Expression level and DNA methylation status of glutathione-S-transferase genes in normal murine prostate and TRAMP tumors

Prognostic biomarker GSTK1 in head and neck squamous cell carcinoma and its correlation with immune infiltration and DNA methylation

Background: Glutathione S-transferase kappa 1 (GSTK1) is critical in sarcoma and breast cancer (BRCA) development. However, the clinical significance of GSTK1 in head and neck squamous cell carcinoma (HNSC) remains unclear. This study is the first investigation into the role of GSTK1 in HNSC. Methods: All original data were downloaded from the Cancer Genome Atlas (TCGA) dataset and verified by R Base Package 4.2.0. The expression of GSTK1 in various cancers was explored with TIMER and TCGA databases. Prognostic value of GSTK1 was analyzed via survival module of Kaplan-Meier plotter and Human Protein Atlas database and Cox regression analysis. The association between GSTK1 and clinical features was evaluated by Wilcoxon signed-rank test and logistic regression analysis. The relationship between GSTK1 and immune infiltration and methylation level was further explored. The expression of GSTK1 and its correlation with immune cell infiltration was verified by Immunohistochemical staining (IHC). Results: GSTK1 was lower in HNSC, BRCA, Lung squamous cell carcinoma, and Thyroid carcinoma than in para-carcinoma. Low GSTK1 expression was associated with worse overall survival in Bladder urothelial carcinoma, Kidney renal papillary cell carcinoma, BRCA, and HNSC. However, only in BRCA and HNSC, GSTK1 expression in tumors was lower than that in normal tissues. Cox regression analyses confirmed that GSKT1 was an independent prognostic factor of overall survival in HNSC patients. The decrease in GSTK1 expression in HNSC was significantly correlated with high T stage and smoker history. IHC showed that the expression level of GSTK1 in HNSC was lower than that in para-carcinoma. In addition, GSEA showed that three pathways related to immune infiltration were positively correlated, while two pathways related to DNA methylation were negatively correlated with expression of GSTK1. Further analysis showed that GSTK1 was moderately positively correlated with the infiltration level of T cells and Cytotoxic cells, which was further confirmed by IHC. The methylation level of GSTK1 was associated with prognosis in patients with HNSC. Conclusion: Low GSTK1 expression may be a potential molecular marker for poor prognosis in HNSC and provide new insight for the development of diagnostic marker or therapeutic target.

Crossbred Sows Fed a Western Diet during Pre-Gestation, Gestation, Lactation, and Post-Lactation Periods Develop Signs of Lean Metabolic Syndrome That Are Partially Attenuated by Spirulina Supplementation

Excessive dietary intake of fats and sugars (“Western diet”, WD) is one of the leading causes of obesity. The consumption of the microalga Arthrospira platensis (spirulina, Sp) is increasing due to its presumed health benefits. Both WD and Sp are also consumed by pregnant and breastfeeding women. This study investigated if gestating and lactating domestic pigs are an appropriate model for WD-induced metabolic disturbances similar to those observed in humans and if Sp supplementation may attenuate any of these adverse effects. Pigs were fed a WD high in fat, sugars, and cholesterol or a control diet. Half of the animals per diet group were supplemented with 20 g Sp per day. The WD did not increase body weight or adipose tissue accumulation but led to metabolic impairments such as higher cholesterol concentration in plasma, lower IGF1 plasma levels, and signs of hepatic damage compared to the control group. Spirulina supplementation could not reduce all the metabolic impairments observed in WD-fed animals. These findings indicate limited suitability of gestating and lactating domestic pigs as a model for WD but a certain potential of low-dose Sp supplementation to partially attenuate negative WD effects.

Polymorphisms in Genes Encoding Glutathione Transferase Pi and Glutathione Transferase Omega Influence Prostate Cancer Risk and Prognosis

Considering the pleiotropic roles of glutathione transferase (GST) omega class members in redox homeostasis, we hypothesized that polymorphisms in GSTO1 and GSTO2 might contribute to prostate cancer (PC) development and progression. Therefore, we performed a comprehensive analysis of GSTO1 and GSTO2 SNPs' role in susceptibility to PC, as well as whether they might serve as prognostic biomarkers independently or in conjunction with other common GST polymorphisms (GSTM1, GSTT1, and GSTP1). Genotyping was performed in 237 PC cases and 236 age-matched controls by multiplex PCR for deletion of GST polymorphisms and quantitative PCR for SNPs. The results of this study, for the first time, demonstrated that homozygous carriers of both GSTO1*A/A and GSTO2*G/G variant genotypes are at increased risk of PC. This was further confirmed by haplotype analysis, which showed that H2 comprising both GSTO1*A and GSTO2*G variant alleles represented a high-risk combination. However, the prognostic relevance of polymorphisms in GST omega genes was not found in our cohort of PC patients. Analysis of the role of other investigated GST polymorphisms (GSTM1, GSTT1, and GSTP1) in terms of PC prognosis has shown shorter survival in carriers of GSTP1*T/T (rs1138272) genotype than in those carrying at least one referent allele. In addition, the presence of GSTP1*T/T genotype independently predicted a four-fold higher risk of overall mortality among PC patients. This study demonstrated a significant prognostic role of GST polymorphism in PC.

A modern era of personalized medicine in the diagnosis, prognosis, and treatment of prostate cancer

The present era is witnessing rapid advancements in the field of medical informatics and modern healthcare management. The role of translational bioinformatics (TBI), an infant discipline in the field of medical informatics, is pivotal in this revolution. The development of high-throughput technologies [e.g., microarrays, next-generation sequencing (NGS)] has propelled TBI to the next stage in this modern era of medical informatics. In this review, we assess the promising translational outcomes of microarray- and NGS-based discovery of genes, proteins, micro RNAs, and other active biological compounds aiding in the diagnosis, prognosis, and therapy of prostate cancer (PCa) to improve treatment strategies at the localized and/or metastatic stages in patients. Several promising candidate biomarkers in circulating blood (miR-25-3p and miR-18b-5p), urine (miR-95, miR-21, miR-19a, and miR-19b), and prostatic secretions (miR-203) have been identified. AURKA and MYCN, novel candidate biomarkers, were found to be specifically expressed in neuroendocrine PCa. The use of BTNL2 gene mutations and inflammasomes as biomarkers in immune function-mediated, inherited PCa has also been elucidated based on NGS data. Although TBI discoveries can benefit clinical performance metrics, the translational potential and the in vivo performance of TBI outcomes need to be verified. In conclusion, TBI aids in the effective clinical management of PCa; furthermore, the fate of personalized/precision medicine mostly relies on the enhanced diagnostic, prognostic, and therapeutic potential of TBI.

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.

Epigenetic alterations in TRAMP mice: epigenome DNA methylation profiling using MeDIP-seq

PURPOSE

We investigated the genomic DNA methylation profile of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) cancer model and to analyze the crosstalk among targeted genes and the related functional pathways.

METHODS

Prostate DNA samples from 24-week-old TRAMP and C57BL/6 male mice were isolated. The DNA methylation profiles were analyzed by methylated DNA immunoprecipitation (MeDIP) followed by next-generation sequencing (MeDIP-seq). Canonical pathways, diseases and function and network analyses of the different samples were then performed using the Ingenuity® Pathway Analysis (IPA) software. Some target genes with significant difference in methylation were selected for validation using methylation specific primers (MSP) and qPCR.

RESULTS

TRAMP mice undergo extensive aberrant CpG hyper- and hypo-methylation. There were 2147 genes with a significant (log2-change ≥ 2) change in CpG methylation between the two groups, as mapped by the IPA software. Among these genes, the methylation of 1105 and 1042 genes was significantly decreased and increased, respectively, in TRAMP prostate tumors. The top associated disease identified by IPA was adenocarcinoma; however, the cAMP response element-binding protein (CREB)-, histone deacetylase 2 (HDAC2)-, glutathione S-transferase pi (GSTP1)- and polyubiquitin-C (UBC)-related pathways showed significantly altered methylation profiles based on the canonical pathway and network analyses. MSP and qPCR results of genes of interests corroborated with MeDIP-seq findings.

CONCLUSIONS

This is the first MeDIP-seq with IPA analysis of the TRAMP model to provide novel insight into the genome-wide methylation profile of prostate cancer. Studies on epigenetics, such as DNA methylation, will potentially provide novel avenues and strategies for further development of biomarkers targeted for treatment and prevention approaches for prostate cancer.

Proteomic Analysis of Neuroblastoma-Derived Exosomes: New Insights into a Metastatic Signature

Neuroblastoma (NB) is the most common extracranial pediatric solid tumor. Around 70% of patients with metastatic disease at diagnosis present bone-marrow infiltration, which is considered a marker of poor outcome; however, the mechanism underlying this specific tropism has to be elucidated. Tumor-derived exosomes may support metastatic progression in several tumors by interacting with the microenvironment, and may serve as tumor biomarkers. The main objective of this study is to identify an exosomal signature associated with NB metastatic bone-marrow dissemination. Therefore, the proteomic cargo of exosomes isolated from NB cell lines derived from primary tumor and bone-marrow metastasis is characterized. The comparison among exosomal proteins show 15 proteins exclusively present in primary tumor-derived exosomes, mainly involved in neuronal development, and 6 proteins in metastasis-derived exosomes related to cancer progression. Significant proteins obtain with statistical analysis performed between the two groups, reveal that primary tumor exosomes contain a higher level of proteins involved in extra-cellular matrix (ECM) assembly and adhesion, as well as in neuronal development. Exosomes isolated from bone-marrow metastasis exhibit proteins involved in ameboidal cell migration and mitochondrial activity. This work suggests that proteomic profiling of NB-derived exosomes reflects the tumor stage and may be considered as potential tumor biomarker.

Glutathione-s-transferase A 4 (GSTA4) suppresses tumor growth and metastasis of human hepatocellular carcinoma by targeting AKT pathway

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies of cancers and its prognosis remains dismal due to the paucity of effective therapeutic targets. Up-regulation of glutathione-s-transferase A 4 (GSTA4) is associated with poor prognosis of HCC, but its functional mechanism in HCC remains unclear. In this study, we investigated the roles of GSTA4 in tumor growth and metastasis of HCC and found that GSTA4 was frequently up-regulated in HCC tissues. Through gain- and loss-of-function studies, GSTA4 was demonstrated to significantly regulate cell proliferation, migration, and invasion in vitro. Furthermore, GSTA4 overexpressing significantly promoted the tumorigenicity and metastasis of HCC cells in nude mice models bearing human HCC, whereas silencing endogenous GSTA4 caused an opposite outcome. Moreover, we demonstrated that GSTA4 enhanced HCC aggressiveness by activating protein kinase B (AKT) signaling. In multivariate analysis, our results GSTA4 overexpression promotes the progression of hepatocellular carcinoma and might represent a novel therapeutic target for its treatment.

Epigenetic CpG Methylation of the Promoter and Reactivation of the Expression of GSTP1 by Astaxanthin in Human Prostate LNCaP Cells

Astaxanthin (AST), a red dietary carotenoid, has synergistic antioxidant effects with polyunsaturated fatty acids at low concentrations via Nuclear factor (erythroid-derived 2)-like 2 (NFE2L2 or Nrf2)/antioxidant response element (ARE) signaling. In addition, chromatin remodeling and DNA methylation-based gene silencing represent a common mechanism in prostate carcinogenesis and tumor progression from normal cells to pre-initiated cells and ultimately to invasive carcinoma. Therefore, the control of epigenetic modification and the transcriptional/translational control of the activation of Nrf2 and Nrf2-target genes, including glutathione S-transferases (GSTs), appear to be an important mechanism that protects cells against injuries from oxidative stress and cancer development. In this study, we aim to investigate the role of AST in reactivating the expression of Nrf2 and GSTP1 through epigenetic modification in human prostate LNCaP cells. Treatment with AST in human LNCaP cells reduced the methylation of 21 CpG sites of the GSTP1 CpG island but did not affect the three CpG sites of the Nrf2 promoter region. AST induced the mRNA expression and protein expression of both Nrf2 and GSTP1. It also increased the mRNA expression of NQO1 in sh-mock LNCaP cells but not in sh-SETD7 LNCaP cells. Furthermore, AST reduced the protein expression of DNMT3b and significantly inhibited DNMT and HDAC activities in vitro. Taken together, these results suggest that AST decreased the methylation status of the GSTP1, and these epigenetic modifying effects may originate from the decreasing activities of epigenetic modification enzymes, contributing to the overall beneficial health effects of AST.

GSTP1 and GSTO1 single nucleotide polymorphisms and the response of bladder cancer patients to intravesical chemotherapy

SNPs may restrict cell detoxification activity and be a potential risk factor for cancer chemosensitivity. We evaluated the predictive value of these polymorphisms on the sensitivity of bladder cancer patients to epirubicin and mitomycin chemotherapy instillation as well as their toxicities. SNPs were analyzed by TaqMan genotyping assays in 130 patients treated with epirubicin and 114 patients treated with mitomycin. Recurrence-free survival (RFS) was estimated by the Kaplan-Meier method, and hazard ratios (HRs) and 95% confidence intervals (CIs) of the HRs were derived from multivariate Cox proportional hazard models. GSTP1 rs1695 and GSTO1 rs4925 were also associated with RFS in the epirubicin group. Patients carrying the GSTP1 AG+GG and GSTO1 AC+AA genotypes had an unfavorable RFS. Patients with the GSTP1 AA and GSTO1 CC genotypes had a reduced risk of recurrence after the instillation of epirubicin. In addition, patients with the GSTP1 rs1695 AA genotype had an increased risk of irritative voiding symptoms; while patients with the GSTO1 rs4925 CC genotype had a decreased risk of hematuria. Our results suggest that GSTP1 and GSTO1 polymorphisms are associated with epirubicin treatment outcomes as well as with epirubicin-related toxicity.

Epigenetic DNA methylation of antioxidative stress regulator NRF2 in human prostate cancer

Epigenetic control of NRF2, a master regulator of many critical antioxidative stress defense genes in human prostate cancer (CaP), is unknown. Our previous animal study found decreased Nrf2 expression through promoter CpG methylation/histone modifications during prostate cancer progression in TRAMP mice. In this study, we evaluated CpG methylation of human NRF2 promoter in 27 clinical prostate cancer samples and in LNCaP cells using MAQMA analysis and bisulfite genomic DNA sequencing. Prostate cancer tissue microarray (TMA) containing normal and prostate cancer tissues was studied by immunohistochemistry. Luciferase reporter assay using specific human NRF2 DNA promoter segments and chromatin immunoprecipitation (ChIP) assay against histone modifying proteins were performed in LNCaP cells. Three specific CpG sites in the NRF2 promoter were found to be hypermethylated in clinical prostate cancer samples (BPH<ADT-RCaP<AS-CaP). NRF2 staining in human prostate cancer TMA showed a decreasing trend for both intensity and percentage of positive cells from normal tissues to advanced-stage prostate cancer (Gleason score from 3-9). Reporter assays in the LNCaP cells containing these three CpG sites showed methylation-inhibited transcriptional activity of the NRF2 promoter. LNCaP cells treated with 5-aza/TSA restored the expression of NRF2 and NRF2 downstream target genes, decreased expression levels of DNMT and HDAC proteins, and ChIP assays showed increased RNA Pol II and H3Ac with a concomitant decrease in H3K9me3, MBD2, and MeCP2 at CpG sites of human NRF2 promoter. Taken together, these findings suggest that epigenetic modification may contribute to the regulation of transcription activity of NRF2, which could be used as prevention and treatment target of human prostate cancer.

DLJ14, a novel chemo-sensitization agent, enhances therapeutic effects of adriamycin against MCF-7/A cells both in vitro and in vivo

OBJECTIVES

We investigated the chemo-sensitization of a ligustrazine derivate, (E)-2-(2, 4-dimethoxystyryl)-3, 5, 6-trimethylpyrazine (DLJ14) on Adriamycin (Adr, Wanle, Shenzhen, China)-resistant human breast cancer (MCF-7/A) cells both in vivo and in vitro.

METHODS

The antitumour effects of DLJ14 and Adr was observed in MCF-7/A cells by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro and was evaluated by MCF-7/A xenografts in nude mice. The intracellular Adr accumulation was assessed by mean fluorescence intensity of Adr. The messenger RNA level of glutathione (GSH) S-transferase (GST)π in MCF-7/A cells was determined by real-time reverse transcription PCR assay. The expression of GSTπ, c-jun NH2 -terminal kinase (JNK) and phosphor-JNK (p-JNK) was detected by Western blotting method.

KEY FINDINGS

The MTT results showed that DLJ14 exhibited a weak inhibition on proliferation of both MCF-7 and MCF-7/A cells, in contrast with the strong inhibition of verapamil. When DLJ14 is combined with Adr, the inhibitory effect on MCF-7/A cells and MCF-7/A xenografts was enhanced significantly through increasing intracellular accumulation of Adr by inhibition of GSH level and the activity of GSH peroxidase and GST. Moreover, DLJ14 could downregulate the expression of GSTπ and increase the expression of JNK and p-JNK in MCF-7/A cells or in xenografts.

CONCLUSION

DLJ14 is a promising chemo-sensitization candidate for the reversal of multidrug resistance in cancers.

Involvement of redox state in the aging of Drosophila melanogaster

SIGNIFICANCE

The main objective of this review was to provide an exposition of investigations, conducted in Drosophila melanogaster, on the role of reactive oxygen species and redox state in the aging process. While early transgenic studies did not clearly support the validity of the oxidative stress hypothesis of aging, predicated on the accumulation of structural damage, they spawned a broader search for redox-related effects that might impact the aging process.

RECENT ADVANCES

Initial evidence implicating the thiol redox state as a possible causative factor in aging has been obtained in Drosophila. Overexpression of genes, such as GCL, G6PD, Prx2, and Prx5, which are involved in the maintenance of thiol redox homeostasis, has strong positive effects on longevity. Further, the depletion of peroxiredoxin activity in the mitochondria through the double knockdown of Prx5 and Prx3 not only results in a redox crisis but also elicits a rapid aging phenotype.

CRITICAL ISSUES

Herein, we summarize the present status of knowledge about the main components of the machinery controlling thiol redox homeostasis and describe how age-related redox fluctuations might impact aging more acutely through disruption of the redox-sensitive signaling mechanisms rather than via the simple accumulation of structural damage.

FUTURE DIRECTIONS

Based on these initial insights into the plausible impact of redox fluctuations on redox signaling, future studies should focus on the pathways that have been explicitly implicated in aging, such as insulin signaling, TOR, and JNK/FOXO, with particular attention to elements that are redox sensitive.

A γ-tocopherol-rich mixture of tocopherols maintains Nrf2 expression in prostate tumors of TRAMP mice via epigenetic inhibition of CpG methylation

Nuclear factor-erythroid 2-related factor 2 (Nrf2) plays a pivotal role in maintaining cellular redox homeostasis and eliminating reactive toxic species. Nrf2 is epigenetically suppressed due to CpG hypermethylation in prostate tumors from the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. We previously showed that dietary feeding of a γ-tocopherol-rich mixture of tocopherols (γ-TmT) suppressed prostate tumorigenesis in TRAMP mice associated with higher Nrf2 protein expression. We hypothesized that γ-TmT may maintain Nrf2 through epigenetic inhibition of promoter CpG methylation. In this study, 8-wk-old male TRAMP mice were fed 0.1% γ-TmT or a control diet for 16 wk. The methylation in the Nrf2 promoter was inhibited in the prostate of the γ-TmT group compared with the control group. Protein expressions of DNA methyltransferase (DNMT), including DNMT1, DNMT3A, and DNMT3B, were lower in the prostate of the γ-TmT group than in the controls. TRAMP-C1 cells were treated with 30 μmol/L of γ-TmT or blank medium for 5 d. The methylation in the Nrf2 promoter was inhibited in the γ-TmT-treated cells compared with the untreated cells at d 5, and mRNA and protein expressions of Nrf2 and NAD(P)H:quinone oxidoreductase 1 were higher. Interestingly, only DNMT3B was inhibited in the γ-TmT-treated cells compared with the untreated cells. In the aggregate, our findings demonstrate that γ-TmT could inhibit CpG methylation in the Nrf2 promoter in the prostate of TRAMP mice and in TRAMP-C1 cells, which might lead to higher Nrf2 expression and potentially contribute to the prevention of prostate tumorigenesis in this TRAMP model.

GSTT1: a marker of the aggressiveness of bladder cancer

INTRODUCTION

Glutathione S-transferases have been implicated in the development of bladder cancer (BC). We investigated the genotype and expression of glutathione S-transferase-mu (GSTM1) and glutathione S-transferase-theta (GSTT1) in BC tissue specimens.

MATERIALS AND METHODS

Tumor samples and matched normal mucosae were obtained from 34 patients. Genomic DNA was used to analyze GSTM1 and GSTT1 genotypes using multiplex polymerase chain reaction. GSTM1 and GSTT1 mRNA levels were measured using real-time reverse transcriptase polymerase chain reaction.

RESULTS

GSTM1 mRNA expression was lower in tumor tissues than in matched normal bladder mucosae, whereas GSTT1 mRNA expression was significantly higher. GSTT1 mRNA expression was higher in muscle-invasive BC and high-grade cancers than in non-muscle-invasive BC and lower-grade tumors.

CONCLUSIONS

GSTT1 is correlated with characteristics of aggressive BC. GSTT1 may play an important role in tumorigenesis and disease progression in patients with BC.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Distribution of glutathione S-transferase T1 and M1 genes polymorphisms in North East Indians: a potential report

BACKGROUND

Detoxifying glutathione S-transferase (GST) gene polymorphisms show variation in different ethnic populations. GST detoxifies and metabolizes carcinogens, including oxygen free radicals. GST polymorphisms have been associated with susceptibility to different diseases. In the current study, allelic polymorphisms of GSTM1 and GSTT1 were analyzed in three ethnic groups of North East (NE) India where a high prevalence of various cancers and other diseases such as hypertension, tuberculosis, and asthma have been reported.

METHODS

We compared the prevalence of GSTT1 and GSTM1 deletion genotypes, which were determined by multiplex polymerase chain reaction, in 422 voluntary, healthy NE Indians with those of other populations. The data was statistically analyzed.

RESULTS

The GSTT1-null genotype was found in 51%, 34.3%, and 15.7% of individuals (from Mizoram, Sikkim, and Assam regions of NE India, respectively), whereas the GSTM1-null genotype was found in 46.9%, 46%, and 35% of individuals from the same areas.

CONCLUSIONS

The NE Indians differ from the rest of the Indian population with reference to genotypic distribution of GST polymorphisms but the frequency was found to be similar to that which has been reported from China. This may explain the hypothesis of the common ancestral origin of both the NE Indians and the Chinese and a higher frequency of cancers such as gastric, esophageal, and oral cancers, which has been reported from these regions. This study establishes baseline frequency data for GST polymorphisms for future case control studies on the role these polymorphisms play with regard to diseases. The results presented here provide the first report on GST polymorphisms in the NE Indian population.

Decreased expression of GST pi is correlated with a poor prognosis in human esophageal squamous carcinoma

Background

Glutathione S-transferase pi (GST pi) is a subgroup of GST family, which provides cellular protection against free radical and carcinogenic compounds due to its detoxifying function. Expression patterns of GST pi have been studied in several carcinomas and its down-regulation was implicated to be involved in malignant transformation in patients with Barrett's esophagus. However, neither the exact role of GST pi in the pathogenesis nor its prognostic impact in squamous esophageal carcinoma is fully characterized.

Methods

Immunohistochemistry was used to investigate GST pi expression on 153 archival squamous esophageal carcinoma specimens with a GST pi monoclonal antibody. Statistic analyses were performed to explore its association with clinicopathological factors and clinical outcome.

Results

The GST pi expression was greatly reduced in tissues of esophageal carcinomas compared to adjacent normal tissues and residual benign tissues. Absent of GST pi protein expression in cytoplasm, nuclear and cytoplasm/nucleus was found in 51%, 64.7% and 48% of all the carcinoma cases, respectively. GST pi deficiency in cytoplasm, nucleus and cytoplasm/nucleus was significantly correlated to poor differentiation (p < 0.001, p < 0.001 and p < 0.001, respectively). UICC stage and T stage were found significantly correlated to negative expression of GST pi in cytoplasm (p < 0.001 and p = 0.004, respectively) and cytoplasm/nucleus (p = 0.017 and p = 0.031, respectively). In univariate analysis, absent of GST pi protein expression in cytoplasm, nucleus and cytoplasm/nucleus was significantly associated with a shorter overall survival (p < 0.001, p < 0.001 and p < 0.001, respectively), whereas only GST pi cytoplasmic staining retained an independent prognostic significance (p < 0.001) in multivariate analysis.

Conclusions

Our results show that GST pi expression is down regulated in the squamous esophageal carcinoma, and that the lack of GST pi expression is associated with poor prognosis. Therefore, deficiency of GST pi protein expression may be an important mechanism involved in the carcinogenesis and progression of the squamous esophageal carcinoma, and the underlying mechanisms leading to decreased GST pi expression deserve further investigation.

A water-soluble parthenolide analogue suppresses in vivo prostate cancer growth by targeting NFkappaB and generating reactive oxygen species

BACKGROUND

To characterize the molecular changes associated with DMAPT-induced prostate cancer cell death and its in vivo activity.

METHODS

CWR22Rv1 and PC-3 were subjected to flow cytometry, electrophoretic mobility shift assays, and Western blot studies to measure DMAPT's ability to generate reactive oxygen species (ROS), inhibit NFkappaB DNA binding, and cause changes in anti-apoptotic proteins. N-acetyl cysteine (NAC) and short hairpin RNA (shRNA) were used to determine the contribution of ROS and JNK2 activation, respectively. The BrdU incorporation assay was used to measure proliferation and trypan blue studies assessed cell viability after DMAPT treatment. The in vivo activity of DMAPT as a single agent and in combination with bicalutamide or docetaxel was assessed in a subcutaneous xenograft model with athymic nude female mice.

RESULTS

DMAPT generated ROS with subsequent JNK activation and inhibited NFkappaB DNA binding and expression of NFkappaB-regulated anti-apoptotic proteins. DMAPT increased necrotic and apoptotic cell death in a cell-type-dependent manner and both types of cell death were blocked by NAC. Additionally, shRNA JNK2 partially blocked the anti-proliferative activity of DMAPT. DMAPT inhibited CWR22Rv1 and PC-3 cellular proliferation by 100% with 10 and 20 microM respectively and in vivo, DMAPT was more effective at inhibiting growth than biclutamide (CWR22v1) and docetaxel (PC-3).

CONCLUSIONS

DMAPT promotes cell death by both generating ROS and inhibition of NFkappaB. Its in vivo activity supports the conduct of clinical trials in patients with castrate-resistant disease.

Opposing roles of Dnmt1 in early- and late-stage murine prostate cancer

Previous studies have shown that tumor progression in the transgenic adenocarcinoma of mouse prostate (TRAMP) model is characterized by global DNA hypomethylation initiated during early-stage disease and locus-specific DNA hypermethylation occurring predominantly in late-stage disease. Here, we utilized Dnmt1 hypomorphic alleles to examine the role of Dnmt1 in normal prostate development and in prostate cancer in TRAMP. Prostate tissue morphology and differentiation status was normal in Dnmt1 hypomorphic mice, despite global DNA hypomethylation. TRAMP; Dnmt1 hypomorphic mice also displayed global DNA hypomethylation, but were characterized by altered tumor phenotype. Specifically, TRAMP; Dnmt1 hypomorphic mice exhibited slightly increased tumor incidence and significantly increased pathological progression at early ages and, conversely, displayed slightly decreased tumor incidence and significantly decreased pathological progression at advanced ages. Remarkably, hypomorphic Dnmt1 expression abrogated local and distant site macrometastases. Thus, Dnmt1 has tumor suppressor activity in early-stage prostate cancer, and oncogenic activity in late stage prostate cancer and metastasis. Consistent with the biological phenotype, epigenomic studies revealed that TRAMP; Dnmt1 hypomorphic mice show dramatically reduced CpG island and promoter DNA hypermethylation in late-stage primary tumors compared to control mice. Taken together, the data reveal a crucial role for Dnmt1 in prostate cancer and suggest that Dnmt1-targeted interventions may have utility specifically for advanced and/or metastatic prostate cancer.

Nrf2 expression is regulated by epigenetic mechanisms in prostate cancer of TRAMP mice

Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) is a transcription factor which regulates the expression of many cytoprotective genes. In the present study, we found that the expression of Nrf2 was suppressed in prostate tumor of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) mice. Similarly, the expression of Nrf2 and the induction of NQO1 were also substantially suppressed in tumorigenic TRAMP C1 cells but not in non-tumorigenic TRAMP C3 cells. Examination of the promoter region of the mouse Nrf2 gene identified a CpG island, which was methylated at specific CpG sites in prostate TRAMP tumor and in TRAMP C1 cells but not in normal prostate or TRAMP C3 cells, as shown by bisulfite genomic sequencing. Reporter assays indicated that methylation of these CpG sites dramatically inhibited the transcriptional activity of the Nrf2 promoter. Chromatin immunopreceipitation (ChIP) assays revealed increased binding of the methyl-CpG-binding protein 2 (MBD2) and trimethyl-histone H3 (Lys9) proteins to these CpG sites in the TRAMP C1 cells as compared to TRAMP C3 cells. In contrast, the binding of RNA Pol II and acetylated histone H3 to the Nrf2 promoter was decreased. Furthermore, treatment of TRAMP C1 cells with DNA methyltransferase (DNMT) inhibitor 5-aza-2′-deoxycytidine (5-aza) and histone deacetylase (HDAC) inhibitor trichostatin A (TSA) restored the expression of Nrf2 as well as the induction of NQO1 in TRAMP C1 cells. Taken together, these results indicate that the expression of Nrf2 is suppressed epigenetically by promoter methylation associated with MBD2 and histone modifications in the prostate tumor of TRAMP mice. Our present findings reveal a novel mechanism by which Nrf2 expression is suppressed in TRAMP prostate tumor, shed new light on the role of Nrf2 in carcinogenesis and provide potential new directions for the detection and prevention of prostate cancer.