Development of a diagnostic microarray assay to assess the risk of recurrence of prostate cancer based on PITX2 DNA methylation

PITX2 methylation: a novel and effective biomarker for monitoring biochemical recurrence risk of prostate cancer

AIMS

Prostate cancer is one of the most common malignancies in men. Biochemical recurrence (BCR) and progression following curative treatment pose a significant public health challenge. Thus, it is essential to explore effective biomarkers for disease progression monitoring and risk stratification. The promoter region of the paired-like homeodomain transcription factor 2 (PITX2) gene has been found to be frequently methylated in prostate cancer. However, the prognostic role of PITX2 methylation in prostate cancer and which patients most likely to be recommended for PITX2 methylation tests to assess BCR risk remain controversial. Therefore, a systematic review was performed to explore the relationship of PITX2 methylation with the BCR risk of prostate cancer.

METHODS

The PubMed, EMBASE, and Cochrane Library databases were systematically searched for eligible studies. Seven studies with a total of 2185 patients were included. Pooled hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) were calculated.

RESULTS

The overall HR was 2.71 (95% CI, 2.21-3.31), suggesting that PITX2 methylation has an adverse impact on BCR of prostate cancer. The pooled estimate of 5-year BCR-free survival for patients with a high methylation status was significantly lower than that for patients with a low methylation status (71% vs 90%; odds ratio [OR] = 3.50; 95% CI, 2.67-4.60, P = .000). A subgroup analysis was conducted according to detection method; the combined HRs were 2.68 (95% CI, 2.02-3.55) for quantitative methylation-specific PCR (qMSP) and 3.29 (95% CI, 2.31-4.68) for microarray EpiChip. In subgroups defined by region, Gleason score, pathological stage, surgical margin status and ethnicity, high methylation status was also associated with BCR of prostate cancer.

CONCLUSIONS

As an effective biomarker, PITX2 methylation is feasible for individualized BCR risk assessment of prostate cancer following radical prostatectomy.

Evaluation of bisulfite kits for DNA methylation profiling in terms of DNA fragmentation and DNA recovery using digital PCR

DNA methylation is one of the most important epigenetic modifications in the regulation of gene transcription. The current gold standard to study this modification is bisulfite sequencing. Although multiple commercial bisulfite treatment kits provide good conversion efficiencies, DNA loss and especially DNA fragmentation remain troublesome. This hampers DNA methylation profiling of long DNA sequences. Here, we explored the performance of twelve commercial bisulfite kits by an in-depth comparison of DNA fragmentation using gel electrophoresis, qPCR and digital PCR, DNA recovery by spectroscopic measurements and digital PCR and conversion efficiency by next generation sequencing. The results show a clear performance difference between the bisulfite kits, and depending on the specific goal of the study, the most appropriate kit might differ. Moreover, we demonstrated that digital PCR is a valuable method to monitor both DNA fragmentation as well as DNA recovery after bisulfite treatment.

Intragenic DNA methylation of PITX1 and the adjacent long non-coding RNA C5orf66-AS1 are prognostic biomarkers in patients with head and neck squamous cell carcinomas

Background

Patients with squamous cell cancer of the head and neck region (HNSCC) are at risk for disease recurrence and metastases, even after initial successful therapy. A tissue-based biomarker could be beneficial to guide treatment as well as post-treatment surveillance. Gene methylation status has been recently identified as powerful prognostic biomarker in HNSCC. We therefore evaluated the methylation status of the homeobox gene PITX1 and the adjacent long intergenic non-coding RNA (lincRNA) C5orf66-AS1 in publicly available datasets.

Methods

Gene methylation and expression data from 528 patients with HNSCC included in The Cancer Genome Atlas (TCGA, there obtained by using the Infinium HumanMethylation450 BeadChip Kit) were evaluated and methylation and expression levels of PITX1 and lincRNA C5orf66-AS1 was correlated with overall survival and other parameters. Thus, ten beads targeting PITX1 exon 3 and three beads targeting lincRNA C5orf66-AS1 were identified as significant candidates. The mean methylation of these beads was used for further correlation and the median was employed for dichotomization.

Results

Both PITX1 exon 3 and lincRNA C5orf66-AS1 were significantly higher methylated in tumor tissue than in normal adjacent tissue (NAT) (PITX1 exon 3: tumor tissue 58.1%, NAT: 31.7%, p<0.001; lincRNA C5orf66-AS1: tumor tissue: 27.4%, NAT: 18.9%, p<0.001). In a univariate analysis, hypermethylation of both loci was significantly associated with the risk of death (univariate: exon 3: Hazard ratio (HR): 4.97 [1.78–16.71], p = 0.010, lincRNA C5orf66-AS1: Hazard ratio (HR): 12.23 [3.01–49.74], p<0.001). PITX1 exon 3 and lincRNA C5orf66-AS1 methylation was also significantly correlated with tumor localization, T category, human papilloma virus (HPV)-negative and p16-negative tumors and tumor grade. Kaplan-Meier analysis showed, that lincRNA C5orf66-AS1 hypomethylation was significantly associated with overall survival (p = 0.001) in the entire cohort as well in a subgroup of HPV-negative tumors (p = 0.003) and in patients with laryngeal tumors (p = 0.022).

Conclusion

Methylation status of PITX1 and even more so of lincRNA C5orf66-AS1 is a promising prognostic biomarker in HNSCC, in particular for HPV-negative patients. Further prospective evaluation is warranted.

Comprehensive Evaluation of TFF3 Promoter Hypomethylation and Molecular Biomarker Potential for Prostate Cancer Diagnosis and Prognosis

Overdiagnosis and overtreatment of clinically insignificant tumors remains a major problem in prostate cancer (PC) due to suboptimal diagnostic and prognostic tools. Thus, novel biomarkers are urgently needed. In this study, we investigated the biomarker potential of Trefoil factor 3 (TFF3) promoter methylation and RNA expression levels for PC. Initially, by quantitative methylation specific PCR (qMSP) analysis of a large radical prostatectomy (RP) cohort (n = 292), we found that the TFF3 promoter was significantly hypomethylated in PC compared to non-malignant (NM) prostate tissue samples (p < 0.001) with an AUC (area under the curve) of 0.908 by receiver operating characteristics (ROC) curve analysis. Moreover, significant TFF3 promoter hypomethylation (p ≤ 0.010) as well as overexpression (p < 0.001) was found in PC samples from another large independent patient sample set (498 PC vs. 67 NM) analyzed by Illumina 450K DNA methylation arrays and/or RNA sequencing. TFF3 promoter methylation and transcriptional expression levels were inversely correlated, suggesting that epigenetic mechanisms contribute to the regulation of gene activity. Furthermore, low TFF3 expression was significantly associated with high ERG, ETS transcription factor (ERG) expression (p < 0.001), as well as with high Gleason score (p < 0.001), advanced pathological T-stage (p < 0.001), and prostate-specific antigen (PSA) recurrence after RP (p = 0.013; univariate Cox regression analysis). There were no significant associations between TFF3 promoter methylation levels, ERG status, or PSA recurrence in these RP cohorts. In conclusion, our results demonstrated diagnostic biomarker potential of TFF3 promoter hypomethylation for PC as well as prognostic biomarker potential of TFF3 RNA expression. To the best of our knowledge, this is the most comprehensive study of TFF3 promoter methylation and transcriptional expression in PC to date.

Clinical performance validation of PITX2 DNA methylation as prognostic biomarker in patients with head and neck squamous cell carcinoma

BACKGROUND

Despite advances in combined modality therapy, outcomes in head and neck squamous cell cancer (HNSCC) remain dismal with five-year overall survival rates of less than 50%. Prognostic biomarkers are urgently needed to identify patients with a high risk of death after initial curative treatment. Methylation status of the paired-like homeodomain transcription factor 2 (PITX2) has recently emerged as a powerful prognostic biomarker in various cancers. In the present study, the clinical performance of PITX2 methylation was validated in a HNSCC cohort by means of an independent analytical platform (Infinium HumanMethylation450 BeadChip, Illumina, Inc.).

METHODS

A total of 528 HNSCC patients from The Cancer Genome Atlas (TCGA) were included in the study. Death was defined as primary endpoint. PITX2 methylation was correlated with overall survival and clinicopathological parameters.

RESULTS

PITX2 methylation was significantly associated with sex, tumor site, p16 status, and grade. In univariate Cox proportional hazards analysis, PITX2 hypermethylation analyzed as continuous and dichotomized variable was significantly associated with prolonged overall survival of HNSCC patients (continuous: hazard ratio (HR) = 0.19 [95%CI: 0.04-0.88], p = 0.034; dichotomized: HR = 0.52 [95%CI: 0.33-0.84], p = 0.007). In multivariate Cox analysis including established clinicopathological parameters, PITX2 promoter methylation was confirmed as prognostic factor (HR = 0.28 [95%CI: 0.09-0.84], p = 0.023).

CONCLUSION

Using an independent analytical platform, PITX2 methylation was validated as a prognostic biomarker in HNSCC patients, identifying patients that potentially benefit from intensified surveillance and/or administration of adjuvant/neodjuvant treatment, i.e. immunotherapy.

PITX3 DNA methylation is an independent predictor of overall survival in patients with head and neck squamous cell carcinoma

BACKGROUND

Molecular biomarkers assisting risk-group assignment and subsequent treatment stratification are urgently needed for patients with squamous cell cancer of the head and neck region (HNSCC). Aberrant methylation is a frequent event in cancer and, therefore, a promising source for potential biomarkers. Here, the methylation status of the paired-like homeodomain transcription factor 3 (PITX3) was evaluated in HNSCC.

METHODS

Using a quantitative real-time PCR, PITX3 methylation was assessed in a cohort of 326 HNSCC patients treated for localized or locally advanced disease (training cohort). The results were validated with Infinium HumanMethylation450 BeadChip data from a 528 HNSCC patient cohort (validation cohort) generated by The Cancer Genome Atlas (TCGA) Research Network.

RESULTS

PITX3 methylation was significantly higher methylated in tumor compared to normal adjacent tissue (NAT; training cohort: median methylation NAT 32.3%, tumor 71.8%, p < 0.001; validation cohort: median methylation NAT 16.9%, tumor 35.9%, p < 0.001). PITX3 methylation was also significantly correlated with lymph node status both in the training (p = 0.006) and validation (p < 0.001) cohort. PITX3 methylation was significantly higher in HPV-associated (p16-positive) tumors compared to p16-negative tumors (training cohort: 73.7 vs. 66.2%, p = 0.013; validation cohort: 40.0 vs. 33.1%, p = 0.015). Hypermethylation was significantly associated with the risk of death (training cohort: hazard ratio (HR) = 1.80, [95% confidence interval (CI) 1.20-2.69], p = 0.005; validation cohort: HR = 1.43, [95% CI 1.05-1.95], p = 0.022). In multivariate Cox analyses, PITX3 added independent prognostic information. Messenger RNA (mRNA) expression analysis revealed an inverse correlation with PITX3 methylation in the TCGA cohort.

CONCLUSIONS

PITX3 DNA methylation is an independent prognostic biomarker for overall survival in patients with HNSCC and might aid in the process of risk stratification for individualized treatment.

PITX2 DNA Methylation as Biomarker for Individualized Risk Assessment of Prostate Cancer in Core Biopsies

Hypermethylation of the paired-like homeodomain transcription factor 2 (PITX2) gene is a strong predictor of the risk of biochemical recurrence in patients with prostate cancer (PCa) after radical prostatectomy. We investigate whether PITX2 methylation is feasible for individualized risk assessment in prostate core biopsies before surgery. A quantitative, methylation-specific real-time PCR was used to measure PITX2 in three cohorts: i) matched samples of neoplastic and nonneoplastic tissue from 24 patients with PCa, ii) a well-characterized cohort of 300 patients with PCa after radical prostatectomy, and iii) core biopsy specimens from 32 patients with PCa and 31 patients with benign prostatic disease. PITX2 methylation discriminated between neoplastic and nonneoplastic tissue in patients with PCa (P < 0.001). In the second cohort, PITX2 methylation significantly correlated with clinicopathologic parameters, and PITX2 hypermethylation predicted an increased risk of biochemical recurrence in univariate Cox proportional hazards regression analysis (hazard ratio, 1.77; P = 0.046) and Kaplan-Meier analysis (P = 0.043). In 753 prostate biopsies, 720 (95.6%) were applicable for analysis, rendering the assay feasible for diagnostic biopsies. PITX2 methylation was furthermore significantly increased in tumor-positive biopsies and strongly correlated with International Society of Urological Pathology (ISUP) grade groups. This study indicates that the PITX2 methylation assay is feasible in prostate biopsies and might add valuable prognostic information for risk assessment in a presurgical diagnostic setting.

Bisulfite Conversion of DNA from Tissues, Cell Lines, Buffy Coat, FFPE Tissues, Microdissected Cells, Swabs, Sputum, Aspirates, Lavages, Effusions, Plasma, Serum, and Urine

Locus-specific analyses of DNA methylation patterns usually require a bisulfite conversion of the DNA, where cytosines are deaminated to uracils, while methylated and hydroxymethylated cytosines remain unaffected. The specific discrimination of hydroxymethylation and methylation can be achieved by introducing an oxidation of 5-hydroxymethylcytosines to 5-formylcytosines and subsequent bisulfite-mediated deamination of 5-formylcytosines.DNA methylation analysis of cell-free circulating DNA in liquid biopsies, i.e., blood samples (serum and plasma), urine, aspirates, bronchial lavages, pleural effusions, and ascites, is of great interest in clinical research. However, due to the generally low concentration of circulating cell-free DNA in body fluids, high volumes need to be analyzed. A reduction of this volume, e.g., by means of a polymer-mediated enrichment, is required in order to facilitate the bisulfite conversion. Further, these sample types usually contain a cellular fraction which is of additional interest and requires specific protocols for the sample preparation.Formalin-fixed, paraffin-embedded (FFPE) tissue is the most commonly used source for tissue-based clinical research. Due to degradation and covalent modifications of DNA in FFPE tissue samples, optimized protocols for the DNA preparation and bisulfite conversion are required.This chapter describes methods and protocols for the sample preparation and subsequent high-speed bisulfite conversion and DNA clean-up for several types of relevant samples, i.e., serum, plasma, urine, buffy coat, aspirates, sputum, lavages, effusions, ascites, swabs, fresh tissues, cell lines, FFPE tissues, and laser microdissected cells.Additionally, two real-time PCR assays for DNA quantification and quality control are described. The cytosine-free fragment (CFF) assay allows for the simultaneous quantification of bisulfite converted and total DNA and thus the determination of bisulfite conversion efficiency. The Mer9 real-time PCR assay amplifies the bisulfite converted sequence of the repetitive element Mer9 and enables the accurate quantification of minute DNA amounts, as present in microdissected cells and body fluids.

DNA Methylation of PITX2 and PANCR Is Prognostic for Overall Survival in Patients with Resected Adenocarcinomas of the Biliary Tract

Biliary tract cancers (BTC) are rare but highly aggressive malignant epithelial tumors. In order to improve the outcome in this lethal disease, novel biomarkers for diagnosis, prognosis, and therapy response prediction are urgently needed. DNA promoter methylation of PITX2 variants (PITX2ab, PITX2c) and intragenic methylation of the PITX2 adjacent non-coding RNA (PANCR) were investigated by methylations-specific qPCR assays in formalin-fixed paraffin-embedded tissue from 80 patients after resection for BTC. Results were correlated with clinicopathologic data and outcome. PITX2 variants and PANCR showed significant hypermethylation in tumor vs. normal adjacent tissue (p < 0.001 and p = 0.015), respectively. In survival analysis, dichotomized DNA methylation of variant PITX2c and PANCR were significantly associated with overall survival (OS). Patients with high tumor methylation levels of PITX2c had a shorter OS compared to patients with low methylation (12 vs. 40 months OS; HR 2.48 [1.38-4.48], p = 0.002). In contrast, PANCR hypermethylation was associated with prolonged survival (25 vs. 19 months OS; HR 0.54 [0.30-0.94], p = 0.015) and qualified as an independent prognostic factor on multivariate analysis. The biomarkers investigated in this study may help to identify BTC subpopulations at risk for worse survival. Further studies are needed to evaluate if PITX2 might be a clinically useful biomarker for an optimized and individualized treatment.

PITX3 promoter methylation is a prognostic biomarker for biochemical recurrence-free survival in prostate cancer patients after radical prostatectomy

BACKGROUND

Molecular biomarkers that might help to distinguish between more aggressive and clinically insignificant prostate cancers (PCa) are still urgently needed. Aberrant DNA methylation as a common molecular alteration in PCa seems to be a promising source for such biomarkers. In this study, PITX3 DNA methylation (mPITX3) and its potential role as a prognostic biomarker were investigated. Furthermore, mPITX3 was analyzed in combination with the established PCa methylation biomarker PITX2 (mPITX2).

METHODS

mPITX3 and mPITX2 were assessed by a quantitative real-time PCR and by means of the Infinium HumanMethylation450 BeadChip. BeadChip data were obtained from The Cancer Genome Atlas (TCGA) Research Network. DNA methylation differences between normal adjacent, benign hyperplastic, and carcinomatous prostate tissues were examined in the TCGA dataset as well as in prostatectomy specimens from the University Hospital Bonn. Retrospective analyses of biochemical recurrence (BCR) were conducted in a training cohort (n = 498) from the TCGA and an independent validation cohort (n = 300) from the University Hospital Bonn. All patients received radical prostatectomy.

RESULTS

In PCa tissue, mPITX3 was increased significantly compared to normal and benign hyperplastic tissue. In univariate Cox proportional hazards analyses, mPITX3 showed a significant prognostic value for BCR (training cohort: hazard ratio (HR) = 1.83 (95 % CI 1.07-3.11), p = 0.027; validation cohort: HR = 2.56 (95 % CI 1.44-4.54), p = 0.001). A combined evaluation with PITX2 methylation further revealed that hypermethylation of a single PITX gene member (either PITX2 or PITX3) identifies an intermediate risk group.

CONCLUSIONS

PITX3 DNA methylation alone and in combination with PITX2 is a promising biomarker for the risk stratification of PCa patients and adds relevant prognostic information to common clinically implemented parameters. Further studies are required to determine whether the results are transferable to a biopsy-based patient cohort. Trial registration: Patients for this unregistered study were enrolled retrospectively.

Large-scale evaluation of SLC18A2 in prostate cancer reveals diagnostic and prognostic biomarker potential at three molecular levels

Limitations of current diagnostic and prognostic tools for prostate cancer (PC) have led to over-diagnosis and over-treatment. Here, we investigate the biomarker potential of the SLC18A2 (VMAT2) gene for PC at three molecular levels. Thus, SLC18A2 promoter methylation was analyzed in 767 malignant and 78 benign radical prostatectomy (RP) samples using methylation-specific qPCR and Illumina 450K methylation microarray data. SLC18A2 transcript levels were assessed in 412 malignant and 45 benign RP samples using RNAseq data. SLC18A2 protein was evaluated by immunohistochemistry in 502 malignant and 305 benign RP samples. Cancer-specificity of molecular changes was tested using Mann-Whitney U tests and/or receiver operating characteristic (ROC) analyses. Log rank, uni- and multivariate Cox regression tests were used for survival analyses. We found that SLC18A2 promoter hypermethylation was highly cancer-specific (area under the curve (AUC): 0.923-0.976) and associated with biochemical recurrence (BCR) after RP in univariate analyses. SLC18A2 transcript levels were reduced in PC and had independent prognostic value for BCR after RP (multivariate HR 0.13, P < 0.05). Likewise, SLC18A2 protein was down-regulated in PC (AUC 0.898) and had independent prognostic value for BCR (multivariate HR 0.51, P < 0.05). Reduced SLC18A2 protein expression was also associated with poor overall survival in univariate analysis (HR 0.29, P < 0.05). Our results highlight SLC18A2 as a new promising methylation marker candidate for PC diagnosis. Furthermore, SLC18A2 expression (RNA and protein) showed promising prognostic potential beyond routine clinicopathological variables. Thus, novel SLC18A2-based molecular tests could have useful future applications for PC detection and identification of high-risk patients.

Expression of the transcription factor PITX2 in ameloblastic carcinoma

Ameloblastic carcinoma is a rare odontogenic tumour that combines the histological features of ameloblastoma with cytological atypia. Until 2005, the incidence of ameloblastic carcinoma was unknown, and since then, fewer than 60 cases have been reported. These tumours may originate from pre-existing tumours or cysts, or they arise de novo from the activation or transformation of embryological cells. PITX2 is a transcription factor that is a product and regulator of the WNT cell signalling pathway, which has been involved in development of several tumours. To analyse whether PITX2 could be involved in the biological behaviour of ameloblastic carcinoma, we analysed the expression of this transcription factor in a sample of this tumour and nine benign ameloblastomas to compare. The results of Western blotting and RT-PCR analyses were positive, and considering the hundreds of genes that PITX2 regulates, we believe that its expression could be intimately linked to the behaviour of ameloblastic carcinoma and possibly other odontogenic lesions.

Evaluation of ZAR1 and SFRP4 methylation status as potentials biomarkers for diagnosis in cervical cancer: exploratory study phase I

CONTEXT

Aberrant hypermethylation of promoter region of tumor suppressor genes could be used as cancer biomarkers.

OBJECTIVE

To test methylation status of ZAR1 and SFRP4 promoter regions as potentials biomarkers for diagnosis of preneoplastic and neoplastic lesions of cervix.

MATERIALS AND METHODS

Cytobrush samples were evaluated by Methylation specific PCR (MSP) and quantitative MSP (qMSP).

RESULTS

ZAR1 and SFRP4 methylation frequency increased as the grade of lesion increased and the differences between normal and cervical cancer (CC) are statistically significant (p < 0.0001). qMSP showed higher ZAR1 and SFRP4 methylation levels in cancer than normal epithelia (p < 0.001) and preneoplastics lesions (p < 0.01).

DISCUSSION

qMSP quantify methylation levels and have high sensitivity and specificity.

CONCLUSION

ZAR1 and SFRP4 qMSP could be used as potential biomarker for CC diagnosis.

Prognostic DNA methylation markers for prostate cancer

Prostate cancer (PC) is the most commonly diagnosed neoplasm and the third most common cause of cancer-related death amongst men in the Western world. PC is a clinically highly heterogeneous disease, and distinction between aggressive and indolent disease is a major challenge for the management of PC. Currently, no biomarkers or prognostic tools are able to accurately predict tumor progression at the time of diagnosis. Thus, improved biomarkers for PC prognosis are urgently needed. This review focuses on the prognostic potential of DNA methylation biomarkers for PC. Epigenetic changes are hallmarks of PC and associated with malignant initiation as well as tumor progression. Moreover, DNA methylation is the most frequently studied epigenetic alteration in PC, and the prognostic potential of DNA methylation markers for PC has been demonstrated in multiple studies. The most promising methylation marker candidates identified so far include PITX2, C1orf114 (CCDC181) and the GABRE~miR-452~miR-224 locus, in addition to the three-gene signature AOX1/C1orf114/HAPLN3. Several other biomarker candidates have also been investigated, but with less stringent clinical validation and/or conflicting evidence regarding their possible prognostic value available at this time. Here, we review the current evidence for the prognostic potential of DNA methylation markers in PC.

Performance evaluation of kits for bisulfite-conversion of DNA from tissues, cell lines, FFPE tissues, aspirates, lavages, effusions, plasma, serum, and urine

DNA methylation analyses usually require a preceding bisulfite conversion of the DNA. The choice of an appropriate kit for a specific application should be based on the specific performance requirements with regard to the respective sample material. In this study, the performance of nine kits was evaluated: EpiTect Fast FFPE Bisulfite Kit, EpiTect Bisulfite Kit, EpiTect Fast DNA Bisulfite Kit (Qiagen), EZ DNA Methylation-Gold Kit, EZ DNA Methylation-Direct Kit, EZ DNA Methylation-Lightning Kit (Zymo Research), innuCONVERT Bisulfite All-In-One Kit, innuCONVERT Bisulfite Basic Kit, innuCONVERT Bisulfite Body Fluids Kit (Analytik Jena). The kit performance was compared with regard to DNA yield, DNA degradation, DNA purity, conversion efficiency, stability and handling using qPCR, UV, clone sequencing, HPLC, and agarose gel electrophoresis. All kits yielded highly pure DNA suitable for PCR analyses without PCR inhibition. Significantly higher yields were obtained when using the EZ DNA Methylation-Gold Kit and the innuCONVERT Bisulfite kits. Conversion efficiency ranged from 98.7% (EpiTect Bisulfite Kit) to 99.9% (EZ DNA Methylation-Direct Kit). The inappropriate conversion of methylated cytosines to thymines varied between 0.9% (innuCONVERT Bisulfite kits) and 2.7% (EZ DNA Methylation-Direct Kit). Time-to-result ranged from 131 min (innuCONVERT kits) to 402 min (EpiTect Bisulfite Kit). Hands-on-time was between 66 min (EZ DNA Methylation-Lightning Kit) and 104 min (EpiTect Fast FFPE and Fast DNA Bisulfite kits). Highest yields from formalin-fixed and paraffin-embedded (FFPE) tissue sections without prior extraction were obtained using the innuCONVERT Bisulfite All-In-One Kit while the EZ DNA Methylation-Direct Kit yielded DNA with only low PCR-amplifiability. The innuCONVERT Bisulfite All-In-One Kit exhibited the highest versatility regarding different input sample materials (extracted DNA, tissue, FFPE tissue, cell lines, urine sediment, and cellular fractions of bronchial aspirates, pleural effusions, ascites). The innuCONVERT Bisulfite Body Fluids Kit allowed for the analysis of 3 ml plasma, serum, ascites, pleural effusions and urine.

Development and clinical validation of a real-time PCR assay for PITX2 DNA methylation to predict prostate-specific antigen recurrence in prostate cancer patients following radical prostatectomy

Prostate cancer is the most common cancer among men. The prospective discrimination of aggressive and clinically insignificant tumors still poses a significant and, as yet, unsolved problem. PITX2 DNA methylation is a strong prognostic biomarker in prostate cancer. Recently, a diagnostic microarray for prostate cancer prognosis based on PITX2 methylation has been developed and validated. Because this microarray requires nonstandard laboratory equipment, its use in a diagnostic setting is limited. This study aimed to develop and validate an alternative quantitative real-time PCR assay for measuring PITX2 methylation that can easily be established in clinical laboratories, thereby facilitating the implementation of this biomarker in clinical practice. A methylation cut-off for patient stratification was established in a training cohort (n = 157) and validated in an independent test set (n = 523) of men treated with radical prostatectomy. In univariate Cox proportional hazards analysis, PITX2 hypermethylation was a significant predictor for biochemical recurrence (P < 0.001, hazard ratio = 2.614). Moreover, PITX2 hypermethylation added significant prognostic information (P = 0.003, hazard ratio = 1.814) to the Gleason score, pathological T stage, prostate-specific antigen, and surgical margins in a multivariate analysis. The clinical performance was particularly high in patients at intermediate risk (Gleason score of 7) and in samples containing high tumor cell content. This assay might aid in risk stratification and support the decision-making process when determining whether a patient might benefit from adjuvant treatment after radical prostatectomy.

DNA methylation of the homeobox genes PITX2 and SHOX2 predicts outcome in non-small-cell lung cancer patients

Biomarkers that facilitate prediction of disease progression in lung cancer patients might be clinically valuable in optimizing individualized therapy. In this study, the ability of the DNA methylation biomarkers PITX2 and SHOX2 to predict disease outcome in lung cancer patients has been evaluated. Quantitative, methylation-specific (HeavyMethyl), real-time polymerase chain reaction assays were used to measure DNA methylation of PITX2 and SHOX2 in bisulfite-converted DNA from formalin-fixed, paraffin-embedded tissues from 474 non-small-cell lung cancer patients. In univariate Cox Proportional Hazard analysis, high methylation of SHOX2 and PITX2 was a significant predictor of progression-free survival [SHOX2: n=465, hazard ratio (HR)=1.395 (1.130 to 1.721), P=0.002; PITX2: n=445, HR=1.312 (1.059 to 1.625), P=0.013]. Patients with low methylation of either PITX2 and/or SHOX2 (n=319) showed a significantly higher risk of disease progression as compared with patients with higher methylation of both genes [n=126; HR=1.555 (1.210 to 1.999), P=0.001]. This was particularly true for the subgroup of patients receiving no adjuvant radiotherapy or chemotherapy [n=258, HR=1.838 (1.252 to 2.698), P=0.002]. In multivariate analysis, both biomarkers added significant independent prognostic information to pT, pN, pM, and grade. Another interesting finding of this study was that SHOX2 and PITX2 DNA methylation was shown to be inversely correlated with TTF1 (also known as NKX2-1) expression (PITX2: P=0.018, SHOX2: P<0.001). TFF1 expression was previously found to be associated with improved survival in the same patient cohort. DNA methylation of PITX2 and SHOX2 is an independent prognostic biomarker for disease progression in non-small-cell lung cancer patients.

DNA methylation changes in prostate cancer

Epigenetic alterations contribute significantly to the development and progression of prostate cancer, the most prevalent malignant tumor in males of Western industrialized countries. Here, we review recent research on DNA methylation alterations in this cancer type. Hypermethylation of several genes including GSTP1 is well known to occur in a consistent and apparently coordinate fashion during the transition from intraepithelial neoplasia to frank carcinoma. These hypermethylation events have shown promise as biomarkers for detection of prostate carcinoma. Many other individual genes have been shown to undergo hypermethylation, which is typically associated with diminished expression. These investigations indicate additional candidates for biomarkers; in particular, hypermethylation events associated with progression can be employed to identify more aggressive cases. In addition, some of genes silenced by aberrant methylation in prostate have been shown to exhibit properties of tumor suppressors, revealing insights into mechanisms of carcinogenesis. Whereas most studies in the past have used candidate gene approaches, new techniques allowing genome-wide screening for altered methylation are increasingly employed in prostate cancer research and have already yielded encouraging results.

Biomarkers in prostate cancer epidemiology

Understanding the etiology of a disease such as prostate cancer may help in identifying populations at high risk, timely intervention of the disease, and proper treatment. Biomarkers, along with exposure history and clinical data, are useful tools to achieve these goals. Individual risk and population incidence of prostate cancer result from the intervention of genetic susceptibility and exposure. Biochemical, epigenetic, genetic, and imaging biomarkers are used to identify people at high risk for developing prostate cancer. In cancer epidemiology, epigenetic biomarkers offer advantages over other types of biomarkers because they are expressed against a person's genetic background and environmental exposure, and because abnormal events occur early in cancer development, which includes several epigenetic alterations in cancer cells. This article describes different biomarkers that have potential use in studying the epidemiology of prostate cancer. We also discuss the characteristics of an ideal biomarker for prostate cancer, and technologies utilized for biomarker assays. Among epigenetic biomarkers, most reports indicate GSTP1 hypermethylation as the diagnostic marker for prostate cancer; however, NKX2-5, CLSTN1, SPOCK2, SLC16A12, DPYS, and NSE1 also have been reported to be regulated by methylation mechanisms in prostate cancer. Current challenges in utilization of biomarkers in prostate cancer diagnosis and epidemiologic studies and potential solutions also are discussed.

Multicenter clinical validation of PITX2 methylation as a prostate specific antigen recurrence predictor in patients with post-radical prostatectomy prostate cancer

PURPOSE

Radical prostatectomy is potentially curative in patients with clinically localized prostate cancer. However, biochemical recurrence affects 15% to 30% of men who undergo radical prostatectomy. We previously reported the prognostic potential of PITX2 gene promoter methylation using conventional assays. In the current study we validated PITX2 methylation status as a biochemical recurrence predictor after radical prostatectomy using a novel microarray based platform in a multi-institutional setting.

MATERIALS AND METHODS

PITX2 methylation status was assessed in formalin fixed, paraffin embedded prostatectomy tumor tissue samples from 476 patients from a total of 4 institutions on customized EpiChip PITX2 microarrays. Associations between PITX2 methylation and biochemical recurrence were assessed using the log rank test and Cox regression controlling for prostate cancer features.

RESULTS

On multivariate analysis men with high methylation status were at significantly higher risk for biochemical recurrence than those with low methylation status (HR 3.0, 95% CI 2.0-4.5, p <10(-5)). The biochemical recurrence-free survival rate 5 years after surgery was 85% and 61% in the low and high methylation groups, respectively. In men with pathological Gleason 7 tumors the relative risk of biochemical recurrence was twice as high for high than for low PITX2 methylation (HR 2.0, 95% CI 1.2-3.3, p = 0.005).

CONCLUSIONS

PITX2 methylation status assessed by EpiChip PITX2 identifies patients with prostate cancer who are most likely to have biochemical recurrence. This test independently adds to the prognostic information provided by standard clinicopathological analysis, improving prostatectomy case stratification into those at high and low risk for biochemical recurrence. This new clinical tool would be of particular benefit to assess intermediate risk cases (Gleason 7) in which risk stratification remains a challenge.