A Review: Proteomics in Nasopharyngeal Carcinoma

Recent Advances in Nasopharyngeal Cancer Management: From Diagnosis to Theranostics

Abstract:

Nasopharyngeal cancer (NPC) is one of the most common head and neck cancers. NPC differs significantly from other cancers in its etiology, epidemiology, clinical behavior, and treatment. Being highly radiosensitive, the standard treatment for NPC is radiotherapy. However, radioresistance hampers the success of treatment and may cause local recurrence and distant metastases in NPC patients. In this review, we discuss the updated protocols for NPC diagnosis and treatment based on recent literature with an emphasis on the mechanisms of radioresistance at the molecular level with a special focus on genetic and epigenetic events, affecting genes involved in xenobiotic detoxification and DNA repair. We also highlight the importance of some cellular and Epstein Barr viral miRNAs targeting specific DNA repair factors and consequently promoting NPC radioresistance. These molecular markers may serve as promising tools for diagnosis, prognosis, and radioresistance prediction to guide theranostics of patients with NPC in the future.

Kiss1 Inhibits the Proliferation of Nasopharyngeal Carcinoma Cells Via Activation of the LKB1/AMPK Pathway

Nasopharyngeal carcinoma (NPC) is a cancer that occurs in the nasopharynx. Infinite proliferation and distant metastasis are the main characteristics of NPC cells, and the main reason for the current failure of malignant tumor treatment. In this study, by integrating the immunohistochemical, cell transfection, western blot and real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis, we observed that the expression of KISS1 and its receptor gene (KISS1R) negatively related with the proliferation of NPC cells. Overexpression of the KISS1 genes in cells reduced cell proliferation, slow down the cell cycle, and increased apoptosis. Additionally, overexpression of these genes significantly increased Liver Kinase B1 (LKB1), phosphorylation of LKB1 and AMPK, indicated by Western blotting. Together, all of these results suggested for the first time that KISS1 and KISS1R suppress the proliferation of NPC cells by activating the LKB1/AMPK pathway, thus revealing a viable indicator for diagnosis of NPC in clinical practice.

Proteomics: Concepts and applications in human medicine

Proteomics is the complete evaluation of the function and structure of proteins to understand an organism’s nature. Mass spectrometry is an essential tool that is used for profiling proteins in the cell. However, biomarker discovery remains the major challenge of proteomics because of their complexity and dynamicity. Therefore, combining the proteomics approach with genomics and bioinformatics will provide an understanding of the information of biological systems and their disease alteration. However, most studies have investigated a small part of the proteins in the blood. This review highlights the types of proteomics, the available proteomic techniques, and their applications in different research fields.

Research status and prospects of biomarkers for nasopharyngeal carcinoma in the era of high‑throughput omics (Review)

As a malignant tumor type, nasopharyngeal carcinoma (NPC) is characterized by distinct geographical, ethnic and genetic differences; presenting a major threat to human health in many countries, especially in Southern China. At present, no accurate and effective methods are available for the early diagnosis, efficacious evaluation or prognosis prediction for NPC. As such, a large number of patients have locoregionally advanced NPC at the time of initial diagnosis. Many patients show toxic reactions to overtreatment and have risks of cancer recurrence and distant metastasis owing to insufficient treatment. To solve these clinical problems, high‑throughput '‑omics' technologies are being used to screen and identify specific molecular biomarkers for NPC. Because of the lack of comprehensive descriptions regarding NPC biomarkers, the present study summarized the research progress that has been made in recent years to discover NPC biomarkers, highlighting the existing problems that require exploration. In view of the lack of authoritative reports at present, study design factors that affect the screening of biomarkers are also discussed here and prospects for future research are proposed to provide references for follow‑up studies of NPC biomarkers.

Lectin affinity chromatography and quantitative proteomic analysis reveal that galectin-3 is associated with metastasis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a serious cancer in East and Southeast Asia. Patients are often diagnosed at advanced stages, rendering treatment failure due to high potential of metastasis. This study identified lectin-binding glycoproteins with a potential role in NPC metastasis. Cell lysate and culture medium in highly metastatic 5-8F, and lowly-metastatic 6-10B NPC cell lines were fractionated by ConA- and WGA-affinity chromatography, and subjected to GeLC-MS/MS. A total of 232 and 197 proteins were identified in ConA-enriched fraction of 5-8F and 6-10B cell lysates respectively. In WGA-enriched fraction, 65 and 164 proteins were found in 5-8F and 6-10B cell lysates respectively. Proteins identified in culture medium for both cell lines were 223 and 85 for ConA-enriched fraction, and 94 and 124 for WGA-enriched fraction from 5-8F and 6-10B respectively. Differentially expressed proteins were functionally categorized into cell–cell adhesion, extracellular matrix, glycolysis, protein homeostasis and/or glycosylation enzymes, and lipid metabolism. Interestingly, Galectin-3 (Gal-3) was highly expressed in 5-8F cells but was lowly expressed in 6-10B cells. The Gal-3 knockdown in 5-8F cells, Gal-3 overexpression in 6-10B cells and treatment with Gal-3 inhibitor revealed that Gal-3 was responsible for metastatic phenotypes including adhesion, migration and invasion. So Galectin-3 may serve as a potential target for NPC therapeutic interventions.

CLIC4 regulates radioresistance of nasopharyngeal carcinoma by iNOS after γ-rays but not carbon ions irradiation

Nasopharyngeal carcinoma (NPC) is a major health problem in the East and Southeast Asia, and the intensity modulated radiotherapy (IMRT) is the current preferred treatment method of NPC, but radioresistance-induced residual and recurrent tumors are the main cause of treatment failure. Till now, the mechanism of radioresistance and prognostic biomarkers of NPC are still unrevealed. In this study, we collected clinical NPC samples and established radioresistant NPC-R cell lines by irradiating NPC cells with fractionation doses of γ-rays. Using genechip assay between radioresistance and radiosensitive clinical samples and TMT assay between NPC and NPC-R cells, differential expressed genes were examined and the potential biomarker of radioresistance was screened. Immunohistochemical assay of NPC clinical specimens showed that CLIC4 was significantly up-regulated in radioresistance tumor tissues. In vitro studies confirmed that up-regulation of CLIC4 gene enhanced radioresistance in comparison with the alterations of intracellular oxidative metabolism of reactive oxygen species (ROS) and nitric oxide (NO) in an opposite way. Correspondingly, inhibition of CLIC4 sensitized NPC cells to irradiation and decreased nuclear translocation of iNOS and intracellular level of NO in NPC cells. Interestingly, the capacity for DNA repair had no difference between NPC and NPC-R cells. Moreover, because of great interests in using carbon ion irradiation to treat NPC effectively, we demonstrated that, after carbon ion irradiation, NPC-R and NPC cells had similar survival even under the status of up- or down-regulation of CLIC4. Conclusively, CLIC4 contributes to radioresistance of NPC to γ-rays but not carbon ions by regulating intracellular oxidative metabolism of nuclear translocation of iNOS.

Riluzole Enhances the Response of Human Nasopharyngeal Carcinoma Cells to Ionizing Radiation via ATM/P53 Signalling Pathway

Riluzole is approved by the FDA as an amyotrophic lateral sclerosis (ALS) drug. Previous studies showed that treatment with riluzole suppressed the proliferation of many cancer cells. However, little is known about its effects on nasopharyngeal carcinoma (NPC) and its molecular mode of action. In this study, we determined the effect of riluzole on apoptosis, cell cycle, migration, and invasion in NPC cell lines and investigated its mechanism at the molecular level. By using the human NPC cell lines CNE1, CNE2, and HNE1, we revealed that riluzole effectively inhibited viability of the NPC cell lines in dose- and time-dependent manners. Furthermore, riluzole dose-dependently induced apoptosis and G2/M cell cycle arrest in the NPC cell lines. After combination with radiotherapy (RT), greater cytotoxicity was achieved than with riluzole or RT alone in vitro and vivo. This was associated with the activation of ataxia telangiectasia mutated (ATM) and phosphoinositide p53 pathways. P53 silencing reduced cell reactiveness to riluzole therapy. These observations demonstrate that the riluzole-activated ATM/P53 pathway is directly involved in radiation-induced apoptosis of NPC cells. Given the acceptable side effect, combining of riluzole and radiotherapy is promising in NPC treatment.

Identification of the differentially expressed proteins in nasopharyngeal carcinoma by proteomics

Background

We sought to determine the differences with respect to the proteome of nasopharyngeal tissues between patients with nasopharyngeal carcinoma (NPC) and healthy controls by using sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH^TM-MS) and ingenuity pathway analysis (IPA). Our primary purpose was to identify specific protein markers that can be applied for diagnosis or treatment of NPC.

Methods

The CNE-1, CNE-2 and H1299 cell lines were cultured in stable isotope labeling of amino acids in cell culture (SILAC) medium for 10 generations to obtain labeled proteins. Thirty samples of NPC and 30 healthy control nasopharyngeal tissues were collected from the Department of Otolaryngology of the First Affiliated Hospital of Jinan University. Proteome of the nasopharyngeal tissues were analyzed and compared by SWATH-MS to identify differently expressed proteins. Further, extraction of target proteins and biological pathways was performed by IPA. Super-SILAC technique and liquid chromatography-tandem mass spectrometry were used to verify the reliability of the data obtained using SWATH-MS.

Results

We identified 1,415 differentially expressed proteins between NPC patients and healthy controls. On IPA analysis, EIF2AK2 and MAPK1 proteins were found to be enriched in multiple biological pathways and functional networks.

Conclusions

The differentially expressed proteins EIF2AK2 and MAPK seem to play an important role in the biological network of NPC or may help discover the specific functional proteins of NPC. Further studies are required to identify the pathways and molecular mechanisms that underlie NPC.

Amyloid Beta (A4) Precursor Protein: A Potential Biomarker for Recurrent Nasopharyngeal Carcinoma

Background and Aim

Nasopharyngeal carcinoma (NPC) is one of the most common cancers in Southern China, Southeast Asia. Radiotherapy is the main treatment for NPC. Still, about 20% of patients with NPC have a recurrence. No effective serum biomarkers are available for recurrent nasopharyngeal carcinoma (rNPC) to date. This study aimed to explore whether amyloid beta (A4) precursor protein (APP) might serve as a valuable diagnostic and prognostic biomarker for patients with rNPC.

Methods

In a previous study, a tandem mass tag–based proteomic test was performed, which screened 59 differentially expressed proteins (DEPs) between nonrecurrent nasopharyngeal carcinoma (nrNPC) and rNPC. In this study, a protein–protein interaction was conducted to screen the key proteins among the 59 DEPs. APP was validated and evaluated by enzyme-linked immunosorbent assay in 70 serum samples [recurrence (n = 35) and no-recurrence (n = 35)]. Also, the receiver operating characteristic (ROC) curve was plotted to evaluate the predictive value of APP.

Results

The area under the ROC curve was 0.666 (95% CI: 0.514–0.818, P = 0.044). The best cutoff point of the relative expression levels for APP was 1.23 (concentration = 16.95 ng/mL), at which the sensitivity was 55.2% and the specificity was 90.9%.

Conclusion

The findings indicated that APP might be a valuable diagnostic and prognostic biomarker for patients with rNPC.

Overexpression of ERBB3 promotes proliferation, migration, and angiogenesis in nasopharyngeal carcinoma

The purpose of this study is to investigate the role of ERBB3 in nasopharyngeal carcinoma (NPC). We investigated the expression level of ERBB3 in NPC by immunohistochemistry and western blot. CCK-8, cell cycle analysis, transwell assay and wound healing assay were used to detect the effect of ERBB3 on the proliferation and migration of NPC cells. HUVECs were used to study the effects of ERBB3 on angiogenesis in NPC. Our results showed that the expression level of ERBB3 in NPC was much higher than that in normal controls. ERBB3 promoted the proliferation and migration of NPC cells, while suppression of ERBB3 reduced angiogenesis. These results indicated that overexpression of ERBB3 promotes tumorigenesis and angiogenesis in NPC, which may provide an effective target in gene therapy for NPC.

Serum proteomics identify potential biomarkers for nasopharyngeal carcinoma sensitivity to radiotherapy

Radiotherapy is the primary treatment option for nasopharyngeal carcinoma (NPC). Local recurrence and metastasis caused by radioresistance become a bottleneck of curative effect for patients with NPC. Currently, serum predictive biomarkers of radioresistance are scare. We enrolled NPC patients, who underwent radiotherapy in the Department of Oncology, Xiangya Hospital, Central Southern University, and analyzed the serum proteins profiles in NPC patients using with quantitative label-free proteomics using ultra-definition MS. Patients were divided into those who were radioresistant and radiosensitive by the overall reduction (≤50% or >50%, respectively) in tumor extent. The MS/MS spectrum database search identified 911 proteins and 809 proteins are quantitatable. Eight proteins significantly up-regulated and 12 serum proteins were significantly down-regulated in the radioresistance group compared with radiosensitivity group (P<0.05). Finally, five proteins entered the optimal models, including secreted protein acidic and cysteine rich (SPARC) (P=0.032), serpin family D member 1S (ERPIND1) (P=0.040), complement C4B (C4B) (P=0.017), peptidylprolyl Isomerase B (PPIB) (P=0.042), and family with sequence similarity 173 member A (FAM173A) (P=0.017). In all patient, the area under the curves (AUC) for SPARC, SERPIND, C4B, PPIB, and FAM173A were 0.716 (95% CI: 0.574-0.881), 0.697 (95% CI: 0.837-0.858), 0.686 (95% CI: 0.522-0.850), 0.668 (95% CI: 0.502-0.834) and 0.657 (95% CI: 0.512-0.825), respectively. The AUC of five selected proteins was 0.968 (95% CI: 0.918-1.000) with the sensitivity of 0.941 and the specificity of 0.926. Our result indicated that a panel including five serum protein (SPARC SERPIND1 C4B PPIB FAM173A) based on serum proteomics provided a high discrimination ability for radiotherapy effects in NPC patients. Studies with larger sample size and longer follow-up outcome are required.

PI3K-PKB-mTOR hyperactivation in relation to nasopharyngeal carcinoma progression and prognosis

Nasopharyngeal carcinoma (NPC) has a unique and complex etiology, which is not completely understood. The aim of this study is to investigate the expression patterns of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB), and mammalian target of rapamycin (mTOR) proteins in patients with NPC and their relationship with NPC progression and prognosis. Between January 2008 and March 2010, PI3K, PKB, and mTOR protein expressions were detected using immunohistochemistry among 119 patients with NPC and 30 healthy people. A 5-year follow-up was conducted for all patients. Correlations of PI3K, PKB, and mTOR proteins with the clinicopathological features and prognosis of NPC were evaluated using Spearman's rank correlation coefficient and Kaplan-Meier curve. Cox's regression analysis was performed to analyze the risk factors for the prognosis of NPC. First, PI3K, PKB, and mTOR were highly expressed in patients with NPC. The expressions of PI3K, PKB, and mTOR proteins were associated with T stage, N stage, clinical stage, relapse, and distant metastasis. Meanwhile, PI3K is positively correlated with PKB and PKB is positively correlated with mTOR in NPC. Higher PI3K, PKB, and mTOR protein expressions were related to a shorter survival time and a lower survival rate in NPC. Cox regression analysis revealed that age, T stage, N stage, PI3K, PKB, and mTOR were independent risk factors for NPC patient survival. Altogether, our data suggest that overexpression of PI3K, PKB, and mTOR proteins is an important indicator of poor survival in NPC. In addition, inhibition of PI3K-PKB-mTOR signaling may also contribute to the development of new therapeutic strategies for NPC.

Quantitative Proteomic Analysis Identifies MAPK15 as a Potential Regulator of Radioresistance in Nasopharyngeal Carcinoma Cells

Since resistance to radiotherapy remains refractory for the clinical management of nasopharyngeal cancer (NPC), further understanding the mechanisms of radioresistance is necessary in order to develop more effective NPC treatment and improve prognosis. In this study, an integrated quantitative proteomic approach involving tandem mass tag labeling and liquid chromatograph-mass spectrometer was used to identify proteins potentially responsible for the radioresistance of NPC. The differential radiosensitivity in NPC model cells was examined through clonogenic survival assay, CCK-8 viability assay, and BrdU incorporation analysis. Apoptosis of NPC cells after exposure to irradiation was detected using caspase-3 colorimetric assay. Intracellular reactive oxygen species (ROS) was detected by a dichlorofluorescin diacetate fluorescent probe. In total, 5,946 protein groups were identified, among which 5,185 proteins were quantified. KEGG pathway analysis and protein-protein interaction enrichment analysis revealed robust activation of multiple biological processes/pathways in radioresistant CNE2-IR cells. Knockdown of MAPK15, one up-regulated protein kinase in CNE2-IR cells, significantly impaired clonogenic survival, decreased cell viability and increased cell apoptosis following exposure to irradiation, while over-expression of MAPK15 promoted cell survival, induced radioresistance and reduced apoptosis in NPC cell lines CNE1, CNE2, and HONE1. MAPK15 might regulate radioresistance through attenuating ROS accumulation and promoting DNA damage repair after exposure to irradiation in NPC cells. Quantitative proteomic analysis revealed enormous metabolic processes/signaling networks were potentially involved in the radioresistance of NPC cells. MAPK15 might be a novel potential regulator of radioresistance in NPC cells, and targeting MAPK15 might be useful in sensitizing NPC cells to radiotherapy.

Expression and clinical significance of basic transcription factor 3 in nasopharyngeal carcinoma

Basic transcription factor 3 (BTF3), a transcription factor and modulator of apoptosis, is differentially expressed in carcinoma. To acquire further understanding of the involvement of BTF3 in carcinoma, the present study analyzed the expression of BTF3, as well as its role in cell function in nasopharyngeal carcinoma (NPC). BTF3 transcription rates in human NPC samples (n=46) and adjacent normal tissue samples (n=46) were analyzed using reverse transcription-quantitative polymerase chain reaction and immunohistochemistry. BTF3-silencing in NPC cells was performed via specific small interfering RNA molecules. The function of BTF3 was analyzed by proliferation assays and colony forming assays using a Cellomic assay system. The positive expression rates of BTF3 were significantly increased in cancerous tissues compared with those in adjacent tissues (P<0.05). In addition, BTF3-silencing decreased cell proliferation and colony formation (P<0.01) in TCA-8113 and 5–8F cells. BTF3 is overexpressed in NPC, and its silencing is associated with decreased cell proliferation and colony formation, enhanced apoptosis and cell cycle regulation of TCA-8113 and 5–8F cells.

Discrimination of normal oral mucosa from oral cancer by mass spectrometry imaging of proteins and lipids

Identification of biomarkers for molecular classification of cancer and for differentiation between cancerous and normal epithelium remains a vital issue in the field of head and neck cancer. Here we aimed to compare the ability of proteome and lipidome components to discriminate oral cancer from normal mucosa. Tissue specimens including squamous cell cancer and normal epithelium were analyzed by MALDI mass spectrometry imaging. Two molecular domains of tissue components were imaged in serial sections-peptides (resulting from trypsin-processed proteins) and lipids (primarily zwitterionic phospholipids), then regions of interest corresponding to cancer and normal epithelium were compared. Heterogeneity of cancer regions was higher than the heterogeneity of normal epithelium, and the distribution of peptide components was more heterogeneous than the distribution of lipid components. Moreover, there were more peptide components than lipid components that showed significantly different abundance between cancer and normal epithelium (median of the Cohen's effect was 0.49 and 0.31 in case of peptide and lipid components, respectively). Multicomponent cancer classifier was tested (vs. normal epithelium) using tissue specimens from three patients and then validated with a tissue specimen from the fourth patient. Peptide-based signature and lipid-based signature allowed cancer classification with a weighted accuracy of 0.85 and 0.69, respectively. Nevertheless, both classifiers had very high precision (0.98 and 0.94, respectively). We concluded that though molecular differences between cancerous and normal mucosa were higher in the proteome domain than in the analyzed lipidome subdomain, imaging of lipidome components also enabled discrimination of oral cancer and normal epithelium. Therefore, both cancer proteome and lipidome are promising sources of biomarkers of oral malignancies.

Correlation of variable repeat number in the neck regions of DC-SIGN and DC-SIGNR with susceptibility to nasopharyngeal carcinoma in a Chinese population

Objective

To evaluate the potential association of variations in the number of tandem repeats in the dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) and dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin-related (DC-SIGNR) neck region with susceptibility to nasopharyngeal carcinoma (NPC).

Methods

Variations in the number of repeats in the genotypes and alleles in the neck region of DC-SIGN/DC-SIGNR were analyzed in 477 unrelated NPC patients and 561 cancer-free controls.

Results

Genotypes and alleles in the DC-SIGN neck region did not differ significantly between NPC patients and controls, but the 9-repeat genotype in the DC-SIGNR neck region was significantly more frequent among patients (OR 1.339, 95% CI 1.018–1.760, P=0.037). The association between this genotype and NPC remained significant after adjusting for sex, age, smoking history, and presence of immunoglobulin against Epstein–Barr virus viral capsid antigen (OR 1.625, 95% CI 1.134–2.329, P=0.0082).

Conclusion

These results suggest that genotypes/alleles in the DC-SIGN neck region are not associated with NPC susceptibility, whereas the 9-repeat variant in the neck region of DC-SIGNR may increase the risk of NPC.

PPARβ/δ Agonist GW501516 Inhibits Tumorigenicity of Undifferentiated Nasopharyngeal Carcinoma in C666-1 Cells by Promoting Apoptosis

Activation of peroxisome proliferator-activated receptor β/δ (PPARβ/δ) had been linked to inhibition on the proliferation and apoptosis in a few cancer cell lines. However, limited data exists regarding the role of PPARβ/δ in nasopharyngeal carcinoma (NPC). This study was undertaken to determine the effect of PPARβ/δ on cell proliferation, anchorage-dependent clonogenicity, and ectopic xenografts in the human NPC cell lines. Gene and protein expression of PPARβ/δ were reduced specifically in the poor- and un-differentiated NPC cell lines as compared with the control NP-69 cells. Ligand activation of PPARβ/δ by GW501516, a specific PPARβ/δ selective agonist, inhibited cell proliferation and colony formation strikingly, and induced a G2/M phase arrest in the EBV positive undifferentiated NPC C666-1 cells relative to the control cells. Moreover, GW501516 induced C666-1 cell apoptosis in a caspase and BAX dependent manner. In accordance with the in vitro result, GW501516 significantly suppressed the ectopic NPC xenograft tumorigenicity that derived from the C666-1 NPC cells in BALB/c nu/nu mice. This effect is greatly associated with its inhibition on the gene and protein expression of integrin-linked kinase (ILK) through activation of the AMPKα-dependent signaling pathways. Collectively, we showed that PPARβ/δ expression is in reverse correlation with the degree of differentiation in the NPC cell lines, and revealed the anti-tumorigenic effects of GW501516 in NPC cells by activation of AMPKα. This study suggested that PPARβ/δ targeting molecules may be useful for the poor-, and particularly un-differentiated NPC chemoprevention.

Nasopharyngeal Carcinoma Protein Interaction Mapping Analysis via Proteomic Approaches

Nasopharyngeal carcinoma (NPC), although not very common in many parts of the world, is a major concern in some countries, including Iran. Molecular studies are very helpful to provide essential information regarding underlying carcinogenetic mechanisms. Here, considering NPC proteomic approaches, established biomarkers were designated for protein-protein interaction network construction and analysis with corresponding plug-ins. A network of reported protein markers was constructed and topological and biological process features were investigated. Centrality analysis showed that JUN, CALM1, HSB1, and SOD1 are more important than other differentially expressed proteins in an interacting pattern. What is more, by extending the network, Tp53, PRDM10, AKT1, ALB, HSP90AA1, and EGFR achieved the highest values for NPC network strength. It can be concluded that these proteins as well as their contributing processes, particularly in a second network, may be important for NPC onset and development. Targeting these candidate proteins may allow novel treatment approaches following appropriate validation.

Knockout of the placenta specific 8 gene radiosensitizes nasopharyngeal carcinoma cells by activating the PI3K/AKT/GSK3β pathway

The present study investigated the radiosensitizing effect of placenta specific 8 (PLAC8) in nasopharyngeal carcinoma (NPC) cells. A PLAC8-knockout CNE2 cell line was constructed using the CRISPR/Cas9 system. The CCK-8 assay demonstrated knockout of PLAC8 significantly reduced cell proliferation and cell survival after irradiation compared to both control cells and non-irradiated PLAC8-knockout cells. The clonogenic assay showed knockout of PLAC8 enhanced the radiosensitivity of NPC cells. Flow cytometry revealed knockout of PLAC8 increased apoptosis and G2/M phase arrest after irradiation. Western blotting demonstrated knockout of PLAC8 was associated with increased levels of γHA2X, a higher BAX:BCL-2 ratio, and increased levels of phosphorylated-Akt and phosphorylated-GSK-3β. Overall, this study indicates PLAC8 contributes to radioresistance in NPC by inhibiting the PI3K/AKT/GSK3β pathway.

In silico-based identification of human α-enolase inhibitors to block cancer cell growth metabolically

Unlimited growth of cancer cells requires an extensive nutrient supply. To meet this demand, cancer cells drastically upregulate glucose uptake and metabolism compared to normal cells. This difference has made the blocking of glycolysis a fascinating strategy to treat this malignant disease. α-enolase is not only one of the most upregulated glycolytic enzymes in cancer cells, but also associates with many cellular processes or conditions important to cancer cell survival, such as cell migration, invasion, and hypoxia. Targeting α-enolase could simultaneously disturb cancer cells in multiple ways and, therefore, is a good target for anticancer drug development. In the current study, more than 22 million chemical structures meeting the criteria of Lipinski’s rule of five from the ZINC database were docked to α-enolase by virtual screening. Twenty-four chemical structures with docking scores better than that of the enolase substrate, 2-phosphoglycerate, were further screened by the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties prediction. Four of them were classified as non-mutagenic, non-carcinogenic, and capable of oral administration where they showed steady interactions to α-enolase that were comparable, even superior, to the currently available inhibitors in molecular dynamics (MD) simulation. These compounds may be considered promising leads for further development of the α-enolase inhibitors and could help fight cancer metabolically.

RNAi-mediated knockdown of CAIX enhances the radiosensitivity of nasopharyngeal carcinoma cell line, CNE-2

Although radiotherapy remains the most powerful as well as the primary treatment modality for nasopharyngeal carcinoma (NPC), approximately 20% of NPC patients still have local recurrence. Carbonic anhydrase IX (CAIX)-related signaling pathways that mediate radioresistance have been found in various kinds of cancer. However, the role of CAIX in NPC radioresistance is still unknown. In this study, we investigated the effect of CAIX silencing on sensitization to ionizing radiation in NPC by using Lipofectamine 2000, which delivers small interfering ribonucleic acid (siRNA) that targets CAIX. Results showed that Lipofectamine 2000 effectively delivered siRNA into the CNE-2 cells, which resulted in the decrease of CAIX expression and cell viability, decrease in cell proliferation and colony formation, and increase in the number of CNE-2 cells stuck in the G₂/M phase of the cell cycle upon induction of ionizing radiation. Increased sensitivity of radiotherapy in CNE-2 cells under hypoxic conditions was correlated with the suppression of CAIX. Cells treated with irradiation in addition to CAIX-siRNA1 demonstrated reduced radiobiological parameters (survival fraction at 2 Gy [SF2]) compared with those treated with irradiation only, with a sensitization-enhancing ratio of 1.47. These findings suggest that CAIX can be a promising therapeutic target for the treatment of radioresistant human NPC.

Identification of CALM as the potential serum biomarker for predicting the recurrence of nasopharyngeal carcinoma using a mass spectrometry-based comparative proteomic approach

To date, there are no serum biomarkers available for the prediction of recurrent nasopharyngeal carcinoma (rNPC). The diagnosis of rNPC mostly depends on imaging and biopsy of diseased tissue; however, both of these methods work mostly if the target tumor is at an advanced stage. Therefore, the identificaqtion of recurrent biomarkers is urgently required. In the present study, we used tandem mass tag (TMT) labeling and high performance liquid chromatography (HPLC) fractionation followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify differentially expressed proteins. Serum was collected from 40 patients with NPC [recurrence (n=20) and no recurrence (n=20)]. Compared to non-recurrent NPC (nrNPC), we found 59 proteins to be significantly dysregulated in rNPC; most of these have been previously reported to play a role in carcinogenesis. The dysregulation of calmodulin (CALM) was confirmed in 74 new patients [recurrence (n=32) and no recurrence (n=42)] by ELISA. Moreover, we performed a preliminary pathway analysis which revealed that oxidative phosphorylation was altered in the patients with rNPC compared to those with nrNPC. Taken together, these data identify a potential diagnostic biomarker for rNPC and elucidate the potential molecular mechanisms that are dysregulated and contribute to the pathogenesis of rNPC.

Peptidome profiling of human serum of uveal melanoma patients based on magnetic bead fractionation and mass spectrometry

AIM

To find new biomarkers for uveal melanoma (UM) by analyzing the serum peptidome profile.

METHODS

Proteomic spectra in patients with UM before and after operation were analyzed and compared with those of healthy controls. Magnetic affinity beads were used to capture serum peptides and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer were used to compile serum peptide profiles.

RESULTS

A panel of 49 peptides were differentially expressed between UM patients and controls, of which 33 peptides were of higher intensities in patient group and 16 peptides were of higher intensities in control group. Based on combined use of these potential markers, peptides with mean molecular masses of 1467 and 9289.0 Da provide high sensitivity (83.3%), specificity (100%) and accuracy rate (93.0%) together to differentiate melanoma patients from healthy controls. At the time point of 6mo postoperatively, the levels of many peptides differentially expressed before surgery showed no more statistical difference between the patients and the control group. Fibrinogen α-chain precursors were identified as potential UM markers.

CONCLUSION

We have shown that a convenient and fast proteomic technique, affinity bead separation and MALDI-TOF analysis combined with bioinformatic software, facilitates the identification of novel biomarkers for UM.

MicroRNA‑210 negatively regulates the radiosensitivity of nasopharyngeal carcinoma cells

Radiotherapy is one of the primary methods of treatment of malignant tumors, however, resistance to radiation is a major problem. The reasons for the radioresistance are still poorly understood. However, it is generally accepted that microRNAs (miRNAs or miRs) can regulate the radiosensitivity of tumors. The present study therefore aimed to identify specific miRNAs and their effects on radioresistant cells. More specifically, the aim was to investigate specific miRNAs and their effects on radioresistant tumor cells. The radioresistant tumor cells (CNE‑2R) were established using a dose gradient method, and the miRNA expression profiles of CNE‑2R cells and the parental cells (CNE‑2) were determined. The expression of miR‑210 in CNE‑2R cells was significantly higher than in CNE‑2 cells. CNE‑2R cells were transfected with LV‑hsa‑miR‑210‑inhibitor, and CNE‑2 cells were transfected with LV‑hsa‑miR‑210. The expression of miR‑210 was confirmed by reverse transcription quantitative‑polymerase chain reaction. The percentages of CNE‑2R‑miR‑210‑inhibitor and CNE‑2 cells in the G2/M phase were higher than in the CNE‑2R and CNE‑2‑miR‑210 cells, and the percentages of cells in S phase were lower than in the CNE‑2R and CNE‑2‑miR‑210 cells. Following 4 Gy of radiation, CNE‑2R‑miR‑210‑inhibitor and CNE‑2 cells, which express low levels of miR‑210, had a higher apoptosis rate than CNE‑2R and CNE‑2‑miR‑210 cells. Following 4, 8 and 12 Gy of radiation, cell viability and survival fraction of CNE‑2R‑miR‑210‑inhibitor cells were lower than those of CNE‑2R and CNE‑2‑miR‑210 cells, and similar to those of CNE‑2 cells. Together, these findings strongly suggest that miR‑210 negatively regulates the radiosensitivity of tumor cells, and may therefore have therapeutic potential for the treatment of radiation resistance.

lncRNA C22orf32-1 contributes to the tumorigenesis of nasopharyngeal carcinoma

The mechanism of nasopharyngeal carcinoma (NPC) remains unclear. The present study investigated the abnormal expression of long non-coding (lnc)RNAs in NPC tissues and one NPC cell line to identify the involvement of lncRNAs in the tumorigenesis of NPC. Using a quantitative reverse transcription polymerase chain reaction (RT-qPCR), the expression of lncRNA C22orf32-1 in NPC tissues and an NPC cell line was verified. The effects of lncRNA C22orf32-1 on NPC cells were investigated with a cell proliferation assay, cell scratch assay, Transwell assay and a cell apoptosis assay. The expression levels of lncRNA C22orf32-1 in NPC tissues and an NPC cell line were upregulated. lncRNA C22orf32-1 promoted the proliferation, migration and invasion of NPC cells, and reduced the apoptosis of NPC cells. The data demonstrated that lncRNA C22orf32-1 may facilitate the tumorigenesis of NPC, and may be used for the early diagnosis and treatment of NPC.

Serum CD166: A novel biomarker for predicting nasopharyngeal carcinoma response to radiotherapy

The present study aimed to identify whether CD166 can be used as a biomarker for predicting the response of nasopharyngeal carcinoma (NPC) to radiotherapy. The serum concentration of CD166 in patients with NPC were detected by enzyme-linked immunosorbent assay. The secreted level of CD166 with radioresistant NPC was significantly higher than that with radiosensitive NPC. In vitro, the CD166 positive rate in the CNE2 cell membrane was significantly lower than that in the CNE2R cell membrane. The magnetic-activated cell sorting technology was used to obtain CNE-2R-CD166(+) and CNE-2R-CD166(−) cell lines. Then radiosensitivity, cell proliferation, and apoptosis were assessed using colony formation assay, cell counting kit 8 assay (CCK-8), and flow cytometry, respectively. The radiation sensitivity ratio was 1.28, indicating that the CNE2R-CD166(−) cells had a stronger radiation sensitivity. The result of CCK-8 assay indicated that the survival fraction of CNE2R-CD166(+) cells was significantly higher than that of CNE2R-CD166(−) cells. The apoptotic rate of CNE2R-CD166(+) cells was significantly lower than that of CNE2R-CD166(−) cells. Our data demonstrate that the secreted protein CD166 may be can used as a biomarker for predicting the response of NPC to radiotherapy.

Overexpression of IGFBP3 is associated with poor prognosis and tumor metastasis in nasopharyngeal carcinoma

Insulin-like growth factor-binding protein-3 (IGFBP3) is an N-linked glycosylated, phosphorylated protein, which has been reported to regulate cancer progression and metastasis. However, the role of IGFBP3 in tumor metastasis remains under debate. Nasopharyngeal carcinoma (NPC) is a highly metastatic head and neck cancer. And it fails to achieve the desired therapeutic efficacy in patients with metastasis, while the role of IGFBP3 in NPC is still unclear. In this study, we first used immunohistochemistry to explore the expression of IGFBP3 in NPC tissues. We found that IGFBP3 was significantly elevated in NPC and its expression level was correlated with N classification, distant metastasis, and TNM clinical stage (all P < 0.05). Patients with high expression of IGFBP3 had poorer survival rate (P < 0.05). In addition, we found that downregulation of IGFBP3 inhibited cell migration and adhesion by Transwell migration assay, wounding healing assay, and cell adhesion assays in vitro. Besides, NPC cells stimulated with recombinant IGFBP3 accelerated migration and adhesion. These data suggest overexpression of IGFBP3 promotes tumor metastasis in NPC, which makes it a potential therapeutic target.

Elevated expression of CD93 promotes angiogenesis and tumor growth in nasopharyngeal carcinoma

CD93, also known as the complement component C1q receptor (C1qRp), has been reported to promote the progression of some cancer types. However, the expression and physiological significance of CD93 in nasopharyngeal carcinoma (NPC) remain largely elusive. In this study, we first examined the expression of CD93 in NPC and experimentally manipulated its expression. We observed that vascular CD93 expression is elevated in NPC and is correlated with T classification, N classification, distant metastasis, clinical stage and poor prognosis (all P < 0.05). In addition, overexpression of CD93 promoted angiogenesis in vitro. What's more, we found that CD93 was highly expressed in NPC tissues and cells, and the regulation of CD93 on cell proliferation was determined by cell counting kit (CCK)-8 assay and cell cycle analyses. Our findings provide unique insight into the pathogenesis of NPC and underscore the need to explore novel therapeutic targets such as CD93 to improve NPC treatment.

HYOU1, Regulated by LPLUNC1, Is Up-Regulated in Nasopharyngeal Carcinoma and Associated with Poor Prognosis

Objective: This study aims to investigate the roles and mechanisms of long palate, lung and nasal epithelium clone 1 (LPLUNC1) in nasopharyngeal carcinoma (NPC).

Methods: The two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-TOF-MS/MS) was applied to identify differentially expressed proteins after over-expressing LPLUNC1 in NPC cells. The qRT-PCR and Western Blot were used to further validate differentially expression of Hypoxia up-regulated 1 (HYOU1). We also applied immunohistochemistry (IHC) to validate the expression of HYOU1 protein in NPC tissues.

Results: Totally 44 differentially expressed proteins were identified, among which 19 proteins were up-regulated and 25 proteins were down-regulated. Function annotation indicated that these proteins were involved in molecular chaperone, cytoskeleton, metabolism and signal transduction. It was shown that the expression of HYOU1 both at mRNA level and protein level was up-regulated significantly in NPC tissues, and HYOU1 protein expression was positively correlated with clinical staging and metastasis of NPC. Kaplan-Meier survival curves showed that high expression of HYOU1 protein in NPC patients had shorter progression-free survival (PFS) and overall survival (OS). COX multivariate regression analysis further indicated that over-expressed HYOU1 was one of the predictors for poor prognosis in NPC patients.

Conclusion: Through regulating proteins in different pathways, LPLUNC1 may inhibit the growth of NPC through participating in cell metabolism, proliferation, transcription and signaling transduction. HYOU1 can be regarded as potential molecular biomarker for progression and prognosis of NPC.