吲哚美辛对结肠癌细胞CDK2、CDK4、P21WAF1/CIP1、Bcl-2及Bax蛋白表达的影响

目的：非甾体类抗类药通过环氧合酶途径是抑制肿瘤的机制之一，是否还有其他途径抑制细胞增殖及诱导凋亡。探讨吲哚美辛抗肿瘤的作用机制。为其临床应用实验依据。方法：不同浓度的吲哚美辛作用于结肠癌细胞株HCT116细胞24h，通过Western蛋白印迹技术检测CDK2、CDK4、p21s^WAF1/CIP1、Bcl-2及Bax蛋白表达。结果：吲哚美辛降低细胞周期素依赖蛋白激酶CDK2、CDK4及抗凋亡蛋白Bcl-2的表达上，上调细胞周期依赖蛋白激酶抑制剂p21s^WAF1/CIP1蛋白，而对促凋亡蛋白Bax的表达无影响。结论：吲哚美辛通过降低CDK2、CDK4、Bcl-2蛋白，上调p21s^WAF1/CIP1的表达来抑制细胞增殖和诱导细胞凋亡。     

Effects of tachyplesin on the regulation of cell cycle in human hepatocarcinoma SMMC-7721 cells

AIM: To investigate the effects of tachyplesin on the cell cycle regulation in human hepatcarcinoma cells. METHODS: Effects of tachyplesin on the cell cycle in human hepatocarcinoma SMMC-7721 cells were assayed with flow cytometry. The protein levels of p53, p16, cyclin D1 and CDK4 were assayed by immunocytochemistry. The mRNA levels of p21(WAF1/CIP1) and c-myc genes were examined with in situ hybridization assay. RESULTS: After tachyplesin treatment, the cell cycle arrested at G0/G1 phase, the protein levels of mutant p53, cyclin D1 and CDK4 and the mRNA level of c-myc gene were decreased, whereas the levels of p16 protein and p21(WAF1/CIP1) mRNA increased. CONCLUSION: Tachyplesin might arrest the cell at G0/G1 phase by upregulating the levels of p16 protein and p21(WAF1/CIP1) mRNA and downregulating the levels of mutant p53, cyclin D1 and CDK4 proteins and c-myc mRNA, and induce the differentiation of human hepatocacinoma cells.     

Synergistic antitumor effect of TRAIL and doxorubicin on colon cancer cell line SW480

AIM: TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) has been reported to specifically induce apoptosis of cancer cells although only a small percentage of cell lines were sensitive to it. Cell lines not responding to TRAIL in vitro were said to be more prone to apoptosis when TRAIL was combined with another anticancer agent.Generally, factors affecting drug-sensitivity involve many apoptosis-related proteins, including p53. The expression of wild-type p53 gene was proposed as an important premise for tumor cells responding to chemotherapy. The present study was to investigate the cell killing action of TRAIL on colon cancer cell line SW480, its synergistic effect with doxorubicin, and the possible mechanisms.METHODS: SW480 cells were cultured in the regular condition and incubated with different levels of agents.Morphologic changes in these cells after treatment were observed under phase-contrast microscope and cytotoxicity by TRAIL alone and in combination with doxorubicin was quantified by a 1-day microculture tetrazolium dye (MTT) assay. In addition, flow cytometry assay (FCM) and transmission electron microscopy were used to detect apoptosis among these cells. Variation of p53 protein level among different groups according to concentrations of agents was measured by Western blot assay.RESULTS: (1) SW480 cells were not sensitive to TRAIL,with IC50>l mg·L^1 and dose-independent cytotoxicity. (2)SW480 cells were sensitive to doxorubicin at a certain degree,with dose-dependent cytotoxicity and IC50=65.25±3.48μmol·L^-1. (3) TRAIL could synergize with doxorubicin to kill SW480 cells effectively, which was represented by the boosted killing effect of doxorubicin on theses cells. IC50 of doxorubicin against SW480 cells sharply reduced when it was combined with TRAIL. (4) Subtoxic TRAIL (100 μg·L^-1),combined with subtoxic doxorubicin (0.86 μmol·L^-1), could kill SW480 cells sufficiently. Cytotoxicity by MTT assay arrived at 80.12±2.67 %, which was significantly higher than that by TRAIL or doxorubicin alone, with P=0.006 and 0.003 respectively. This killing effect was partly due to apoptosis. It was proved by large amounts of apoptotic cells under phase-contrast microscopy, cell apoptosis rate of 76.82±1.93 % by FCM assay and typical apoptotic morphology observed through transmission electron microscopy. Increase of apoptosis after combined treatment had no relation with protein level of p53 (p>0.05).CONCLUSION: SW480 cells are not sensitive to TRAIL, but TRAIL can synergize with lower concentra~on of doxorubidn to induce apoptosis effectively. The status of p53 protein is not involved in the mechanism of synergistic apoptosis. It suggests the potential therapeutic applicability of the combination of TRAIL with doxorubidn against colon cancers.     

肝胆管癌丙型肝炎病毒感染与p53和p21WAFD/CIP1异常表达的关系

为探讨丙型肝炎病毒（ＨＣＶ）感染与Ｐ５３和Ｐ２１ＴＷＡＦ－／ＣＩＰ１基因的关系。采用 化技术对２９例原发性肝胆管癌中ＨＣＶ抗原（ＮＳ５－Ａｇ）、ｐ５３和ｐ２１＾ＷＡＦＩ＝／ＣＩＰ１蛋白表达进行研究。结果：２９例胆管癌中ＮＳ５－Ａｇ、ｐ５３及Ｐ２１ＴＷＡＦＩ／ＣＩＰＩ蛋白表达进行研究。结果：２９例胆管癌中ＮＳ５－Ａｇ、Ｐ５３display structure     

p21<Superscript>WAF1/CIP1</Superscript> is more effective than p53 in growth suppression of mouse renal carcinoma cell line Renca in vitro and in vivo

Purpose Although there are many controversial reports about the effect of p53 and p21^WAF1/CIP1 overexpression in different human tumor cells, the p53 gene is shown to be a more effective candidate for cancer gene therapy because of its more pronounced ability to induce apoptosis. In the present study, we present the effect of p53 and p21^WAF1/CIP1 overexpression on mouse renal carcinoma cells in vitro and in vivo.Methods p53 and p21^WAF1/CIP1 genes were introduced into Renca cells using adenoviral vectors (Ad5CMV-p53 and Ad5CMV-p21). The induction of apoptosis was measured using Annexin V assay and DNA fragmentation analysis. The expression of proteins was examined using immunocytochemistry and Western blot methods. The ability of adenoviral vectors to inhibit tumorigenicity of Renca cells, as well as the growth of pre-established tumors was measured.Results In vitro growth assays revealed higher growth suppression after Ad5CMV-p21 infection. Although both vectors induced apoptosis, Ad5CMV-p53 was slightly more efficient. In vivo studies in Balb/c mice, demonstrated that tumorigenicity was completely suppressed by Ad5CMV-p21. Besides this, Ad5CMV-p21 significantly inhibited the growth of established tumors, while Ad5CMV-p53 did not.Conclusions These data suggest that p21^WAF1/CIP1 is a more potent growth suppressor than p53 of mouse tumor cells Renca. The divergent responses of tumor cells to p21^WAF1/CIP1 overexpression could be due to various networks that differ between species.     

丙戊酸钠对肝癌SMMC-7721细胞增殖和细胞周期的影响及机制

目的:探讨丙戊酸钠(VPA)对人肝癌SMMC-7721细胞增殖、细胞周期及对p21WAF1/CIP1mRNA表达的影响.方法:实验分为空白对照组、PBS组、VPA0.2mmol/L组、VPA1.0mmol/L组和VPA5.0mmol/L组.不同浓度VPA干预人肝癌SMMC-7721细胞24h、48h和72h,采用MTT法检测细胞存活率,流式细胞仪检测细胞周期;干预72h后,用Real-timePCR法检测VPA干预72h后p21WAF1/CIP1mRNA的表达情况.结果:与空白对照组及PBS组比较,不同浓度的VPA作用24h,48h及72h时组肝癌SMMC-7721细胞增殖均出现了不同程度抑制(请将具体数据列出来P<0.05),随着VPA药物浓度升高,细胞增殖抑制作用逐渐增强,随作用时间延长,抑制程度逐渐增强(P<0.05).随药物浓度升高,G1期细胞比例逐渐增多,S期细胞比例逐渐减少,细胞发生G0/G1期阻滞.VPA干预肝癌SMMC-7721细胞72h后,VPA组p21WAF/CIP1mRNA表达较空白对照组及PBS组表达明显升高(请将具体数据列出来P<0.01).结论:VPA可抑制人肝癌SMMC-7721细胞的增殖,且呈时间及剂量依赖性,并诱导出现G0/G1细胞周期阻滞,同时上调p21WAF1/CIP1mRNA的表达.     

Status of p53 phosphorylation and function in sensitive and resistant human cancer models exposed to platinum-based DNA damaging agents

Purpose Resistance to chemotherapeutic drugs is a hallmark of many human cancers, which can occur independent of p53 gene status; however, the presence of wild-type p53 in chemorefractory tumors confers greater resistance to cisplatin, but such tumors do not display complete cross-resistance to the platinum analog (1R,2R-diaminocyclohexane)(trans-diacetato)(dichloro)platinum^IV (DACH-Ac-Pt). In this article we examine DNA damage-induced phosphorylation of p53 and downstream p53-dependent transactivation events in cisplatin-sensitive and cisplatin-resistant human cancer cell lines possessing wild-type p53.Methods Western-blot analysis was utilized to study the effect of cisplatin and the analog on p53 phosphorylation and p53-dependent target genes.Results In response to CDDP and DACH-Ac-Pt, both CDDP-sensitive and CDDP-resistant models demonstrated time- and dose-dependent inductions of total p53 protein and an increase in Ser-15 phosphorylation, which was more pronounced with CDDP. Although phosphorylation of p53 at Ser-392 was also observed in CDDP-treated sensitive and resistant cells, it was weak or absent in response to DACH-Ac-Pt. Lack of Ser-392 phosphorylation by DACH-Ac-Pt, however, did not affect the induction of p21^WAF1/CIP1 or Mdm2. Similarly, inductions of p21^WAF1/CIP1 and Mdm2 were observed in sensitive cells exposed to cisplatin. In marked contrast, cisplatin-mediated induction of p21^WAF1/CIP1 was minimal or absent in resistant cells, but that of Mdm2 was unaffected. Wortmannin, a PI3-kinase (PI3-K) inhibitor, caused a dose-dependent inhibition of total p53 accumulation, Ser-15 phosphorylation and p21^WAF1/CIP1 transactivation in response to both CDDP and DACH-Ac-Pt, indicating that members of the PI3-K family are involved in phosphorylation of p53 and that transactivation of p21^WAF1/CIP1 is p53 dependent.Conclusion These studies demonstrate that cisplatin and DACH-Ac-Pt differentially phosphorylate p53 through independent DNA damage-induced pathways, and that the kinase-mediated phosphorylation of p53 at Ser-15 or Ser-392 is unaltered in resistance. Moreover, the phosphorylation status of Ser-392 on its own does not appear to correlate with p21^WAF1/CIP1 or Mdm2 induction in these studies; however, a lack of increase in p21^WAF1/CIP1 by cisplatin, but not DACH-Ac-Pt, provides a correlation with resistance and its circumvention, and implicates the role for cyclin-dependent kinase inhibitor in the differential cytotoxic effects of the two platinum agents against resistant cells.     

Expression of p53 and p21WAF1/CIP1 Proteins in Gastric and Esophageal Cancers (Comparison with Mutations of the p53 Gene)

The p53 gene has been shown to be commonlymutated in various human cancers, and mutant p53 can actas a dominant oncogene. The intact p53 protein is alsoknown to induce the cyclin-dependent kinase inhibitor p21^WAF1/CIP1 and is implicated incell cycle arrest. We investigated p53 gene alterationsin gastric adenocarcinoma and esophageal squamous cellcarcinoma to elucidate the association of the nuclearaccumulation of the p53 protein and/orp21^WAF1/CIP1 protein. Abnormalities of thetumor suppressor gene p53 protein and the expression ofp21^WAF1/CIP1 protein were analyzed byimmunohistochemical techniques in 32 cases of gastric adenocarcinoma and 15 cases ofesophageal squamous cell carcinoma. Twenty cases ofgastric cancer and five cases of esophageal cancer werealso analyzed for p53 gene mutation by polymerase chain reaction and direct nucleotide sequencing.Overexpression of p53 protein was found in 13/32 (41%)of gastric cancers and 5/15 (33%) of esophageal cancers.We found immunodetectable p53 in 10/14 cases with mutations and in none of 11 cases withoutmutations in gastric and esophageal cancers. Hence,immunohistochemical and genetic analyses gave concordantresults in 84% of 25 cases, revealing a good correlation between immunostaining of p53 and missensemutation of the p53 gene. p53 immunostaining was notobserved in cases with frameshift or splicing mutation.The expression of p21^WAF1/CIP1 protein wasfound in 9/32 (29%) of gastric cancers and 4/15 (27%) ofesophageal cancers and in 2/14 (14%) cases withalteration of the p53 gene and in 5/11 (45%) without.These results suggest that abnormalities of p53 may be closely associated with the pathogenesisof gastric adenocarcinoma and esophageal squamous cellcarcinoma and that the immunoreactivity of p53 proteinis a general indicator of the tumors with altered p53 function. The expression ofp21^WAF1/CIP1 protein was suppressed in theneoplastic tissues with and without p53 genealteration.     

ATRA对甲状腺鳞癌细胞株SW579细胞CDK4、CyclinD1、Rb表达的影响

目的观察全反式维甲酸（ATRA）对甲状腺鳞癌细胞株SW579细胞CDK4、CyclinD1、Rb表达的影响,以探讨其抑癌机制。方法分别以终浓度为10-7、10-6、5×10-6、10-5mol/L的ATRA作用SW579细胞株,对照组加入5μl无水乙醇,各组细胞均在培养24 h后加药。继续培养48 h,RT-PCR、Western blot检测SW579细胞CDK4、CyclinD1、Rb mRNA及其蛋白的表达。结果 ATRA作用后,RT-PCR检测结果表明,经不同浓度ATRA处理的细胞CDK4、Rb mRNA表达水平没有明显变化;CyclinD1的表达明显下调;Western blot检测结果表明经不同浓度ATRA处理的细胞CDK4蛋白表达水平没有明显变化,pRb蛋白的磷酸化水平明显下降,CyclinD1蛋白表达水平明显下降。结论 ATRA在一定浓度范围内可能通过下调甲状腺鳞癌细胞株SW579细胞CyclinD1的表达及Rb蛋白的磷酸化水平抑制细胞增殖。     

曲古抑菌素A对甲状腺鳞癌SW579细胞株p53和p21表达的影响

目的观察曲古抑菌素A(TSA)对甲状腺鳞癌SW579细胞株生长增殖及p53和p21表达的影响,进而探讨TSA抗甲状腺癌的作用机制。方法体外培养SW579细胞,实验分为DMSO组、TSA组(终浓度为50、100、200、400 nmol/L),采用MTT比色法测定细胞增殖活性;用RT-PCR方法检测SW579细胞p53及p21的mRNA表达;用Western blot方法检测SW579细胞p53及p21的蛋白表达。结果 MTT结果显示,TSA可明显抑制SW579的增殖,并呈剂量依赖性。RT-PCR与Western blot检测结果表明,与未加TSA组比较,TSA组随着浓度的逐渐加大,p21 mRNA和蛋白表达水平明显升高;p53 mRNA表达不变,而p53蛋白表达水平上调。结论 TSA在一定浓度范围内对甲状腺鳞癌细胞株SW579有剂量依赖性地增殖抑制作用,其机制可能与TSA提高SW579细胞p53的表达,进而再上调p21的表达有关。     

Clostridium difficile toxin A-induced colonocyte apoptosis involves p53-dependent p21(WAF1/CIP1) induction via p38 mitogen-activated protein kinase

BACKGROUND & AIMS: Clostridium difficile toxin A causes marked apoptosis of colonocytes in vivo and in vitro, which contributes to the formation of ulcers and pseudomembranes. We investigated the role of p53-dependent pathways and p38 mitogen-activated protein kinase (p38) in toxin A-induced colonocyte apoptosis. METHODS: The effects of the activation of p53 and p53-dependent pathways including p21(WAF1/CIP1) were assessed in nontransformed human colonic NCM460 epithelial cells exposed to toxin A. Phosphorylation of p53 protein by p38 was measured by in vitro kinase assay, whereas p21 induction by activated p53 was determined by gel shift assays and RNA silencing (small interfering RNA). The relationship between colonocyte apoptosis and p38/p53-dependent pathways was studied in intact mice. RESULTS: Toxin A stimulated p38 and p53 activation and induced cell cycle arrest (G(2)-M) with persistent expression of p21(WAF1/CIP1). Blockage of p38 by SB203580 inhibited p53 phosphorylation and induction of p21(WAF1/CIP1). In intact mice, p38 blockade suppressed toxin A-mediated destruction of intestinal villi, p21(WAF1/CIP1) expression, and enterocyte apoptosis. In addition, toxin A-mediated p21(WAF1/CIP1) and Bak induction, cytochrome c release, and caspase-3 activation were markedly attenuated in p53-silenced colonocytes, despite active p38. Overexpression of p21(WAF1/CIP1) triggered apoptosis and increased toxin A-associated colonocyte apoptosis. CONCLUSIONS: The signaling pathway for colonocyte apoptosis following toxin A exposure involves p38-dependent activation of p53 and subsequent induction of p21(WAF1/CIP1), resulting in cytochrome c release and caspase-3 activation through Bak induction.     

大鼠肾小球系膜细胞表型的增龄性变化

目的 观察大鼠肾小球系膜细胞随增龄细胞表型及功能的变化特点. 方法取3、12、24月龄健康雄性Wistar大鼠原代系膜细胞进行培养,MTT法检测细胞增殖能力,进行SA-β-gal染色,采用RT-PCR和Western印迹法分别检测p21~(WAF1/CIP1/SDI1)基因及蛋白质的表达变化,并用免疫荧光法检测系膜细胞中p21~(WAF1/CIP1/SDI1)的表达与定位. 结果大鼠肾小球系膜细胞增殖能力随增龄逐渐减弱(P<0.05),SA-β-gal染色阳性率随增龄逐渐增加(P<0.05),p21~(WAF1/CIP1/SDI1) mRNA及蛋白质表达随增龄逐渐增加(P<0.05).免疫荧光结果示p21~(WAF1/CIP1/SDI1)主要在细胞核内表达,荧光强度随增龄逐渐增强 (P<0.05). 结论大鼠肾小球系膜细胞随增龄细胞形态、增殖能力与衰老相关蛋白表达发生明显改变,出现了复制性衰老表型.     

Synergistic antitumor effect of TRATL and doxorubicin on colon cancer cell line SW480

AIM: TRAIL (tumor necrosis factor-related apoptosisinducing ligand) has been reported to specifically induce apoptosis of cancer cells although only a small percentage of cell lines were sensitive to it. Cell lines not responding to TRAIL in vitro were said to be more prone to apoptosis when TRAIL was combined with another anticancer agent.Generally, factors affecting drug-sensitivity involve many apoptosis-related proteins, including p53. The expression of wild-type p53 gene was proposed as an important premise for tumor cells responding to chemotherapy. The present study was to investigate the cell killing action of TRAIL on colon cancer cell line SW480, its synergistic effect with doxorubicin, and the possible mechanisms. METHODS: SW480 cells were cultured in the regular condition and incubated with different levels of agents.Morphologic changes in these cells after treatment were observed under phase-contrast microscope and cytotoxicity by TRAIL alone and in combination with doxorubicin was quantified by a 1-day microculture tetrazolium dye (MTT)assay. In addition, flow cytometry assay (FCM) and transmission electron microscopy were used to detectapoptosis among these cells. Variation of p53 protein level among different groups according to concentrations of agents was measured by Western blot assay.RESULTS: (1) SW480 cells were not sensitive to TRAIL,with IC50＞1 mg@L1 and dose-independent cytotoxicity. (2)SW480 cells were sensitive to doxorubicin at a certain degree,with dose-dependent cytotoxicity and IC50=65.25+3.48μmol@L-1. (3) TRAIL could synergize with doxorubicin to kill SW480 cells effectively, which was represented by the boosted killing effect of doxorubicin on theses cells. IC50 of doxorubicin against SW480 cells sharply reduced when it was combined with TRAIL. (4) Subtoxic TRAIL (100 μg.L-1),combined with subtoxic doxorubicin (0.86 μmol@L1), could kill SW480 cells sufficiently. Cytotoxicity by MTT assay arrived at 80.12+2.67%, which was significantly higher than that by TRAIL or doxorubicin alone, with P=0.006 and 0.003 respectively. This killing effect was partly due to apoptosis. It was proved by large amounts of apoptotic cells under phase-contrast microscopy, cell apoptosis rate of 76.82±1.93 % by FCM assay and typical apoptotic morphology observed through transmission electron microscopy. Increase of apoptosis after combined treatment had no relation with protein level of p53 (P＞0.05). CONCLUSION: SW480 cells are not sensitive to TRAIL, but TRAIL can synergize with lower concentration of doxorubicin to induce apoptosis effectively. The status of p53 protein i snot involved in the mechanism of synergistic apoptosis. It suggests the potential therapeutic applicability of the combination of TRAIL with doxorubicin against colon cancers.     

Selective inhibition of cell growth by activin in SNU-16 cells

AIM: To investigate whether activin regulates the cell proliferation of human gastric cancer cell line SNU-16 through the mRNA changes in activin receptors, Smads and p21CIP1/WAF1. METHODS: The human gastric cancer cell lines were cultured, RNAs were purified, and RT-PCRs were carried out with specifically designed primer for each gene. Among them, the two cell lines SNU-5 and SNU-16 were cultured with activin A for 24, 48 and 72 h. The cell proliferation was measured by MTT assay. For SNU-16, changes in ActRⅠA, ActRⅠB, ActRⅡA, ActRⅡB, Smad2, Smad4, Smad7, and p21CIP1/WAF1 mRNAs were detected with RT-PCR after the cells were cultured with activin A for 24, 48 and 72 h. RESULTS: The proliferation of SNU-16 cells was down regulated by activin A whereas other cells showed no change. Basal level of inhibin/activin subunits, activin receptors, Smads, and p21CIP1/WAF1 except for activinβB mRNAs was observed to have differential expression patterns in the human gastric cancer cell lines, AGS, KATOⅢ, SNU-1, SNU-5, SNU-16, SNU-484, SNU-601, SNU-638, SNU-668, and SNU-719. Interestingly, significantly higher expressions of ActRⅡA andⅡB mRNAs were observed in SNU-16 cells when compared to other cells. After activin treatment, ActRⅠA,ⅠB, andⅡA mRNA levels were decreased whereas ActRⅡB mRNA level increased in SNU-16 cells. Smad4 mRNA increased for up to 48 h whereas Smad7 mRNA increased sharply at 24 h and returned to the initial level at 48 h in SNU-16 cells. In addition, expression of the p21CIP1/WAF1, the mitotic inhibitor, peaked at 72 h after activin treatment in SNU-16 cells. CONCLUSION: Our results suggest that inhibition of cell growth by activin is regulated by the negative feedback effect of Smad7 on the activin signaling pathway, and is mediated through p21CIP1/WAF1 activation in SNU-16 cells.     

Flavopiridol通过调节CDK4/CDK6/cyclinD1复合物表达抑制肝癌细胞增殖

目的研究flavopiridol对肝癌细胞Huh7增殖、凋亡和细胞周期的影响。方法Flavopiridol处理Huh7细胞后,检测细胞增殖和凋亡,进行细胞周期分析。Westernblot检测flavopiridol对cDK4／cDK6／cyclinD1复合物表达的影响。结果Flavopiridol可显著抑制Huh7细胞增殖;Flavopiridol可剂量依赖性导致Huh7细胞发生凋亡,空白对照组凋亡细胞2．65％,550nmol／L剂量处理组凋亡细胞14．17％;Flavopiridol可剂量依赖性引起Huh7细胞G1期阻滞,空白对照组G1期细胞51．06％,550nmol／L剂量处理组G1期细胞57．53％;Flavopiridol可抑制Huh7细胞Gl期相关的蛋白细胞周期素依赖激酶（CDK）4,CDK6,细胞周期素D1（cyclinD1）的表达。结论Flavopiridol通过抑制肝癌细胞G1期cDK4／cDK6／cyclinD1蛋白复合物表达,引起细胞G1期阻滞并发生凋亡,从而抑制细胞增殖。     

The antiangiogenic agent TNP-470 requires p53 and p21CIP/WAF for endothelial cell growth arrest

Targeting the endothelial cell cycle as an antiangiogenic strategy has been difficult given the ubiquitous expression of critical cell cycle regulators. Here, we show that the antiangiogenic drug TNP-470 displays striking cell-type specificity insofar as it induces the expression of p21(CIP/WAF), a cyclin-dependent kinase inhibitor, in endothelial cells but not in embryonic or adult fibroblasts. Moreover, primary endothelial cells isolated from p53(-/-) and p21(CIP/WAF-/-) mice are resistant to the cytostatic activity of TNP-470. We also demonstrate that p21(CIP/WAF-/-) mice are resistant to the antiangiogenic activity of TNP-470 in the basic fibroblast growth factor corneal micropocket angiogenesis assay. We conclude that TNP-470 induces p53 activation through a unique mechanism in endothelial cells leading to p21(CIP/WAF) expression and subsequent growth arrest.