Relationship between telomere length and radiosensitivity in various human cancer cell lines

Objective： To investigate the relationship between telomere length and radiosensitivity in various human cancer cell lines with the expectation to find a valid and common predictor of radiosensitivity for different cancers. Methods： Eight human cancer cell lines were used, including five human breast cancer cell lines （ZR-75-30, MCF-7, MDA-MB-435S, T-47-D, F539-1590）, two human larynx squamous carcinoma cell lines （Hep-2 and Hep-2R） and a human malignant glioma cell line （U251）. Among them, the radioresistant cell line Hep-2R was isolated and established from a radiosensitive human larynx squamous carcinoma cell line Hep-2 by our center. The radiobiological characteristics of the eight lines were analyzed by the method of colony-forming assay and the radiosensitivity parameters were calculated. Telomere length was analyzed by TRF （mean Telomere Restriction Fragments） length assay. Results： The radioresistance of Hep-2R cell line proved to be stable in long-term passaged cultures as well as in frozen samples. Radiosensitivity parameters are different among those lines. The SF2 values of Hep-2 and U251 are 0.4148 and 0.7520, respectively; The SF2 values of breast cancer cell lines are between those of Hep-2 and U251. The TRF of Hep-2R is 11.12Kb, longer than three times that of its parental counterpart. There is a positive correlation both between SF2 and TRF （r=-0.786, P〈0.05）, and between Do and TRF （r=0.905, P〈0.01）. Conclusion： It is concluded that radiosensitivity and telomere length （TRF） are negatively correlated, TRF could be a valid predictor for radiosensitivity.     

Combined antitumor effect of ursolic acid and 5-fluorouracil on human esophageal carcinoma cell Eca-109 <Emphasis Type="Italic">in vitro</Emphasis>

Objective:To study the combined antitumor effect and possible mechanisms of ursolic acid with 5-fluorouracil (5-FU) on human esophageal carcinoma cell Eca-109 in vitro. Methods:Eca-109 cells were treated with ursolic acid (10-50 μmol/L) and/or 5-fluorouracil (48.0-768.8 μmol/L) for 48 h in vitro. And then cell proliferation was determined by MTT assay. Cell cycle and apoptosis rate were analyzed by flow cytometry (FCM). The morphological changes of apoptosis were observed by fluorescent microscopy. At last ...     

生长抑素增强三苯氧胺抗乳腺癌作用的体外研究

Objective:To study the antineoplastic effects of tamoxifen(TAM) in combination with a somatostain analogue(octreotide,OCT) on breast cancer.Methods:Estrogen receptor(ER)-positive(MCF-7) and ER-negative(MDA-MB-435S)human breast carcinoma cell lines were treated with TAM or OCT,or combination of both agents in vitro.Cell proliferation was evaluated by MTT assay,distribu-tion of cell cycle and rate of apoptosis were detemined by flow cytometry.Results:The inhibitory effect of OCT or TAM on proliferation of MCF-7 cells was associated with cell arrest in G0/G1 phase and induction of apoptosis.The inhibitory effect on proliferation of MCF-7 cells enhanced when treatment of TAM combined with OCT.The increased rate of apoptosis induced by combination of TAM and OCT was much higher than use of either TAM or OCT alone.TAM or OCT also had weak inhibitory effect on MDA-MB435S cell.The cells were arrested at S phase by TAM and at G0/G1 phase by OCT, but the induction of apoptosis was not identified.However,the rate of apoptosis was 22.7% if combined treatment of TAM and OCT applied.Conclusion:TAM and OCT can synergistically inhibit proliferation and induce apoptosis of ER-positive and ER-negative breast cancer cells.The synergism of TAM and OCT may be of interest in the clinical treatment of breast carcinoma.     

体外Fas介导细胞凋亡的细胞周期特异性的检测方法

Objective： To establish a system in detecting the cell cycle specificity induced by recombinant human Fas ligand in vitro, so as to provide a reliable platform for further exploring the mechanism of cell cycle control and regulation in Fas-mediated apoptosis. Methods： The target cells-leukaemia cell lines and activated peripheral blood lymphocytes stimulated by phytohemagglutinin were incubated with recombinant human Fas ligand for 6 to 36 h, apoptosis was detected by sub-G1, common annexin-Ⅴ/PI and modified annexin Ⅴ and propidium iodide （API） methods and analysed by flow cytometry. Results： The modified API method demonstrated that Fas-mediated apoptosis was cell cycle specific and initiated at G1 phase. The common annexinⅤ/PI method showed the most appropriate condition for the detection of typical cell cycle-specific apoptosis. The sub-G1 method could only illuminate late apoptosis and DNA histogram. Conclusion： Fas-mediated apoptosis was cell cycle-specific and initiated at G 1 phase. Based on the modified API and common AnnexinⅤ/PI methods, the establishment of stable and typical cell cycle-specific model in Fas-mediated apoptosis in vitro was feasible.     

Effect on biological behavior of chemotherapy-resistant tumor cells by human wild-type p53, GM-CSF and B7-1 genes via recombinant adenovirus

　Objective To explore the effect on biological behavior of chemotherapy-resistant tumor cells by human wild-type p53, GM-CSF and B7-1 genes mediated via recombinant adenovirus. Methods p53-abnormal KB-v200 (VCR resistant) and KB-s (VCR sensitive) cell lines were used as model tumor cells, which are resistant and sensitive to chemotherapeutic drugs respectively. After infected with recombinant adenovirus carrying human wild-type p53, GM-CSF and B7-1 genes, changes in biological behavior (including drug sensitivity) of these two kinds of gene-transduced cancer cells were observed. Results Both of the cell lines were susceptible to adenovirus, all of three exogenous genes (p53, GM-CSF and B7-1) could be effectively expressed in these cell lines, their growth was suppressed, and apoptosis was induced. The drug-pumping-out function of Pgp glycoprotein on the cytomembrane of drug-resistant KB-v200 cells was markedly affected 48h after transfection of the recombinant adenovirus, revealed by increase of the amount of rhodamine 123 accumulation in the cells. The MTT assay also indicated the reversal of their sensitivity to VCR drugs. In vivo experiment in nude mice it was demonstrated reduction of tumorigenicity of the KB-v200 cells or KB-s cells infected with the recombinant adenovirus, and increase of their sensitivity to VCR. Conclusion The clinical application of this recombinant adenovirus carrying agents might be more effective in treatment of tumors with multidrug resistance (MDR).     

EXPRESSION OF c-erbB-2, p53, p16 IN SQUAMOUS CELL CARCINOMA OF ANTERIOR TONGUE IN CHINA POPULATION

Objective: Aberrant expression of c-erbB-2, p53, p16 has been found in oral squamous cell carcinoma. We therefore examined expression of these proteins in squamous cell carcinoma of the anterior tongue and compared their relationship with clinical stages and prognosis. Methods: Seventy-six patients with squamous cell carcinoma of the anterior tongue never treated before were obtained from Cancer Hospital, CAMS. Archive tissues of carcinoma and paracarcinoma were examined for c-erbB-2, p53 and p16 expression by immunohistochemistry.Results: The rates of immunopositive staining of c-erbB-2, p53 and p16 were 64.5%, 61.8% and 23.7% respectively; the positive rates in paracarcinoma mucosa were 19.7%, 22.6% and 55.3% respectively. Overexpression of c-erbB-2 was significantly correlated with short overall survival, metastasis and staging. Overexpression of paracarcinoma p53 was significantly correlated with local recurrence.Conclusion. c-erbB-2 may be used as a prognosis marker for the patients with squamous cell carcinoma of the anterior tongue and p53 as a recurrence marker.     

TRICHOSTATIN A INHIBITS PROLIFERATION, INDUCES APOPTOSIS AND CELL CYCLE ARREST IN HELA CELLS

Objective： The histone deacetylase inhibitors （HDACIS） have been shown to inhibit cancer cell proliferation, stimulate apoptosis, an induce cell cycle arrest. Our purpose was to investigate the antiproliferative effects of a HDACI, trichostatin A （TSA）, against human cervical cancer cells （HeLa）. Methods： HeLa cells were treated in vitro with various concentrations of TSA. The inhibitory effect of TSA on the growth of HeLa cells was measured by MTT assay. To detect the characteristic of apoptosis chromatin condensation, HeLa cells were stained with Hoechst 33258 in the presence of TSA. Induction of cell cycle arrest was studied by flow cytometry. Changes in gene expression of p53, p21wafl and p27Kipl were studied by semiquantitative RT-PCR. Results： TSA inhibited cell growth in a time- and dose-dependent manner. Hoechst 33258 staining assay showed that TSA induced apoptosis. Cell cycle analysis indicated that treatment with TSA decreased the proportion of cells in S phase and increased the proportion of cells in G0/G1 and/or G2/M phases of the cell cycle. This was concomitant with overexpression of genes related to malignant phenotype, including an increase in p53, p21wall and p27Kipl. Conclusion： These results suggest that TSA is effective in inhibiting growth of HeLa cells in vitro. The findings raise the possibility that TSA may prove particularly effective in treatment of cervical cancers.     

CHEMOSENSITIVITY OF MGc80-3 HUMAN GASTRIC ADENOCARCINOMA CELLS AND ITS CLINICAL SIGNIFICANCE

In the present study, the chemosensitivity of MGc80-3 human gastric adenocarcinoma cells was determined by means of colony-forming assay and the in vitro activities of 10 anticancer drugs were examined on the basis of the clinically achievable peak plasma drug concentration. The results showed that MGc80-3 cells were most sensitive to mitomyc'n C, adriamycin and 5-fluorouracil, being consistent with the response noted in clinical gastric cancer. This cell line may retain its original drug sensitivity and may be useful in screening for new compounds with activity against this disease.     

Antitumor effects of artesunate on human breast carcinoma MCF-7 cells and IGF-IR expression in nude mice xenografts

Purpose： The objective of this study was to investigate the anti-tumor effects and analyze the mechanism of artesunate （ART） action on breast cancer in vivo using tumor transplanted nude mice. Methods： The human breast tumor cell line MCF-7 was transplanted into nude mice, and the animals were treated with various doses of ART alone or in combination with cyclophosphamide （CTX） or normal saline （NS）. The tumor inhibitory effects were observed and compared, and the ultrastructural morphology of the transplanted tumor cells was observed by electron microscopy. The apoptosis rates and cell cycle status were detected by flow cytometry （FCM）. The expression of apoptosis-related proteins p53, Bcl-2, Bax and Caspase-3 were detected by immunohistochemistry and IGF-IR was detected by western blot. The expression correlation for these proteins was also analyzed. Results： The tumor inhibition rates in the low dose ART group, high dose ART group, CTX group and combined drug therapy group were （24.39±10.20）%, （40.24±7.02）%, （57.01±5.84）% and （68.29±5.1）%, respectively. The cell cycle was arrested in phase G0/Gt after treatment with ART. The expression of Bcl-2 was significantly reduced, and the expression levels of Bax and Caspase-3 were significantly increased in the ART group compared to the negative control saline group. There was no significant difference detected in p53 expression. The Bcl-2 level was negatively related to Bax and Caspase-3. The western blotting results showed IGF-IR downregulation. Conclusions： ART inhibits the growth of MCF-7 breast tumor cell xenografts in nude mice. The anti-tumor mechanism of ART for human breast carcinoma in nude mice might be correlated with the alteration of apoptosis related protein expression, which may further induce apoptosis and inhibit cell proliferation.     

ADENOVIRUS－MEDIATED P53 GENE TRANSFER INCREASES THE THERMOSENSITIVITY OF HUMAN GASTRIC CARCINOM ACELL LINES （IN VITRO AND IN VIVO）

Objective: To investigate the effect of adenovirus-mediated p53 (Adp53) transfer on thermosensitivity of human gastric carcinoma cell lines (BGC823). Methods: Two human gastric carcinoma cell lines with different p53 status, BGC823-wtp53 cell (abbreviate W) bearing the wilt-type p53 and BGC823-mutp53 cell (abbreviate M) bearing the mutant p53, were cultured with DMEM medium and were infected with Adp53 at a viral multiplicity of infection of 100 (1:100MOI) for 48h before heating. Cell cycle redistribution and apoptosis of two human gastric carcinoma cell lines in 24h at 37°C after heat treatment at 42°C for 2h or 43°C for 0.5h were analyzed by flow cytometry. Relative tumor volume growth curves were used in a nude mouse tumor model of the two cell lines following hyperthermia at 43 C for 0.5h after 48h intratumoral injection of 1×108 pfu of Adp53 to evaluate thermoenhancemet effectin vivo. Results:In vitro study showed that both W and M cells infected with Adp53 and treated with heating had strong arrest in G2 (after heating at 42°C for 2h, 34.0% of original population for W cells and 25.3% of original population for M cells) and produced obvious apoptotic response. The apoptosis rate showed 230% increased (for W cells) and 110% increase (for M cells) compared with heating only control.In vivo study showed that the growth of tumor of both W cells and M cells was significantly delayed by hyperthemia combining with Adp53 as compared to tumors receiving either treatment alone. Conclusion: This study demonstrated that Adp53 transfer increased cellular apoptosis and thermo- sensitivityin vitro and tumor thermosensitivityin vivo independent of cellular intrinsic p53 status. These results support the combined used of p53 gene therapy with hyperthermia in clinical trials. Foundation item: This work was supported by the National Natural Foundation of China (No. 39670234 ) Biography: ZHANG Shan-wen(1946–), male, professor, Department of Radiotherapy, Peking University School of Oncology, majors in radiation oncology and gene therapy.     

Adenovirus-mediated Ink4a/ARF gene transfer significantly suppressed the growth of pancreatic carcinoma cells

OBJECTIVES: To determine the effects of adenovirus-mediated transfer of p14(ARF) and p16(INK4a) on growth and apoptosis of human pancreatic carcinoma cell lines. RESULTs: Pancreatic carcinoma cell lines, PC-7, PANC-1 and MIA PaCa-2 (p14(ARF)-/- and p16(INK4a)-/-), were used. PC-7 (p53 wt) and MIA PaCa-2 (p53 mt) cells infected with recombinant adenovirus vector expressing p14(ARF) gene (Adp14) showed significant inhibition of cell growth compared with control vector in vitro and in vivo, whereas PANC-1 cells (p53 mt) did not show such effects. Those three cell lines exhibited growth retardation and senescence phenotype after infected with the adenovirus vector containing p16(INK4a) gene (Adp16) in vivo and in vitro. CONCLUSIONS: Adenovirus-mediated transfer of p14(ARF) and p16(INK4a) produces significant growth suppression of pancreatic carcinoma cells in vitro and in vivo. The effects of Adp14 partly depend on the status of p53 gene in those cells.     

Combined radiation and p53 gene therapy of malignant glioma cells

More than half of malignant gliomas reportedly have alterations in the p53 tumor suppressor gene. Because p53 plays a key role in the cellular response to DNA-damaging agents, we investigated the role of p53 gene therapy before ionizing radiation in cultured human glioma cells containing normal or mutated p53. Three established human glioma cell lines expressing the wild-type (U87 MG, p53wt) or mutant (A172 and U373 MG, p53mut) p53 gene were transduced by recombinant adenoviral vectors bearing human p53 (Adp53) and Escherichia coli beta-galactosidase genes (AdLacZ, control virus) before radiation (0-20 Gy). Changes in p53, p21, and Bax expression were studied by Western immunoblotting, whereas cell cycle alterations and apoptosis were investigated by flow cytometry and nuclear staining. Survival was assessed by clonogenic assays. Within 48 hours of Adp53 exposure, all three cell lines demonstrated p53 expression at a viral multiplicity of infection of 100. p21, which is a p53-inducible downstream effector gene, was overexpressed, and cells were arrested in the G1 phase. Bax expression, which is thought to play a role in p53-induced apoptosis, did not change with either radiation or Adp53. Apoptosis and survival after p53 gene therapy varied. U87 MG (p53wt) cells showed minimal apoptosis after Adp53, irradiation, or combined treatments. U373 MG (p53mut) cells underwent massive apoptosis and died within 48 hours of Adp53 treatment, independent of irradiation. Surprisingly, A172 (p53mut) cells demonstrated minimal apoptosis after Adp53 exposure; however, unlike U373 MG cells, apoptosis increased with radiation dose. Survival of all three cell lines was reduced dramatically after >10 Gy. Although Adp53 transduction significantly reduced the survival of U373 MG cells and inhibited A172 growth, it had no effect on the U87 MG cell line. Transduction with AdLacZ did not affect apoptosis or cell cycle progression and only minimally affected survival in all cell lines. We conclude that responses to p53 gene therapy are variable among gliomas and most likely depend upon both cellular p53 status and as yet ill-defined downstream pathways involving activation of cell cycle regulatory and apoptotic genes.     

Adenovirus-mediated expression of p53 or p21 in a papillary serous endometrial carcinoma cell line (SPEC-2) results in both growth inhibition and apoptotic cell death: potential application of gene therapy to endometrial cancer.

Papillary serous endometrial carcinoma is an aggressive tumor characterized by late-stage presentation, i.p. spread, and poor prognosis. It is histologically similar to serous papillary carcinoma of the ovary. Preclinical studies have shown that adenovirus-mediated expression of p53 in ovarian cancer cell lines causes growth inhibition and apoptosis in vitro and in vivo. Such studies provide the rationale for Phase I Adp53 gene therapy clinical trials in ovarian cancer. In the present study, we compared the efficacy of adenoviral vectors containing p53 (Adp53) or p21 (Adp21) in a papillary serous endometrial tumor cell line (SPEC-2) that contains mutated p53. Growth assays revealed that both Adp53 and Adp21 were efficacious in decreasing cell proliferation as assessed by anchorage-dependent and anchorage-independent growth assays. However, as compared with Adp53, the effects of Adp21 tended to be more transient and less marked. Strikingly, Adp21, but not Adp53, induced a G1 arrest in SPEC-2 endometrial adenocarcinoma cells. In contrast, as assessed by induction of hypodiploid peaks, free DNA ends detected by a terminal deoxynucleotidyl transferase-based assay, and annexin V positivity, p53 was more effective than p21 in inducing cell death by apoptosis. Compatible with the more efficient induction of apoptosis, Adp53, but not Adp21, induced a marked increase in expression of the preapoptotic molecule BAX without a concomitant change in expression of the antiapoptotic mediator Bcl-2. The differential effects of Adp53 and Adp21 on cell cycle progression and apoptosis may be related to the reversibility of p21-induced cell cycle arrest and the irreversibility of p53-induced apoptosis. Thus, at least in the papillary serous endometrial carcinoma cell line SPEC-2, Adp53 may be more effective than Adp21 as a gene therapeutic. Nevertheless, these preclinical studies suggest that papillary serous endometrial carcinoma is a potential target for p53- or p21-mediated gene therapy.     

抑癌基因p53对人胃癌细胞系放射敏感性的作用

目的评价野生型抑癌基因（正常）ｐ５３对人胃癌细胞系放射敏感性的控制作用。方法用流式细胞仪分析４Ｇｙ照射后８和２４小时４种不同ｐ５３状态的人胃癌细胞系细胞周期分布和凋亡的反应。以４Ｇｙ细胞存活份数和１０Ｇｙ照射后的肿瘤生长曲线比较４种细胞的放射敏感性。结果照射４Ｇｙ后８小时和２４小时的ｐ５３正常的ＢＧＣ８２３细胞出现强烈的Ｇ１期阻滞（分别占原细胞总数的６７．９％和６１．１％）,比无照射的该细胞Ｇ１期比例有显著的增高（Ｐ＜０．０５）,并出现明显的预示凋亡的亚Ｇ１峰（ＳｕｂＧ１）,凋亡细胞比例分别达１３．０％和１５．３％;同样条件下其他３种ｐ５３异常的细胞Ｇ１期比例没有显著的变化（Ｐ＞０．０５）,都没有出现亚Ｇ１峰,凋亡细胞比例均为０．０％。ｐ５３正常的ＢＧＣ８２３细胞４Ｇｙ的存活份数明显低于其它３种细胞（Ｐ＜０．０５）;且细胞移植肿瘤１０Ｇｙ照射后比其它３种的生长受到更明显抑制（Ｐ＜０．０５）。结论以上的结果证实了野生型ｐ５３基因促进了照射后肿瘤细胞的Ｇ１期阻滞和凋亡,从而明显地提高肿瘤细胞的放射敏感性。     

Up-regulation of the proapoptotic mediators Bax and Bak after adenovirus-mediated p53 gene transfer in lung cancer cells.

Overexpression of wild-type p53 in cancer cells by adenovirus-mediated p53 gene transfer can result in the induction of apoptosis. To identify the potential mediators of this p53-induced apoptosis, we examined apoptotic protein levels in human lung cancer cells after Adp53 gene transfer. We observed up-regulation of Bax and Bak protein levels 18-36 h after transduction with Adp53 in H1299, H358, and H322 lung cancer cells. Contrary to expected observations, no changes in Bcl-2 and Bcl-X(L) protein levels were observed. Morphological cell changes and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining showed evidence of apoptosis in all cell lines 48 h after transduction with Adp53. These results indicate that the induction of apoptosis by adenovirus-mediated p53 transfer may be mediated by the induction of proapoptotic mechanisms rather than suppression of antiapoptotic mechanisms.     

TGF-β1对人肝癌细胞系凋亡的调控作用研究

 目的　本研究旨在明确人肝癌细胞系中TGF β1的作用及其与凋亡的关系。 方法　本研究选用了 3种含有不同 p5 3基因状态的人肝癌细胞系 ,应用TUNEL技术对TGF β1诱导的肝癌细胞的凋亡进行了定量检测。结果　TGF β1仅能诱导HepG2细胞 (野生型p5 3)凋亡 ,这提示凋亡与 p5 3基因的表达具有明确的联系。结论　HepG2细胞系比Huh 7和Hep3B系细胞更易发生TGF β1诱导的凋亡 ,TGF β1通过p5 3依赖性途径诱导肝癌细胞系发生凋亡     

Potential of adenoviral p53 gene therapy and irradiation for the treatment of malignant gliomas

We investigated the combined effects of p53 gene transfer and irradiation and its still unclear interaction mechanism in human gliomas. Four human glioma cell lines expressing mutant type p53 (U373 and A172) and wild-type p53 (D54MG and EFC-2) were transfected by adenoviral vectors bearing p53 gene at 50 multiplicity of infection. Two days after transfection, cells were irradiated (3, 6, and 9 Gy). The cytotoxicity was evaluated by clonogenic assay. The quantitative analysis of apoptosis and cell cycle analysis were performed using flow cytometry. Irradiation combined with adenoviral p53 transfection significantly increased cytotoxicity, which was additive in cell lines with wild-type p53 and more than additive in cell lines with mutant p53. The combination of two modalities increased the apoptotic population by 14% in A172 cells and 20% in D54 MG cells, which were the sum of apoptosis from each modality. Adenoviral p53 transfection increased the G1 phase fraction and concomitant decrease of radioresistant S phase fraction in A172 and D54MG cells. Our study demonstrated that p53 gene transfer combined with irradiation increased absolute cytotoxicity in human glioma cells used in this experiment. The interaction mechanism for increased cytotoxicity involved, in part, increased apoptosis and change of cell cycle profile.     

Adenovirus-mediated N5 gene transfer inhibits tumor growth and metastasis of human carcinoma in nude mice

The therapeutic effectiveness of cancer therapy often relies on induction of apoptotic cell death. Gene-therapy-mediated induction of apoptosis, therefore, may provide an effective means to kill cancer cells. The N5 gene encodes a death-domain-containing protein (p84N5) that can trigger atypical apoptosis from within the nucleus, suggesting it may be a candidate for use as a gene therapy for cancer. In the present study, we test the potential utility of a recombinant adenovirus designed to express the N5 gene(AdN5) for the treatment of a variety of human cancers using in vitro and animal models. In vitro, adenoviral-mediated N5 gene transfer inhibits the growth of five different tumor cell lines, but not a normal diploid fibroblast cell line. Adenoviral-mediated N5 gene transfer also reduces the growth and metastasis of primary human tumors in subcutaneous and orthotopic xenograft mouse models. Reduction in tumor cell growth in vitro and in vivo correlates with increased expression of p84N5 and induction of apoptosis. The relative sensitivity of different human cancer cells to AdN5 or Adp53 varies, suggesting that AdN5 may be effective in tumors relatively resistant to p53 gene therapy. We conclude that N5 has potential utility for the gene therapy of cancer.     

Downregulation of XIAP expression induces apoptosis and enhances chemotherapeutic sensitivity in human gastric cancer cells

X-linked inhibitor of apoptosis (XIAP) is the most potent member of the inhibitor of apoptosis protein (IAP) gene family in terms of its ability to inhibit caspases and suppress apoptosis. Recent evidence has suggested that XIAP is a key determinant in chemoresistance of cancer cells. To explore a novel approach for ameliorating chemotherapy of gastric cancer, the antisense expression vector for the XIAP gene was constructed and transferred into gastric cancer cell lines, MKN-45 (wild-type p53) and MKN-28 (mutant-type p53). This transfer resulted in significant downregulation of XIAP expression, decreased in vitro cell viabilities, and induced apoptosis. In transferred cells, inactive caspase-3 precursors were cleaved into the active subunits (p20 and p17) during apoptosis induced by downregulation of XIAP. The inhibitory effects of cisplatin and mitomycin C on the growth of XIAP downregulated cancer cells were significantly enhanced. In addition, this process occurred only in wild-type p53 (MKN-45), but not in mutant-type p53 (MKN-28) gastric cancer cells. The data presented suggest that downregulation of XIAP via antisense RNA can lead to apoptosis of gastric cancer cells in vitro, correlating with cellular p53 status and activation of caspase-3. This finding could lead to a potential strategy for improving the efficiency of therapies for gastric cancer.