SFRP1基因表达与大肠肿瘤发生的关系研究

目的：探讨SFRP1与大肠癌发生的关系。方法：运用半定量RT—PCR方法及免疫组化方法检测SFRP1、β—catenin、E—cad在正常大肠粘膜、大肠腺瘤以度大肠腺癌中的表达。结果：大肠腺癌、腺瘤组织的β—catenin、E—cad胞膜表达不同程度缺失，β—catenin呈胞质和胞核异位表达，腺瘤β—eatenin的异位表达率为87．5％．低于大肠腺癌（100％，P〈0．05）。大肠腺瘤β—eatenin、E—cad胞膜表达缺失率分别为37。5％、37．5％，低于大肠腺癌（58．8％、76.4％，P均〈0．05）。半定量RT—PCR显示，SFRP1基因在大肠腺瘤、大肠腺癌组织中的表达水平均明显低于大肠正常组织的对照组，且大肠腺癌组织中SFRP1基因的表达水平低于大肠腺瘤（P〈0．05）。结论：SFRP1基因下调使其抬抗Wnt途径的功能削弱，导致Wnt的持续存在，其下游基因β—eatenin、E—cad异常表达，从而导致大肠粘膜细胞获得恶变潜能。故SFRP1可能为预防大肠肿瘤的发生、大肠肿瘤的早期诊断提供新思路，并为防治大肠肿瘤提供新靶标和实验依据。     

APC、β-catenin、C-myc和Cyclin D1在大肠癌组织中的表达及其意义

背景与目的:Wnt信号转导通路成员各癌基因、抑癌基因的异常,激活下游相关靶基因的转录,在肿瘤发生发展中起重要作用.本研究通过检测不同大肠组织中APC、β-catenin、C-myc和Cyclin D1的表达情况,探讨其在大肠癌发生中的意义.方法:应用免疫组织化学方法检测30例正常大肠粘膜、30例大肠腺瘤、10例大肠腺瘤恶变及50例大肠癌组织中APC、β-catenin、C-myc和Cyclin D1蛋白的表达情况.以β-catenin在细胞膜表达为正常表达,而在胞浆和/或胞核表达为异位表达.结果:大肠癌和大肠腺瘤恶变组织APC阳性率分别为44.0%和40.0%,显著低于大肠腺瘤(86.7%)和正常大肠粘膜(100%)(P＜0.01).大肠癌、大肠腺瘤恶变组织和大肠腺瘤β-catenin胞浆和/或胞核异位表达率分别为62.0%、50.0%、30.0%,均显著高于正常大肠粘膜(0%)(P＜0.01),大肠癌β-catenin异位表达率显著高于大肠腺瘤(P＜0.01).大肠癌、大肠腺瘤恶变组织、大肠腺瘤中C-myc表达率分别为56.0%、60.0%、46.7%,均显著高于正常大肠粘膜(0%)(P＜0.01),而Cyclin D1阳性率分别为66.0%、60.0%、30.0%,均显著高于正常大肠粘膜(0%)(P＜0.01).大肠癌Cyclin D1表达率显著高于大肠腺瘤(P＜0.01).大肠癌中β-catenin异位表达与C-myc和Cyclin D1表达呈正相关关系(r=0.63,P＜0.01;r=0.57,P＜0.01),而与APC表达呈负相关关系(r=-0.39,P＜0.05).结论:大肠癌组织中存在APC低表达和/或β-catenin异位表达,以及C-myc和Cyclin D1的过度表达,4种基因蛋白可能在大肠癌发生过程中起重要作用.     

APC、β-catenin及c-myc在大肠腺瘤-癌组织序列中的表达及其意义

目的 探讨大肠腺瘤性息肉病基因(adenomatous polysis coil,APC)、β-环形蛋白(β-catenin)及原癌基因蛋白c-myc的表达在大肠肿瘤发生发展中的作用及其与临床病理参数之间的关系.方法 应用免疫组织化学SP法检测APC、β-catenin及c-myc在大肠正常黏膜、大肠腺瘤和大肠腺癌组织中的表达.结果 ①正常黏膜、大肠腺瘤和大肠腺癌中APC蛋白的表达率为97.3%、25.0%、24.6%.腺瘤与腺癌组均低于正常黏膜组(P＜0.01),腺瘤与腺癌组差异不显著(P＞0.05).②β-catenin在正常黏膜组为胞膜表达,腺瘤与腺癌组呈胞质/核异位表达,异位表达率为10.8%、75.0%、98.2%,3组之间有显著性差异(P＜0.01).③正常黏膜、大肠腺瘤和大肠腺癌中c-myc的表达率为10.8%、40.6%、70.2%.3组之间有显著性差异(P＜0.01).④大肠腺癌中β-catenin蛋白的异常表达随着肿瘤大小、组织学分级、Dukes分期的改变呈逐渐增高趋势,有淋巴结转移者β-catenin蛋白阳性表达率(100.0%)高于无淋巴结转移者(96.4%),但无显著性差异(P＞0.05).结论 APC的失表达、β-catenin的异常表达及c-myc的过表达与大肠肿瘤的发生发展有关,β-catenin的异常表达可能与大肠腺癌的恶性行为有关.     

β-catenin在大肠肿瘤中的表达及其意义

目的:探讨β-连环素(β-catenin)的表达在大肠肿瘤发生发展中的作用及其与临床病理参数之间的关系。方法:应用免疫组织化学SP法检测β-catenin在大肠正常黏膜、大肠腺瘤和大肠腺癌中的表达。结果:β-catenin在正常黏膜中为胞膜表达,腺瘤与腺癌组呈胞浆/核异位表达,异位表达率为10.8%、75.0%、98.2%,三组之间有显著差异(P<0.01)。大肠腺癌中β-catenin蛋白的异常表达随着肿瘤大小、组织学分级、Dukes分期的改变呈逐渐增高趋势,有淋巴结转移者β-catenin蛋白阳性表达率(100.0%)高于无淋巴结转移者(96.4%),但无统计学意义(P>0.05)。结论:β-catenin的异常表达与大肠肿瘤的发生发展有关,是早期事件;β-catenin的异常表达可能与大肠腺癌的恶性行为有关。     

大肠癌中SFRP2和β-catenin的表达及意义

目的 探讨分泌型Frizzled相关蛋白2(Secreled Frizzled-relaled proleins2,SFRP2)和β-连接素(β-calenin)在大肠癌发生、发展中的作用.方法 采用免疫组化方法检测20例正常大肠黏膜20例非腺瘤性息肉、36例大肠腺瘤和42例大肠癌组织中的SFRP2和β-calenin蛋白的表达情况分析二者表达的差异及其与临床病理参数的关系.结果 大肠癌和大肠腺瘤组SFRP2的阳性表达率分别为28.6%和36.1%显著低于正常大肠黏膜(100.O%)和非腺瘤性息肉组(95.0%)(P<0.05).大肠癌中β-calenin膜表达缺失率为52.4%,显著高于正常大肠黏膜(O%)、非腺瘤性息肉(0%)及大肠腺瘤组(11.1%)(P<0.05).大肠癌和大肠腺瘤组β-calenin异位表达率分别为64.3%和30.6%显著高于正常大肠黏膜(0%)和非腺瘤性息肉组(0%)(P<0.05),大肠癌β-calenin异位表达率高于大肠腺瘤(P<0.05).SFRP2表达、β-calenin膜表达缺失及异位表达与大肠癌患者的肿瘤部位、大体形态、肿瘤直径、淋巴转移和Dukes分期无明显关系,而与大肠癌的分化程度密切相关,其中SFRP2表达还与大肠癌的浸润深度密切相关SFRP2表达与β-calenib膜表达缺失、异位表达呈显著负相关(P<0.01)而β-calenin膜表达缺失与异位表达呈显著正相关(P<0.01).结论 SFRP2和β-calenin的表达与大肠癌的发生、发展密切相关可能是大肠癌发生的早期事件,且SFRP2表达与β-calenin膜表达缺失、异位表达均呈负相关,前者起抑癌作用,后者起促癌作用.     

大肠癌中APC、β-catenin和cyclinD1的表达及其临床意义

目的：探讨APC、β-catenin和cyclinD1在大肠癌发生、发展过程中的作用。方法：应用免疫组织化学方法检测30例正常大肠黏膜、30例大肠腺瘤、10例大肠腺瘤恶变及50例大肠癌组织中APC、β-catenin和cyclinD1蛋白的表达情况。结果：大肠癌和大肠腺瘤恶变APC阳性率分别为44.0%,40.0%,显著低于大肠腺瘤（86.7%）和正常大肠黏膜（100%）（P〈0.01）。大肠癌、大肠腺瘤恶变和大肠腺瘤β-catenin胞浆和/或胞核异位表达率分别为：62.0%,50.0%,30.0%,显著高于正常大肠黏膜（0）（P〈0.01）,大肠癌β-catenin异位表达率显著高于大肠腺瘤（P〈0.01）。大肠癌中β-catenin膜表达缺失率为：46.0%,显著高于大肠腺瘤（10.0%）和正常大肠黏膜（0）（P〈0.01）。大肠癌、大肠腺瘤恶变、大肠腺瘤cyclinD1阳性率分别为：66.0%,60.0%,30.0%,显著高于正常大肠黏膜（0）（P〈0.01）,大肠癌cyclinD1阳性率显著高于大肠腺瘤（P〈0.01）。β-catenin膜表达缺失和cyclinD1高表达与大肠癌组织分化程度、浸润深度、淋巴结转移、Dukes分期有关。APC蛋白表达与大肠癌组织分化程度有关。大肠癌中β-catenin异位表达与cyclinD1阳性表达呈正相关关系（r=0.57,P〈0.01）,而与APC阳性表达呈负相关关系（r=-0.39,P〈0.05）。结论：APC失表达和/或β-catenin异位表达,可能是原癌基因cyclinD1激活的重要原因,并在大肠癌发生过程中起重要作用,可能是大肠癌发生的早期事件。β-catenin膜表达缺失和cyclinD1高表达与大肠癌的侵袭、转移有关。     

E-cadherin 、β-catenin 、FAK在大肠癌的表达及其意义

目的探讨β-连环素(β-cat)、上皮钙黏附素(E-cad)和黏着斑激酶(FAK)在大肠癌发生、发展中的作用.方法采用免疫组织化学方法检测了12例正常大肠黏膜,28例大肠腺瘤及49例大肠癌组织的β-cat、E-cad和FAK表达情况.结果大肠癌β-cat异位表达率61.2%,显著高于大肠腺瘤(35.7%,P＜0.05).大肠癌β-cat、E-cad膜表达缺失率分别为67.3%,57.1%,显著高于正常大肠黏膜和大肠腺瘤(P＜0.01,P＜0.01).大肠癌FAK阳性率65.3%,高于大肠腺瘤和正常大肠黏膜(P＜0.01).β-cat异位表达、β-cat和E-cad膜表达缺失、FAK表达与大肠癌的浸润程度、淋巴结转移和Dukes分期等因素有关.大肠癌中,FAK表达与β-cat、β-cad膜表达缺失及β-cat异位表达呈正相关.结论β-cat异位表达可能参与了大肠癌的发生、发展.β-cat和E-cad膜表达缺失、β-cat异位表达、FAK表达可能与大肠癌的侵袭和转移有关,此过程中,FAK可能抑制了癌细胞之间的黏附.     

食管鳞癌及贲门腺癌中分泌型卷曲相关蛋白4基因启动子区甲基化状态的联合检测

目的:检测食管鳞癌(esophageal squamous cell cancer,ESCC)和贲门腺癌(gastric cardia adenocarcinoma,GCA)中分泌型卷曲相关蛋白4(secreted frizzled related protein 4, SFRP4)的基因甲基化状态,探讨其与食管鳞癌和贲门腺癌发生的关系.方法:应用甲基化特异性PCR(methylation-specific PCR,MSP)及RT-PCR的方法检测49例食管鳞癌及58例贲门腺癌中SFRP4基因的甲基化状态及其mRNA表达情况,应用免疫组织化学法检测Wnt通路中心因子β-catenin蛋白的表达情况,并分析其与临床病理参数间的关系.结果: 在食管鳞癌及贲门腺癌中,SFRP4基因的甲基化率分别为42.6%(21/49)和72.4%(42/58),均明显高于癌旁非肿瘤组织(P<0.01).在贲门腺癌中SFRP4基因的高甲基化与肿瘤患者的临床分期相关,与病理分级无关;而在食管鳞癌中,该基因的甲基化与各临床病理指标均无关(P>0.05).SFRP4基因在食管鳞癌及贲门腺癌中mRNA阳性表达率分别为69.3%(34/49)和44.8%(26/58),均明显低于癌旁非肿瘤组织(P<0.05),且肿瘤组织中mRNA表达与该基因的甲基化状态明显相关(P<0.01).通路中心因子β-catenin蛋白在食管鳞癌及贲门腺癌中的异质表达率分别为65.3%(32/49)和86.2%(50/58),均明显高于癌旁非肿瘤组织(P<0.01),且其异质表达与SFRP4基因的甲基化状态相关(P<0.05).结论:SFRP4基因的高甲基化状态可能是引起贲门癌及食管癌发生的共同分子机制之一,并有可能通过Wnt/β-catenin信号转导通路发挥作用. 检测SFRP4基因甲基化状态对于贲门腺癌的预后评估有一定参考价值.     

大肠癌β-连环素和上皮钙黏附素表达及其意义

目的 :探讨 β 连环素 (β catenin ,β cat)和上皮钙黏附素 (E cadherin ,E cd)在大肠癌发生、发展中的作用。方法 :采用免疫组化方法检测 2 5例正常人大肠黏膜、4 2例大肠腺瘤、19例腺瘤癌变及 5 8例大肠癌组织的 β cat、E cd的表达情况。结果 :正常大肠黏膜 β cat、E cd呈胞膜阳性表达。大肠腺瘤、腺瘤癌变和大肠癌组织 β cat表达特征发生改变 ,胞膜表达缺失 ,呈胞浆和 或胞核异位表达 ,腺瘤癌变 β cat异位表达率为 89 5 % ,显著高于大肠腺瘤 (4 2 9% ,P <0 0 1)和大肠癌 (65 5 % ,P <0 0 5 ) ;β cat异位表达与大肠癌的组织分化程度、淋巴结转移、Dukes分期等因素有关。大肠癌 β cat、E cd胞膜表达缺失率分别为 77 6%、70 7% ,显著高于大肠腺瘤 (33 3%、2 8 6% )和腺瘤癌变 (4 2 1%、36 8% ) (P <0 0 1) ,且与大肠癌淋巴结转移和Dukes分期有关。结论 :β cat异位表达可能参与了大肠癌发生、发展过程 ;β cat、E cd胞膜表达缺失可能与大肠癌的侵袭和转移有关     

散发性结直肠腺癌APC、β-catenin基因的表达及其意义

目的探讨APC、β-catenin在散发性结直肠肿瘤发生、发展中的作用和意义。方法采用SP免疫组化方法检测55例散发性结直肠腺癌、33例结直肠腺瘤组织标本中APC、β-catenin基因蛋白产物的表达水平。结果APC基因蛋白产物在结直肠腺癌组织中阳性表达率(23.6%)明显低于正常结直肠黏膜组织(86.7%)和结直肠腺瘤组织(72.7%),差异有显著性(P<0.05)。结直肠腺瘤、结直肠腺癌组织中β-catenin阳性表达率(69.7%、81.8%)明显高于正常结直肠黏膜组织(0%),差异有显著性P<0.05。结直肠腺癌中APC的表达与β-catenin的表达呈负相关关系γ=-0.514,P<0.05。结论APC、β-catenin基因在散发性结直肠腺癌的发生、发展过程中有重要作用。散发性结直肠腺癌组织中β-catenin细胞核聚集的主要原因可能是APC蛋白产物功能的失活。β-catenin细胞核异位表达是散发性结直肠腺癌发生发展过程中的早期改变。     

Ⅱ型子宫内膜癌中E-cadherin、β-catenin和HER2的表达及意义

目的:探讨Ⅱ型子宫内膜癌中上皮钙黏素(E-cadherin,E-cad)、β-连环素(β-catenin,β-cat)和HER2表达的关系及临床病理意义. 方法:采用Envision法检测84例Ⅱ型子宫内膜癌中E-cad、β-cat和HER2的表达,分析三者表达与临床病理的关系,并对随访数据资料进行统计学处理.结果:84例Ⅱ型子宫内膜癌中E-cad、β-cat和HER2的阳性表达率分别为52.4%、67.9%和76.2%.Ⅱ型子宫内膜癌中E-cad、β-cat和HER2的表达均与肿瘤TNM分期及淋巴结转移有关(P<0.05),与患者年龄、肿瘤大小及组织学分级无关(P>0.05).Ⅱ型子宫内膜癌中E-cad表达与β-cat和HER2表达呈负相关(P<0.05),β-cat和HER2表达与临床分期和患者生存率呈负相关(P<0.05).结论:E-cad可抑制Ⅱ型子宫内膜癌的浸润和转移,与β-cat和HER2表达具有相关性,可能在Ⅱ型子宫内膜癌的发展过程中具有协调作用,联合检测E-cad、β-cat和HER2可能为临床判断子宫内膜癌的预后和个体化治疗提供参考指标.     

Centrosomal Kinases, HsAIRK1 and HsAIRK3, are Overexpressed in Primary Colorectal Cancers

Members of the recently identified family of Homo sapiens Aurora/Ipl1-related kinases (HsAIRKs), homologous to chromosome segregation kinases, fly Aurora and yeast Ipl1 , are highly expressed during M phase, and have been suggested to regulate centrosome function, chromosome segregation, and cytokinesis. In the present study, immunohistochemical analyses were performed of HsAIRK1 and HsAIRK3 expression in 78 primary colorectal cancers and 36 colorectal adenomas as well as 15 normal colorectal specimens. In normal colon mucosa, some crypt cells showed weak positive staining in 10 and 12 out of 15 cases for HsAIRK1 and HsAIRK3, respectively, the remaining cases being negative. Elevated expression of HsAIRK1 was observed in 53 (67.9%) of the colorectal cancers, and of HsAIRK3 in 40 (51.3%). Furthermore, colorectal adenomas showed high expression of HsAIRK1 and HsAIRK3 in 11 (30.6%) and 7 (19.4%) cases, respectively, thus being intermediate between colorectal cancers and normal colorectal mucosa. Interestingly, HsAIRK1 overexpression was significantly associated with pT (primary tumor invasion) and p53 accumulation in colorectal cancers. There was no significant correlation between proliferating cell nuclear antigen-labeling index (PCNA-LI) and the levels of these proteins. The results suggest that overexpression of HsAIRK1 and HsAIRK3 might be involved in tumorigenesis and/or progression of colorectal cancers.     

Centrosomal kinases, HsAIRK1 and HsAIRK3, are overexpressed in primary colorectal cancers.

Members of the recently identified family of Homo sapiens Aurora / Ipl1-related kinases (HsAIRKs), homologous to chromosome segregation kinases, fly Aurora and yeast Ipl1, are highly expressed during M phase, and have been suggested to regulate centrosome function, chromosome segregation, and cytokinesis. In the present study, immunohistochemical analyses were performed of HsAIRK1 and HsAIRK3 expression in 78 primary colorectal cancers and 36 colorectal adenomas as well as 15 normal colorectal specimens. In normal colon mucosa, some crypt cells showed weak positive staining in 10 and 12 out of 15 cases for HsAIRK1 and HsAIRK3, respectively, the remaining cases being negative. Elevated expression of HsAIRK1 was observed in 53 (67.9%) of the colorectal cancers, and of HsAIRK3 in 40 (51.3%). Furthermore, colorectal adenomas showed high expression of HsAIRK1 and HsAIRK3 in 11 (30.6%) and 7 (19.4%) cases, respectively, thus being intermediate between colorectal cancers and normal colorectal mucosa. Interestingly, HsAIRK1 overexpression was significantly associated with pT (primary tumor invasion) and p53 accumulation in colorectal cancers. There was no significant correlation between proliferating cell nuclear antigen-labeling index (PCNA-LI) and the levels of these proteins. The results suggest that overexpression of HsAIRK1 and HsAIRK3 might be involved in tumorigenesis and / or progression of colorectal cancers.     

Genetic Alterations and Expression Pattern of CEACAM1 in Colorectal Adenomas and Cancers

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is expressed on epithelial cells throughout the intestinal tract and is a negative regulator of tumor cell growth, suggesting that it may function as a tumor suppressor. In this study, to determine whether the CEACAM1 is involved in colorectal tumorigenesis, we have investigated the genetic alterations, including mutations and allelic loss, of the CEACAM1 gene in 17 colonic adenomas and 123 sporadic colorectal cancers. In addition, the expression pattern of the CEACAM1 protein was examined in 60 colonic adenomas and 123 sporadic colorectal adenocarcinomas. No mutation was found in colonic adenomas, but four somatic missense mutations, L36F, T312I, V398I and A445V, were detected in colorectal cancers. Interestingly, all of the mutations were found in left-side colon cancers of the patients with clinical stage III. In LOH analysis, nine adenomas were informative for at least one of the markers and five (55.6%) showed allelic loss. Thirty-eight cancers were informative at D19S211 and D19S872 markers and 21 (56.3%) showed LOH at these markers. Statistically, the frequency of allelic loss at the CEACAM1 locus was not associated with clinicopathologic parameters (P > 0.05). In immunohistochemical analysis, loss of expression of CEACAM1 protein was detected in nine (15.0%) and 30 (24.4%) of 60 colorectal adenomas and 123 colorectal cancers. Statistically, there was no significant relationship between loss of CEACAM1 expression and clinicopathologic parameters, including clinical stage, tumor location, tumor size, lymph node metastasis and 5-year survival (P > 0.05). These data suggest that genetic alteration and loss of expression of the CEACAM1 may contribute to the development of colorectal cancers, as an early event.     

CD44V6在结直肠癌组织中的表达及临床意义

目的：探讨CD44V6表达与结直肠癌发生、发展及转移的关系。方法：采用S－P免疫组织化学方法，检测78例原发性结直肠腺癌、14例结直肠腺瘤癌变、57例结直肠腺瘤、30例结直肠增生性息肉和24例结直肠正常黏膜中CD44V6的表达情况。结果：腺瘤、腺瘤癌变和腺癌组织中CD44V6阳性表达率分别为78．95％、100．00％和56．41％，明显高于增生性息肉和正常黏膜组织的阳性表达率（14．81％）。CD44V6阳性表达与腺癌淋巴结转移、Dukes分期和病理分级无相关性。结论：CD44V6表达与结直肠癌的发生有关，可作为诊断结直肠癌前病变和早期癌的生物学指标。     

EphB2 is a prognostic factor in colorectal cancer.

A receptor tyrosine kinase for ephrin ligands, EphB2 is expressed in colorectal cancer and has been proposed as a target for immunoconjugate therapy. The aim of this study was to perform a detailed histologic analysis of EphB2 expression in normal and neoplastic colorectal tissues. In addition, we sought to evaluate EphB2 expression as a prognostic factor in colorectal cancer. Expression of EphB2 was examined in normal colon (n = 28), colorectal cell lines (n = 20), colorectal adenomas (n = 148), primary cancers (n = 28), and metastases (n = 39) using immunohistochemistry. In addition, a series of primary cancers and matched normal (n = 342) with outcome data were profiled in tissue microarrays. The intensity of EphB2 expression was assessed in the entire series by immunohistochemistry, and in a subset by in situ hybridization. Overall survival and recurrence-free survival were correlated with EphB2 protein expression in retrospective subset analyses. Epithelial EphB2 expression was shown at all stages of colorectal tumorigenesis, including the base of all normal crypts, 77% of adenomas, 82% of primary cancers, and 64% of metastases. Although homogeneous expression was observed in adenomas, the pattern of staining was focal (mean 25%) in most malignant lesions. Patients whose tumor stained 2+ for EphB2 expression (versus 0/1+) exhibited significantly prolonged overall survival: mean duration of survival, 2,514 versus 1,044 days; hazard ratio, 0.45; 95% confidence interval, 0.18 to 0.95 (P = 0.035). In summary, EphB2 is expressed in normal crypts, colorectal adenomas, primary cancers, and metastases. High levels of EphB2 expression are associated with a longer mean duration of survival in colorectal cancer.     

Association between folate levels and CpG Island hypermethylation in normal colorectal mucosa

Gene-specific promoter methylation of several genes occurs in aging normal tissues and may predispose to tumorigenesis. In the present study, we investigate the association of blood folate levels and dietary and lifestyle factors with CpG island (CGI) methylation in normal colorectal mucosa. Subjects were enrolled in a multicenter chemoprevention trial of aspirin or folic acid for the prevention of large bowel adenomas. We collected 1,000 biopsy specimens from 389 patients, 501 samples from the right colon and 499 from the rectum at the follow-up colonoscopy. We measured DNA methylation of estrogen receptor alpha (ERα) and secreted frizzled related protein-1 (SFRP1), using bisulfite pyrosequencing. We used generalized estimating equations regression analysis to examine the association between methylation and selected variables. For both ERα and SFRP1, percentage methylation was significantly higher in the rectum than in the right colon (P = 0.001). For each 10 years of age, we observed a 1.7% increase in methylation level for ERα and a 2.9% increase for SFRP1 (P < 0.0001). African Americans had a significantly lower level of ERα and SFRP1 methylation than Caucasians and Hispanics. Higher RBC folate levels were associated with higher levels of both ERα (P = 0.03) and SFRP1 methylation (P = 0.01). Our results suggest that CGI methylation in normal colorectal mucosa is related to advancing age, race, rectal location, and RBC folate levels. These data have important implications regarding the safety of supplementary folate administration in healthy adults, given the hypothesis that methylation in normal mucosa may predispose to colorectal neoplasia.     

Beta-catenin mutations are more frequent in small colorectal adenomas than in larger adenomas and invasive carcinomas

Loss of serine or threonine phosphorylation sites from exon 3 of beta-catenin has been identified in approximately half of colorectal tumors which lack adenomatous polyposis coli (APC) mutations, but the overall contribution of beta-catenin mutations to sporadic colorectal tumorigenesis is unclear. We therefore used PCR to amplify and sequence exon 3 of beta-catenin from 202 sporadic colorectal tumors. Exon 3 beta-catenin mutations were identified in 6 of 48 small (< 1 cm) adenomas, 2 of 82 large (> or =1 cm) adenomas, and 1 of 72 invasive carcinomas. Eight of the nine mutations, including all of those in the small adenomas and the invasive cancer, involved loss of serine or threonine phosphorylation sites. The percentage of beta-catenin mutations in small adenomas (12.5%) was significantly greater than that in large adenomas (2.4%) and invasive cancers (1.4%; P = 0.05 and P = 0.02, respectively). We conclude that mutation of beta-catenin can be an early, perhaps initiating, event in colorectal tumorigenesis. Small adenomas with beta-catenin mutations do not appear to be as likely to progress to larger adenomas and invasive carcinomas as other adenomas, however, with the result that beta-catenin mutations are only rarely seen in invasive cancers. This suggests that APC and beta-catenin mutations are not functionally equivalent, and that the APC gene may have other tumor suppressor functions besides the degradation of beta-catenin.