卵巢癌的DNA甲基化研究进展

卵巢癌是常见的妇科恶性肿瘤,但由于缺乏早期的诊断手段,其病死率居于妇科肿瘤首位。 DNA甲基化是最早发现的表观遗传学改变。RAS相关领域家族基因1（RASSF1A）、乳腺癌易感基因1（BRCA1）和hMLH1等基因的甲基化在卵巢癌的发生、发展中发挥重要作用,通过对这些基因的甲基化检测,可以有助于对卵巢癌的早期诊断。然而,一些基因的甲基化,如hMLH1,可能降低癌细胞对化疗的敏感性。去甲基化药物则可以使得这些甲基化基因发生去甲基化,从而改善化疗效果和患者的预后。综述对卵巢癌主要相关基因的甲基化研究的最新进展。     

组蛋白甲基化修饰在子宫内膜癌中的研究进展

子宫内膜癌是一种子宫内膜上皮源性的恶性肿瘤。雌激素刺激、肥胖、糖尿病、高血压和未孕未产等因素是其发病的高危因素。近年研究发现,表观遗传修饰在子宫内膜癌中起重要作用。随着组蛋白甲基化修饰在子宫内膜癌中的研究逐渐深入,越来越多的研究发现组蛋白甲基化修饰作为基因转录的重要一环具有复杂的生物学行为。组蛋白甲基化相关的酶与癌症的发生密切相关,其可能通过调节启动子、增强子、外显子和重复序列等基因结构的组蛋白甲基化,使下游基因重编程,从而在子宫内膜癌的发生、发展及预后中发挥重要作用。未来有望通过靶向组蛋白甲基化相关的酶来调节基因的生物学行为,从而预防和治疗子宫内膜癌。     

DNA甲基化与卵巢癌耐药关系的研究进展

卵巢癌为女性常见的恶性肿瘤之一,其恶性程度高,预后差。目前卵巢癌患者的化疗策略是基于铂类和紫杉醇的组合。虽然大多数卵巢癌患者对化疗敏感,但仍有许多初始反应者最终发展为化疗耐药。以往的研究认为癌基因激活、抑癌基因失活主要是基因突变、缺失导致的DNA序列改变。而现有研究表明许多肿瘤的重要基因并未发生突变、缺失,基因表达的异常主要通过DNA甲基化实现,且DNA甲基化和其他表观遗传修饰可能是可逆的。这就使得表观遗传因子成为疾病预防和对化疗药物重获敏感性的候选者。大量研究也证实,在耐药和敏感卵巢癌细胞中DNA甲基化水平差异表达。亦有研究使用DNA甲基化酶抑制剂抑制DNA甲基化,以期达到逆转卵巢癌细胞耐药的目的。现综述DNA甲基化与卵巢癌耐药之间的关系。     

Epigenetics makes its mark on women-specific cancers—an opportunity to redefine oncological approaches?

Over the past decade it has become clear that cancer is an epigenetic and a genetic disease. While we have begun to understand the impact of variations in the DNA sequence on cancer development, it is only more recently that we have appreciated the significant contribution of the epigenome to carcinogenesis and cancer biology. Twin studies demonstrate that genetics makes little contribution to the development of women-specific cancers and that the ‘epigenome,’ the interphase between genome and environment, is likely to confer the largest component of risk. Epigenetic factors can therefore act as surrogate markers of disease risk that could potentially facilitate tailored treatment and refine preventive measures. This review focuses attention on DNA methylation—a core epigenetic mechanism that can be readily detected in body fluids and has the potential to substantially reform cancer screening and treatment.     

宫颈脱落细胞中的DNA甲基化研究

在宫颈病变发生、发展的过程中,DNA甲基化水平发生一系列改变。以往的研究多是基于宫颈组织的,而近来检测宫颈脱落细胞甲基化的研究越来越多。与宫颈组织相比,用宫颈脱落细胞作为研究对象进行检测安全无创,更方便临床应用,可能成为筛查、诊断宫颈病变和判断宫颈病变预后的有利工具。讨论研究较多的宫颈脱落细胞中基因的甲基化水平与宫颈病变等级的关系及其临床应用。     

子宫内膜容受性的表观遗传调控机制的研究进展

表观遗传在调控子宫内膜容受性和胚胎植入方面有重要作用。表观遗传学调控参与月经周期子宫内膜再生和增殖、血管形成、植入和蜕膜化。DNA甲基化与EMs发生有关,卵巢癌相关的肿瘤抑制基因的高甲基化导致基因表达沉默,很多与子宫内膜癌相关的肿瘤基因都有异常甲基化变化,进而发生肿瘤。组蛋白修饰参与许多妇科疾病的发生过程,其中部分妇科疾病正是因为改变子宫内膜容受状态进而导致不孕。组蛋白修饰和DNA甲基化之间也可以相互调控,同时组蛋白乙酰化也可以调节DNA甲基化。缺少miRNA的表达与某些人类子宫内膜疾病相关,例如EMs、子宫内膜增生和肿瘤,这些疾病影响子宫内膜的厚度、血流状态、分子表达进而降低子宫内膜的容受性,导致不孕。     

Up-regulation of DNA methyltransferase 3B expression in endometrial cancers

OBJECTIVE: To understand the role of epigenetic regulation in the pathogenesis of endometrial cancer, we have characterized DNA methyltransferase 3B (DNMT3B) gene expression in normal, Grade I and Grade III endometrioid cancers, and examined DNMT3B promoter activities in endometrial cancer cell lines. METHODS: DNMT3B expression was measured in normal, Grade I, and Grade III endometrioid cancer samples. Real-time PCR and Western blot analysis were performed to compare DNMT3B mRNA and protein levels. DNMT3B levels were also compared among endometrial cell lines including those for Ishikawa, KLE, AN3, RL-95, HEC-1A, and HEC-1B. DNMT3B promoter reporter plasmids were constructed. Promoter activities in well and poorly differentiated cell lines were compared by in vitro reporter gene transfection. RESULTS: DNMT3B was significantly up-regulated in both Grade I and Grade III cancers as compared to normal controls. Western blot analysis confirmed the increased DNMT3B protein expression in cancer tissues. It was also found that the well-differentiated endometrial cell line, Ishikawa, expressed lower levels of DNMT3B than the poorly differentiated KLE cells, the expression patterns similar to those observed in tumor specimens. CONCLUSION: The results suggest that DNMT3B overexpression may play a significant role in endometrial cancer development. In addition, the transfection experiments indicated that DNMT3B promoters are more active in the poorly differentiated endometrial cancer cell lines, suggesting that the in vitro assay provides a useful model for studying the DNMT3B transactivation mechanism related to tumor transformation.     

Screening and the prevention of gynecologic cancer: endometrial cancer

Over the years, endometrial cancer has remained the most common gynecologic malignancy in the United States. Two categories of endometrial cancer exist: type I and type II. Type I cancers constitute the majority of cases of endometrial cancer, and the risk factors for this type have been studied in greatest detail. These cancers are driven by estrogen, and many of the risk factors are directly or indirectly linked to a state of excessive estrogen. Protective factors seem to be related to conditions that may result in decreased estrogen exposure. Cure rates for endometrial cancer remain high, mainly because of the early stage at which the majority of cases present. Warning signs of abnormal vaginal bleeding or discharge allow detection of these cancers in their early stages. Screening for these cancers is not effective and often leads to additional unnecessary tests; thus, it is not currently recommended in the general population.     

Hereditary Endometrial Cancer: Lynch Syndrome

Lynch syndrome (hereditary nonpolyposis colorectal cancer [HNPCC]), Cowden syndrome (CS), and Peutz-Jeghers syndrome (PJS) are hereditary diseases with an increased risk for endometrial cancer. Lynch syndrome is the most frequent disease associated with hereditary endometrial cancer. Lynch syndrome is autosomal dominant disorder caused by germ-cell mutation of DNA mismatch repair genes. Patients with Lynch syndrome have a higher risk of endometrial cancer compared with the general population. Thus, these patients and their families may develop malignant tumors, including colon and endometrial cancers. The lifetime risk of endometrial cancer in females with Lynch syndrome is particularly high (28-60 %). Lynch syndrome is a typical hereditary tumor associated with endometrial cancer, and elucidation of the oncogenic mechanism is important to understand the characteristics of endometrial cancer, including sporadic endometrial cancer. The Amsterdam II Criteria are used for screening for Lynch syndrome, but some cases of hereditary endometrial cancer do not meet these criteria (masked Lynch syndrome); therefore, patients with a suspected hereditary predisposition, including juvenile-onset and double cancer, should undergo genetic tests in addition to taking of a family history.     

微小RNA基因的DNA甲基化在卵巢癌中的研究

微小RNA(microRNA,miRNA)是一类短链非编码RNA,通过降解mRNA或抑制mRNA翻译的方式调控众多基因的表达。已有许多研究表明miRNA与卵巢癌的发生、发展、耐药和预后相关。DNA甲基化是表观遗传学的重要组成部分,与细胞的增殖、癌变等生命现象有着重大的关系,是目前肿瘤中研究最多的表观遗传学机制之一,与肿瘤的发生、发展、耐药和预后相关。研究卵巢癌中miRNA基因的DNA甲基化可能为卵巢癌诊治提供新的分子诊断和预后标记物,为化疗耐药分析和个性化治疗提供新的临床思路。     

Opposite alterations of DNA methyltransferase gene expression in endometrioid and serous endometrial cancers

OBJECTIVE: To examine the DNA methyltransferase (DNMT) mRNA and protein levels in endometrioid and serous cancers and to study the relationship between DNA methyltransferase expression and endometrial cancer development. METHODS: Normal endometrium, Grade I and Grade III endometrioid carcinoma tissues and cell lines, as well as serous cancer tissues, were analyzed for DNMT expression. Real-time PCR and Western blot techniques were employed to measure the mRNA and protein levels of the four DNA methyltransferases, DNMT1, DNMT2, DNMT3A, and DNMT3B. Immunohistochemistry was performed to detect alterations in DNMT nuclear localization and spatial organization patterns. RESULTS: While DNMT2 and DNMT3A expression appear to be normal, two- to fourfold increase in DNMT1 and DNMT3B were found in both Grade I and Grade III endometrioid cancers. In addition, the poorly differentiated cell lines expressed relatively higher DNMT levels than well-differentiated cells. In contrast to endometrioid carcinomas, serous cancers expressed substantially lower levels of DNMT1 and DNMT3B than normal controls, with four- and twofold reduction observed in DNMT1 and DNMT3B mRNA levels, respectively. Western blot analysis confirmed opposite expression patterns of DNMT1 and DNMT3B protein in endometrioid and serous cancers. Immunohistochemistry showed normal nuclear localization of DNMT1 and DNMT3B in Type I and Type II cancer specimens as well as cell cultures. CONCLUSION: Two opposite DNMT expression patterns were identified in endometrioid and serous cancers. The concerted upregulation in maintenance and de novo DNA methyltransferases in endometrioid carcinomas is consistent with a tendency for gene-specific hypermethylation observed in this histologic subtype, and may be implicated in tumor suppressor silencing. In contrast, the downregulation of maintenance and de novo DNA methyltransferases in serous cancers suggests that these tumors may contain hypomethylated genomic DNA, which has been associated with a higher mutation rate and is consistent with the known pathogenesis of serous-specific phenotypes. Taken together, the data suggest that divergent DNA methylation pathways may be implicated in the development of Type I and Type II endometrial cancers.     

Lynch Syndrome Screening of Women with Endometrial Cancer: Feasibility and Outcomes in a Community Program

ObjectiveUniversal screening of endometrial cancer for underlying Lynch syndrome (LS) using DNA mismatch repair immunohistochemistry (MMR IHC) has been recommended. The objective of this study was to assess the feasibility and outcomes of using office endometrial samplings in a community LS screening program.MethodsA community laboratory adopted Cancer Care Ontario's LS screening recommendations. All new endometrial cancers in women aged <70 years were screened for LS using MMR IHC and MLH1 promoter methylation testing cascade for MLH1/PMS2-deficient cases. This retrospective validation study analyzes the first year's results.ResultsOf 693 new endometrial cancers, 467 (67.4%) were eligible for LS screening. Both MMR IHC and MLH1 promoter methylation testing were conclusive in >98% of cases. MMR deficiency (MMRd), which includes LS screen-positive cases, was identified in 25.9% of patients (121/467). LS screen-positive tumours comprised 5.9% (27/467) of all cases.ConclusionEndometrial samplings from community practice are suitable for pre-operative LS screening. This testing can identify MMRd endometrial cancers with significant prognostic implications. Approximately 1 in 20 Ontario women <70 years of age with endometrial cancer screen positive for LS. Pre-operative and/or operative assessment for co-existent colonic neoplasms needs to be considered in this high-risk group. In addition, these women should be referred to genetic counselling.     

Diagnostic clinical application of two-color fluorescence in situ hybridization that detects chromosome 1 and 17 alterations to direct touch smear and liquid-based thin-layer cytologic preparations of endometrial cancers

We performed two-color fluorescence in situ hybridization (FISH) on direct touch smears and liquid-based thin-layer (ThinPrep) cytological preparations of endometrial tumors to detect alterations of chromosome 1 and 17 that present with high incidence in endometrial cancers. The DNA probes used for two-color FISH analysis were a combination of the probes designed for 17cen (cCI 17-321) and 17p13.3 (D17S34), and a combination of the probes designed for 1q12 (D1Z1) and 1p36 (cCI1-5335). Numerical or structural alterations of chromosome 1 and/or 17 were detected in 95% (19 of 20 cases) of the direct touch smears obtained from endometrial cancer, while these alterations were also detected in 93% (12 of 13 cases) of samples obtained from grade 1 endometrioid adenocarcinoma cases, including three cases that could not be diagnosed as positive by conventional Papanicolaou cytopathologic staining. Using ThinPrep cytopathologic preparations, numerical or structural abnormalities were found in 26 (90%) and five (100%) cases, respectively, of samples obtained transcervically from 29 endometrial cancer and five atypical endometrial hyperplasia cases. Therefore, two-color FISH may be a useful diagnostic method for endometrial adenocarcinoma and premalignant lesions that demonstrate only slight cellular atypia in conventional cytopathologic preparations.     

Endometrial glandular dysplasia and endometrial intraepithelial neoplasia

PURPOSE OF REVIEW: In recent decades, progress has been made in defining endometrial precancers. Endometrial intraepithelial neoplasia has been widely accepted as a precancer of type I endometrial cancer, while endometrial glandular dysplasia is a newly described entity as a probable precancer of type II cancer. As endometrial intraepithelial neoplasia has been discussed more extensively in the literature, we focus more on the recent development of endometrial glandular dysplasia in this review. RECENT FINDINGS: Serous endometrial intraepithelial carcinoma was previously considered as a putative precancer for endometrial serous carcinoma or uterine papillary serous carcinoma. It is now considered as an early form of endometrial serous carcinoma, however. Endometrial glandular dysplasia was found to be a better candidate for precancer for both endometrial serous and clear cell carcinomas, which meets almost all recently defined criteria for precancer. Biomarkers of p53 and IMP3 are helpful for the early detection of endometrial glandular dysplasia as well as type II endometrial cancers. SUMMARY: Two types of endometrial cancers are derived from two different precancers. Type I endometrioid carcinoma develops from endometrial intraepithelial neoplasia, while type II derives most probably from endometrial glandular dysplasia. Recognition and correct detection of endometrial glandular dysplasia may deepen our understanding and improve prevention and clinical management for type II endometrial cancer.     

DNA content as a prognostic factor in endometrial carcinoma

Two hundred thirty-three cases of endometrial carcinoma were analyzed for DNA content using flow cytometry of cell nuclei extracted from archival paraffin blocks. The median follow-up time for the cases was 8.7 years. Aneuploidy, present in 18% of tumors overall, was associated with adverse histologic type, high grade, and depth of invasion in the uterus. Aneuploidy was not detected in low-grade carcinomas. A DNA index greater than 1.5 strongly predicted death from disease. For endometrial adenocarcinoma and papillary serous carcinoma, this finding appeared independent of stage or tumor grade. The percentage of cells in S phase or G2 + M of the cell cycle did not predict clinical outcome in diploid tumors. Application of DNA analysis to low-stage endometrial cancers of high grade or of papillary serous type may be useful for selecting a subgroup of patients for adjuvant therapy.     

RAS/RAF mutation and defective DNA mismatch repair in endometrial cancers

OBJECTIVE: Defective DNA mismatch repair is a common genetic abnormality in both colon cancers and endometrial cancers. Cancers with defective DNA mismatch repair have the so-called mutator phenotype and accumulate genetic errors at an increased rate. An early mutational target in cells with defect DNA mismatch repair may be the RAS/RAF pathway. Colon cancers often have KRAS2 mutations and, if not KRAS2 mutations, may have BRAF mutations. This study investigated the spectrum and frequency of mutations in BRAF and KRAS2 in endometrial carcinomas on the basis of mismatch repair status. STUDY DESIGN: Four hundred forty-one patients with endometrial cancer were staged properly and graded and evaluated for mismatch repair status. These patients were then stratified to groups by the degree of microsatellite instability that was observed in their tumors. One hundred forty-six of the selected tumors were then evaluated for KRAS2 and BRAF mutations on the basis of their microsatellite instability. RESULTS: One hundred forty-six endometrioid endometrial cancers were evaluated for KRAS2 and BRAF mutations. Thirty-five cancers (24%) had activating KRAS2 mutations, but only a single BRAF mutation was identified in an microsatellite instability-positive cancer. Twenty-four of 81 microsatellite instability high cancers (29.6%) in which the MLH1 repair gene was methylated had KRAS2 mutations. When compared with the other groups, this finding approached statistical significance (P=.06). KRAS2 mutation status was associated with increasing age at diagnosis (P=.02). CONCLUSION: Despite many similarities between colon and endometrial cancers, the mechanism of the development of endometrial cancers appears to be different from colon cancers in that BRAF is not affected by a mismatch repair problem, because only KRAS2 mutations were seen. In addition, increasing age appears to lead to an increased likelihood that such a mutation will occur.     

Estimation of DNA methylation level in endometrial cancer tissues

OBJECTIVES: A level of DNA methylation plays an important role in regulation of cellular gene's expression. Estimation of DNA methylation level in endometrial neoplastic tissues compared to normal endometrial samples was the aim of this study. DESIGN: It was to be shown, that changes in methylation rate in promotory regions could lead to carcinogenesis in particular cell. Authors describe an analysis of DNA methylation level in endometrial cancer tissues compared to DNA methylation level in normal or hyperplastic endometrium. MATERIAL AND METHODS: Endometrial samples from 88 women were collected. 56 of them were classified as adenocarcinoma, 20 as hyperplastic changes, 12 as normal endometrium-control group. DNA was isolated from tissues and than prepared to pm5dC and pdC. Than we performed a statistical analysis of results. RESULTS: The median DNA methylation level was significantly higher in neoplastic tissues than in normal endometrium. There was no difference between DNA methylation level between normal endometrium and hyperplastic changes. CONCLUSIONS: Authors conclude that neoplastic endometrial tissues show high DNA methylation rate compared to normal or hyperplastic endometrium.     

Adjuvante Therapie des Endometriumkarzinoms

In April 2018, the first German interdisciplinary S3 guideline for diagnosis, treatment, and follow-up of patients with endometrial cancer was published. The current article is a summary of chapters 7, “Radiotherapy of endometrial cancer” and 8, “Adjuvant medical treatment of endometrial cancer”, providing readers with a clinically orientated short version. The recommendations for postoperative brachytherapy and external beam radiotherapy as well as for adjuvant progestagen and chemotherapy for type I and II endometrial cancers, including carcinosarcomas, are given.     

表观遗传学与子宫内膜异位症相关性卵巢癌发生机制的研究进展

子宫内膜异位症（endometriosis,EMs）指子宫内膜组织在子宫腔外的存在,是一种慢性的、激素依赖性的妇科疾病,影响着全球数百万女性。虽然EMs在形态学上表现为良性,但其在临床行为学上却表现为增生、浸润、复发等恶性肿瘤的特点。已有充分证据表明EMs可通过多种机制增加恶性转化的风险,但目前关于EMs发生恶性转化的具体机制尚不明确。越来越多证据表明,表观遗传修饰不仅参与EMs的发生,而且在EMs恶性转化的发病机制中发挥重要作用,包括DNA甲基化和去甲基化、组蛋白修饰、微小RNA（microRNAs,miRNAs）异常表达等。综述表观遗传学与子宫内膜异位症相关性卵巢癌（endometriosis associated ovarian cancer,EAOC）发生机制的研究进展,以期寻找可能与EMs恶性转化相关的一些危险因素。