Genome-wide DNA methylation assay reveals novel candidate biomarker genes in cervical cancer

Figures & data

Figure 1. Unsupervised clustering analysis of the normal cervical tissue (N), CIN3 tissue (CIN3), and the cervical cancer tissue (CC). The color gradient green to red displays the β-value and can range from 0–1.

Table 1. Mean β-values for CpG sites represented in the heat map in Figure 1

		Normal tissue			CIN3 tissue			Cancer tissue
CpG ID	Gene name	Mean	SD	n	Mean	SD	n	Mean	SD	n
cg18803079	EFCAB7, DLEU2L	0.78	0.04	20	0.58	0.10	18	0.53	0.03	6
cg21581312	LOC723972	0.84	0.04	20	0.62	0.11	18	0.50	0.07	6
cg17461271	NA	0.79	0.05	20	0.60	0.11	18	0.54	0.05	6
cg12050434	NA	0.65	0.06	20	0.44	0.12	18	0.28	0.07	6
cg13070650	STK3	0.57	0.12	20	0.79	0.08	18	0.76	0.10	6
cg01262337	TKT	0.39	0.12	20	0.21	0.09	18	0.17	0.03	6
cg00470565	NA	0.62	0.11	20	0.85	0.19	18	0.65	0.09	6
cg02116612	MGLL	0.45	0.10	20	0.26	0.12	18	0.24	0.08	6
cg24662154	EXT2	0.06	0.06	20	0.16	0.08	18	0.13	0.06	6
cg14156405	RGS7	0.03	0.01	20	0.16	0.16	18	0.40	0.28	6
cg16241932	ZDHHC14	0.39	0.31	20	0.77	0.21	18	0.63	0.36	6
cg08272731	LHX8	0.05	0.04	20	0.22	0.18	18	0.47	0.22	6
cg03861379	NA	0.59	0.14	20	0.77	0.12	18	0.78	0.09	6
cg23243867	ST6GALNAC5	0.02	0.02	20	0.13	0.14	18	0.40	0.22	6
cg21632158	NA	0.06	0.05	20	0.19	0.14	18	0.40	0.17	6
cg00532449	NA	0.12	0.11	20	0.30	0.17	18	0.40	0.26	6
cg20784693	HDAC4	0.71	0.15	20	0.50	0.17	18	0.63	0.22	6
cg21183256	NA	0.07	0.04	20	0.22	0.17	18	0.53	0.17	6
cg17985646	TBX20	0.05	0.05	20	0.21	0.17	18	0.45	0.22	6
cg22617898	RAB3A	0.80	0.13	20	0.61	0.17	18	0.56	0.15	6
cg22762215	NA	0.06	0.05	20	0.21	0.17	18	0.48	0.22	6
cg20302133	KCNA3	0.01	0.01	20	0.18	0.23	18	0.42	0.31	6
cg22721334	ZSCAN18	0.01	0.02	20	0.14	0.16	18	0.39	0.21	6
cg23385248	NA	0.34	0.18	20	0.14	0.11	18	0.11	0.12	6
cg18075755	C1QTNF7	0.48	0.28	20	0.17	0.22	18	0.32	0.29	6

NA, not annotated. Bold-face numbers indicate genes selected as candidate biomarkers (see Table 4).

Figure 2. Distribution of hypermethylated and hypomethylated CpG locus in CpG island (CGI), CpG island shore, CpG island shelves and other regions.

Table 2. Hypomethylated gene promoter regions in cancer tissues compared with the normal tissues

Gene name	Function	Region	∆β	Adjust P value	Abberrantly methylated in
AIM2	Inflammasome activity	TSS1500 TSS200	-0.34 -0.33	0.004 0.002	Leukemia^31 pancreratic cancer^30
B3GALT6	Transmembrane protein	1st Exon	-0.32	0.001
BST2	Expressed in B-cells	1st Exon	-0.31	0.002	Lupus,^54 glioblastoma^55
BTN3A3	Inhibitor of immune response	5′UTR	-0.28	0.000
C1orf150	Not known	TSS200	-0.36	0.038
CASP10	Cell apoptosis	TSS200	-0.33	0.026
CLEC2B	Cell adhesion, cell-cell signaling, immune response	TSS1500	-0.31	0.033
CST7	Immune regulation	TSS1500	-0.31	0.028
CSTA	Epidermal development	TSS1500	-0.33	0.034
DAPP1	B-cell adhesion	TSS200 5′UTR	-0.32 -0.30	0.024 0.034
EDARADD	Ectodermal dysplasia	1st Exon	-0.28	0.035
FAM26F	Not known	5′UTR	-0.28	0.001
GBP4	Cell growth, anti-viral activity	TSS200	-0.37	0.007
GPR55	Cell proliferation	5′UTR	-0.29	0.042
HAVCR2	Regulates T-cells	5′UTR 1st Exon	-0.30 -0.30	0.030 0.028
HBBP1	hemoglobin, β pseudogene 1	TSS200	-0.35	0.010
HLA-DPB1	Immune response	1st Exon	-0.36	0.001
IGLL1	B-cell regulation	TSS200	-0.35	0.017
IL12RB1	Immune response	TSS200	-0.31	0.006	Atherosclerosis^56
MARCO	Innate antimicrobial immune system	TSS200	-0.30	0.032
MIR15B	Regulation of gene express	TSS1500	-0.35	0.007
NAGS	Urea cycle	1st Exon	-0.27	0.028
OR8B12	G protein-mediated transduction	1st Exon	-0.31	0.036
PATE3	Fertility and reproduction	5′UTR 1st Exon	-0.28 -0.28	0.049 0.046
PIGB	GPI-anchor biosynthesis	TSS1500	-0.32	0.005
PIK3R6	Leukocyte chemotaxis	5′UTR 1st Exon	-0.29 -0.28	0.030 0.016
PRTN3	Regulates immune cells	5′UTR 1st Exon	-0.29 -0.29	0.006 0.005	myeloid tissue^57
S1PR4	Cell-signaling in lymphoid tissue	TSS1500	-0.46	0.017
SDF4	Regulates calcium	TSS1500	-0.31	0.002
SIGLEC12	Immunoglobulin	5′UTR	-0.28	0.030
SPTA1	Cell shape	TSS1500	-0.35	0.002
STAT5A	JAK/STAT pathway	5′UTR	-0.30	0.003	lymphoma^58
VPREB1	B-cell differentiation	TSS200	-0.30	0.013

The list is merged of top-ten differentially methylated (according to Δβ-value) genes in the TSS1500-, TSS200-, 5′UTR- and 1st exon regions.

Table 3. Hypermethylated gene promoter regions in cancer tissues compared with the normal tissues

Gene name	Function	Region	∆β	Adjust p-value	Abberrantly methylated in
ACAN	Part of the extracellular matrix in cartilagenous tissue	TSS1500	0.41	< 0.001
ADCYAP1	Neurotransmitter	TSS1500	0.42	< 0.001	PTSD^59 cervical cancer^60
AJAP1	Adheren junctions	TSS1500	0.41	< 0.001	gastric cancer^61 oligidendrioma^62
AKAP2	Transcription factor	TSS1500	0.47	< 0.001
BARHL2	Homeobox-containing gene	TSS1500 5′UTR	0.46 0.57	< 0.001 < 0.001	Lung cancer^63
BOLL	Cell development	TSS200	0.52	< 0.001	Colorectal cancer,^64 lung cancer^65
C1orf114	ND	1st Exon	0.52	< 0.001
CTNND2	Encodes an adhesive junction associated protein	TSS200	0.56	< 0.001
CXCL12	Stromal cell-derived α chemokine member of the intercrine family	TSS200	0.55	< 0.001	Breast cancer,^66 rheumatoid arthr.^67 lung cancer,^68 glioma,^69 colorectal cancer,^70 pancreatic cancer^71
FAM159B	ND	5′UTR 1st Exon	0.55 0.55	< 0.001 < 0.001
FBXL7	F-box family member and function in phosphorylation-dependent ubiquitination	TSS200 5′UTR 1st Exon	0.52 0.56 0.56	< 0.001 < 0.001 < 0.001
GALR1	Inhibits adenylyl cyclase via a G- protein of the Gi/Go family	5′UTR	0.57	< 0.001	HNSCC^28
GYPC	Integral membrane glycoprotein regulates the mechanical stability of red cells	5′UTR 1st Exon	0.56 0.56	< 0.001 < 0.001
HYDIN	Involved in the ciliary function	1st Exon	0.54	< 0.001
KIF19	ND	TSS200	0.50	< 0.001
MARCH11	Ubiquitin-mediated protein sorting in the trans-Golgi network	TSS1500 TSS200	0.41 0.50	< 0.001 < 0.001
MIR129–2	Targets SOX4	TSS200	0.50	< 0.001	Gastric cancer^72
MIR663	Targets TGFB1	TSS1500	0.44	< 0.001
NAP1L3	NAP family are involved in neuronal differentiation	5′UTR	0.53	< 0.001
NPAS4	Transcriptional regulator	5′UTR	0.53	< 0.001
PTGDR	G-protein-coupled receptor	5′UTR	0.55	< 0.001	bladder cancer^73 neuroblastoma^74 asmathic pat.^75
SCT	Endocrine hormone	5′UTR 1st Exon TSS200	0.52 0.52 0.53	< 0.001 < 0.001 < 0.001
SORCS1	Membrane receptor	TSS200	0.61	< 0.001
SOX8	Transcription factor	TSS1500	0.41	< 0.001
TCERG1L	Transcription factor	1st Exon	0.53	< 0.001	colrectal cancer^76
TRIM58		1st Exon	0.52	< 0.001	Age-associated^77 hepatocellular carcinoma^78
TTYH1		1st Exon	0.57	< 0.001
VSTM2B		TSS1500	0.48	< 0.001
ZFP42		TSS1500	0.42	< 0.001	Renal cancer^79 esophageal cancer^80
ZIK1		5′UTR 1st Exon	0.61 0.61	< 0.001 < 0.001	Esophageal cancer^80
ZNF582		TSS201	0.58	< 0.001	Cervical cancer^27

The list is merged of top-ten differentially methylated (according to Δβ-value) genes in the TSS1500, TSS200, 5′UTR and 1st exon regions. ND, not determined; PTSD, post-traumatic stress disorder; HNSCC, head and neck squamous cell carcinoma.

Table 4. Methylation status and gene expression of candidate biomarker genes

Gene name	Function	Methylation status, CpGs on the array^1	Gene expression data set, FC GSE6791 GSE9750 GSE7803			Aberrantly methylated in cancers
ACAN	Part of the ECM	Hyper, (10/18)	-1.34*	-0.47	-0.38	−
AJAP1	Membrane protein	Hyper, (30/69)	-1.39*	-1.24	-1.31*	gastric cancer^61 oligidendrioma^62
BARHL2	TF	Hyper, (15/15)	−	−	−	lung cancer^63
BOLL	TF	Hyper, (8/17)	-1.55*	−	−	CRC^64 lung cancer^65
C1orf114	NA	Hyper, (9/13)	-1.38*	-1.08	-1.18*	−
FBXL7	ubiquitin	Hyper, (26/28)	-1.26	-1.89*	-1.66*	−
GALR1	galanin receptor	Hyper, (29/34)	-1.16*	-1.42	1.18	HNSCC^28
GYPC	erythrocyte surface protein	Hyper, (4/18)	-1.69*	-1.04	1.17	−
KCNA3	ion channel	Hyper, (9/19)	-1.48*	-1.01	1.46*	−
KIF19	microtubule-depolymerizing activity	Hyper, (12/22)	-1.24*	−	−	−
LHX8	TF	Hyper, (43/46)	-1.09	−	−	−
MIR663	micro RNA	Hyper, (11/11)	−	−	−	−
PTGDR	prostaglandin D(2) receptor	Hyper, (13/19)	-1.25*	-0.16	0.02	bladder cancer^73 neuroblastoma^74
RGS7	regulator of G protein signaling	Hyper, (18/35)	-1.38*	-0.30	-1.06	−
S1PR4	1-phosphate receptor	Hypo, (5/12)	-1.40*	1.26	-1.10	−
SORCS1	VPS10 domain containing receptor	Hyper, (10/20)	-1.42*	−	−	−
ST6GALNAC5	modify proteins on the cell surface	Hyper, (18/29)	1.24	1.08	-1.22	CRC^81
TBX20	TF	Hyper, (19/20)	-1.17*	−	−	−
TRIM58	NA	Hyper, (14/16)	-1.13*	1.16	-1.18	−
TTYH1	chloride anion channels	Hyper, (12/16)	-1.32*	1.05	-1.13	−
VSTM2B	NA	Hyper, (17/20)	−	−	−	−
ZIK1	TF	Hyper, (12/15)	-1.79*	−	−	esophageal cancer^80
ZNF582	TF	Hyper, (10/12)	-1.41*	−	−	cervical cancer^27
ZSCAN18	TF	Hyper, (24/38)	-2.20*	-3.68*	-3.34*	renal carcinoma^82

The gene expression was analyzed in three independent data sets. ¹Number of statistically significant CpG sites / total number CpG sites on the array. The statistically significant (P < 0.05) gene expressions are marked with (*). The negative value means lower expression in cancer compared with the normal tissue. The (−) sign indicates no data available. TF, transcription factor; CRC, colorectal cancer; HNSCC, head and neck squamous cell carcinoma.

Yamazaki J, Taby R, Vasanthakumar A, Macrae T, Ostler KR, Shen L, Kantarjian HM, Estecio MR, Jelinek J, Godley LA, et al. Effects of TET2 mutations on DNA methylation in chronic myelomonocytic leukemia. Epigenetics 2012; 7:201 - 7; http://dx.doi.org/10.4161/epi.7.2.19015; PMID: 22395470

 PubMed Web of Science ®Google Scholar

Pedersen KS, Bamlet WR, Oberg AL, de Andrade M, Matsumoto ME, Tang H, Thibodeau SN, Petersen GM, Wang L. Leukocyte DNA methylation signature differentiates pancreatic cancer patients from healthy controls. PLoS One 2011; 6:e18223; http://dx.doi.org/10.1371/journal.pone.0018223; PMID: 21455317

 PubMed Web of Science ®Google Scholar

Jeffries MA, Dozmorov M, Tang Y, Merrill JT, Wren JD, Sawalha AH. Genome-wide DNA methylation patterns in CD4+ T cells from patients with systemic lupus erythematosus. Epigenetics 2011; 6:593 - 601; http://dx.doi.org/10.4161/epi.6.5.15374; PMID: 21436623

 PubMed Web of Science ®Google Scholar

Etcheverry A, Aubry M, de Tayrac M, Vauleon E, Boniface R, Guenot F, Saikali S, Hamlat A, Riffaud L, Menei P, et al. DNA methylation in glioblastoma: impact on gene expression and clinical outcome. BMC Genomics 2010; 11:701; http://dx.doi.org/10.1186/1471-2164-11-701; PMID: 21156036

 PubMed Web of Science ®Google Scholar

Zawada AM, Rogacev KS, Hummel B, Grün OS, Friedrich A, Rotter B, Winter P, Geisel J, Fliser D, Heine GH. SuperTAG methylation-specific digital karyotyping reveals uremia-induced epigenetic dysregulation of atherosclerosis-related genes. Circ Cardiovasc Genet 2012; 5:611 - 20; http://dx.doi.org/10.1161/CIRCGENETICS.112.963207; PMID: 23074332

 PubMed Web of Science ®Google Scholar

Lübbert M, Tobler A, Daskalakis M. Cytosine demethylation of the proteinase-3/myeloblastin primary granule protease gene during phagocyte development. Leukemia 1999; 13:1420 - 7; http://dx.doi.org/10.1038/sj.leu.2401486; PMID: 10482994

 PubMed Web of Science ®Google Scholar

Zhang Q, Wang HY, Liu X, Wasik MA. STAT5A is epigenetically silenced by the tyrosine kinase NPM1-ALK and acts as a tumor suppressor by reciprocally inhibiting NPM1-ALK expression. Nat Med 2007; 13:1341 - 8; http://dx.doi.org/10.1038/nm1659; PMID: 17922009

 PubMed Web of Science ®Google Scholar

Ressler KJ, Mercer KB, Bradley B, Jovanovic T, Mahan A, Kerley K, et al. Post-traumatic stress disorder is associated with PACAP and the PAC1 receptor. Nature. England, 2011:492-7.

 Google Scholar

Jung S, Yi L, Jeong D, Kim J, An S, Oh TJ, Kim CH, Kim CJ, Yang Y, Kim KI, et al. The role of ADCYAP1, adenylate cyclase activating polypeptide 1, as a methylation biomarker for the early detection of cervical cancer. Oncol Rep 2011; 25:245 - 52; PMID: 21109983

 PubMed Web of Science ®Google Scholar

Matsusaka K, Kaneda A, Nagae G, Ushiku T, Kikuchi Y, Hino R, et al. Classification of Epstein-Barr virus-positive gastric cancers by definition of DNA methylation epigenotypes. Cancer Res. United States, 2011:7187-97.

 Google Scholar

Cogdell D, Chung W, Liu Y, McDonald JM, Aldape K, Issa JP, et al. Tumor-associated methylation of the putative tumor suppressor AJAP1 gene and association between decreased AJAP1 expression and shorter survival in patients with glioma. Chin J Cancer. China, 2011:247-53.

 Google Scholar

Rauch TA, Wang Z, Wu X, Kernstine KH, Riggs AD, Pfeifer GP. DNA methylation biomarkers for lung cancer. Tumour Biol 2012; 33:287 - 96; http://dx.doi.org/10.1007/s13277-011-0282-2; PMID: 22143938

 PubMed Web of Science ®Google Scholar

Kim YH, Lee HC, Kim SY, Yeom YI, Ryu KJ, Min BH, Kim DH, Son HJ, Rhee PL, Kim JJ, et al. Epigenomic analysis of aberrantly methylated genes in colorectal cancer identifies genes commonly affected by epigenetic alterations. Ann Surg Oncol 2011; 18:2338 - 47; http://dx.doi.org/10.1245/s10434-011-1573-y; PMID: 21298349

 PubMed Web of Science ®Google Scholar

Tessema M, Yu YY, Stidley CA, Machida EO, Schuebel KE, Baylin SB, Belinsky SA. Concomitant promoter methylation of multiple genes in lung adenocarcinomas from current, former and never smokers. Carcinogenesis 2009; 30:1132 - 8; http://dx.doi.org/10.1093/carcin/bgp114; PMID: 19435948

 PubMed Web of Science ®Google Scholar

Ramos EA, Camargo AA, Braun K, Slowik R, Cavalli IJ, Ribeiro EM, Pedrosa FdeO, de Souza EM, Costa FF, Klassen G. Simultaneous CXCL12 and ESR1 CpG island hypermethylation correlates with poor prognosis in sporadic breast cancer. BMC Cancer 2010; 10:23; http://dx.doi.org/10.1186/1471-2407-10-23; PMID: 20109227

 PubMed Web of Science ®Google Scholar

Karouzakis E, Rengel Y, Jungel A, Kolling C, Gay RE, Michel BA, et al. DNA methylation regulates the expression of CXCL12 in rheumatoid arthritis synovial fibroblasts. Genes Immun. England, 2011:643-52.

 Google Scholar

Yoshino M, Suzuki M, Tian L, Moriya Y, Hoshino H, Okamoto T, Yoshida S, Shibuya K, Yoshino I. Promoter hypermethylation of the p16 and Wif-1 genes as an independent prognostic marker in stage IA non-small cell lung cancers. Int J Oncol 2009; 35:1201 - 9; PMID: 19787276

 PubMed Web of Science ®Google Scholar

Zhou W, Jiang Z, Song X, Liu Y, Wen P, Guo Y, Xu F, Kong L, Zhang P, Han A, et al. Promoter hypermethylation-mediated down-regulation of CXCL12 in human astrocytoma. J Neurosci Res 2008; 86:3002 - 10; http://dx.doi.org/10.1002/jnr.21746; PMID: 18512766

 PubMed Web of Science ®Google Scholar

Wendt MK, Johanesen PA, Kang-Decker N, Binion DG, Shah V, Dwinell MB. Silencing of epithelial CXCL12 expression by DNA hypermethylation promotes colonic carcinoma metastasis. Oncogene 2006; 25:4986 - 97; http://dx.doi.org/10.1038/sj.onc.1209505; PMID: 16568088

 PubMed Web of Science ®Google Scholar

Sato N, Matsubayashi H, Fukushima N, Goggins M. The chemokine receptor CXCR4 is regulated by DNA methylation in pancreatic cancer. Cancer Biol Ther 2005; 4:70 - 6; http://dx.doi.org/10.4161/cbt.4.1.1378; PMID: 15662133

 PubMed Web of Science ®Google Scholar

Misawa K, Ueda Y, Kanazawa T, Misawa Y, Jang I, Brenner JC, Ogawa T, Takebayashi S, Grenman RA, Herman JG, et al. Epigenetic inactivation of galanin receptor 1 in head and neck cancer. Clin Cancer Res 2008; 14:7604 - 13; http://dx.doi.org/10.1158/1078-0432.CCR-07-4673; PMID: 19047085

 PubMed Web of Science ®Google Scholar

Shen RZ, Pan S, Qi SJ, Lin XL, Cheng SD. Epigenetic repression of microRNA-129-2 leads to overexpression of SOX4 in gastric cancer. Biochem Biophys Res Commun 2010; 394:1047 - 52; http://dx.doi.org/10.1016/j.bbrc.2010.03.121; PMID: 20331975

 PubMed Web of Science ®Google Scholar

Reinert T, Modin C, Castano FM, Lamy P, Wojdacz TK, Hansen LL, Wiuf C, Borre M, Dyrskjøt L, Orntoft TF. Comprehensive genome methylation analysis in bladder cancer: identification and validation of novel methylated genes and application of these as urinary tumor markers. Clin Cancer Res 2011; 17:5582 - 92; http://dx.doi.org/10.1158/1078-0432.CCR-10-2659; PMID: 21788354

 PubMed Web of Science ®Google Scholar

Sugino Y, Misawa A, Inoue J, Kitagawa M, Hosoi H, Sugimoto T, Imoto I, Inazawa J. Epigenetic silencing of prostaglandin E receptor 2 (PTGER2) is associated with progression of neuroblastomas. Oncogene 2007; 26:7401 - 13; http://dx.doi.org/10.1038/sj.onc.1210550; PMID: 17533365

 PubMed Web of Science ®Google Scholar

Isidoro-García M, Sanz C, García-Solaesa V, Pascual M, Pescador DB, Lorente F, Dávila I. PTGDR gene in asthma: a functional, genetic, and epigenetic study. Allergy 2011; 66:1553 - 62; http://dx.doi.org/10.1111/j.1398-9995.2011.02685.x; PMID: 21883277

 PubMed Web of Science ®Google Scholar

Yi JM, Dhir M, Guzzetta AA, Iacobuzio-Donahue CA, Heo K, Yang KM, Suzuki H, Toyota M, Kim HM, Ahuja N. DNA methylation biomarker candidates for early detection of colon cancer. Tumour Biol 2012; 33:363 - 72; http://dx.doi.org/10.1007/s13277-011-0302-2; PMID: 22238052

 PubMed Web of Science ®Google Scholar

Koch CM, Wagner W. Epigenetic-aging-signature to determine age in different tissues. Aging (Albany NY) 2011; 3:1018 - 27; PMID: 22067257

 PubMedGoogle Scholar

Tao R, Li J, Xin J, Wu J, Guo J, Zhang L, Jiang L, Zhang W, Yang Z, Li L. Methylation profile of single hepatocytes derived from hepatitis B virus-related hepatocellular carcinoma. PLoS One 2011; 6:e19862; http://dx.doi.org/10.1371/journal.pone.0019862; PMID: 21625442

 PubMedGoogle Scholar

Arai E, Chiku S, Mori T, Gotoh M, Nakagawa T, Fujimoto H, Kanai Y. Single-CpG-resolution methylome analysis identifies clinicopathologically aggressive CpG island methylator phenotype clear cell renal cell carcinomas. Carcinogenesis 2012; 33:1487 - 93; http://dx.doi.org/10.1093/carcin/bgs177; PMID: 22610075

 PubMed Web of Science ®Google Scholar

Oka D, Yamashita S, Tomioka T, Nakanishi Y, Kato H, Kaminishi M, Ushijima T. The presence of aberrant DNA methylation in noncancerous esophageal mucosae in association with smoking history: a target for risk diagnosis and prevention of esophageal cancers. Cancer 2009; 115:3412 - 26; http://dx.doi.org/10.1002/cncr.24394; PMID: 19472401

 PubMed Web of Science ®Google Scholar

Huang RL, Chang CC, Su PH, Chen YC, Liao YP, Wang HC, Yo YT, Chao TK, Huang HC, Lin CY, et al. Methylomic analysis identifies frequent DNA methylation of zinc finger protein 582 (ZNF582) in cervical neoplasms. PLoS One 2012; 7:e41060; http://dx.doi.org/10.1371/journal.pone.0041060; PMID: 22815913

 PubMed Web of Science ®Google Scholar

Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics. CA Cancer J Clin 2011; 61:69 - 90; http://dx.doi.org/10.3322/caac.20107; PMID: 21296855

 PubMed Web of Science ®Google Scholar

Oster B, Thorsen K, Lamy P, Wojdacz TK, Hansen LL, Birkenkamp-Demtröder K, Sørensen KD, Laurberg S, Orntoft TF, Andersen CL. Identification and validation of highly frequent CpG island hypermethylation in colorectal adenomas and carcinomas. Int J Cancer 2011; 129:2855 - 66; http://dx.doi.org/10.1002/ijc.25951; PMID: 21400501

 PubMed Web of Science ®Google Scholar

Morris MR, Ricketts CJ, Gentle D, McRonald F, Carli N, Khalili H, Brown M, Kishida T, Yao M, Banks RE, et al. Genome-wide methylation analysis identifies epigenetically inactivated candidate tumour suppressor genes in renal cell carcinoma. Oncogene 2011; 30:1390 - 401; http://dx.doi.org/10.1038/onc.2010.525; PMID: 21132003

 PubMed Web of Science ®Google Scholar