Aurora kinase A (AURKA) and never in mitosis gene A-related kinase 6 (NEK6) genes are upregulated in erosive esophagitis and esophageal adenocarcinoma
- Authors:
- Published online on: April 25, 2012 https://doi.org/10.3892/etm.2012.561
- Pages: 33-42
Abstract
Introduction
Esophageal cancer is the sixth most leading cause of cancer-related mortality worldwide (1). Esophageal adeno-carcinoma (EAC) and esophageal squamous cell carcinoma are the two main histological types of esophageal cancers (1). Of all esophageal cancer types in Western countries, 30-50% of cases are esophageal adenocarcinoma (1). The incidence of EAC has increased faster than that of any malignancy in Western countries, with an increase of 400% over the past 40 years (2). However, there has been no increase in the prevalence of proximal gastric cancers and distal esophageal adenocarcinomas in the Turkish population (3). The prognosis for EAC is poor and the overall 5-year survival rate is less than 10% (4). Risk factors for EAC include dietary factors, alcohol and tobacco use, obesity, gastroesophageal reflux disease and Barrett’s esophagus (BE) (5). Gastroesophageal reflux disease (GERD) is very common worldwide (6). The prevalence of GERD is high, especially in developed Western countries (7). Bor et al found the prevalence of GERD to be 20% in Izmir (8) and 22.8% in Turkey, similar to the rates in the US (7). Chronic GERD is one of the main risk factors for the development of Barrett’s esophagus (BE) and BE is one of the strongest risk factors for EAC (5,9). Mechanisms that control chromatin stucture and gene expression in normal mammalian cells are DNA methylation, covalent histone modifications, nucleosome position, histone variants and miRNAs (10–12). Recent epigenetic studies have shown the effect of epigenetic alterations in carcinogenesis as well as genetic alterations. A number of studies suggest that epigenetic alterations may even be initiating factors for certain types of cancer (13). Genetic alterations are irreversible but epigenetic alterations are reversible and this fact supports future hope for epigenetic therapy (14).
Studies that have investigated the relationship between erosive esophagitis (EE) and EAC usually focus on symptom-related evidence or on polymorphisms. There are no epigenetic gene expression studies on this topic. We aimed to evaluate the relationship between EE and EAC to ascertain whether there is a genetic tendency for EAC.
Materials and methods
Location of study
The study was conducted at the Department of Gastroenterology, Department of Medical Biology, Celal Bayar University, Manisa between March 2010 and September 2011. Patients were also referred from the Department of Gastroenterology, Celal Bayar University, the Department of Gastroenterology, Ege University and the Department of Gastroenterology, Ataturk Research and Training Hospital.
Ethics
This study was performed in accordance with the Declaration of Helsinki, good clinical practice and applicable regulatory requirements. Celal Bayar University Institutional Review Board approved this clinical trial on June 2, 2009. Each patient signed a consent form prior to any study-related procedure.
Study design and subjects
Between March 2010 and September 2011 fresh paired tissue samples from 60 patients [group 1 (20 patients) categorized as the macroscopic and histopathologically confirmed esophageal carcinoma group; group 2 (20 patients) categorized as the erosive esophagitis (without histopathologically esophageal adenocarcinoma and Barrett’s esophagus) group; and group 3 (20 patients) categorized as the control group (who had normal esophageal mucosa with no endoscopic or histopathological lesions)] were collected. Typical GERD symptoms were defined as at least five years of regurgitation and/or heartburn per week in erosive esophagitis. Patients were excluded from the study if they had a history of upper gastrointestinal surgery such as gastrectomy, fundoplication or distal esophagectomy, severe gastroparesis and esophageal varices.
Endoscopy
Erosive esophagitis and control group
Esophagogastroduodenoscopies were undertaken for the EE and control group at the Department of Gastroenterology, Celal Bayar University by the same two endoscopists (E.K., H.Y.) who performed the study. During upper gastrointestinal endoscopy, the distal 5 cm of the esophagus mucosal morphology at the squamo-columnar junction was visualized using conventional endoscopy followed by the Narrow Band Imaging (NBI) system using video endoscopes. During standard white-light endoscopy and NBI examination, erosions, mucosal breaks and other complications were graded according to the Los Angeles classification (15). Two biopsies were taken 2 cm above the esophagogastric junction from patients in the control group, and two biopsies were taken from mucosal breaks in patients with EE.
Esophageal adenocarcinoma
Esophagogastroduodenoscopies were undertaken for EAC cases at the Department of Gastroenterology, Celal Bayar University (11 patients), Department of Gastroenterology, Ege University and Department of Gastroenterology (5 patients), Ataturk Research and Training Hospital (4 patients). Two biopsies were taken from patients pathologically diagnosed as having EACs using Olympus biopsy forceps.
EAC was evaluated according to thoracic and abdominal computed tomography (CT) in three stages: stage 1, esophageal adenocarcinoma located in the esophagus; stage 2, esophageal adenocarcinoma located in the esophagus and with pathological lymphadenopathy; stage 3, esophageal adenocarcinoma located in the esophagus with pathological lymphadenopathy and distant metastasis.
Samples were immediately frozen using dry ice (a block of dry ice has a surface temperature of −78.5°C) and stored at −80°C until RNA extraction.
Isolation of total RNA
Total RNA was extracted using the TriPure solution as described in the manufacturer’s protocol. The fresh tissue was resuspended in a vial of MagNA Lyser Green Beads containing 350 μl lysis buffer and 50 μl of proteinase (Roche). Next, the suspension was subjected to mechanical lysis in a MagNA lyser instrument (Roche) for 45 sec at 4500 rpm. Afterwards, RNA was further extracted and purified using a MagNA Pure LC instrument (Roche) in combination with the MagNA Pure NA isolation kit III. All steps were taken according to the manufacturer’s protocol.
Quantity and purity of total RNA
RNA was quantified measuring the absorbance at 260 nm (A260 nm) and RNA purity was determined by the ratio A260 nm/A280 nm using a classical spectrophotometer. RNA quality was good, with 260/280 ratios slightly higher than 2.0 and 260/230 ratios slightly higher than 1.8.
RT2 profiler™ PCR protocol first strand cDNA synthesis
The protocol took 2 h to perform (per sample) from start to finish. We initially had as little as 25 ng of total RNA from our experimental samples. We first converted the experimental RNA samples into PCR templates to prepare cDNAs with the RT2 First Strand kit (SABioscience, Frederick, MD, USA) according to the manufacturer’s instructions. Next we combined the template with a specific instrument and used ready-to-use RT2 SYBR Green qPCR Master Mix. Then we added equal aliquots of this mixture (25 μl for 96-well) to each well of the same PCR array plate containing the predispensed gene-specific primer sets and performed PCR. Specialized software (SABiosciences) was used to calculate the threshold cycle (Ct) values for the genes on each PCR array.
Epigenetic chromatin modification enzyme PCR array
The Human Epigenetic Chromatin Modification Enzyme RT2 Profiler™ PCR Array (PAHS-085A) (SABiosciences) was used to detect the expression levels of 84 key genes (Table I) encoding enzymes known or predicted to modify genomic DNA and histones to regulate chromatin accessibility and therefore gene expression. These genes exhibit differential expression profiles in tumor cells relative to normal cells. The PCR array is a 96-well plate containing RT2 Profiler™ PCR Primer Assays for a set of 84 related genes, plus five housekeeping genes and three controls.
Data analysis
Data were analyzed using RT2 profiler PCR array data analysis software (http://www.sabiosciences.com/pcrarraydataanalysis.php). The website also allowed online analysis. For each PCR reaction, the Excel sheet calculated two normalized average cycle threshold (Ct) values, a paired t-test p-value and a fold-change. PCR array quantification was based on the Ct number. A gene was considered not detectable when Ct >32. Ct was defined as 35 for the ΔCt calculation when the signal was under detectable limits.
Fold-change and fold-regulation values >2 were indicative of upregulated gene; fold-change values <0.5 and fold-regulation values <-2 were indicative of downregulated genes.
Statistics
Data were statistically analyzed with RT2 profiler PCR array data analysis software (http://www.sabiosciences.com/pcrarraydataanalysis.php). Results were expressed as the mean values ± standard deviation and the p-values were calculated based on a Student’s t-test of the replicate 2−ΔCt values for each gene in the control group, esophageal adenocarcinoma group and erosive esophagitis group. A p-value <0.05 was accepted as statistically significant.
Results
A total of 60 patients were divided into three groups: 20 patients as a control group (who had normal esophageal mucosa with no esophagogastroduodenoscopic or histopathological lesions), 20 patients with EE without Barrett’s esophagus and microscopic adenocarcinoma and 20 patients with macroscopic and histopathological adenocarcinoma. The mean age ± SD of the control group was 51.5±11.3 years. The mean age ± SD of the EE group was 56.6±10.2 years. The mean age ± SD of the EAC group was 58.6±12.4 years.
For the three groups genetic analysis was used to investigate the expression of 84 key genes (Table I) encoding enzymes known or predicted to modify genomic DNA and histones to regulate chromatin accessibility and therefore gene expression.
Upregulated and downregulated genes in the EAC and control group are summarized in Table II. AURKA, AURKB, NEK6 were expressed at significantly higher levels in the EAC than in the control group. MBD2 was expressed significantly lower in the EAC than in the control group. Fig. 1 is a scatter plot of the log base 10 of the hybridization intensity of each gene in the two groups [x-axis, control group; y-axis, the EAC (group 1) group]. The middle line indicates a fold-change (2−ΔCt) of 1. The top and the bottom lines indicate the desired fold-change in gene expression threshold. Expression of 80 key genes was unchanged, showing no significant difference in expression between the two groups. The three points above the top line indicate upregulated (AURKA, AURKB, NEK6) genes. The one point under the bottom line represents a down-regulated (MBD2) gene.
 | Table II.Differentially upregulated and downregulated genes between the esophageal adenocarcinomas and control group. |
Upregulated and downregulated genes in the EE and control group are summarized in Table III. Seven genes (AURKA, AURKC, HDAC9, NEK6, HDAC8, SETD5, SETD7) were upregulated and AURKA, AURKC, HDAC9, NEK6 were expressed at significantly higher levels in EE than in the control group. There were no downregulated genes in the two groups. Fig. 2 is a scatter plot of the log base 10 of the hybridization intensity of each gene in the two groups [x-axis, control group; y-axis, EE (group 2) group]. The middle line indicates a fold-change (2–ΔCt) of 1. The top and the bottom lines indicate the desired fold-change in gene expression threshold. Expression of 77 key genes was unchanged with no significant difference in gene expression between the two groups. The seven points above the top line represent upregulated (AURKA, AURKC, HDAC9, NEK6, HDAC8, SETD5, SETD7) genes.
| Table III.Differentially upregulated and downregulateda genes between the erosive esophagitis and control group. |
Upregulated and downregulated genes in EAC and EE are summarized in Table IV. There was no significant difference in gene upregulation between the two groups. Two genes (MBD2 and MYSM1) were downregulated and MBD2 was significantly downregulated in EAC compared to the EE group. Fig. 3 is a plot of the log base 10 of the hybridization intensity of each gene in the two groups (x-axis represents group 1, EAC, and the y-axis shows group 2, EE). The middle line indicates a fold-change (2−ΔCt) of 1. The top and bottom lines indicate the desired fold-change in gene expression threshold. The expression of 82 key genes was unchanged and no significant difference in gene upregulation was noted between the two groups. The two points under the bottom line represent downregulated (MBD2, MSYM1) genes.
| Table IV.Differentially upregulateda and downregulated genes between esophageal adenocarcinoma and erosive esophagitis. |
The NEK6 and AURKA genes were significantly upregulated in the EAC and EE groups compared to the control group.
The correlation between the AURKA gene and the stage of EAC is summarized in Fig. 4A. There were more patients in the stage 1 group than in the stage 2 and stage 3 groups (p<0.05).
The correlation between the NEK6 gene and the stage of EAC is summarized in Fig. 4B. Again, there were more patients classified in the stage 1 group than in stage 2 and stage 3 groups (p<0.05).
The correlation between expression of the AURKA gene and the Los Angeles classification of erosive esophagitis are summarized in Fig. 5A. Expression of the AURKA gene was found to be elevated dependent on the grade of EE according to the Los Angeles Classification.
The correlation between expression of the NEK6 gene and the Los Angeles classification of EE is summarized in Fig. 5B. The patients with overexpression of the NEK6 gene were more prevalent in the LA Grade B than LA Grade A group (p>0.05).
A clustergram analysis based on differentially expressed genes between the three groups is shown in Fig. 6. The cluster-gram creates a heat map with dendrograms to show genes that are co-regulated. The color saturation reflects the magnitude of the change in gene expression. Green squares represent lower gene expression in the experimental samples (ratios less than 1); black squares represent genes equally expressed (ratios near 1); red squares represent higher than control levels of gene expression (ratios greater than 1); gray squares indicate insufficient or missing data.
Discussion
Understanding the epigenetic structure of carcinomas provides important information on carcinogenesis. Expanding the information on the molecular biology of cancer may result in better follow-up of precancerous and cancer lesions (13,16). Epigenetic changes in stem cells provide important information concerning cancer aetiology, and epigenetic alterations such as gene expression have been used as biomarkers in recent years (17).
In the present study, three genes were overexpressed in the EAC group, with AURKA, AURKB and NEK6 being significantly more highly expressed than levels in the control group. Four genes (AURKA, AURKC, HDAC9, NEK6) were significantly more highly expressed in the EE group than levels in the control group. AURKA and NEK6 genes were significantly more highly expressed in the EE group and in the EAC group than levels in the control group.
Recent studies have shown that the aurora kinase family, polo-like kinase family and NIMA (never in mitosis gene A) kinase family control cell cycle (18,19). Aurora kinases are activated through autophosphorylation at the activation loop unlike most kinases within the cell (20) and NimA promotes mitotic chromosome condensation through phosphorylation of histone H3 at serine 10 and may compose the nuclear membrane division during mitotic exit (21).
Enzymes in the Aurora kinase family are encoded by the AURKA (also called AIK/ARK1/AURA/AURORA2/BTAK/MGC34538/STK15/STK6/STK7) gene, which is localized on 20q13.2 (22,23). These enzymes play very important roles in mitosis and meiosis for healthy cell proliferation. AURKA is a serine/threonine kinase acting as a regulator of centro-some function/duplication, mitotic entry, and bipolar spindle assembly (24). AURKA protein levels and kinase activity are low in the G1/S phase; accumulate during G2/M and decrease rapidly following mitosis (25). AURKA is an important kinase-encoding gene involved in centrosome duplication and distribution; its overexpression leads to centrosome amplification, chromosomal instability and aneuploidy in several cancer types (26,27). AURKA overexpression has been found in numerous tumor cells and tissues including gastric cancer, breast cancer, colorectal cancer, bladder cancer, pancreatic cancer, ovarian cancer, prostate cancer and esophageal squamous-cell carcinoma, esophageal adenocarcinoma and Barrett’s esophagus (27,28). Dar et al demonstrated overexpression of mitotic kinase encoding gene in upper gastrointestinal adenocarcinomas through the immunohistochemical analysis of 130 tumors. This overexpression was more prevalent in gastroesophageal junction adenocarcinomas and lower in esophageal, Barrett-related adenocarcinomas (BAS) than in antrum and body gastric adenocarcinomas. They also found that the expression of AURKA caused an anti-apoptotic effect in gastrointestinal cancer cells with drug-induced apoptosis in an in vitro model (27). Rugge et al found that AURKA immunostaining increased significantly along with the Barrett’s carcinogenesis, from Barrett’s mucosa even without metaplasia towards Barrett’s adenocarcinoma (24). AURKA appears to play an important role in the carcinogenesis of esophageal adenocarcinoma and will be an important target for surveillance, diagnosis, treatment and prognosis in Barrett’s esophagus. The positive relationship between Barrett’s esophagus and AURKA is important for our results since in this study we demonstrated that AURKA is upregulated in erosive esophagitis and the AURKA gene was found to be elevated dependent on the grade of erosive esophagitis based on the Los Angeles Classification. GERD can yield to complications such as erosive esophagitis and strictures; furthermore, it can cause Barrett’s esophagus, which can progress to adenocarcinoma (29). We believe that ascertaining whether the AURKA gene may be used as an early marker in erosive esophagitis toward the development of EAC is crucial.
NIMA is another gene found to be related to cell cycle dysfunction when it is overexpressed or underexpressed. NIMA (never in mitosis gene a)-related kinase 6 (NEK6; also called SID6-1512) is localized on chromosome 9q33-34 and is a serine/threonine kinase that belongs to the Neks (NIMA-related kinases) family, which has been implicated in mitosis control (30). Yin et al previously found that human Nek6 is required for metaphase-anaphase transition during cell cycle progression (31). It is believed that interfering with Nek6 function causes mitotic arrest and triggers apoptosis (32,33). The negative mutant form of Nek6 was found to induce spindle defects, abnormal chromosome segregation, mitotic arrest and apoptosis (34). Overexpression of Nek6 was shown in hepatocellular carcinoma as compared with the adjacent normal tissue as an evidence of its antiapoptotic effect (18). Overexpression of NEK6 was associated with histological grade, level of α feto protein and poor prognosis. NEK6 was shown to mediate human cancer cell transformation and was proposed as a potential cancer therapeutic marker in a previous study (34). Takeno et al stated that NEK6 is a potential marker of gastric cancer regardless of stage and since conventional staging of tumors are not adequate to predict individual prognosis, genetic analyses of tumor tissues may provide better opportunities to predict disease outcome for each individual and may even predict response to therapy (35). The authors selected seven focus genes showing a 2-fold change; four had not been previously evaluated for the association with gastric tumors. NEK6 was one these four new genes (35). They concluded that mapping of gene expression data on large sample numbers helped to identify two novel candidate genes, INHBA and NEK6, that are promising potential markers of gastric cancer. Nassirpour et al revealed that the protein level and kinase activity of Nek6 are highly elevated in a variety of malignant human cancers including breast, uterus, colon, stomach, ovary, lung, kidney, rectum, thyroid, cervix, prostate, pancreas, small intestine cancer cells, and knockdown of Nek6 resulted in reduction of tumors in a nude mouse xenograft model (34). They concluded that since inhibition of NEK6 specifically induces cell death in tumor cells and not in normal tissues, NEK6 inhibitors are a better therapeutic option with lower side effects than cytotoxic antitumor agents.
This is the first study investigating the impact of NEK6 in esophageal adenocarcinoma. Our data show the significant upregulation of NEK6 in erosive esophagitis and esophageal adenocarcinoma. NEK6 was more prevalent in samples with Los Angeles classification B than A in erosive esophagitis demonstrating that NEK6 and AURKA are more evident in more severe forms of esophagitis.
Erosive esophagitis is chronic damage of the esophagus caused by acid, pepsin and biliary salts. Environmental insults cause genetic and epigenetic alterations and they affect the expression of tumor-progenitor genes. Chronic injury is a major cause of cancer even though it is not inherently mutagenic (16). There are studies with large number of patients and long follow-up periods for GERD patients investigating whether they are at risk of developing esophageal adenocarcinoma. In a Swedish nationwide case-control study, gastroesophageal reflux and obesity were identified as strong and independent risk factors for esophageal adenocarcinoma. The risk increased with duration and severity of reflux symptoms and with increasing body mass index (36). Erichsen et al performed a nationwide cohort study in Denmark using data from 33,849 GERD patients and concluded that erosive but not non-erosive reflux disease has an impact on the development of adenocarcinoma emphasizing inflammation as an important factor in carcinogenesis (37).
In our study, in addition to AURKA and NEK6, HDAC9 and AURKC were significantly upregulated in EE compared to the control group. These genes were not expressed in EAC. Wu et al stated that AURKC was overexpressed in inflamed cervical tissue specimens and HDAC inhibitors are therapeutic for several inflammatory conditions (38,39). Do these genes have a role in addition to defect of the defense mechanism of the esophagus in patients with EE in gastroesophageal disease?
MBD2 was significantly downregulated in EAC compared to EE and the control group. MBD2 is a member of the MBD protein family. MBD2 binds to methylated promoter CpG islands and acts as a methylation-dependent transcriptional repressor (40). MBD2 has a role in the activation of methylated and unmethylated genes (42). Expression of MBD2 was particularly low in brain tumors, immune thrombocytopenia and in colorectal and gastric carcinomas (42–44) as found in our study. The reasons for the loss of MBD2 expression and the functional consequences are unknown (44). Thus, MBD2 should be studied further in relation to its association with esophageal adenocarcinoma.
This is the first study concerning the epigenetic chromatin histone modification in EE and EAC patients. Compared to the other genes investigated, AURKA and NEK6 were notably upregulated in EAC and EE. AURKA was proven to be associated with EAC in previous studies, and we found similar results for AURKA. This is the first study investigating the impact of NEK6 in esophageal adenocarcinoma, and our data revealed the significant upregulation of NEK6 in erosive esophagitis and esophageal adenocarcinoma. Our study is also the first study aiming to detect the presence of genetic upregulation in EE, a lesion which is not considered to be a precancerous lesion. These results pave the way for future studies with larger numbers of patients and longitudinal studies with longer follow-up periods. In a recent study (7), we found that low prevalence of Barrett’s esophagus was demonstrated in a Western Turkish population. Based on these data, we intend to explore expression of AURKA and NEK6 genes in the future at the national level, using another group with Barrett’s esophagus.
It is hoped that future studies may address the following questions: i) Is erosive esophagitis a precancerous lesion and once detected, is surveillance required? ii) Can AURKA and NEK6 be used as screening tests for esophageal adeno-carcinoma in erosive esophagitis? iii) What are the ranges of AURKA and NEK6 overexpression predictive of the prognosis and the outcome of antitumor therapy? iv) Can AURKA and NEK6 be used as therapeutic targets?
In conclusion, we demonstrated overexpression of AURKA and NEK6 in erosive esophagitis and esophageal adenocarcinoma in a Turkish population. Understanding the molecular pathophysiology of the disease will aid in elucidating the steps for diagnosis, therapy and prognosis. AURKA and NEK6 are two promising genetic markers for erosive esophagitis and esophageal adenocarcinoma.
Abbreviations:
|
AURKA |
aurora kinase A |
|
AURKB |
aurora kinase B |
|
AURKC |
aurora kinase C |
|
BE |
Barrett’s esophagus |
|
EAC |
esophageal adenocarcinoma |
|
EE |
erosive esophagitis |
|
GERD |
gastroesophageal reflux disease |
|
HDAC9 |
histone deacetylase 9 |
|
MBD2 |
methyl-CpG binding domain protein 2 |
|
NEK6 |
never in mitosis gene A-related kinase 6 |
Acknowledgements
This study was supported by the Celal Bayar University Coordinator of the Scientific Research Projects (2009-053) Manisa, Turkey.
References
|
Ekiz F, Ormeci N, Coban S, et al: Association of methylenetetrahydrofolate reductase C677T-A1298C polymorphisms with risk for esophageal adenocarcinoma, Barrett’s esophagus, and reflux esophagitis. Dis Esophagus. Sep 23–2011.(Epub ahead of print). | |
|
Yoon HH, Khan M, Shi Q, et al: The prognostic value of clinical and pathologic factors in esophageal adenocarcinoma: a Mayo cohort of 796 patients with extended follow-up after surgical resection. Mayo Clin Proc. 85:1080–1089. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Bor S, Vardar R, Ormeci N, et al: Prevalence patterns of gastric cancers in Turkey: model of a developing country with high occurrence of Helicobacter pylori. J Gastroenterol Hepatol. 22:2242–2245. 2007. View Article : Google Scholar : PubMed/NCBI | |
|
Reavis KM, Morris CD, Gopal DV, Hunter JG and Jobe BA: Laryngopharyngeal reflux symptoms better predict the presence of esophageal adenocarcinoma than typical gastroesophageal reflux symptoms. Ann Surg. 239:849–856. 2004. View Article : Google Scholar | |
|
Das A: Tumors of the Esophagus. In: Sleisenger and Fordtran’s Gastrointestinal and Liver Disease. Feldman M, Friedman L, Friedman S and Brandt JL: Saunders, Elsevier; Philadelphia: pp. 745–773. 2010 | |
|
Zendehdel N, Biramijamal F, Hossein-Nezhad A, Zendehdel N, Sarie H, Doughaiemoghaddam M and Pourshams A: Role of cytochrome P450 2C19 genetic polymorphisms in the therapeutic efficacy of omeprazole in Iranian patients with erosive reflux esophagitis. Arch Iran Med. 13:406–412. 2010.PubMed/NCBI | |
|
Bayrakçi B, Kasap E, Kitapçioğlu G and Bor S: Low prevalence of erosive esophagitis and Barrett esophagus in a tertiary referral center in Turkey. Turk J Gastroenterol. 19:145–151. 2008.PubMed/NCBI | |
|
Bor S, Mandıracıoglu A, Kitapcıoglu G, Caymaz-Bor C and Gilbert RJ: Gastroesophageal reflux in a low-income region in Turkey. Am J Gastroenterol. 100:744–754. 2005.PubMed/NCBI | |
|
Peng D, Hu TL, Jiang A, Washington MK, Moskaluk CA, Schneider-Stock R and El-Rifai W: Location-specific epigenetic regulation of the metallothionein 3 gene in esophageal adenocarcinomas. PLoS One. 6:e220092011. View Article : Google Scholar : PubMed/NCBI | |
|
Sharma S, Kelly TK and Jones PA: Epigenetics in cancer. Carcinogenesis. 31:27–36. 2010. View Article : Google Scholar | |
|
Jones PA and Baylin SB: The fundamental role of epigenetic events in cancer. Nat Rev Genet. 3:415–428. 2002.PubMed/NCBI | |
|
Jones PA and Baylin SBl: The epigenomics of cancer. Cell. 128:683–692. 2007. View Article : Google Scholar : PubMed/NCBI | |
|
Feinberg AP, Ohlsson R and Henikoff S: The epigenetic progenitor origin of human cancer. Nat Rev Genet. 7:21–33. 2006. View Article : Google Scholar : PubMed/NCBI | |
|
Yoo CB and Jones PA: Epigenetic therapy of cancer: past, present and future. Nat Rev Drug Discov. 5:37–50. 2006. View Article : Google Scholar : PubMed/NCBI | |
|
Lundell LR, Dent J, Bennett JR, et al: Endoscopic assessment of oesophagitis: clinical and functional correlates and further validation of the Los Angeles classification. Gut. 45:172–180. 1999. View Article : Google Scholar : PubMed/NCBI | |
|
Egger G, Liang G, Aparicio A and Jones PA: Epigenetics in human disease and prospects for epigenetic therapy. Nature. 429:457–463. 2004. View Article : Google Scholar : PubMed/NCBI | |
|
Tzao C, Tung HJ, Jin JS, et al: Prognostic significance of global histone modifications in resected squamous cell carcinoma of the esophagus. Mod Pathol. 22:252–260. 2009. View Article : Google Scholar : PubMed/NCBI | |
|
Cao X, Xia Y, Yang J, et al: Clinical and biological significance of never in mitosis gene A-related kinase 6 (NEK6) expression in hepatic cell cancer. Pathol Oncol Res. 18:201–207. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Malumbres M and Barbacid M: Cell cycle kinases in cancer. Curr Opin Genet Dev. 17:60–65. 2007. View Article : Google Scholar | |
|
Fu J, Bian M, Jiang Q and Zhang C: Roles of Aurora kinases in mitosis and tumorigenesis. Mol Cancer Res. 5:1–10. 2007. View Article : Google Scholar : PubMed/NCBI | |
|
Moniz L, Dutt P, Haider N and Stambolic V: Nek family of kinases in cell cycle, checkpoint control and cancer. Cell Div. 6:182011. View Article : Google Scholar : PubMed/NCBI | |
|
Sen S, Zhou H and White RA: A putative serine/threonine kinase encoding gene BTAK on chromosome 20q13 is amplified and overexpressed in human breast cancer cell lines. Oncogene. 14:2195–2200. 1997. View Article : Google Scholar : PubMed/NCBI | |
|
Reiter R, Gais P, Jütting U, et al: Aurora kinase A messenger RNA overexpression is correlated with tumor progression and shortened survival in head and neck squamous cell carcinoma. Clin Cancer Res. 12:5136–5141. 2006. View Article : Google Scholar : PubMed/NCBI | |
|
Rugge M, Fassan M, Zaninotto G, et al: Aurora kinase A in Barrett’s carcinogenesis. Hum Pathol. 41:1380–1386. 2010. | |
|
Lo Iacono M, Monica V, Saviozzi S, Ceppi P, Bracco E, Papotti M and Scagliotti GV: Aurora Kinase A expression is associated with lung cancer histological-subtypes and with tumor de-differentiation. J Transl Med. 9:1002011.PubMed/NCBI | |
|
Sillars-Hardebol AH, Carvalho B, de Wit M, et al: Identification of key genes for carcinogenic pathways associated with colorectal adenoma-to-carcinoma progression. Tumour Biol. 31:89–96. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Dar AA, Zaika A, Piazuelo MB, et al: Frequent overexpression of Aurora Kinase A in upper gastrointestinal adenocarcinomas correlates with potent antiapoptotic functions. Cancer. 112:1688–1698. 2008. View Article : Google Scholar | |
|
El-Rifai W and Powell SM: Molecular and biologic basis of upper gastrointestinal malignancy. Gastric carcinoma. Surg Oncol Clin N Am. 11:273–291. 2002. View Article : Google Scholar : PubMed/NCBI | |
|
Shaheen N and Ransohoff DF: Gastroesophageal reflux, Barrett esophagus, and esophageal cancer: scientific review. JAMA. 287:1972–1981. 2002. View Article : Google Scholar : PubMed/NCBI | |
|
Jee HJ, Kim AJ, Song N, Kim HJ, Kim M, Koh H and Yun J: Nek6 overexpression antagonizes p53-induced senescence in human cancer cells. Cell Cycle. 9:4703–4710. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Yin MJ, Shao L, Voehringer D, Smeal T and Jallal B: The serine/threonine kinase Nek6 is required for cell cycle progression through mitosis. J Biol Chem. 278:52454–52460. 2003. View Article : Google Scholar : PubMed/NCBI | |
|
Belham C, Roig J, Caldwell JA, Aoyama Y, Kemp BE, Comb M and Avruch J: A mitotic cascade of NIMA family kinases. Nercc1/Nek9 activates the Nek6 and Nek7 kinases. J Biol Chem. 278:34897–34909. 2003. View Article : Google Scholar : PubMed/NCBI | |
|
O’Regan L and Fry AM: The Nek6 and Nek7 protein kinases are required for robust mitotic spindle formation and cytokinesis. Mol Cell Biol. 29:3975–3990. 2009.PubMed/NCBI | |
|
Nassirpour R, Shao L, Flanagan P, Abrams T, Jallal B, Smeal T and Yin MJ: Nek6 mediates human cancer cell transformation and is a potential cancer therapeutic target. Mol Cancer Res. 8:717–728. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Takeno A, Takemasa I, Doki Y, et al: Integrative approach for differentially overexpressed genes in gastric cancer by combining largescale gene expression profiling and network analysis. Br J Cancer. 99:1307–1315. 2008. View Article : Google Scholar | |
|
Lagergren J: Increased incidence of adenocarcinoma of the esophagus and cardia. Reflux and obesity are strong and independent risk factors according to the SECC study. Lakartidningen J. 97:1950–1953. 2000.(In Swedish). | |
|
Erichsen R, Robertson D, Farkas DK, Pedersen L, Pohl H, Baron J and Sorensen HT: Erosive reflux disease increases risk for esophageal adenocarcinoma risk, compared with non-erosive reflux. Clin Gastroenterol Hepatol. Jan 12–2012.(Epub ahead of print). | |
|
Wu SR, Li CF, Hung LY, Huang AM, Tseng JT, Tsou JH and Wang J: MCCAAT/enhancer-binding protein delta mediates tumor necrosis factor alpha-induced Aurora kinase C transcription and promotes genomic instability. J Biol Chem. 286:28662–28670. 2011. View Article : Google Scholar | |
|
Shakespear MR, Halili MA, Irvine KM, Fairlie DP and Sweet MJ: Histone deacetylases as regulators of inflammation and immunity. Trends Immunol. 32:335–343. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Berger J and Bird A: Role of MBD2 in gene regulation and tumorigenesis. Biochem Soc Trans. 33:1537–1540. 2005. View Article : Google Scholar : PubMed/NCBI | |
|
Fujita H, Fujii R, Aratani S, Amano T, Fukamizu A and Nakajima T: Antithetic effects of MBD2a on gene regulation. Mol Cell Biol. 23:2645–2657. 2003. View Article : Google Scholar : PubMed/NCBI | |
|
Müller-Tidow C, Kügler K, Diederichs S, et al: Loss of expression of HDAC-recruiting methyl-CpG-binding domain proteins in human cancer. Br J Cancer. 85:1168–1174. 2001.PubMed/NCBI | |
|
Kanai Y, Ushijima S, Nakanishi Y and Hirohashi S: Reduced mRNA expression of the DNA demethylase, MBD2, in human colorectal and stomach cancers. Biochem Biophys Res Commun. 2:962–966. 1999. View Article : Google Scholar : PubMed/NCBI | |
|
Chen ZP, Gu DS, Zhou ZP, et al: Decreased expression of MBD2 and MBD4 gene and genomic-wide hypomethylation in patients with primary immune thrombocytopenia. Hum Immunol. 72:486–491. 2011. View Article : Google Scholar : PubMed/NCBI |
