原发胃癌中p16和p15基因表达及甲基化异常

为检测胃癌组织中抑癌基因p16,p15及其启动子区甲基化状态和P16、P15蛋白表达情况。选择p16、p15基因及启动子区域，用PCR－SSCP、MSP（甲基化特异的PCR）和测序法对100例胃癌患者的癌组织、癌旁正常组织和5例正常组织进行检测，同时用免疫组化法检测了癌组织和正常对照组织的P16和P15的表达。结果发现癌组织p16和p15基因启动子区甲基化率显著高于癌旁正常组织和正常对照；胃癌组织中，71％的病例P16表达阴性，54％的病例具有p16基因启动子区的高甲基化，无突变和纯合缺失检出；11％的病例P15表达阴性，9％的病例具有p15基因启动子区的高甲基化，p15异常与低分化胃癌有关，p15基因内含子1和外显子1内各发现1例DNA序列改变；癌组织中p16和p15基因启动子区甲基化与其蛋白表达密切相关。结果显示p16基因启动子区域高甲基化是胃癌中p16基因失活的关键因素之一，并在胃癌的发生发展中发挥重要作用；p15基因启动子区域高甲基化在胃癌中起一定作用。     

食管鳞状细胞癌中p16基因甲基化及其表达

目的：探讨食管鳞状细胞癌p16／INK4基因启动子区高甲基化和p16、cyclinD1蛋白表达的意义。方法：用甲基化特异性PCR（MSP）法检测p16／INK4基因启动子区的高甲基化，用免疫组织化学方法检测p16、cyclind1蛋白的表达。结果：30例食管鳞状细胞癌中7例p16免疫组织化学阳性，15例cyclinD1阳性，组织学和统计学分析显示p16与cyclinD1的表达呈负相关。4例检出p16／INK4基因启动子区高甲基化，但与p16失表达无统计学意义。结论：（1）在食管鳞状细胞癌可检出p16／INK4基因启动子区的高甲基化，而甲基化不是引起p16失表达的主要原因。（2）p16与cyclinD1的表达呈负相关，提示细胞周期调控因子之间可能存在相互影响表达的反馈机制。     

乳腺癌中p16INK4a和视网膜母细胞瘤基因甲基化状况及其表达

目的 研究乳腺癌及癌旁增生组织中p16INK4a和视网膜母细胞瘤(RB)基因启动子区域的甲基化状况,并探讨基因异常甲基化与蛋白表达及其临床意义.方法 采用甲基化特异性PCR方法 对46例乳腺癌、22例癌旁增生组织及7例正常乳腺组织中p16INK4a和RB基因启动子区域甲基化状况进行检测,并采用免疫组织化学SP法对p16INK4a蛋白表达情况进行相应检测.结果 乳腺癌、癌旁增生组织和正常乳腺组织中p16INK4a基因的甲基化率分别为23.9%(11/46)、18.2%(4/22)、1/7;RB基因的甲基化率分别为10.8%(5/46)、9.1%(2/22)、0(0/7);肿瘤组织、癌旁增生组织和正常乳腺组织中p16INK4a基因、RB基因甲基化率差异均无统计学意义(P>0.05).正常乳腺组织、癌旁增生组织、乳腺癌中p16INK4a蛋白表达阳性率分别为7/7、60.8%(28/46)和81.8%(18/22),三者之间差异无统计学意义(P>0.05);肿瘤组织中p16INK4a蛋白表达与肿瘤分级相关(P<0.05);肿瘤组织中p16INK4a甲基化状况与其蛋白表达、肿瘤分级、ER表达阴性具有相关性(P<0.05),与肿瘤大小、淋巴结转移、年龄均不相关;RB基因甲基化状态与肿瘤分级、肿瘤大小、ER表达及年龄均无相关性,但与淋巴结转移相关(P<0.05).结论 p16INK4a基因异常甲基化可能在乳腺癌发生过程中作用有限,但在肿瘤的演进中发挥作用;RB基因甲基化检测对于分析乳腺癌进展及预后情况可能有一定参考价值;p16INK4a基因甲基化是p16INK4a蛋白失表达的机制之一.     

乳腺癌中p16INK4a和视网膜母细胞瘤基因甲基化状况及其表达

目的 研究乳腺癌及癌旁增生组织中p16INK4a和视网膜母细胞瘤(RB)基因启动子区域的甲基化状况,并探讨基因异常甲基化与蛋白表达及其临床意义.方法 采用甲基化特异性PCR方法 对46例乳腺癌、22例癌旁增生组织及7例正常乳腺组织中p16INK4a和RB基因启动子区域甲基化状况进行检测,并采用免疫组织化学SP法对p16INK4a蛋白表达情况进行相应检测.结果 乳腺癌、癌旁增生组织和正常乳腺组织中p16INK4a基因的甲基化率分别为23.9%(11/46)、18.2%(4/22)、1/7;RB基因的甲基化率分别为10.8%(5/46)、9.1%(2/22)、0(0/7);肿瘤组织、癌旁增生组织和正常乳腺组织中p16INK4a基因、RB基因甲基化率差异均无统计学意义(P>0.05).正常乳腺组织、癌旁增生组织、乳腺癌中p16INK4a蛋白表达阳性率分别为7/7、60.8%(28/46)和81.8%(18/22),三者之间差异无统计学意义(P>0.05);肿瘤组织中p16INK4a蛋白表达与肿瘤分级相关(P<0.05);肿瘤组织中p16INK4a甲基化状况与其蛋白表达、肿瘤分级、ER表达阴性具有相关性(P<0.05),与肿瘤大小、淋巴结转移、年龄均不相关;RB基因甲基化状态与肿瘤分级、肿瘤大小、ER表达及年龄均无相关性,但与淋巴结转移相关(P<0.05).结论 p16INK4a基因异常甲基化可能在乳腺癌发生过程中作用有限,但在肿瘤的演进中发挥作用;RB基因甲基化检测对于分析乳腺癌进展及预后情况可能有一定参考价值;p16INK4a基因甲基化是p16INK4a蛋白失表达的机制之一.     

乳腺癌中p16INK4a和视网膜母细胞瘤基因甲基化状况及其表达

目的 研究乳腺癌及癌旁增生组织中p16INK4a和视网膜母细胞瘤(RB)基因启动子区域的甲基化状况,并探讨基因异常甲基化与蛋白表达及其临床意义.方法 采用甲基化特异性PCR方法 对46例乳腺癌、22例癌旁增生组织及7例正常乳腺组织中p16INK4a和RB基因启动子区域甲基化状况进行检测,并采用免疫组织化学SP法对p16INK4a蛋白表达情况进行相应检测.结果 乳腺癌、癌旁增生组织和正常乳腺组织中p16INK4a基因的甲基化率分别为23.9%(11/46)、18.2%(4/22)、1/7;RB基因的甲基化率分别为10.8%(5/46)、9.1%(2/22)、0(0/7);肿瘤组织、癌旁增生组织和正常乳腺组织中p16INK4a基因、RB基因甲基化率差异均无统计学意义(P>0.05).正常乳腺组织、癌旁增生组织、乳腺癌中p16INK4a蛋白表达阳性率分别为7/7、60.8%(28/46)和81.8%(18/22),三者之间差异无统计学意义(P>0.05);肿瘤组织中p16INK4a蛋白表达与肿瘤分级相关(P<0.05);肿瘤组织中p16INK4a甲基化状况与其蛋白表达、肿瘤分级、ER表达阴性具有相关性(P<0.05),与肿瘤大小、淋巴结转移、年龄均不相关;RB基因甲基化状态与肿瘤分级、肿瘤大小、ER表达及年龄均无相关性,但与淋巴结转移相关(P<0.05).结论 p16INK4a基因异常甲基化可能在乳腺癌发生过程中作用有限,但在肿瘤的演进中发挥作用;RB基因甲基化检测对于分析乳腺癌进展及预后情况可能有一定参考价值;p16INK4a基因甲基化是p16INK4a蛋白失表达的机制之一.     

软组织平滑肌肉瘤中p16基因的甲基化检测

目的 探讨软组织平滑肌肉瘤（ＬＭＳ）中p16基因ＩＮＫ４Ａ的甲基化状态及其与p16表达的关系。方法 应用ＭＳＰ法检测３８例软组织平滑肌肉瘤,１０例平滑肌瘤及５例正常平滑肌组织中p16基因ＩＮＫ４Ａ的甲基化状态,用免疫组织化学ＳＰ方法检测p16蛋白表达情况。结果 ３８例ＬＭＳ中９例发生异常甲基化,异常甲基化率为２３.7%（９／３８）。其中,７例p16蛋白表达阴性,２例p16蛋白弱阳性,在p16蛋白表达阴性的ＬＭＳ中,异常甲基化率为５０％（７／１４）。结论 p16基因第一外显子启动子区５‘CpG岛的异常甲基化是导致p16基因失活、蛋白缺如的重要基因外机制,并可能参与肿瘤的发生。     

非小细胞肺癌p16基因异常与临床病理相关性研究

目的　探讨抑癌基因p16在非小细胞肺癌中的失活方式、mRNA和p16蛋白表达与临床病理因素的相关性。方法　应用对比性多重聚合酶链式反应检测 6 4例非小细胞肺癌中p16基因启动子的甲基化状况 ,同时应用原位杂交和免疫组织化学方法 [链霉素抗生物素蛋白 过氧化物酶 (SP)法 ]检测p16基因的mRNA和蛋白表达水平 ,并将上述结果与非小细胞肺癌之临床病理因素进行了相关性研究。结果　 5 6 3% (36 / 6 4 )的肺癌标本被检出有p16基因启动子甲基化 ,且甲基化与p16蛋白表达呈负相关 (P <0 0 5 ) ;免疫组织化学检测结果显示 ,5 7 8% (37/ 6 4 )的标本呈现p16蛋白表达缺失 ;原位杂交检测有 2 0 3% (13/ 6 4 )的标本被检出p16mRNA表达 ,且这 13例阳性者的p16蛋白也表达。同时具有p16基因启动子甲基化和蛋白表达缺失的非小细胞肺癌患者淋巴结转移率明显增高 ,术后生存期明显降低 (P <0 0 5 )。结论　启动子甲基化是导致非小细胞肺癌p16基因失活的主要方式 ,同时具有p16基因启动子甲基化及p16蛋白表达异常的患者预后不良     

肾细胞癌RASSF1A基因启动子区甲基化状况与表达水平研究

目的检测19例肾细胞癌患者癌组织及癌旁组织Ras相关区域家族蛋白1A（RASSFlA）基因启动子区甲基化情况并检测其mRNA表达水平，探索两者之间的联系。方法收集肾细胞癌患者癌组织及相应癌旁组织19份，分别提取其基因组DNA，以甲基化特异性PCR（Methylation special PCR，MSP）法检测RASSFlA基因启动子区甲基化情况。并以QPCR法检测了RASSFlA基因的mRNA表达水平。结果19例中有lO例肾细胞癌患者癌组织存在高甲基化，mRNA表达水平表达降低，二者之间存在显著负相关性（r=-0．8734，P〈0．01）。结论肾细胞癌中RASSFlA基因启动子区存在高甲基化，并抑制该基因的表达。     

Dact1基因在结直肠癌组织中的表达及其相关性研究

目的：观测Dact1基因在结直肠癌组织的表达及其启动子甲基化状态,并探讨它们之间的关系及在结直肠癌发生中的作用.方法：采用逆转录聚合酶链反应（RT-PCR）检测结直肠癌组织、癌旁组织各50例及正常对照组织20例Dact1基因mRNA的表达情况,甲基化特异性PCR（MSP）检测Dact1基因启动子甲基化状态.结果：结直肠癌组中,9例Dact1基因mRNA失表达（18%）,20例表达低于正常对照组（40%）;癌旁组织组中,1例Dact1基因mRNA失表达（2%）,3例表达低于正常对照组（6%）;正常对照组中,1例Dact1基因mRNA低表达（5%）.Dact1基因在癌组织、癌旁组织、正常对照组织中的甲基化阳性率分别为46%、12%、5%,癌组织组与癌旁组织组及正常对照组阳性率比较,差异均有统计学意义（P＜0.01）,而癌旁组织组和正常对照组阳性率比较,差异无统计学意义（P＞0.05）.Dact1基因mRNA的失表达（低表达）与其启动子甲基化状态的相关性分析有统计学意义（P＜0.05）.结论：Dact1基因mRNA的失表达（低表达）可能参与了结直肠癌的发生发展,其失表达可能与Dact1启动子区甲基化相关.     

Analysis of CDH1 gene expression in hereditary diffuse gastric cancer

目的 研究在遗传性弥漫型胃癌家系中是否存在上皮型钙黏素基因(CDH1)以及基因表达的异常.方法 收集符合遗传性弥漫型胃癌(HDGC)诊断标准的1个家系中15例成员的外周血和组织标本.用免疫组化和Westernblot法检测组织CDH1蛋白表达;提取基因组DNA,通过PCR扩增DNA直接测序检测CDH1基因16个外显子突变.用克隆测序法,鉴定CDH1基因启动子区CpG位点甲基化状况.结果 先证者和另一胃癌患者(家系2号成员)的癌旁胃黏膜上皮细胞CDH1蛋白表达较正常胃黏膜减弱,两者肿瘤组织的蛋白表达几乎为阴性.包括先证者在内的11例家系成员第14外显子mRNA水平2 377位点存在一个C→T的单核苷酸多态性(SNP),但未检测到16个外显子的胚系突变.相对于正常胃黏膜,先证者和家系2号成员的胃癌组织均有CDH1基因启动子的高甲基化,其瘤旁黏膜也有高甲基化.结论 此HDGC家系中,CDH1基因外显子胚系突变不是其致病原因,基因启动子区的甲基化可能是导致基因失活的原因之一.     

p16INK4a expression in basal-like breast carcinoma

BLBC represents a distinctive group of invasive breast carcinomas with specific genotype and immunopro-file. BLBC is usually defined by gene expression profiling and is currently associated with poor outcome. BLBCs are estrogen receptor (ER) negative, progesterone receptor (PgR) negative, HER2 negative, and usually show a variable expression of basal cytokeratins (CKs), EGFR and CD117. p16 ^INK4a is a tumor suppressor protein, encoded by the CDKN2A gene, which regulates cell cycle. The reported association of abnormalities in the p16/Rb pathway with increased risk of malignancy prompted us to determine the expression of p16^INK4a in a group of BLBC; the results were compared with a group of high-grade invasive carcinoma (HG-IC) of breast. Tissue microarrays (TMA) were constructed in triplicate including 18 BLBC and 18 HG-IC. All BLBC cases were ER-/PgR-/HER2-. Seventeen (94%) BLBC were CK 5/6+/CK 14+; 14 (78%) BLCB showed EGFR expression and 13 (72%) were CD117 positive. BLBCs showed a strong positive reaction with p16 ^INK4a antibody in 16 of 18 (89%) cases. Although the significance of p16 ^INK4a expression in breast cancer is not fully understood, we have shown that p16^INK4a is strongly expressed in breast cancers with basal-like phenotype. Since it is known that p16^INK4a is associated with aggressive behavior in human carcinomas, these data suggest that p16^INK4a play a role in the poor prognosis of BLBC.     

细胞衰老与p16INK4a的转录调控

抑癌基因p16~(INK4a)可特异地抑制CDK4及CDK6,在抑制细胞生长、促进细胞衰老等方面发挥重要的生物学作用。由于p16~(INK4a)功能的重要性,近年来,针对p16~(INK4a)转录调控方面的研究取得了一系列进展,发现了一系列正性和负性调控元件和转录调控因子,如:E47、Id1、Jun B、Bmi-1、RREB等,为进一步认识细胞增殖规律以及衰老进程具有重要的理论意义。     

Expression of p16INK4a in various cancer cells

The p16INK4a protein was detected by means of monoclonal antibodies to this protein in the cells of some carcinomas: that of the lungs (17 samples), urinary bladder (6 samples) and mammary gland (4 samples) as well as in the cells of three cell lines from of human uterine cervix carcinoma: SiHa (containing high risk HPV genome), C33A and HT3 (both HPV-negative but have RB mutations in RB gene). Lung carcinoma samples were very heterogenous by the part of cells expressing p16INK4a. High content of this protein was found in all 6 samples of transient cell urinary bladder carcinoma and in 1 sample of mammary gland ductal carcinoma. Cells of all three cell lines also contained p16INK4a. Thus, hyperexpression of this protein is not specific for only HPV-positive cancer of the uterine cervix. The protein presence in cancer cells seems to be an indicator of gene RB mutation or other disturbances of RB pathway.     

Expression of p16/INK4a in posttransplantation lymphoproliferative disorders

It was recently demonstrated that classification of posttransplantation lymphoproliferative disorders (PT-LPDs) into morphological and molecular categories is clinically relevant. It was also reported that PT-LPD not associated with Epstein-Barr virus (EBV) had a more aggressive course than most lesions associated with EBV. Because the cyclin-dependent kinase inhibitor p16/INK4a has been reported to be frequently inactivated in high-grade lymphomas, we evaluated 17 PT-LPD to determine whether p16/INK4a expression could be correlated to morphology, EBV detection, and a Ki-67 labeling index. We demonstrated that tumors with no p16/INK4a expression (n = 8) had a predominantly monomorphic appearance, and most were EBV negative (respectively, 7/8 and 5/8), whereas lesions with p16/INK4a expression (n = 9) were mostly polymorphic PT-LPD (6/9) (P = 0.049) and associated with EBV (9/9) (P = 0.015). In particular, strong p16/INK4a expression was observed in atypical immunoblasts and Reed-Sternberg-like cells. Furthermore, the proliferation index was significantly higher in tumors lacking p16/INK4a expression than in other lesions (P = 0.0008). In conclusion, down-regulation of p16/INK4a was mostly observed in PT-LPD lesions known to follow more aggressive courses: monomorphic tumors and EBV-negative PT-neoplasms. Conversely, overexpression of p16/INK4a was associated with EBV-positive PT-LPD. While p16/INK4a might play a role in the proliferative rate of LP-LPD, further investigations are needed to assess the clinical relevance of p16/INK4a expression in predicting the evolution of tumors and to explain how EBV could favor p16/INK4a protein accumulation in lesions.     

Role for p16(INK4a) in progression of gastrointestinal stromal tumors of the stomach: alteration of p16(INK4a) network members

Gastrointestinal stromal tumors feature a wide spectrum of biologic behavior, ranging from benign to extremely malignant. To determine the role of p16^INK4a alteration in progression of gastrointestinal stromal tumors of the stomach, we have investigated protein expression and gene methylation in correlation with clinicopathologic factors and survival. In addition to immunohistochemical analysis of p16^INK4a in a series of 95 cases, real-time quantitative methylation specific polymerase chain reaction for p16^INK4a and immunostaining for cyclin D1, cyclin E, pRb, DP-1, E2F-1, and Ki-67 were also evaluated in randomly selected samples. The p16^INK4a labeling indices ranged from 0% to 74% (median, 21%), demonstrating a significant inverse correlation with size (P = .046). On univariate (P = .003) and multivariate (P = .067) analyses, loss of p16^INK4a expression increased the likelihood of a poor tumor-related survival. In addition, size (P = .036) and the mitotic index (P = .005) had independent prognostic influence. The p16^INK4a methylation index, which ranged from 0% to 100% (median, 17%), was significantly higher in larger tumors (P < .001) and in high-risk category lesions (P = .001) and inversely correlated with protein expression. Hierarchical cluster analysis based on expression of p16^INK4a network members identified 2 clusters in 27 randomly selected tumor samples, containing 11 and 16 tumors each. Former cluster samples demonstrated higher risk category (P = .022), higher p16^INK4a methylation (P < .001), and more reduced pRb expression (P < .018). In addition, p16^INK4a network members clustered into 2 groups: (1) showing down-regulated p16^INK4a protein and up-regulating of both cyclin D1 and DP-1 and (2) down-regulated pRb and up-regulated E2F-1. We conclude that p16^INK4a alteration has an important role in progression of gastrointestinal stromal tumors of the stomach. Furthermore, the study provides a possible link between regulation of p16^INK4a network members and gastrointestinal stromal tumors.     

EB病毒感染和p16INK4a蛋白过表达与胃腺癌的关系

目的 探讨Epstein-Barr Virus(EBV)感染与p16异常表达在胃腺癌发生发展中的作用.方法 应用检测免疫组化法检测EB病毒潜伏感染膜蛋白-1(LMP-1)和p16蛋白在97份胃腺癌组织中表达.结果 97份胃腺癌组织中30例LMP-1蛋白表达阳性,阳性率为30.9%,EBV阳性率与患者性别、浸润深度、淋巴结转移、组织学分型和临床分期之间无明显关系(P>0.05);p16蛋白在胃腺癌组织中过度表达,阳性率为63.91%,p16过度表达与患者性别、肿瘤组织学类型、浸润深度不相关,而与淋巴结转移和临床分期相关;EBV感染与p16阳性表达之间无显著相关性(P>0.05).结论 ①EBV感染在胃腺癌的发生中起一定作用;②胃腺癌组织中p16蛋白过度表达是频发事件,p16是重要的预后指标之一;③EBV感染与p16异常表达在胃腺癌发生中是两个独立因素.     

p16INK4a expression in invasive vulvar squamous cell carcinoma.

p16, a member of the INK4a family of cyclin-dependent kinase inhibitors, is known as a negative regulator of cell cycle progression and differentiation. Although p16 has been shown to be a promising biomarker for the detection of cervical intraepithelial neoplasia, few data have been published on vulvar cancer. Using immunohistochemistry, we evaluated the expression of p16 in 80 cases of invasive vulvar squamous cell carcinoma. Results were correlated with clinicopathologic parameters and survival data to determine the prognostic significance of p16 in vulvar cancer. p16 expression was detected in 34 of 80 (43%) cases of invasive vulvar squamous cell carcinoma. The expression was localized to the cytoplasm and the nuclei of the tumor cells. Correlations between p16 expression status and any clinicopathologic variables failed to be of statistical significance. In a univariate analysis, groin lymph node status, tumor stage, and tumor grade were associated with disease-free and overall survival, respectively. Patients positive for p16 expression showed a significantly longer disease-free and overall survival by univariate analysis. p16 expression was not associated with survival in a multivariate Cox-regression model. Our data add on those published in the literature and suggest that p16 may be of prognostic significance in invasive vulvar squamous cell carcinoma.     

p16(INK4a) promoter methylation and 9p21 allelic loss in colorectal carcinomas: relation with immunohistochemical p16(INK4a) expression and with tumor budding

In colorectal carcinomas, p16(INK4a) inactivation is known to occur by allelic loss and by promoter methylation, but mutations are rare. p16(INK4a) is up-regulated in tumor buds, and the consequent shutdown of proliferation may be a prerequisite for tumor budding. Fifty-seven colorectal carcinomas from a consecutive series were investigated. Using DNA from tissue homogenates, p16(INK4a) promoter methylation was seen in 17 of 57 tumors by methylation-specific polymerase chain reaction, and this could be confirmed using DNA from laser-capture microdissected material in 16 of these cases. A total loss of immunohistochemical p16(INK4a) expression was seen in 6 of 17 tumors with promoter methylation. Quantification of immunohistochemical p16(INK4a) expression for the remaining 11 cases revealed statistically lower frequencies of expression as compared with cases without p16(INK4a) promoter methylation. 9p21 allelic loss was observed in 9 cases, but p16(INK4a) expression in these carcinomas was not reduced. Attempted linear regression of p16(INK4a) expression in tumor buds on the degree of tumor budding, as counted on pan-cytokeratin immunostains, did not show a correlation. p16(INK4a) promoter methylation can completely abrogate p16(INK4a) expression in colorectal carcinomas. In many cases, however, it has an appreciable but only modulatory influence on p16(INK4a) expression. Possibly, methylations are heterozygous, and/or mosaic in colorectal carcinomas and/or methylations are not totally stable but can be lost between carcinoma cell replication cycles. Up-regulation of p16(INK4a) does not seem to be a strict requirement for tumor budding, hence, the absence of a correlation.     

Expression of p14ARF, p15INK4b, p16INK4a, and DCR2 increases during prostate cancer progression.

Prostate carcinoma is a hormonally driven age-related neoplasm. Cellular senescence is an age-related process where cells remain metabolically active but in a growth-arrested state at the G1 phase. p14(ARF), p15(INK4b), and p16(INK4a), which are known to regulate G1 cell cycle arrest, and the tumor necrosis factor receptor superfamily member decoy receptor 2 (DCR2), have been recently identified as senescence markers. The purpose of this study was to characterize and compare the expression of p14(ARF), p15(INK4b), p16(INK4a), and DCR2 in tissue microarrays containing cases of normal prostate, nodular hyperplasia, prostate intraepithelial neoplasia (PIN), and malignant prostate cancer tissue. We performed immunohistochemical staining for p14(ARF), p15(INK4b), p16(INK4a), and DCR2 in tissue microarray blocks containing 41 cores of normal prostate, 65 cores of nodular hyperplasia, 21 cores of PIN, 69 cores of low-grade prostate carcinoma, and 42 cores of high-grade prostate carcinoma, derived from 80 cases of prostatectomy with adenocarcinomas. We detected positive staining of p16(INK4a) in 19% of the PIN, 25% of the low-grade carcinoma, and 43% of the high-grade carcinoma specimens but none in the normal prostate and nodular hyperplasia specimens. Expression of p14(ARF) revealed very high levels of expression in normal tissues (83%), nodular hyperplasia (88%), PIN (89%), and cancer cells (100%). P15(INK4b) and DCR2 were found positive in 81 and 33% normal, 46 and 10% nodular hyperplasia, 74 and 36% PIN tissues, 87 and 89% low-grade carcinomas, and 100 and 93% high-grade carcinomas. There is an increased protein expression of senescence-associated molecular markers, indicating that cellular senescence might play a role in prostate carcinoma. Because p16(INK4a)-positive cells were detected only in premalignant lesions and carcinomas but not in normal or benign tissues, p16(INK4a) may aid in the diagnosis of PIN and prostate cancer in difficult cases.