Significant association of EED promoter hypomethylation with colorectal cancer

  • Authors:
    • Xiuru Ying
    • Ranran Pan
    • Jie Zhong
    • Boyi Wu
    • Yuting Jiang
    • Jieer Ying
    • Cong Zhou
    • Jie Dai
    • Shuangying Zhao
    • Yinan Shen
    • Wei Zhang
    • Shiwei Duan
  • View Affiliations

  • Published online on: June 4, 2019     https://doi.org/10.3892/ol.2019.10432
  • Pages: 1564-1570
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

Colorectal cancer (CRC) is one of the most common and serious types of malignancy worldwide. The embryonic ectoderm development (EED) gene is important to maintain transcriptional repressive states of genes over successive cell generations. The present study aimed to investigate the association between EED methylation and CRC. A total of 111 CRC tissue samples, 111 paired para‑tumor tissues and 20 colorectal normal tissues were obtained for EED methylation assay, which was performed using a quantitative methylation‑specific polymerase chain reaction. The percentage of methylated reference was calculated to represent the DNA methylation level. A dual‑luciferase reporter gene assay was used to detect the gene promoter activity of a EED fragment. The current results revealed a significant difference in the EED methylation levels among tumor, para‑tumor and normal colorectal tissues (tumor vs. para‑tumor vs. normal, 5.03±4.61 vs. 8.65±11.50 vs. 40.12±45.31; F=45.014; P<0.0001). The dual‑luciferase reporter gene assay demonstrated that the transcriptional activity of recombinant pGL3‑EED plasmid was significantly higher compared with that of the pGL3‑Basic control vector (fold‑change, 3.15; P=0.014), which suggests the EED fragment can promote gene expression. In conclusion, the present study demonstrated that EED hypomethylation may be an important factor associated with CRC.

Introduction

Colorectal cancer (CRC) is one of the most common and serious malignancies in the world, particularly in developed countries (1). In England and Wales between 1991 and 1998, the 5-year survival rate of CRC in the initial stages was 60–95%, markedly decreasing to 35% in stages where lymph node metastases are detected (2). The lifetime risk of CRC is ~5%, and almost 45% of patients succumb to CRC, despite treatment (1). In China, although CRC is not the leading cause of cancer-associated mortality, the incidence and mortality rates of CRC have been increasing over the past 20 years, and they have been predicted to continue to increase if no effective intervention occurs (3).

The initiation and progression of human cancer depends on both genetic alterations and epigenetic changes (4). The carcinogenesis of CRC has been revealed to be involved in epigenetic alterations, including DNA methylation and histone modifications (5,6). Gene silencing caused by aberrant promoter methylation acts as one of the most significant epigenetic mechanisms (7). In CRC, methylation alterations frequently occur in chromosomes 1, 5, 6, 8, 11, 13, 18, 19, 21 and 22 (8). Differentially methylated DNA regions have been identified in both primary tumor tissues and blood samples (9), and more recently in cell-free DNA (10).

The embryonic ectoderm development (EED) gene, encodes a member of the Polycomb-group (PcG) family, which has been demonstrated to maintain the transcriptional repressive states of genes over successive cell generations (11). PcG genes have been revealed to be highly mutated in a number of human diseases (12). In addition, PcG proteins have been identified to be associated with cancer development (13) and proposed as potential targets for cancer therapeutic strategies (14). EED has been identified to mediate the repression of gene activity through histone deacetylation (15). EED hypermethylation has been detected in cholangiocarcinoma tumors (16). Furthermore, high EED expression levels have been demonstrated to be associated with CRC (17). However, to the best of our knowledge, no EED methylation in CRC has been reported. In light of previous findings, the present study aimed to investigate the association between EED methylation and CRC.

Materials and methods

Tissue specimens

In the past 5 years, a total of 111 CRC tissue samples, 111 paired para-tumor tissues and 20 colorectal normal tissues were collected from patients diagnosed at Shaoxing People's Hospital (Shaoxing, China), Zhejiang Province Cancer Hospital (Hangzhou, China) and Nanjing Chinese Medicine Hospital (Nanjing, China). Clinical diagnosis was determined on the basis of colonoscopy findings and histological assessment. The types of cancer were staged according to the seventh edition of the American Joint Committee on Cancer staging system (18). The mean age of the patients was 60.96±11.66 years and the cohort included 72 males and 39 females. All individuals were of Han Chinese ethnicity from Eastern China. The specimens were freshly obtained and stored at −80°C. The study protocol was approved by the Ethical Committees of Shaoxing People's Hospital (Shaoxing, China), Zhejiang Province Cancer Hospital (Hangzhou, China), Nanjing Chinese Medicine Hospital (Nanjing, China) and Ningbo University (Ningbo, China). The number of institutional review board approval was IRB-2018-28. Written informed consent was obtained from all participants.

DNA methylation assay

DNA extraction and bisulfite conversion were performed as described previously (19). Quantitative methylation-specific polymerase chain reaction (qMSP) was used to detect the methylation levels. qMSP was performed as described in our previous studies (2022). The percent of methylated reference (PMR) was used to represent gene methylation (23,24). The genomic position and function annotations of EED were obtained from the University of California Santa Cruz genome browser (GRCh37/hg19; http://genome.ucsc.edu/index.html). The primer sequences of EED were 5′-GAGGCGGAGGAATATGTT-3′ for the forward primer and 5′-TCACTACTCAACTTCTACTTCT-3′ for the reverse primer. The primer sequences of ACTB were 5′-TGGTGATGGAGGAGGTTTAGTAAGT-3′ for the forward primer and 5′-AACCAATAAAACCTACTCCTCCCTTAA-3′ for the reverse primer. The current study used qMSP with internal negative and positive controls, and a reference gene control for the methylation assay of EED.

The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) data analysis

EED methylation and EED expression datasets were retrieved from the online resource [http://www.cbioportal.org/; colorectal Adenocarcinoma (TCGA, Provisional)] to analyze the association between EED methylation and EED expression in patients with CRC. The dataset GSE32323 (25) was downloaded from the GEO database (https://www.ncbi.nlm.nih.gov/gds/) to provide data regarding EED expression with and without 5′-AZA-deoxycytidine treatment in the cell lines COLO320, HT29 and RKO.

Dual-luciferase reporter gene assay

293T cells, obtained from the Chinese Academy of Sciences cell bank (Shanghai, China), were cultured as previously described (26). The fragment of EED (−300 bp to +390 bp) was chemically synthesized according to the manufacturer's protocol (TransLipid HL Transfection Reagent; TransGen Biotech, Co., Ltd., Beijing, China) and digested with XhoI and KpnI (New England BioLabs, Inc., Ipswich, MA, USA). The fragment was then purified by Cycle Pure kit (Omega Bio-Tek, Inc., Norcross, GA, USA) and the target DNA fragment was cloned into a pGL3 vector (Promega Cooperation, Madison, WI, USA) using DNA Ligation kit (Takara Bio, Inc., Otsu, Japan). The empty pGL3 basic vector was used as the negative control and the pGL3 promoter vector (both Promega Cooperation, Madison, WI, USA) was used as the positive control, which contained an SV40 promoter upstream of the luciferase gene. The plasmid transfection and the detection of luciferase activity were performed as previously described (23,27).

Statistical analysis

SPSS 16.0 software (SPSS, Inc., Chicago, IL, USA) was used for all statistical analysis. Data that were not normally distributed are presented as the median (interquartile range) and variables that were normally distributed are presented as the mean ± standard deviation. Mann-Whitney U test, Kruskal-Wallis and unpaired Student's t-test were applied to analyze the baseline characteristics among the 111 patients with CRC. Association of PMR difference with the clinical characteristics in 111 paired samples was performed by χ2 test. Analysis of variance test was applied to compare EED methylation levels among tumor, para-tumor and normal colorectal samples, and the Bonferroni correction was used for the post hoc test. To analyze the results of the dual-luciferase reporter assay, an analysis of variance and Bonferroni's correction were also used. Spearman's correlation test was applied to evaluate the correlation between EED mRNA expression level and methylation in 369 patients with CRC from TCGA data portal. P<0.05 was considered to indicate a statistically significant difference.

Results

In the present study, a total of 111 CRC tumor tissues, 111 paired para-tumor tissues and 20 colorectal normal tissues were obtained to investigate the role of EED promoter methylation in CRC.

Characteristics of the target sequence on the EED promoter region

The genomic region and target sequence of EED are presented in Fig. 1A. One CpG site was located in the primers of the tested fragment (hg19, chr11:85956259-85956348). The capillary electrophoresis result revealed a pMSP product with a length of 90 base pairs, which was expected, and Sanger sequencing demonstrated that the amplified fragment matched the target sequence (Fig. 1B).

Baseline characteristics of the methylation levels among patients

Subsequently, no significant difference was identified between EED methylation levels and clinical characteristics, including sex, age, tumor location, tumor size, differentiation and lymph node metastasis (Table I). However, when the PMR difference value between methylation levels of tumor and para-tumor samples was used to perform the χ2 test, the only significant association of PMR difference with clinical characteristics was identified for tumor location (P=0.039; Table II).

Table I.

Baseline characteristics among 111 patients with colorectal cancer.

Table I.

Baseline characteristics among 111 patients with colorectal cancer.

Clinical characteristicsNo. (n=111)Percentage of methylated reference in tumorP-value
Sex 0.587a
  Male724.73 (2.52,6.67)
  Female394.41 (1.40,6.31)
Age, years 0.165a
  ≤65744.79 (2.55,6.63)
  >65373.33 (1.42,6.08)
Tumor location 0.929b
  Colon464.70 (1.91,6.38)
  Rectum564.43 (2.50,6.62)
  Colon and rectum94.78 (1.30,7.69)
Tumor size, cm 0.673a
  ≤6964.42 (2.21,6.62)
  >6155.76 (2.06,5.94)
Differentiation 0.222c
  High and medium157.58±8.86
  Low and none964.63±3.44
Lymph node metastasis 0.435a
  Positive564.70 (2.60,6.55)
  Negative554.44 (1.44,6.53)

{ label (or @symbol) needed for fn[@id='tfn1-ol-0-0-10432'] } Data that do not conform to normal distribution are presented as median (lower quartile, upper quartile). Variables that conform to normal distribution are presented as the mean ± standard deviation.

a Non-parametric test (Mann-Whitney U test) was applied.

b Non-parametric test (Kruskal-Wallis) was applied.

c Unpaired Student's t test was applied.

Table II.

Associations between the PMR differences and clinical characteristics.

Table II.

Associations between the PMR differences and clinical characteristics.

Clinical characteristicsNo. (n=111)P-value
Sex 0.643
  Male72
  Female39
Age, years 0.590
  ≤6574
  >6537
Tumor location 0.039
  Colon46
  Rectum56
  Colon and rectum9
Tumor size, cm 0.071
  ≤696
  >615
Differentiation 0.119
  High and medium15
  Low and none96
Lymph node metastasis 0.286
  Positive56
  Negative55

[i] Data were analyzed by χ2 test. PMR difference value between methylation levels of tumor and para-tumor samples was used to perform this test. PMR, percentage of methylated reference.

Notably, a significant difference of EED methylation levels among tumor, para-tumor and normal colorectal tissues was revealed (tumor vs. para-tumor vs. normal: 5.03±4.61 vs. 8.65±11.50 vs. 40.12±45.31; F=45.014; P<0.0001; Fig. 2). Following Bonferroni's correction the results were as follows: Tumor vs. para-tumor, P=0.237; tumor vs. normal tissue, P<0.0001; and para-tumor vs. normal tissue, P<0.0001 (Fig. 2). Previous studies have demonstrated that bisulfite sequencing PCR and qMSP can yield similar conclusions (28,29). Bisulfite sequencing PCR is a reliable and accurate method; however, it is labor intensive and therefore only applicable for methylation in a limited number of samples.

Diagnostic value of EED methylation

A further estimation of the diagnostic value of EED methylation for CRC revealed an area under the curve (AUC) of 0.574 (95% CI, 0.498–0.650) with a sensitivity of 33.3% and a specificity of 89.2% between tumor and para-tumor tissues (median PMR, 4.54 vs. 4.90%; P=0.056; Fig. 3). Furthermore, an AUC of 0.855 (95% CI, 0.729–0.981) with a sensitivity of 80% and a specificity of 89.2% was identified between tumor tissues and normal colorectal tissues (median PMR, 4.54 vs. 18.97%; P<0.0001; Fig. 3). In addition, an AUC of 0.787 (95% CI, 0.657–0.917) with a sensitivity of 65% and a specificity of 86.5% was revealed between para-tumor tissues and normal colorectal tissues (median PMR, 4.90 vs. 18.97%; P<0.0001; Fig. 3).

Characteristics of EED expression and methylation

A dual-luciferase reporter gene assay was performed to evaluate whether the EED fragment (−300 bp to +390 bp) was able to regulate gene expression. The dual-luciferase assay demonstrated that the transcriptional activity of recombinant pGL3-EED plasmid was significantly higher compared with the pGL3-Basic control vector (pGL3-EED vs. pGL3-Basic vs. pGL3-Promoter: 2.05±0.19 vs. 0.65±0.02 vs. 30.27±0.26; F=16589.76; P<0.0001; pGL3-EED vs. pGL3-Basic: fold-change, 3.15; P=0.014; pGL3-EED vs. pGL3-Promoter: P<0.0001; pGL3-Basic vs. pGL3-Promoter: P<0.0001; Fig. 4), which indicates that the EED fragment is able to promote gene expression.

Furthermore, EED mRNA expression and methylation data of patients with CRC were obtained from TCGA online database to investigate their correlation. Spearman correlation test revealed that EED mRNA expression level was inversely correlated with methylation (r=−0.248; P<0.0001; Fig. 5). In addition, a further analysis of GEO data (GSE32323) demonstrated that EED expression level in three CRC cell lines (COLO320, HT29 and RKO) was increased following 5′-AZA-deoxycytidine treatment (average fold-change, 1.44; Fig. 6). In summary, the present results indicate that EED hypomethylation is likely to upregulate EED expression and eventually increase the risk of CRC.

Discussion

In the current study, EED methylation levels were detected in 111 pairs of CRC tumor and para-tumor tissues from patients with CRC and 20 colorectal tissues from normal controls. The results revealed that EED hypomethyation was significantly associated with the risk of CRC. In addition, the dual-luciferase reporter gene assay demonstrated that the EED fragment exhibited promoter activity. Further bioinformatics analyses revealed that EED methylation was inversely correlated with EED expression and demethylation treatment was identified to upregulate EED expression.

EED is a key component of the polycomb repressive complex 2 (PRC2) (30), which can mediate epigenetic silencing of genes associated with worse survival of patients with colon cancer (31). Higher expression of EED and two other PRC2 components has been demonstrated to contribute to the progression of CRC (17).

Polymorphism of EED gene has been identified to be associated with the lymph node metastatic process of CRC (32). In addition, EED expression has been demonstrated to be regulated by interleukin-22 and signal transducer and activator of transcription 3 (33). EED mRNA levels are significantly higher in CRC tissues compared with non-cancerous tissues (17). The dual-luciferase reporter gene assay performed in the current study demonstrated an enhanced transcriptional activity of the cloned EED fragment. Furthermore, data from TCGA and GEO databases suggested that EED methylation was associated with decreased expression levels of EED. This supports the hypothesis that EED hypomethylation may promote CRC via upregulation of EED expression. The present study identified that EED expression may be regulated by the methylation of its promoter, which may promote understanding of the role of EED in CRC.

Previous studies have revealed that DNA cytosine modifications serve an important role in cancer biology, and provide promising biomarkers for cancer diagnosis and prognosis evaluation (10,34). Several epigenetic biomarkers have been studied for the diagnosis of CRC, including SEPT9 (35), BMP3, NDRG4 (36) and hMLH1 (37). The ROC curves generated in the current study demonstrated that EED hypomethylation is a good biomarker for the diagnosis of CR. Tumor vs. para-tumor revealed a sensitivity of 33.3% and a specificity of 89.2%. Tumor vs. normal tissue analysis demonstrated a sensitivity of 80% and a specificity of 89.2%. Finally, para-tumor vs. normal tissue revealed a sensitivity of 65% and a specificity of 86.5%.

However, there were a number of limitations of the present study. Firstly, the GEO analyses to investigate the effect of demethylation agent on EED expression involved data from only three cell lines. Furthermore, a comparison of EED mRNA expression level between 17 paired tumor and non-cancerous tissues from TCGA database yielded an insignificant result (4.45±0.58 vs. 4.32±0.50; P=0.393), although this discrepancy may be due to different ethnic samples and a small sample size. Future studies are required to confirm the current findings and further address the functional roles of EED methylation in CRC. In conclusion, the present results demonstrated that EED hypomethylation might be an important risk factor associated with CRC.

Acknowledgements

Not applicable.

Funding

The present study was supported by grants from the National Institutes of Health (grant no. U01CA217078) and the K. C. Wong Magna Fund in Ningbo University.

Availability of data and materials

All data generated or analyzed during the present study are included in this published article.

Authors' contributions

SD and WZ made substantial contributions to the conception and design. XY and RP analyzed and interpreted the data, drated and revised the manuscript, and agreed to be accountable for all aspects of the work. JZ, BW, JY and YJ contributed to the interpretation of data and completion of figures and tables. SZ, YS, CZ and JD contributed to performing the experiments and analyzing the data. All the authors have read and approved the final manuscript.

Ethical approval and consent to participate

Informed consent was provided by all participants prior to their inclusion within the study. The study was approved by the Ethical Committees of the Shaoxing People's Hospital, Zhejiang Province Cancer Hospital, Nanjing Chinese Medicine Hospital and Ningbo University.

Patient consent for publication

All patients have provided informed consent for the publication of any associated data and accompanying images.

Competing interests

The authors declare that they have no competing interests.

References

1 

Ferlay J, Shin HR, Bray F, Forman D, Mathers C and Parkin DM: Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. Int J Cancer. 127:2893–2917. 2010. View Article : Google Scholar : PubMed/NCBI

2 

Kanthan R, Senger JL and Kanthan SC: Molecular events in primary and metastatic colorectal carcinoma: A review. Patholog Res Int. 2012:5974972012.PubMed/NCBI

3 

Zheng ZX, Zheng RS, Zhang SW and Chen WQ: Colorectal cancer incidence and mortality in China, 2010. Asian Pac J Cancer Prev. 15:8455–8460. 2014. View Article : Google Scholar : PubMed/NCBI

4 

Fukushige S and Horii A: DNA methylation in cancer: A gene silencing mechanism and the clinical potential of its biomarkers. Tohoku J Exp Med. 229:173–185. 2013. View Article : Google Scholar : PubMed/NCBI

5 

van Engeland M, Derks S, Smits KM, Meijer GA and Herman JG: Colorectal cancer epigenetics: Complex simplicity. J Clin Oncol. 29:1382–1391. 2011. View Article : Google Scholar : PubMed/NCBI

6 

Grady WM and Carethers JM: Genomic and epigenetic instability in colorectal cancer pathogenesis. Gastroenterology. 135:1079–1099. 2008. View Article : Google Scholar : PubMed/NCBI

7 

Sakai E, Nakajima A and Kaneda A: Accumulation of aberrant DNA methylation during colorectal cancer development. World J Gastroenterol. 20:978–987. 2014. View Article : Google Scholar : PubMed/NCBI

8 

Sipos F, Mũzes G, Patai AV, Fũri I, Péterfia B, Hollósi P, Molnár B and Tulassay Z: Genome-wide screening for understanding the role of DNA methylation in colorectal cancer. Epigenomics. 5:569–581. 2013. View Article : Google Scholar : PubMed/NCBI

9 

Song BP, Jain S, Lin SY, Chen Q, Block TM, Song W, Brenner DE and Su YH: Detection of hypermethylated vimentin in urine of patients with colorectal cancer. J Mol Diagn. 14:112–119. 2012. View Article : Google Scholar : PubMed/NCBI

10 

Li W, Zhang X, Lu X, You L, Song Y, Luo Z, Zhang J, Nie J, Zheng W, Xu D, et al: 5-Hydroxymethylcytosine signatures in circulating cell-free DNA as diagnostic biomarkers for human cancers. Cell Res. 27:1243–1257. 2017. View Article : Google Scholar : PubMed/NCBI

11 

Schumacher A, Lichtarge O, Schwartz S and Magnuson T: The murine Polycomb-group gene eed and its human orthologue: Functional implications of evolutionary conservation. Genomics. 54:79–88. 1998. View Article : Google Scholar : PubMed/NCBI

12 

Piunti A and Shilatifard A: Epigenetic balance of gene expression by Polycomb and COMPASS families. Science. 352:aad97802016. View Article : Google Scholar : PubMed/NCBI

13 

Du J, Li L, Ou Z, Kong C, Zhang Y, Dong Z, Zhu S, Jiang H, Shao Z, Huang B and Lu J: FOXC1, a target of polycomb, inhibits metastasis of breast cancer cells. Breast Cancer Res Treat. 131:65–73. 2012. View Article : Google Scholar : PubMed/NCBI

14 

Scelfo A, Piunti A and Pasini D: The controversial role of the Polycomb group proteins in transcription and cancer: How much do we not understand Polycomb proteins? FEBS J. 282:1703–1722. 2015. View Article : Google Scholar : PubMed/NCBI

15 

Yu JI, Kang IH, Seo GS, Choi SC, Yun KJ and Chae SC: Promoter polymorphism of the EED gene is associated with the susceptibility to ulcerative colitis. Dig Dis Sci. 57:1537–1543. 2012. View Article : Google Scholar : PubMed/NCBI

16 

Sriraksa R, Zeller C, Dai W, Siddiq A, Walley AJ, Limpaiboon T and Brown R: Aberrant DNA methylation at genes associated with a stem cell-like phenotype in cholangiocarcinoma tumors. Cancer Prev Res (Phila). 6:1348–1355. 2013. View Article : Google Scholar : PubMed/NCBI

17 

Liu YL, Gao X, Jiang Y, Zhang G, Sun ZC, Cui BB and Yang YM: Expression and clinicopathological significance of EED, SUZ12 and EZH2 mRNA in colorectal cancer. J Cancer Res Clin Oncol. 141:661–669. 2015. View Article : Google Scholar : PubMed/NCBI

18 

Pike JG, Berardinucci G, Hamburger B and Kiruluta G: The surgical management of urinary incontinence in myelodysplastic children. J Pediatr Surg. 26:466–471. 1991. View Article : Google Scholar : PubMed/NCBI

19 

Chen X, Yang Y, Liu J, Li B, Xu Y, Li C, Xu Q, Liu G, Chen Y, Ying J and Duan S: NDRG4 hypermethylation is a potential biomarker for diagnosis and prognosis of gastric cancer in Chinese population. Oncotarget. 8:8105–8119. 2017.PubMed/NCBI

20 

Chen R, Hong Q, Jiang J, Chen X, Jiang Z, Wang J, Liu S, Duan S and Shi S: AGTR1 promoter hypermethylation in lung squamous cell carcinoma but not in lung adenocarcinoma. Oncol Lett. 14:4989–4994. 2017. View Article : Google Scholar : PubMed/NCBI

21 

Yang Y, Chen X, Hu H, Jiang Y, Yu H, Dai J, Mao Y and Duan S: Elevated UMOD methylation level in peripheral blood is associated with gout risk. Sci Rep. 7:111962017. View Article : Google Scholar : PubMed/NCBI

22 

Li B, Chen X, Jiang Y, Yang Y, Zhong J, Zhou C, Hu H and Duan S: CCL2 promoter hypomethylation is associated with gout risk in Chinese Han male population. Immunol Lett. 190:15–19. 2017. View Article : Google Scholar : PubMed/NCBI

23 

Hu H, Chen X, Wang C, Jiang Y, Li J, Ying X, Yang Y, Li B, Zhou C, Zhong J, et al: The role of TFPI2 hypermethylation in the detection of gastric and colorectal cancer. Oncotarget. 8:84054–84065. 2017. View Article : Google Scholar : PubMed/NCBI

24 

Yang B, Du Z, Gao YT, Lou C, Zhang SG, Bai T, Wang YJ and Song WQ: Methylation of Dickkopf-3 as a prognostic factor in cirrhosis-related hepatocellular carcinoma. World J Gastroenterol. 16:755–763. 2010. View Article : Google Scholar : PubMed/NCBI

25 

Khamas A, Ishikawa T, Shimokawa K, Mogushi K, Iida S, Ishiguro M, Mizushima H, Tanaka H, Uetake H and Sugihara K: Screening for epigenetically masked genes in colorectal cancer Using 5-Aza-2′-deoxycytidine, microarray and gene expression profile. Cancer Genomics Proteomics. 9:67–75. 2012.PubMed/NCBI

26 

Shen Z, Chen X, Li Q, Zhou C, Xu Y, Yu R, Ye H, Li J and Duan S: Elevated methylation of CMTM3 promoter in the male laryngeal squamous cell carcinoma patients. Clin Biochem. 49:1278–1282. 2016. View Article : Google Scholar : PubMed/NCBI

27 

Ji H, Wang Y, Liu G, Xu X, Dai D, Chen Z, Zhou D, Zhou X, Han L, Li Y, et al: OPRK1 promoter hypermethylation increases the risk of Alzheimer's disease. Neurosci Lett. 606:24–29. 2015. View Article : Google Scholar : PubMed/NCBI

28 

Demokan S, Chuang AY, Pattani KM, Sidransky D, Koch W and Califano JA: Validation of nucleolar protein 4 as a novel methylated tumor suppressor gene in head and neck cancer. Oncol Rep. 31:1014–1020. 2014. View Article : Google Scholar : PubMed/NCBI

29 

Park JY, Kim D, Yang M, Park HY, Lee SH, Rincon M, Kreahling J, Plass C, Smiraglia DJ, Tockman MS and Kim SJ: Gene silencing of SLC5A8 identified by genome-wide methylation profiling in lung cancer. Lung Cancer. 79:198–204. 2013. View Article : Google Scholar : PubMed/NCBI

30 

Margueron R and Reinberg D: The Polycomb complex PRC2 and its mark in life. Nature. 469:343–349. 2011. View Article : Google Scholar : PubMed/NCBI

31 

Nagarsheth N, Peng D, Kryczek I, Wu K, Li W, Zhao E, Zhao L, Wei S, Frankel T, Vatan L, et al: PRC2 epigenetically silences Th1-Type chemokines to suppress effector T-cell trafficking in colon cancer. Cancer Res. 76:275–282. 2016. View Article : Google Scholar : PubMed/NCBI

32 

Seo GS, Yu JI, Chae SC, Park WC, Shin SR, Yoo ST, Choi SC and Lee SH: EED gene polymorphism in patients with colorectal cancer. Int J Biol Markers. 28:274–279. 2013. View Article : Google Scholar : PubMed/NCBI

33 

Sun D, Lin Y, Hong J, Chen H, Nagarsheth N, Peng D, Wei S, Huang E, Fang J, Kryczek I and Zou W: Th22 cells control colon tumorigenesis through STAT3 and polycomb repression complex 2 signaling. Oncoimmunology. 5:e10827042016. View Article : Google Scholar : PubMed/NCBI

34 

Das PM and Singal R: DNA methylation and cancer. J Clin Oncol. 22:4632–4642. 2004. View Article : Google Scholar : PubMed/NCBI

35 

Ravegnini G, Zolezzi Moraga JM, Maffei F, Musti M, Zenesini C, Simeon V, Sammarini G, Festi D, Hrelia P and Angelini S: Simultaneous analysis of SEPT9 promoter methylation status, micronuclei frequency, and folate-related gene polymorphisms: The potential for a novel blood-based colorectal cancer biomarker. Int J Mol Sci. 16:28486–28497. 2015. View Article : Google Scholar : PubMed/NCBI

36 

Kadiyska T and Nossikoff A: Stool DNA methylation assays in colorectal cancer screening. World J Gastroenterol. 21:10057–10061. 2015. View Article : Google Scholar : PubMed/NCBI

37 

Wang Y, Li D, Li X, Teng C, Zhu L, Cui B, Zhao Y and Hu F: Prognostic significance of hMLH1/hMSH2 gene mutations and hMLH1 promoter methylation in sporadic colorectal cancer. Med Oncol. 31:392014. View Article : Google Scholar : PubMed/NCBI

Related Articles

Journal Cover

August 2019
Volume 18 Issue 2

Print ISSN: 1792-1074
Online ISSN:1792-1082

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
APA
Ying, X., Pan, R., Zhong, J., Wu, B., Jiang, Y., Ying, J. ... Duan, S. (2019). Significant association of EED promoter hypomethylation with colorectal cancer. Oncology Letters, 18, 1564-1570. https://doi.org/10.3892/ol.2019.10432
MLA
Ying, X., Pan, R., Zhong, J., Wu, B., Jiang, Y., Ying, J., Zhou, C., Dai, J., Zhao, S., Shen, Y., Zhang, W., Duan, S."Significant association of EED promoter hypomethylation with colorectal cancer". Oncology Letters 18.2 (2019): 1564-1570.
Chicago
Ying, X., Pan, R., Zhong, J., Wu, B., Jiang, Y., Ying, J., Zhou, C., Dai, J., Zhao, S., Shen, Y., Zhang, W., Duan, S."Significant association of EED promoter hypomethylation with colorectal cancer". Oncology Letters 18, no. 2 (2019): 1564-1570. https://doi.org/10.3892/ol.2019.10432