X-linked inhibitor of apoptosis protein inhibition induces apoptosis and enhances chemotherapy sensitivity in human prostate cancer cells

Androgen-insensitive prostate cancer cells are highly resistant to several chemotherapeutic drugs and are characterized by the appearance of apoptosis-resistant cells. In this study, we identified the critical role of X-linked inhibitor of apoptosis protein (XIAP), a potent antiapoptotic factor, in conferring chemotherapy resistance in an androgen-insensitive DU145 human prostate cancer cell line. Results reveal that DU145 cells were highly resistant to cisplatin, but this resistance was overridden when the cells were treated for a prolonged time (>96 hours) with cisplatin (IC(50) = 27.5 to 35.5 micromol/L). A decrease in levels of XIAP and Akt/phospho-Akt and an increase in caspase-3 activity were identified to be key factors in cisplatin sensitivity (40% to 55% decrease in cell viability) at later time points. In contrast, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment caused a 40% to 50% decrease in cell viability within 6 hours (IC(50) = 135 to 145 ng/mL). However, increasing concentrations or prolonged treatment with TRAIL did not change drug potency. A significant increase in caspase-3 activity was observed with TRAIL treatment with no apparent change in XIAP levels. Specific inhibition of XIAP expression using an antisense XIAP phosphorodiamidate morpholino oligomer induced apoptosis and increased caspase-3 activity. Combination of cisplatin with XIAP antisense potentiated cisplatin sensitivity by decreasing the IC(50) from >200 micromol/L with cisplatin alone to 9 to 20 micromol/L and decreasing incubation time required for activity from 96 to 24 hours. Similarly, TRAIL in combination with XIAP antisense phosphorodiamidate morpholino oligomer enhanced TRAIL potency by 12- to 13-fold. In conclusion, abrogation of XIAP expression is essential for therapeutic apoptosis and enhanced chemotherapy sensitization in androgen-refractory prostate cancer cells.     

重组XIAP对H2O2诱导小肠上皮细胞凋亡的保护作用

背景:XIAP在细胞抗凋亡中发挥关键作用,能作为与凋亡相关的多种疾病预防治疗的靶点。目的:构建大鼠重组XIAP表达质粒,观察其对H2O2诱导细胞凋亡的保护作用和机制。方法:采用RT-PCR从大鼠小肠上皮细胞IEC-6扩增出大鼠XIAP基因ORF序列,插入pCMV6-AC-GFP载体,重组成pXIAP-GFP表达质粒,测序鉴定。以重组pXIAP-GFP与对照质粒pCMV6-AC-GFP转染IEC-6细胞,Westernblot检测细胞重组XIAP的表达,同时在H2O2诱导细胞凋亡后,MTT法检测细胞存活,Westernblot检测细胞Casepase-3表达。结果与结论:经测序证实pXIAP-GFP重组序列正确,Westernblot证实将其转染IEC-6细胞后细胞正确表达XIAP,表明pXIAP-GFP重组质粒构建成功;在转染质粒和H2O2诱导凋亡后,与对照质粒pCMV6-AC-GFP组比较,pXIAP-GFP组细胞A值增高,Caspase-3表达降低。表明重组XIAP能通过抑制Caspase-3的表达抵抗H2O2诱导的细胞凋亡。     

Activity of lapatinib is independent of EGFR expression level in HER2-overexpressing breast cancer cells

Epidermal growth factor receptor (EGFR/ErbB1) and HER2 (ErbB2/neu), members of the ErbB receptor tyrosine kinase family, are frequently overexpressed in breast cancer and are known to drive tumor growth and progression, making them promising targets for cancer therapy. Lapatinib is a selective competitive inhibitor of both the HER2 and EGFR tyrosine kinases. Although lapatinib showed significant activity in patients with HER2-positive breast cancer, the role of EGFR in the response of breast cancer to lapatinib has not been defined. Here, we examined the role of EGFR expression levels in the sensitivity of HER2-overexpressing breast cancer cells to lapatinib. Depletion of EGFR by EGFR small-interfering RNA knockdown did not affect lapatinib sensitivity in these cells, whereas treated HER2 siRNA knockdown cells became more resistant to lapatinib. We conclude that the in vitro activity of lapatinib is not dependent on EGFR expression level in HER2-overexpressing breast cancer cells.     

XIAP表达在ATRA诱导APL细胞分化中的意义

目的 探讨X染色体相关凋亡抑制蛋白在全反式维甲酸诱导急性早幼粒细胞白血病细胞分化过程中的表达意义.方法 以急性早幼粒白血病细胞NB4为细胞模型,利用细胞计数、瑞氏染色、蛋白质免疫印记等方法.观察细胞经ATRA处理不同时间后细胞分化情况以及XIAP蛋白表达情况.结果 1μmol/L的ATRA可抑制NB4细胞的生长,在用药处理72h后细胞出现明显的分化,XIAP蛋白含量明显下降.结论 在ATRA诱导APL细胞分化过程中,凋亡抑制蛋白XIAP表达明显下调.     

Overexpression of X-linked inhibitor of apoptosis protein protects against noise-induced hearing loss in mice

Apoptosis is responsible for cochlear cell death induced by noise. Here, we show that transgenic (TG) mice that overexpress X-linked inhibitor of apoptosis protein (XIAP) under control of the ubiquitin promoter display reduced hearing loss and cochlear damage induced by acoustic overstimulation (125?dB sound pressure level, 6?h) compared with wild-type (WT) littermates. Hearing status was evaluated using the auditory brainstem response (ABR), whereas cochlear damage was assessed by counts of surviving hair cells (HCs) and spiral ganglion neurons (SGNs) as well as their fibers to HCs. Significantly smaller threshold shifts were found for TG mice than WT littermates. Correspondingly, the TG mice also showed a reduced loss of HCs, SGNs and their fibers to HCs. HC loss was limited to the basal end of the cochlea that detects high frequency sound. In contrast, the ABRs demonstrated a loss of hearing sensitivity across the entire frequency range tested (2-32?kHz) indicating that the hearing loss could not be fully attributed to HC loss alone. The TG mice displayed superior hearing sensitivity over this whole range, suggesting that XIAP overexpression reduces noise-induced hearing loss not only by protecting HCs but also other components of the cochlea.     

Adding Pertuzumab to Trastuzumab and Taxanes in HER2 positive breast cancer

Introduction: The monoclonal antibody trastuzumab has improved the median disease free and overall survival of patients with early stage breast cancer that overexpresses the human epidermal growth factor receptor 2 (HER2). Despite this advance, some patients experience cancer relapse and novel approaches are always needed. One such advance is the monoclonal antibody pertuzumab, which prevents dimerisation between members of the HER family of transmembrane glycoprotein receptors.

Areas covered: In this review, the authors analyse recent research which has focused on the development of new HER2 targeting agents for HER2-positive breast cancer, particularly pertuzumab, and its addition to trastuzumab and taxanes.

Expert opinion: Pertuzumab has significantly improved disease control in patients with advanced HER2 positive breast cancer when added to chemotherapy and trastuzumab. Although pertuzumab has also increased response rates in the preoperative setting, this has not yet translated into increased overall survival. The authors believe that future research should focus on improvements in novel biomarkers to select patients for new treatments.     

Abrogation of TGF-β signaling enhances chemokine production and correlates with prognosis in human breast cancer

In human breast cancer, loss of carcinoma cell–specific response to TGF-β signaling has been linked to poor patient prognosis. However, the mechanisms through which TGF-β regulates these processes remain largely unknown. In an effort to address this issue, we have now identified gene expression signatures associated with the TGF-β signaling pathway in human mammary carcinoma cells. The results strongly suggest that TGF-β signaling mediates intrinsic, stromal-epithelial, and host-tumor interactions during breast cancer progression, at least in part, by regulating basal and oncostatin M–induced CXCL1, CXCL5, and CCL20 chemokine expression. To determine the clinical relevance of our results, we queried our TGF-β–associated gene expression signatures in 4 human breast cancer data sets containing a total of 1,319 gene expression profiles and associated clinical outcome data. The signature representing complete abrogation of TGF-β signaling correlated with reduced relapse-free survival in all patients; however, the strongest association was observed in patients with estrogen receptor–positive (ER-positive) tumors, specifically within the luminal A subtype. Together, the results suggest that assessment of TGF-β signaling pathway status may further stratify the prognosis of ER-positive patients and provide novel therapeutic approaches in the management of breast cancer.     

胸腔积液及肺泡灌洗液中X链锁凋亡抑制蛋白及生存素检测对肺癌的早期诊断价值

目的 探讨胸腔积液及肺泡灌洗液中X链锁凋亡抑制蛋白(X-linked inhibitor of apoptosis protein,XIAP)及生存素(survivin)水平对肺癌早期诊断的临床价值.方法 60例经病理确诊的肺癌伴胸腔积液患者的胸腔积液及肺泡灌洗液作为肺癌组,60倒结核性渗出性胸膜炎患者的胸水及肺泡灌洗液为对照组,以酶联免疫吸附法测定2组中XIAP、生存素含量,并对其进行统计学分析.结果 恶性胸腔积液中XIAP水平高于结核性胸腔积液患者,(84.83±27.40)ng/L vs(47.23±21.58)ng/L(P＜0.05),恶性胸水患者肺泡灌洗液中XIAP水平明显高于结核性胸腔积液患者肺泡灌洗液患者,(85.02±41.22) ng/L vs(43.10±28.61)ng/L( P＜0.05);恶性胸腔积液中survivin浓度高于结核性胸腔积液患者,(85.54±29.18) ng/L vs (43.15±21.98) ng/L(P＜0.05);恶性组肺泡灌洗液中survivin显著高于结核性胸腔积液患者的肺泡灌洗液中survivin,(95.27±34.54) ng/L vs(48.99±22.17)ng/L(P＜0.05);单个检查XIAP、生存素在胸腔积液中的敏感度85.0％,90.0％,在肺泡灌洗液中的敏感度75.0％、95.0％,XIAP+生存素联合检查在胸腔积液敏感度及肺泡灌洗液中均为95.0％;但特异度降低.结论 胸腔积液中XIAP及生存素的测定有利于良恶性胸腔积液的鉴别诊断,同时由于肺泡灌洗中XIAP及生存素的含量高于胸腔积液,且敏感度较高,对于肺癌的早期诊断具有重要的意义.     

Pertuzumab: evolving therapeutic strategies in the management of HER2-overexpressing breast cancer

Colorectal cancer is an important public health problem worldwide. Gene therapy has therapeutic potential for patients with advanced or recurrent colorectal cancer, incurable by conventional treatments. To date, many strategies of gene therapy have been explored, including mutant gene correction, prodrug activation, immune stimulation and genetically-modified oncolytic viruses. Although the preclinical results of gene therapy for colorectal cancer have shown promise, gene therapy is still at an early stage of clinical development and has not yet shown a significant therapeutic benefit for patients. The main obstacles for introduction of gene therapy to patients are poor targeting selectivity of the vectors and inefficient gene transfer. As the science supporting tumour-selective vectors evolves, gene therapy may expand rapidly in the clinical practice of colorectal cancer treatment.     

X连锁凋亡抑制蛋白相关因子-1诱导细胞凋亡的研究进展

肿瘤是一种多基因疾病，其发生、发展涉及多条信号通路中多种基因的调控。细胞凋亡异常是肿瘤形成及耐药的重要机制，而诱导凋亡已成为治疗肿瘤的主要方法之一。凋亡抑制蛋白家族（inhibitor of apototic proteins，IAPs）是近年来受到普遍关注的蛋白因子，且都具有高度保守的杆状病毒凋亡抑制因子重复序列的结构域，可作用于凋亡信号通路中重要的天冬氨酸特异性半胱氨酸蛋白（Caspases）级联反应的起始或效应阶段，调节Caspase-3、Caspase-7、Caspase-9功能．从而明显抑制细胞凋亡。     

Cyclin D3 is down-regulated by rapamycin in HER-2-overexpressing breast cancer cells

Rapamycin and its analogues are being tested as new antitumor agents. Rapamycin binds to FKBP-12 and this complex inhibits the activity of FRAP/mammalian target of rapamycin, which leads to dephosphorylation of 4EBP1 and p70 S6 kinase, resulting in blockade of translation initiation. We have found that RAP inhibits the growth of HER-2-overexpressing breast cancer cells. The phosphorylation of mammalian target of rapamycin, p70 S6 kinase, and 4EBP1 is inhibited by rapamycin and cells are arrested in the G1 phase, as determined by growth assays, fluorescence-activated cell sorting analysis, and bromodeoxyuridine incorporation studies. Rapamycin causes down-regulation of cyclin D3 protein, retinoblastoma hypophosphorylation, loss of cyclin-dependent kinase (cdk) 4, cdk6, and cdk2 activity. The half-life of cyclin D3 protein decreases after rapamycin treatment, but not its synthesis, whereas the synthesis or half-life of cyclin D1 protein is not affected by the drug. Additionally, rapamycin caused accumulation of ubiquitinated forms of cyclin D3 protein, proteasome inhibitors blocked the effect of rapamycin on cyclin D3, and rapamycin stimulated the activity of the proteasome, showing that the effect of rapamycin on cyclin D3 is proteasome proteolysis dependent. This effect depends on the activity of HER-2 because Herceptin, a neutralizing antibody against HER-2, is able to block both the induction of proteasome activity and the cyclin D3 down-regulation due to rapamycin. Furthermore, inhibition of HER-2 gene expression by using small interfering RNA blocked the rapamycin effects on cyclin D3. These data indicate that rapamycin causes a G1 arrest in HER-2-overexpressing breast cancer cells that is associated with a differential destabilization and subsequent down-regulation of cyclin D3 protein.     

Targeting the apoptotic machinery in pancreatic cancers using small-molecule antagonists of the X-linked inhibitor of apoptosis protein

Resistance to apoptosis is a hallmark of many solid tumors, including pancreatic cancers, and may be the underlying basis for the suboptimal response to chemoradiation therapies. Overexpression of a family of inhibitor of apoptosis proteins (IAP) is commonly observed in pancreatic malignancies. We determined the therapeutic efficacy of recently described small-molecule antagonists of the X-linked IAP (XIAP) in preclinical models of pancreatic cancer. Primary pancreatic cancers were assessed for XIAP expression by immunohistochemistry, using a pancreatic cancer tissue microarray. XIAP small-molecule antagonists ("XAntag"; compounds 1396-11 and 1396-12) and the related compound 1396-28 were tested in vitro in a panel of human pancreatic cancer cell lines (Panc1, Capan1, and BxPC3) and in vivo in s.c. xenograft models for their ability to induce apoptosis and impede neoplastic growth. In addition, pancreatic cancer cell lines were treated with XAntags in conjunction with either tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or with radiation to determine potential synergy for such dual targeting of the apoptotic machinery. XIAP was overexpressed in 14 of 18 (77%) of primary pancreatic cancers. The XAntags1396-11 and 1396-12, but not the inactive isomer 1396-28, induced profound apoptosis in multiple pancreatic cancer cell lines tested in vitro, with a IC(50) in the range of 2 to 5 mumol/L. Mechanistic specificity of the XAntags for the baculoviral IAP repeat-2 domain of XIAP was shown by preferential activation of downstream "effector" caspases (caspase-3 and caspase-7) versus the upstream "initiator" caspase-9. S.c. BxPC3 xenograft growth in athymic mice was significantly inhibited by monotherapy with XAntags; treated xenografts showed marked apoptosis and increased cleavage of caspase-3. Notably, striking synergy was demonstrable when XAntags were combined with either TRAIL or radiation therapy, as measured by growth inhibition in vitro and reduced colony formation in soft agar of pancreatic cancer cell lines, at dosages where these therapeutic modalities had minimal to modest effects when used alone. Finally, XAntags in combination with the standard-of-care agent for advanced pancreatic cancer, gemcitabine, resulted in significantly greater inhibition of in vitro growth than gemcitabine alone. Our results confirm that pharmacologic inhibition of XIAP is a potent therapeutic modality in pancreatic cancers. These antagonists are independently capable of inducing pancreatic cancer cell death and also show synergy when combined with proapoptotic ligands (TRAIL), with radiation, and with a conventional antimetabolite, gemcitabine. These preclinical results suggest that targeting of the apoptotic machinery in pancreatic cancers with XAntags is a promising therapeutic option that warrants further evaluation.     

Sensitizing HER2-overexpressing cancer cells to luteolin-induced apoptosis through suppressing p21(WAF1/CIP1) expression with rapamycin

HER2 overexpression, which confers resistance to various therapeutic regimens, correlates with a poor clinical prognosis. In this study, we showed that luteolin, a naturally occurring flavonoid, is a potent stimulator of HER2 degradation. Luteolin effectively inhibited cell proliferation and induced apoptosis in HER2-overexpressing cancer cells. Furthermore, we found that low doses of luteolin up-regulated p21 expression and high doses of luteolin down-regulated its expression. Examination of the Akt/mammalian target of rapamycin (mTOR) signaling revealed that this signaling was only transiently inhibited by low doses of luteolin, which suggested that the inability to cause sustained Akt/mTOR inhibition may contribute to p21 induction and provide a survival advantage to HER2-overexpressing cancer cells. To test this hypothesis, we showed that the combined use of luteolin and mTOR inhibitor rapamycin prevented low doses of luteolin from inducing p21 expression, and HER2-overexpressing cancer cells would be sensitized toward luteolin-induced apoptosis. In addition, p21 small interfering RNA also increased the luteolin-induced cell death. In nude mice with xenografted SKOV3.ip1-induced tumors, luteolin significantly inhibited HER2 expression and tumor growth in a dose-dependent manner, and rapamycin further enhanced the effect of luteolin with a concomitant p21 inhibition. These results reveal an intriguing finding that suppressing p21 expression might have therapeutic implications and further suggest that combination of mTOR inhibitors may be a promising strategy to help increase the efficacy of preventive or therapeutic compounds against HER2-overexpressing tumors.     

Reversion of RhoC GTPase-induced inflammatory breast cancer phenotype by treatment with a farnesyl transferase inhibitor

Inflammatory breast carcinoma (IBC) is a highly aggressive form of locally advanced breast cancer that has the ability to invade and block the dermal lymphatics of the skin overlying the breast. In a previous series of studies, our laboratory identified overexpression of RhoC GTPase in >90% of IBCs (K. L. van Golen et al., Clin. Cancer Res., 5: 2511-2519, 1999) and defined RhoC as a mammary oncogene involved in conferring the metastatic phenotype (K. L. van Golen et al., Cancer Res., 60: 5832-5838, 2000). RhoC GTPase is involved in cytoskeletal reorganization during cellular motility. Farnesyl transferase inhibitors (FTIs) were previously shown to be effective in modulating tumor growth in Ras-transformed tumor cells. Recently, studies have focused on RhoB as a putative non-Ras target of FTI action. In the present study, we assessed the effect of the FTI L-744,832 on RhoC-overexpressing IBC and RhoC-transfected human mammary epithelial (HME-RhoC) cells. Treatment of the SUM149 IBC cell line and HME-RhoC transfectants with the FTI L-744,832 led to reversion of the RhoC-induced phenotype, manifested by a significant decrease in anchorage-independent growth, motility, and invasion. Although RhoC expression and activation were not affected, RhoB levels were increased by FTI treatment. Transient transfection of geranylgeranylated RhoB (RhoB-GG) into the same cells reproduced the effects of the FTI, thus suggesting that FTI-induced reversion of the RhoC phenotype may be mediated by an increase in RhoB-GG levels. These data provide direct evidence that FTIs may find use in the clinic when directed against RhoC-overexpressing tumors and suggest appropriate biological markers to evaluate during FTI treatment.     

上尿路肿瘤ErbB1、ErbB2和ErbB3受体表达和临床病理的关系

目的:探讨上尿路肿瘤患者ErbB1、ErbB2和ErbB3受体表达和临床病理的关系.方法:对70例输尿管和肾盂癌患者行肾及输尿管切除术外加膀胱袖套切除(随访1～165个月,平均38个月),切除的标本连续分段进行ErbB1、ErbB2和ErbB3免疫组化染色.通过Kaplan-Meier图表、Log-rank检验和Cox比例风险模型分析ErbB受体表达和关于复发、进展、无瘤生存期和总生存期等临床结果之间的关系.结果:ErbB1、ErbB2和ErbB3在肿瘤的表达分别为7例(10.0%),10例(14.3%)和21例(30.0%).34例(48.6%)至少有1个受体表达和6例同时有2或3种受体表达.ErbB2表达和肿瘤浸润的关系有显著意义(P=0.03),而ErbB1和ErbB3没有.膀胱肿瘤复发的发生率和是否输尿管肿瘤及ErbB2表达有显著关联(P分别为0.03和0.03).在多变量分析中,肿瘤分期和ErbB2表达是肿瘤进展(P分别为0.03和0.02)、无瘤生存(P分别为0.04和0.01)和总生存(P分别为0.03和0.04)的预后因素.结论:ErbB2可以预测上尿路肿瘤进展和相关生存.     

乳腺癌组织Livin和PTEN的表达及与肿瘤细胞凋亡的相关性

目的研究乳腺癌组织中凋亡抑制蛋白Livin和抑癌基因PTEN的表达与肿瘤细胞凋亡的关系,探讨两者在乳腺癌细胞凋亡、侵袭转移中的作用机制。方法应用免疫组化Elivision法检测90例乳腺癌和30例乳腺纤维腺瘤组织中Livin和PTEN的表达,另以TUNEL法检测细胞凋亡情况,分析Livin和PTEN表达与乳腺癌细胞凋亡的关系。结果在90例乳腺癌中Livin和PTEN的表达阳性率分别为54.4%, 48.9%,凋亡指数为4.79%±1.62%,与良性对照组比较均有显著差异（P < 0.01）;Livin阳性表达与乳腺癌肿瘤大小、临床分期呈正相关（P < 0.05）,与凋亡指数呈负相关（P < 0.05）,与年龄、病理分级、淋巴结转移未见显著相关（P>0.05）;PTEN表达与乳腺癌淋巴结转移、临床分期呈负相关（P < 0.05）,与凋亡指数呈正相关（P < 0.05）,与年龄、肿瘤大小、病理分级未见显著相关（P>0.05）。结论Livin和PTEN对乳腺癌细胞凋亡分别起抑制和促进作用,Livin高表达和PTEN失表达都可通过抑制细胞凋亡促进乳腺癌的侵袭转移,调控两种基因的表达有望影响乳腺癌细胞凋亡以及乳腺癌的发生发展。     

乳腺癌HER2与IGF-IR和PTEN表达的相关性

目的探讨中国人乳腺癌中HER2与IGF-IR和PTEN之间的相关性。方法分别在65例HER2(+)和108例HER2(-)的乳腺浸润性导管癌中,用免疫组化EnVision法检测IGF-IR和PTEN蛋白的表达。结果 HER2(+)组中,IGF-IR和PTEN阳性率分别为78.5%(51/65)和52.3%(34/65);HER2(-)组中,IGF-IR和PTEN阳性率分别为71.3%(77/108)和68.5%(74/108)。阳性组IGF-IR过表达率高于阴性组,但差异不显著(P>0.05);阳性组PTEN表达低于HER2阴性组,差异显著(P<0.05)。HER2阳性和阴性组中,IGF-IR过表达与各临床病理参数间均无相关性(P>0.05);但阳性组中,IGF-IR高表达与淋巴结转移密切相关(P<0.05)。对全部乳腺癌标本分析显示,PTEN表达与癌的组织学分级和淋巴结转移呈负相关(P<0.05),与ER表达呈正相关(P<0.05),与其他临床指标间无相关性(P>0.05)。PTEN表达与IGF-IR和HER2表达呈负相关(P<0.05)。结论 PTEN表达丢失与乳腺癌进展密切相关;HER2阳性的乳腺癌中常见PTEN蛋白表达丢失,且IGF-IR可能参与促进了癌细胞的转移过程。PTEN蛋白缺失与IGF-IR蛋白过表达均与乳腺癌进展相关联,其分子机制和相关意义有待于进一步研究。     

Down-regulation of X-linked inhibitor of apoptosis synergistically enhanced peroxisome proliferator-activated receptor gamma ligand-induced growth inhibition in colon cancer

We found previously that X-linked inhibitor of apoptosis protein (XIAP), a potent endogenous inhibitor of apoptosis, is overexpressed in colon cancer. Ligand-induced activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to exert proapoptotic and antiproliferative effects in many cancer cell types. However, neither XIAP down-regulation alone nor monotherapy using PPARgamma ligands is potent enough to control colon cancer. We explored whether XIAP inhibition and PPARgamma activation offer a synergistic anticancer effect in colon cancer. HCT116-XIAP(+/+) and HCT116-XIAP(-/-) cells were treated with troglitazone or 15-deoxy-Delta(12,14)-prostaglandin J(2) (15-PGJ(2)). Cell growth and apoptosis were measured. Nude mice were s.c. inoculated with HCT116 cells with or without oral troglitazone. Tumor growth, angiogenesis, and apoptosis were measured. Troglitazone- and 15-PGJ(2)-induced growth inhibition and apoptosis were more prominent in HCT116-XIAP(-/-) cells. Troglitazone- and 15-PGJ(2)-induced apoptosis correlated with enhanced cleavage of caspases and poly(ADP-ribose) polymerase, which were more profound in HCT116-XIAP(-/-) cells. Pretreatment of cells with XIAP inhibitor 1396-12 also sensitized HCT116-XIAP(+/+) cells to PPARgamma ligand-induced apoptosis. Troglitazone significantly retarded the growth of xenograft tumors, more significantly so in HCT116-XIAP(-/-) cell-derived tumors. Reduction of tumor size was associated with reduced expression of Ki-67, vascular endothelial growth factor, and CD31 as well as increased apoptosis. Loss of XIAP significantly sensitized colorectal cancer cells to PPARgamma ligand-induced apoptosis and inhibition of cell proliferation. Thus, simultaneous inhibition of XIAP and activation of PPARgamma may have a synergistic antitumor effect against colon cancer.