation. Last, the anti-tumor effect of artesunate, which binds to and degrades TCTP, was evaluated. Artesunate significantly suppressed the viability of MPNST cells but not normal Schwann cells, and the TCTP level inversely correlated with artesunate sensitivity. Moreover, combinational use of artesunate and rapamycin enhanced the cytotoxic effect on MPNST cells. These findings suggest that TCTP is functionally implicated in the progression of NF1-associated tumors and could serve as a biological target for their therapy.

Epithelial membrane protein-2 (EMP2) activates Src protein and is a novel therapeutic target for glioblastoma

Despite recent advances in molecular classification, surgery, radiotherapy, and targeted therapies, the clinical outcome of patients with malignant brain tumors remains extremely poor. In this study, we have identified the tetraspan protein epithelial membrane protein-2 (EMP2) as a potential target for glioblastoma (GBM) killing. EMP2 had low or undetectable expression in normal brain but was highly expressed in GBM as 95% of patients showed some expression of the protein. In GBM cells, EMP2 enhanced tumor growth in vivo in part by up-regulating αvβ3 integrin surface expression, activating focal adhesion kinase and Src kinases, and promoting cell migration and invasion. Consistent with these findings, EMP2 expression significantly correlated with activated Src kinase in patient samples and promoted tumor cell invasion using intracranial mouse models. As a proof of principle to determine whether EMP2 could serve as a target for therapy, cells were treated using specific anti-EMP2 antibody reagents. These reagents were effective in killing GBM cells in vitro and in reducing tumor load in subcutaneous mouse models. These results support the role of EMP2 in the pathogenesis of GBM and suggest that anti-EMP2 treatment may be a novel therapeutic treatment.

Novel ubiquitin-derived high affinity binding proteins with tumor targeting properties

Targeting effector molecules to tumor cells is a promising mode of action for cancer therapy and diagnostics. Binding proteins with high affinity and specificity for a tumor target that carry effector molecules such as toxins, cytokines, or radiolabels to their intended site of action are required for these applications. In order to yield high tumor accumulation while maintaining low levels in healthy tissues and blood, the half-life of such conjugates needs to be in an optimal range. Scaffold-based binding molecules are small proteins with high affinity and short systemic circulation. Due to their low molecular complexity, they are well suited for combination with effector molecules as well as half-life extension technologies yielding therapeutics with half-lives adapted to the specific therapy. We have identified ubiquitin as an ideal scaffold protein due to its outstanding biophysical and biochemical properties. Based on a dimeric ubiquitin library, high affinity and specific binding molecules, so-called Affilin® molecules, have been selected against the extradomain B of fibronectin, a target almost exclusively expressed in tumor tissues. Extradomain B-binding molecules feature high thermal and serum stability as well as strong in vitro target binding and in vivo tumor accumulation. Application of several half-life extension technologies results in molecules of largely unaffected affinity but significantly prolonged in vivo half-life and tumor retention. Our results demonstrate the utility of ubiquitin as a scaffold for the generation of high affinity binders in a modular fashion, which can be combined with effector molecules and half-life extension technologies.

Factors Associated with Serum Levels of Carcinoembryonic Antigen in Healthy Non-smokers

BACKGROUND

Carcinoembryonic antigen (CEA), a serological marker of malignant tumors, demonstrates a modest increase under nonmalignant conditions such as aging and smoking. Also, recent study results suggested that serum CEA levels may be related to insulin resistance or low-grade inflammation. The aim of this study was to investigate the factors associated with serum CEA levels in healthy non-smokers.

METHODS

Data was gathered from 21,501 adults aged 20 and over. We excluded 19,081 subjects who had omissions in anthropometric measurements or laboratory tests, or who had previous or current smoking history.

RESULTS

The mean CEA level was 1.18 ± 0.85 ng/dL in males and 0.93 ± 0.73 ng/dL in females. After adjustment for age, CEA level was positively correlated with fasting glucose, glycosylated hemoglobin (HbA1C), high density lipoprotein (HDL) cholesterol, estimated glomerular filtration rate in males. In females, CEA level was positively correlated with fasting glucose, HbA1C, HDL cholesterol, aspartate aminotransferase, and high-sensitivity C-reactive protein. In both gender groups, HbA1C had a strong influence on CEA levels when all other variables were included in the regression model (P < 0.05).

CONCLUSION

Within normal range, serum CEA levels were significantly associated with HbA1C levels but not with homeostasis model assessment of insulin resistance in the non-smoking population. These findings suggest that serum CEA levels are influenced by the glucose level itself instead of insulin resistance.

Heat shock protein 90-α mediates aldo-keto reductase 1B10 (AKR1B10) protein secretion through secretory lysosomes

Aldo-keto reductase 1B10 (AKR1B10) protein is a new tumor biomarker in humans. Our previous studies have shown that AKR1B10 is secreted through a lysosome-mediated nonclassical pathway, leading to an increase in the serum of breast cancer patients. This study illuminates the regulatory mechanism of AKR1B10 secretion. The cytosolic AKR1B10 associates with and is translocated to lysosomes by heat shock protein 90α (HSP90α), a chaperone molecule. Ectopic expression of HSP90α significantly increased the secretion of endogenous AKR1B10 and exogenous GFP-AKR1B10 fusion protein when cotransfected. Geldanamycin, a HSP90α inhibitor, dissociated AKR1B10-HSP90α complexes and significantly reduced AKR1B10 secretion in a dose-dependent manner. We characterized the functional domain in AKR1B10 and found that helix 10 (amino acids 233-240), located at the C terminus, regulates AKR1B10 secretion. Targeted point mutations recognized that amino acids Lys-233, Glu-236, and Lys-240 in helix 10 mediate the interaction of AKR1B10 with HSP90α. Together, our data suggest that HSP90α mediates AKR1B10 secretion through binding to its helix 10 domain. This finding is significant in exploiting the use of AKR1B10 in cancer clinics.

A soluble fragment of the tumor antigen BCL2-associated athanogene 6 (BAG-6) is essential and sufficient for inhibition of NKp30 receptor-dependent cytotoxicity of natural killer cells

Immunosurveillance of tumor cells depends on NKp30, a major activating receptor of human natural killer (NK) cells. The human BCL2-associated athanogene 6 (BAG-6, also known as BAT3; 1126 amino acids) is a cellular ligand of NKp30. To date, little is known about the molecular details of this receptor ligand system. Within the current study, we have located the binding site of NKp30 to a sequence stretch of 250 amino acids in the C-terminal region of BAG-6 (BAG-6(686-936)). BAG-6(686-936) forms a noncovalent dimer of 57-59 kDa, which is sufficient for high affinity interaction with NKp30 (KD < 100 nM). As our most important finding, BAG-6(686-936) inhibits NKp30-dependent signaling, interferon-γ release, and degranulation of NK cells in the presence of malignantly transformed target cells. Based on these data, we show for the first time that BAG-6(686-936) comprises a subdomain of BAG-6, which is sufficient for receptor docking and inhibition of NKp30-dependent NK cell cytotoxicity as part of a tumor immune escape mechanism. These molecular insights provide an access point to restore tumor immunosurveillance by NK cells and to increase the efficacy of cellular therapies.

Development of a Chemiluminescence Immunoassay for Serum YB-1 and its Clinical Application as a Potential Diagnostic Marker for Hepatocellular Carcinoma

BACKGROUND

Y-box binding protein 1 (YB-1) overexpression has been shown in various tumor cells including hepatocellular carcinoma (HCC); moreover, this protein can be actively secreted.

OBJECTIVES

The aim of this study was to establish a method to quantify serum YB-1 and evaluate its clinical application in the clinical diagnosis of HCC.

PATIENTS AND METHODS

Recombinant YB-1 and two populations of its antibodies were prepared. A monoclonal antibody was specific to the N-terminus of YB-1 amino acids 134-160; and another was a polyclonal antibody. A sandwich-type chemiluminescence immunoassay (CLIA) was developed and evaluated. Levels of YB-1 and alpha fetoprotein (AFP) in serum samples from 105 HCC patients, 25 hepatitis B virus patients, 25 cirrhosis patients, and 50 healthy donors were detected using the established method and an AFP electrochemiluminescence kit.

RESULTS

The developed method was linear to 150 μg/L of YB-1 with a minimum detection limit of 0.01 μg/L. The average recoveries were between 93.9% and 109.0%. The mean intra- and inter-assay coefficients of variation (CVs) were 4.0-4.8% and 8.2-10.2%, respectively. The relationship between the concentration of diluted YB-1 and the dilution ratios gave a good linear correlation coefficient of 0.9986. The YB-1 concentration was increased in serum of HCC patients (33.0 ± 23.39 μg/L) compared to healthy individuals (13.2 ± 5.29 μg/L, P < 0.0001), patients with HBV (17.9 ± 7.49 μg/L, P = 0.0003), and patients with HBV cirrhosis (20.7 ± 8.75 μg/L, P < 0.05). Moreover, the combination of YB-1 and alpha-fetoprotein had a high sensitivity (89.5%) and reasonable specificity (62.0%) in identifying HCC.

CONCLUSIONS

The established method has an acceptable performance in quantifying YB-1. In addition, serum YB-1 may aid in the diagnosis of HCC.

Recognition of the Thomsen-Friedenreich pancarcinoma carbohydrate antigen by a lamprey variable lymphocyte receptor

Variable lymphocyte receptors (VLRs) are leucine-rich repeat proteins that mediate adaptive immunity in jawless vertebrates. VLRs were recently shown to recognize glycans, such as the tumor-associated Thomsen-Friedenreich antigen (TFα; Galβ1-3GalNAcα), with a selectivity rivaling or exceeding that of lectins and antibodies. To understand the basis for TFα recognition by one such VLR (VLRB.aGPA.23), we measured thermodynamic parameters for the binding interaction and determined the structure of the VLRB.aGPA.23-TFα complex to 2.2 Å resolution. In the structure, four tryptophan residues form a tight hydrophobic cage encasing the TFα disaccharide that completely excludes buried water molecules. This cage together with hydrogen bonding of sugar hydroxyls to polar side chains explains the exquisite selectivity of VLRB.aGPA.23. The topology of the glycan-binding site of VLRB.aGPA.23 differs markedly from those of lectins or antibodies, which typically consist of long, convex grooves for accommodating the oligosaccharide. Instead, the TFα disaccharide is sandwiched between a variable loop and the concave surface of the VLR formed by the β-strands of the leucine-rich repeat modules. Longer oligosaccharides are predicted to extend perpendicularly across the β-strands, requiring them to bend to match the concavity of the VLR solenoid.

Ubiquitin C-terminal hydrolase L1 (UCH-L1) acts as a novel potentiator of cyclin-dependent kinases to enhance cell proliferation independently of its hydrolase activity

Dysregulation of cell proliferation and the cell cycle are associated with various diseases, such as cancer. Cyclin-dependent kinases (CDKs) play central roles in cell proliferation and the cell cycle. Ubiquitin C-terminal hydrolase L1 (UCH-L1) is expressed in a restricted range of tissues, including the brain and numerous types of cancer. However, the molecular functions of UCH-L1 remain elusive. In this study, we found that UCH-L1 physically interacts with CDK1, CDK4, and CDK5, enhancing their kinase activity. Using several mutants of UCH-L1, we showed that this enhancement is dependent upon interaction levels between UCH-L1 and CDKs but is independent of the known ubiquitin-related functions of UCH-L1. Gain- and loss-of-function studies revealed that UCH-L1 enhances proliferation of multiple cell types, including human cancer cells. Inhibition of the interaction between UCH-L1 and cell cycle-associated CDK resulted in the abolishment of UCH-L1-induced enhancement of cell proliferation. RNA interference of UCH-L1 reduced the growth of human xenograft tumors in mice. We concluded that UCH-L1 is a novel regulator of the kinase activities of CDKs. We believe that our findings from this study will significantly contribute to our understanding of cell cycle-associated diseases.