Quantitative analysis of promoter methylation in exfoliated epithelial cells isolated from breast milk of healthy women

Promoter methylation analysis of genes frequently silenced in breast cancer is a promising indicator of breast cancer risk, as these methylation events are thought to occur long before presentation of disease. The numerous exfoliated epithelial cells present in breast milk may provide the breast epithelial DNA needed for detailed methylation analysis and assessment of breast cancer risk. Fresh breast milk samples and health, lifestyle, and reproductive history questionnaires were collected from 111 women. Pyrosequencing analysis was conducted on DNA isolated from the exfoliated epithelial cells immunomagnetically separated from the total cell population in the breast milk of 102 women. A total of 65 CpG sites were examined in six tumor suppressor genes: PYCARD (also known as ASC or TMS1), CDH1, GSTP1, RBP1 (also known as CRBP1), SFRP1, and RASSF1. A sufficient quantity of DNA was obtained for meaningful analysis of promoter methylation; women donated an average of 86 ml of milk with a mean yield of 32,700 epithelial cells per ml. Methylation scores were in general low as expected of benign tissue, but analysis of outlier methylation scores revealed a significant relationship between breast cancer risk, as indicated by previous biopsy, and methylation score for several CpG sites in CDH1, GSTP1, SFRP1, and RBP1. Methylation of RASSF1 was positively correlated with women’s age irrespective of her reproductive history. Promoter methylation patterns in DNA from breast milk epithelial cells can likely be used to assess breast cancer risk. Additional studies of women at high breast cancer risk are warranted.     

Quantitative analysis of promoter methylation in exfoliated epithelial cells isolated from breast milk of healthy women

Promoter methylation analysis of genes frequently silenced in breast cancer is a promising indicator of breast cancer risk, as these methylation events are thought to occur long before presentation of disease. The numerous exfoliated epithelial cells present in breast milk may provide the breast epithelial DNA needed for detailed methylation analysis and assessment of breast cancer risk. Fresh breast milk samples and health, lifestyle and reproductive history questionnaires were collected from 111 women. Pyrosequencing analysis was conducted on DNA isolated from the exfoliated epithelial cells immunomagnetically separated from the total cell population in the breast milk of 102 women. A total of 65 CpG sites were examined in six tumor suppressor genes: PYCARD (also known as ASC or TMS1), CDH1, GSTP1, RBP1 (also known as CRBP1), SFRP1 and RASSF1. A sufficient quantity of DNA was obtained for meaningful analysis of promoter methylation; women donated an average of 86 ml of milk with a mean yield of 32,700 epithelial cells per ml. Methylation scores were in general low as expected of benign tissue, but analysis of outlier methylation scores revealed a significant relationship between breast cancer risk, as indicated by previous biopsy and methylation score, for several CpG sites in CDH1, GSTP1, SFRP1 and RBP1. Methylation of RASS F1 was positively correlated with women''s age irrespective of her reproductive history. Promoter methylation patterns in DNA from breast milk epithelial cells can likely be used to assess breast cancer risk. Additional studies of women at high breast cancer risk are warranted.Key words: biomarker, pyrosequencing, promoter methylation, breast epithelial cells, breast milk, breast cancer risk, parity, age-related promoter methylation, pregnancy-associated protection from breast cancer     

Breast cancer diagnostics based on extracellular DNA and RNA circulating in blood

Extracellular DNA and RNA were extracted from blood plasma and cell surface-bound fractions of healthy women and patients with fibroadenoma and breast cancer. Frequency of methylation of RASSF1A, Cyclin D2, and RARβ2 genes was detected in the extracellular DNA using methylation-specific PCR. Methylation of at least one of these genes was found in plasma of 13% patients with nonmalignant breast fibroadenoma and in 60% of breast cancer patients. Employment cell-surface bound DNA as the substrate for PCR increased the detection frequency of gene methylation up to 87% in patients with fibroadenoma and 95% in breast cancer patients. In clinically healthy women the methylation markers have not been found in extracellular DNA. GAPDH, RASSF8, Ki-67 mRNAs, and 18S rRNA copies were quantified using RT-qPCR of extracellular RNA circulating in blood of patients with breast tumors and healthy controls. The major part of blood extracellular RNA is associated with cell surface. ROC analysis has shown that differences in concentrations 18S RNA, RASSF8, and Ki-67 mRNAs in blood plasma are highly sensitive and specific in discrimination of benign and malignant breast tumors. Thus, analysis of methylated forms of tumor suppressor genes in blood extracellular and quantification of specific extracellular RNA circulating in blood plasma may detect mammary gland tumors and discriminate malignant and benign neoplasms.     

Detection of promoter methylation of tumor suppressor genes in serum DNA of breast cancer cases and benign breast disease controls

Tumors are capable of shedding DNA into the blood stream. This shed DNA may be recovered from serum or plasma. The objective of this study was to evaluate whether pyrosequencing promoter DNA in a panel of 12 breast cancer-related genes (APC, BRCA1, CCND2, CDH1, ESR1, GSTP1, HIN1, P16, RARβ, RASSF1, SFRP1 and TWIST) to measure the degree of methylation would lead to a useful serum-based marker of breast cancer. Serum was obtained from women who were about to undergo a breast biopsy or mastectomy at three hospitals from 1977 to 1987 in Grand Rapids, MI USA. We compared the methylation status of 12 genes in serum DNA obtained from three groups of postmenopausal women (mean age at blood collection: 63.0 y; SD 9.9; range 35–91): breast cancer cases with lymph node-positive disease (n = 241); breast cancer cases with lymph node-negative disease (n = 63); and benign breast disease control subjects (n = 234). Overall, median levels of promoter methylation were low, typically below 5%, for all genes in all study groups. For all genes, median levels of methylation were higher (by 3.3 to 47.6%) in lymph node-positive breast cancer cases than in the controls. Comparing mean methylation level between lymph-node positive cases and controls, the most statistically significant findings, after adjustment of the false-positive rate (q-value), were for TWIST (p = 0.04), SFRP1 (p = 0.16), ESR1 (p = 0.17), P16 (p = 0.19) and APC (p = 0.19). For two of these four genes (TWIST, P16), the median methylation level was also highest in lymph-node positive cases, intermediate in lymph node-negative cases and lowest in the controls. The percent of study subjects with mean methylation scores ≥ 5% was higher among lymph node-positive cases than controls for ten genes, and significantly higher for HIN1 and TWIST (22.0 vs. 12.2%, p = 0.04 and 37.9 vs. 24.5%, p = 0.004, respectively). Despite relatively consistent variation in methylation patterns among groups, these modest differences did not provide sufficient ability to distinguish between cases and controls in a clinical setting.     

Detection of RASSF1A and RAR? Hypermethylation in Serum DNA from Breast Cancer Patients

Breast cancer is fast emerging as the leading cancer amongst females, especially in young females in metropolitan cities in India. The epigenetic alterations involved in the onset and progression of breast cancer may serve as biomarkers for early detection and prognosis of the disease. Furthermore, using body fluids such as serum offers a non-invasive method to procure multiple samples for such analyses. In this study, we examined methylation status of two normally unmethylated but biologically significant cancer genes, RAS association domain family protein 1A (RASSF1A) and Retionic acid receptor ? (RAR?) by Methylation Specific PCR (MSP) in invasive ductal carcinomas of the breast and paired serum DNA. RASSF1A was found to be methylated in 17 of 20 (85%) breast tumors; while sera from 15 of 20 (75%) of the patients showed concordant methylated RASSF1A, with a sensitivity of 88%. RAR? was methylated in 2/20 (10%) breast tumors. A gene unmethylated in the tumor DNA was always found to be unmethylated in the matched serum DNA for both RASSF1A and RAR? genes; hence specificity was 100%. Immunohistochemical analysis of RAR? protein in 15 breast carcinoma patients harboring unmethylated RAR? in tumors and serum DNA showed the expression of RAR? protein in tumors and paired normal breast tissues, confirming the MSP findings, suggesting that RAR? promoter is functional in these cases. This study underscores the potential utility of DNA methylation based screening of serum, a readily accessible body fluid, as a surrogate marker for early detection of breast cancer.      

Increased promoter methylation in exfoliated breast epithelial cells in women with a previous breast biopsy

Accurately identifying women at increased risk of developing breast cancer will provide greater opportunity for early detection and prevention. DNA promoter methylation is a promising biomarker for assessing breast cancer risk. Breast milk contains large numbers of exfoliated epithelial cells that are ideal for methylation analyses. Exfoliated epithelial cells were isolated from the milk obtained from each breast of 134 women with a history of a non-proliferative benign breast biopsy (Biopsy Group). Promoter methylation of three tumor suppressor genes, RASSF1, SFRP1 and GSTP1, was assessed by pyrosequencing of bisulfite-modified DNA. Methylation scores from the milk of the 134 women in the Biopsy Group were compared to scores from 102 women for whom a breast biopsy was not a recruitment requirement (Reference Group). Mean methylation scores for RASSF1 and GSTP1 were significantly higher in the Biopsy than in the Reference Group. For all three genes the percentage of outlier scores was greater in the Biopsy than in the Reference Group but reached statistical significance only for GSTP1. A comparison between the biopsied and non-biopsied breasts of the Biopsy Group revealed higher mean methylation and a greater number of outlier scores in the biopsied breast for both SFRP1 and RASSF1, but not for GSTP1. This is the first evidence of CpG island methylation in tumor suppressor genes of women who may be at increased risk of developing breast cancer based on having had a prior breast biopsy.     

Global and gene-specific promoter methylation analysis in primary hyperparathyroidism

Epigenetic mechanisms involved in primary hyperparathyroidism are poorly understood as studies are limited. In order to understand the role of aberrant DNA promoter methylation in the pathogenesis of parathyroid tumors, we have quantified the CpG island promoter methylation density of several candidate genes including APC (promoter 1A and 1B), β-catenin (CTNNB1), CASR, CDC73/HRPT2, MEN1, P16 (CDKN2A), PAX1, RASSF1A, SFRP1 and VDR in 72 parathyroid tumors and 3 normal parathyroid references using bisulfite pyrosequencing. Global methylation levels were assessed for LINE-1. We also compared methylation levels with gene expression levels measured by qRT-PCR for genes showing frequent hypermethylation. The adenomas displayed frequent hypermethylation of APC 1A (37/66; 56%), RASSF1A (34/66; 52%) and β-catenin (19/66; 29%). One of the three atypical adenomas was hypermethylated for APC 1A. The three carcinomas were hypermethylated for RASSF1A and SFRP1, and the latter was only observed in this subtype. The global methylation density was similar in tumors (mean 70%) and parathyroid reference samples (mean 70%). In general, hypermethylated genes had reduced expression in the parathyroid adenomas using qRT-PCR. Among the adenomas, methylation of APC 1A correlated with adenoma weight (r = 0.306, p < 0.05). Furthermore, the methylation status of RASSF1A correlated with each of APC 1A (r = 0.289, p < 0.05) and β-catenin (r = 0.315, p < 0.01). Our findings suggest a role for aberrant DNA promoter methylation of APC 1A, β-catenin and RASSF1A in a subset of parathyroid tumors.     

Impact of Hyperhomocysteinemia on Breast Cancer Initiation and Progression: Epigenetic Perspective

Our recent study showing association of hyperhomocysteinemia and hypomethioninemia in breast cancer and other studies indicating association of hyperhomocysteinemia with metastasis and development of drug resistance in breast cancer cells treated with homocysteine lead us to hypothesize that homocysteine might modulate the expression of certain tumor suppressors, i.e., RASSF1, RARβ1, CNND1, BRCA1, and p21, and might influence prognostic markers such as BNIP3 by inducing epigenetic alteration. To demonstrate this hypothesis, we have treated MCF-7 and MDA-MB-231 cells with different doses of homocysteine and observed dose-dependent inhibition of BRCA1 and RASSF1, respectively. In breast cancer tissues, we observed the following expression pattern: BNIP3 > BRCA1 > RARβ1 > CCND1 > p21 > RASSF1. Hyperhomocysteinemia was positively associated with BRAC1 hypermethylation both in breast cancer tissue and corresponding peripheral blood. Peripheral blood CpG island methylation of BRCA1 in all types of breast cancer and methylation of RASSF1 in ER/PR-negative breast cancers showed positive correlation with total plasma homocysteine. The methylation of RASSF1 and BRCA1 was associated with breast cancer initiation as well as progression, while BRCA1 methylation was associated with DNA damage. Vitamin B₁₂ showed inverse association with the methylation at both the loci. RFC1 G80A and cSHMT C1420T variants showed positive association with methylation at both the loci. Genetic variants influencing remethylation step were associated positively with BRCA1 methylation and inversely with RASSF1 methylation. GCPII C1561T variant showed inverse association with BRCA1 methylation. We found good correlation of BRAC1 (r = 0.90) and RASSF1 (0.92) methylation pattern between the breast cancer tissue and the corresponding peripheral blood. To conclude, elevated homocysteine influences methionine dependency phenotype of breast cancer cells and is associated with breast cancer progression by epigenetic modulation of RASSF1 and BRCA1 .     

Detection of promoter methylation of tumor suppressor genes in serum DNA of breast cancer cases and benign breast disease controls

Tumors are capable of shedding DNA into the blood stream. This shed DNA may be recovered from serum or plasma. The objective of this study was to evaluate whether pyrosequencing promoter DNA in a panel of 12 breast cancer-related genes (APC, BRCA1, CCND2, CDH1, ESR1, GSTP1, HIN1, P16, RARβ, RASSF1, SFRP1 and TWIST) to measure the degree of methylation would lead to a useful serum-based marker of breast cancer. Serum was obtained from women who were about to undergo a breast biopsy or mastectomy at three hospitals from 1977 to 1987 in Grand Rapids, MI USA. We compared the methylation status of 12 genes in serum DNA obtained from three groups of postmenopausal women (mean age at blood collection: 63.0 y; SD 9.9; range 35–91): breast cancer cases with lymph node-positive disease (n = 241); breast cancer cases with lymph node-negative disease (n = 63); and benign breast disease control subjects (n = 234). Overall, median levels of promoter methylation were low, typically below 5%, for all genes in all study groups. For all genes, median levels of methylation were higher (by 3.3 to 47.6%) in lymph node-positive breast cancer cases than in the controls. Comparing mean methylation level between lymph-node positive cases and controls, the most statistically significant findings, after adjustment of the false-positive rate (q-value), were for TWIST (p = 0.04), SFRP1 (p = 0.16), ESR1 (p = 0.17), P16 (p = 0.19) and APC (p = 0.19). For two of these four genes (TWIST, P16), the median methylation level was also highest in lymph-node positive cases, intermediate in lymph node-negative cases and lowest in the controls. The percent of study subjects with mean methylation scores ≥ 5% was higher among lymph node-positive cases than controls for ten genes, and significantly higher for HIN1 and TWIST (22.0 vs. 12.2%, p = 0.04 and 37.9 vs. 24.5%, p = 0.004, respectively). Despite relatively consistent variation in methylation patterns among groups, these modest differences did not provide sufficient ability to distinguish between cases and controls in a clinical setting.     

Investigation of tumor-derived extracellular DNA in blood of cancer patients by methylation-specific PCR

The frequency of APC, RASSF1A, RARbeta, CDH1 and CDH13 gene promoter methylation in samples of DNA isolated from breast and lung patient plasma was studied in order to develop the noninvasive tumor-specific DNA detection method. Methylation of at least one of genes was detected in extracellular DNA from most of the cancer blood specimens. The results obtained indicate that promoter hypermethylation of a number of marker genes represents a promising serum marker for early breast and lung cancer detection.     

Clinical significance of promoter hypermethylation of RASSF1A, RARbeta2, BRCA1 and HOXA5 in breast cancers of Indian patients

Promoter hypermethylation of genes is implicated in the pathogenesis of many cancers, including breast cancer. Herein, we analyzed the promoter methylation status of a panel of critical growth regulatory genes, RASSF1A, RARbeta2, BRCA1 and HOXA5, in 54 breast cancers and 5 distant normal breast tissues of Indian patients. The methylation data were correlated with clinicopathological characteristics and hormone receptor status to determine the impact of methylation in breast carcinogenesis. Promoter hypermethylation of RASSF1A was observed in 39/54 (72%), HOXA5 in 36/54 (67%), BRCA1 in 15/54 (28%) and RARbeta2 in 8/54 (15%) breast cancers. Our most significant findings were the association of RASSF1A methylation with nodal metastasis (p=0.05); and RARbeta2 methylation with age (all tumors in patients in the older age group were methylated, p=0.04). Further, the interactions between DNA methylation and hormone receptor biology in breast cancer cells are beginning to be clearly understood. In this context the association of HOXA5 methylation with loss of ERalpha (p=0.009) is noteworthy.     

Methylation of the Putative Tumor Suppressor Gene RASSF1A in Primary Cervical Tumors

Methylation-sensitive restriction endonuclease analysis (MSRA) followed by polymerase chain reaction (PCR) have been used to estimate the methylation level of 13 CpG dinucleotides in the promoter region of the putative suppressor gene RASSF1A (3p21.31) in squamous cell carcinomas of the uterine cervix (SCCs) carrying human papillomavirus (HPV) types 16, 18, and related types. Methylation of 3 to 13 CpG pairs has been found in 64% (25 out of 39) tumor DNA samples, 22% (2 out of 9) DNA samples from morphologically normal tissues adjacent to the tumor (P = 0.0306), and two out of three DNA samples from peripheral blood leukocytes of carcinoma patients. These CpG pairs are not methylated in the DNA of leukocytes of healthy donors (0 out of 10). The methylation level of the RASSF1A promoter region studied in tumors of the patients with regional lymph node metastases is significantly higher than in tumors of the patient that have no metastases (P = 8.5 × 10^–12). The methylation frequency of gene RASSF1A is two times higher than the frequency of hemi- and homozygous deletions in the chromosome 3 region where the gene is located. The data obtained indicate that methylation is one of the main mechanisms of the RASSF1A gene inactivation in HPV-positive human cervical tumors. The methylation of this gene may be an early event in the genesis of cervical tumors, the methylation level increasing with tumor progression.     

肺癌与DNA 甲基化研究的进展

DNA甲基化是表观遗传学研究的重要内容。其本质是在甲基转移酶的催化下,DNA的CG两个核苷酸的胞嘧啶被选择性地添加甲基,形成5’甲基胞嘧啶的过程。CpG岛是DNA甲基化常发生的部位。CpG岛指基因组中长度为300～3000 bp的富含CpG二核苷酸的一些区域,主要存在于基因的5’区域。以往的研究表明,肺癌的发生常与CpG岛的异常甲基化有关。多基因异常的甲基化常为肿瘤发生的重要机制。近年来,研究比较热门的基因有p16、RASSF1A、CDH1、CDH13、FHTI、TMS1/ASC等。研究集中在肺癌组织与癌旁组织甲基化频率的统计分析,以及对于血液,痰液,肺泡灌洗液发生甲基化频率的统计分析。对于肺癌相关抑癌基因甲基化的研究,为肺癌患者的早期诊断提供思路,并为治疗开辟新的方向。去甲基化治疗虽研究较少,但目前已取得一定进展。     

Prognostic potential of <Emphasis Type="Italic">KLOTHO</Emphasis> and <Emphasis Type="Italic">SFRP1</Emphasis> promoter methylation in head and neck squamous cell carcinoma

Hypermethylation in the CpG island promoter regions of tumor suppressors is known to play a significant role in the development of HNSCC and the detection of which can aid the classification and prognosis of HNSCC. This study aims to profile the methylation patterns in a panel of key genes including CDKN2A, CDKN2B, KLOTHO (KL), RASSF1A, RARB, SLIT2, and SFRP1, in a group of HNSCC samples from Saudi Arabia. The extent of methylation in these genes is determined using the MethyLight assay and correlated with known clinicopathological parameters in our samples of 156 formalin-fixed and paraffin-embedded HNSCC tissues. SLIT2 methylation had the highest frequency (64.6%), followed by RASSF1A (41.3%), RARB (40.7%), SFRP1 (34.9), KL (30.7%), CKDN2B (29.6%), and CKDN2A (29.1%). KL and SFRP1 methylation were more predominant in nasopharyngeal tumors (P = 0.001 and P = 0.031 respectively). Kaplan Meier analysis showed that patients with moderately differentiated tumors who display SFRP1 methylation have significantly worse overall survival in comparison with other samples. In contrast, better clinical outcomes were seen in patients with KL methylation. In conclusion, our findings suggest that the detection of frequent methylation in SFRP1 and KL genes’ promoters could serve as prognostic biomarkers for HNSCC.     

SFRP1 CpG island methylation locus is associated with renal cell cancer susceptibility and disease recurrence

Loss of the secreted Fzd-related protein 1 (SFRP1) and concurrent alteration of the SFRP1/WNT pathway are frequently observed in human cancers such as in renal cell cancer (RCC). Whether methylation of a SFRP1 CpG island locus in normal human solid tissues is associated with increased tissue specific cancer risk has not been determined to date. Here we measure the cancer risk attributable to SFRP1 DNA methylation in renal tissue. Pyrosequencing of bisulfite treated DNA was used for a case-control study including 120 normal-appearing renal tissues of autopsy specimens and 72 normal-appearing tissues obtained from tumor adjacent areas, and a cross sectional study of 96 RCCs. Association of methylation with demographic risk factor age, clinicopathological parameters and course of patients was investigated. We show significant hypermethylation of a SFRP1 CpG island locus in normal-appearing renal tissues from RCC patients compared with normal-appearing autopsy kidney tissues. Inter quartile analysis revealed a 6-, 13- and 11-fold increased cancer risk for the second, third and fourth quartiles of methylation in the age matched subgroup of tissues (p = 0.001, p = 1.3E-6, p = 6.9E-6). Methylation in autopsy tissues increased with age and methylation in tumors was an independent predictor of recurrence free survival. SFRP1 DNA methylation, accumulates with age in normal-appearing kidney tissues and is associated with increased renal cancer risk, suggesting this CGI sub region as an epigenetic susceptibility locus for RCC. Our data underline the need to further analyze the tissue specific risks conferred by methylated loci for the development of human cancers.     

Decreased expression of EZH2 reactivates RASSF2A by reversal of promoter methylation in breast cancer cells

EZH2, the catalytic subunit of polycomb repressor complex 2, has oncogenic properties, whereas RASSF2A, a Ras association domain family protein, has a tumor suppressor role in many types of human cancer. However, the interrelationship between these two genes remains unclear. Here, we showed that the downregulation of EZH2 reduces CpG island methylation of the RASSF2A promoter, thereby leading to increased RASSF2A expression. Our findings also showed that knockdown of EZH2 increased RASSF2A expression in the human breast cancer cell line MCF‐7 in cooperation with DNMT1. This was similar to the effect of 5‐Aza‐CdR, a DNA methylation inhibitor that reactivates tumor suppressor genes and activated RASSF2A expression in our study. The EZH2 inhibitor DZNep markedly suppressed the proliferation, migration, and invasion of MCF‐7 cells treated with ADR and TAM. EZH2 inhibits the expression of tumor suppressor gene RASSF2A via promoter hypermethylation. Thus, it plays an important role in tumorigenesis and is a potential therapeutic target for the treatment of breast cancer.     

A ligation assay for multiplex analysis of CpG methylation using bisulfite-treated DNA

Aberrant methylation of promoter CpG islands is causally linked with a number of inherited syndromes and most sporadic cancers, and may provide valuable diagnostic and prognostic biomarkers. In this report, we describe an approach to simultaneous analysis of multiple CpG islands, where methylation-specific oligonucleotide probes are joined by ligation and subsequently amplified by polymerase chain reaction (PCR) when hybridized in juxtaposition on bisulfite-treated DNA. Specificity of the ligation reaction is achieved by (i) using probes containing CpGpCpG (for methylated sequences) or CpApCpA (for unmethylated sequences) at the 3′ ends, (ii) including three or more probes for each target, and (iii) using a thermostable DNA ligase. The external probes carry universal tails to allow amplification of multiple ligation products using a common primer pair. As proof-of-principle applications, we established duplex assays to examine the FMR1 promoter in individuals with fragile-X syndrome and the SNRPN promoter in individuals with Prader-Willi syndrome or Angelman syndrome, and a multiplex assay to simultaneously detect hypermethylation of seven genes (ID4, APC, RASSF1A, CDH1, ESR1, HIN1 and TWIST1) in breast cancer cell lines and tissues. These data show that ligation of oligonucleotide probes hybridized to bisulfite-treated DNA is a simple and cost-effective approach to analysis of CpG methylation.     

巢式甲基化特异性PCR检测肝细胞癌患者血清中RASSF1A和CDH13基因启动子区甲基化

为了检测肝细胞癌患者血清中RASSF1A和CDH13基因启动子的甲基化状态,收集肝细胞癌患者及健康对照者的血清标本,采用巢式甲基化特异性PCR(nMSP)法检测RASSF1A和CDH13基因启动子区甲基化状态.结果肝细胞癌患者血清样品中RASSF1A和CDH13基因启动子区甲基化率为53.12%和31.25%,68.75%的患者血清可以检测到异常甲基化,正常对照血清中未检测到RASSF1A和CDH13基因启动子区甲基化,RASSF1A和CDH13基因甲基化与患者的临床病理资料无明显相关性(P>0.05);表明nMSP法检测血清中RASSF1A和CDH13基因启动子区甲基化具有较高的敏感性,可为肝细胞癌的筛查、早期诊断和预后判断提供有价值的信息.