RASSF1A基因与乳腺癌的研究进展

RASSF1是新发现的一种定位于染色体3p的肿瘤抑制基因。该基因存在多种不同的转录本,而RASSF1A是最重要最常见的转录本。它在多种实体肿瘤中如乳腺癌表达缺失,其主要原因是启动子甲基化。启动子甲基化作为肿瘤标记物在乳腺癌的诊断、治疗等方面有着广泛的研究前景和临床价值。     

RASSF1A基因甲基化与妇科肿瘤

ras相关区域家族1A基因(RASSF1A)启动子区域的高甲基化影响了该基因的转录表达,促进了相关肿瘤的发生发展.研究发现,RASSF1A启动子区域高甲基化与子宫颈癌、卵巢癌和子宫内膜癌等的发生密切相关.     

RASSF1A基因与乳腺癌相关性的研究进展

目的:总结RASSF1A基因作为新型的肿瘤抑制因子与乳腺癌发生发展相关性的研究现状,探讨其高甲基化在乳腺癌的早期诊断和治疗方面的研究前景和临床价值.方法:应用PubMed数据库检索系统以“RASSF1A、methylation、breast cancer和epigenetics”为关键词.检索2000-01-2012-08关于RASSF1A基因与乳腺癌相关性研究.纳入标准:1)RASSF1A基因甲基化的相关研究;2)RASSF1A基因高甲基化与乳腺癌相关性的研究.根据纳入标准,符合分析的文献35篇.结果:RASSF1A高甲基化可能是乳腺癌发生和发展中一个早期事件.RASSF1A高甲基化水平在乳腺癌临床诊断中具有较高的阳性率(57％～85％);逆转RASSFIA基因启动子CpG岛高甲基化可成为乳腺癌药物治疗的新方向.RASSF1A基因在乳腺癌诊断和治疗等方面正在得到越来越广泛的研究和应用.结论:RASSF1A基因与乳腺癌的发生发展密切相关,可用于乳腺癌的早期诊断及治疗.     

肿瘤候选抑制基因RASSF1A

新克隆的RASSF1A基因位于3p21.3,是新的肿瘤候选抑制基因,能明显抑制肿瘤细胞生长.RASSF1A失表达见于多种实性肿瘤组织,与RASSF1A启动子甲基化密切相关.RASSF1A启动子甲基化检测可能是很有用的临床指标.     

RASSF1A基因甲基化与非小细胞肺癌预后的相关性研究

背景与目的研究发现在很多肿瘤中均存在RASSF1A基因启动子区域高甲基化状态导致基因表达失活的现象,本研究就RASSF1A基因启动子的甲基化状态与非小细胞肺癌预后的关系进行探讨。方法采用甲基化特异的PCR检测150例非小细胞肺癌和20例肺部良性病变RASSF1A启动子甲基化状态。结果150例非小细胞肺癌中58例发现RASSF1A启动子存在甲基化(58/158,38.7%),20例肺部良性病变中无一例发现RASSF1A启动子甲基化。存在RASSF1A启动子高甲基化的病例预后较未发现RASSF1A甲基化的病例差(P=0.004),Cox回归分析显示RASSF1A启动子的甲基化状态是非小细胞肺癌术后的一个预后相关因素(RR=1.584,95%CI:1.040-2.411,P=0.032)。结论MSP法检测RASSF1A启动子甲基化状态可以作为非小细胞肺癌术后的一个预后评价指标。     

RASSF1A基因甲基化作为肿瘤生物学标志的临床应用

RAS相关区域家族1A基因（rasassociation domain family 1A, RASSF1A）是新近发现的一个位于人染色体3p21.3上的抑癌基因。RASSF1表达的缺失是人类恶性肿瘤中最常见的一个分子事件，目前至少有37种肿瘤存在该基因启动子的甲基化。RASSF1基因启动子CpG岛的甲基化在许多肿瘤组织和肿瘤患者体液中检测到，而在正常组织和体液中罕见，提示它具有肿瘤标志物的特征；RASSF1与其他一些基因组合的甲基化分析有助于卵巢癌、乳腺癌、膀胱癌、肾癌、肺癌等的早期诊断。其次，RASSF1甲基化可作为恶变危险因素的监测，良性增生性病变RASSF1A甲基化的出现往往提示恶变的危险性增高。第三，应用于预后判断，因为某些恶性肿瘤RASSF1A甲基化与患者预后不良相关联。第四，RASSF1A甲基化提供了顺铂和三苯氧胺治疗是否耐药的一个标志，并可在癌症患者整个治疗过程给予监控。总之，RASSF1A甲基化作为肿瘤生物标志物在肿瘤的诊断及其他众多领域有一定的临床应用前景。     

RASSF1A基因甲基化作为肿瘤生物学标志的临床应用

RAS相关区域家族1A基因（ras-association domain family 1A，RASSF1A）是新近发现的一个位于人染色体3p21．3上的抑癌基因。RASSF1表达的缺失是人类恶性肿瘤中最常见的一个分子事件，目前至少有37种肿瘤存在该基因启动子的甲基化。RASSF1基因启动子CpG岛的甲基化在许多肿瘤组织和肿瘤患者体液中检测到，而在正常组织和体液中罕见，提示它具有肿瘤标志物的特征；RASSF1与其他一些基因组合的甲基化分析有助于卵巢癌、乳腺癌、膀胱癌、肾癌、肺癌等的早期诊断。其次，RASSF1甲基化可作为恶变危险因素的监测，良性增生性病变RASSF1A甲基化的出现往往提示恶变的危险性增高。第三，应用于预后判断，因为某些恶性肿瘤RASSF1A甲基化与患者预后不良相关联。第四，RASSF1A甲基化提供了顺铂和三苯氧胺治疗是否耐药的一个标志，并可在癌症患者整个治疗过程给予监控。总之，RASSF1A甲基化作为肿瘤生物标志物在肿瘤的诊断及其他众多领域有一定的临床应用前景。     

肿瘤候选抑制基因RASSF1A

新克隆的RASSF1A基因位于3p21．3，是新的肿瘤候选抑制基因，能明显抑制肿瘤细胞生长。RASSF1A失表达见于多种实性肿瘤组织，与RASSF1A启动子甲基化密切相关。RASSF1A启动子甲基化检测可能是很有用的临床指标。     

RASSF1A基因启动子外周血和组织甲基化在乳腺癌中的意义

目的通过对乳腺癌、癌旁组织及同一患者对应的术前外周血中RASSF1A基因甲基化的检测,加深对乳腺癌发病分子机制的了解并为乳腺癌早期诊断和预后判断提供候选指标。方法采用甲基化特异性PCR方法,分别检测156例乳腺癌患者血浆、肿瘤组织及癌旁正常组织和39例乳腺良性病变血浆及其正常组织中RASSF1A基因启动子甲基化状况。结果早期乳腺癌组织RASSF1A基因启动子甲基化发生率为62.2%(23/37),同一患者外周血甲基化发生率为56.7%(21/37),Kappa值为0.6553(P<0.001),40例血浆RASSF1A甲基化的患者中,37例发生淋巴结转移92.5%(37/40),3例未发生淋巴结转移7.5%(3/40),差异有显著性(P=0.0003);乳腺癌组织和外周血中的RASSF1A甲基化水平与乳腺癌的年龄、家族史、分型、分期、ER、PR、CerbB-2无关;晚期癌复发的86例中,其中癌组织甲基化病例的复发率为25.5%(13/51),癌旁组织甲基化的复发率为75.7%(53/70),两组差异有显著性(P<0.0001)。结论乳腺癌血浆RASSF1A甲基化与组织中的变化较为一致,可作为早期病例筛查和判断淋巴结转移的候选指标之一;晚期乳腺癌癌旁RASSF1A甲基化可能参与肿瘤复发,可作为预测晚期病例预后的候选指标之一。     

宫颈鳞癌组织中RASSF1A基因甲基化状态及其临床意义

背景与目的:Ras相关区域家族1A(ras associated domain family 1A,RASSF1A)基因是一种肿瘤候选抑痛基因,其启动子区高甲基化与多种人类上皮性肿瘤的发生有关.本研究通过检测宫颈鳞癌(cervical squamous cell carcinoma,CSCC)组织中RASSF1A基因启动子区甲基化状态及其蛋白表达情况,旨在分析RASSF1A基因甲基化与基因失活的相关性,并探讨RASSF1A基因甲基化与CSCC发生的关系.方法:分别采用甲基化特异性PCR(methylation-specific PCR,MSP)及免疫组织化学方法检测15例正常宫颈组织和46例CSCC组织中RASSF1A基因的甲基化程度及RASSF1A蛋白的表达情况,并分析RASSF1A基因甲基化与RASSF1A蛋白表达及其与CSCC临床病理特征之间的关系.结果:正常宫颈组织中未见RASSF1A基因甲基化,而CSCC组织中RASSF1A基因甲基化率为43.5%(20/46),两者比较差异具有统计学意义(P＜0.05).CSCC中临床Ⅰ期、Ⅱ期、Ⅲ～Ⅳ期的甲基化阳性率呈逐渐增高趋势(19.0%→58.8%→75.0%,P＜0.05),不同组织学分级、有无淋巴结转移与RASSF1A基因甲基化间未见明显相关性(P＞0.05).RASSF1A基因甲基化与RASSF1A蛋白的表达呈负相关(r=-0.469,P＜0.05).结论:RASSF1A基因启动子区甲基化是导致RASSF1A蛋白低表达的机制之一,可能与CSCC的发生发展有关.     

Epigenetic inactivation of RASSF1A in lung and breast cancers and malignant phenotype suppression

BACKGROUND: The recently identified RASSF1 locus is located within a 120-kilobase region of chromosome 3p21.3 that frequently undergoes allele loss in lung and breast cancers. We explored the hypothesis that RASSF1 encodes a tumor suppressor gene for lung and breast cancers. METHODS: We assessed expression of two RASSF1 gene products, RASSF1A and RASSF1C, and the methylation status of their respective promoters in 27 non-small-cell lung cancer (NSCLC) cell lines, in 107 resected NSCLCs, in 47 small-cell lung cancer (SCLC) cell lines, in 22 breast cancer cell lines, in 39 resected breast cancers, in 104 nonmalignant lung samples, and in three breast and lung epithelial cultures. We also transfected a lung cancer cell line that lacks RASSF1A expression with vectors containing RASSF1A complementary DNA to determine whether exogenous expression of RASSF1A would affect in vitro growth and in vivo tumorigenicity of this cell line. All statistical tests were two-sided. RESULTS: RASSF1A messenger RNA was expressed in nonmalignant epithelial cultures but not in 100% of the SCLC, in 65% of the NSCLC, or in 60% of the breast cancer lines. By contrast, RASSF1C was expressed in all nonmalignant cell cultures and in nearly all cancer cell lines. RASSF1A promoter hypermethylation was detected in 100% of SCLC, in 63% of NSCLC, in 64% of breast cancer lines, in 30% of primary NSCLCs, and in 49% of primary breast tumors but in none of the nonmalignant lung tissues. RASSF1A promoter hypermethylation in resected NSCLCs was associated with impaired patient survival (P =.046). Exogenous expression of RASSF1A in a cell line lacking expression decreased in vitro colony formation and in vivo tumorigenicity. CONCLUSION: RASSF1A is a potential tumor suppressor gene that undergoes epigenetic inactivation in lung and breast cancers through hypermethylation of its promoter region.     

Detection of RASSF1A aberrant promoter hypermethylation in sputum from chronic smokers and ductal carcinoma in situ from breast cancer patients

The newly identified 3p21.3 tumour suppressor gene RASSF1A is methylated in the majority of primary lung tumours, lung tumour cell lines and in a variable percentage of breast tumours. To determine the extent of RASSF1A promoter hypermethylation in early lung tumorigenesis, we analysed sputum samples from lung cancer patients and from current and former smokers using a sensitive methylation-specific PCR (MSP) technique. We also analysed RASSF1A promoter region hypermethylation in trios of normal breast/invasive ductal breast carcinoma/ductal carcinoma in situ (DCIS) from breast cancer patients and DCIS without invasive cancer. We found that 50% of small cell lung cancer (SCLC) and 21% of non-small cell lung cancer (NSCLC) patients had RASSF1A methylation, while one of two former smokers and four of 13 current smokers demonstrated RASSF1A methylation in sputum. Furthermore, two of the four current smokers and one former smoker showing RASSF1A methylation in their sputum developed cancer within 12-14 months of bronchoscopy. In our breast cancer trios, RASSF1A promoter hypermethylation was detected in 65% of invasive cancers, in 42% of corresponding DCIS but in none of the normal breast samples. In addition, we found that three out of 10 DCIS without invasive breast cancer also underwent RASSF1A promoter hypermethylation. Our findings suggest that RASSF1A promoter region hypermethylation may be a useful molecular marker for early detection of lung cancer. Furthermore, since RASSF1A promoter hypermethylation was detected in ductal carcinoma in situ, inactivation of RASSF1A may be an early event in breast tumorigenesis.     

Epigenetic inactivation of RASSF1A candidate tumor suppressor gene at 3p21.3 in brain tumors

The human Ras association domain family 1A (RASSF1A) gene, recently isolated from the lung and breast tumor suppressor locus 3p21.3, is highly methylated in primary lung, breast, nasopharyngeal and other tumors, and re-expression of RASSF1A suppresses the growth of several types of cancer cells. Epigenetic inactivation of RASSF1A by promoter hypermethylation is also important in the development of several human cancers. The methylation status of the promoter region of RASSF1A was analysed in primary brain tumors and glioma cell lines by methylation-specific polymerase chain reaction. In primary brain tumors, 25 of 46 (54.3%) gliomas and five of five (100%) medulloblastomas showed RASSF1A methylation. In benign tumors, only one of 10 (10%) schwannomas and two of 12 (16.7%) meningiomas showed RASSF1A methylation. The RASSF1A promoter region was methylated in all four glioma cell lines. RASSF1A was re-expressed in all methylated cell lines after treatment with the demethylating agent 5-aza-2'-deoxycytidine. Methylation of the promoter CpG islands of the RASSF1A may play an important role in the pathogenesis of glioma and medulloblastoma.     

Expression and promoter methylation of the RASSF1A gene in sporadic breast cancers in Chinese women

The novel tumor suppressor RASSF1A is frequently inactivated during human tumorigenesis by promoter methylation. In this study, we detected the RASSF1A promoter methylation by methylated-specific PCR and investigated RASSF1A gene expression by semi-quantitative RT-PCR and immunohistochemical staining in 36 cases of breast cancer and their adjacent normal tissues in Chinese women. The promoter methylation of the RASSF1A gene was found to be a frequent event in the breast cancers (61.1%). RASSF1A methylation was not found in the matched adjacent normal tissues. The loss frequency of RASSF1A mRNA was 33.3% and that of the RASSF1A protein was 44.4% in breast cancers. RASSF1A mRNA and protein were all expressed in adjacent normal tissues. The mRNA and protein expression level of RASSF1A was significantly lower in breast cancer than in adjacent normal tissue. However, the promoter methylation of the RASSF1A gene in breast cancers were not correlated with clinical parameters, such as ages, histological types, TNM stages and lymph node metastases. Thus, the promoter methylation of RASSF1A was one reason for the low level of RASSF1A mRNA and protein expression and was a frequent event in primary sporadic breast tumorigenesis in Chinese women.     

The RASSF1A tumor suppressor gene is commonly inactivated in adenocarcinoma of the uterine cervix.

PURPOSE: Development of adenocarcinoma (AC) of the uterine cervix, as well as squamous cell carcinoma (SCC), is strongly linked to infection by high-risk human papillomavirus (HPV) types. Human HPV E6 and E7 proteins inactivate the tumor suppressor genes p53 and retinoblastoma, respectively. However, additional genetic alterations may be required to maintain a malignant phenotype. Allelic loss at the short arm of chromosome 3 is one of the most frequent genetic changes found in cervical cancer and various other types of human cancer, including lung, breast, and ovarian cancer. This implies that a resident tumor-suppressor gene in this region is involved in the genesis of these tumors. RASSF1A, which is located at 3p21.3, is rarely inactivated by mutations but has been suggested as a target tumor suppressor gene on the basis of its frequent inactivation through promoter hypermethylation and loss of heterozygosity in a variety of primary human cancers. In the present study, we sought to determine whether epigenetic silencing of RASSF1A caused by hypermethylation of the promoter region plays a role in the development of uterine cervical cancer. Experimental Design: We studied 51 uterine cervical carcinoma samples. These 51 cases were comprised of 31 SCCs and 20 ACs. Real-time methylation-specific PCR system was used for the detection and quantitation of the bisulfite-converted methylated version of the RASSF1A promoter region. The 20 cases of cervical AC were also analyzed for the presence of oncogenic HPV 16 DNA using a PCR-based method. RESULTS: We found complete methylation of the RASSF1A promoter in 45% (9 of 20 samples) of AC cases. There was no promoter methylation observed in any of the 31 cases of SCC. We also correlated RASSF1A promoter hypermethylation to oncogenic HPV 16 infection. HPV 16 DNA was found in 3 of 9 (33%) AC tumors with RASSF1A promoter hypermethylation and 5 of 11 (45%) AC tumors without RASSF1A promoter hypermethylation. We could not demonstrate an inverse correlation between RASSF1A methylation and HPV 16 infection in AC of the uterine cervix. CONCLUSIONS: Hypermethylation of the RASSF1A promoter region is common in AC of the uterine cervix and rare in squamous carcinoma of uterine cervix. HPV infection does not correlate with RASSF1A methylation status in AC of the uterine cervix, but the absence of RASSF1A methylation in SCC of the uterine cervix coupled with the high incidence of HPV 16 infection in this subtype is in accord with previous reports. Our results suggest that epigenetic silencing of RASSF1A may play a role in the development of AC of the uterine cervix.     

Promoter Methylation of BRCA1, DAPK1 and RASSF1A is Associated with Increased Mortality among Indian Women with Breast Cancer

Background: Promoter methylation has been observed for several genes in association with cancer development and progression. Hypermethylation mediated-silencing of tumor suppressor genes (TSGs) may contribute to breast cancer pathogenesis. The present study was conducted to investigate the promoter methylation status of BRCA1, DAPK1 and RASSF1A genes in Indian women with breast cancer. Materials and Methods: Promoter methylation was evaluated in DNA extracted from mononuclear cells (MNCs) in peripheral blood samples of 60 histopathologically confirmed newly diagnosed, untreated cases of breast cancer as well as 60 age and sex matched healthy controls using MS-PCR. Association of promoter methylation with breast cancer-specific mortality was analyzed with Cox proportional hazards models. Kaplan-Meier survival analysis was performed for overall survival of the breast cancer patients. Results: We observed a significant increase of BRCA1, DAPK1 and RASSF1A promoter methylation levels by 51.7% (P <0.001), 55.0% (P <0.001) and 46.6% (P <0.001), respectively, when compared to healthy controls. A strong correlation was noted between hypermethylation of the tumor suppressor genes BRCA1 (P= 0.009), DAPK1 (P= 0.008) and RASSF1A (P= 0.02)) with early and advanced stages of breast cancer patients. We also found that breast cancer-specific mortality was significantly associated with promoter methylation of BRCA1 [HR and 95% CI: 3.25 (1.448-7.317)] and DAPK1 [HR and 95% CI: 2.32 (1.05-5.11)], whereas limited significant link was evident with RASSF1A [HR and 95% CI: 1.54 (0.697-3.413]. Conclusion: Our results suggest that promoter methylation of BRCA1, DAPK1 and RASSF1A genes may be associated with disease progression and poor overall survival of Indian women with breast cancer.     

Role of physical activity in modulating breast cancer risk as defined by APC and RASSF1A promoter hypermethylation in nonmalignant breast tissue.

Physical activity reduces breast cancer risk. Promoter hypermethylation of the tumor suppressor genes APC and RASSF1A, which is potentially reversible, is associated with breast cancer risk. We conducted a cross-sectional study in 45 women without breast cancer to determine the association of physical activity with promoter hypermethylation of APC and RASSF1A in breast tissue. We used quantitative methylation-specific PCR to test the methylation status of APC and RASSF1A, and questionnaires to assess study covariates and physical activity (measured in metabolic equivalent hours per week). In univariate analyses, the study covariate, benign breast biopsy number, was positively associated with promoter hypermethylation of APC (P = 0.01) but not RASSF1A. Mulitvariate logistic regression indicated that, although not significant, physical activities for a lifetime [odds ratio (OR), 0.57; 95% confidence interval (95% CI), 0.22-1.45; P = 0.24], previous 5 years (OR, 0.62; 95% CI, 0.34-1.12; P = 0.11), and previous year (OR, 0.72; 95% CI, 0.43-1.22; P = 0.22) were inversely related to promoter hypermethylation of APC but not RASSF1A for all physical activity measures. Univariate logistic regression indicated that physical activities for a lifetime, previous 5 years, and previous year were inversely associated with benign breast biopsy number, and these results were approaching significance for lifetime physical activity (OR, 0.41; 95% CI, 0.16-1.01; P = 0.05) and significant for physical activity in the previous 5 years (OR, 0.57; 95% CI, 0.34-0.94; P = 0.03). The study provides indirect evidence supporting the hypothesis that physical activity is inversely associated with promoter hypermethylation of tumor suppressor genes, such as APC, in nonmalignant breast tissue.