细胞凋亡相关基因在食管上皮癌变中的表达及其意义

 目的　探讨食管上皮癌变过程中多个相关的细胞凋亡调控因子的表达状况及其意义。方法　应用碘化丙啶染色和间接免疫荧光标记方法,采用流式细胞术对60例食管癌组织及相应的癌旁组织进行定量检测。结果　bcl-2、c-FLIP基因蛋白在食管癌中的表达皆显著高于癌旁组织,两者比较差异有统计学意义（P＜0.01）;Fadd、Caspase-8和Caspase-3 蛋白在食管癌中的表达皆显著低于癌旁组织,两者比较差异有统计学意义（P＜0.01）。基因相关性比较结果显示,Fadd 与Caspase-8基因蛋白表达之间呈正相关关系（P＜0.01）,与正常黏膜组织和不典型增生组织相比,癌组织中DNA含量明显增高,异倍体细胞显著增加。结论　细胞凋亡的级联调控机制c-FLIP-Fadd-Caspase-8-Caspase-3-bcl-2在食管上皮癌变过程中起着重要作用。食管上皮癌变过程中,DNA含量及异倍体率增加。     

食管癌前细胞DNA含量及多基因表达的定量检测

目的 探讨食管癌高发区人群食管上皮癌变过程中的早期分子改变及早期癌变机理。方法 自食管癌高发区采集食管黏膜上皮细胞,碘化丙啶（propidium lodide,PI)染色进行DNA含量及倍体测定;对各基因蛋白进行间接免疫荧光标记,采用流式细胞仪（flow cytometry,FCM)进行定量检测。结果 DNA含量在癌形成时明显增高,二倍体细胞显著减少,而异倍体细胞明显增多,在癌细胞组异倍体率为84．2％;同时p53蛋白有明显积聚,而抑癌基因p16有明显缺失。在癌细胞组p53及cyclin D1蛋白表达的阳性率均为100％（5／5、6／6）。结论 在癌形成早期,DNA含量及异倍体率增加,癌基因cyclin D1表达增高,抑癌基因p16缺失及p53蛋白积聚。食管上皮癌形成时已有多个分子事件发生。     

Cyclin E、CDK2和p21WAF1在食管上皮癌变过程中的表达及意义

目的探讨食管上皮癌变过程中细胞周期调控因子cyclin E、CDK2和p21WAF1的表达状况及其意义.方法应用免疫组化SP法和原位杂交方法分别检测48例食管癌组织、31例非典型增生组织和17例正常食管粘膜中cyclin E、CDK2和p21WAF1蛋白及mRNA表达.应用半定量RT-PCR和Western blot检测22例新鲜食管癌及相应癌旁组织的mRNA和蛋白表达.结果从食管正常粘膜、非典型增生组织到癌组织,cyclin E和CDK2蛋白和mRNA阳性表达率逐渐上升,差异具有统计学意义(P＜0.01或P＜0.05).食管癌组织中cyclin E、CDK2和p21WAF1蛋白及mRNA高表达,与癌旁组织或切缘正常食管粘膜有显著性差异(P＜0.01).cyclin E、CDK2和p21WAF1基因表达显著正相关(P＜0.01或P＜0.05).结论食管上皮癌变过程中,细胞周期相关基因cyclin E和CDK2表达逐渐增强.cyclin E基因表达异常是食管癌变过程中的早期事件.p21WAF1基因在食管癌中高表达,可能与细胞周期调控的反馈机制有关.     

食管癌DNA含量和细胞周期分析的临床意义

目的：研究食管癌和癌旁组织DNA含量、细胞周期分布与临床分期及组织病理学分级的关系和意义。方法：应用流式细胞术（FCM）测定40例食管癌、癌旁组织、10例正常食管粘膜细胞的DNA指数（DI）、S期细胞百分率（SPF）、异倍体率。结果：癌灶中心组织DI、SPF、异倍体率明显高于癌旁组织；DI、SPF、异倍体率明显高于无淋巴结转移。结论：DNA含量、异倍体率与癌中心灶密切相关，SPF可作为组织病理学分级、临床分期的一个参数。DI、SPF、异倍体率与患的临床信息结合，将有助于食管癌患的诊断、治疗及预后评价。     

食管癌组织中p27蛋白表达与DNA含量的关系及其意义

目的探讨食管癌组织中p27蛋白表达与DNA含量、S期细胞比值(SPF)的关系及意义.方法应用免疫组化法检测食管癌及癌旁组织中p27蛋白的表达;应用流式细胞术检测其DNA含量(DI)和S期细胞比值(SPF).结果48例食管癌组织中仅有16例(33.33%)为p27蛋白高表达,而32例癌旁组织中25例为p27蛋白高表达(78.12%);食管癌组织DI和SPF的平均值分别为1.48±0.32和19.48%±12.35%,明显高于癌旁组织(分别为1.02±0.17和9.39%±5.75%),p27蛋白低表达组的DI和SPF均明显高于p27高表达组(分别为1.66±0.28和9.78%±6.12%;1.10±0.19和5.56%±5.18%).结论p27基因作为细胞负性调节因子,表达减少,DNA含量增加,推测与食管癌的发生、发展有关.     

食管上皮癌变过程中cyclin E和p21WAF1的表达及其意义

目的研究细胞周期调控因子cyclinE和p21^WAF1基因在食管上皮癌变过程中的表达及其意义。方法应用免疫组化S—P方法和原位杂交方法分别检测48例食管癌组织和相应癌旁组织(正常黏膜17例，非典型增生组织31例)中cyclinE和p21^WAF1蛋白及mRNA表达。结果从食管正常黏膜到非典型增生组织和癌组织，cyclinE蛋白和mRNA阳性表达率皆呈逐渐升高的趋势，食管癌组织和癌旁组织之间差异有显著性。高分化鳞癌中蛋白阳性表达率显著高于其它各组，mRNA阳性表达率显著高于正常黏膜和非典型增生Ⅰ级。p21^WAF1蛋白及mRNA在癌旁组织和癌组织中表达皆较高，两者差异无显著性。cyclinE和p21^WAF1基因表达无显著相关性。结论食管癌变过程中，细胞周期蛋白cyclinE表达水平增高，和组织分化程度显著相关，其异常是食管癌变过程中的早期事件，可能作为食管高分化鳞癌的诊断标志物之一。p21^WAF1基因在食管癌组织中高表达，可能与细胞周期调控的反馈机制有关。     

MDM2、P53和P27蛋白在食管鳞癌及其癌旁组织中的表达及其意义

背景与目的:探讨癌基因蛋白MDM2、抑癌基因蛋白P53以及细胞周期蛋白P27在食管鳞癌及其癌旁组织中的表达及其意义.材料与方法:采用免疫组织化学EnVision二步法(定性)检测85例食管癌存档蜡块及其癌旁黏膜中MDM2、P53和P27蛋白的表达;采用流式细胞仪(定量)检测上述3种蛋白在48例食管癌新鲜组织标本及其癌旁黏膜以及12例切缘相对正常黏膜中的表达.结果:从单纯性增生-轻度非典型增生-中度非典型增生-重度非典型增生-原位癌-浸润癌进展过程的变化,发现:定性和定量检测结果均显示P53蛋白在正常食管黏膜上皮中无表达,在食管癌变早期即出现P53蛋白的积聚;而MDM2、P27蛋白在正常黏膜上皮均有不同程度的表达,在癌变的晚期MDM2蛋白表达明显增加.结论:P53和P27蛋白表达的变化可能发生在食管癌形成早期,MDM2蛋白表达的变化可能发生在食管癌变的晚期.定性和定量2种方法联合检测能更客观和准确的探讨癌基因产物的表达及其临床意义.     

BRF2 基因在食管鳞状细胞癌组织中的表达及其临床意义

目的:检测TFIIB相关因子2(TFIIB-related factor 2,BRF2)基因在人食管鳞状细胞组织、癌旁组织及正常食管组织中的表达,分析BRF2在食管鳞状细胞癌发生、发展及预后中的意义。方法:选取2007年1月至2008年1月在山东大学齐鲁医院胸外科行手术治疗的食管鳞状细胞患者74例,应用RT-PCR和免疫组化方法检测食管鳞状细胞组织、癌旁组织和正常食管组织中BRF2 mRNA和蛋白表达水平。结果:食管鳞状细胞癌及其癌旁组织中BRF2 mRNA表达水平明显高于正常食管组织。食管鳞状细胞组织、癌旁组织和正常食管组织中BRF2蛋白表达阳性率分别为54.5%、32.5%和7.5%,癌组织、癌旁组织中BRF2蛋白的阳性率均显著高于正常食管组织(P<0.05)。随着食管鳞状细胞分化程度升高,BRF2蛋白阳性率显著下降,Ⅲ期和Ⅳ期食管鳞状细胞组织中BRF2蛋白阳性率明显高于Ⅰ期和Ⅱ期(72.7%,73.3%vs 35.7%,34.8%,P<0.05),且生存3年以下的食管鳞状细胞癌患者BRF2表达明显高于3年以上者(69.2%vs 38.2%,P<0.05),吸烟患者预后BRF2蛋白阳性率明显高于非吸烟患者(61.1%vs 30.4%,P<0.05)。结论:食管鳞状细胞癌组织高表达BRF2蛋白,BRF2 mRNA和蛋白与患者不良预后相关,可能作为食管鳞状细胞预后判断的参考指标之一。     

食管、贲门

ET-1及其受体ETAR在食管癌中的表达及意义；自杀基因联合放射对食管癌细胞株的实验研究；胸苷酸合成酶基因多肽性及其蛋白表达与食管鳞状细胞癌淋巴结转移的关系；食管癌术后锁骨上野放疗与食管气管沟淋巴结转移关系的探讨；食管上皮癌变过程中DNA含量及细胞周期调控因子表达的定量检测；综合影像学检查对中晚期食管癌分期的意义；     

组蛋白去乙酰化酶在食管鳞癌中的表达及其表达下调对EC9706细胞生物特性的影响

目的:探讨组蛋白去乙酰化酶(histone deacetylase2,HDAC2)在食管鳞癌组织中的表达,并研究其表达下调对食管鳞癌EC9706细胞增殖、细胞周期和细胞凋亡的影响,以及分析其相关的分子机制。方法:采用免疫组织化学法检测食管鳞癌组织中HDAC2蛋白的表达。将特异性针对HDAC2基因的小分子干扰RNA(small interfering RNA,siRNA)和对照siRNA分别转染食管鳞癌EC9706细胞,实验分3组:未处理组、对照siRNA组和HDAC2siRNA组。蛋白质印迹法检测各组EC9706细胞中HDAC2蛋白的表达。CCK-8计数法检测转染前后细胞的增殖情况。FCM法检测细胞周期和细胞凋亡的变化。蛋白质印迹法检测与细胞增殖、细胞周期和细胞凋亡相关蛋白的表达变化。结果:HDAC2蛋白在食管鳞癌组织中表达的阳性率为79.71%,显著高于癌旁不典型增生组织的51.11%和正常食管黏膜组织的23.19%,3者之间差异具有统计学意义(χ2=44.121,P=0.000);此外,HDAC2蛋白表达与患者的年龄和性别无关(P均>0.05),但是与组织学分级、浸润深度、TNM分期和淋巴结转移均显著相关(P均<0.05)。HDAC2siRNA能有效下调食管鳞癌EC9706细胞中HDAC2蛋白的表达,明显抑制食管鳞癌EC9706细胞的增殖,促使细胞周期静止在G0/G1期,并诱导细胞凋亡。蛋白质印迹法检测结果显示,HDAC2表达下调能明显提高p21和凋亡相关蛋白bax的表达量,同时降低细胞周期蛋白cyclin D1和bcl-2的表达量。结论:HDAC2可能在食管鳞癌的发生、发展中具有重要作用,其表达下调介导的食管鳞癌细胞增殖抑制、细胞周期静止以及细胞凋亡可能与p21、bax的表达升高和cyclin D1、bcl-2表达降低密切相关。     

香加皮杠柳苷对MCF-7细胞周期及p21WAF1/CIP1表达的影响

 目的：研究香加皮杠柳苷（CPP）对人乳腺癌MCF-7细胞周期及p21^WAF1/CIP1表达的影响 ,探讨其抗肿瘤作用及作用机制。方法：采用MTT法检测不同浓度CPP（1.25、2.50、5.00、 10.00、20.00 ng/ml）作用不同时间（24、48、72 h）对MCF-7细胞的增殖抑制作用;应用流 式细胞术分析不同浓度CPP （2.50、5.00、10.00 ng/ml）分别作用于MCF-7细胞6、12、24、 48、72 h对肿瘤细胞周期的影响;并采用RT-PCR和免疫细胞化学技术检测细胞周期相关因子 p21^WAF1/CIP1的表达。结果：CPP能明显抑制MCF-7细胞的增殖,并呈浓度及时间依赖性,作用 于MCF-7细胞48 h的IC₅₀为（4.88±0.16）ng/ml。流式细胞术结果显示,CPP作用MCF-7细胞24 h时,G₀/G₁期细胞明显增多,而S期和G₂/M期细胞显著减少,与对照组相比差异有统计学意义 （P<0.05）,其中5.00 ng/ml组G₀/G₁期细胞由对照组的（49.33±3.25）%升高至（79.47± 2.40）%,S期和G₂/M期细胞由对照组的（28.47±1.59）%和（22.20±2.09）%分别下降至（10.13±3.26）%和（10.40±1.41）%。经CPP处理的MCF-7细胞中p21^WAF1/CIP1 mRNA的表达明显增强,p21^WAF1/CIP1/β-actin光吸度比值与对照组相比明显增高（P<0.05）。免疫细胞化学结果显示,CPP组MCF-7细胞中p21^WAF1/CIP1 蛋白的表达随作用浓度的增加而增强,其中10.00 ng/ml组肿瘤细胞p21^WAF1/CIP1的表达呈强阳性。结论：香加皮杠柳苷（CPP）具有显著的体外抗肿瘤作用,且有效剂量很小,其IC₅₀仅为（4.88±0.16）ng/ml。CPP可使MCF-7细胞发生G₀/G₁期阻滞,并可使细胞周期相关基因p21^WAF1/CIP1的mRNA及蛋白表达增强,提示阻滞细胞周期可能是CPP体外抗肿瘤的作用机制之一。     

Unusual deregulation of cell cycle components in early and frank estrogen-induced renal neoplasias in the Syrian hamster

There is strong evidence that estrogens are involved in theetiology, promotion and progression of a variety of cancers,including the cancers of the breast and endometrium. The Syrianhamster estrogen-induced, estrogen-dependent renal neoplasmis a well-established animal model used to elucidate the cellularand molecular mechanisms involved in solely estrogen-inducedcarcinogenic processes. G₁ cell cycle progression was studiedin estrogen-induced early renal tumor foci and in large kidneytumors of castrated male hamsters. Levels of cyclin D1, cyclinE and retinoblastoma (pRb) proteins were higher in these renalneoplasias than in adjacent uninvolved renal tissue and kidneysfrom untreated, age-matched animals. Of particular interestis the presence of a predominant 35 kDa cyclin E protein variantform in primary renal tumors. In addition, amounts of the phosphorylatedforms of cyclin-dependent kinases (cdk) 2 and 4 were decreased,and both RNA and protein levels of p27^kip1 (p27), a cyclin-dependentkinase inhibitor, were markedly higher in early and frank renaltumors than in adjacent uninvolved renal tissue and kidneysof untreated, age-matched animals. These changes in cell cyclecomponents coincided with a rise in renal tumor cell proliferation.Binding of the elevated p27 protein to cyclin E, cdk2 and cdk4,however, was not impaired, suggesting that this cell cycle suppressorprotein is functional. In addition, cyclin D1-, cdk2-, cdk4-and cyclin E-associated kinase activities were also lower inthese estrogen-induced renal neoplasms than in untreated, age-matchedkidneys. Interestingly, when compared with untreated kidneytissue, early and frank renal neoplasms had less of the 62 kDanative form of E2F1 and contained a 57 kDa variant form. Thuswe have characterized an unusual deregulation of the cell cycleduring estrogen-induced renal tumorigenesis in Syrian hamsterswhich still allows for estrogen-driven kidney tumor cell proliferationand may contribute to the early genomic instability found.     

Cell cycle-dependent modulation of O6-methylguanine-DNA methyltransferse in C3H/10T1/2 cells

O⁶-methylguanine-DNA methyltransferase (MGMT) was measured inpartially synchronized cultures of C3H/10T1/2 mouse embryo cellsas a function of cell cycle. The degree of synchrony and progressionof the cell cycle were monitored by flow cytometry. The MGMTlevel was significantly reduced prior to the onset of S-phase.This reduction was concomitant with the inhibition of in vivorepair of O⁶-methylguanine in DNA of S-phase cells as observedearlier. The recovery of the MGMT level paralleled the progressionof synchronized cells into G₂. S-phase cells purified by cellsorting contained -15% of the MGMT present in G_o or early G₁cells. A comparison of the in vivo repair of O⁶-methylguanineand MGMT levels suggests that the lack of repair of O⁶-methylguaninein DNA of the mouse embryo cells is due only in part to a temporalloss of MGMT.     

The chemopreventive flavonoid apigenin induces G2/M arrest in keratinocytes

Apigenin is a plant flavonoid which has been shown to significantlyinhibit UV-induced mouse skin tumorigenesis when applied topically,and may represent an alternative sunscreen agent in humans.We have investigated the molecular mechanism(s) by which apigenininhibits skin tumorigenesis. Initial studies examined the effectsof apigenin on the cell cycle. DNA flow cytometric analysisindicated that culturing cells for 24 h in medium containingapigenin induced a G₂/M arrest in two mouse skin derived celllines, C50 and 308, as well as in human HL-60 cells. The G₂/Marrest was fully reversible after an additional 24 h in mediumwithout apigenin. We investigated the effects of apigenin oncyclin B1 and p34^cdc2, since cyclin B1/p34^cdc2 complexes regulateG₂/M progression. Western blot and immune complex kinase assaysusing whole cell lysates from 308 and C50 cells treated for24 h with 0–70 µM doses of apigenin demonstratedthat apigenin treatment did not change the steady-state levelof p34^cdc2 protein, but did inhibit p34^cdc2 H1 kinase activityin 308 cells. Western blot analysis showed that apigenin treatmentof C50 cells and 308 cells inhibited the accumulation of cyclinB1 protein in a dose-dependent manner. The apigenin levels detectedin cultured keratinocytes were relevant to those detected inepidermal cells of Sencar mice treated with tumor inhibitorydoses of apigenin. In conclusion, we present evidence that apigenininduces a reversible G₂/M arrest in cultured keratinocytes,the mechanism of which is in part due to inhibition of the mitotickinase activity of p34^cdc2, and perturbation of cyclin B1 levels.     

乳腺浸润性导管癌中cyclinD1 、p57 KIP2的表达及意义

 目的 研究cyclinD1、p57^KIP2在乳腺浸润性导管癌（IDC）中的表达及意义。方法 采用免疫组织化学SP法检测64例113（2、15例乳腺导管内癌（DCIS）和15例癌旁正常乳腺组织中cyclinD1、p57 ^KIP2的表达。结果 cyclinD1、p57 ^KIP2阳性表达率在IDC与在乳腺不同组织之间、腋窝淋巴结有无转移之间差异均有显著性（P≤0．05，P〈0．01）；cyclinD1阳性表达率与IDC组织学分级有关（P〈0．01）；cyclinD1与p57 ^KIP2之间阳性表达率呈负相关（P〈0．01）。结论 cyclinD1与p57 ^KIP2共同参与了乳腺癌的发生发展过程。cyclinD1异常表达是乳腺癌发生的早期事件。联合检测cyclinD1及p57 ^KIP2对预测乳腺癌淋巴结转移有重要意义。     

食管鳞癌中VEGF165b、HIF-1α的表达及临床意义

目的检测食管鳞癌组织中VEGF_165b和HIF-1α的表达及与临床病理特征的关系。方法应用免疫组织化学SP法检测143例食管鳞状细胞癌组织中VEGF_165b和HIF-1α的表达。结果VEGF_165b和HIF-1α在食管鳞癌组织中的阳性表达率分别为13.3%和43.4%;VEGF_165b阳性表达率与HIF-1α阳性表达率呈负相关关系（P=0.035）。HIF-1α阳性表达率与饮酒程度、分期、纵隔淋巴结转移及肿瘤的分化程度呈正相关（P＜0.05）。结论VEGF_165b和HIF-1α在食管癌的发生发展和淋巴转移中起重要的作用,VEGF_165b的表达与HIF-1α存在相关性,饮酒是食管癌的重要危险因素。VEGF_165b可能成为治疗的靶点。     

Apoptotic and anti-proliferative effects of fumonisin B1 in human keratinocytes, fibroblasts, esophageal epithelial cells and hepatoma cells

Fumonisin B₁ is associated with various animal and human carcinomasand toxicoses, including leukoencelphalomalacia, hepatocarcinoma,pulmonary edema and esophageal carcinoma. We have examined thecellular effects of fumonisin B₁ in vitro using cellular modelsystems relevant to potential human target tissues. Althoughfumonisin B₁ has been described as a mitogen in Swiss 3T3 cellsbased on stimulation of [³H]thymidine incorporation, in thecurrent work it was found that fumonisin B₁ inhibited incorporationof [³H]thymidine by cultured neonatal human keratinocytes andHepG2 human hepatocarcinoma cells at 10^–7 and 10^–4M respectively. Fumonisin B₁ also inhibited clonal expansionof normal human keratinocytes and HET-1A human esophageal epithelialcells at 10^–5 M and growth in mass culture of normal humanfibroblasts at 10^–7 M. The clonogenicity of normal humankeratinocytes decreased to 45.5% of controls afterexposure to10^–4 M fumonisin B₁ for 2 days. However, no differencesin the cell cycle distribution of cultured keratinocytes wasnoted after exposure to 10^–5 M fumonisin B₁ for 40 h.Theviability of normal human keratinocytes and HET-1A cellsdecreased as a result of fumonisin B₁ treatment, as determinedby a fluorescein diacetate/propidium iodide flow cytometriccell viability assay. Fumonisin B₁-treated keratinocytes releasednucleosomal DNA fragments into the medium 2–3 days afterexposure to 10^–4 M fumonisin B₁ and increased DNA strandbreaks were detected in attached keratinocytes exposed to 0–10^–4M fumonisin B₁ using a terminal deoxy-nucleotidyl transferase-basedimmunochemical assay system. Furthermore, fumonisin B₁-treatedkeratinocytes and HET-1A cells developed morphological featuresconsistent with apoptosis, as determined by phase contrast microscopy,fluorescent microscopy of acridine orange stained cells andelectron microscopy. These results are consistent with the occurrenceof fumonisin B₁-mediated apoptosis in vitro.     

Induction of p21/WAF1 and G1 cell-cycle arrest by the chemopreventive agent apigenin

Apigenin is a plant flavonoid that has been shown to significantly inhibit ultraviolet-induced mouse skin tumorigenesis when applied topically and may be an alternative sunscreen agent for humans. A long-term goal of our laboratory is to elucidate the molecular mechanism or mechanisms by which apigenin inhibits skin tumorigenesis. In a previous publication, we characterized the mechanism by which apigenin induced G₂/M arrest in keratinocytes. More recent studies in our laboratory have provided evidence that apigenin can induce G₁ arrest in addition to arresting cells at G₂/M. Here we describe the mechanism of the apigenin-induced G₁ arrest in human diploid fibroblasts (HDF). Treatment of asynchronous HDF for 24 h with 10–50 μM apigenin resulted in dose-dependent cell-cycle arrest at both the G₀/G₁ and G₂/M phases as measured by flow cytometry. The G₀/G₁ arrest was more clearly defined by using HDF that were synchronized in G₀ and then released from quiescence by replating at subconfluent densities in medium containing 10–70 μM apigenin. The cells were analyzed for cell-cycle progression or cyclin D1 expression 24 h later. A dose of apigenin as low as 10 μM reduced the percentage of cells in S phase by 20% compared with control cultures treated with solvent alone. Western blot analysis of apigenin-treated HDF indicated that cyclin D1 was expressed at higher levels than in untreated cells, which signifies that they were arrested in G₁ phase rather than in a G₀ quiescent state. The G₁ arrest was further studied by cyclin-dependent kinase 2 (cdk2) immune complex–kinase assays of apigenin-treated asynchronous HDF, which demonstrated a dose-dependent inhibition of cdk2 by apigenin. Inhibition of cdk2 kiase activity in apigenin-treated cells was associated with the accumulation of the hypophosphorylated form of the retinoblastoma (Rb) protein as measured by western blot analysis. The cdk inhibitor p21/WAF1 was also induced in a dose-dependent manner, with a 22-fold induction of p21/WAF1 in 70 μM apigenin-treated cells. In conclusion, apigenin treatment produced a G₁ cell-cycle arrest by inhibiting cdk2 kinase activity and the phosphorylation of Rb and inducing the cdk inhibitor p21/WAF1, all of which may mediate its chemopreventive activities in vivo. To our knowledge this is the first report of a chemopreventive agent inducing p21/WAF1, a known downstream effector of the p53 tumor suppressor protein. Mol. Carcinog. 19:74–82, 1997. © 1997 Wiley-Liss, Inc.