Differences in loss of p16INK4 protein expression by promoter methylation between left- and right-sided primary colorectal carcinomas

The p16INK4 gene, encoding a cyclin-dependent kinase inhibitor, is frequently methylated in colorectal cancer, and a side-specific methylation frequency was suggested. To clarify the frequency of real loss of tumor suppressor function dependent on anatomical localization, we investigated 43 primary colorectal carcinomas by determining aberrant promoter methylation using methylation-specific PCR. In addition, we evaluated the p16INK4 protein expression immunohistochemically. P16INK4 methylation was found in 18 of 43 (41.9%) cases. Fourteen of 43 cases (32.6%) were negative for p16INK4 protein, whereas 10 of these 14 cases showed methylation of the promoter region of the p16INK4 gene. Methylation of the promoter region was significantly correlated with loss of p16INK4 protein (p<0.01). P16INK4 tumor suppressor inactivation was significantly correlated with proximal location (p=0.031 for methylation and p=0.028 for immunostaining). The groups characterized by tumors with and without aberrant promoter methylation or loss of p16INK4 immunostaining showed no significant difference in either Dukes' stage and grade or age and gender. This is further evidence that p16INK4 methylation causes gene silencing. Loss of p16INK4 tumor suppressor function in colorectal tumors was associated with proximal location in the gut.     

Promoter methylation and immunohistochemical expression of hMLH1 and hMSH2 in sporadic colorectal cancer: a study from India

To determine the etiological factors of human colorectal cancer (CRC) we assessed the frequency and prognostic significance of hMLH1 and hMSH2 genes in conjunction with hMLH1 and hMSH2 protein expression in 30 Indian CRC patients. The protein expression and promoter methylation of hMLH1 and hMSH2; Mismatch Repair genes (MMR) were analyzed by immunohistochemistry and methylation-specific PCR (MSP), respectively. A loss of hMLH1 expression was recognized in 4(13.3 %) and loss of hMSH2 expression was recognized in 2(6.6 %) of 30 CRC cases whereas 50 % tumors showed reduced expression of hMLH1 and 33.3 % showed reduced expression of hMSH2 protein. One tumor showed a loss of both hMLH1 and hMSH2 expression. Normal nuclear staining pattern of hMLH1 and hMSH2 was observed in almost all the adjoining and normal mucosa. Promoter hypermethylation of the hMLH1 gene was detected in 15 of 30 CRC cases (50 %) and of hMSH2 gene was only in 3 of 30 CRC cases (10 %). No promoter methylation of hMLH1 and hMSH2 genes was observed in adjoining and normal mucosa. Combination of methylation of hMLH1 and hMSH2 gene was observed in two tumors (6.6 %). A significant correlation between histological grade of the tumor, methylation and expression of hMLH1 gene (p?<?0.05) was observed. Normal expression of hMLH1 and hMSH2 was seen in all of the unmethylated tumors (100 %). Nuclear staining and promoter methylation of hMLH1 and hMSH2 did not significantly influence survival. hMLH1 methylation was common and was significantly correlated with loss of hMLH1 protein expression. In contrast, hMSH2 methylation was infrequent. These findings suggest that the inactivation of MMR gene expression probably via hypermethylation may lead to inactivation of their functions which finally leads to tumor aggressiveness and the immunostaining of hMLH1 protein can be used as a prognostic factor for determining the grade of the tumor.     

A cancer-prone case with a background of methylation of p16 tumor suppressor gene.

PURPOSE AND EXPERIMENTAL DESIGN: To date, the presence of p16 gene promoter methylation associated with loss of protein expression has been demonstrated frequently in digestive tract cancers. In this study, we tested for the methylation status of p16 promoter in normal tissue specimens using the methylation-specific PCR technique to examine whether p16 methylation already existed in the background of tumors. RESULTS: Aberrant promoter methylation of p16 gene was detected in 1 of 40 esophageal and 1 of 69 gastric and no colorectal epithelium specimens, and these 2 specimens were derived from the same patient. We also found the same methylation change in both tumor and blood cell DNA. CONCLUSION: These results suggested that the p16 gene was inactivated by methylation in normal background cells of this patient and that other additional factors may promote tumor development in his esophageal and gastric tissues.     

P16 methylation of the colorectal cancer and association with dukes stages

Since its discovery as a CDKi (cyclin-dependent kinase inhibitor) in 1993, the tumor suppressor p16(INK4/MTS1/CDKN2A) has been found to play animportant role in carcinogenesis[1,2]. A high frequency of p16 gene alterations were observed in many tumors. P16 gene alterations have at least three ways: homozygousdeletion, point mutation and methylation of thepromoter[3]. The first two mechanisms have never been found in colorectal cancer[3-5]. The role of p16 gene methylation in tumorigenesi…     

肺鳞癌、腺癌中p14 ARF基因启动子区甲基化及蛋白表达的研究

背景与目的 p14^ARF基因是新近发现的抑癌基因，其异常表达与多种人类肿瘤发生有关，启动子区异常甲基化作为p14^ARF基因失活的重要形式可能参与了肿瘤的发生。本研究通过检测肺鳞癌、腺癌中p14^ARF启动子区甲基化状态和蛋白表达，探讨p14^ARF启动子区甲基化与肺癌的关系。方法 通过免疫组织化学（IHC）、甲基化特异性PCR（MSP）和相关限制性内切酶PCR（RF-PCR）方法，检测40例肺鳞癌、腺癌组织中p14^ARF启动子区甲基化状态和蛋白表达水平。结果 癌组织及癌旁正常组织中p14^ARF启动子区甲基化阳性率分别为17．5％（7／40）和2．5％（1／40）（P-0．025）。RE-PCR检测结果相同。癌组织及癌旁正常组织中p14^ARF蛋白阳性率分别为70．0％（28／40）和95．0％（38／40）（P-0．003）。p14^ARF基因启动子区甲基化和蛋白表达均与肿瘤分期、组织类型、分化程度、淋巴结转移等临床病理特征无明显关系（P＜0．05）。p14^ARF启动子区甲基化与蛋白表达呈负相关（r=-0．56，P=0．001）。结论 启动子区甲基化是p14^ARF基因失活的重要机制。p14^ARF启动子区异常甲基化可能参与了非小细胞肺癌的发生，是肺癌发生过程的早期事件。     

DNA启动子甲基化致ADAMTS9蛋白下调促进大肠癌病程进展

背景与目的：大肠癌的发病率逐年递增。该研究旨在考察ADAMTS9蛋白水平及其启动子甲基化水平在大肠癌发病及病程进展中的意义。方法：采用甲基化特异性PCR法,检测162例大肠癌患者外周血来源DNA样本中ADAMTS9基因启动子甲基化水平;并应用酶联免疫吸附试验法检测162例大肠癌患者和150例健康体检者血浆ADAMTS9蛋白水平。结果：与健康人相比,大肠癌患者血浆中ADAMTS9蛋白水平明显降低[(65.25±9.70)μg vs (50.28±9.66)μg,P<0.001];162例大肠癌患者中有66例ADAMTS9基因启动子存在甲基化(40.7%);甲基化患者的血浆ADAMTS9蛋白水平显著降低(P<0.001),而ADAMTS9蛋白低表达患者的血样ADAMTS9基因甲基化水平显著升高(P=0.007);ADAMTS9甲基化与肿瘤大小(P=0.017)和肿瘤分化程度(P=0.029)密切相关,而ADAMTS9蛋白低表达与浸润深度(P=0.020)、淋巴结转移(P=0.019)和Dukes分期(P=0.002)密切相关。结论：在大肠癌中,由DNA启动子甲基化引起的ADAMTS9蛋白表达下调可能参与大肠癌的发病、侵袭转移、并促进病程进展。     

食管鳞癌中p16基因启动子区甲基化及其表达

 目的探讨食管鳞癌（ESCC）p16基因甲基化的状况及其表达与食管鳞癌临床病理特征之间的关系。方法采用甲基化特异性PCR方法（MSP）分别检测75例食管癌组织、癌旁组织和切缘组织p16基因启动子区域CpG岛甲基化状态。采用Envision免疫组化法检测食管癌组织及癌旁组织的p16蛋白的表达。结果75例标本中，食管癌组织、癌旁组织和切缘细织p16基因甲基化率分别为41．3％（31／75）、13．3％（10／75）和6．67％（5／75）。癌组织和癌旁组织P16蛋白的阳性表达率分别为29．3％（22／75）和56．7％0（17／30）。31例癌组织p16基因甲基化阳性标本中有2例（6．4％）检测到P16蛋白的表达，而44例癌组织p16基因甲基化阴性标本中有20例（45．5％）检测到P16蛋白的表达。食管癌组织p16基因甲基化率显著高于癌旁组织和切缘组织（P〈0.01），P16蛋白表达与p16基因甲基化呈负相关。p16基因启动子区甲基化与食管癌的组织学分级、肿瘤部位无明显相关，与临床分期、淋巴转移密切相关。结论p16基因甲基化在食管癌发生发展中起着重要作用，食管鳞癌的分期和淋巴结转移与p16基因甲基化之间有密切关系。     

Hypermethylation of RARβ2 correlates with high COX-2 expression and poor prognosis in patients with colorectal carcinoma

Silencing of gene expression by aberrant methylation at the CpG islands is common in human tumors, including colorectal cancer. This epigenetic alteration affects promoter of genes having crucial cellular functions such as tumor suppressor, DNA repair, apoptosis, cell adhesion, etc. We investigated the methylation status in the promoter regions of the RARβ2, RASSF1A, DAPKinase, and CDH1 genes in 73 colorectal carcinoma and 43 paired normal tissues of Tunisian patients using methylation-specific PCR assays. The association between methylation status and the clinicopathological features was evaluated. To determine whether aberrant methylation affects gene expression, we performed immunohistochemistry analysis for E-cadherin and COX-2, a target gene of RARβ2. The methylation frequencies vary from 80.8% for RARβ2 to 35.6% for RASSF1A while in non-tumor-paired samples; the frequencies of methylation are significantly lower for all the fourth genes tested. The methylation status did not correlate with any of the clinical features considered; however, aberrant methylation of RARβ2 was associated with a shortened overall patients’ survival (p logrank?=?0.026); nevertheless, it needs to be confirmed on larger sample size. Moreover, a significant inverse association was observed between methylation status of RARβ2 and COX-2 protein expression in tumor specimen (p?=?0.014). On the other hand, we found that loss of E-cadherin expression was significantly associated with aberrant methylation of the CDH1 promoter (p?=?0.005). Our findings showed that RARβ2 was frequently methylated in colorectal cancer and correlated with a worse prognosis and high expression of COX-2 suggesting a link between these two proteins in colorectal carcinogenesis. We also showed that epigenetic alteration of CDH1 is a major mechanism of the loss of E-cadherin protein expression in primary colorectal tumors.     

Prognostic significance of CDKN2A (p16) promoter methylation and loss of expression in 902 colorectal cancers: Cohort study and literature review

A cyclin‐dependent kinase inhibitor CDKN2A (p16/Ink4a) is a tumor suppressor and upregulated in cellular senescence. CDKN2A promoter methylation and gene silencing are associated with the CpG island methylator phenotype (CIMP) in colon cancer. However, prognostic significance of CDKN2A methylation or loss of CDKN2A (p16) expression independent of CIMP status remains uncertain. Using a database of 902 colorectal cancers in 2 independent cohort studies (the Nurses' Health Study and the Health Professionals Follow‐up Study), we quantified CDKN2A promoter methylation and detected hypermethylation in 269 tumors (30%). By immunohistochemistry, we detected loss of CDKN2A (p16) expression in 25% (200/804) of tumors. We analyzed for LINE‐1 hypomethylation and hypermethylation at 7 CIMP‐specific CpG islands (CACNA1G, CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1); microsatellite instability (MSI); KRAS, BRAF and PIK3CA mutations; and expression of TP53 (p53), CTNNB1 (β‐catenin), CDKN1A (p21), CDKN1B (p27), CCND1 (cyclin D1), FASN (fatty acid synthase) and PTGS2 (cyclooxygenase‐2). CDKN2A promoter methylation and loss of CDKN2A (p16) were associated with shorter overall survival in univariate Cox regression analysis [hazard ratio (HR): 1.36, 95% CI: 1.10–1.66, p = 0.0036 for CDKN2A methylation; HR: 1.30, 95% CI: 1.03–1.63, p = 0.026 for CDKN2A (p16) loss] but not in multivariate analysis that adjusted for clinical and tumor variables, including CIMP, MSI and LINE‐1 methylation. Neither CDKN2A promoter methylation nor loss of CDKN2A (p16) was associated with colorectal cancer‐specific mortality in uni‐ or multivariate analysis. Despite its well‐established role in carcinogenesis, CDKN2A (p16) promoter methylation or loss of expression in colorectal cancer is not independently associated with patient prognosis.     

Methylation pattern of the O6-methylguanine-DNA methyltransferase gene in colon during progressive colorectal tumorigenesis

O(6)-methylguanine-DNA methyltransferase (MGMT) is a DNA repair gene which is frequently methylated in colorectal cancer (CRC). However, it remains controversial whether methylation of specific CpG sequences within MGMT promoter leads to loss of its protein expression, and if MGMT methylation correlates with G to A transition mutations in KRAS. Two methylation sensitive regions (Mp and Eh region) of MGMT promoter were investigated in 593 specimens of colorectal tissue: 233 CRCs, 104 adenomatous polyps (AP), 220 normal colonic mucosa from CRC patients (N-C) and 36 normal colonic mucosa specimens obtained from subjects without colorectal neoplasia (N-N) by combined bisulfite restriction analysis (COBRA). The region-specific methylation data were compared to the MGMT protein expression, spectrum of KRAS mutations and other clinical features. Extensive (including both Mp and Eh) and partial (either Mp or Eh) MGMT methylation were found in 24.5% and 11.6% of CRCs, 3.8% and 27.9% of APs, 0.5% and 7.7% of C-Ns and 2.8% and 2.8% of N-Ns, respectively. Extensive methylation of MGMT promoter was primarily present in CRCs while partial methylation was common in APs. Extensive methylation of MGMT promoter was associated with loss/reduced protein expression (p < 0.0001), as well as with G to A mutations in KRAS (p = 0.0017). We herein provide first evidence that extensive methylation of MGMT promoter region is essential for methylation-induced silencing of this gene. Our data suggest that MGMT methylation may evolve and spread throughout the promoter in a stepwise manner as the colonic epithelial cells progress through the classical-adenoma-cancer multistep cascade.     

SLIT2 axon guidance molecule is frequently inactivated in colorectal cancer and suppresses growth of colorectal carcinoma cells

We have shown recently that SLIT2 has tumor suppressor activity and that it is epigenetically silenced in >40% of lung and breast tumors. In this study, we have analyzed the methylation status of SLIT2 in primary colorectal cancers and matching normal colorectal mucosa. SLIT2 promoter region methylation was found in 23 (72%) of 32 primary colorectal cancers. In contrast, normal colorectal mucosa from the same patients exhibited significantly lower levels of SLIT2 promoter region hypermethylation. SLIT2 methylation was reversed and expression restored by treating colorectal tumor cell lines with the demethylating agent 5-aza-2-deoxycytidine. Loss of heterozygosity at D4S1546 marker, which maps within 100 kb of the SLIT2 gene, was observed in 39% of the methylated tumors. Furthermore, SLIT2 epigenetic silencing was independent of ROBO1/p16/RASSF1A hypermethylation. The presence of SLIT2 methylation was also independent of the presence of K-RAS mutations. Ectopic expression of SLIT2 diminished the ability to form colonies in two colorectal tumor cell lines. In addition, conditioned medium from SLIT2-transfected COS-7 cells reduced cell growth and induced apoptosis in SW48 colorectal tumor cell line. In conclusion, SLIT2 is an excellent candidate tumor suppressor gene for colorectal cancer.     

胶质瘤患者外周血 DNA 修复基因甲基化与蛋白表达的相关性

目的：探讨胶质瘤患者O6-甲基鸟嘌呤-DNA-甲基转移酶（ O6-Methylguanine -DNA methyltransferase,MGMT）及人类错配修复基因 MSH2（Human mutS homolog2,hMSH2）蛋白表达与外周血相应基因启动子甲基化的相关性。方法分别采用免疫组化法及甲基化特异性PCR （ MSP ）检测275例胶质瘤患者肿瘤组织MGMT、hMSH2蛋白的表达及外周血中这两个基因启动子甲基化情况。结果脑胶质瘤患者肿瘤组织MGMT和hMSH2蛋白阴性表达率分别为47．2％和62．5％;基因启动子区甲基化阳性率分别为41．8％和22．4％。统计学分析显示外周血MGMT基因启动子甲基化与肿瘤组织蛋白阴性表达相关（P＜0．05）。 hMSH2基因启动子甲基化与肿瘤组织hMSH2蛋白表达不具有相关性（P＞0．05）。结论 MGMT基因甲基化是脑胶质瘤发生过程中常见的分子事件,可能与胶质瘤的发生有关;而hMSH2基因启动子甲基化可能并不是胶质瘤hMSH2蛋白失活的主要原因,可能存在其他重要因素影响其表达。     

Methylation of hMLH1 in a population-based series of endometrial carcinomas.

Microsatellite instability (MSI) is a characteristic feature of hereditary nonpolyposis colorectal cancer and is also observed in sporadic colorectal and endometrial cancers. Alterations in the mismatch repair genes hMLH1 and hMSH2 are important for the development of MSI. It has recently been demonstrated that hypermethylation of the hMLH1 promoter region is associated with MSI and appears to be a common mechanism for gene inactivation. For endometrial carcinoma, however, previous studies have been relatively small and have not been population based. We therefore wanted to assess the frequency and prognostic significance of hypermethylation of the hMLH1 and hMSH2 genes in conjunction with hMLH1 protein expression in a prospective and population-based series of endometrial carcinoma patients with known MSI status and complete follow-up. A total of 138 patients were studied, and methylation of hMLH1 was found in 23% of tumors with conclusive results, whereas methylation of hMSH2 was seen in only 1% of tumors. Methylation of hMLH1 was significantly correlated with MSI (P < 0.001). Loss of nuclear staining of hMLH1 protein was seen in 14% of the cases and was significantly correlated with hMLH1 methylation and MSI (P < 0.001). Normal expression of hMLH1 was seen in all of the unmethylated tumors (100%). Of the 14 MSI-positive tumors that were also methylated, all but 1 (93%) showed a loss of nuclear expression of hMLH1. None of the tumors with loss of hMLH1 expression or hMLH1 methylation were aneuploid (P for both < or = 0.05), and loss of hMLH1 expression and hMLH1 methylation was significantly correlated with lack of p53 overexpression (P for both < or = 0.05). Nuclear hMLH1 staining and hMLH1 methylation did not significantly influence survival. In conclusion, hMLH1 methylation was common and was significantly correlated with loss of hMLH1 protein expression, MSI, diploid tumors, and lack of p53 overexpression. In contrast, hMSH2 methylation was infrequent in this prospective and population-based series of endometrial carcinomas.     

Methylation and regulation of expression of different retinoic acid receptor beta isoforms in human colon cancer

Tumor suppressor genes can become inactivated in cancer via hypermethylation of their promoter. The retinoic acid receptor beta (RARbeta) gene is expressed from two distinct promoters, both of which have CpG islands. RARbeta1 is expressed primarily during embryogenesis, whereas RARbeta2 is expressed in adult tissues and hypermethylated in a number of cancer cells. We used combined bisulfite restriction analysis to evaluate their methylation in colorectal mucosa and tumors. Methylation of RARbeta1 was detected, with a mean of 2% in normal colon tissues in young subjects (< 32 years), and 16% in older subjects (> 75 years) (P < 0.001). Using paired normal/tumor tissue samples, we found higher mean methylation rate in tumors than in adjacent normal tissue (mean, 46% versus 16%; P < 0.001) and hypermethylation of RARbeta1 in all eight cell lines examined. By RT-PCR, RARbeta1 was not expressed in normal adult colon tissues and its expression could not be efficiently activated in most cell lines by the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-Aza-CdR). RARbeta2 methylation was also observed in normal colon tissues and was lower in young individuals than in older ones (mean, 11% versus 23%; P < 0.05). Among paired samples, RARbeta2 methylation was higher in tumor tissue than in normal tissue in 14 cases, vice versa in 7 cases, and equal in 6 cases. All eight cell lines were hypermethylated and did not express RARbeta2, but RARbeta2 expression could be reactivated easily by 5-Aza-CdR. We suggest that the embryonic RARbeta1 isoform is readily hypermethylated in aging colon mucosa and all colorectal cancers because of its lack of expression in normal tissues. The adult RARbeta2 isoform also shows age-related methylation in normal tissues but more variable methylation in colorectal cancer, perhaps because its expression offers continued protection against methylation or its silencing does not provide a selective advantage in the early stages of the disease.     

Loss of function of p16 gene and prognosis of pulmonary adenocarcinoma

BACKGROUND: Stepwise progression of peripheral-type lung adenocarcinoma was characterized morphologically and was related to prognosis. Expression of the tumor suppressor gene p16 in pulmonary adenocarcinoma decreased, mainly as a result of aberrant methylation of the CpG islands of the promoter region. METHODS: Aberrant methylation status of the p16 promoter region, the expression of its product, and loss of heterozygosity (LOH) on 9p21 were examined in surgically resected lung specimens from 57 patients (28 males and 29 females) with peripheral-type lung adenocarcinoma measuring 相似文献   

NSCLC患者血清中p16、DAP基因甲基化的研究

目的：探讨p16、死亡相关蛋白激酶（death-associated protein kinase,DAP）基因的异常甲基化作为非小细胞肺癌（NSCLC）患者诊断的基因标志物的可行性。方法：采用甲基化特异性PCR（MSP）法检测30例NSCLC患者肿瘤组织及对应血清中p16、DAP基因的异常甲基化，结果：NCSLC肿瘤中60．0％（18／30）检测出至少一个基因启动子呈甲基化改变，在18例肿瘤组织检测到异常甲基化的患者中，50．0％的患者（9／18）在血清中检测到相应的改变。所有的癌旁组织、健康对照组的血清中及正常肺组织均未检测到p16、DAP的甲基化，结论：检测NSCLC患者血清中p16、DAP基因异常甲基化有可能成为肺癌诊断的分了标志物。     

抑癌基因促甲状腺激素受体和p16启动子甲基化与甲状腺乳头状癌关系的研究

 目的　研究促甲状腺激素受体（TSHR）和p16抑癌基因在甲状腺乳头状癌的表达及启动子甲基化的情况, 分析两种抑癌基因的甲基化状况与肿瘤发生的关系。方法　对50例甲状腺乳头状癌组织和32例对照组织（20例结节性甲状腺肿,12例甲状腺腺瘤）提取RNA后,反转录为cDNA,进行PCR,检测两种抑癌基因mRNA的表达情况,运用甲基化PCR（其中p16使用巢氏甲基化PCR）检测上述组织中两种抑癌基因启动子区甲基化的情况, 对两种抑癌基因甲基化和未甲基化的组织随机进行测序。结果　甲状腺乳头状癌组50例患者中,有34例（68 %）TSHR基因、27例（54 %）的p16 基因启动子发生了甲基化;对照组32例患者中,有7例（21.9 %）TSHR基因、5例（15.6 %）的p16基因启动子发生了甲基化;甲状腺乳头状癌组TSHR基因、p16基因启动子甲基化率均显著高于对照组,差异有统计学意义（χ2=16.61,P < 0.05;χ2＝12.08,P <0.05）。TSHR基因和p16基因mRNA在甲状腺乳头状癌中的表达量分别为0.41±0.11、0.51±0.17,相应的对照组织的mRNA的表达量分别为0.63±0.08、0.72±0.22,两种基因的mRNA在甲状腺乳头状癌中的表达明显低于对照组织,差异有统计学意义（t值分别为3.86和3.66,P <0.05）。最终,经DNA 测序证实,两种抑癌基因启动子发生甲基化的其CpG岛的碱基未发生改变,仍为CG;未发生甲基化的,碱基由CG变为TG。结论　两种抑癌基因启动子甲基化与甲状腺乳头状癌的发生和发展均相关。     

结直肠肿瘤中sFRP基因的甲基化及表达调控

目的探讨分泌型卷曲相关蛋白(sFRP)家族基因启动子CpG岛甲基化在结直肠肿瘤发生、发展中的作用。方法应用5-氮杂-2’-脱氧胞苷(DAC)和曲古菌素A(TSA)对结直肠癌细胞系RKO、HCT116和SW480进行去甲基化处理。甲基特异性PCR和逆转录PCR分别检测结直肠肿瘤组织及细胞系中sFRP基因甲基化和mRNA表达。结果正常大肠黏膜不存在sFRP基因甲基化。sFRP1、sFRP2和sFRP5在结直肠腺癌、腺瘤和异常隐窝灶(ACF)中均存在高频率甲基化,sFRP1甲基化率>85%,sFRP2甲基化率>75%,sFRP5甲基化率>50%,腺癌、腺瘤和ACF间sFRP基因甲基化率差异无统计学意义(P>0.05),但均高于正常黏膜及瘤旁正常组织(P<0.05)。3种结直肠癌细胞系RKO、HCT116和SW480均存在sFRP基因甲基化,甲基化的sFRP基因mRNA失表达。联合使用DAC和TSA能有效恢复结直肠癌细胞系的sFRP基因表达。结论在ACF中,sFRP基因家族已出现高频率甲基化,是结直肠肿瘤发生常见的早期事件,sFRP1、sFRP2和sFRP5甲基化可能成为早期发现结直肠肿瘤的生物学标志。去甲基化能有效恢复基因表达,可能成为治疗肿瘤的有效手段。