Aberrant GSTP1 promoter methylation is associated with increased risk and advanced stage of breast cancer: a meta-analysis of 19 case-control studies

Sources of gene expression variation in a globally diverse human cohort

Genetic variation that influences gene expression and splicing is a key source of phenotypic diversity1-5. Although invaluable, studies investigating these links in humans have been strongly biased towards participants of European ancestries, which constrains generalizability and hinders evolutionary research. Here to address these limitations, we developed MAGE, an open-access RNA sequencing dataset of lymphoblastoid cell lines from 731 individuals from the 1000 Genomes Project6, spread across 5 continental groups and 26 populations. Most variation in gene expression (92%) and splicing (95%) was distributed within versus between populations, which mirrored the variation in DNA sequence. We mapped associations between genetic variants and expression and splicing of nearby genes (cis-expression quantitative trait loci (eQTLs) and cis-splicing QTLs (sQTLs), respectively). We identified more than 15,000 putatively causal eQTLs and more than 16,000 putatively causal sQTLs that are enriched for relevant epigenomic signatures. These include 1,310 eQTLs and 1,657 sQTLs that are largely private to underrepresented populations. Our data further indicate that the magnitude and direction of causal eQTL effects are highly consistent across populations. Moreover, the apparent 'population-specific' effects observed in previous studies were largely driven by low resolution or additional independent eQTLs of the same genes that were not detected. Together, our study expands our understanding of human gene expression diversity and provides an inclusive resource for studying the evolution and function of human genomes.

ABERRANT METHYLATION OF CANCER-RELATED GENES IN VIETNAMESE BREAST CANCER PATIENTS: ASSOCIATIONS WITH CLINICOPATHOLOGICAL FEATURES

BACKGROUND

Epigenetic alteration is one of the most common molecular changes identified in the progression of breast cancer (BC).

AIM

To study the frequency and relation between methylation of BRCA1, MLH1, MGMT, GSTP1, APC, RASSF1A, p16, WIF, and EGFR and the clinicopathological features in Vietnamese BC patients.

MATERIALS AND METHODS

Methylation-specific polymerase chain reaction (MS-PCR) and SPSS 20.0 software were utilized in order to identify methylated frequency as well as evaluate its relationship with the patient's clinical features.

RESULTS

In 162 BC cases, the methylation rates of the selected genes were 53.7%, 22.8%, 38.9%, 34.6%, 29.0%, 46.3%, 20.4%, 18.5%, and 28.4% respectively. In 32 cases of benign breast diseases (BBD) - 12.5%, 15.6%, 6.3%, 3.1%, 12.5%, 21.9%, 3.1%, 15.6% and 3.1%. BC samples displayed higher BRCA1, MGMT, GSTP1, APC, RASSF1A, WIF1, and p16 methylation levels than BBD samples (p < 0.001). Hypermethylation of BRCA1, GSTP1, and RASSF1A was predominant in the invasive ductal carcinoma, while hypermethylation of BRCA1, GSTP1, RASSF1A, WIF-1, and p16 was found to significantly correlate with lymph node metastasis (p < 0.05). Hypermethylation of BRCA1, MGMT, and GSTP1 was more common in stage III (p < 0.05) than in stages I/II, whereas MLH1 methylation was predominant in stage I and APC methylation was less common in stage III (p = 0.03). In addition, methylation of RASSF1A and EGFR was more frequent in younger patients (p < 0.01) than in elder patients.

CONCLUSION

These data suggest that a gene panel (BRCA1/MGMT/GSTP1) can be used to support the diagnosis and screening of Vietnamese patients' BC with a sensitivity of 70%, and a specificity of 85%.

Genetic association between rs1695 in glutathione S-transferase P1 and risk of periodontitis: a pilot study

The present study aims to determine the association between a genetic polymorphism of GSTP1 (rs1695) and the risk of periodontitis. This study used a cross-sectional design and included subjects from the South Indian population. A total of 100 individuals enrolled at Saveetha Dental College and Hospital, Tamil Nadu were included in this study. The participants were divided into control (n=50) and periodontitis (n=50) based on clinical examination. Blood samples were collected. Genotyping was performed using specific primers spanning the polymorphic site. The genotypic frequencies for the rs1695 polymorphism were not significantly different between cases and controls.

Methylation profiles of global LINE-1 DNA and the GSTP1 promoter region in children exposed to lead (Pb)

Lead (Pb) exposure has adverse health effects and altered DNA methylation may contribute to Pb toxicity. LINE-1 is an interspersed repeated DNA that is used as a surrogate marker for estimating genomic DNA methylation levels, and GSTP1 is an isozyme that detoxifies xenobiotics like Pb, and its expression is inhibited by methylation. Thus, to assess the effects of Pb exposure on global hypomethylation and gene-specific promoter hypermethylation, we examined DNA methylation at LINE-1 repetitive elements and the GSTP1 promoter region. Blood samples were obtained from children (N = 123) living in Pb-polluted areas (as exposed children) and children (N = 63) living in Pb-unpolluted areas (as control children) in Kabwe, Zambia. ICP-MS was used to determine blood lead levels (BLLs), and pyrosequencing and a fluorescence-based polymerase chain reaction assay were used to determine levels of LINE-1 methylation and GSTP1 promoter methylation, respectively. Inverse association was found between BLLs and LINE-1 methylation (β = - 0.046, p = 0.006). The highest quartile of BLL had significant hypomethylation of LINE-1 (p for trend = 0.03), suggesting the higher the BLL, the lower LINE-1 methylation. GSTP1 methylation levels did not differ significantly between the two areas (p = 0.504), nor was it associated with Pb poisoning risk (OR = 1.03, p = 0.476), indicating GSTP1 methylation may not be a reliable biomarker of Pb exposure in healthy people. Therefore, Pb-related health problems could result from global DNA methylation changes due to high BLLs.

Epigenetic Determinants of Racial Disparity in Breast Cancer: Looking beyond Genetic Alterations

Simple Summary

A substantial disparity in breast cancer incidence and mortality exists between African American (AA) and European American (EA) women. However, the basis for these disparities is poorly understood. In this article, we describe that gene–environment interactions mediated through epigenetic modifications may play a significant role in racial disparities in BC incidence and outcomes. Our in silico analyses and an in-depth literature survey suggest that there exists a significant difference in epigenetic patterns between AA and EA women with breast cancer. Herein, we describe the environmental factors that contribute to these epigenetic changes, which may underlie the disparate racial burden in patients with breast cancer. We suggest that AA women with higher basal epigenetic changes, may have higher pre-disposition to cancer onset, and an aggressive disease course. Pre-existing racial differences in epigenetic profiles of breast tissues raises the possibility of examining these profiles for early diagnosis.

Abstract

Breast cancer (BC) is the most commonly diagnosed cancer in women. Despite advancements in BC screening, prevention, and treatment, BC incidence and mortality remain high among African American (AA) women. Compared with European American (EA) women, AA women tend to be diagnosed with more advanced and aggressive tumors and exhibit worse survival outcomes. Most studies investigating the determinants of racial disparities in BC have focused on genetic factors associated with African ancestry. However, various environmental and social stressors over an individual’s life course can also shape racial stratification in BC. These social and environmental exposures result in long-term changes in gene expression mediated by epigenetic mechanisms. Epigenetics is often portrayed as an intersection of socially patterned stress and genetic expression. The enduring nature of epigenetic changes makes them suitable for studying the effects of different environmental exposures over an individual’s life course on gene expression. The role of differential social and environmental exposures in racial disparities in BC suggests varied epigenetic profiles or signatures associated with specific BC subtypes in AA and EA women. These epigenetic profiles in EA and AA women could be used as biomarkers for early BC diagnosis and disease prognosis and may prove valuable for the development of targeted therapies for BC. This review article discusses the current state of knowledge regarding epigenetic differences between AA and EA women with BC. We also discuss the role of socio-environmental factors, including psychosocial stress, environmental toxicants, and dietary factors, in delineating the different epigenetic profiles in AA and EA patients with BC.

Genome-wide aberrant methylation in primary metastatic UM and their matched metastases

Uveal melanoma (UM) is an aggressive intra-ocular cancer with a strong tendency to metastasize. Metastatic UM is associated with mutations in BAP1 and SF3B1, however only little is known about the epigenetic modifications that arise in metastatic UM. In this study we aim to unravel epigenetic changes contributing to UM metastasis using a new genome-wide methylation analysis technique that covers over 50% of all CpG’s. We identified aberrant methylation contributing to BAP1 and SF3B1-mediated UM metastasis. The methylation data was integrated with expression data and surveyed in matched UM metastases from the liver, skin and bone. UM metastases showed no commonly shared novel epigenetic modifications, implying that epigenetic changes contributing to metastatic spreading and colonization in distant tissues occur early in the development of UM and epigenetic changes that occur after metastasis are mainly patient-specific. Our findings reveal a plethora of epigenetic modifications in metastatic UM and its metastases, which could subsequently result in aberrant repression or activation of many tumor-related genes. This observation points towards additional layers of complexity at the level of gene expression regulation, which may explain the low mutational burden of UM.

Estimating DNA methylation potential energy landscapes from nanopore sequencing data

High-throughput third-generation nanopore sequencing devices have enormous potential for simultaneously observing epigenetic modifications in human cells over large regions of the genome. However, signals generated by these devices are subject to considerable noise that can lead to unsatisfactory detection performance and hamper downstream analysis. Here we develop a statistical method, CpelNano, for the quantification and analysis of 5mC methylation landscapes using nanopore data. CpelNano takes into account nanopore noise by means of a hidden Markov model (HMM) in which the true but unknown (“hidden”) methylation state is modeled through an Ising probability distribution that is consistent with methylation means and pairwise correlations, whereas nanopore current signals constitute the observed state. It then estimates the associated methylation potential energy function by employing the expectation-maximization (EM) algorithm and performs differential methylation analysis via permutation-based hypothesis testing. Using simulations and analysis of published data obtained from three human cell lines (GM12878, MCF-10A, and MDA-MB-231), we show that CpelNano can faithfully estimate DNA methylation potential energy landscapes, substantially improving current methods and leading to a powerful tool for the modeling and analysis of epigenetic landscapes using nanopore sequencing data.

Glutathione S transferase T1 gene polymorphism and its promoter methylation are associated with breast cancer susceptibility in Egyptian women

BACKGROUND

Breast cancer (BC) is one of the leading causes of cancer mortality in women. Glutathione S-transferase (GSTT1) is involved in activation of detoxification reactions and catalysis of chemicals conjugation with glutathione. GSTT1 genotype is a limiting factor for some environmental diseases. Epigenetic changes have an essential role in BC through inappropriate interaction between genomic and environmental risk factors.

AIM

This study was directed to explore the association of BC risk with GSTT1 genetic variations and its methylation status in Egyptian women.

DESIGN AND METHODS

This study included 100 healthy women as the control group and 100 patients were clinically and histologically diagnosed with breast cancer. All blood samples were used for genomic DNA extraction. GSTT1 genotyping was accomplished by multiplex PCR and methylation-specific PCR was used to analyze the GSTT1 promoter methylation status.

RESULTS

Breast cancer patients showed significant incidence of null GSTT1 in relation to controls (p = 0.004). GSTT1 gene promoter methylation status showed significant difference between hypermethylated and unmethylated patients when compared with healthy subjects (p = 0.005). GSTT1 promoter methylation status was not significantly associated with null genotype. There was no significant association between GSTT1-null genotypes and BC stage in cases with or without family history, but for promotor methylation, there was significant association with stage III and IV breast cancer disease.

CONCLUSION

GSTT1 null genetic variant and promoter hypermethylation in the GSTT region of the gene may be considered as critical risk factors for BC in Egyptian women.

Epigenetic Regulation of Differentially Expressed Drug-Metabolizing Enzymes in Cancer

Drug metabolism is a biotransformation process of drugs, catalyzed by drug-metabolizing enzymes (DMEs), including phase I DMEs and phase II DMEs. The aberrant expression of DMEs occurs in the different stages of cancer. It can contribute to the development of cancer and lead to individual variations in drug response by affecting the metabolic process of carcinogen and anticancer drugs. Apart from genetic polymorphisms, which we know the most about, current evidence indicates that epigenetic regulation is also central to the expression of DMEs. This review summarizes differentially expressed DMEs in cancer and related epigenetic changes, including DNA methylation, histone modification, and noncoding RNAs. Exploring the epigenetic regulation of differentially expressed DMEs can provide a basis for implementing individualized and rationalized medication. Meanwhile, it can promote the development of new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer. SIGNIFICANCE STATEMENT: This review summarizes the aberrant expression of DMEs in cancer and the related epigenetic regulation of differentially expressed DMEs. Exploring the epigenetic regulatory mechanism of DMEs in cancer can help us to understand the role of DMEs in cancer progression and chemoresistance. Also, it provides a basis for developing new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer.

Promoter methylation and Ile105val polymorphism of GSTP1 gene in the modulation of colorectal cancer risk in ethnic Kashmiri population

BACKGROUND

Glutathione-S-transferases (GSTs) are the most important phase II enzymes of the xenobiotic pathway responsible for the detoxification of carcinogens. GSTP1 gene polymorphisms are mostly associated with a lack or an alteration of enzymatic activity toward several substrates thus resulting in increased cancer susceptibility. GSTP1 promoter methylation is also frequently associated with tumor development or poor prognosis in a wide range of tumors.

AIM

In this study, we examined the role of genetic polymorphism and promoter methylation of GSTP1 gene in the context of modulation of risk of colorectal cancer (CRC) in Kashmiri population.

METHODS

This study used tissue tumor samples (114) and blood samples from (160) patients with CRC and 200 blood samples from healthy donors. GSTP1 polymorphism was studied using polymerase chain reaction (PCR)-restriction fragment length polymorphism and methylation using methylation-specific PCR.

RESULTS

There was no significant association between GSTP1 I105V genotypes and the CRC (P>0.05). However, we found a significant association of the Val/Val variant genotype with the dwelling and smoking status (P-value < 0.05). Overall, the homozygous variant Val/Val genotype was associated with a modestly elevated risk for CRC (OR = 1.57; 95% CI = 0.67-3.57). Methyl-specific-PCR analysis revealed 25.4% methylation of the GSTP1 promoter in CRC cases and was not found to be statistically significantly associated with clinicopathological parameters of the CRC cases (P>0.05). Also, no significant associations of any of the three genotypes with promoter hypermethylation were observed.

CONCLUSION

We conclude that promoter hypermethylation in homozygous GSTP1 mutants did not elevate the risk of CRC in Kashmiri population.

Methylation of Glutathione-S-Transferase P1 Promotor in Egyptian Females with Breast Cancer

Background:

Breast cancer (BC) is the second most common cancer after the lung cancer worldwide and number one killing cancer in Egyptian females . It is a multifactorial disease driven by different environmental, hormonal, genetic and epigenetic factors. Epigenetic alterations have been studied in cancer breast. Role of GSTP1 promotor methylation in breast cancer has been studied in different ethnic groups.

Objectives:

Current study aimed at studying the methylation status of the promotor region of glutathione-S-transferase P1 in breast ductal carcinoma of a cohort group of Egyptian females and its correlations with histopathological and prognostic parameters.

Methods:

Control group included 15 fresh normal breast tissues taken from BC female patients after leaving a clearly defined safety margin and a Patient group included confirmed 35 fresh breast ductal carcinoma tissue biopsies taken from female patients postoperatively. To all patients clinical examination, radiological examination (plain X-ray chest and or CT scan, ultrasonography of abdomen and pelvis were done), in addition to histopathological examination, typing, grading and staging of tumour, hormonal receptors status and molecular typing of breast mass. GSTP1 methylation status was evaluated using methyl specific polymerase chain reaction.

Results:

Statistical significant increase was found in methylation status of GSTP1 promotor gene in BC cases than that in control group, (60% of patients samples had methylated GSTP1 promotor vs only 6.7% of controls) (p= >0.001). No association was found between GSTP1 promotor methylation status and the poor prognostic factors neither with hormonal profile nor molecular type. However, GSTP1 promotor methylation were two times higher in postmenopausal than premenopausal cases and three times higher in late grade (III). Also GSTP1 promotor methylation was 2.4 times higher in Her2 positive cases than either ER or PR positive cases. Conclusion: Glutathione-S-Transferase P1 Promotor methylation plays a role in breast cancer development.

Gene promoter methylation and cancer: An umbrella review

Gene promoter methylation is a common epigenetic event, taking place in the early phase of tumorigenesis, which has a great potential as a diagnostic and prognostic cancer biomarker. In this umbrella review, we provide an overview on the association between gene-promoter methylation of protein-coding genes and cancer risk based on currently available meta-analyses data on gene promoter methylation. We searched MEDLINE via PubMed and the Cochrane Database of Systematic Reviews for meta-analyses that examine the association between gene-promoter methylation and cancer, published until January 2019 in English. We used AMSTAR to assess the quality of the included studies and applied a set of pre-specified criteria to evaluate the magnitude of each association. We provide a comprehensive overview of 80 unique combinations between 22 different genes and 18 cancer outcomes, all of which indicated a positive association between promoter hypermethylation and cancer. In total, the 70 meta-analyses produced significant results under a random-effects model with odds ratios that ranged from 1.94 to 26.60, with the summary effect being in favor of the unmethylated group in all cases. Three of the strong evidence associations involve RASSF1 methylation on bladder cancer risk (OR = 18.46; 95% CI: 12.69-26.85; I² = 0%), MGMT methylation on NSCLC (OR = 4.25; 95% CI: 2.83-6.38; I² = 22.4%) and RARB methylation on prostate cancer (OR = 6.87; 95% CI: 4.68-10.08; I² = 0%). Meta-analyses showed a moderate quality, AMSTAR score ranging from 4 to 9 (Mdn = 8; IQR: 7.0 to 8.0). As primary studies and meta-analyses on the subject accumulate, more genetic loci may be found to be highly associated with specific cancer types and hence the biomarker sets will become wider.

Transcriptional Activation of Gstp1 by MEK/ERK Signaling Confers Chemo-Resistance to Cisplatin in Lung Cancer Stem Cells

Lung cancer management remains a challenge due to its asymptomatic and late presentation when it is metastatic. The clinical response to the first-line platinum-based chemotherapy in patients with advanced lung cancer is disappointing due to the development of chemoresistance. Chemoresistance is a complex phenomenon. Mechanistic research using experimental models has yielded limited clinical results to help increase understanding for overcoming resistance. While the role of lung CSCs in conferring multidrug resistance has been postulated, experimental evidence remains associative and lacks in depth mechanistic inquisition. In the present study, using mouse and human lung adenocarcinoma cell lines and their respective paired CSC derivative cell lines that we generated, we identified cancer stem cell component of lung adenocarcinoma as the source that confers multidrug resistance phenotype. Mechanistically, Gstp1 confers cisplatin resistance in mouse and human lung CSC models, both in vitro and in vivo. Further, transcriptional activation of Gstp1 expression by MEK/ERK signaling underlies cisplatin resistance in lung CSC cells. Moreover, we show that GSTP1 expression is a poor diagnostic and prognostic marker for human lung adenocarcinoma, thus is of high clinical relevance. Taken together, we have provided mechanistic understanding of the lung CSC in mediating chemoresistance.

GSTP1 methylation in cancer: a liquid biopsy biomarker?

The coding region of GSTP1 gene is preceded by a large CpG-rich region that is frequently affected by methylation. In many cancer types, GSTP1 is affected by hypermethylation and, as a consequence, it has a low expression. The aim of this review is to give an overview on GSTP1 methylation studies with a special focus on liquid biopsy, thus to summarize methods, results, sample types, different diseases, to have a complete information regarding this promising epigenetic biomarker. We used all the most valuable scientific search engines (PubMed, Medline, Scopus and Web of Science) searching the following keywords: GSTP1, methylation, cancer, urine, serum, plasma and blood. GSTP1 is a largely investigated tissue biomarker in several malignancies such as prostate, breast, lung and hepatocellular carcinoma with good performances especially for diagnostic purposes. As a liquid biopsy biomarker, it has been mainly investigated in prostate cancer (PCa) where it showed a high specificity but a low sensitivity; thus, it is recommended in combination with other biomarkers. Despite the large number of published papers and the promising results, GSTP1 has not yet entered the clinical practice even for PCa diagnosis. For this reason, further large and prospective studies are needed to validate this assay.

Methylation of CLEC14A is associated with its expression and lung adenocarcinoma progression

Our main objective is probing the effect of methylation of CLEC14A on its expression and lung adenocarcinoma (LUAD) progression. Microarray analysis was utilized to screen out differentially downregulated genes with hypermethylation in LUAD tissues. The CLEC14A expression level was measured by western blot analysis and qRT-PCR. Methylation-specific-PCR was performed to evaluate methylation status of CLEC14A. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromid (MTT) assay was used to check the relation between CLEC14A expression and cell proliferation. Cell cycle, cell apoptosis, migration, and invasion were respectively detected by the flow cytometry assay, wound healing assay, and transwell assay. Tumor xenograft models were established for investigating the effect of CLEC14A on tumor formation. CLEC14A expression in LUAD tissues was impaired compared with that in adjacent tissues, and CLEC14A promoter was highly methylated in LUAD. Overexpressing CLEC14A or inhibiting the methylation level of CLEC14A in A549 and LTEP-a-2 cells impeded the duplication of LUAD cells, promoted apoptosis, attenuated cell migration, and invasion ability, and arrested cell cycle at the G0/G1 phase. Overexpression of CLEC14A inhibited tumorigenesis of LUAD cells in nude mice. The promoter of CLEC14A is methylated in LUAD, leading to downregulation of CLEC14A in LUAD. CLEC14A acts as an antitumor role in LUAD by suppressing cell proliferation, migration, invasion, promoting cell apoptosis, and reducing tumorigenicity in nude mice. Thus, the inhibition of CLEC14A methylation is a novel strategy for the clinic treatment of LUAD.

Evaluation of glutathione S-transferase pi 1 expression and gene promoter methylation in Moroccan patients with urothelial bladder cancer

BACKGROUND

Glutathione S-transferase pi 1 (GSTP1) is a cytosolic detoxifying enzyme that protects cells against deleterious effects of oxidative stress. Deregulated expression of GSTP1 protein and aberrant promoter methylation of GSTP1 gene were reported in various human tumors and were shown to be involved in the molecular pathway for cancer development.

AIMS AND METHODS

In this study, we aimed to determine the expression status of GSTP1 in relation to its gene promoter methylation in Moroccan population of 30 bladder cancer (BC) patients and in two noncancerous bladder tissues used as controls. GSTP1 expression was assessed by immunohistochemistry and GSTP1 gene promoter methylation status was studied by methylation-specific PCR (MS-PCR).

RESULTS

Glutathione S-transferase pi 1 was expressed in the two normal tissues. In BC cases, GSTP1 expression was strong in 23.33% (7/30), moderate in 60% (18/30), and weak in 13.33% (4/30) of cases, while GSTP1 was not expressed in one cancer case (3.33%). Variability of GSTP1 expression does not correlate with high-grade cancer or invasive-stage (p > 0.05). No GSTP1 gene promoter methylation was detected in all control and cancer cases.

CONCLUSION

Our data suggest that GSTP1 expression is not associated with BC development, limiting its use as a biomarker for BC management in Morocco. Moreover, difference in GSTP1 expression among BC cases is not due to GSTP1 promoter methylation.

Methylation Profiles of BRCA1, RASSF1A and GSTP1 in Vietnamese Women with Breast Cancer

Objective: This study investigated the DNA promoter methylation profiles of BRCA1, RASSF1A and GSTP1 genes, both individually and in an integrative manner in order to clarify their correlation with clinicopathological parameters of breast cancer from Vietnamese patients, and establish new potential integrative methylation biomarkers for breast cancer detection. Material and methods: The methylation frequencies of BRCA1, RASSF1A and GSTP1 were analyzed by methylation specific polymerase chain reaction (MSP) in 70 specimens of breast carcinomas and 79 pairs of tumor and matched adjacent normal tissues from breast cancer patients. Results: All the three analyzed genes showed a concordance concerning their promoter methylation in tumor and adjacent normal tissue. The methylation of BRCA1, RASSF1A and GSTP1 was found in 58.23 %, 74.68 % and 59.49 % of tumor tissues and 51.90 %, 63.29 % and 35.44 % of corresponding adjacent tissues, respectively. When each gene was assessed individually, only the methylation of GSTP1 was significantly associated with tumor tissues (p=0.003). However, the methylation frequency of at least one of the three genes and the methylation frequency of all the three genes both showed significant association with tumor (p=0.008 and p=0.04, respectively). The methylation of BRCA1 was found to be significantly associated with tumor grade (p=0.01). Conclusion: This study emphasized that the panel of the three genes BRCA1, RASSF1A and GSTP1 can be further developed as potential biomarkers in diagnosis and classification of breast cancer in Vietnamese women.

Prognostic significance of GSTP1 in patients with triple negative breast cancer

Background

Previous studies showed that glutathione S-transferase Pi 1 (GSTP1) is a critical metabolic driver that is heightened specifically in triple negative breast cancer (TNBC) and drives breast cancer pathogenicity. This study focuses on investigating the relationship between the expression of the GSTP1 protein and TNBC metastasis and prognosis in China.

Results

Chi-square and Fisher's exact tests showed that tumor size (P=0.023) and clinical stage (P=0.049) were significantly associated with GSTP1 expression. Patients with high GSTP1 expression exhibited an improved survival rate compared with patients with low GSTP1 expression, but the difference was not statistically significant (P=0.437). On multivariate analysis, clinical stage proved to be an independent prognostic factor for survival in breast cancer.

Materials and methods

A total of 175 patients with histologically confirmed TNBC, who also underwent radical surgery between January 2008 and November 2011 at the Liaoning Cancer Hospital, were enrolled. Immunohistochemistry was used to detect GSTP1 expression in breast cancer tissue from 175 patients. The correlations between GSTP1 expression and other parameters were evaluated using the Chi-square and Fisher's exact tests. Univariate and multivariate Cox regression analyses were performed to assess independent prognostic factors for survival. Associations of GSTP1 expression with clinical stage and prognosis were analyzed using Kaplan–Meier survival curves.

Conclusions

Tumors with high GSTP1 protein expression were independently associated with low clinical stages in TNBC patients in China. The expression of the GSTP1 protein may be a novel prognosis marker for TNBC patients in China.

DNA methylation profiles in cancer diagnosis and therapeutics

Cancer initiation and proliferation is regulated by both epigenetic and genetic events with epigenetic modifications being increasingly identified as important targets for cancer research. DNA methylation catalyzed by DNA methyltransferases (DNMTs) is one of the essential epigenetic mechanisms that control cell proliferation, apoptosis, differentiation, cell cycle, and transformation in eukaryotes. Recent progress in epigenetics revealed a deeper understanding of the mechanisms of tumorigenesis and provided biomarkers for early detection, diagnosis, and prognosis in cancer patients. Although DNA methylation biomarker possesses potential contributing to precision medicine, there are still limitations to be overcome before it reaches clinical setting. Hence, the current status of DNA methylation biomarkers was reviewed and the future use in clinic was also predicted.

Methylation of kruppel-like factor 2 (KLF2) associates with its expression and non-small cell lung cancer progression

Kruppel-like factor 2 (KLF2) is a putative tumor suppressor gene. This study investigated its role and epigenetic mechanisms in human non-small cell lung cancer (NSCLC) in ex vivo and in vitro. A total of 47 paired NSCLC and normal tissues and six cell lines were analyzed using qRT-PCR for KLF2 expression. KLF2 methylation was assessed using the methylation specific PCR (MSP) or bisulfite sequencing PCR (BSP). Functional KLF2 region 4 (+567 to +906) was confirmed using the dual-luciferase reporter assay, while CCK-8 cell viability and flow cytometric assays were used to assess changes in cell viability, cell cycle distribution, and apoptosis after knockdown or re-expression of KLF2. Western blot was performed to analyze the effects of KLF2 shRNA on knockdown of KLF2 expression and p15 and p21 expression in cells. We found that KLF2 expression was significantly reduced in NSCLC cells and tissues via KLF2 methylation. Reduction of KLF2 expression was associated with KLF2 region 4 hypermethylation in 27 of 47 (57.45%) NSCLC tissues. Furthermore, methylation at KLF2 region 4 was significantly associated with lymph node metastasis and advanced TNM stage. Re-expression of KLF2 suppressed NSCLC cell viability, arrested cells at G0/G1 cell cycle by induction of p15 and p21 expression, and promoted apoptosis, whereas knockdown of KLF2 expression had the opposite effects on cells. Taken together, KLF2 possesses tumor suppressor functions in NSCLC and detection of KLF2 methylation should be further evaluated as a tumor or prognostic biomarker for NSCLC.

CHL1 hypermethylation as a potential biomarker of poor prognosis in breast cancer

The CHL1 gene encodes a cell-adhesion molecule proposed as being a putative tumour-suppressor gene in breast cancer (BC). However, neither the underlying molecular mechanisms nor the clinical value of CHL1 downregulation in BC has been explored. The methylation status of three CpG sites in the CHL1 promoter was analysed by pyrosequencing in neoplastic biopsies from 142 patients with invasive BC and compared with that of non-neoplastic tissues. We found higher CHL1 methylation levels in breast tumours than in non-neoplastic tissues, either from mammoplasties or adjacent-to-tumour, which correlated with lower levels of protein expression in tumours measured by immunohistochemistry. A panel of five BC cell lines was treated with two epigenetic drugs, and restoration of CHL1 expression was observed, indicating in vitro dynamic epigenetic regulation. CHL1 was silenced by shRNA in immortalized but non-neoplastic mammary cells, and enhanced cell proliferation and migration, but not invasion, were found by real-time cell analysis. The prognostic value of CHL1 hypermethylation was assessed by the log-rank test and fitted in a Cox regression model. Importantly, CHL1 hypermethylation was very significantly associated with shorter progression-free survival in our BC patient series, independent of age and stage (p = 0.001). In conclusion, our results indicate that CHL1 is downregulated by hypermethylation and that this epigenetic alteration is an independent prognostic factor in BC.

CDH22 hypermethylation is an independent prognostic biomarker in breast cancer

BACKGROUND

Cadherin-like protein 22 (CDH22) is a transmembrane glycoprotein involved in cell-cell adhesion and metastasis. Its role in cancer is controversial because it has been described as being upregulated in colorectal cancer, whereas it is downregulated in metastatic melanoma. However, its status in breast cancer (BC) is unknown. The purpose of our study was to determine the molecular status and clinical value of CDH22 in BC.

RESULTS

We observed by immunohistochemistry that the level of CDH22 expression was lower in BC tissues than in their matched adjacent-to-tumour and non-neoplastic tissues from reduction mammoplasties. Since epigenetic alteration is one of the main causes of gene silencing, we analysed the hypermethylation of 3 CpG sites in the CDH22 promoter by pyrosequencing in a series of 142 infiltrating duct BC cases. CDH22 was found to be hypermethylated in tumoral tissues relative to non-neoplastic mammary tissues. Importantly, this epigenetic alteration was already present in adjacent-to-tumour tissues, although to a lesser extent than in tumoral samples. Furthermore, CDH22 gene regulation was dynamically modulated in vitro by epigenetic drugs. Interestingly, CDH22 hypermethylation in all 3 CpG sites simultaneously, but not expression, was significantly associated with shorter progression-free survival (p = 0.015) and overall survival (p = 0.021) in our patient series. Importantly, CDH22 hypermethylation was an independent factor that predicts poor progression-free survival regardless of age and stage (p = 0.006).

CONCLUSIONS

Our results are the first evidence that CDH22 is hypermethylated in BC and that this alteration is an independent prognostic factor in BC. Thus, CDH22 hypermethylation could be a potential biomarker of poor prognosis in BC.

GSTP1 Methylation and Protein Expression in Prostate Cancer: Diagnostic Implications

GSTP1 belongs to the GSTs family, a group of enzymes involved in detoxification of exogenous substances and it also plays an important role in cell cycle regulation. Its dysregulation correlates with a large variety of tumors, in particular with prostate cancer. We investigated GSTP1 methylation status with methylation specific PCR (MS-PCR) in prostate cancer (PCa) and in benign tissue of 56 prostatectomies. We also performed immunohistochemistry (IHC) so as to correlate gene methylation with gene silencing. GSTP1 appears methylated in PCa and not in healthy tissue; IHC confirmed that methylation leads to protein underexpression (p < 0.001). GSTP1 is highly expressed in basal cell layer and luminal cells in benign glands while in prostatic intraepithelial neoplasia (PIN) it stains only basal cell layer, whereas PCa glands are completely negative. We demonstrated that methylation leads to underexpression of GSTP1. The progressive loss of GSTP1 expression from healthy glands to PIN and to PCa glands underlines its involvement in early carcinogenesis.