DNA hypomethylation of CAGE promotors in squamous cell carcinoma of uterine cervix

HDAC9 and miR-512 Regulate CAGE-Promoted Anti-Cancer Drug Resistance and Cellular Proliferation

Histone deacetylase 9 (HDAC9) is known to be upregulated in various cancers. Cancer-associated antigens (CAGEs) are cancer/testis antigens that play an important role in anti-cancer drug resistance. This study aimed to investigate the relationship between CAGEs and HDAC9 in relation to anti-cancer drug resistance. AGSR cells with an anti-cancer drug-resistant phenotype showed higher levels of CAGEs and HDAC9 than normal AGS cells. CAGEs regulated the expression of HDAC9 in AGS and AGSR cells. CAGEs directly regulated the expression of HDAC9. Rapamycin, an inducer of autophagy, increased HDAC9 expression in AGS, whereas chloroquine decreased HDAC9 expression in AGSR cells. The downregulation of HDAC9 decreased the autophagic flux, invasion, migration, and tumor spheroid formation potential in AGSR cells. The TargetScan analysis predicted that miR-512 was a negative regulator of HDAC9. An miR-512 mimic decreased expression levels of CAGEs and HDAC9. The miR-512 mimic also decreased the autophagic flux, invasion, migration, and tumor spheroid forming potential of AGSR cells. The culture medium of AGSR increased the expression of HDAC9 and autophagic flux in AGS. A human recombinant CAGE protein increased HDAC9 expression in AGS cells. AGSR cells displayed higher tumorigenic potential than AGS cells. Altogether, our results show that CAGE-HDAC9-miR-512 can regulate anti-cancer drug resistance, cellular proliferation, and autophagic flux. Our results can contribute to the understanding of the molecular roles of HDAC9 in anti-cancer drug resistance.

DNA Methylation and Hydroxymethylation in Cervical Cancer: Diagnosis, Prognosis and Treatment

Recent discoveries have led to the development of novel ideas and techniques that have helped elucidate the correlation between epigenetics and tumor biology. Nowadays, the field of tumor genetics has evolved to include a new type of regulation by epigenetics. An increasing number of studies have demonstrated the importance of DNA methylation and hydroxymethylation in specific genes in the progression of cervical cancer. Determining the methylation and hydroxymethylation profiles of these genes will help in the early prevention and diagnosis, monitoring recurrence, prognosis, and treatment of patients with cervical cancer. In this review, we focus on the significance of aberrant DNA methylation and hydroxymethylation in cervical cancer and the use of these epigenetic signatures in clinical settings.

Biological implications and therapeutic significance of DNA methylation regulated genes in cervical cancer

Cervical cancer is the second most common cancer among women worldwide. About 528,000 women are diagnosed with cervical cancer contributing to around 266,000 deaths, across the globe every year. Out of these, the burden of 226,000 (85%) deaths occurs in the developing countries, who are less resource intensive to manage the disease. This is despite the fact that cervical cancer is amenable for early detection due to its long and relatively well-known natural history prior to its culmination as invasive disease. Infection with high risk human papillomavirus (hrHPVs) is essential but not sufficient to cause cervical cancer. Although it was thought that genetic mutations alone was sufficient to cause cervical cancer, the current epidemiological and molecular studies have shown that HPV infection along with genetic and epigenetic changes are frequently associated and essential for initiation, development and progression of the disease. Moreover, aberrant DNA methylation in host and HPV genome can be utilized not only as biomarkers for early detection, disease progression, diagnosis and prognosis of cervical cancer but also to design effective therapeutic strategies. In this review, we focus on recent studies on DNA methylation changes in cervical cancer and their potential role as biomarkers for early diagnosis, prognosis and targeted therapy.

Overexpression of Cancer-Associated Genes via Epigenetic Derepression Mechanisms in Gynecologic Cancer

Like other cancers, most gynecologic cancers are caused by aberrant expression of cancer-related genes. Epigenetics is one of the most important gene expression mechanisms, which contribute to cancer development and progression by regulating cancer-related genes. Since the discovery of differential gene expression patterns in cancer cells when compared with normal cells, extensive efforts have been made to explore the origins of abnormal gene expression in cancer. Epigenetics, the study of inheritable changes in gene expression that do not alter DNA sequence is a key area of this research. DNA methylation and histone modification are well-known epigenetic mechanisms, while microRNAs and alternative splicing have recently been identified as important regulators of epigenetic mechanisms. These mechanisms not only affect specific target gene expression but also regulate the functioning of other epigenetic mechanisms. Moreover, these diverse epigenetic regulations occur simultaneously. Epigenetic regulation of gene expression is extraordinarily complicated and all epigenetic mechanisms to be studied at once to determine the exact gene regulation mechanisms. Traditionally, the contribution of epigenetics to cancer is thought to be mediated through the inactivation of tumor suppressor genes expression. But recently, it is arising that some oncogenes or cancer-promoting genes (CPGs) are overexpressed in diverse type of cancers through epigenetic derepression mechanism, such as DNA and histone demethylation. Epigenetic derepression arises from diverse epigenetic changes, and all of these mechanisms actively interact with each other to increase oncogenes or CPGs expression in cancer cell. Oncogenes or CPGs overexpressed through epigenetic derepression can initiate cancer development, and accumulation of these abnormal epigenetic changes makes cancer more aggressive and treatment resistance. This review discusses epigenetic mechanisms involved in the overexpression of oncogenes or CPGs via epigenetic derepression in gynecologic cancers. Therefore, improved understanding of these epigenetic mechanisms will provide new targets for gynecologic cancer treatment.

DNA hypomethylation of CAGE, MAGE-A1 and MAGE-A3 genes in gastric carcinoma

AIM: To investigate the relationship between the hypomethylation of cancer associated antigen gene (CAGE), melanoma antigen gene A1 (MAGE-A1) and melanoma antigen gene A3 (MAGE-A3) promoters and clinicopathological features of gastric carcinoma.

METHODS: The methylation status of CAGE, MAGE-A1 and MAGE-A3 promoter CpG islands was detected by MSP in 30 gastric carcinoma samples and 25 normal controls. The relationship between hypomethylation of CAGE, MAGE-A1 and MAGE-A3 promoters and clinicopathological features of gastric carcinoma was analyzed.

RESULTS: The rates of hypomethylation of CAGE, MAGE-A1 and MAGE-3 promoters in gastric carcinoma were significantly higher than those in normal controls (80.0% vs 4.0%, 60.0% vs 0.0%, 46.7% vs 8.0%, all P < 0.05). Hypomethylation of CAGE promoter was significantly correlated with lymphatic metastasis and TNM stage (P = 0.016, 0.026), hypomethylation of MAGE-A1 promoter was significantly correlated with tumor differentiation and TNM stage (P = 0.042, 0.002), and hypomethylation of MAGE-A3 promoter was significantly correlated with tumor differentiation and lymphatic metastasis (P = 0.034, 0.026).

CONCLUSION: The hypomethylation of CAGE, MAGE-A1 and MAGE-A3 promoter CpG islands may be used as a biomarker to estimate the differentiation, lymphatic metastasis and TNM stage of gastric carcinoma.

Cancer/testis antigen CAGE exerts negative regulation on p53 expression through HDAC2 and confers resistance to anti-cancer drugs

The role of the cancer/testis antigen CAGE in drug resistance was investigated. The drug-resistant human melanoma Malme3M (Malme3M(R)) and the human hepatic cancer cell line SNU387 (SNU387(R)) showed in vivo drug resistance and CAGE induction. Induction of CAGE resulted from decreased expression and thereby displacement of DNA methyltransferase 1(DNMT1) from CAGE promoter sequences. Various drugs induce expression of CAGE by decreasing expression of DNMT1, and hypomethylation of CAGE was correlated with the increased expression of CAGE. Down-regulation of CAGE in these cell lines decreased invasion and enhanced drug sensitivity resulting from increased apoptosis. Down-regulation of CAGE also led to decreased anchorage-independent growth. Down-regulation of CAGE led to increased expression of p53, suggesting that CAGE may act as a negative regulator of p53. Down-regulation of p53 enhanced resistance to drugs and prevented drugs from exerting apoptotic effects. In SNU387(R) cells, CAGE induced the interaction between histone deacetylase 2 (HDAC2) and Snail, which exerted a negative effect on p53 expression. Chromatin immunoprecipitation assay showed that CAGE, through interaction with HDAC2, exerted a negative effect on p53 expression in Malme3M(R) cells. These results suggest that CAGE confers drug resistance by regulating expression of p53 through HDAC2. Taken together, these results show the potential value of CAGE as a target for the development of cancer therapeutics.

Bisphenol-A exposure in utero leads to epigenetic alterations in the developmental programming of uterine estrogen response

Bisphenol-A (BPA) is a nonsteroidal estrogen that is ubiquitous in the environment. The homeobox gene Hoxa10 controls uterine organogenesis, and its expression is affected by in utero BPA exposure. We hypothesized that an epigenetic mechanism underlies BPA-mediated alterations in Hoxa10 expression. We analyzed the expression pattern and methylation profile of Hoxa10 after in utero BPA exposure. Pregnant CD-1 mice were treated with BPA (5 mg/kg IP) or vehicle control on d 9-16 of pregnancy. Hoxa10 mRNA and protein expression were increased by 25% in the reproductive tract of mice exposed in utero. Bisulfite sequencing revealed that cytosine-guanine dinucleotide methylation was decreased from 67 to 14% in the promoter and from 71 to 3% in the intron of Hoxa10 after in utero BPA exposure. Decreased DNA methylation led to an increase in binding of ER-alpha to the Hoxa10 ERE both in vitro as and in vivo as determined by EMSA and chromatin immunoprecipitation, respectively. Diminished methylation of the ERE-containing promoter sequence resulted in an increase in ERE-driven gene expression in reporter assays. We identify altered methylation as a novel mechanism of BPA-induced altered developmental programming. Permanent epigenetic alteration of ERE sensitivity to estrogen may be a general mechanism through which endocrine disruptors exert their action.

DNA hypomethylation in the origin and pathogenesis of human diseases

The pathogenesis of any given human disease is a complex multifactorial process characterized by many biologically significant and interdependent alterations. One of these changes, specific to a wide range of human pathologies, is DNA hypomethylation. DNA hypomethylation signifies one of the major DNA methylation states that refers to a relative decrease from the "normal" methylation level. It is clear that disease by itself can induce hypomethylation of DNA; however, a decrease in DNA methylation can also have an impact on the predisposition to pathological states and disease development. This review presents evidence suggesting the involvement of DNA hypomethylation in the pathogenesis of several major human pathologies, including cancer, atherosclerosis, Alzheimer's disease, and psychiatric disorders.

Hypermethylation of homeobox A10 by in utero diethylstilbestrol exposure: an epigenetic mechanism for altered developmental programming

Diethylstilbestrol (DES) is a nonsteroidal estrogen that induces developmental anomalies of the female reproductive tract. The homeobox gene HOXA10 controls uterine organogenesis, and its expression is altered after in utero DES exposure. We hypothesized that an epigenetic mechanism underlies DES-mediated alterations in HOXA10 expression. We analyzed the expression pattern and methylation profile of HOXA10 after DES exposure. Expression of HOXA10 is increased in human endometrial cells after DES exposure, whereas Hoxa10 expression is repressed and shifted caudally from its normal location in mice exposed in utero. Cytosine guanine dinucleotide methylation frequency in the Hoxa10 intron was higher in DES-exposed offspring compared with controls (P = 0.017). The methylation level of Hoxa10 was also higher in the caudal portion of the uterus after DES exposure at the promoter and intron (P < 0.01). These changes were accompanied by increased expression of DNA methyltransferases 1 and 3b. No changes in methylation were observed after in vitro or adult DES exposure. DES has a dual mechanism of action as an endocrine disruptor; DES functions as a classical estrogen and directly stimulates HOXA10 expression with short-term exposure, however, in utero exposure results in hypermethylation of the HOXA10 gene and long-term altered HOXA10 expression. We identify hypermethylation as a novel mechanism of DES-induced altered developmental programming.

Epigenetic changes in cancer

Cancer is as much an epigenetic disease as it is a genetic disease, and epigenetic alterations in cancer often serve as potent surrogates for genetic mutations. Normal epigenetic modifications of DNA encompass three types of changes: chromatin modifications, DNA methylation, and genomic imprinting, each of which is altered in cancer cells. This review addresses the various epigenetic modifications that are pervasive among human tumors and traces the history of cancer epigenetics from the first observations of altered global methylation content to the recently proposed epigenetic progenitor model, which provides a common unifying mechanism for cancer development.

Association of GSTM1, GSTT1, and GSTM3 gene polymorphisms and susceptibility to cervical cancer in a North Indian population

OBJECTIVE

The objective of the study was to evaluate the influence of genetic polymorphisms of GSTM1, GSTT1, and GSTM3 on the susceptibility of cervical cancer.

STUDY DESIGN

Blood samples from 150 women with biopsy-confirmed cervical cancer and 168 healthy controls were analyzed by multiplex polymerase chain reaction (PCR) to detect the presence or absence of GSTM1 and GSTT1. Insertion/deletion polymorphism in intron 6 of GSTM3 was determined by PCR.

RESULTS

The frequencies of homozygous GSTM1 null and GSTT1 null genotypes were found to be significantly higher in cancer patients as compared with healthy controls (P = .009, odds ratio [OR] 1.52, 95% confidence interval [CI], 1.1 to 2.0 and P = .0004, OR 2.4, 95% CI: 1.4 to 4.0, respectively). The AB genotype of GSTM3 also conferred higher risk of cancer (P = .053, OR 1.64, 95% CI, 1.0 to 2.6). However, no significant association of at-risk genotypes was observed with any stages of cervical cancer. Interactions among GSTM1 null, GSTT1 null, and AB genotype of GSTM3 resulted in additive predictive risks of cervical cancer. In case-only analysis, carriers of the AA genotype of GSTM3 among tobacco users were at elevated risk of cervical cancer (P = .024, OR 2.1, 95% CI, 1.0 to 4.1) as compared with AB and BB genotypes.

CONCLUSION

GSTM1 null, GSTT1 null, and GSTM3*AB genotypes may confer higher susceptibility to cervical cancer and cancer risk because at-risk genotypes are additive. Tobacco usage by carriers of GSTM3*AA has enhanced the risk of cervical cancer as compared with nonusers.

MethyCancer: the database of human DNA methylation and cancer

Cancer is ranked as one of the top killers in all human diseases and continues to have a devastating effect on the population around the globe. Current research efforts are aiming to accelerate our understanding of the molecular basis of cancer and develop effective means for cancer diagnostics, treatment and prognosis. An altered pattern of epigenetic modifications, most importantly DNA methylation events, plays a critical role in tumorigenesis through regulating oncogene activation, tumor suppressor gene silencing and chromosomal instability. To study interplay of DNA methylation, gene expression and cancer, we developed a publicly accessible database for human DNA Methylation and Cancer (MethyCancer, http://methycancer.genomics.org.cn). MethyCancer hosts both highly integrated data of DNA methylation, cancer-related gene, mutation and cancer information from public resources, and the CpG Island (CGI) clones derived from our large-scale sequencing. Interconnections between different data types were analyzed and presented. Furthermore, a powerful search tool is developed to provide user-friendly access to all the data and data connections. A graphical MethyView shows DNA methylation in context of genomics and genetics data facilitating the research in cancer to understand genetic and epigenetic mechanisms that make dramatic changes in gene expression of tumor cells.

Expressions and significances of Caveolin-1, nm23 and matrix metalloproteinase -2 in gastric carcinomas

AIM: To investigate the protein expression of Caveolin-1, nm23 and matrix metalloproteinase-2 (MMP-2) in normal gastric mucosa, gastric atypical hyperplasia and gastric carcinoma tissues.

METHODS: S-P immunohistochemical method was used to detect the expression of Caveolin-1, nm23 and MMP-2 proteins in normal gastric mucosa (n = 25), gastric atypical hyperplasia (n = 65), and gastric carcinomas (n = 71).

RESULTS: Caveolin-1 and nm23 expression showed a decreasing tendency in normal gastric mucosa, atypical hyperplasia and gastric cancer tissues ordinarily, and there were statistical differences between groups (χ² = 106.303, P < 0.05; χ² = 64.254, P < 0.05). However, MMP-2 expression exhibited a increasing tendency (χ² = 35.247, P < 0.05). Fisher's exact test demonstrated that the expression of Caveolin-1, nm23 and MMP-2 protein were significantly different between the cases with different invasion depths or lymph node metastases (P < 0.05), but not between the cases with different ages, sex and vessel invasions (P > 0.05). Spearman rank correlation analysis indicated that the expression of Caveolin-1 was positively correlated with that of nm23 (r = 0.957, P < 0.05) , but negatively correlated with that of MMP-2 (r = -0.975, P < 0.05). Furthermore, there was a negative correlation between nm23 and MMP-2 expression (r = -0.987, P < 0.05).

CONCLUSION: The absent expression of Caveolin-1 and nm23 together with over-expression of MMP-2 may be one of the important causes for the onset, development and progression of gastric carcinoma. Caveolin-1 may serve as a tumor suppressor gene.