激酶4抑制因子家族基因表达的激活对肠癌细胞增殖侵袭的影响

目的探讨激活激酶4抑制因子（INK4）家族（P15ink4b和P16ink4a／CDKN2）基因表达对结肠癌细胞增殖和迁移能力的影响。方法应用1×10^-7、5×10^-7及1×10^-6mol／L不同浓度的特异性DNA甲基转移酶抑制剂（5-Aza-CdR）对结肠癌RKO细胞进行去甲基化处理（分别为A、B、C3个实验组）,另设阳性对照组（未经处理的RKO细胞）。Western blot法检测INK4家族基因的蛋白表达：软琼脂克隆细胞集落实验评估体外致瘤情况;Transwell小室实验评估体外迁移情况。将各组RKO细胞注射BALB／c裸鼠（每组10只）,通过称量瘤体的重量和体积评估体内成瘤情况。结果A、B、C3组实验组细胞中P15ink4b和P16ink4a／CDKN2蛋白表达分别为阳性对照组的1．13、1．38、1．92倍和1．11、1．45、2．14倍。体外实验显示,B组和C组的细胞集落数明显少于阳性对照组（P〈0．05）;3组实验组的细胞迁移数均明显少于阳性对照组（P〈0．05）。体内实验显示,相对于阳性对照组,3组实验组裸鼠的抑瘤率分别为2．1％、16．8％和26．2％,差异有统计学意义（P〈0．01）。结论激活INK4家族基因的表达能有效抑制结肠癌细胞的增殖和迁移。     

肝硬化组织中p16INK4a和Rb的基因甲基化状态和蛋白表达

目的：探讨肝硬化组织中p16INK4a和视网膜母细胞瘤易感基因（Rb基因）启动子区域的甲基化状态与其蛋白的表达的关系。方法：分别采用PCR和免疫组织化学方法测定65例肝硬化患者和20例正常人肝组织中p16INK4a和Rb启动子区域甲基化状况和蛋白的表达。结果：20例正常肝组织（对照组肝组织）中均未检测到p16INK4a和Rb甲基化异常,肝硬化组肝组织中p16INK4a和Rb基因甲基化率分别为40.0%（26/65）和36.9%（24/65）;p16INK4a和Rb蛋白表达的积分光密度（IOD）在正常肝组织为225.7±27.4和254.7±34.8,在肝硬化组肝组织中为32.4±7.5和45.2±6.4,差异均有统计学意义（均P<0.05）。结论：肝硬化组织中存在p16INK4a和Rb异常甲基化和p16INK4a和Rb蛋白的表达降低,由此导致的细胞周期失控可能参与了肝硬化的发生发展过程。     

植物类雌激素杨梅素对结肠癌细胞系RKO生长的影响

目的检测一种植物类雌激素杨梅素对人结肠癌细胞系RKO生长的影响,并初步探讨其作用机制。方法采用噻唑蓝(MTT)比色法检测杨梅素对RKO细胞系生长的影响;流式细胞仪技术检测杨梅素对细胞周期的影响;半定量反转录聚合酶链反应(RT-PCR)确定杨梅素对抑癌基因p16INK4a表达的影响。结果MTT法显示杨梅素处理组对结肠癌细胞系生长有明显抑制作用;流式细胞仪分析结果显示,经杨梅素处理后RKO细胞周期明显阻滞在G0/G1期;RT-PCR结果显示杨梅素恢复了RKO细胞系p16INK4a的转录。结论杨梅素对RKO细胞系生长有明显的抑制作用,杨梅素可能通过上调抑癌基因p16INK4a的表达使RKO细胞周期阻滞于G0/G1期。     

凋亡蛋白酶活化因子-1基因甲基化在骨肉瘤细胞株中的作用

目的 检测骨肉瘤细胞株中凋亡蛋白酶活化因子(APAF)-1基因启动子区域甲基化状态及该基因mRNA表达,观察APAF-1基因对骨肉瘤形成的影响.方法 以骨肉瘤细胞株MG63和Hs888T为研究对象,提取DNA,经重亚硫酸钠处理后,采用限制性酶切图谱分析(COBRA)检测APAF-1基因CpG岛的甲基化情况,使用不同浓度(0、1×10~(-7)、3×10~(-7)mol/L)的DNA甲基转移酶抑制剂5-氮杂2'-脱氧胞苷(5-Aza-CdR)处理骨肉瘤细胞株4、10、20d,采用实时定量聚合酶链反应(QT-PCR)检测Apaf-1 mRNA表达水平的变化.结果 在Hs888T细胞株中APAF-1基因存在CpG岛甲基化并且随着5-Aza-CdR浓度的增加Apaf-1 mRNA表达水平也在增加.3×10~(-7)mol/L的5-Aza-CdR处理Hs888T细胞株20 d与对照组比较差异有统计学意义(P<0.05).结论 Hs888T细胞株中APAF-1基因异常表达与APAF-1基因启动子区域CpG岛甲基化有关,提示APAF-1基因甲基化可能参与某些骨肉瘤的发生.     

5-氮-2′-脱氧胞苷对RKO结肠癌细胞株maspin基因去甲基化的转录调节作用

目的探讨 DNA5′ CpG岛去甲基化对 RKO结肠癌细胞株 maspin基因的转录调控作用及对细胞株生长增殖的生物学影响 ,寻找抗癌治疗的新靶点.方法应用甲基化特异性 PCR(methylation specific PCR, MSP)检测 RKO结肠癌细胞株 maspin基因核心启动子区 CpG岛甲基化情况;用特异性 DNA甲基转移酶抑制剂 5-氮- 2′-脱氧胞苷 (5- aza- 2′- deoxycytidine, 5- aza- CdR)作用结肠癌细胞株 72 h后 ,逆转录聚合酶链反应 (RT- PCR)检测 maspin mRNA表达,四唑盐 (MTT)比色、流式细胞仪检测用药前后 RKO细胞株生长存活率和细胞周期的变化.结果 RKO结肠癌细胞株 maspin基因核心启动子区存在 CpG岛甲基化.与对照组相比, 3组不同浓度 5- aza- CdR作用后, maspin基因 mRNA表达分别增加了 10.89、 16.91和 23.97倍,明显抑制肿瘤细胞生长,阻滞细胞周期于 G0/G1期, 诱导细胞凋亡, 凋亡率分别为 5.17%、 8.71%和 11.23%.结论 RKO结肠癌细胞株 maspin基因 5′端核心启动子甲基化可能是导致该基因表达沉默的主要原因;特异性甲基转移酶抑制剂 5- aza- CdR能较好地逆转 RKO细胞 DNA异常甲基化,并有效地激活因高甲基化所致 maspin基因沉默的再转录,诱导该基因表达,从而抑制肿瘤细胞生长,诱导细胞凋亡.     

人原发性肝癌中多种基因CpG岛甲基化研究进展

1概述在表观遗传学(epigenesis※)这个发展非常快的领域,DNA甲基化,组蛋白去乙酰化和RNA介导是基因沉默(silencing)的三大主要原因。在人类基因组DNA中,约3%～4%的胞嘧啶碱基以5甲基胞嘧啶形式存在,结果导致在人类正常组织细胞DNA中,5甲基胞嘧啶占所有核甘酸碱基的0.75%～1%。大约70%～80%的5甲基胞嘧啶存在于CpG序列中,CpG二核甘酸集中的区域称之为CpG岛,这部分通常是未甲基化,这些CpG岛跨过许多基因的5’末端———包括启动子,未翻译区和第一外显子。现在知道的哺乳类基因组中至少一半基因的启动子区存在CpG岛,其甲基化只发生在…     

5-氮-2''''-脱氧胞苷对RKO结肠癌细胞株maspin基因去甲基化的转录调节作用

目的探讨DNA5'CpG岛去甲基化对RKO结肠癌细胞株maspin基因的转录调控作用及对细胞株生长增殖的生物学影响,寻找抗癌治疗的新靶点。方法应用甲基化特异性PCR(methylationspecificPCR,MSP)检测RKO结肠癌细胞株maspin基因核心启动子区CpG岛甲基化情况;用特异性DNA甲基转移酶抑制剂5-氮-2'-脱氧胞苷(5-aza-2'-deoxycytidine,5-aza-CdR)作用结肠癌细胞株72h后,逆转录聚合酶链反应(RT-PCR)检测maspinmRNA表达,四唑盐(MTT)比色、流式细胞仪检测用药前后RKO细胞株生长存活率和细胞周期的变化。结果RKO结肠癌细胞株maspin基因核心启动子区存在CpG岛甲基化。与对照组相比,3组不同浓度5-aza-CdR作用后,maspin基因mRNA表达分别增加了10.89、16.91和23.97倍,明显抑制肿瘤细胞生长,阻滞细胞周期于G0/G1期,诱导细胞凋亡,凋亡率分别为5.17%、8.71%和11.23%。结论RKO结肠癌细胞株maspin基因5'端核心启动子甲基化可能是导致该基因表达沉默的主要原因;特异性甲基转移酶抑制剂5-aza-CdR能较好地逆转RKO细胞DNA异常甲基化,并有效地激活因高甲基化所致maspin基因沉默的再转录,诱导该基因表达,从而抑制肿瘤细胞生长,诱导细胞凋亡。     

胰液中K-ras基因突变和p16基因甲基化改变联合检测在胰腺癌诊断中的初步研究

目的 探讨胰液中K-ras基因突变和p16基因启动子区5′CpG岛甲基化联合检测在胰腺癌诊断中的价值.方法 采用ERCP下放置鼻胰管收集胰液,采用聚合酶链反应-限制性片段长度多态性分析(PCR-RFLP)法检测胰液中K-ras基因12密码子点突变,PCR-MSP法检测胰液中p16基因甲基化状态.结果 所有胰液标本均成功抽提出DNA,30例胰腺疾病病人胰液标本同时进行了K-ras基因突变和p16基因启动子区5′CpG岛甲基化检测,其中20例胰腺癌病人胰液中K-ras基因突变率为70%(14/20),p16基因甲基化率为35%(7/20),8例慢性胰腺炎中K-ras基因突变率为25%(2/8),2例胰腺囊腺瘤病人中K-ras基因突变率为50%(1/2),慢性胰腺炎和胰腺囊腺瘤病人胰液中无p16基因甲基化.单纯胰液中K-ras基因突变检测诊断胰腺癌的敏感性为70%(14/20),特异性为70%(7/10),阳性预测值为82.4%(14/17),阴性预测值为53.8%(7/13),诊断准确性70%(21/30).胰液中p16基因甲基化与K-ras基因联合诊断胰腺癌的敏感性为70%(14/20),特异性为100%(10/10),阳性预测值为100%(14/14),阴性预测值为62.5%(10/16),诊断准确性80.0%(24/30).结论 鼻胰管收集的胰液可用于分子生物学检测,联合检测胰液中K-ras基因突变和p16基因启动子区5′CpG岛甲基化更有助于胰腺癌的诊断.     

5-杂氮-2′-脱氧胞苷对前列腺癌PC-3细胞生物学行为的影响

目的 检测E-cadherin基因在激素非依赖性前列腺癌(HIPC)细胞上的表达及启动子CpG岛甲基化,探讨甲基化抑制剂5-杂氮-2′-脱氧胞苷(5-Aza-CdR)对HIPC细胞的影响及意义.方法 2.5、5.0、10.0 μmol/L的5-Aza-CdR处理PC-3细胞72h后,甲基化特异性聚合酶链反应(MSP)方法检测CpG岛甲基化改变,逆转录—聚合酶链反应(RT-PCR)方法检测E-cadherin mRNA变化,Westernblot方法检测E-cadherin蛋白变化,Transwell小室检测细胞侵袭性改变.结果 HIPC的E-cadherin启动子CpG岛甲基化呈阳性,基因表达缺失,细胞侵袭性明显.经5-Aza-CdR作用之后,CpG岛甲基化阳性明显减弱(P＜0.05),E-cadherin基因恢复表达(P＜0.05),PC-3细胞的侵袭性下降约59.68％,且与药物的浓度呈正相关.结论 5-Aza-CdR可逆转PC-3细胞E-cadherin启动子CpG岛的异常甲基化,诱导mRNA转录和蛋白的表达,并降低癌细胞的侵袭性.     

5-氮-2’-脱氧胞苷对RKO结肠癌细胞株maspin基因去甲基化的转录调节作用

目的 探讨DNA5’CpG岛去甲基化对RKO结肠癌细胞株maspin基因的转录调控作用及对细胞株生长增殖的生物学影响，寻找抗癌治疗的新靶点。方法 应用甲基化特异性PCB（methylation specific PCR，MSP）检测RKO结肠癌细胞株maspin基因核心启动子区CpG岛甲基化情况；用特异性DNA甲基转移酶抑制剂5-氮-2’-脱氧胞苷（5-aza-2＇-deoxycytidine，5-aza-CdR）作用结肠癌细胞株72h后，逆转录聚合酶链反应（RT-PCR）检测nlaspin mRNA表达，四唑盐（MTT）比色、流式细胞仪检测用药前后RKO细胞株生长存活率和细胞周期的变化。结果 RKO结肠癌细胞株maspin基因核心启动子区存在CpG岛甲基化。与对照组相比，3组不同浓度5-aza-CdR作用后。maspin基因mRNA表达分别增加了10．89、16．91和23．97倍。明显抑制肿瘤细胞生长，阻滞细胞周期于G0／G1期，诱导细胞凋亡，凋亡率分别为5．17％、8．71％和11．23％。结论 RKO结肠癌细胞株maspin基因5’端核心启动子甲基化可能是导致该基因表达沉默的主要原因；特异性甲基转移酶抑制剂5-aza-CdR能较好地逆转RKO细胞DNA异常甲基化，并有效地激活因高甲基化所致maspin基因沉默的再转录，诱导该基因表达，从而抑制肿瘤细胞生长，诱导细胞凋亡。     

p21WAF1/CIP1 gene is inactivated in metastatic prostatic cancer cell lines by promoter methylation

INTRODUCTION: p21WAF1/CIP1 may act as a tumour suppressor gene (TSG) and loss of the p21WAF1/CIP1 gene has been reported in several solid tumours. The aim of this study was to see whether p21WAF1/CIP1 was expressed in metastatic prostate cancer cell lines and to determine if there was methylation of the p21WAF1/CIP1 promoter. METHOD: PC3, LNCaP and DU145 metastatic prostate cancer cell lines, 1542NP normal prostate, and RD rhabdomyosarcoma cell lines were cultured in the demethylating agent 5-Aza-2 deoxycytidine (5-Aza-CdR). p21WAF1/CIP1 mRNA expression was analysed by RT-PCR. DNA from untreated cell lines was modified with sodium bisulphite and promoter sequencing was performed. RESULTS: p21WAF1/CIP1 was expressed at low or undetectable levels in metastatic prostate cancer cell lines but expression was reactivated by treatment with 5-Aza-CdR. Sequence analysis of the promoter region revealed several sites of methylation at the 5' end of a CpG island in the PC3, LNCaP and DU145 cell line DNA but not in the normal prostate control DNA. Most notably the Sis-inducible element (SEI)-1-a STAT1-binding site, was methylated. CONCLUSIONS: In this study, we show that p21WAF1/CIP1 expression in metastatic prostate cancer cell lines is enhanced as a result of demethylation of the DNA. Furthermore, several cytosine residues in the promoter region are methylated, including critical binding sites. The inhibition of the STAT1-signalling pathway by methylation of the promoter may inactivate the p21WAF1/CIP1 TSG in prostate cancer.     

CDKN2／p16^INK4a基因克隆,探针制备及其在肺癌基因诊断中的 …

OBJECTIVES: To clone CDKN2/p16(INK4a) gene, prepare its probe, and to study the change of CDKN2/p16(INK4a) gene in lung cancers. METHODS: Total RNA of normal lung tissue was extracted, CDKN2/p16(INK4a) gene cDNA synthesized, and CDKN2/p16(INK4a) gene recombinant vector, constructed. Southern blot was used to study CDKN2/p16(INK4a) gene in 46 cases of lung cancers, 3 cases of normal lung tissues, 6 cases of lung tissues near cancer, and 3 cases of lymph nodes with lung cancer metastasis. RESULTS: Cloned CDKN2/p16(INK4a) cDNA was proved by enzyme digestion and sequencing. Southern blot showed 4.3 kb band in normal lung tissues and lung tissues near cancers, and deletion of CDKN2/p16(INK4a) gene in cancer tissues and lymph nodes with lung cancer metastasis, with a deletion rate of 17.4% (8/46). CONCLUSION: CDKN2/p16(INK4a) gene may play a role to some extent in progression of lung cancers.     

Concordant loss of MTAP and p16/CDKN2A expression in gastroesophageal carcinogenesis: evidence of homozygous deletion in esophageal noninvasive precursor lesions and therapeutic implications

The gene that encodes methylthioadenosine phosphorylase (MTAP), an enzyme involved in adenine and methionine salvage pathways, is located on chromosome 9p21 telomeric to the p16INK4A/CDKN2A tumor suppressor gene. Inactivation of the p16INK4A/CDKN2A gene occurs by three different mechanisms: hypermethylation of the gene promoter, intragenic mutation coupled with loss of the second allele, and homozygous deletion. Immunohistochemical labeling for the p16INK4A/CDKN2A gene product parallels gene status but does not elucidate the mechanism of gene inactivation. Since the MTAP gene is often co-deleted with p16INK4A/CDKN2A, concurrent immunolabeling for both proteins can identify cases with homozygous p16INK4A/CDKN2A gene deletion. MTAP loss itself has therapeutic implications since it may confer selective sensitivity to inhibitors of de novo purine biosynthesis, such as L-alanosine. Twelve tissue microarrays were constructed from 92 cases of Barrett-associated adenocarcinomas and precursor lesions and 112 cases of gastric adenocarcinoma and precursor lesions comprising 1161 individual cores. Multiple cores were arrayed from any given case, and when available, included the entire histologic spectrum of intestinal metaplasia-dysplasia-carcinoma. Tissue microarrays were labeled with monoclonal antibodies against MTAP protein (clone 6.9, Salmedix, Inc) and p16 (clone 16P07, Neomarkers). Complete loss of labeling was considered negative, while any labeling (p16: nuclear; MTAP: cytoplasmic and nuclear) was considered positive. Loss of MTAP labeling occurred exclusively in conjunction with loss of p16 labeling, confirming that the previous findings from this group that concurrent loss of MTAP and p16 labeling is a surrogate marker of 9p21 homozygous deletions. Complete loss of MTAP and p16 was seen in 4 of 25 (16%) patients with Barrett's esophagus, 4 of 18 (22%) with low-grade dysplasia, 5 of 39 (13%) with high-grade dysplasia, 17 of 78 (22%) with invasive adenocarcinoma, and 8 of 36 (22%) of metastases. There were 7 cases of esophageal adenocarcinoma with loss of both MTAP and p16 for which precursor lesions were available. In 6 on these 7 cases (85%), the precursor lesion(s) had loss of both MTAP and p16. Lack of MTAP and p16 expression was seen in 11 of 106 (10%) cases of gastric adenocarcinoma. All metaplastic (30 biopsies from 20 cases) and dysplastic (15 biopsies from 13 cases) gastric tissues had both intact MTAP and p16INK4A/CDKN2A gene products. No precursor lesions were available from the gastric cancers that had loss of both MTAP and p16. Two benign gastric hyperplastic polyps also had intact p16 and MTAP. Concurrent MTAP and p16 loss detected by immunohistochemistry can serve as a convenient surrogate for p16INK4A/CDKN2A gene homozygous deletion in archival tissues. Inactivation of p16INK4A/CDKN2A by homozygous deletion appears to be an early event in Barrett carcinogenesis, occurring in noninvasive precursor lesions, including nondysplastic Barrett mucosa, in subsets of cases. In the absence of MTAP, cells depend exclusively on the de novo synthesis pathway for production of adenosine. This loss of MTAP during 9p21 homozygous deletion might be exploited therapeutically using de novo purine synthesis antimetabolites to treat a subset of invasive gastroesophageal adenocarcinomas and esophageal precursor lesions.     

The expression of key cell cycle markers and presence of human papillomavirus in squamous cell carcinoma of the tonsil

BACKGROUND: Chemical carcinogens induce squamous cell carcinoma (SCC) of the head and neck by targeting the p53 and the retinoblastoma (pRb) pathways. Human papillomavirus (HPV) might have an etiologic role in these cancers at particular sites. Few studies have compared cell cycle protein expression in HPV-positive and HPV-negative tumors in this region. METHODS: Fifty tonsil SCCs were analyzed for HPV by PCR and for expression of cell cycle proteins (p53, pRb, p16(INK4A), p21(CIP1/WAF1), p27(KIP1), and cyclinD1) by immunohistochemistry. RESULTS: HPV was present in 42%; almost all were type 16. There were statistical associations between HPV positivity and reduced expression of pRb and cyclinD1, overexpression of p16, and younger patient age. Tumor with down-regulated p27 tended to have down-regulated pRb and p21. CONCLUSIONS: HPV-positive tonsil SCCs have distinct molecular pathways. Their association with younger patient age suggests that they are biologically distinct from HPV-negative tumors.     

Assessing the use of p16(INK4a) promoter gene methylation in serum for detection of bladder cancer

OBJECTIVE: This study was undertaken to investigate whether hypermethylation in p16(INK4a) gene promoter could serve as plasma biomarker of bladder cancer. METHODS AND PATIENTS: We examined the p16(INK4a) status using methylation-specific PCR in 86 cancer patients and 49 controls (31 healthy people and 18 patients with benign urological diseases). RESULTS: The p16(INK4a) methylation was found in 22% of the serum samples and in 26% of the bladder cancer biopsies; one of them with carcinoma in situ. The presence of hypermethylated p16(INK4a) in serum seems to be a product from tumour cells because a strong statistical association was found between both matched DNA signals (p<0.0001). Using the control group, the presence of methylated p16(INK4a) in the serum of individuals with suspicion of bladder cancer was found to be associated with the tumour presence (p=0.0009). Aberrant p16(INK4a) methylation was also observed in one non-cancer patient, which is undergoing further assessment. CONCLUSIONS: According with our results, methylation of p16(INK4a) promoter may be involved in the bladder cancer genesis and the presence of p16(INK4a) methylated in serum of these patients could be useful in the cancer diagnosis with values of sensitivity, specificity and positive predictive value of 0.226, 0.950 and 0.98, respectively. These figures support the use of methylated p16(INK4a) as a new class of tumour marker in bladder cancer.     

Opposing roles for p21(waf1/cip1) and p27(kip1) in enterocyte differentiation, proliferation, and migration

BACKGROUND: Originating from proliferating stem cells of the intestinal crypt, enterocytes differentiate as they migrate up the crypt-villus axis. A regulatory role of the cyclin-dependent kinase inhibitors p21(waf1/cip1) and p27(kip1) in these processes has been suggested by in vitro models. We sought to determine the effect of p21(waf1/cip1) and p27(kip1) deficiency on enterocyte differentiation, proliferation and migration. METHODS: Three strains of mice including control (C57Bl/6), p27(kip1)-null, and p21(waf1/cip1)-null were studied. Enterocyte differentiation was evaluated by immunostaining for intestinal alkaline phosphatase, by colorimetric assaying for intestinal alkaline phosphatase and sucrase enzyme activity, and by polymerase chain reaction for intestinal fatty acid-binding protein and villin-messenger RNA in enterocytes extracted by laser capture microdissection. Rates of enterocyte proliferation and migration were determined by 5-bromo 2-deoxyuridine immunostaining after a 50% small-bowel resection (SBR). RESULTS: Compared with controls, p27(kip1)-null mice demonstrated minimal differentiation but maintained a normal proliferative response to SBR. Contrarily, p21(waf1/cip1)-null mice demonstrated greater enterocyte differentiation without significant increases in enterocyte proliferation after SBR. CONCLUSIONS: These findings suggest that p21(waf1/cip1) and p27(kip1) have distinctive and opposing roles in the pathogenesis of enterocyte differentiation, proliferation, and migration.     

p16(INK4a) alterations in chronic pancreatitis-indicator for high-risk lesions for pancreatic cancer

BACKGROUND. p16(INK4a) alterations are considered to be an early event in pancreatic tumorigenesis and have been described in duct lesions adjacent to pancreatic cancers. This study evaluates whether duct lesions in chronic pancreatitis tissues of patients without pancreatic cancer also harbor genetic alterations in the p16(INK4a) tumor-suppressor gene, and thus represent high-risk precursors for pancreatic cancer. METHODS. Tissues were obtained from 20 pancreatic specimens taken from patients operated on for histologically verified chronic pancreatitis. Pancreatic intraductal neoplasias (PanIN) were identified in hematoxylin-and-eosin-stained slides. p16 protein expression was investigated immunohistochemically in all specimens. DNA from PanIN and non-PanIN tissue was analyzed genetically for p16(INK4a) mutations by single-strand conformation variation analysis and direct sequencing of the encoding region. Additionally, p16(INK4a) promoter methylation was analyzed by a methylation specific polymerase test. RESULTS. PanIN-1a lesions were identified in 10 of the 20 chronic pancreatitis specimens. Four of these 10 PanIN specimens (40%), but none of the 20 non-PanIN tissues, revealed a loss of p16 expression in immunohistochemistry. The mutational analysis of the p16(INK4a) gene showed 1 known polymorphism (c.442G > A; A148T) but no mutations. Two of the 10 specimens with PanIN revealed an inactivating hypermethylation of the p16(INK4a) promoter. CONCLUSIONS. This study shows for the first time that p16(INK4a) alterations can be observed in a considerable number of PanIN1 in chronic pancreatitis tissues not associated with pancreatic cancer. Therefore, p16(INK4a) alterations, especially promoter methylation, might indicate high-risk precursors in chronic pancreatitis that might progress to cancer.     

胃肠间质瘤中9p21区域杂合子丢失及P16蛋白表达研究

目的 探讨染色体9p21区域杂合子丢失（LOH）及相关的P16INK4A（CDKN2A）抑癌基因的表达与胃肠间质瘤（GIST）侵袭行为及预后的关系.方法 采用微卫星分析方法检测51例GIST标本中9p21区域D9S1751、D9S1846、D9S942和D9S1748 4个微卫星位点的LOH现象,并采用免疫组织化学技术,对D9S942位点相邻的CDKN2A抑癌基因产物P16蛋白的表达,分析P16蛋白表达缺失与GIST临床病理特征和预后的关系.结果 51例GIST标本中有2例9p21区域4个微卫星位点均为纯合子（无效信息）,其余49例9p21区域的LOH率：D9S1751为37.0%（10/27）、D9S1846为37.5%（12/32）、D9S942为42.1%（16/38）、D9S1748为24.2%（8/33）,总LOH率为63.3%（31/49）.P16蛋白在GIST标本中的阴性表达率为41.2%（21/51）,阳性率为58.8%（30/51）.高度与低或极低度侵袭风险组P16阴性表达率分别为60%（12/20）和23.5%（4/17）,差异有统计学意义（P＜0.05）.P16阴性与阳性表达组5年生存率分别为70.8%和92.0%,差异有统计学意义（P＜0.05）.结论 9p21区域的LOH在GIST中普遍存在 CDKN2A抑癌基因可能参与GIST的发生发展 P16蛋白与GIST侵袭风险及预后关系密切.