Molecular detection of p16 promoter methylation in the serum of recurrent colorectal cancer patients

We previously proved that p16 promoter methylation present in the tumors of colorectal cancer patients can be detected in the serum of those same patients using methylation-specific PCR (MSP). To seek the possibility that this technique could be applied to the monitoring of cancer recurrence, we examined the p16 methylation using MSP. We detected tumor DNA in the serum of 31 of 45 (69%) patients with recurrent colorectal cancer. No methylation was found in serum DNA of 50 patients with colorectal cancers whose corresponding tumor DNA had no methylation in p16 promoter. These results suggested that MSP might be a sensitive and useful method to detect recurrent colorectal cancer in serum.     

大肠癌组织p16基因甲基化与临床病理特征的关系

目的：研究p16基因启动子CpG区甲基化的改变与大肠癌发生及其临床病理特征的关系。方法：采用甲基化特异PCR技术（MSP法）研究大肠癌组织p16基因甲基化,并分析其与临床病理特征的关系。结果：30例大肠癌组织中有12例（40．0％）呈p16CpG区甲基化阳性。DukesC、D期组织p16CpG区甲基化发生率明显高于DukesA、B期。有转移的大肠癌组织p16甲基化发生率（84．6％）明显高于无转移者（5．9％）。结论p16启动子区甲基化导致p16抑癌基因失活,参与大肠癌的发生和发展。大肠癌组织p16CpG区甲基化与Dukes分期、肿瘤转移有关。p16甲基化可作为评估大肠癌患者预后的1个指标。     

支气管上皮细胞系BEP2D恶性转化过程中p16基因甲基化改变研究

目的 研究人支气管上皮细胞系BEP2D恶性转化过程中pl6基因甲基化改变以及pl6基因mRNA转录情况。方法 选取正常人支气管上皮细胞系BEP2D及其经α粒子照射20周(R-20)、21周(R-21)、35周(T-35)和54周(T-54)的BEP2D细胞株作为研究对象(其中R-20、R-21末发生恶性转化，而T-35、T-54已发生恶性转化)．采用甲基化特异性PCR(methylation-specific PCR，MSP)检测各细胞株中pl6基因的甲基化改变情况，再运用半定量反转录PCR(retro-translation PCR，RT-PCR)检测pl6基因mRNA在各细胞株中的表达情况。结果 ①正常BEP2D细胞株pl6基因未发生甲基化，而R-20、R-21、T-35和T-54细胞的pl6基因均发生了甲基化改变。②与正常BEP2D细胞相比，R-20、R-21、T-35和T-54细胞p16基因mRNA转录水平均降低。结论 pl6基因甲基化改变发生在肺癌形成的早期阶段。p16基因甲基化可导致p16基因mRNA转录水平降低。     

Aberrant promoter methylation of p16 in colorectal adenocarcinoma in North Indian patients

AIM: To investigate p16 gene methylation and its expression in 30 patients with sporadic colorectal adenocarcinoma in a North Indian population.METHODS: Methylation specific polymerase chain reaction was used to detect p16 gene methylation and immunohistochemistry was used to study the p16 expression in 30 sporadic colorectal tumors as well as adjoining and normal tissue specimens.RESULTS: Aberrant promoter methylation of p16 gene was detected in 12 (40%) tumor specimens, whereas no promoter methylation was observed in adjoining and normal tissue. Immunohistochemistry showed expression of p16 protein in 26 (86.6%) colorectal tumors whereas complete loss of expression was seen in 4 (13.3%) and reduced expression was observed in 12 (40%) tumors. In the adjoining mucosa, expression of p16 was in 11 (36.6%) whereas no clear positivity for p16 protein was seen in normal tissue. There was a significant difference in the expression of p16 protein in tumor tissue and adjoining mucosa (P < 0.001). The methylation of the p16 gene had a significant effect on the expression of p16 protein (P = 0.021). There was a significant association of methylation of p16 gene with the tumor size (P = 0.015) and of the loss/reduced expression of p16 protein with the proximal site of the tumor (P = 0.047). Promoter methylation and expression of p16 had no relation with the survival of the patients (P > 0.05).CONCLUSION: Our study demonstrated that promoter hypermethylation of the p16 gene results in loss/reduced expression of p16 protein and this loss/reduced expression may contribute to tumor enlargement.     

非小细胞肺癌p16基因甲基化及缺失的研究

目的 研究p16基因在非小细胞肺癌组织中的甲基化和缺失情况，探讨其在肺癌诊断中的价值。方法 应用甲基化相关的PCR及双重PCR，检测50例肺癌组织和54例正常肺组织中p16基因第1外显子5′端启动子区域CpG岛甲基化及第2外显子缺失情况。结果 p16基因在非小细胞肺癌组织中甲基化率为32.0%(16/50)。缺失率为28.0%(14/50);54例正常肺组织甲基化率为3.7%(2/54)，缺失率为0，二组比较，甲基化率（Fisher's exact=0.000)及缺失率（Fisher's exact=0.000)均有显著性差异。结论 甲基化和缺失是非小细胞肺癌p16基因失活的主要形式，检测p16基因甲基化和缺失状态可能有助于肺癌的诊断。     

Meta-analysis of 16 studies of the association of alcohol with colorectal cancer

Alcohol consumption is an established risk factor for colorectal cancer (CRC). However, while studies have consistently reported elevated risk of CRC among heavy drinkers, associations at moderate levels of alcohol consumption are less clear. We conducted a combined analysis of 16 studies of CRC to examine the shape of the alcohol–CRC association, investigate potential effect modifiers of the association, and examine differential effects of alcohol consumption by cancer anatomic site and stage. We collected information on alcohol consumption for 14,276 CRC cases and 15,802 controls from 5 case-control and 11 nested case-control studies of CRC. We compared adjusted logistic regression models with linear and restricted cubic splines to select a model that best fit the association between alcohol consumption and CRC. Study-specific results were pooled using fixed-effects meta-analysis. Compared to non-/occasional drinking (≤1 g/day), light/moderate drinking (up to 2 drinks/day) was associated with a decreased risk of CRC (odds ratio [OR]: 0.92, 95% confidence interval [CI]: 0.88–0.98, p = 0.005), heavy drinking (2–3 drinks/day) was not significantly associated with CRC risk (OR: 1.11, 95% CI: 0.99–1.24, p = 0.08) and very heavy drinking (more than 3 drinks/day) was associated with a significant increased risk (OR: 1.25, 95% CI: 1.11–1.40, p < 0.001). We observed no evidence of interactions with lifestyle risk factors or of differences by cancer site or stage. These results provide further evidence that there is a J-shaped association between alcohol consumption and CRC risk. This overall pattern was not significantly modified by other CRC risk factors and there was no effect heterogeneity by tumor site or stage.     

检测痰脱落细胞p16基因甲基化对周围型肺癌的诊断价值

目的　探讨检测痰脱落细胞p16基因甲基化对周围型肺癌的诊断价值。方法　应用甲基化特异性PCR(methylation specificPCR ,MSP)对 5 0例周围型肺结节患者及 2 0例正常人痰脱落细胞p16基因甲基化改变进行检测 ,将检测结果与术后病理报告相对照。结果　周围型肺癌痰脱落细胞 p16MSP阳性率( 2 7/ 44 ,61.4%)明显高于良性周围型肺结节 ( 1/ 6,16.7%)及正常人 ( 3 / 2 0 ,15 .0 %) ( χ2 值分别为 4.2 81和11.869,P <0 .0 5 ) ,良性周围型肺结节 p16MSP阳性率与正常人无显著性差异 ( χ2 =0 .13 6,P >0 .0 5 )。鳞癌和腺癌患者痰脱落细胞 p16MSP阳性率无显著性差异 ( χ2 =3 .416,P >0 .0 5 )。如果以痰脱落细胞 p16MSP阳性作为判断肺结节恶性的标准 ,其诊断周围型肺癌的阳性预测值为 96.4%,阴性预测值 2 2 .7%,灵敏度 61.4%,特异度 83 .0 %。结论　检测痰脱落细胞 p16基因甲基化对周围型肺癌具有辅助诊断价值     

Cloning of the 5'Upstream Region of the Rat p16 Gene and Its Role in Silencing

Hypermethylation of the 5'upstream region (5'region) of the human p16 ^CDKN2A ( p16 ) gene is known to cause silencing, which is involved in a wide range of human cancers. For the rat p16 gene, its 5'region has not been cloned, and it is uncertain whether surrogate use of exon la is adequate for analysis of p16 silencing. In this study, we observed that methylation analysis of exon la gave false positive results in three samples of normal rat mammary epitheliums and in two of six primary mammary carcinomas. Therefore, we determined the nucleotide sequence of the 5'region of the rat p16 gene. To confirm that methylation status of the 5'region is correlated with p16 expression, the methylation status was analyzed by bisulfite sequencing and methylation-specific PCR in three samples of normal mammary glands, six samples of mammary carcinomas and four cell lines. The 5'region was demethylated in all of the three normal and six carcinoma samples that fully expressed p16 . On the other hand, the 5'region was highly methylated in the 3Y1 cell line, which lacked p16 expression, but without deletion. These results showed that the methylation status of the 5'region was more closely correlated with p16 expression than that of the exon 1α and analysis of the methylation status is useful in examining p16 silencing in various rat tumors.     

Colorectal Cancers with both p16 and p14 Methylation Show Invasive Characteristics

Recent studies indicated that p16 and p14 inactivation owing to promoter methylation was important for colorectal tumorigenesis. In this study, we examined the methylation status of these genes in 86 primary colorectal cancers using methylation-specific PCR (MSP) and correlated the results with the clinicopathological features of the patients. Aberrant promoter methylation of p16 and p14 genes was detected in 43 of 86 (50%) and 25 of 86 (29%) colorectal cancers, respectively. Next, we examined the correlation of methylation status with the clinicopathological features. We found a significant difference in maximal tumor size ( P =0.022) when patients with both p16 and p14 methylation were compared to other patients. On the other hand, there was no significant difference in other factors, such as the extent of tumor and Dukes stage. These results suggested that colorectal cancer with both p16 and p14 methylation has the same invasiveness at a smaller size compared to that of the cancer with neither p16 nor p14 methylation. Inactivation of both p16 and p14 genes may result in a malignant change in colorectal cancer cells, leading to advanced cancers with a smaller size than those with p16 or p14 activity.     

炭末沉着症和p16~(ink4a)基因异常甲基化对小型肺腺癌发生进展的影响

背景与目的 炭末沉着症系长期吸入非生产性粉尘而导致各级支气管壁粘膜和肺膜内有炭末斑形成,可致支气管变形及破坏.有研究表明,炭末沉着症与小型肺腺癌的发生和进展密切相关.本研究旨在探讨炭末沉着症与p16ink4a基因异常甲基化修饰程度在小型肺腺癌发生和进展过程中的影响.方法应用Methylation Specific PCR技术检测68例原发性小型肺腺痛患者的癌组织、癌周正常组织中的p16ink4a基因启动子区域的异常甲基化修饰程度;炭末定量分析法来检测患者肺内的炭末沉着量;采用野口氏病理分型.结果 重度吸烟者(吸烟指数>600)的平均炭末沉着量明显高于轻度吸烟者(吸烟指数<600)和非吸烟者(P=0.005);重度吸烟者的p16ink4a基因异常甲基化检出率为60%,也明显高于轻度吸烟者和非吸烟者的27%(P=0.023);早期小型肺腺癌的p16ink4a基因异常甲基化检出率低于进展期和低分化小型腺癌,但无统计学意义;p16ink4a基因调控产物表达早期小型腺癌高于低分化小型腺癌(P=0.032).结论 炭末沉着定量分析与p16ink4a基因异常甲基化检测二者结合,有可能应用于对吸烟人群的肺腺癌早期发现和早期诊断.     

四种肿瘤细胞p16基因CpG岛甲基化的检测

目的:检测4种肿瘤细胞系中p16基因CpG岛甲基化的状况。方法:利用甲基化特异性PCR(MSP)检测了4种肿瘤细胞(SPC-A1、BIU-87、T24、Hep-G2)的甲基化状况。结果:除BIU-87外,其它3种肿瘤细胞p16基因都有不同程度的甲基化。结论:p16基因CpG岛的甲基化与肿瘤的发生、发展关系密切。     

Genome-wide analysis of aberrant DNA methylation for identification of potential biomarkers in colorectal cancer patients

Background: Colorectal cancer is one of the leading causes of mortality worldwide. Genome wide analysisstudies have identified sequence mutations causing loss-of-function that are associated with disease occurrence andseverity. Epigenetic modifications, such DNA methylation, have also been implicated in many cancers but haveyet to be examined in the East Asian population of colorectal cancer patients. Methods: Biopsies of tumors andmatched non-cancerous tissue types were obtained and genomic DNA was isolated and subjected to the bisulphiteconversion method for comparative DNA methylation analysis on the Illumina Infinium HumanMethylation27BeadChip. Results: Totals of 258 and 74 genes were found to be hyper- and hypo-methylated as compared tothe individual’s matched control tissue. Interestingly, three genes that exhibited hypermethylation in theirpromoter regions, CMTM2, ECRG4, and SH3GL3, were shown to be significantly associated with colorectalcancer in previous studies. Using heatmap cluster analysis, eight hypermethylated and 10 hypomethylated geneswere identified as significantly differentially methylated genes in the tumour tissues. Conclusions: Genome-widemethylation profiling facilitates rapid and simultaneous analysis of cancerous cells which may help to identifymethylation markers with high sensitivity and specificity for diagnosis and prognosis. Our results show thepromise of the microarray technology in identification of potential methylation biomarkers for colorectal cancers.     

p16基因甲基化对非小细胞肺癌发病的影响

目的探讨p16基因甲基化对非小细胞肺癌发病的影响。方法原发性肺癌患者47例及同期无呼吸系统疾病又未患任何肿瘤同性别者94例作对照,采用甲基化特异性PCR等技术,检测p16基因甲基化。结果p16基因甲基化在肺癌组织和正常肺组织中检出率分别为44.7%(21/47)和17.0%(8/47),两者有显著差异(P<0.05)。37例非小细胞肺癌吸烟者中有21例肺癌组织发生p16基因甲基化,而10例非小细胞肺癌非吸烟者中无一例肺癌组织发生p16基因甲基化。p16基因甲基化与年龄、饮酒、肺癌病理分型及肺癌临床分期之间均无明显的相关性(P>0.05)。结论p16基因甲基化与非小细胞肺癌发生的关系非常密切,p16基因甲基化与吸烟有关。检测p16基因甲基化与否,可能有助于肺癌的诊断。     

子宫内膜癌中p16基因缺失及CpG岛甲基化的研究

目的　研究子宫内膜癌中 p16基因缺失及CpG岛甲基化情况。 方法　用PCR技术检测 p16基因在子宫内膜癌中的纯合性缺失及第一外显子异常甲基化。结果　 36例癌组织中 9例发生基因缺失 ,12例发生甲基化 ,未发现基因缺失与甲基化同时存在的病例。结论　 1.p16基因缺失与子宫内膜癌组织学分级严重程度和临床分期呈正相关 ;2 .5’CpG甲基化可能是 p16基因失活的重要机理 ,参与子宫内膜癌发生、发展。     

CDKN2/p16基因5′-CpG岛SmaI位点甲基化与肺癌的关系

目的　研究CDKN2 /p16基因 5′端调控序列CpG岛甲基化的状态与肺癌发生发展的关系。方法　采用对甲基化敏感的核酸内切酶SmaⅠ ,酶切基因组DNA的方法 ,对 89例肺癌标本和 10例正常肺组织的CDKN2 /p16基因进行Southern杂交分析。结果　 89例肺癌中 ,CDKN2 /p16基因甲基化者 15例 ,甲基化频率为 16 .9%。 42例p16蛋白阴性的肺癌患者中 ,有 12例发生甲基化 ,甲基化频率为 2 8.6 % ;另有 47例p16蛋白阳性患者中仅有 3例发生甲基化。 10例正常肺组织中均未发现CDKN2 /p16基因有甲基化现象。结论　CDKN2 /p16基因 5′端CpG岛甲基化是该基因失活的重要机制 ,是肺癌细胞区别于正常细胞的分子事件之一 ,可能参与肺癌的发生发展过程     

宫颈癌中p16基因启动子异常甲基化的检测

目的:探讨宫颈癌组织及外周血浆中p16基因启动子异常甲基化的状况及其在宫颈癌诊断中的价值.方法:用甲基化特异性PCR技术对宫颈癌组织,正常宫颈组织及相对应血浆中p16基因进行甲基化的检测.结果:45例宫颈癌组织中p16基因异常甲基化率为33.3％(15/45),相对应血浆中p16基因甲基化的检出率为20％(9/45),而正常对照组织未检出甲基化.血浆中甲基化的改变与宫颈癌组织甲基化状态显著相关(P＜0.05).p16基因甲基化发生率与年龄、病理分级、临床分期之间无统计学相关性(P＞0.05).结论:p16基因CpG岛甲基化是宫颈癌发生的高频事件,其甲基化检测在宫颈癌早期诊断中有一定的应用价值.     

Inhibition of VEGF induces cellular senescence in colorectal cancer cells

Vascular endothelial growth factor (VEGF) inhibitors, such as bevacizumab, have improved outcomes in metastatic colorectal cancer (CRC). Recent studies have suggested that VEGF can delay the onset of cellular senescence in human endothelial cells. As VEGF receptors are known to be upregulated in CRC, we hypothesized that VEGF inhibition may directly influence cellular senescence in this disease. In our study, we observed that treatment with bevacizumab caused a significant increase (p < 0.05) in cellular senescence in vitro in several CRC cells, such as MIP101, RKO, SW620 and SW480 cells, compared to untreated or human IgG-treated control cells. Similar results were also obtained from cells treated with a VEGFR2 kinase inhibitor Ki8751. In vivo, cellular senescence was detected in MIP101 tumor xenografts from 75% of mice treated with bevacizumab, while cellular senescence was undetectable in xenografts from mice treated with saline or human IgG (p < 0.05). Interestingly, we also observed that the proportion of senescent cells in colon cancer tissues obtained from patients treated with bevacizumab was 4.4-fold higher (p < 0.01) than those of untreated patients. To understand how VEGF inhibitors may regulate cellular senescence, we noted that among the two important regulators of senescent growth arrest of tumor cells, bevacizumab-associated increase in cellular senescence coincided with an upregulation of p16 but appeared to be independent of p53. siRNA silencing of p16 gene in MIP101 cells suppressed bevacizumab-induced cellular senescence, while silencing of p53 had no effect. These findings demonstrate a novel antitumor activity of VEGF inhibitors in CRC, involving p16.