High recovery of cell-free methylated DNA based on a rapid bisulfite-treatment protocol

Colorectal cancer detected by liquid biopsy 2 years prior to clinical diagnosis in the HUNT study

BACKGROUND

Colorectal cancer (CRC) is often diagnosed in advanced stages. Circulating tumour DNA (ctDNA) has been proposed as an early diagnostic biomarker. However, as a screening tool, ctDNA has mainly been studied in selected populations at the time of clinical diagnosis. The aim of this study was to detect CRC by known ctDNA markers up to 2 years prior to clinical diagnosis.

METHODS

In this case-control study, methylated ctDNA markers were detected in plasma samples from 106 healthy controls and 106 individuals diagnosed with CRC within 24 months following participation in The Trøndelag Health Study.

RESULTS

The most specific single markers were BMP3, FLI1, IKZF1, SFRP1, SFRP2, NPTX2, SLC8A1 and VIM (specificity >70%). When combining these into a panel, the CRC sensitivity was 43% (95% CI 42.7-43.4) and the CRC specificity was 86% (95% CI 85.7-86.2). The findings were reproduced in an independent validation set of samples.

CONCLUSIONS

Detection of known methylated ctDNA markers of CRC is possible up to 2 years prior to the clinical diagnosis in an unselected population resembling the screening setting. This study supports the hypothesis that some patients could be diagnosed earlier, if ctDNA detection was part of the CRC screening programme.

Promoter hypermethylation of SFRP1 as a prognostic and potentially predictive blood-based biomarker in patients with stage III or IV pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma remains one of the major causes of cancer-related mortality globally. Unfortunately, current prognostic biomarkers are limited, and no predictive biomarkers exist. This study examined promoter hypermethylation of secreted frizzled-related protein 1 (phSFRP1) in cfDNA as a prognostic biomarker and predictor of treatment effect in patients with metastatic FOLFIRINOX-treated PDAC and locally advanced PDAC.

METHODS

We performed methylation-specific PCR of the SFRP1 genes' promoter region, based on bisulfite treatment. Survival was assessed as time-to-event data using the pseudo-observation method and analyzed with Kaplan-Meier curves and generalized linear regressions.

RESULTS

The study included 52 patients with FOLFIRINOX-treated metastatic PDAC. Patients with unmethylated (um) SFRP1 (n = 29) had a longer median overall survival (15.7 months) than those with phSFRP1 (6.8 months). In crude regression, phSFRP1 was associated with an increased risk of death of 36.9% (95% CI 12.0%-61.7%) and 19.8% (95% CI 1.9-37.6) at 12 and 24-months, respectively. In supplementary regression analysis, interaction terms between SFRP1 methylation status and treatment were significant, indicating reduced benefit of chemotherapy. Forty-four patients with locally advanced PDAC were included. phSFRP1 was associated with an increased risk of death at 24-months CONCLUSIONS: This indicates that phSFRP1 is a clinically useful prognostic biomarker in metastatic PDAC and possibly in locally advanced PDAC. Together with existing literature, results could indicate the value of cfDNA-measured phSFRP1 as a predictive biomarker of standard palliative chemotherapy in patients with metastatic PDAC. This could facilitate personalized treatment of patients with metastatic PDAC.

Promoter hypermethylation of SFRP1 as a prognostic and potentially predictive blood-based biomarker in patients with localized pancreatic ductal adenocarcinoma

Introduction

Current prognostic blood-based biomarkers for pancreatic adenocarcinoma (PDAC) are limited. Recently, promoter hypermethylation of SFRP1 (phSFRP1) has been linked to poor prognosis in patients with gemcitabine-treated stage IV PDAC. This study explores the effects of phSFRP1 in patients with lower stage PDAC.

Methods

Based on a bisulfite treatment process, the promoter region of the SFRP1 gene was analyzed with methylation-specific PCR. Kaplan-Meier curves, log-rank tests, and generalized linear regression analysis were used to assess restricted mean survival time survival at 12 and 24 months.

Results

The study included 211 patients with stage I-II PDAC. The median overall survival of patients with phSFRP1 was 13.1 months, compared to 19.6 months in patients with unmethylated SFRP1 (umSFRP1). In adjusted analysis, phSFRP1 was associated with a loss of 1.15 months (95%CI -2.11, -0.20) and 2.71 months (95%CI -2.71, -0.45) of life at 12 and 24 months, respectively. There was no significant effect of phSFRP1 on disease-free or progression-free survival. In stage I-II PDAC, patients with phSFRP1 have worse prognoses than patients with umSFRP1.

Discussion

Results could indicate that the poor prognosis may be caused by reduced benefit from adjuvant chemotherapy. SFRP1 may help guide the clinician and be a possible target for epigenetically modifying drugs.

Validation of SFRP1 Promoter Hypermethylation in Plasma as a Prognostic Marker for Survival and Gemcitabine Effectiveness in Patients with Stage IV Pancreatic Adenocarcinoma

Simple Summary

Pancreatic adenocarcinoma (PDAC) is a disease with an incredibly grim prognosis. Most patients die within one year of receiving the diagnosis. There are currently very few tools to help the clinician decide between treatment options and evaluate prognosis at an individual level. The aim of the current study was to assess the effect of promoter hypermethylation of secreted frizzled-related protein 1 (phSFRP1) as an independent prognostic blood-based biomarker in gemcitabine-treated patients with advanced PDAC. The study was conducted as a combined discovery and validation study. Analysis in both cohorts confirmed that patients with phSFRP1 had overall poorer survival compared to those without hypermethylation. Thus, phSFRP1 shows promise as an independent prognostic biomarker in this patient group and can hopefully aid the clinician and patient find the correct balance between quantity and quality of life.

Abstract

No reliable predictive blood-based biomarkers are available for determining survival from pancreatic adenocarcinoma (PDAC). This combined discovery and validation study examines promoter hypermethylation (ph) of secreted frizzled-related protein 1 (SFRP1) in plasma-derived cell-free DNA as an independent prognostic marker for survival and Gemcitabine effectiveness in patients with stage IV PDAC. We conducted methylation-specific polymerase chain reaction analysis of the promoter region of the SFRP1 gene, based on bisulfite treatment. Survival was analyzed with Kaplan–Meier curves, log-rank test, and Cox regression. The discovery cohort included 40 patients, 25 receiving Gem. Gem-treated patients with phSFRP1 had a shorter median overall survival (mOS) (4.4 months) than unmethylated patients (11.6 months). Adjusted Cox-regression yielded a hazard rate (HR) of 3.48 (1.39–8.70). The validation cohort included 58 Gem-treated patients. Patients with phSFRP1 had a shorter mOS (3.2 months) than unmethylated patients (6.3 months). Adjusted Cox regression yielded an HR of 3.53 (1.85–6.74). In both cohorts, phSFRP1 was associated with poorer survival in Gem-treated patients. This may indicate that tumors with phSFRP1 are more aggressive and less sensitive to Gem treatment. This knowledge may facilitate tailored treatment of patients with stage IV PDAC. Further studies are planned to examine phSFRP1 in more intensive chemotherapy regimens.

Guidelines for pre-analytical conditions for assessing the methylation of circulating cell-free DNA

Methylation analysis of circulating cell-free DNA (cirDNA), as a liquid biopsy, has a significant potential to advance the detection, prognosis, and treatment of cancer, as well as many genetic disorders. The role of epigenetics in disease development has been reported in several hereditary disorders, and epigenetic modifications are regarded as one of the earliest and most significant genomic aberrations that arise during carcinogenesis. Liquid biopsy can be employed for the detection of these epigenetic biomarkers. It consists of isolation (pre-analytical) and detection (analytical) phases. The choice of pre-analytical variables comprising cirDNA extraction and bisulfite conversion methods can affect the identification of cirDNA methylation. Indeed, different techniques give a different return of cirDNA, which confirms the importance of pre-analytical procedures in clinical diagnostics. Although novel techniques have been developed for the simplification of methylation analysis, the process remains complex, as the steps of DNA extraction, bisulfite treatment, and methylation detection are each carried out separately. Recent studies have noted the absence of any standard method for the pre-analytical processing of methylated cirDNA. We have therefore conducted a comprehensive and systematic review of the important pre-analytical and analytical variables and the patient-related factors which form the basis of our guidelines for analyzing methylated cirDNA in liquid biopsy.

Cell-free DNA promoter hypermethylation as a diagnostic marker for pancreatic ductal adenocarcinoma - An external validation study

BACKGROUND

We recently identified a diagnostic prediction model based on promoter hypermethylation of eight selected genes in plasma cell-free (cf) DNA, which showed promising results as a diagnostic biomarker for pancreatic ductal adenocarcinoma (PDAC). The aim of the present study was to validate this biomarker profile in an external patient cohort and examine any additional effect of serum CA 19-9.

METHODS

Patients with PDAC (n = 346, stage I-IV) and chronic pancreatitis (n = 25) were included. Methylation-specific PCR of a 28-gene panel was performed on serum cfDNA samples. The previously developed diagnostic prediction model (age>65 years, BMP3, RASSF1A, BNC1, MESTv2, TFPI2, APC, SFRP1 and SFRP2) was validated alone and in combination with serum CA 19-9 in this external patient cohort.

RESULTS

Patients with PDAC had a higher number of hypermethylated genes (mean 8.11, 95% CI 7.70-8.52) than patients with chronic pancreatitis (mean 5.60, 95% CI 4.42-6.78, p = 0.011). Validation of the diagnostic prediction model yielded an AUC of 0.77 (95% CI 0.69-0.84). The combination of serum CA 19-9 and our test had an AUC of 0.93 (95% CI 0.89-0.96) in the primary study and 0.85 (95% CI 0.79-0.91) in the validation study.

CONCLUSION

In this validation study, PDAC was associated with a higher number of hypermethylated genes in serum cfDNA than chronic pancreatitis. Our diagnostic test was superior to the predictive value of serum CA 19-9 alone in both the primary and the validation study. The combination of our test with CA 19-9 may serve as a clinically useful diagnostic biomarker for PDAC.

DNA methylation biomarkers in peripheral blood of patients with head and neck squamous cell carcinomas. A systematic review

BACKGROUND

Head and neck squamous cell carcinomas (HNSCC) are often diagnosed in advanced stages. In search of new diagnostic tools, focus has shifted towards the biological properties of the HNSCC, and the number of different biomarkers under investigation is rapidly growing.

OBJECTIVES

The objective was to review the current literature regarding aberrantly methylated DNA found in peripheral blood plasma or serum in patients with HNSCC and to evaluate the diagnostic accuracy of these changes.

METHODS

The inclusion criteria were clinical studies involving patients with verified HNSCC that reported findings of aberrantly methylated DNA in peripheral blood serum or plasma. We systematically searched PubMed, OVID Embase and Cochrane Library. In addition to the search, we performed forward and backward chaining in references and Web of Science. The protocol was registered in PROSPERO: CRD42019135406. Two authors independently extracted data. The quality and the risk of bias of the included studies were assessed by the QUADAS-2 tool.

RESULTS

A total of 1,743 studies were found eligible for screening, while ultimately seven studies were included. All studies were found to have methodological weaknesses, mainly concerning patient selection bias. The best individual marker of HNSCC was Septin 9 in plasma with a sensitivity of 57% and a specificity of 95%.

CONCLUSIONS

None of the aberrantly methylated genes found in the retrieved studies are applicable as single diagnostic markers for HNSCC and the best gene-panels still lack diagnostic accuracy. Future studies may benefit from newer sequencing techniques but validation studies with well-designed cohorts are also needed in the process of developing epigenetic based diagnostic tests for HNSCC.

The prognostic efficacy of cell-free DNA hypermethylation in colorectal cancer

Epigenetic alterations in colorectal cancer (CRC) cause important differences in the underlying tumor biology and aggressiveness. DNA hypermethylation is central for the development of CRC but the prognostic impact remains elusive. We aimed to assess the association between cell-free hypermethylated DNA and stage and survival in colorectal cancer (CRC). We analyzed pre-treatment plasma samples from 193 patients with CRC. Thirty gene-promoter regions were analyzed using methylation specific PCR. We compared the median number (range) of hypermethylated promoter regions with CRC stage, and constructed a multivariable Cox-regression model adjusted for stage, to evaluate the added prognostic information. The median number of hypermethylated promoter regions was nine (0-28) in patients with distant metastasis compared to five (0-19) in patients without metastatic disease (p < 0.0001). The majority of the hypermethylated promoter regions inferred a poor prognosis. Cox-regression analysis adjusted for patient age, sex, pre-treatment CEA-levels, and disease stage, showed that RARB (HR = 1.99, 95% CI [1.07, 3.72]) and RASSF1A (HR = 3.35, 95% CI [1.76, 6.38]) hypermethylation inferred a significant effect on survival. The risk of metastasis increase with the number of cell-free hypermethylated promoter regions. The presence of RARB and RASSF1A hypermethylation indicated aggressive disease, regardless of stage at the time of diagnosis.

An optimized rapid bisulfite conversion method with high recovery of cell-free DNA

BACKGROUND

Methylation analysis of cell-free DNA is a encouraging tool for tumor diagnosis, monitoring and prognosis. Sensitivity of methylation analysis is a very important matter due to the tiny amounts of cell-free DNA available in plasma. Most current methods of DNA methylation analysis are based on the difference of bisulfite-mediated deamination of cytosine between cytosine and 5-methylcytosine. However, the recovery of bisulfite-converted DNA based on current methods is very poor for the methylation analysis of cell-free DNA.

RESULTS

We optimized a rapid method for the crucial steps of bisulfite conversion with high recovery of cell-free DNA. A rapid deamination step and alkaline desulfonation was combined with the purification of DNA on a silica column. The conversion efficiency and recovery of bisulfite-treated DNA was investigated by the droplet digital PCR. The optimization of the reaction results in complete cytosine conversion in 30 min at 70 °C and about 65% of recovery of bisulfite-treated cell-free DNA, which is higher than current methods.

CONCLUSIONS

The method allows high recovery from low levels of bisulfite-treated cell-free DNA, enhancing the analysis sensitivity of methylation detection from cell-free DNA.

Cell-free DNA promoter hypermethylation in plasma as a predictive marker for survival of patients with pancreatic adenocarcinoma

Introduction

Few prognostic biomarkers are available for pancreatic cancer. The aim of this study is to examine the correlation between the survival of pancreatic adenocarcinoma patients and hypermethylated genes in plasma-derived cell-free DNA.

Methods

Consecutive patients with pancreatic adenocarcinoma were prospectively included and staged according to the TNM classification. Methylation-specific PCR of 28 genes was conducted. A survival prediction model independent of cancer stage and stage-specific survival prediction models were developed by multivariable Cox regression analysis using backward stepwise selection.

Results

Ninety-five patients with pancreatic adenocarcinoma were included. Patients with more than 10 hypermethylated genes had a HR of 2.03 (95% CI; 1.15-3.57) compared to patients with fewer hypermethylated genes. Three survival prediction models were developed: Total group; (American Society of Anesthesiologists score (ASA)=3, GSTP1, SFRP2, BNC1, SFRP1, TFPI2, and WNT5A) Risk groups 2, 3 and 4 had a HR of 2.65 (95% CI; 1.24-5.66), 4.34 (95% CI; 1.98-9.51) and 21.19 (95% CI; 8.61-52.15), respectively, compared to risk group 1. Stage I-II; (ASA=3, SFRP2, and MESTv2) Risk groups 2, 3 and 4 had a HR of 4.83 (95% CI; 2.01-11.57), 9.12 (95% CI; 2.18-38.25) and 70.90 (95% CI; 12.63-397.96), respectively, compared to risk group 1. Stage IV; (BMP3, NPTX2, SFRP1, and MGMT) Risk group 2 had a HR of 5.23 (95% CI; 2.13-12.82) compared to risk group 1.

Conclusion

Prediction models based on cell-free DNA hypermethylation stratified pancreatic adenocarcinoma patients into risk groups according to survival. The models have the potential to work as prognostic biomarkers. However, further validation of the results is required to substantiate the findings.

Promoter hypermethylation in plasma-derived cell-free DNA as a prognostic marker for pancreatic adenocarcinoma staging

Correct staging of pancreatic cancer is paramount, as treatment is stage specific. However, minimally invasive tools to facilitate staging are lacking. DNA promoter hypermethylation is a hallmark of cancer. The aim of this study is to evaluate promoter hypermethylation in cell-free DNA as a prognostic marker for stage classification of pancreatic adenocarcinoma. Consecutive patients with pancreatic adenocarcinoma were prospectively included. Plasma samples were obtained before diagnostic work-up and treatment. Patients were staged according to the TNM classification. Methylation-specific PCR of 28 genes was performed. Prognostic prediction models for staging of pancreatic adenocarcinoma were developed by multivariable logistic regression analysis using stepwise backwards elimination. Ninety-five patients with pancreatic adenocarcinoma were included. The mean number of hypermethylated genes was identical for stage I, II and III disease (7.09 (95% CI; 5.51-8.66), 7.00 (95% CI; 5.93-8.07) and 6.77 (95% CI; 5.08-8.46)), respectively, and highly significantly different from stage IV disease (10.24 (95% CI; 8.88-11.60)). The prediction model (SEPT9v2, SST, ALX4, CDKN2B, HIC1, MLH1, NEUROG1, and BNC1) enabled the differentiation of stage IV from stage I-III disease (AUC of 0.87 (cut point 0.55; sensitivity 74%, specificity 87%)). Model (MLH1, SEPT9v2, BNC1, ALX4, CDKN2B, NEUROG1, WNT5A, and TFPI2) enabled the differentiation of stage I-II from stage III-IV disease (AUC of 0.82 (cut point 0.66; sensitivity 73%, specificity 80%)). Cell-free DNA promoter hypermethylation has the potential to be blood-based prognostic markers for pancreatic adenocarcinoma, as panels of hypermethylated genes enables the differentiation according to cancer stage. However, further validation is required.

Hypermethylated DNA, a circulating biomarker for colorectal cancer detection

Background

Colorectal cancer (CRC) is one of the most common cancers in the western world. Screening is an efficient method of reducing cancer-related mortality. Molecular biomarkers for cancer in general and CRC in particular have been proposed, and hypermethylated DNA from stool or blood samples are already implemented as biomarkers for CRC screening.

We aimed to evaluate the performance of proven hypermethylated DNA promoter regions as plasma based biomarkers for CRC detection.

Methods

We conducted a cross-sectional case-control study of 193 CRC patients and 102 colonoscopy-verified healthy controls. Using methylation specific polymerase chain reaction, we evaluated 30 DNA promoter regions previously found to be CRC specific. We used multivariable logistic regression with stepwise backwards selection, and subsequent leave-pair-out cross validation, to calculate the optimism corrected area under the receiver operating characteristics curve (AUC) for all stage as well as early stage CRC.

Results

None of the individual DNA promoter regions provided an overall sensitivity above 30% at a reasonable specificity. However, seven hypermethylated promoter regions (ALX4, BMP3, NPTX2, RARB, SDC2, SEPT9, and VIM) along with the covariates sex and age yielded an optimism corrected AUC of 0.86 for all stage CRC and 0.85 for early stage CRC. Overall sensitivity for CRC detection was 90.7% at 72.5% specificity using a cut point value of 0.5.

Conclusions

Individual hypermethylated DNA promoter regions have limited value as CRC screening markers. However, a panel of seven hypermethylated promoter regions show great promise as a model for CRC detection.

Comparative analysis of 12 different kits for bisulfite conversion of circulating cell-free DNA

Blood circulating cell-free DNA (cfDNA) is becoming popular in the search of promising predictive and prognostic biomarkers. Among these biomarkers, cfDNA methylation markers have especially gained considerable attention. A significant challenge in the utilization of cfDNA methylation markers is the limited amount of cfDNA available for analyses; reportedly, bisulfite conversion (BSC) reduce cfDNA amounts even further. Nevertheless, few efforts have focused on ensuring high cfDNA conversion efficiency and recovery after BSC. To compare cfDNA recovery of different BSC methods, we compared 12 different commercially available BSC kits. We tested whether DNA recovery was affected by the molecular weight and/or quantity of input DNA. We also tested BSC efficiency for each kit. We found that recovery varied for DNA fragments of different lengths: certain kits recovered short fragments better than others, and only 3 kits recovered DNA fragments of <100 bp well. In contrast, DNA input amount did not seem to affect DNA recovery: for quantities spanning between 820 and ∼25,000 genome equivalents per BSC, a linear relation was found between input and recovery amount. Overall, mean recovery ranged between 9 and 32%, with BSC efficiency of 97-99.9%. When plasma cfDNA was used as input for BSC, recovery varied from 22% for the poorest and 66% for the best performing kits, while conversion efficiency ranged from 96 to 100% among different kits. In conclusion, clear performance differences exist between commercially available BSC kits, both in terms of DNA recovery and conversion efficiency. The choice of BSC kit can substantially impact the amount of converted cfDNA available for downstream analysis, which is critical in a cfDNA methylation marker setting.

Cell-free DNA promoter hypermethylation in plasma as a diagnostic marker for pancreatic adenocarcinoma

BACKGROUND

Pancreatic cancer has a 5-year survival rate of only 5-7%. Difficulties in detecting pancreatic cancer at early stages results in the high mortality and substantiates the need for additional diagnostic tools. Surgery is the only curative treatment and unfortunately only possible in localized tumours. A diagnostic biomarker for pancreatic cancer will have a major impact on patient survival by facilitating early detection and the possibility for curative treatment. DNA promoter hypermethylation is a mechanism of early carcinogenesis, which can cause inactivation of tumour suppressor genes. The aim of this study was to examine promoter hypermethylation in a panel of selected genes from cell-free DNA, as a diagnostic marker for pancreatic adenocarcinoma.

METHODS

Patients with suspected or biopsy-verified pancreatic cancer were included prospectively and consecutively. Patients with chronic/acute pancreatitis were included as additional benign control groups. Based on an optimized accelerated bisulfite treatment protocol, methylation-specific PCR of a 28 gene panel was performed on plasma samples. A diagnostic prediction model was developed by multivariable logistic regression analysis using backward stepwise elimination.

RESULTS

Patients with pancreatic adenocarcinoma (n = 95), chronic pancreatitis (n = 97) and acute pancreatitis (n = 59) and patients screened, but negative for pancreatic adenocarcinoma (n = 27), were included. The difference in mean number of methylated genes in the cancer group (8.41 (95% CI 7.62-9.20)) vs the total control group (4.74 (95% CI 4.40-5.08)) was highly significant (p < 0.001). A diagnostic prediction model (age >65, BMP3, RASSF1A, BNC1, MESTv2, TFPI2, APC, SFRP1 and SFRP2) had an area under the curve of 0.86 (sensitivity 76%, specificity 83%). The model performance was independent of cancer stage.

CONCLUSIONS

Cell-free DNA promoter hypermethylation has the potential to be a diagnostic marker for pancreatic adenocarcinoma and differentiate between malignant and benign pancreatic disease. This study brings us closer to a clinical useful diagnostic marker for pancreatic cancer, which is urgently needed. External validation is, however, required before the test can be applied in the clinic.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02079363.

Hypermethylated DNA as a biomarker for colorectal cancer: a systematic review

AIM

Improved methods for early detection of colorectal cancer (CRC) are essential for increasing survival. Hypermethylated DNA in blood or stool has been proposed as a biomarker for CRC. Biochemical methods have improved in recent years, and several hypermethylated genes that are sensitive and specific for CRC have been proposed. Articles describing the use of hypermethylated promoter regions in blood or stool as biomarkers for CRC were systematically reviewed.

METHOD

A systematic literature search was performed using the Medline, Web of Science and Embase databases. Studies were included if they analysed hypermethylated genes from stool or blood samples in correlation with CRC. Studies in languages other than English and those based on animal models or cell lines were excluded.

RESULTS

The literature search yielded 74 articles, including 43 addressing blood samples and 31 addressing stool samples. In blood samples, hypermethylated ALX4, FBN2, HLTF, P16, TMEFF1 and VIM were associated with poor prognosis, hypermethylated APC, NEUROG1, RASSF1A, RASSF2A, SDC2, SEPT9, TAC1 and THBD were detected in early stage CRC and hypermethylated P16 and TFPI2 were associated with CRC recurrence. In stool samples, hypermethylated BMP3, PHACTR3, SFRP2, SPG20, TFPI2 and TMEFF2 were associated with early stage CRC.

CONCLUSION

Hypermethylation of the promoters of specific genes measured in blood or stool samples could be used as a CRC biomarker and provide prognostic information. The majority of studies, however, include only a few patients with poorly defined control groups. Further studies are therefore needed before hypermethylated DNA can be widely applied as a clinical biomarker for CRC detection and prognosis.

DNA methylation analysis of steroid hormone receptor genes

Steroid hormone receptors (SHR) are important transcription factors for regulating different physiological and pathological processes. Their altered expression has been strongly associated to cancer progression. Epigenetic marks such as DNA methylation have been proposed as one of the regulatory mechanisms for SHR expression in cancer. DNA methylation occurs at CpG dinucleotides, which form clusters known as CpG islands. These islands are mostly observed at promoter regions of housekeeping genes, and their aberrant methylation in cancer cells is associated with silencing of tumor-suppressor gene expression. SHR genes are characterized for presenting alternative promoters with different CpG island content, which are prone to be methylated. The method of choice for studying DNA methylation is bisulfite sequencing, since it provides information about the methylation pattern at single-nucleotide level. The method is based on the deamination of cytosine residues to uracil after treatment with sodium bisulfite. The converted DNA is amplified by a polymerase chain reaction, cloned, and sequenced. Here, we describe a protocol for bisulfite sequencing suitable for analyzing different CpG regions in SHR genes.

Methylated DNA for monitoring tumor growth and regression: how do we get there?

A wide range of protein cancer biomarkers is currently recommended in international guidelines for monitoring the growth and regression of solid tumors. However, a number of these markers are also present in low concentrations in blood obtained from healthy individuals and from patients with benign diseases. In contrast, evidence has accumulated that suggests that modified methylated DNA is strongly related to the cancer phenotype. The modifications found in modified methylated DNA include a global loss of methylation in the genomes of the tumor cells as well as focal hypermethylation of gene promoters. Because tumor cells naturally secrete DNA and upon cell death leak DNA, modified methylated DNA can be detected in blood, urine, sputum and other body fluids. At present international guidelines do not include recommendations for monitoring modified methylated DNA. The low level of evidence can partly be explained by incomplete collection of serial blood samples, by analytical challenges, and by lack of knowledge of how monitoring studies should be designed and how serial marker data obtained from individual patients should be interpreted. Here, we review the clinical validity and utility of methylated DNA for monitoring the activity of malignant disease.

Microsphere-based multiplex analysis of DNA methylation in acute myeloid leukemia

Aberrant regulation of DNA methylation is characteristic of cancer cells and clearly influences phenotypes of various malignancies. Despite clear correlations between DNA methylation and patient outcome, tests that directly measure multiple-locus DNA methylation are typically expensive and technically challenging. Previous studies have demonstrated that the prognosis of patients with acute myeloid leukemia can be predicted by the DNA methylation pattern of 18 loci. We have developed a novel strategy, termed microsphere HpaII tiny fragment enrichment by ligation-mediated PCR (MELP), to simultaneously analyze the DNA methylation pattern at these loci using methylation-specific DNA digestion, fluorescently labeled microspheres, and branched DNA hybridization. The method uses techniques that are inexpensive and easily performed in a molecular laboratory. MELP accurately reflects the methylation levels at each locus analyzed and segregates patients with acute myeloid leukemia into prognostic subgroups. Our results demonstrate the usefulness of MELP as a platform for simultaneous evaluation of DNA methylation of multiple loci.

Genome-wide screening for understanding the role of DNA methylation in colorectal cancer

DNA methylation analysis methods have undergone an impressive revolution over the past 15 years. Regarding colorectal cancer (CRC), the localization and distribution of several differently methylated genes have been determined by genome-wide DNA methylation assays. These genes do not just influence the pathogenesis of CRC, but can be used further as diagnostic or prognostic markers. Moreover, the identified four DNA methylation-based subgroups of CRC have important clinical and therapeutic merit. Since genome-wide DNA methylation analyzes result in a large amount of data, there is a need for complex bioinformatic and pathway analysis. Future challenges in epigenetic alterations of CRC include the demand for comprehensive identification and experimental validation of gene abnormalities. By introduction of genome-wide DNA methylation profiling into clinical practice not only the patients' risk stratification but development of targeted therapies will also be possible.