伏马菌素B1对人结肠腺癌细胞培养倍增时间的影响

 目的　观测伏马菌素B1(FB1)对培养细胞倍增时间的影响 ，探讨FB1诱发肿瘤的可能机理。方法　利用荧光分光光度法测定原位溶解 的人结肠腺癌培养细胞的DNA，以DNA总量的倍增作为培养细胞数目的倍增，通过比较对照组 和FB1处理组DNA倍增的时间，判断出FB1对该细胞株细胞倍增时间的影响。结果　对照组结肠腺癌细胞的倍增时间在39～42小时，FB1处理组细胞的倍增时间为34～36小 时。结论　伏马菌素B1可明显缩短人结肠腺癌细胞株的倍增时间。     

CA50-时间分辨荧光免疫分析试剂盒的制备与评价

目的研制并评价CA50-时间分辨荧光免疫分析(TRFIA)试剂盒。方法基于YRFIA技术,利用双抗体夹心法制备CA50-FRFIA试剂盒,并进行自制试剂盒的指标评价。检测415份健康人血清,确定CA50-TRFIA试剂盒检测血清CA50的正常值范围。结果CA50-TRFIA试剂盒的线性测量范围为5300 U/ml,灵敏性为0.2 U/ml,稳定性为4℃10个月,均优于CA50-放射免疫分析(RIA)试剂盒。与癌胚抗原(CEA)、CA12-5、CA15—3及甲胎蛋白(AFP)均无交叉反应发生,与CA19-9的交叉反应值为0.7 U/ml。批内变异系数(CV)均低于10%,批间CV低于15%,符合国家生物制品检定规程的规定。自制CA50-TRFIA试剂盒与CA50-RIA试剂盒的血清CA50检测结果显著相关(r= 0.901)。结论CASO-TRFIA试剂盒具有良好的灵敏性、特异性和准确性,适于临床应用。     

单剂量黄曲霉毒素B1致大鼠肝癌作用的短期实验模型

本文报告单剂量黄曲霉毒素Ｂ１（ＡＦＢ１）致大鼠肝癌作用短期实验模型的研究。６周龄、雄性Ｗｉｓｔａｒ大鼠，经腹腔一次性注射不同剂量（０、０．５０、０．７５、１．００和１．５０ｍｇ／ｋｇ体重）的ＡＦＢ１，作为启动剂，两周后，饲以含０．０１５％的２－乙酰氨基芴（２－ＡＡＦ）饲料４周，实验第三周末，施行肝大部分切除术（ＰＨ）。所有动物于实验第６周处死，取肝组织作Ｇａｍｍａ－谷氨酰转肽酶（ＧＧＴ）化学染色，     

乙肝病毒和黄曲霉毒素B1在树鼩肝癌形成中的协同作用

目的:动态观察乙肝病毒(HBV)和黄曲霉毒素B1(AFB1)在树鼩原发性肝细胞癌(HCC)形成过程中的作用.方法:成年树鼩按不同处理分为四组:A-HBV+AFB1组;B-HBV组;C-AFB1组;D-空白对照组.整个实验期间,各组所有动物定期抽血及肝活检.实验于160周结束,处死所有动物.血及肝组织标本进行HBV感染标志及常规病理组织学等检测.结果:第一例HCC于实验99周时出现于A组.A、C组的HCC发生率分别为66.7%和30.0%;HCC的平均出现时间在A、C组分别为120.3±16.6周和153.3±5.8周(P<0.01).B、D组于实验结束时均无一例HCC发生,但动态观察中见B组的肝细胞增生结节不仅发生较早而且较多,其中一例于实验130周死亡时已有直径大至0.5cm的增生结节形成.结论:HBV作为独立的致肝癌因素时作用较弱,但HBV与AFB1有很强的协同致肝癌作用;在HCC的形成过程中可能存在着"病毒-化学协同机制".     

广西黄曲霉毒素B1高污染区210人CYP3A7基因多态性检测

背景与目的:了解广西黄曲霉毒素B1(AFB1)高污染区人群细胞色素P450 3A7(CYP3A7)基因的多态性,及其基因型与肝细胞癌易感性之间的关系.材料与方法:选取黄曲霉毒素B1高污染区人群210例,其中肝细胞性肝癌患者97例,设为肝细胞性肝癌组(HCC组);HBV阳性而无其它疾病者38例,设为HBV阳性组;HBV阴性且无疾病者75例,设为HBV阴性组.取各组对象抗凝全血标本用酚-氯仿法提取DNA进行PCR扩增,并用限制性片段长度多态性检测CYP3A7*IA和CYP3A7*1C等位基因.结果:所检测的210份样本CYP3A7均为*1A/*1A型,未检测到*1C等位基因.结论:未检测到CYP3A7高表达*1C等位基因,推测CYP3A7在AFB1诱发的HCC发生中所起的作用小.     

黄曲霉毒素B1诱导的恶性转化肝细胞miRNA表达谱的变化

目的：检测黄曲霉毒素B1（aflatoxin B1,AFB1）诱导的恶性转化肝L02细胞（L02T）的miRNA表达谱,寻找差异表达的miRNA。方法：以含有AFB1的培养液多次间歇性染毒L02细胞获得转化细胞L02T,通过miRNA芯片技术检测和分析对照L02和转化L02T细胞的miRNA表达谱;用实时荧光定量PCR方法对芯片结果加以验证;采用TargetScan软件预测miRNA可能调控的靶基因。结果：获得2组细胞856个miRNA的表达谱,在25个表达差异显著的miRNA中,15个表达上调,10个表达下调;用定量RT-PCR对芯片结果中表达差异的miR-320a、miR-638和miR-98进行验证,并对其中上调显著的miR-638进行生物信息学分析,预测到4个与肝癌相关的潜在靶基因。结论：在AFB1诱导的恶性转化肝L02细胞中筛查出25个表达差异显著的miRNA,差异表达的miRNA可能在细胞恶性转化过程中起重要作用。     

体内相关代谢酶对黄曲霉毒素B1（AFB1）代谢影响的研究进展

黄曲酶毒素B1（AFB1）因其强有力的致肝毒性和遗传毒性被列为人类的致癌物，但它的致癌性与其在体内代谢形成“活性中间体”密切相关，由于这种“活性中间体”极不稳定，分子生物标记成为AFB1暴露评估的指标。近年来，分子生物学的进展，代谢酶基因遗传多态性对AFB1的致癌性发挥了重要的作用。     

广西乙肝病毒／黄曲霉毒素B1双暴露人肝细胞癌中PTENmRNA表达及突变的初步研究

目的探讨乙肝病毒／黄曲霉毒素B1双暴露相关肝细胞性肝癌（HCC）中PTEN基因的突变特点及其mRNA的表达水平。方法108例HCC来自广西不同地区样本,按照乙肝病毒与黄曲霉毒素的暴露情况,分为4个亚组：A组：HBV（＋）／AFB1-DNA（＋）,共48例;B组：HBV（＋）／AFB1-DNA（-）,共27例;C组：HBV（-）／AFB1-DNA（＋）,共19例;D组：HBV（-）／AFB1-DNA（-）,共14例。采用PCR联合基因直接测序法,检测108例肝癌组织中PTEN基因第4、5、8外显子的突变情况。同时采用RT—PCR法检测其基因mRNA的表达状况。结果（1）PTEN基因第4、5、8外显子测序结果未发现发生在外显子上的突变。但在第4外显子与第4内含子交界处有61例发生大片段的缺失,缺失率为56.4％。②PTEN缺失率在A、B、C、D组中分别为60．4％、62．9％、47．3％和46．6％,其差异在4个亚组间均无统计学意义（P〉0．05）。@PTENmRNA在4个亚组中的表达半定量灰度值分别为：A组：0．54±0．13;B组：0．59±0．16;C组：0．97±0．16;D组：0．92±0．13。其中,A、B组分别与C、D组相比,其差异均具有统计学意义（PAC=0．002,PAD=0．032,PBC=0．000,PBC=0．011）。结论在广西乙型肝炎病毒／黄曲霉毒素B1的双暴露肝细胞癌中,PTENmRNA的表达下调是一个常见的分子生物学事件,PTENmRNA表达下调可能主要与HBV感染有关。AFB1对PTENmRNA的表达下调可能有协同作用。     

银杏叶提取物对黄曲霉毒素B1所致大鼠肝癌相关蛋白表达影响的研究

目的:探讨银杏叶提取物(extract761 from Ginkgo giloba,EGb761)对黄曲霉毒素B1(aflatox B1,AFB1)致大鼠肝癌后相关蛋白表达的影响。方法:71只大鼠随机分为AFB1组(28只),AFB1+EGb761组(29只),空白对照组(14只)。第64周观察大鼠肝癌发生率,应用免疫组化法检测硫酸乙酰肝素类蛋白聚糖(MXR7)、环氧化酶(COX-2)以及细胞周期蛋白依赖性蛋白激酶抑制蛋白(p16)的表达情况。结果:AFB1组肝癌发生率明显高于AFB1+EGb761组(76%vs28%),χ2=10.602,P<0.05,对照组无肿瘤发生。AFB1+EGb761组MXR7蛋白含量明显低于AFB1组〔(1.488±1.178)vs(5.133±2.725)〕,F=18.638,P<0.001;AFB1+EGb761组p16蛋白含量明显高于AFB1组〔(2.456±1.014)vs(1.533±0.856)〕,F=24.091,P=0.03,AFB1组COX-2蛋白含量为3.305±0.566;AFB1+EGb761组为2.704±0.431,F=9.352,P=0.783。结论...     

黄曲霉毒素B1诱导性大鼠肝癌超微结构观察及DNA甲基化转移酶3表达变化

由DNA甲基化转移酶(DNA methyltransferase,DNMT)活性改变诱导的DNA甲基化模式改变是肿瘤异常表观遗传修饰的重要机制,主要表现为基因组整体的低甲基化和区域性高甲基化,通过改变癌基因、抑癌基因的表达和基因组的稳定性,诱导正常细胞癌性转变[1-2].DNMT3基因是DNMT家系重要成员,在建立组织特异性甲基化模式方面发挥关键作用.黄曲霉毒素B1(aflatoxin B1,AFB1)为公认的原发性肝癌(hepatocellular carcinoma,HCC)致癌因素之一,其致癌过程中同样涉及DNA甲基化模式异常改变[3-6].DNMT3在肝细胞癌变过程中动态变化的研究少见报道,本研究旨在分析AFB1诱导性大鼠肝细胞癌变不同阶段DNMT3a mRNA和DNMT3b mRNA变化特征,初步研究AFB1诱导性大鼠HCC发生的表观遗传学机制.     

Mitoinhibitory effect of fumonisin B1 on rat hepatocytes in primary culture

The inhibitory effect of fumonisin B₁ (FB₁) on epidermal growthfactor (EGF)-induced DNA synthesis in primary rat hepatocyteswas investigated by monitoring the incorporation of [³H]thymidinein the DNA. A pulse-labelling technique was adapted to determinethe incorporation of the radioactivity in the DNA (S-phase)quantitatively. FB₁ inhibits the EGF-induced DNA synthesis upto 90% when incorporated at concentrations of 150 to 300 µMfor a period of 44 h. A continued presence of FB₁ is requiredto exhibit this inhibition as (i) the subsequent removal ofFB₁ resulted in a reversal of the effect, (ii) a higher stimulatoryresponse in EGF-treated hepatocytes was found when the exposureperiod of hepatocytes to FB₁ was reduced, and (iii) pretreatmentof hepatocytes with FB₁ only slightly reduced (not significantly)DNA synthesis induced by EGF. Whilst the growth inhibitory effectof FB₁ was not associated with a cytotoxic effect, binding studiesusing [¹²⁵I]EGF indicated that the growth factor—receptorinteraction was not altered. No relationship was found betweenthe disruption of the sphingolipid biosynthesis by FB₁ and (i)the mitoinhibitory effect on the EGF response and (ii) the cytotoxicityof FB₁ in primary hepatocytes.     

Cancer initiation by fumonisin B(1) in rat liver--role of cell proliferation.

Fumonisin B(1) (FB(1)), a carcinogenic mycotoxin produced by the fungus Fusarium verticillioides in corn, causes cancer initiation in rat liver in a similar manner to genotoxic carcinogens although apparently with different kinetics. The present experiment was designed to evaluate the role of regenerative cell proliferation, effected by partial hepatectomy (PH) and carbontetrachloride (CCl(4)) and direct mitogen-induced hyperplasia, induced by lead nitrate (PbNO(3)), on FB(1)-induced cancer initiation. Initiation was effected over a period of 14 days by gavage administration of FB(1) at different daily doses ranging from 0.14 to 3.5 mg FB(1)/100 g body weight while the stimuli for cell proliferation were introduced 7 days after the start of the FB(1) treatment. Based on the proliferative stimulus used, cancer promotion was effected 3 weeks after completion of the initiating treatment by 2-acetylaminofluorene (2-AAF) treatment followed by PH or carbon tetrachloride CCl(4) on day 4. Cancer initiation by FB(1) was associated with a hepatotoxic effect and an increase in lipid peroxidation. In contrast to compensatory liver cell proliferation induced by PH and CCl(4), mitogen-induced hyperplasia (PbNO(3)) failed to enhance the cancer initiating potential of FB(1) suggesting that cancer induction by a non-genotoxic carcinogen is supported by regenerative cell proliferation. Cognizance of the enhancing role of cell proliferation during cancer initiation by FB(1) is required in assessing the risks posed by this mycotoxin to humans.     

The cancer-initiating potential of the fumonisin B mycotoxins.

The cancer-initiating potential of the fumonisin B (FB) mycotoxins produced by Fusarium moniliforme was screened in rat liver for their ability to induce rare hepatocytes with an acquired resistance to the mitoinhibitory effect of 2-acetyl-aminofluorene (2-AAF). Two different initiating protocols were used: a feeding regimen during which FB1 was fed at a dietary level of 0.1% for 26 days, and another where single or multiple doses of FB1 and FB2 (varying from 200 to 50 mg/kg) were administered (by gavage) to hepatectomized rats. In both cases promotion was effected by a 2-acetylamino-fluorene/carbontetrachloride treatment. Cancer initiation was only obtained after the prolonged feeding regimen, indicating that the fumonisins are poor cancer initiators. FB1 and FB2 also lack genotoxic effects in the in vivo and in vitro DNA repair assays in primary hepatocytes. Although FB1 primarily affects the liver, it is not very cytotoxic to primary hepatocytes when compared to aflatoxin B1.     

Toxicity and carcinogenicity of the Fusarium moniliforme metabolite, fumonisin B1, in rats.

A semi-purified corn-based diet containing 50 mg/kg of pure (not less than 90%) fumonisin B1 (FB1), isolated from culture material of Fusarium moniliforme strain MRC 826, was fed to a group of 25 rats over a period of 26 months. A control group of 25 rats received the same diet without FB1. Five rats from each group were killed at 6, 12, 20 and 26 months. The liver was the main target organ in the FB1-treated rats and the hepatic pathological changes were identical to those previously reported in rats fed culture material of F.moniliforme MRC 826. All FB1-treated rats that died or were killed from 18 months onwards suffered from a micro- and macronodular cirrhosis and had large expansile nodules of cholangiofibrosis at the hilus of the liver. Ten out of 15 FB1-treated rats (66%) that were killed and/or died between 18 and 26 months developed primary hepatocellular carcinoma. Metastases to the heart, lungs or kidneys were present in four of the rats with hepatocellular carcinoma. No neoplastic changes were observed in any of the control rats. Chronic interstitial nephritis was present in the kidneys of FB1-treated rats killed after 26 months. No lesions were observed in the esophagus, heart or forestomach of FB1-treated rats and this is contrary to previous findings when culture material of the fungus was fed to rats. It is concluded that FB1 is responsible for the hepatocarcinogenic and the hepatotoxic but not all the other toxic effects of culture material of F.moniliforme MRC 826 in rats.     

Association between tortilla consumption and human urinary fumonisin B1 levels in a Mexican population.

Fumonisins are mycotoxins produced by Fusarium spp. and commonly contaminate maize and maize products worldwide. Fumonisins are rodent carcinogens and have been associated with human esophageal cancer. However, the lack of a valid exposure biomarker has hindered both the assessment of human exposure and the evaluation of disease risk. A sensitive liquid chromatography-mass spectrometry method to measure urinary fumonisin B1 (FB1) following extraction on Oasis MAX cartridges was established and applied to urine samples from women in a cohort recruited in Morelos County, Mexico. Urinary FB1 was compared with dietary information on tortilla consumption. FB1 recovery in spiked samples averaged 94% as judged by deuterium-labeled FB1 internal standard. Urinary FB1 was determined in 75 samples from women selected based on low, medium, or high consumption of maize-based tortillas. The geometric mean (95% confidence interval) of urinary FB1 was 35.0 (18.8-65.2), 63.1 (36.8-108.2), and 147.4 (87.6-248.0) pg/mL and the frequency of samples above the detection limit (set at 20 pg FB1/mL urine) was 45%, 80%, and 96% for the low, medium, and high groups, respectively. Women with high intake had a 3-fold higher average FB1 levels compared with the "low intake" group (F = 7.3; P = 0.0015). Urinary FB1 was correlated with maize intake (P(trend) = 0.001); the correlation remained significant after adjusting for age, education, and place of residence. This study suggests that measurement of urinary FB1 is sufficiently sensitive for fumonisin exposure assessment in human populations and could be a valuable tool in investigating the associated health effects of exposure.     

The effects of dietary iron overload on fumonisin B1-induced cancer promotion in the rat liver

The present study was performed to determine whether excess hepatic iron modulates the cancer-initiating and promoting properties of FB1. Thirty-eight male F344 rats were divided into four dietary treatment groups: (i) control diet (AIN, n = 8); (ii) FB1 250 mg/kg diet (FB1, n = 10); (iii) 1-2% carbonyl iron (CI, n = 10); or (iv) FB1 plus iron loading (FB1/CI, n = 10) for 5 weeks (2 x 2 factorial design). Hepatic iron concentrations in iron-loaded animals at 5 weeks were 444 +/- 56 (CI) and 479 +/- 80 micromol/g dry weight (FB1/CI) (mean +/- SEM). All the FB1-fed rats, in the presence or absence of CI, developed a toxic hepatitis with a 4-fold rise in serum alanine transaminase (ALT) levels. FB1 appeared to augment iron-induced hepatic lipid peroxidation, as measured by the generation of thiobarbituric acid reacting substances (TBARS) in liver homogenates (P < 0.0001). Morphometric analysis showed that FB1 caused a significantly greater mean +/- SEM number of 'enzyme-altered' foci and nodules per cm2 (5.34 +/- 1.42 vs. 1.50 +/- 0.52, P < 0.05), as well as a greater area (%) of liver occupied by foci and nodules (0.33 +/- 0.12% vs. 0.05 +/- 0.03%, P < 0.001), compared with FB1/CI. The addition of FB1 to dietary iron loading caused a shift in distribution of iron from hepatocytes to Kupffer cells, probably due to phagocytosis of necrotic iron-loaded hepatocytes. In conclusion, (i) FB1 appears to cause toxicity in the liver independently from effects on lipid peroxidation; (ii) FB1 has a potentiating effect on iron-induced lipid peroxidation; and (iii) dietary iron loading appears to protect against the cancer promoting properties of FB1, possibly due to a stimulatory effect of iron on hepatocyte regeneration.     

肺癌诊断试剂盒的研制

目的 利用特异性与灵敏性较高的神经元特异烯醇化酶（NSE）、细胞角蛋白21-1片段（CYFRA21-1）肺癌相关标志物,研制肺癌双显色的体外联合诊断酶联免疫反应（ELISA）试剂盒。方法 将NSE、CYFRA21-1两种抗体按一定比例组合包被到酶标板的板底制成试剂盒。分别以NSE、CYFRA21-1抗原为研究对象,对包被液、包被时间、包被温度因素进行考察,以试剂盒的稳定性、灵敏度、准确性为指标进行结果 分析。结果 NSE、CYFRA21-1肺癌双显色ELISA诊断试剂盒4 ℃放置时有效期为6个月。试剂盒灵敏度为83.8%（129/154）,特异度为53.8%（57/106）,准确性为71.5%（186/260）,受试者工作特征曲线（ROC）曲线下面积Az为0.90,各项指标均较单独的NSE、CYFRA21-1明显提高。结论 成功制备双显色ELISA肺癌诊断试剂盒,该试剂盒可提高肺癌检查的准确性、灵敏度,降低假阳性率,具有开发为新型肺癌诊断试剂盒的条件。     

脑星形细胞肿瘤组织中内皮素-1的表达及定量分析

背景与目的:已有研究表明内皮素(endothelin-1,ET-1)可以在一些恶性肿瘤中合成、释放,并对肿瘤的发生、发展有重要的影响。本文研究ET-1在脑星形细胞瘤组织中的表达及含量与组织学分级的关系。方法:采用免疫组织化学S-P法及图像分析技术测定70例不同级别的星形细胞瘤组织中的ET-1表达的阳性率和含量。结果:ET-1普遍存在于星形细胞瘤,其阳性表达主要在胞浆内。Ⅳ级和Ⅲ级星形细胞瘤ET-1阳性率(86.67%和93.33%)与阳性细胞中的ET-1含量(0.1875±0.0227和0.1516±0.0134)都明显高于Ⅱ级(75.00%;0.1215±0.0116)和Ⅰ级星形细胞瘤(66.67%;0.1048±0.0143)及正常星形细胞(37.50%;0.0717±0.0074)(P<0.05,P<0.01)。分析表明:肿瘤分化程度越低,则ET-1的阳性率和含量越高,肿瘤分化程度越高,则ET-1的阳性率和含量越低。ET-1含量与肿瘤的分化程度呈正相关(r=0.863,P<0.01)。结论:ET-1可作为星形细胞瘤恶性生长的一个指标。     

A potential mechanism for fumonisin B(1)-mediated hepatocarcinogenesis: cyclin D1 stabilization associated with activation of Akt and inhibition of GSK-3beta activity

Fumonisin B(1) (FB(1)) is a worldwide corn contaminant and has been epidemiologically linked to the high incidence of human esophageal cancer in South Africa and China. FB(1) is hepatocarcinogenic in rats by an unknown mechanism. Inhibition of ceramide synthase and disruption of membrane phospholipids have been shown to be mechanisms of toxicity. Here we show overexpression of cyclin D1 protein in both preneoplastic and neoplastic liver specimens obtained from a long-term feeding study of FB(1) in rats. In rats fed FB(1) short-term, cyclin D1 protein levels in liver were increased up to five-fold in a dose-responsive manner. Northern blot analysis demonstrated no increase in mRNA levels of cyclin D1. 2D electrophoresis of cyclin D1 protein in FB(1)-treated samples showed a distinct pattern of migration (presence of less negatively charged form of the protein) that differed from controls. Recently, it has been shown that phosphorylation of cyclin D1 by glycogen synthase kinase 3beta (GSK-3beta) on a single threonine residue (Thr-286) positively regulates proteosomal degradation of cyclin D1. In FB(1)-treated samples we detected GSK-3beta phosphorylated on serine 9; activated protein kinase B (Akt) appears to be responsible for this activity-inhibiting phosphorylation. These findings suggest that overexpression of cyclin D1 results from stabilization due to a lack of phosphorylation mediated by GSK-3beta. We also observed an increase in cyclin dependent kinase 4 (Cdk4) complexes with cyclin D1 in FB(1)-treated samples; additionally, elevated Cdk4 activity was shown by increased phosphorylation of the retinoblastoma protein. In summary, the activation of Akt leads to increased survival, inhibition of GSK-3beta activity and post-translational stabilization of cyclin D1, all events responsible for disruption of the cell cycle G(1)/S restriction point in hepatocytes. This is the first report suggesting the mechanism by which FB(1) acts as a carcinogen.     

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.