Circulating cell-free methylated DNA and lactate dehydrogenase release in colorectal cancer
© Philipp et al.; licensee BioMed Central Ltd. 2014
Received: 30 September 2013
Accepted: 3 April 2014
Published: 8 April 2014
Hypermethylation of DNA is an epigenetic alteration commonly found in colorectal cancer (CRC) and can also be detected in blood samples of cancer patients. Methylation of the genes helicase-like transcription factor (HLTF) and hyperplastic polyposis 1 (HPP1) have been proposed as prognostic, and neurogenin 1 (NEUROG1) as diagnostic biomarker. However the underlying mechanisms leading to the release of these genes are unclear. This study aimed at examining the possible correlation of the presence of methylated genes NEUROG1, HLTF and HPP1 in serum with tissue breakdown as a possible mechanism using serum lactate dehydrogenase (LDH) as a surrogate marker. Additionally the prognostic impact of these markers was examined.
Pretherapeutic serum samples from 259 patients from all cancer stages were analyzed. Presence of hypermethylation of the genes HLTF, HPP1, and NEUROG1 was examined using methylation-specific quantitative PCR (MethyLight). LDH was determined using an UV kinetic test.
Hypermethylation of HLTF and HPP1 was detected significantly more often in patients with elevated LDH levels (32% vs. 12% [p = 0.0005], and 68% vs. 11% [p < 0.0001], respectively). Also, higher LDH values correlated with a higher percentage of a fully methylated reference in a linear fashion (Spearman correlation coefficient 0.18 for HLTF [p = 0.004]; 0.49 [p < .0001] for HPP1). No correlation between methylation of NEUROG1 and LDH was found in this study. Concerning the clinical characteristics, high levels of LDH as well as methylation of HLTF and HPP1 were significantly associated with larger and more advanced stages of CRC. Accordingly, these three markers were correlated with significantly shorter survival in the overall population. Moreover, all three identified patients with a worse prognosis in the subgroup of stage IV patients.
We were able to provide evidence that methylation of HLTF and especially HPP1 detected in serum is strongly correlated with cell death in CRC using LDH as surrogate marker. Additionally, we found that prognostic information is given by both HLTF and HPP1 as well as LDH. In sum, determining the methylation of HLTF and HPP1 in serum might be useful in order to identify patients with more aggressive tumors.
KeywordsColorectal cancer Dna methylation Hltf Hpp1 Neurog1 Ldh
Colorectal cancer (CRC) is the third most common cancer and the fourth most frequent cause of death from cancer worldwide with about 1.2 million cases and about 633,000 deaths in 2008 . Despite significant advances in the last decades, especially patients with metastatic disease suffer from poor prognosis . In addition to new therapeutic options, biomarkers are needed that allow the identification of different subgroups of patients potentially benefitting from different treatment regimens and intensity.
In many human cancers aberrant hypermethylation of CpG islands is a common epigenetic DNA modification leading to transcriptional silencing of genes that is already detectable in early stages of carcinogenesis . Genes found hypermethylated in colorectal cancer have many functions, including mismatch repair, cell-cycle regulation and cell differentiation . Methylated tumor DNA cannot only be found in primary colorectal cancer tissue, but can also be detected in remote media like serum or stool and potentially be used as biomarkers for various purposes [5–7]. We have previously described methylation of the genes neurogenin 1 (NEUROG1) in serum and HIC1 in stool as diagnostic markers [8, 9] and helicase-like transcription factor (HLTF) and hyperplastic polyposis 1 (HPP1), also known as transmembrane protein with EGF-like and two follistatin-like domains 2 (TMEFF2), as prognostic serum markers [10, 11].
NEUROG1 is a basic helix-loop-helix transcription factor which has been identified as one of the main players in neurosensory evolution and development, especially of the inner ear . Moreover NEUROG1 has been described to be frequently hypermethylated in colorectal cancers and has been proposed as a marker to classify the CpG-island methylator phenotype in colorectal cancers [13, 14].
HLTF is a transcription factor and a member of the SWI/SNF family of chromatin-remodeling factors . The physiological function of HLTF has not yet been fully understood, but evidence for its association with genesis and progression of cancer exists . Recently HLTF deficiency has been reported to significantly increase the formation of small intestinal adenocarcinoma and colon cancer in mice on a Apc min/+ mutant background and to be associated with chromosomal instability . Hypermethylation of HLTF can commonly be found in all stages of CRC as well as in adenomas and is associated with tumor size, stage and poor prognosis [17–20]. Besides its occurrence in serum, methylated HLTF has also been detected in stool samples of CRC patients [21, 22].
HPP1 encodes a transmembrane protein containing epidermal growth factor and follistatin domains. While reported to function as a tumor suppressor related to the STAT1 pathway earlier , a recently published study failed to identify tumors in HPP1 mutant mice . Hypermethylation of HPP1 can be detected already early in colorectal carcinogenesis [25–27]. Hyperplastic polyps and ulcerative colitis associated dysplasias as well as a several other tumor entities, including Barrett’s-associated esophageal adenocarcinoma, gastric adenocarcinoma, bladder cancer, non-small cell lung cancer and others, frequently showed HPP1 methylation [26–32].
Lactate dehydrogenase (LDH) is essential for anaerobic glycolysis and reversably converts pyruvate to lactate. Its expression has been shown to be related to the hypoxia inducible factor HIF-1 [33–36]. Activation of the HIF pathway is a common finding in cancers [37, 38]. LDH in serum is a frequently used parameter in clinical routine and is released upon cell membrane disintegration. Thus, it is an unspecific marker for tissue damage, e.g. caused by necrosis. Elevated LDH levels can be found in numerous diseases including myocardial infarction, hemolysis and malignancies . Additionally LDH has been reported to be associated with more aggressive tumors and shorter survival [40–43] in CRC. In other cancer entities like testicular cancer [44, 45] and aggressive non-hodgkin lymphoma  elevated LDH levels are used as prognostic biomarkers. Recently, LDH has been discussed as a predictive biomarker for anti-angiogenic therapies in colorectal cancer [43, 47, 48].
Cell death, especially necrosis, is considered to be the source of circulating cell-free DNA (cfDNA) in cancer patients [49, 50]. However, the exact mechanisms leading to the release of the tumor markers discussed here with prognostic (HLTF and HPP1) or diagnostic (NEUROG1) information have not been examined so far. This study aimed at investigating a possible correlation of the presence of the methylated genes NEUROG1, HLTF and HPP1 in serum with tissue breakdown as a possible release mechanism using serum lactate dehydrogenase (LDH) as a surrogate marker. Additionally, the prognostic information given by these markers was examined.
Patients and serum samples
Clinical features of the patient population
Number of patients (%)
Number of patients (%)
Total number of patients 259
≤ 65 years
> 65 years
Tumor grade d
G1 & G2
G3 & G4
Tumor size b
Nodal status c
DNA isolation and bisulfite conversion
The frozen serum samples were thawed at room temperature and homogenized by smoothly flipping the tube containing the serum. Genomic DNA from 200 μL of each serum sample was isolated using the High Pure Viral Nucleic Acid Kit (Roche Applied Science, Mannheim, Germany) according to the manufacturer’s instructions and eluted in 50 μl of Elution Buffer. Bisulfite conversion was performed as described previously .
Analysis of DNA methylation
Bisulfite-treated DNA was analyzed by a fluorescence-based, real-time PCR assay, described previously as MethyLight . Dispersed Alu repeats were used to control for DNA amplification and to normalize for input DNA. Primer and probe sequences are listed in Additional file 1: Table S1. PCRs were done in 20 μL volumes containing 1x PCR buffer (Qiagen, Hilden, Germany), 4 mmol/L MgCl2, 250 μmol/L deoxynucleotide triphosphate mixture, 4 μL bisulfite-treated DNA, 0.05 units/μL Taq DNA polymerase (HotStar Taq, Qiagen) along with a pair of primers and probes according to Additional file 1: Table S1. PCRs were conducted in a Mastercycler® ep realplex4 (Eppendorf, Hamburg, Germany) using the following conditions: 95°C for 900 s followed by 50 cycles of 95°C for 30 s, 60°C for 120 s, and 84°C for 20 s. The specificity of all reactions for methylated DNA was confirmed by separately amplifying completely methylated and unmethylated human control DNA (Chemicon, Temecula, CA) with each set of primers and probes. The percentage of fully methylated reference (PMR) at a specific locus was calculated as described previously  by dividing the gene/Alu ratio of a sample by the gene/Alu ratio of fully methylated, bisulfite-treated DNA (CpGenome™ Universal Methylated DNA, Millipore, Billerica, MA) and multiplying by 100. A gene was considered methylated if the percentage of the fully methylated reference value was > 0.
Determination of LDH
LDH values were determined by a UV kinetic test using the Beckman Coulter AU 2700 analyser (Beckman Coulter GmbH, Krefeld, Germany) by the central laboratory of the university hospital of Munich. The upper limit of normal for this assay applied in everyday clinical routine is 250 U/l in our hospital. LDH levels above this value were defined as elevated in this study.
All statistical analysis was done using SAS 9.3 (SAS Institute Inc., Cary, NC). Pearson’s χ2 test was used to explore associations between clinicopathologic features and categorized variables. Associations between categorized and continuous variables were tested by means of the Wilcoxon-Mann–Whitney test and correlations between continuous variables were examined using Spearman Correlation Coefficients. For evaluation of simultaneous influence of clinicopathologic features and methylation markers on LDH values a multivariate logistic regression model was developed. Overall survival was calculated from the date of diagnosis of the primary tumor to the date of death or end of follow-up. Univariate analysis of overall survival according to gene methylation status and LDH values was performed using the Kaplan–Meier method and log-rank tests.
Clinicopathologic features and DNA methylation in serum
Distribution of LDH and methylation of HLTF , HPP1 and NEUROG1 among clinicopathologic features
LDH ≥ 250 U/l
≤ 65 years
> 65 years
Tumor size a
Nodal status b
Tumor grade c
G1 & G2
G3 & G4
LDH values ranged from 100 to 1730 U/l with a mean value of 238 U/l (standard deviation 202 U/l) and a median value of 185 U/l. A cutoff of 250 U/l, representing the upper limit of normal of the assay used, was chosen, resulting in 50 patients (19%) with elevated LDH levels. These patients suffered more frequently from T4 tumors (T1-3 vs. T4, p = 0.038), nodal and distant metastases (p = 0.0006 and p < 0.0001, respectively) as well as higher tumor stages (p < 0.0001). Additionally, a non-significant trend towards higher LDH levels in younger patients was found (p = 0.055).
Correlation between LDH and DNA methylation in serum
First we analyzed the correlation of methylation of HLTF, HPP1 and NEUROG1 with LDH in a binary way. For this purpose we used a cutoff of LDH at 250 U/l as mentioned above. For the methylation markers we considered a PMR > 0 as methylation positive which has been shown previously to be reasonable for serum methylation analysis by our and other groups [10, 52, 53]. In the 50 samples with elevated LDH levels, methylation of HLTF, HPP1, or NEUROG1 was detected in 16 (32%), 34 (68%), or 12 cases (24%), respectively, compared to 25 (12%), 23 (11%), or 54 (26%) in those 209 samples with normal LDH levels. Patients with elevated LDH levels revealed significantly more often methylation of HLTF or HPP1 (p = 0.0005 or p < 0.0001, respectively), whereas no correlation between NEUROG1 methylation and elevated LDH was found.
We also examined the relation of the methylation markers between each other. Methylation of HLTF was found significantly more often in HPP1 positive samples (51% vs. 17%, p < 0.0001). No significant difference in the frequency of either HLTF or HPP1 methylation was observed between NEUROG1 positive and NEUROG1 negative cases (32% vs. 24% and 26% vs. 25%, respectively).
Linear Spearman correlation coefficients for the percentage of fully methylated reference (PMR) of HLTF , HPP1 and NEUROG1, and LDH levels among each other
0.32 (p < .0001)
0.05 (p = 0.41)
−0.00 (p = 0.97)
0.18 (p = 0.004)
0.49 (p < .0001)
0.01 (p = 0.85)
Next, a multivariate model was developed using logistic regression analysis with LDH values higher than 250 U/l as target variable. HPP1 and HLTF methylation as binary parameters, i.e. with a PMR > 0, as well as clinicopathological features were entered as independent variables. Only presence of distant metastases and HPP1 correlated significantly and independently with elevated LDH levels higher than 250 U/l. The odds ratios were 3.1 for metastatic disease (95% CI 1.3-7.2, p = 0.009) and 9.5 for HPP1 methylation (95% CI 4.2-21.9, p < 0.0001).
We earlier reported methylation of HLTF and HPP1 to be independent prognostic markers in metastastatic colorectal cancer . On the other hand, elevated LDH levels have been described to be linked to shorter survival . Thus we compared methylation of HLTF and HPP1 with LDH as prognostic factors in our patient population.
Next, we evaluated the prognostic significance stratified by tumor stage. For patients with UICC stage I-III no significant difference in overall survival, neither for LDH (p = 0.41) nor for HLTF and HPP1 (p = 0.41 and p = 0.08, respectively), was found. However, in stage IV HLTF methylation positive patients showed a median survival of 0.86 years (95% CI 0.5-1.2) versus 1.6 years (95% CI 1.2-2.3) for HLTF negative cases (p = 0.0081; Figure 2D). For HPP1 positive and negative cases the median survival was 1.0 years (95% CI 0.6-1.4) and 1.8 years (95% CI 1.2-3.3), respectively (p = 0.0005; Figure 2E). For LDH, elevated levels > 250 U/l were associated with shorter median survival (1.0 years, 95% CI 0.6-1.2, vs. 1.8 years, 95% CI 1.3-2.5; p = 0.0002; Figure 2F).
In this study we examined the correlation between cell damage using LDH as a surrogate marker and the methylation status of three genes which have previously been proposed as prognostic (HLTF, HPP1) [10, 11] or diagnostic (NEUROG1)  biomarkers for patients with CRC.
Our data confirm our previous findings that methylation of HLTF or HPP1 in serum is found more often in patients with advanced stages of colorectal cancer, especially in those with distant metastases, whereas no correlation between methylation of NEUROG1 and any clinicopathologic data was found. While methylation of HLTF was only correlated with metastastatic disease, methylation of HPP1 was also associated with local tumor extent and nodal status as well as tumor grade with high statistic significance.
It is well known that patients with elevated serum levels of LDH tend to have more aggressive tumors and a shorter survival time [40–43]. Consistent with the literature high LDH levels in our data were significantly correlated with advanced tumor stages as well as nodal and distant metastases. Trends towards larger tumor size and younger age were observed but did not reach statistical significance.
Cell death associated mechanisms like apoptosis or, especially in cancer, necrosis have been suggested as main sources for cell-free DNA (cfDNA) in the blood, but other mechanisms like physiological active release have been described as well (for reviews see refs. [49, 50]). In this study we found methylation of HLTF and, even to a higher degree, HPP1 to be correlated with elevated LDH levels. This finding was robust, as it was confirmed by different statistical methods. Given that elevated LDH indicates cell membrane damage, this observation might be a hint that methylated HLTF and HPP1 DNA is released by tumor cells undergoing cell death. The fact that necrosis tends to be found more often in larger, more aggressive tumours and advanced cancer stages [55, 56], which was likewise the case for LDH as well as methylated HLTF and HPP1 in our data, also suggests an interrelation.
For NEUROG1, on the other hand, hypermethylation in serum was detectable independently of LDH levels and tumor stage. This is consistent with earlier analyses revealing methylation of NEUROG1 in primary tissue not to be associated with tumor stage (A.P. and F.K., data not published). Hence the observed correlation between DNA methylation in serum and LDH seems not to be linked to global methylation levels and cell death alone. Besides the methylation status of distinct genes, other parameters influencing this observation might include DNA integrity and stability of the respective segments as well as still unknown factors. Therefore it seems likely that tumor cell death might not be the only mechanism by which methylated tumor DNA is released to the blood.
In addition to the correlation analysis we examined the prognostic significance of the methylation markers HPP1 and HLTF as well as of LDH. All three markers were significantly associated with worse overall survival. This could be attributed to the fact that all three markers are found more frequently in advanced cancer stages. However, earlier analyses  as well as the survival data presented here furthermore divide patients with already metastasized disease into two subgroups with better or worse prognosis, respectively.
In conclusion we were able to provide evidence that methylation of HLTF and especially HPP1 detected in serum is strongly correlated with cell death in colorectal cancer using LDH as surrogate marker. However, this finding was specific for those two genes and did not occur for NEUROG1, suggesting that mechanisms other than release by membrane disintegration could be responsible for the occurrence of cell-free DNA in blood of CRC patients. Additionally, we found that prognostic information is given by both HLTF and HPP1 as well as LDH. In sum, determining the methylation of HLTF and HPP1 in serum might be useful in order to identify patients with more aggressive tumors. Future research needs to further clarify the underlying biological mechanisms and to validate methylated cell-free circulating DNA as a biomarker for colorectal cancer.
Cell-free deoxyribonucleic acid
CpG island methylator phenotype
Hypoxia inducible factor
Helicase-like transcription factor
Polymerase chain reaction
Percentage of fully methylated reference
Union for international cancer control
Medical Faculty of the University of Munich.
- Ferlay J, Shin HR, Bray F, Forman D, Mathers C, Parkin DM: Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. Int J Cancer. 2010, 127: 2893-2917. 10.1002/ijc.25516.View ArticlePubMedGoogle Scholar
- O’Connell JB, Maggard MA, Ko CY: Colon cancer survival rates with the new American Joint Committee on Cancer sixth edition staging. J Natl Cancer Inst. 2004, 96: 1420-1425. 10.1093/jnci/djh275.View ArticlePubMedGoogle Scholar
- Jones PA, Baylin SB: The epigenomics of cancer. Cell. 2007, 128: 683-692. 10.1016/j.cell.2007.01.029.View ArticlePubMedPubMed CentralGoogle Scholar
- Baylin SB, Ohm JE: Epigenetic gene silencing in cancer - a mechanism for early oncogenic pathway addiction?. Nat Rev Cancer. 2006, 6: 107-116. 10.1038/nrc1799.View ArticlePubMedGoogle Scholar
- Duffy MJ, Napieralski R, Martens JWM, Span PN, Spyratos F, Sweep FCGJ, Brunner N, Foekens JA, Schmitt M: Methylated genes as new cancer biomarkers. Eur J Cancer. 2009, 45: 335-346. 10.1016/j.ejca.2008.12.008.View ArticlePubMedGoogle Scholar
- Kim MS, Lee J, Sidransky D: DNA methylation markers in colorectal cancer. Cancer Metastasis Rev. 2010, 29: 181-206. 10.1007/s10555-010-9207-6.View ArticlePubMedGoogle Scholar
- Herbst A, Kolligs FT: Detection of DNA hypermethylation in remote media of patients with colorectal cancer: new biomarkers for colorectal carcinoma. Tumour Biol. 2012, 33: 297-305. 10.1007/s13277-012-0346-y.View ArticlePubMedGoogle Scholar
- Herbst A, Rahmig K, Stieber P, Philipp A, Jung A, Ofner A, Crispin A, Neumann J, Lamerz R, Kolligs FT: Methylation of NEUROG1 in Serum Is a Sensitive Marker for the Detection of Early Colorectal Cancer. Am J Gastroenterol. 2011, 106: 1110-1118. 10.1038/ajg.2011.6.View ArticlePubMedGoogle Scholar
- Lenhard K, Bommer GT, Asutay S, Schauer R, Brabletz T, Göke B, Lamerz R, Kolligs FT: Analysis of promoter methylation in stool: a novel method for the detection of colorectal cancer. Clin Gastroenterol Hepatol. 2005, 3: 142-149. 10.1016/S1542-3565(04)00624-X.View ArticlePubMedGoogle Scholar
- Wallner M, Herbst A, Behrens A, Crispin A, Stieber P, Göke B, Lamerz R, Kolligs FT: Methylation of serum DNA is an independent prognostic marker in colorectal cancer. Clin Cancer Res. 2006, 12: 7347-7352. 10.1158/1078-0432.CCR-06-1264.View ArticlePubMedGoogle Scholar
- Philipp AB, Stieber P, Nagel D, Neumann J, Spelsberg F, Jung A, Lamerz R, Herbst A, Kolligs FT: Prognostic role of methylated free circulating DNA in colorectal cancer. Int J Cancer. 2012, 131: 2308-2319. 10.1002/ijc.27505.View ArticlePubMedGoogle Scholar
- Pan N, Kopecky B, Jahan I, Fritzsch B: Understanding the evolution and development of neurosensory transcription factors of the ear to enhance therapeutic translation. Cell Tissue Res. 2012, 349: 415-432. 10.1007/s00441-012-1454-0.View ArticlePubMedPubMed CentralGoogle Scholar
- Weisenberger DJ, Siegmund KD, Campan M, Young J, Long TI, Faasse MA, Kang GH, Widschwendter M, Weener D, Buchanan D, Koh H, Simms L, Barker M, Leggett B, Levine J, Kim M, French AJ, Thibodeau SN, Jass J, Haile R, Laird PW: CpG island methylator phenotype underlies sporadic microsatellite instability and is tightly associated with BRAF mutation in colorectal cancer. Nat Genet. 2006, 38: 787-793. 10.1038/ng1834.View ArticlePubMedGoogle Scholar
- Ogino S, Cantor M, Kawasaki T, Brahmandam M, Kirkner GJ, Weisenberger DJ, Campan M, Laird PW, Loda M, Fuchs CS: CpG island methylator phenotype (CIMP) of colorectal cancer is best characterised by quantitative DNA methylation analysis and prospective cohort studies. Gut. 2006, 55: 1000-1006. 10.1136/gut.2005.082933.View ArticlePubMedPubMed CentralGoogle Scholar
- Sandhu S, Wu X, Nabi Z, Rastegar M, Kung S, Mai S, Ding H: Loss of HLTF function promotes intestinal carcinogenesis. Mol Cancer. 2012, 11: 18-10.1186/1476-4598-11-18.View ArticlePubMedPubMed CentralGoogle Scholar
- Debauve G, Capouillez A, Belayew A, Saussez S: The helicase-like transcription factor and its implication in cancer progression. Cell Mol Life Sci. 2008, 65: 591-604. 10.1007/s00018-007-7392-4.View ArticlePubMedGoogle Scholar
- Moinova HR, Chen W-D, Shen L, Smiraglia D, Olechnowicz J, Ravi L, Kasturi L, Myeroff L, Plass C, Parsons R, Minna J, Willson JKV, Green SB, Issa J-P, Markowitz SD: HLTF gene silencing in human colon cancer. Proc Natl Acad Sci U S A. 2002, 99: 4562-4567. 10.1073/pnas.062459899.View ArticlePubMedPubMed CentralGoogle Scholar
- Bai AHC, Tong JHM, To K-F, Chan MWY, Man EPS, Lo K-W, Lee JFY, Sung JJY, Leung WK: Promoter hypermethylation of tumor-related genes in the progression of colorectal neoplasia. Int J Cancer. 2004, 112: 846-853. 10.1002/ijc.20485.View ArticlePubMedGoogle Scholar
- Hibi K, Nakao A: Highly-methylated colorectal cancers show poorly-differentiated phenotype. Anticancer Res. 2006, 26: 4263-4266.PubMedGoogle Scholar
- Kim Y, Petko Z, Dzieciatkowski S, Lin L, Ghiassi M, Stain S, Chapman WC, Washington MK, Willis J, Markowitz SD, Grady WM: CpG island methylation of genes accumulates during the adenoma progression step of the multistep pathogenesis of colorectal cancer. Genes Chromosomes Cancer. 2006, 45: 781-789. 10.1002/gcc.20341.View ArticlePubMedGoogle Scholar
- Leung WK, To K-F, Man EPS, Chan MWY, Bai AHC, Hui AJ, Chan FKL, Lee JFY, Sung JJY: Detection of epigenetic changes in fecal DNA as a molecular screening test for colorectal cancer: a feasibility study. Clin Chem. 2004, 50: 2179-2182. 10.1373/clinchem.2004.039305.View ArticlePubMedGoogle Scholar
- Leung WK, To K-F, Man EPS, Chan MWY, Hui AJ, Ng SSM, Lau JYW, Sung JJY: Detection of hypermethylated DNA or cyclooxygenase-2 messenger RNA in fecal samples of patients with colorectal cancer or polyps. Am J Gastroenterol. 2007, 102: 1070-1076. 10.1111/j.1572-0241.2007.01108.x.View ArticlePubMedGoogle Scholar
- Elahi A, Zhang L, Yeatman TJ, Gery S, Sebti S, Shibata D: HPP1-mediated tumor suppression requires activation of STAT1 pathways. Int J Cancer. 2008, 122: 1567-1572.View ArticlePubMedGoogle Scholar
- Chen TR, Wang P, Carroll LK, Zhang Y, Han B-X, Wang F: Generation and characterization of Tmeff2 mutant mice. Biochem Biophys Res Commun. 2012, 425: 189-194. 10.1016/j.bbrc.2012.07.064.View ArticlePubMedPubMed CentralGoogle Scholar
- Ebert MP, Mooney SH, Tonnes-Priddy L, Lograsso J, Hoffmann J, Chen J, Röcken C, Schulz H-U, Malfertheiner P, Lofton-Day C: Hypermethylation of the TPEF/HPP1 Gene in Primary and Metastatic Colorectal Cancers. Neoplasia. 2005, 7: 771-778. 10.1593/neo.05235.View ArticlePubMedPubMed CentralGoogle Scholar
- Young J, Biden KG, Simms LA, Huggard P, Karamatic R, Eyre HJ, Sutherland GR, Herath N, Barker M, Anderson GJ, Fitzpatrick DR, Ramm GA, Jass JR, Leggett BA: HPP1: a transmembrane protein-encoding gene commonly methylated in colorectal polyps and cancers. Proc Natl Acad Sci U S A. 2001, 98: 265-270. 10.1073/pnas.98.1.265.View ArticlePubMedGoogle Scholar
- Sato F, Shibata D, Harpaz N, Xu Y, Yin J, Mori Y, Wang S, Olaru A, Deacu E, Selaru FM, Kimos MC, Hytiroglou P, Young J, Leggett B, Gazdar AF, Toyooka S, Abraham JM, Meltzer SJ: Aberrant methylation of the HPP1 gene in ulcerative colitis-associated colorectal carcinoma. Cancer Res. 2002, 62: 6820-6822.PubMedGoogle Scholar
- Saito S, Kato J, Hiraoka S, Horii J, Suzuki H, Higashi R, Kaji E, Kondo Y, Yamamoto K: DNA methylation of colon mucosa in ulcerative colitis patients: Correlation with inflammatory status. Inflamm Bowel Dis. 2011, 17: 1955-1965. 10.1002/ibd.21573.View ArticlePubMedGoogle Scholar
- Eads CA, Lord RV, Kurumboor SK, Wickramasinghe K, Skinner ML, Long TI, Peters JH, DeMeester TR, Danenberg KD, Danenberg PV, Laird PW, Skinner KA: Fields of aberrant CpG island hypermethylation in Barrett’s esophagus and associated adenocarcinoma. Cancer Res. 2000, 60: 5021-5026.PubMedGoogle Scholar
- Ivanauskas A, Hoffmann J, Jonaitis LV, Markelis R, Juozaityte E, Kupcinskas L, Lofton-Day C, Röcken C, Malfertheiner P: Distinct TPEF/HPP1 gene methylation patterns in gastric cancer indicate a field effect in gastric carcinogenesis. Dig Liver Dis. 2008, 40: 920-926. 10.1016/j.dld.2008.05.004.View ArticlePubMedGoogle Scholar
- Hellwinkel OJC, Kedia M, Isbarn H, Budäus L, Friedrich MG: Methylation of the TPEF- and PAX6-promoters is increased in early bladder cancer and in normal mucosa adjacent to pTa tumours. BJU Int. 2008, 101: 753-757. 10.1111/j.1464-410X.2007.07322.x.View ArticlePubMedGoogle Scholar
- Lee SM, Park JY, Kim DS: Methylation of TMEFF2 gene in tissue and serum DNA from patients with non-small cell lung cancer. Mol Cells. 2012, 34: 171-176. 10.1007/s10059-012-0083-5.View ArticlePubMedPubMed CentralGoogle Scholar
- Semenza GL, Roth PH, Fang HM, Wang GL: Transcriptional regulation of genes encoding glycolytic enzymes by hypoxia-inducible factor 1. J Biol Chem. 1994, 269: 23757-23763.PubMedGoogle Scholar
- Firth JD, Ebert BL, Pugh CW, Ratcliffe PJ: Oxygen-regulated control elements in the phosphoglycerate kinase 1 and lactate dehydrogenase A genes: similarities with the erythropoietin 3’ enhancer. Proc Natl Acad Sci U S A. 1994, 91: 6496-6500. 10.1073/pnas.91.14.6496.View ArticlePubMedPubMed CentralGoogle Scholar
- Firth JD, Ebert BL, Ratcliffe PJ: Hypoxic regulation of lactate dehydrogenase A. Interaction between hypoxia-inducible factor 1 and cAMP response elements. J Biol Chem. 1995, 270: 21021-21027. 10.1074/jbc.270.36.21021.View ArticlePubMedGoogle Scholar
- Weidemann A, Johnson RS: Biology of HIF-1alpha. Cell Death Differ. 2008, 15: 621-627. 10.1038/cdd.2008.12.View ArticlePubMedGoogle Scholar
- Maxwell PH, Pugh CW, Ratcliffe PJ: Activation of the HIF pathway in cancer. Curr Opin Genet Dev. 2001, 11: 293-299. 10.1016/S0959-437X(00)00193-3.View ArticlePubMedGoogle Scholar
- Keith B, Johnson RS, Simon MC: HIF1α and HIF2α: sibling rivalry in hypoxic tumour growth and progression. Nat Rev Cancer. 2012, 12: 9-22.Google Scholar
- Huijgen HJ, Sanders GT, Koster RW, Vreeken J, Bossuyt PM: The clinical value of lactate dehydrogenase in serum: a quantitative review. Eur J Clin Chem Clin Biochem. 1997, 35: 569-579.PubMedGoogle Scholar
- Mekenkamp LJM, Koopman M, Teerenstra S, van Krieken JHJM, Mol L, Nagtegaal ID, Punt CJA: Clinicopathological features and outcome in advanced colorectal cancer patients with synchronous vs metachronous metastases. Br J Cancer. 2010, 103: 159-164. 10.1038/sj.bjc.6605737.View ArticlePubMedPubMed CentralGoogle Scholar
- De Gramont A, Figer A, Seymour M, Homerin M, Hmissi A, Cassidy J, Boni C, Cortes-Funes H, Cervantes A, Freyer G, Papamichael D, Le Bail N, Louvet C, Hendler D, de Braud F, Wilson C, Morvan F, Bonetti A: Leucovorin and fluorouracil with or without oxaliplatin as first-line treatment in advanced colorectal cancer. J Clin Oncol. 2000, 18: 2938-2947.PubMedGoogle Scholar
- Wu X, Ma F, Wang X-L: Serological diagnostic factors for liver metastasis in patients with colorectal cancer. World J Gastroenterol. 2010, 16: 4084-4088. 10.3748/wjg.v16.i32.4084.View ArticlePubMedPubMed CentralGoogle Scholar
- Scartozzi M, Giampieri R, Maccaroni E, Del Prete M, Faloppi L, Bianconi M, Galizia E, Loretelli C, Belvederesi L, Bittoni A, Cascinu S: Pre-treatment lactate dehydrogenase levels as predictor of efficacy of first-line bevacizumab-based therapy in metastatic colorectal cancer patients. Br J Cancer. 2012, 106: 799-804. 10.1038/bjc.2012.17.View ArticlePubMedPubMed CentralGoogle Scholar
- International Germ Cell Cancer Collaborative Group: Germ Cell Consensus Classification: a prognostic factor-based staging system for metastatic germ cell cancers. International Germ Cell Cancer Collaborative Group. J Clin Oncol. 1997, 15: 594-603.Google Scholar
- Krege S, Beyer J, Souchon R, Albers P, Albrecht W, Algaba F, Bamberg M, Bodrogi I, Bokemeyer C, Cavallin-Ståhl E, Classen J, Clemm C, Cohn-Cedermark G, Culine S, Daugaard G, De Mulder PHM, De Santis M, de Wit M, de Wit R, Derigs HG, Dieckmann K, Dieing A, Droz J, Fenner M, Fizazi K, Flechon A, Fosså SD, del Muro XG, Gauler T, Geczi L, et al: European consensus conference on diagnosis and treatment of germ cell cancer: a report of the second meeting of the European Germ Cell Cancer Consensus group (EGCCCG): part I. Eur Urol. 2008, 53: 478-496. 10.1016/j.eururo.2007.12.024.View ArticlePubMedGoogle Scholar
- A predictive model for aggressive non-Hodgkin’s lymphoma. The International Non-Hodgkin's Lymphoma Prognostic Factors Project. N Engl J Med. 1993, 329: 987-994.
- Hecht JR, Trarbach T, Hainsworth JD, Major P, Jäger E, Wolff RA, Lloyd-Salvant K, Bodoky G, Pendergrass K, Berg W, Chen B-L, Jalava T, Meinhardt G, Laurent D, Lebwohl D, Kerr D: Randomized, placebo-controlled, phase III study of first-line oxaliplatin-based chemotherapy plus PTK787/ZK 222584, an oral vascular endothelial growth factor receptor inhibitor, in patients with metastatic colorectal adenocarcinoma. J Clin Oncol. 2011, 29: 1997-2003. 10.1200/JCO.2010.29.4496.View ArticlePubMedGoogle Scholar
- Van Cutsem E, Bajetta E, Valle J, Köhne C-H, Randolph Hecht J, Moore M, Germond C, Berg W, Chen B-L, Jalava T, Lebwohl D, Meinhardt G, Laurent D, Lin E: Randomized, placebo-controlled, phase III study of oxaliplatin, fluorouracil, and leucovorin with or without PTK787/ZK 222584 in patients with previously treated metastatic colorectal adenocarcinoma. J Clin Oncol. 2011, 29: 2004-2010. 10.1200/JCO.2010.29.5436.View ArticlePubMedGoogle Scholar
- Jung K, Fleischhacker M, Rabien A: Cell-free DNA in the blood as a solid tumor biomarker–a critical appraisal of the literature. Clin Chim Acta. 2010, 411: 1611-1624. 10.1016/j.cca.2010.07.032.View ArticlePubMedGoogle Scholar
- Schwarzenbach H, Hoon DSB, Pantel K: Cell-free nucleic acids as biomarkers in cancer patients. Nat Rev Cancer. 2011, 11: 426-437. 10.1038/nrc3066.View ArticlePubMedGoogle Scholar
- Eads CA, Danenberg KD, Kawakami K, Saltz LB, Blake C, Shibata D, Danenberg PV, Laird PW: MethyLight: a high-throughput assay to measure DNA methylation. Nucleic Acids Res. 2000, 28: E32-10.1093/nar/28.8.e32.View ArticlePubMedPubMed CentralGoogle Scholar
- Müller HM, Widschwendter A, Fiegl H, Ivarsson L, Goebel G, Perkmann E, Marth C, Widschwendter M: DNA methylation in serum of breast cancer patients: an independent prognostic marker. Cancer Res. 2003, 63: 7641-7645.PubMedGoogle Scholar
- Ebert MP, Model F, Mooney S, Hale K, Lograsso J, Tonnes-Priddy L, Hoffmann J, Csepregi A, Röcken C, Molnar B, Schulz H-U, Malfertheiner P, Lofton-Day C: Aristaless-like homeobox-4 gene methylation is a potential marker for colorectal adenocarcinomas. Gastroenterology. 2006, 131: 1418-1430. 10.1053/j.gastro.2006.08.034.View ArticlePubMedGoogle Scholar
- Tas F, Aykan F, Alici S, Kaytan E, Aydiner A, Topuz E: Prognostic factors in pancreatic carcinoma: serum LDH levels predict survival in metastatic disease. Am J Clin Oncol. 2001, 24: 547-550. 10.1097/00000421-200112000-00003.View ArticlePubMedGoogle Scholar
- Pollheimer MJ, Kornprat P, Lindtner RA, Harbaum L, Schlemmer A, Rehak P, Langner C: Tumor necrosis is a new promising prognostic factor in colorectal cancer. Hum Pathol. 2010, 41: 1749-1757. 10.1016/j.humpath.2010.04.018.View ArticlePubMedGoogle Scholar
- Richards CH, Roxburgh CSD, Anderson JH, McKee RF, Foulis AK, Horgan PG, McMillan DC: Prognostic value of tumour necrosis and host inflammatory responses in colorectal cancer. Br J Surg. 2012, 99: 287-294. 10.1002/bjs.7755.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2407/14/245/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.