CpG Hypermethylation ofMDR1Gene Contributes to the Pathogenesis and Progression of Human Prostate Cancer

Systematic review of comparative transcriptomic studies of cellular resistance to genotoxic stress

The development of resistance by tumor cells to various types of therapy is a significant problem that decreases the effectiveness of oncology treatments. For more than two decades, comparative transcriptomic studies of tumor cells with different sensitivities to ionizing radiation and chemotherapeutic agents have been conducted in order to identify the causes and mechanisms underlying this phenomenon. However, the results of such studies have little in common and often contradict each other. We have assumed that a systematic analysis of a large number of such studies will provide new knowledge about the mechanisms of development of therapeutic resistance in tumor cells. Our comparison of 123 differentially expressed gene (DEG) lists published in 98 papers suggests a very low degree of consistency between the study results. Grouping the data by type of genotoxic agent and tumor type did not increase the similarity. The most frequently overexpressed genes were found to be those encoding the transport protein ABCB1 and the antiviral defense protein IFITM1. We put forward a hypothesis that the role played by the overexpression of the latter in the development of resistance may be associated not only with the stimulation of proliferation, but also with the limitation of exosomal communication and, as a result, with a decrease in the bystander effect. Among down regulated DEGs, BNIP3 was observed most frequently. The expression of BNIP3, together with BNIP3L, is often suppressed in cells resistant to non-platinum genotoxic chemotherapeutic agents, whereas it is increased in cells resistant to ionizing radiation. These observations are likely to be mediated by the binary effects of these gene products on survival, and regulation of apoptosis and autophagy. The combined data also show that even such obvious mechanisms as inhibition of apoptosis and increase of proliferation are not universal but show multidirectional changes.

P-Glycoprotein and Androgen Receptor Expression Reveals Independence of Canine Prostate Cancer from Androgen Hormone Stimulation

Canine prostate cancer (PC) is an aggressive disease, and dogs can be considered comparative models for human PC. In recent years, canine PC has been shown to resemble human castrate-resistant prostate cancer. The influx and efflux of testosterone in prostatic luminal cells are regulated by P-glycoprotein (P-gp). Therefore, human PC generally lacks P-gp expression and maintains the expression of androgen receptors (ARs). However, this co-expression has not previously been investigated in dogs. Therefore, this study aimed to evaluate AR and P-gp co-expression to elucidate these protein patterns in canine prostate samples. We identified AR/P-gp double immunofluorescence co-expression of both proteins in normal luminal cells. However, in canine PC, cells lack AR expression and exhibit increased P-gp expression. These results were confirmed by gene expression analyses. Overall, our results strongly suggest that normal canine prostate testosterone influx may be regulated by P-gp expression, and that during progression to PC, prostatic cells lack AR expression and P-gp overexpress. P-gp expression in canine PC may be related to a phenotype of multiple drug resistance.

Aberrant DNA Methylation of ABC Transporters in Cancer

ATP-binding cassette (ABC) transporters play a crucial role in multidrug resistance (MDR) of cancers. They function as efflux pumps, resulting in limited effectiveness or even failure of therapy. Increasing evidence suggests that ABC transporters are also involved in tumor initiation, progression, and metastasis. Tumors frequently show multiple genetic and epigenetic abnormalities, including changes in histone modification and DNA methylation. Alterations in the DNA methylation status of ABC transporters have been reported for a variety of cancer types. In this review, we outline the current knowledge of DNA methylation of ABC transporters in cancer. We give a brief introduction to structure, function, and gene regulation of ABC transporters that have already been investigated for their DNA methylation status in cancer. After giving an overview of the applied methodologies and the CpGs analyzed, we summarize and discuss the findings on aberrant DNA methylation of ABC transporters by cancer types. We conclude our review with the discussion of the potential to target aberrant DNA methylation of ABC transporters for cancer therapy.

Hypermethylation of multiple Wnt antagonist genes in gastric neoplasia: Is H pylori infection blasting fuse?

Wnt antagonist genes hypermethylation has been found in several tumors. Accordingly, the events that occur during the progression of adenoma to carcinoma have been characterized and include activation of the Wnt-pathway. Further, gastric adenoma (GA) is a premalignant lesion of gastric adenocarcinoma (GAC). In this paper, we focused our interesting on Wnt signaling path function in the pathogenesis of GAC.We compared the differences between low grade adenoma (LGA), high grade adenoma (HGA), GACs and corresponding normal gastric tissue (NGT). Specific indexes include the pathological characteristics of gastric neoplasia, Helicobacter pylori infection, β-catenin mutation status, and methylation status of Wnt antagonist genes.There was significant difference of β-catenin expression in patient with NGT, LGA, HGA, and GAC, the results respectively were 4.2%, 41.7%, 83.3%, and 91.7%. Only 1 GACs was detected exon 3 of β-catenin mutation. Wnt antagonist genes mRNA expression levels, such as APC, sFRP-1, Wif-1, and Dkk-1, were significantly reduced in GAC. Promoter methylation levels of the 4 genes were significantly elevated in GAC and HGA compared to NGT and LGA. However, there was no significant difference between HGAs and GACs. The β-catenin abnormal expression was correlated with hypermethylation of these 4 genes. Multiple gene concurrent methylation phenomenon was increased from NGTs to GACs; the amount of methylation genes in GACs and HGAs was more than NGTs and LGAs. The more methylation of the above-mentioned genes, the more severity of local inflammation. The infection rate of H pylori was significantly higher in patient with HGA (66.7%, 16/24) and GAC (58.5%, 14/24) than in LGAs (16.7%,4/24) (PHGA-LGA = .024, PGAC-LGA = .032). In addition, the present of H pylori also correlated with the β-catenin abnormal expression and the hypermethylation status of Wnt antagonist genes (P < .001). But other parameters in adenoma cases had no significantly related with infection of H pylori.Hypermethylation of Wnt antagonist genes may have a tight relationship with gastric tumorigenesis. And these genes may increase the incidence of GAC. Additionally, H pylori may have promotion function in GA formation.

Promoter methylation patterns of ABCB1, ABCC1 and ABCG2 in human cancer cell lines, multidrug-resistant cell models and tumor, tumor-adjacent and tumor-distant tissues from breast cancer patients

Overexpression of ABCB1, ABCC1 and ABCG2 in tumor tissues is considered a major cause of limited efficacy of anticancer drugs. Gene expression of ABC transporters is regulated by multiple mechanisms, including changes in the DNA methylation status. Most of the studies published so far only report promoter methylation levels for either ABCB1 or ABCG2, and data on the methylation status for ABCC1 are scarce. Thus, we determined the promoter methylation patterns of ABCB1, ABCC1 and ABCG2 in 19 human cancer cell lines. In order to contribute to the elucidation of the role of DNA methylation changes in acquisition of a multidrug resistant (MDR) phenotype, we also analyzed the promoter methylation patterns in drug-resistant sublines of the cancer cell lines GLC-4, SW1573, KB-3-1 and HL-60. In addition, we investigated if aberrant promoter methylation levels of ABCB1, ABCC1 and ABCG2 occur in tumor and tumor-surrounding tissues from breast cancer patients.

Our data indicates that hypomethylation of the ABCC1 promoter is not cancer type-specific but occurs in cancer cell lines of different origins. Promoter methylation was found to be an important mechanism in gene regulation of ABCB1 in parental cancer cell lines and their drug-resistant sublines. Overexpression of ABCC1 in MDR cell models turned out to be mediated by gene amplification, not by changes in the promoter methylation status of ABCC1. In contrast to the promoters of ABCC1 and ABCG2, the promoter of ABCB1 was significantly higher methylated in tumor tissues than in tumor-adjacent and tumor-distant tissues from breast cancer patients.

Frequent down-regulation of ABC transporter genes in prostate cancer

Background

ATP-binding cassette (ABC) transporters are transmembrane proteins responsible for the efflux of a wide variety of substrates, including steroid metabolites, through the cellular membranes. For better characterization of the role of ABC transporters in prostate cancer (PCa) development, the profile of ABC transporter gene expression was analyzed in PCa and noncancerous prostate tissues (NPT).

Methods

TaqMan Low Density Array (TLDA) human ABC transporter plates were used for the gene expression profiling in 10 PCa and 6 NPT specimens. ABCB1 transcript level was evaluated in a larger set of PCa cases (N = 78) and NPT (N = 15) by real-time PCR, the same PCa cases were assessed for the gene promoter hypermethylation by methylation-specific PCR.

Results

Expression of eight ABC transporter genes (ABCA8, ABCB1, ABCC6, ABCC9, ABCC10, ABCD2, ABCG2, and ABCG4) was significantly down-regulated in PCa as compared to NPT, and only two genes (ABCC4 and ABCG1) were up-regulated. Down-regulation of ABC transporter genes was prevalent in the TMPRSS2-ERG-negative cases.

A detailed analysis of ABCB1 expression confirmed TLDA results: a reduced level of the transcript was identified in PCa in comparison to NPT (p = 0.048). Moreover, the TMPRSS2-ERG-negative PCa cases showed significantly lower expression of ABCB1 in comparison to NPT (p = 0.003) or the fusion-positive tumors (p = 0.002). Promoter methylation of ABCB1 predominantly occurred in PCa and was rarely detected in NPT (p < 0.001).

Conclusions

The study suggests frequent down-regulation of the ABC transporter genes in PCa, especially in the TMPRSS2-ERG-negative tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1689-8) contains supplementary material, which is available to authorized users.

The expression of RUNDC3B is associated with promoter methylation in lymphoid malignancies

DNA methylation is an epigenetic modification that plays an important role in the regulation of gene expression. The function of RUNDC3B has yet to be determined, although its dysregulated expression has been associated with malignant potential of both breast and lung carcinoma. To elucidate the potential of using DNA methylation in RUNDC3B as a biomarker in lymphoid malignancies, the methylation status of six regions spanning the CpG island in the promoter region of RUNDC3B was determined in cancer cell lines. Lymphoid malignancies were found to have more prominent methylation and did not express RUNDC3B compared with myeloid malignancies and solid tumours, supporting the potential use of DNA methylation in this region as a biomarker for lymphoid malignancies. RUNDC3B contains a RUN domain in its N‐terminal region that mediates interaction with Rap2, an important component of the mitogen‐activated protein kinase (MAPK) cascade, which regulates cellular proliferation and differentiation. The protein sequence of RUNDC3B also contains characteristic binding sites for MAPK intermediates. Therefore, it is possible that RUNDC3B serves as a mediator between Rap2 and the MAPK signalling cascade. Three genes with MAPK‐inducible expression were downregulated in a methylated leukaemia cell line (HSPA5, Jun and Fos). Jun and Fos combine to form the activating protein 1 transcription factor, and loss of this factor is associated with the dysregulation of genes involved in differentiation and proliferation. We hypothesize that the loss of RUNDC3B secondary to aberrant hypermethylation of the early growth response 3 transcription factor binding site results in dysregulated MAPK signalling and carcinogenesis in lymphoid malignancies. © 2015 The Authors. Hematological Oncology published by John Wiley & Sons Ltd

Genetic polymorphisms of the multidrug resistance 1 gene MDR1 and the risk of hepatocellular carcinoma

A possible association between multiple drug resistance 1 gene (MDR1) polymorphisms and the risk of developing hepatocellular carcinoma (HCC) is currently under debate, and evidence from various epidemiological studies has yielded controversial results. To derive a more precise estimation of the association between MDR1 polymorphisms and HCC risk, the present meta-analysis was performed. A total of 8 studies containing 11 cohorts with 4407 cases and 4436 controls were included by systematic literature search of EMBASE, PubMed, Web of Science, and CNKI. All polymorphisms were classified as mutant/wild-type alleles. In particular, the variation type, functional impact, and protein domain location of the polymorphisms were assessed and used as stratified indicators. The pooled odds ratio (OR) with 95 % confidence interval (CI) was calculated to evaluate the association. Overall, our results suggested that the mutant alleles of the MDR1 gene were associated with a significantly increased risk for HCC under all genetic models (allelic model: OR = 1.28, 95 % CI = 1.20-1.36, P < 0.001; dominant model: OR = 1.27, 95 % CI = 1.16-1.38, P < 0.001; recessive model: OR = 1.59, 95 % CI = 1.36-1.85, P < 0.001). Furthermore, increased risks for HCC were also revealed in stratified analyses by ethnicity, sample size, and quality scores of cohorts as well as variation type, functional impact, and protein domain location of polymorphisms. In conclusion, the present meta-analysis suggested that the presence of MDR1 mutant alleles might be a risk factor for HCC.

Potency of non-steroidal anti-inflammatory drugs in chemotherapy

Cancer cell resistance, particularly multidrug resistance (MDR), is the leading cause of chemotherapy failure. A number of mechanisms involved in the development of MDR have been described, including the overexpression of ATP-dependent membrane-bound transport proteins. The enhanced expression of these proteins, referred to as ATP-binding cassette (ABC) transporters, results in an increased cellular efflux of the cytotoxic drug, thereby reducing its intracellular concentration to an ineffective level. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently consumed drugs worldwide. NSAIDs are mainly used to treat pain, fever and inflammation. Numerous studies suggest that NSAIDs also show promise as anticancer drugs. NSAIDs have been shown to reduce cancer cell proliferation, motility, angiogenesis and invasiveness. In addition to these effects, NSAIDs have been shown to induce apoptosis in a wide variety of cancer types. Moreover, several studies have indicated that NSAIDs may sensitise cancer cells to the antiproliferative effects of cytotoxic drugs by modulating ABC transporter activity. Therefore, combining specific NSAIDs with chemotherapeutic drugs may have clinical applications. Such treatments may allow for the use of a lower dose of cytotoxic drugs and may also enhance the effectiveness of therapy. The objective of this review was to discuss the possible role of NSAIDs in the modulation of antitumour drug cytotoxicity. We particularly emphasised on the use of COX-2 inhibitors in combination with chemotherapy and the molecular and cellular mechanisms underlying the alterations in outcome that occur in response to this combination therapy.

ABCB1 regulation through LRPPRC is influenced by the methylation status of the GC -100 box in its promoter

One of the potential mechanisms of imatinib mesylate (IM) resistance in chronic myeloid leukemia (CML) is increased level of P-glycoprotein (Pgp). Pgp is an efflux pump capable of activating the multidrug resistance (MDR) phenotype. The gene encoding Pgp (ABCB1) has several binding sites in its promoter region, along with CpG islands and GC boxes, involved in its epigenetic control. In previous work, we performed a proteomic study to identify proteins involved in IM cross-resistance in acute leukemia. Among these proteins, we identified LRPPRC as a potential regulator of ABCB1 transcription via an invMED1 binding site in ABCB1. Interestingly, this invMED1 binding site overlaps with the GC -100 box. In this work, we investigated the potential role of LRPPRC in the regulation of ABCB1 transcriptional activity in CML resistance. In addition, we evaluated the potential connection between this regulation and the methylation status of the ABCB1 promoter in its GC -100 box. Our results show that LRPPRC binds prominently to the ABCB1 promoter in Lucena cells, an IM-resistant cell line. Luciferase assays showed that ABCB1 transcription is positively regulated by LRPPRC upon its knockdown. Pyrosequencing analysis showed that the ABCB1 promoter is differentially methylated at its GC -100 box in K562 cells compared with Lucena cells, and in CML patients with different response to IM. Chromatin immunoprecipitation and Pgp expression after DNA demethylation treatment showed that LRPPRC binding is affected by the methylation status of ABCB1 GC -100 box. Taken together, our findings indicate that LRPPRC is a transcription factor related to ABCB1 expression and highlight the importance of epigenetic regulation in CML resistance.

Validation study of genes with hypermethylated promoter regions associated with prostate cancer recurrence

BACKGROUND

One challenge in prostate cancer is distinguishing indolent from aggressive disease at diagnosis. DNA promoter hypermethylation is a frequent epigenetic event in prostate cancer, but few studies of DNA methylation in relation to features of more aggressive tumors or prostate cancer recurrence have been completed.

METHODS

We used the Infinium HumanMethylation450 BeadChip to assess DNA methylation in tumor tissue from 407 patients with clinically localized prostate cancer who underwent radical prostatectomy. Recurrence status was determined by follow-up patient surveys, medical record review, and linkage with the Surveillance, Epidemiology, and End Results (SEER) registry. The methylation status of 14 genes for which promoter hypermethylation was previously correlated with advanced disease or biochemical recurrence was evaluated. Average methylation level for promoter region CpGs in patients who recurred compared with those with no evidence of recurrence was analyzed. For two genes with differential methylation, time to recurrence was examined.

RESULTS

During an average follow-up of 11.7 years, 104 (26%) patients recurred. Significant promoter hypermethylation in at least 50% of CpG sites in two genes, ABHD9 and HOXD3, was found in tumors from patients who recurred compared with those without recurrence. Evidence was strongest for HOXD3 (lowest P = 9.46 × 10(-6)), with higher average methylation across promoter region CpGs associated with reduced recurrence-free survival (P = 2 × 10(-4)). DNA methylation profiles did not differ by recurrence status for the other genes.

CONCLUSIONS

These results validate the association between promoter hypermethylation of ADHB9 and HOXD3 and prostate cancer recurrence.

IMPACT

Tumor DNA methylation profiling may help to distinguish patients with prostate cancer at higher risk for disease recurrence.

Irreversible perinatal imprinting of adult expression of the principal sex-dependent drug-metabolizing enzyme CYP2C11

We proposed to determine whether, like other sexual dimorphisms, drug metabolism is permanently imprinted by perinatal hormones, resulting in its irreversible sex-dependent expression. We treated newborn male rats with monosodium glutamate (MSG), a total growth hormone (GH) blocker, and, using cultured hepatocytes, examined expression of adult CYP2C11, the predominant cytochrome-P450 expressed only in males, as well as the signal transduction pathway by which episodic GH solely regulates the isoform's expression. In addition, adolescent hypophysectomized (hypox) male rats served as controls in which GH was eliminated after the critical imprinting period. Whereas renaturalization of the masculine episodic GH profile restored normal male-like levels of CYP2C11, as well as CYP2C12, in hepatocytes from hypox rats, the cells derived from the MSG-treated rats were completely unresponsive. Moreover, GH exposure of hepatocytes from hypox rats resulted in normal induction, activation, nuclear translocation, and binding to the CYP2C11 promoter of the signal transducers mediating GH regulation of CYP2C11 expression, which dramatically contrasted with the complete unresponsiveness of the MSG-derived hepatocytes, also associated with hypermethylation of GH-response elements in the CYP2C11 promoter. Lastly, neonatal MSG treatment had no adverse effect on postnatal and adult testosterone levels. The results demonstrate that the sexually dimorphic expression of CYP2C11 is irreversibly imprinted shortly after birth by a hormone other than the customary testosterone, but likely by GH.

BPH and prostate cancer risk

INTRODUCTION

With the exclusion of non-melanomatous skin malignancy, prostate cancer (PCa) is the second most prevalent cancer in men globally. It has been reported that the majority of men will develop benign prostatic hyperplasia (BPH) by the time they reach their 60s. Together, these prostatic diseases have a significant morbidity and mortality affecting over a billion men throughout the world. The risk of developing prostate cancer of men suffering BPH is one that has resulted in a healthy debate amongst the urological community. Here, we try to address this conundrum with clinical and basic science evidence.

MATERIALS AND METHODS

Data from an online search and contemporary data presented at international urological congresses was reviewed.

RESULTS

BPH and PCa can be linked together at a molecular and cellular level on genetic, hormonal, and inflammatory platforms suggesting that these prostatic diseases have common pathophysiological driving factors. Epidemiological studies are weighted towards the presence of BPH having a greater risk for a man to develop PCa in his lifetime; however, a conclusion of causality cannot be confidently stated.

CONCLUSION

The future workload healthcare practitioners will face regarding BPH, and PCa will substantially increase. Further basic science and large epidemiological studies using a global cohort of men are required prior to the urological community confidently counseling their patients with BPH with regards to their PCa risk.

Severe hypoxia induces complete antifolate resistance in carcinoma cells due to cell cycle arrest

Antifolates have a crucial role in the treatment of various cancers by inhibiting key enzymes in purine and thymidylate biosynthesis. However, the frequent emergence of inherent and acquired antifolate resistance in solid tumors calls for the development of novel therapeutic strategies to overcome this chemoresistance. The core of solid tumors is highly hypoxic due to poor blood circulation, and this hypoxia is considered to be a major contributor to drug resistance. However, the cytotoxic activity of antifolates under hypoxia is poorly characterized. Here we show that under severe hypoxia, gene expression of ubiquitously expressed key enzymes and transporters in folate metabolism and nucleoside homeostasis is downregulated. We further demonstrate that carcinoma cells become completely refractory, even at sub-millimolar concentrations, to all hydrophilic and lipophilic antifolates tested. Moreover, tumor cells retained sensitivity to the proteasome inhibitor bortezomib and the topoisomerase II inhibitor doxorubicin, which are independent of cell cycle. We provide evidence that this antifolate resistance, associated with repression of folate metabolism, is a result of the inability of antifolates to induce DNA damage under hypoxia, and is attributable to a hypoxia-induced cell cycle arrest, rather than a general anti-apoptotic mechanism. Our findings suggest that solid tumors harboring a hypoxic core of cell cycle-arrested cells may display antifolate resistance while retaining sensitivity to the chemotherapeutics bortezomib and doxorubicin. This study bears important implications for the molecular basis underlying antifolate resistance under hypoxia and its rational overcoming in solid tumors.

Epigenetic modulation of the drug resistance genes MGMT, ABCB1 and ABCG2 in glioblastoma multiforme

Background

Resistance of the highly aggressive glioblastoma multiforme (GBM) to drug therapy is a major clinical problem resulting in a poor patient’s prognosis. Beside promoter methylation of the O⁶-methylguanine-DNA-methyltransferase (MGMT) gene the efflux transporters ABCB1 and ABCG2 have been suggested as pivotal factors contributing to drug resistance, but the methylation of ABCB1 and ABCG2 has not been assessed before in GBM.

Methods

Therefore, we evaluated the proportion and prognostic significance of promoter methylation of MGMT, ABCB1 and ABCG2 in 64 GBM patient samples using pyrosequencing technology. Further, the single nucleotide polymorphisms MGMT C-56 T (rs16906252), ABCB1 C3435T (rs1045642) and ABCG2 C421A (rs2231142) were determined using the restriction fragment length polymorphism method (RFLP). To study a correlation between promoter methylation and gene expression, we analyzed MGMT, ABCB1 and ABCG2 expression in 20 glioblastoma and 7 non-neoplastic brain samples.

Results

Despite a significantly increased MGMT and ABCB1 promoter methylation in GBM tissue, multivariate regression analysis revealed no significant association between overall survival of glioblastoma patients and MGMT or ABCB1 promoter methylation. However, a significant negative correlation between promoter methylation and expression could be identified for MGMT but not for ABCB1 and ABCG2. Furthermore, MGMT promoter methylation was significantly associated with the genotypes of the MGMT C-56 T polymorphism showing a higher methylation level in the T allele bearing GBM.

Conclusions

In summary, the data of this study confirm the previous published relation of MGMT promoter methylation and gene expression, but argue for no pivotal role of MGMT, ABCB1 and ABCG2 promoter methylation in GBM patients’ survival.

Epigenetic regulation of MDR1 gene through post-translational histone modifications in prostate cancer

BACKGROUND

Multidrug resistance 1 (MDR1) gene encodes for an ATP binding cassette transporter--P-glycoprotein (P-gp)-- involved in chemoresistance to taxanes. MDR1 promoter methylation is frequent in prostate carcinoma (PCa), suggesting an epigenetic regulation but no functional correlation has been established. We aimed to elucidate the epigenetic mechanisms involved in MDR1 deregulation in PCa.

RESULTS

MDR1 promoter methylation and P-gp expression were assessed in 121 PCa, 39 high-grade prostatic intraepithelial neoplasia (HGPIN), 28 benign prostatic hyperplasia (BPH) and 10 morphologically normal prostate tissue (NPT) samples, using quantitative methylation specific PCR and immunohistochemistry, respectively. PCa cell lines were exposed to a DNA methyltransferases inhibitor 5-aza-2'deoxycytidine (DAC) and histone deacetylases inhibitor trichostatin A (TSA). Methylation and histone posttranscriptional modifications status were characterized and correlated with mRNA and protein expression. MDR1 promoter methylation levels and frequency significantly increased from NPTs, to HGPIN and to PCa. Conversely, decreased or absent P-gp immunoexpression was observed in HGPIN and PCa, inversely correlating with methylation levels. Exposure to DAC alone did not alter significantly methylation levels, although increased expression was apparent. However, P-gp mRNA and protein re-expression were higher in cell lines exposed to TSA alone or combined with DAC. Accordingly, histone active marks H3Ac, H3K4me2, H3K4me3, H3K9Ac, and H4Ac were increased at the MDR1 promoter after exposure to TSA alone or combined with DAC.

CONCLUSION

Our data suggests that, in prostate carcinogenesis, MDR1 downregulation is mainly due to histone post-translational modifications. This occurs concomitantly with aberrant promoter methylation, substantiating the association with P-gp decreased expression.

Tumour-suppressive microRNA-874 contributes to cell proliferation through targeting of histone deacetylase 1 in head and neck squamous cell carcinoma

BACKGROUND

Our recent studies of microRNA (miRNA) expression signature demonstrated that microRNA-874 (miR-874) was significantly downregulated in maxillary sinus squamous cell carcinoma (MSSCC), and a putative tumour-suppressive miRNA in human cancers. Our aim of this study was to investigate the functional significance of miR-874 in cancer cells and to identify novel miR-874-mediated cancer pathways and responsible genes in head and neck squamous cell carcinoma (HNSCC).

METHODS

Gain-of-function studies using mature miR-874 were performed to investigate cell proliferation and cell cycle distribution in HNSCC cell lines (SAS and FaDu). To identify miR-874-mediated molecular pathways and targets, we utilised gene expression analysis and in silico database analysis. Loss-of-function assays were performed to investigate the functional significance of miR-874 target genes.

RESULTS

Expression levels of miR-874 were significantly downregulated in HNSCC tissues (including oral, pharyngeal and laryngeal SCCs) compared with normal counterpart epithelia. Restoration of miR-874 in SAS and FaDu cell lines revealed significant inhibition of cell proliferation and induction of G2/M arrest and cell apoptosis. Our expression data and in silico analysis demonstrated that miR-874 modulated the cell cycle pathway. Moreover, histone deacetylase 1 (HDAC1) was a candidate target of miR-874 regulation. Luciferase reporter assays showed that miR-874 directly regulated HDAC1. Silencing of the HDAC1 gene significantly inhibited cell proliferation and induced G2/M arrest and cell apoptosis in SAS cells.

CONCLUSIONS

Downregulation of miR-874 was a frequent event in HNSCC. miR-874 acted as a tumour suppressor and directly targeted HDAC1. Recognition of tumour-suppressive miRNA-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis and suggests novel therapeutic strategies for the disease.

Silencing the EZH2 gene by RNA interference reverses the drug resistance of human hepatic multidrug-resistant cancer cells to 5-Fu

AIMS

The EZH2 gene, which is expressed in various solid tumours, including liver cancer, can regulate gene transcription and promote the generation and progression of tumours. Our aim was to investigate the relationship between EZH2 and multidrug-resistance of human hepatic cancer cells using RNA interference.

MAIN METHODS

We detected the expression of EZH2 in the human hepatic multidrug-resistant cancer cell line Bel/Fu by RT-PCR and western blot; then knocked EZH2 gene by RNA interference to investigate the proliferation, the cell cycle and cell apoptosis by MTT and flow cytometry; finally we checked the alteration of MDR1 methylation and MDR1 expression after EZH2 silencing by MS-PCR, RT-PCR and western blot.

KEY FINDINGS

EZH2 is highly expressed in Bel/Fu cells. After EZH2-depleted Bel/Fu cells were treated with 5-Fu, the cell proliferation was inhibited, the cell cycle arrested at G1, which may be associated with the alteration of G1/S checkpoint regulators, meanwhile the apoptotic rate of the cells increased. Furthermore, the expression of MDR1 decreased and the corresponding methylation levels of MDR1 were significantly increased in EZH2-depleted Bel/Fu cells.

SIGNIFICANCE

We demonstrate the relationship between EZH2 and multidrug-resistance in hepatic cancer for the first time. EZH2 may become a new target for gene therapy to reverse multidrug-resistance in hepatic cancer.

Potential molecular approaches for the early diagnosis of lung cancer (review)

Lung cancer is the leading cause of mortality from cancer among men and women worldwide. More individuals die each year of lung cancer than of colon, breast and prostate cancer combined. Despite new diagnostic techniques, the overall 5-year survival rate remains at approximately 15% and the majority of patients still present with advanced disease. Therefore, lung cancer is the most lethal cancer at present. Diagnosing and treating cancer at its early stages, ideally during the precancerous stages, could increase the 5-year survival rate by 3-4‑fold, with the possibility of cure. To date, no screening method has been shown to decrease the disease-specific mortality rate. This review describes issues related to early lung cancer screening and their rationale, the management of primary cancers detected by screening and the different approaches that have been tested for cancer screening; these include imaging techniques, bronchoscopies and molecular screening, such as analysis of epigenomics using different noninvasive or invasive sources, such as blood, sputum, bronchoscopic samples and exhaled breath.

Even-skipped homeobox 1 is frequently hypermethylated in prostate cancer and predicts PSA recurrence

Background:

DNA methylation is an important epigenetic mechanism in prostate cancer (PCa) progression. Given the role of even-skipped homeobox 1 (EVX1) in the regulation of multiple genes during embryogenesis, we postulated that EVX1 methylation is altered in PCa progression.

Methods:

Bisulphite sequencing and quantitative MethyLight were used to assess methylation in human prostate epithelial cells, four PCa cell lines, liver, lung, spleen, kidney, 35 paired tumour and tumour-associated benign tissues, and 11 normal prostate tissues. Prostate cancer cell lines were treated with 5-azacytidine (AzaC) or trichostatin A (TSA), and expression of EVX1 transcript and variants was assessed by qPCR. Hypermethylation was compared with clinicopathological features in a validation set of 58 patients using microarray.

Results:

Even-skipped homeobox 1 hypermethylation was observed in all four PCa cell lines and 57% of tumours. High-grade tumours exhibited increased methylation compared with intermediate-grade tumours. Even-skipped homeobox 1 expression was induced in PCa cell lines after treatment with AzaC or TSA. In the validation set, 83% of tumours were hypermethylated and hypermethylation was associated with worse recurrence-free survival.

Conclusion:

In this first evaluation of EVX1 methylation in human cancer, EVX1 is one of the most commonly hypermethylated genes observed in PCa and predicted treatment failure in moderate risk patients.

DNA methylation in promoter region as biomarkers in prostate cancer

The prostate gland is the most common site of cancer and the second leading cause of cancer death in American men. Recent emerging molecular biological technologies help us to know that epigenetic alterations such as DNA methylation within the regulatory (promoter) regions of genes are associated with transcriptional silencing in cancer. Promoter hypermethylation of critical pathway genes could be potential biomarkers and therapeutic targets for prostate cancer. In this chapter, we updated current information on methylated genes associated with the development and progression of prostate cancer. Over 40 genes have been investigated for methylation in promoter region in prostate cancer. These methylated genes are involved in critical pathways, such as DNA repair, metabolism, and invasion/metastasis. The role of hypermethylated genes in regulation of critical pathways in prostate cancer is discussed. These findings may provide new information of the pathogenesis, the exciting potential to be predictive and to provide personalized treatment of prostate cancer. Indeed, some epigenetic alterations in prostate tumors are being translated into clinical practice for therapeutic use.

Epigenetic biomarkers in urological tumors: A systematic review

Prostate, bladder, kidney and testis cancers, the most common genitourinary (GU) neoplasms, are generally clinically silent at their earliest stages when curative treatment is most likely successful. However, there are no consensual guidelines for GU cancer screening and available methods are characterized by suboptimal sensitivity and specificity. Moreover, standard clinical and pathological parameters meet with important limitations in the assessment of prognosis in an individual basis. Herein, we focus on the development of epigenetic-based GU cancer biomarkers, which have emerged from exploratory studies in recent years and that hold the promise to revolutionize the clinical management of GU cancer patients.

Expression of MDR1, HIF-1α and MRP1 in sacral chordoma and chordoma cell line CM-319

Background

Chordoma was a typically slow-growing tumor. The therapeutic approach to chordoma had traditionally relied mainly on surgical therapy. And the main reason for therapeutic failure was resistance to chemotherapy and radiotherapy. However the refractory mechanism was not clear. The aim of this study was to investigate the expression of three genes (MDR1, HIF-1α and MRP1) associated with resistance to chemotherapy and radiotherapy in chordoma and chordoma cell line CM-319.

Materials and methods

Using immunohistochemical techniques, the expression of MDR1, HIF-1α and MRP1 was investigated in 50 chordoma specimen. Using RT-PCR and Western blot, the expression of MDR1, HIF-1α and MRP1 was investigated in chordoma and chordoma cell line CM-319.

Results

Expression of MDR1, HIF-1α and MRP1 was observed in 10%, 80% and 74% of all cases, respectively. Expression of MRP1 was correlated with HIF-1α. On the other hand, expression of MDR1 was not correlated with the expression of HIF-1α or MRP1. The expression of HIF-1α and MRP1 was observed, but MDR1 was not observed in chordoma and CM-319.

Conclusion

Expression of HIF-1α and MRP1 was observed in most chordoma specimen and CM-319 cell line; expression of HIF-1α correlated with MRP1. HIF-1α and MRP1 may play a role in the multidrug resistance of chordoma to chemotherapy.

Gene expression correlation analysis predicts involvement of high- and low-confidence risk genes in different stages of prostate carcinogenesis

BACKGROUND

Whole genome association studies have identified many loci associated with the risk of prostate cancer (PC). However, very few of the genes associated with these loci have been related to specific processes of prostate carcinogenesis. Therefore I inferred biological functions associated with these risk genes using gene expression correlation analysis.

METHODS

PC risk genes reported in the literature were classified as having high (P<10(-6)), medium (P<10(-4)), or low (P<10(-2)) statistical confidence. Correlation coefficients of the expression levels between the risk genes and other genes in cancerous prostates samples were compared against those in normal prostates using a microarray dataset from Gene Expression Omnibus.

RESULTS

Overall, significant decrease of correlations in PC was observed between the levels of expression of the high-confidence genes and other genes in the microarray dataset, whereas correlation between low-confidence genes and other genes in PC showed smaller decrease. Genes involved in developmental processes were significantly correlated with all risk gene categories. Ectoderm development genes, which may be related to squamous metaplasia, and genes enriched in fetal prostate stem cells (PSCs) showed strong association with the high-confidence genes. The association between the PSC genes and the low-confidence genes was weak, but genes related to neural system genes showed strong association with low-confidence genes.

CONCLUSIONS

The high-confidence risk genes may be associated with an early stage of prostate carcinogenesis, possibly involving PSCs and squamous metaplasia. The low-confidence genes may be involved in a later stage of carcinogenesis.

Co-expression of CD147 (EMMPRIN), CD44v3-10, MDR1 and monocarboxylate transporters is associated with prostate cancer drug resistance and progression

Background:

The aim of this study is to seek an association between markers of metastatic potential, drug resistance-related protein and monocarboxylate transporters in prostate cancer (CaP).

Methods:

We evaluated the expression of invasive markers (CD147, CD44v3-10), drug-resistance protein (MDR1) and monocarboxylate transporters (MCT1 and MCT4) in CaP metastatic cell lines and CaP tissue microarrays (n=140) by immunostaining. The co-expression of CD147 and CD44v3-10 with that of MDR1, MCT1 and MCT4 in CaP cell lines was evaluated using confocal microscopy. The relationship between the expression of CD147 and CD44v3-10 and the sensitivity (IC₅₀) to docetaxel in CaP cell lines was assessed using MTT assay. The relationship between expression of CD44v3-10, MDR1 and MCT4 and various clinicopathological CaP progression parameters was examined.

Results:

CD147 and CD44v3-10 were co-expressed with MDR1, MCT1 and MCT4 in primary and metastatic CaP cells. Both CD147 and CD44v3-10 expression levels were inversely related to docetaxel sensitivity (IC₅₀) in metastatic CaP cell lines. Overexpression of CD44v3-10, MDR1 and MCT4 was found in most primary CaP tissues, and was significantly associated with CaP progression.

Conclusions:

Our results suggest that the overexpression of CD147, CD44v3-10, MDR1 and MCT4 is associated with CaP progression. Expression of both CD147 and CD44v3-10 is correlated with drug resistance during CaP metastasis and could be a useful potential therapeutic target in advanced disease.

Up-regulation of ABCB1/P-glycoprotein by escaping promoter hypermethylation indicates poor prognosis in hematologic malignancy patients with and without bone marrow transplantation

We investigated the correlation between MDR1 promoter methylation status and MDR1 expression in 228 hematologic malignancies patients and 90 healthy controls. High level of MDR1 mRNA correlated to promoter hypomethylation and strongly associated with poor prognosis indicated by 2-year survival rates, poor CR rate (without BMT) and high relapse rate (with BMT). Furthermore, relative luciferase activity of methylated MDR1 at promoter -50 region was significantly higher than that of the unmethylated. In addition, MDR1 in K562 cells elevated significantly after 5-Aza-dC treatment. In summary, MDR1 promoter hypomethylation conferred its up-regulation and indicated poor prognosis in patients with and without BMT.

Cancer biomarkers: are we ready for the prime time?

A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. In cancer, a biomarker refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker might be either a molecule secreted by a tumor or it can be a specific response of the body to the presence of cancer. Genetic, epigenetic, proteomic, glycomic, and imaging biomarkers can be used for cancer diagnosis, prognosis and epidemiology. These markers can be assayed in non-invasively collected biofluids. However, few cancer biomarkers are highly sensitive and specific for cancer detection at the present time. Consequently, biomarkers are not yet ready for routine use due to challenges in their clinical validation for early disease detection, diagnosis and monitoring to improve long-term survival of patients.

Genistein reverses hypermethylation and induces active histone modifications in tumor suppressor gene B-Cell translocation gene 3 in prostate cancer

BACKGROUND

: B-cell translocation gene 3 (BTG3/ANA/APRO4) is a candidate tumor suppressor gene in some malignancies. We report here that B-cell translocation gene 3 (BTG3) is transcriptionally down-regulated in prostate cancer and the mechanism of inactivation is through promoter hypermethylation.

METHODS

: Prostate cancer and normal cell lines were treated with different doses of genistein and 5-aza-2'-deoxycytidine (5Aza-C). BTG3 messenger ribonucleic acid (mRNA) expression was determined by quantitative real-time polymerase chain reaction in tissues and cell lines. Bisulfate-modified polymerase chain reaction, cloning and sequencing were used to examine promoter methylation in tumor samples and cell lines. Enzyme activity/inhibition assays were done to check the effect of genistein and 5Aza-C on DNA methyltransferases. ChIP assay was performed to analyze chromatin modifications caused by genistein treatment.

RESULTS

: BTG3 mRNA expression was down-regulated in cancer tissues and cells. Genistein and 5Aza-C induced BTG3 mRNA expression in all PC cell lines. Complete methylation of BTG3 promoter in tumor samples and cancer cell lines was observed. Genistein and 5Aza-C treatment significantly decreased promoter methylation, reactivating BTG3 expression. Genistein and 5Aza-C increased levels of acetylated histones 3, 4, histone 3 dimethylated at lysine 4, histone 3 trimethylated at lysine 4, and RNA polymerase II, decreased DNA methyl transferase and methyl-binding domain protein 2 activity, and increased histone acetyl transferase (HAT) activity.

CONCLUSIONS

: This is the first report to show that BTG3 is silenced in prostate cancer and can be reactivated by genistein-induced promoter demethylation and active histone modification. Genistein showed similar effects to that of 5Aza-C, which is currently undergoing phase 2 clinical trials as a treatment for prostate cancer. Because genistein is a natural, nontoxic, and dietary isoflavone, these results indicate that genistein is a novel, advantageous therapeutic agent for treating prostate cancer.

Celecoxib enhanced the sensitivity of cancer cells to anticancer drugs by inhibition of the expression of P-glycoprotein through a COX-2-independent manner

The P-glycoprotein (p170, P-gp) encoded by human MDR1 gene functions as a pump to extrude anticancer drugs from cancer cells. Over-expression of p170 is closely related to primary and induced drug resistance phenotype of tumor cells. Recent studies have demonstrated that expression of cyclooxygenase-2 (COX-2) is positively correlated with the p170 level, suggesting a potential of COX-2 specific inhibitors in regulation of cytotoxicity of anticancer agents. Celecoxib is one of the specific inhibitors of COX-2 and has been widely used in clinic. However, its function in the response of cancer cells to anticancer drugs and the related mechanism are still waiting to be investigated. To explore the correlation of celecoxib and the p170-mediated drug resistance, the role of celecoxib in drug response of cancer cells was analyzed with flow cytometry, high performance liquid chromatography (HPLC), and colony formation experiments. Celecoxib (50 microM) was found to significantly enhance the sensitivity of MCF-7 and JAR/VP16 cells to tamoxifen and etoposide, respectively, by inhibition of p170 expression and increase in intracellular accumulation of the drugs. However, celecoxib did not affect pump function of p170. Enzyme activity and methylation analyses demonstrated that the inhibitory effect of celecoxib on p170 was independent on COX-2 but closely related to hypermethylation of MDR1 gene promoter. Our study suggested that celecoxib was a potential agent for enhancement of the sensitivity of cancer cells to anticancer drugs. It also provided a links between epigenetic change of MDR1 and drug response of cancer cells.

CpG hypomethylation of MDR1 gene in tumor and serum of invasive ductal breast carcinoma patients

OBJECTIVES

Multidrug resistance 1 (MDR1) gene encodes P-glycoprotein (P-gp), a transmembrane calcium-dependent efflux pump, implicated in drug resistance. In this prospective study, methylation status of MDR1 promoter and its correlation with clinicopathological parameters were evaluated in tumor and serum of breast cancer patients.

DESIGN AND METHODS

Methylation-specific PCR was carried out to investigate the promoter methylation status of MDR1 in tumor and serum of 100 patients with invasive ductal carcinomas of breast (IDCs). The effect of promoter methylation on protein expression was evaluated by immunohistochemistry.

RESULTS

MDR1 was hypomethylated in 47% tumors and 44% paired sera of IDC patients and correlated significantly with increased tumor size and advanced tumor stage. Promoter hypomethylation of MDR1 in serum DNA showed 98% specificity and 50% sensitivity.

CONCLUSIONS

Hypomethylation of MDR1 promoter in IDCs accounted for P-gp overexpression and aggressive biologic behavior in a subset of patients. Detection of these epigenetic changes in circulating DNA may not only enhance insight into the biological behavior of the primary tumor of an individual but may also provide valuable information regarding prognosis that can be readily monitored throughout the disease course.

Promoter methylation of glutathione S-transferase pi1 and multidrug resistance gene 1 in bronchioloalveolar carcinoma and its correlation with DNA methyltransferase 1 expression

BACKGROUND

The presence of glutathione S-transferase (GST) pi1 (GSTP1) or multidrug resistance gene 1 (MDR1) promoter methylation in lung cancer was studied for the first time to the authors' knowledge; and, to date, the clinical significance of methylation is not clear. The objective of the current study was to determine the promoter methylation status of GSTP1 and MDR1, which encode GST-pi and P-glycoprotein (Pgp), respectively, in patients with bronchioloalveolar carcinoma (BAC) and to investigate whether methyltransferase 1 (DNMT1)-mediated GSTP1 or MDR1 methylation are responsible for disease progression and prognosis in patients with BAC.

METHODS

Protein expression levels of DNTM1, GST-pi, and Pgp were determined by immunohistochemistry in samples from 36 patients with BAC. Promoter methylation status of the GSTP1 and MDR1 genes was determined by using methylation-specific polymerase chain reaction analysis.

RESULTS

The results demonstrated a significant correlation between the methylation of the GSTP1 or MDR1 promoters and negative expression of their respective proteins in BAC (P < .05). A significant correlation also was demonstrated between GSTP1 methylation and recurrence-free and overall survival of patients with BAC. DNMT1 protein expression levels were correlated with GSTP1 promoter methylation and patient prognosis (P < .05). However, no correlation was observed between DNMT1 expression and MDR1 methylation.

CONCLUSIONS

GSTP1 promoter methylation mediated by DNMT1 may promote BAC progression and could serve as a poor prognostic indicator for patients with this disease. DNMT1 protein expression also may be considered as a prognostic indicator. Methylation of the MDR1 promoter may be mediated through pathways other than DNMT1 in BAC and does not appear to be associated with disease progression or patient prognosis.

Role of hormonal and other factors in human prostate cancer

American men have a lifetime risk of about 18% for prostate cancer diagnosis. Large international variations in prostate cancer risks and increased risks among migrants from low- to high-risk countries indicate important roles for environmental factors. Major known risk factors include age, family history, and country/ethnicity. Type 2 diabetes appears to reduce risk, while high birth weight and adult height are linked to increased risk of aggressive prostate cancer. Limited evidence supports an association with a history of sexually transmitted infections. A previous meta-analysis of eight cohort studies indicated no associations with plasma androgen, estrogen, or sex hormone binding globulin (SHBG) levels. However, there were dose-response relationships with baseline plasma testosterone levels in two studies that adjusted for other serum hormones and obesity. Finasteride (a drug that blocks testosterone activation) reduced prostate cancer risk by 25%. Low-frequency genes linked to familial prostate cancer only explain a small fraction of all cases. Sporadic cases were linked to relatively common polymorphisms of genes involved in (1) androgen synthesis, activation, inactivation and excretion, (2) hormone and vitamin D receptors, (3) carcinogen metabolism, and (4) DNA repair. Epidemiologic evidence supports protective roles for dietary selenium, vitamin E, pulses, tomatoes/lycopene, and soy foods, and high plasma 1,25-dihydroxyvitamin D levels. There is inadequate evidence that vegetables, fruit, carotenoids, and vitamins A and C reduce risk and that animal fat, alpha-linoleic acid, meat, coffee, and tea increase risk. Two major cohort studies found dose-response relationships with dietary calcium intake. Total dietary energy intake may enhance risk. Limited evidence supports a protective role for physical activity and elevated risk for farmers and other men with occupational pesticide exposure, particularly to organochlorine compounds and phenoxy herbicides. There is inadequate evidence for a relationship with alcohol or smoking. Most known or suspected external risk factors may act through hormonal mechanisms, but our review found little supporting evidence, and substantial further research is needed.

CpG island hypermethylation at multiple gene sites in diagnosis and prognosis of prostate cancer

OBJECTIVES

CpG island hypermethylation causes gene silencing and could be decisive in prostate carcinogenesis and progression. We investigated its role at multiple gene sites during prostate carcinogenesis.

METHODS

A quantitative, methylation-specific polymerase chain reaction was used to analyze the hypermethylation patterns at nine gene loci (Annexin2, APC, EDNRB, GSTP1, PTGS2, MDR1, RARbeta, Reprimo, and TIG1) in 80 patients with prostate cancer (PCa) and 26 patients with benign prostatic hyperplasia (BPH).

RESULTS

Hypermethylation was more frequent in PCa than in BPH tissues (EDNRB, 100% versus 88%; TIG1, 96% versus 12%; RARbeta, 95% versus 35%; GSTP1, 93% versus 15%; APC, 80% versus 50%; MDR1, 80% versus 31%; PTGS2, 68% versus 15%; Reprimo, 59% versus 19%; and Annexin2, 4% versus 0%). TIG1 and GSTP1 hypermethylation distinguished between PCa and BPH with a specificity of greater than 85% and sensitivity of greater than 93%. Hypermethylation at a single gene locus did not correlate with any clinicopathologic variables. In contrast, hypermethylation at two genes (eg, APC and TIG1, APC and GSTP1, APC and PTGS2, APC or MDR, GSTP1 or PTGS2) correlated significantly with the pathologic stage and/or Gleason score (P = 0.033 to 0.045). Hypermethylation at APC and Reprimo, as well as DNA hypermethylation at more than five genes, correlated significantly with the rate of prostate-specific antigen recurrence after radical prostatectomy (P = 0.0078 and P = 0.0074, respectively).

CONCLUSIONS

Our results have confirmed that the hypermethylation patterns are helpful in the diagnosis and prognosis of PCa. Increases in CpG island hypermethylation at multiple gene sites occur during PCa progression and indicate early biochemical recurrence after radical prostatectomy.

Cobalamin potentiates vinblastine cytotoxicity through downregulation of mdr-1 gene expression in HepG2 cells

BACKGROUND

P-glycoprotein (Pgp), produced by multidrug resistance-1 gene (mdr-1), is a main mechanism developed by cancer cells to guard against anti-cancer drugs. Alterations of DNA methylation of the mdr-1 gene promoter are known to be linked to mdr-1 gene expression and are probably related to intracellular S-adenosyl-methionine. We here used HepG2 cells to determine the role of the methionine cycle (through the use of the Methionine-Synthase (MS) cofactor, cobalamin) on mdr-1 gene expression.

METHODS

Semiquantitative RT-PCR of mdr-1 gene, cellular retention of rhodamine-123, and vinblastine cytotoxicity were carried out on cells cultivated with and without cobalamin. Methylation status of the mdr-1 gene promoter was determined by methylation-specific PCR.

RESULTS

Addition of cobalamin to the cells led to an increase in MS activity, to a significant decrease in mdr-1 gene expression which is correlated to an increase in retention of the Pgp substrate Rhodamine 123. Furthermore, cobalamin potentiated cell sensitivity to vinblastine to the same range as that of the Pgp blocker verapamil and prevented methotrexate-induced up-regulation of mdr-1 gene expression. However, no modification in methylation of the mdr-1 gene promoter was observed.

CONCLUSION

Cobalamin downregulates mdr-1 gene expression, as well as Pgp expression and function, and significantly increases cytotoxicity of vinblastine. The identification of this novel way of diminishing cellular resistance to the chemotherapeutic agent vinblastine holds promises of leading to better treatments for cancer patients.

Wnt antagonist family genes as biomarkers for diagnosis, staging, and prognosis of renal cell carcinoma using tumor and serum DNA

PURPOSE

We hypothesized that combined methylation analysis of Wnt antagonist genes could serve as a panel of biomarkers for diagnosis, staging, and prognosis in renal cell carcinoma (RCC).

EXPERIMENTAL DESIGN

Samples (n = 62) of RCC and corresponding normal renal tissue (NRT) were analyzed using methylation-specific PCR for methylation of six Wnt antagonist genes (sFRP-1, sFRP-2, sFRP-4, sFRP-5, Wif-1, and Dkk-3). To increase the sensitivity/specificity of RCC detection, the methylation score (M score) for multigene methylation analysis was developed. Receiver operator characteristic curve analysis was used to determine the optimal sensitivity/specificity of the M score. In addition, the M score was compared with the clinicopathologic outcome. Thirty-three serum DNA samples were also used to investigate the methylation status of Wnt antagonist genes.

RESULTS

The methylation levels of all Wnt antagonists were significantly higher in RCC than in NRT. In multivariate regression analysis, the methylation level of sFRP-1 was a significant independent predictor of RCC, whereas for sFRP-2 and sFRP-4 there was a trend toward significance as independent predictors. The M score of Wnt antagonist genes was significantly higher in RCC than in NRT. Overall, the M score had a sensitivity of 79.0% and a specificity of 75.8% (area under the curve, 0.808) as a diagnostic biomarker. In addition, the M score could significantly distinguish grade, pT category, M category, and overall survival of RCC patients. The M score was independent of age and gender in predicting overall survival by the Cox proportional hazards model. In RCC patients, 72.7% of the methylation-specific PCR results had identical methylation in samples of tumor and serum DNA. No serum DNA in normal controls showed aberrant methylation of the Wnt antagonist genes. In addition, the methylation status of Wnt antagonist genes in serum DNA was significantly correlated with tumor grade and stage.

CONCLUSIONS

This is the first report showing that M score analysis of Wnt antagonist genes can serve as an excellent epigenetic biomarker panel for detection, staging, and prognosis of RCC using serum DNA.

Comparative and evolutionary pharmacogenetics of ABCB1: complex signatures of positive selection on coding and regulatory regions

BACKGROUND

As a major mediator in the complex interplay between humans and the xenobiotic environment, the ABCBI transporter gene is an obvious candidate for comparative and evolutionary pharmacogenetic studies. It has been recently reported that common variants in its coding region, which are variously associated with drug response and disease susceptibility, may have conferred differential selective sweep in various populations. Fully profiling the alletic architecture and explicitly interrogating the natural selection at ABCBI are needed to understand its evolutionary population genetics.

METHODS AND RESULTS

Using a comprehensive single nucleotide polymorphism variants in coding and regulatory regions, as well as comparable genotype data from the Environmental Genome Project, we systematically characterized the extent and length of linkage disequilibrium throughout the ABCBI locus in three major ethnic populations (African, European, and Chinese). We observed pronounced signals of recent positive selection on the derived alleles of three common single nucleotide polymorphisms coding regions: e12/1236T, e21/2677T, and e26/3435T in the Chinese, as well as on extended haplotype homozygosity were also observed for two potentially functional common variants in the 5'f/-4489G (rs17149810) in the Chinese and 5'f/-693T (rs3213619) in the Africans, respectively, which may have shaped the phylogenetically inferred star-like haplotype structure of the 5'flanking region.

CONCLUSION

Our finding reveal complex signatures of natural selection on both coding and regulatory regions of the human ABCBI gene, point to potential functional relevance of its regulatory variants, and suggest that evolutionary dynamics and transcriptional regulation may underline the phenotypic variation in xenobiotic disposition and varying predisposition to complex in which xenobiotics play a role.

Regulation and expression of human CYP7B1 in prostate: overexpression of CYP7B1 during progression of prostatic adenocarcinoma

BACKGROUND

Cytochrome P450 (CYP) 7B1 is involved in many metabolic processes including androgen metabolism. Cytochrome P450 (CYP) 7B1 is expressed within the prostate and may determine the levels of the natural estrogen receptor beta (ERbeta) ligand 5alpha-androstane-3beta,17beta-diol (3betaAdiol) available and hence affect the regulation of prostate proliferation. We hypothesized that CYP7B1 expression is increased in prostate tumors and that promoter methylation contributes to the regulation of CYP7B1 expression in human prostate tissue.

METHODS

Expression of the CYP7B1 gene and protein in clinical prostate tissues and prostate cancer cell lines were investigated using real-time PCR and immunohistochemistry. The methylation status of the CYP7B1 gene was analyzed using methylation-specific PCR (MSP).

RESULTS

The immunohistochemical results demonstrate that high expression of CYP7B1 protein occurs in high-grade prostatic intraepithelial neoplasia (PIN) and adenocarcinomas. The ERbeta/CYP7B1 mRNA ratio was significantly lower in tumor compared to the non-tumor area. The MSP analysis indicate that local methylation of CYP7B1 promoter region is an important mechanism involved in down-regulation of CYP7B1 in human prostate tissue.

CONCLUSIONS

This is the first report showing that CYP7B1 is overexpressed in high-grade PIN and in prostate cancer and that local methylation of CYP7B1 promoter region may have significant effect on gene transcription.

Epigenetic modifications of RASSF1A gene through chromatin remodeling in prostate cancer

PURPOSE

The RAS-association domain family 1, isoform A (RASSF1A) gene is shown to be inactivated in prostate cancers. However, the molecular mechanism of silencing of the RASSFIA gene is not fully understood. The present study was designed to investigate the mechanisms of inactivation of the RASSF1A gene through the analysis of CpG methylation and histone acetylation and H3 methylation associated with the RASSF1A promoter region.

EXPERIMENTAL DESIGN

Methylation status of the RASSF1A gene was analyzed in 131 samples of prostate cancer, 65 samples of benign prostate hypertrophy (BPH), and human prostate cell lines using methylation-specific PCR. Histone acetylation (acetyl-H3, acetyl-H4) and H3 methylation (dimethyl-H3-K4, dimethyl-H3-K9) status associated with the promoter region in prostate cells were analyzed by chromatin immunoprecipitation (ChIP) assay.

RESULTS

Aberrant methylation was detected in 97 (74.0%) prostate cancer samples and 12 (18.5%) BPH samples. The methylation frequency of RASSF1A showed a significant increase with high Gleason sum and high stage. The ChIP assays showed enhancement of histone acetylation and dimethyl-H3-K4 methylation on the unmethylated RASSF1A promoter. TSA alone was unable to alter key components of the histone code. However, after 5-aza-2'-deoxy-cytidine treatment, there was a complete reversal of the histone components in the hypermethylated promoter. Levels of acetyl-H3, acetyl-H4, and dimethyl-H3-K4 became more enriched, whereas H3K9me2 levels were severely depleted.

CONCLUSIONS

This is the first report suggesting that reduced histone acetylation or H3K4me2 methylation and increased dimethyl-H3-K9 methylation play a critical role in the maintenance of promoter DNA methylation-associated RASSF1A gene silencing in prostate cancer.

The establishment of two paclitaxel-resistant prostate cancer cell lines and the mechanisms of paclitaxel resistance with two cell lines

BACKGROUND

Although paclitaxel is used for hormone-resistant prostate cancer, relapse definitely occurs later. Details of the molecular mechanism responsible for paclitaxel- resistance remain unclear.

METHODS

We established paclitaxel-resistant cells, DU145-TxR and PC-3-TxR from parent DU145 and PC-3. To characterize these cells, we examined cross-resistance to other anticancer drugs. Expression of several potential genes that had been related to drug-resistance was compared with parent cells by RT-PCR and Western blotting. Methylation analysis of multiple drug resistance (MDR1) promoter was carried out using bisulfite-modified DNA from cell lines. Knockdown experiments using small interfering RNA (siRNA) were also performed to confirm responsibility of drug-resistance. Finally, cDNA microarray was performed to quantify gene expression in PC-3 and PC-3-TxR cells.

RESULTS

The IC(50) for paclitaxel in DU145-TxR and PC-3-TxR was 34.0- and 43.4-fold higher than that in both parent cells, respectively. Both cells showed cross-resistance to some drugs, but not to VP-16 and cisplatin. Methylation analysis revealed that methylated CpG sites of MDR1 promoter in DU145 and PC-3 cells were demethylated in DU145-TxR cells, but not in PC-3-TxR cells. Knockdown of P-glycoprotein (P-gp), which was up-regulated in resistant cells, by MDR-1 siRNA restored paclitaxel sensitivity in DU145-TxR but not in PC-3-TxR, indicating that up-regulation of P-gp was not always main cause of paclitaxel-resistance. Microarray analysis identified 201 (1.34%) up-regulated genes and 218 (1.45%) out of screened genes in PC-3-TxR.

CONCLUSIONS

Our data will provide molecular mechanisms of paclitaxel-resistance and be useful for screening target genes to diagnose paclitaxel sensitivity.

Stress chaperones, mortalin, and pex19p mediate 5-aza-2' deoxycytidine-induced senescence of cancer cells by DNA methylation-independent pathway

DNA demethylating agents are used to reverse epigenetic silencing of tumor suppressors in cancer therapeutics. Understanding of the molecular and cellular factors involved in DNA demethylation-induced gene desilencing and senescence is still limited. We have tested the involvement of two stress chaperones, Pex19p and mortalin, in 5-Aza-2' deoxycytidine (5AZA-dC; DNA demethylating agent)-induced senescence. We found that the cells overexpressing these chaperones were highly sensitive to 5AZA-dC, and their partial silencing eliminated 5AZA-dC-induced senescence in human osteosarcoma cells. We demonstrate that these chaperones modulate the demethylation and chromatin remodeling-dependent (as accessed by p16(INK4A) expression) and remodeling-independent (such as activation of tumor suppressor p53 pathway) senescence response of cells. Furthermore, we found the direct interactions of 5AZA-dC with these chaperones that may alter their functions. We conclude that both mortalin and Pex19p are important mediators, prognostic indicators, and tailoring tools for 5AZA-dC-induced senescence in cancer cells.

Inhibition of the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway decreases DNA methylation in colon cancer cells

The extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK-MAPK) pathway is a critical intermediary for cell proliferation, differentiation, and survival. In the human colon cancer cell line SW1116, treatment with the DNA methyltransferase 1 (DNMT1) inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) or the ERK-MAPK inhibitors PD98059 or rottlerin, or transient transfection with the MAP/ERK kinase (MEK)1/2 small interfering RNA down-regulates DNMT1 and proliferating cell nuclear antigen levels. In this report, we found that drug treatment or small interfering RNA transfection of SW1116 cells induced promoter demethylation of the p16(INK4A) and p21(WAF1) genes, which up-regulated their mRNA and protein expression levels. Flow cytometry revealed that rottlerin treatment induced cell cycle arrest at phase G(1) (p < 0.05). Thus, the ERK-MAPK inhibitor treatment or siRNA-mediated knockdown of ERK-MAPK decreases DNA methylation via down-regulating DNMT1 expression and other unknown mediator(s) in SW1116 colon cancer cells.

Riboregulator H19 induction of MDR1-associated drug resistance in human hepatocellular carcinoma cells

Acquisition of drug resistance is one of the main obstacles encountered in cancer chemotherapy. Overexpression of multi-drug resistance 1 (MDR1) gene and its protein product P-glycoprotein, accompanied with a decrease in doxorubicin accumulation level, was observed in doxorubicin-resistant R-HepG2 cells, a subline derived by selection of human hepatocellular carcinoma HepG2 cells with doxorubicin. In addition, Northern-blot analysis revealed an eight fold upregulation of the imprinted H19 mRNA in R-HepG2 cells. H19 knockdown by transfection with antisense H19 oligonucleotides suppressed the MDR1/P-glycoprotein expression, increased the cellular doxorubicin accumulation level and sensitized doxorubicin toxicity in both HepG2 parent cells and R-HepG2 cells. Results from methylation-specific polymerase chain reaction analysis indicated that the MDR1 gene promoter was hypomethylated in R-HepG2 cells. Antisense H19 oligonucleotides transfection induced a marked increase in the percentage of MDR1 promoter methylation and decrease in MDR1 expression in R-HepG2 cells. Thus, the H19 gene is believed to induce P-glycoprotein expression and MDR1-associated drug resistance at least in liver cancer cells through regulation of MDR1 promoter methylation.

The application of epigenetic modifiers on the treatment of prostate and bladder cancer

Prostate cancer and transitional cell carcinoma (TCC) of bladder are the 2 most common malignancies in the male adult urogenital system. Epigenetic gene silencing, particularly tumor suppressor genes, has become a new area of cancer research. Agents such as deoxyribonucleic acid methyltransferase inhibitors or histone deacetylase inhibitors are epigenetic modifiers that can restore gene expression and alter the malignant phenotype of cancer. They provide a new therapeutic avenue for prostate cancer and TCC. It is also likely that combination regimens using epigenetic modifiers with other classes of agents may have higher therapeutic efficacy for prostate cancer and TCC, especially metastatic and/or refractory cases. We review current knowledge of epigenetic event in prostate cancer and TCC, and discuss the possible clinical implications for these 2 diseases.

Epigenetics of prostate cancer: beyond DNA methylation

Epigenetic mechanisms permit the stable inheritance of cellular properties without changes in DNA sequence or amount. In prostate carcinoma, epigenetic mechanisms are essential for development and progression, complementing, amplifying and diversifying genetic alterations. DNA hypermethylation affects at least 30 individual genes, while repetitive sequences including retrotransposons and selected genes become hypomethylated. Hypermethylation of several genes occurs in a coordinate manner early in carcinogenesis and can be exploited for cancer detection, whereas hypomethylation and further hypermethylation events are associated with progression. DNA methylation alterations interact with changes in chromatin proteins. Prominent alterations at this level include altered patterns of histone modification, increased expression of the EZH2 polycomb histone methyltransferase, and changes in transcriptional corepressors and coactivators. These changes may make prostate carcinoma particularly susceptible to drugs targeting chromatin and DNA modifications. They relate to crucial alterations in a network of transcription factors comprising ETS family proteins, the androgen receptor, NKX3.1, KLF, and HOXB13 homeobox proteins. This network controls differentiation and proliferation of prostate epithelial cells integrating signals from hormones, growth factors and cell adhesion proteins that are likewise distorted in prostate cancer. As a consequence, prostate carcinoma cells appear to be locked into an aberrant state, characterized by continued proliferation of largely differentiated cells. Accordingly, stem cell characteristics of prostate cancer cells appear to be secondarily acquired. The aberrant differentiation state of prostate carcinoma cells also results in distorted mutual interactions between epithelial and stromal cells in the tumor that promote tumor growth, invasion, and metastasis.