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

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ABSTRACT

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.

No MeSH data available.


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PITX3 DNA methylation in prostatectomy specimens. Median methylation is indicated by the gray line. PITX3 DNA methylation is significantly higher in prostate cancer (PCa) tissue compared to corresponding normal adjacent tissue (NAT) and benign prostatic hyperplasia (BPH). a NAT and PCa samples of the training cohort (TCGA). p values refer to Wilcoxon-Mann-Whitney test. b NAT, BPH, and PCa samples from a test study comprising 71 patient samples. Each sample was measured in triplicate. p values refer to Kruskal-Wallis test
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Fig2: PITX3 DNA methylation in prostatectomy specimens. Median methylation is indicated by the gray line. PITX3 DNA methylation is significantly higher in prostate cancer (PCa) tissue compared to corresponding normal adjacent tissue (NAT) and benign prostatic hyperplasia (BPH). a NAT and PCa samples of the training cohort (TCGA). p values refer to Wilcoxon-Mann-Whitney test. b NAT, BPH, and PCa samples from a test study comprising 71 patient samples. Each sample was measured in triplicate. p values refer to Kruskal-Wallis test

Mentions: For the analysis of PITX3 promoter methylation (mPITX3) in the training cohort, results obtained from two Illumina Infinium HumanMethylation450 BeadChip beads from the TCGA dataset (cg12324970 and cg23095743) were used. Both beads were located within the CpG island of PITX3 (Fig. 1a). Firstly, PCa (n = 498) and normal adjacent tissue (NAT, n = 50) samples from the training cohort were analyzed with respect to mPITX3. Patient samples showed a significantly lower level of mPITX3 in NAT compared to PCa samples (p < 0.001, Fig. 2a). A histogram of mPITX3 showed a bell curve with a minor depression at ≈68 % (Fig. 3a). mPITX3 levels as a continuous variable were related to prognostic clinicopathological variables and were found to be significantly correlated with the ISUP Gleason grading group (ρ = 0.112; p = 0.012), pathologic tumor (pT) category (ρ = 0.123; p = 0.006), presurgical PSA (ρ = 0.134; p = 0.003), and the AR activity score (ρ = 0.154; p = 0.005) as obtained from TCGA [27] in the training cohort. In order to analyze the suitability of mPITX3 for the stratification of patients at risk for biochemical recurrence (BCR), mPITX3 was dichotomized by an optimized cutoff (mPITX3low < 68.2 % ≤ mPITX3high; Table 1) which was identified by an iterative approach. In the training cohort, mPITX3high was significantly associated with BCR in the univariate Cox proportional hazards model (hazard ratio (HR) = 1.83 (95 % CI 1.07–3.11); p = 0.027; (Table 2)) and the Kaplan-Meier analysis (likelihood ratio (LR) = 5.05; p = 0.025, Fig. 3b).Fig. 1


PITX3 promoter methylation is a prognostic biomarker for biochemical recurrence-free survival in prostate cancer patients after radical prostatectomy
PITX3 DNA methylation in prostatectomy specimens. Median methylation is indicated by the gray line. PITX3 DNA methylation is significantly higher in prostate cancer (PCa) tissue compared to corresponding normal adjacent tissue (NAT) and benign prostatic hyperplasia (BPH). a NAT and PCa samples of the training cohort (TCGA). p values refer to Wilcoxon-Mann-Whitney test. b NAT, BPH, and PCa samples from a test study comprising 71 patient samples. Each sample was measured in triplicate. p values refer to Kruskal-Wallis test
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Related In: Results  -  Collection

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Fig2: PITX3 DNA methylation in prostatectomy specimens. Median methylation is indicated by the gray line. PITX3 DNA methylation is significantly higher in prostate cancer (PCa) tissue compared to corresponding normal adjacent tissue (NAT) and benign prostatic hyperplasia (BPH). a NAT and PCa samples of the training cohort (TCGA). p values refer to Wilcoxon-Mann-Whitney test. b NAT, BPH, and PCa samples from a test study comprising 71 patient samples. Each sample was measured in triplicate. p values refer to Kruskal-Wallis test
Mentions: For the analysis of PITX3 promoter methylation (mPITX3) in the training cohort, results obtained from two Illumina Infinium HumanMethylation450 BeadChip beads from the TCGA dataset (cg12324970 and cg23095743) were used. Both beads were located within the CpG island of PITX3 (Fig. 1a). Firstly, PCa (n = 498) and normal adjacent tissue (NAT, n = 50) samples from the training cohort were analyzed with respect to mPITX3. Patient samples showed a significantly lower level of mPITX3 in NAT compared to PCa samples (p < 0.001, Fig. 2a). A histogram of mPITX3 showed a bell curve with a minor depression at ≈68 % (Fig. 3a). mPITX3 levels as a continuous variable were related to prognostic clinicopathological variables and were found to be significantly correlated with the ISUP Gleason grading group (ρ = 0.112; p = 0.012), pathologic tumor (pT) category (ρ = 0.123; p = 0.006), presurgical PSA (ρ = 0.134; p = 0.003), and the AR activity score (ρ = 0.154; p = 0.005) as obtained from TCGA [27] in the training cohort. In order to analyze the suitability of mPITX3 for the stratification of patients at risk for biochemical recurrence (BCR), mPITX3 was dichotomized by an optimized cutoff (mPITX3low < 68.2 % ≤ mPITX3high; Table 1) which was identified by an iterative approach. In the training cohort, mPITX3high was significantly associated with BCR in the univariate Cox proportional hazards model (hazard ratio (HR) = 1.83 (95 % CI 1.07–3.11); p = 0.027; (Table 2)) and the Kaplan-Meier analysis (likelihood ratio (LR) = 5.05; p = 0.025, Fig. 3b).Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

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&thinsp;=&thinsp;498) from the TCGA and an independent validation cohort (n&thinsp;=&thinsp;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)&thinsp;=&thinsp;1.83 (95&nbsp;% CI 1.07&ndash;3.11), p&thinsp;=&thinsp;0.027; validation cohort: HR&thinsp;=&thinsp;2.56 (95&nbsp;% CI 1.44&ndash;4.54), p&thinsp;=&thinsp;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.

No MeSH data available.


Related in: MedlinePlus