血管抑制素基因抑制结肠癌细胞增殖及肿瘤血管生成的研究

目的:研究血管抑制素基因体外对结肠癌细胞增殖的抑制及体内对肿瘤血管生成的抑制,探讨血管抑制素基因对结肠癌的抑制作用。方法:构建重组质粒pcDNA3.1( )／angio,用脂质体转染法将重组质粒、空白载体导入结肠癌细胞Colo205,培养细胞观察细胞生长,绘制细胞生长曲线,计算增殖抑制率,然后将pcDNA3.1( )／angio、pcDNA3.1( )／Colo205、Colo205分别接种至裸鼠右侧颈部皮下,观察肿瘤的生长,测量肿瘤体积,计算抑瘤率,免疫组化检测肿瘤组织中微血管密度(MVD)、血管内皮生长因子(VEGF)的表达。结果:体外pcDNA3.1( )／angio组细胞的生长速度略慢于pcDNA3.1( )／Colo205、Colo205组,但差异无统计学意义(P>0.05);体内pcDNA3.1( )／angio组细胞的致力显著降低,瘤体增长缓慢,抑瘤率较高(P<0.01),瘤体组织中MVD及VEGF的表达较低(P<0.05);pcDNA3.1( )／Colo205、Colo205两组之间的差异无统计学意义(P>0.05)。结论:在体外血管抑制素不直接影响结肠癌细胞Colo205的生物学特性,但在体内可强烈抑制肿瘤的生长,其机制可能是通过降低血管生成因子而抑制肿瘤的新生血管生成,发挥抑制肿瘤作用。     

ShRNA-mediated gene silencing of β-catenin inhibits growth of human colon cancer cells

AIM: To observe the gene silencing mediated by the specific shRNA targeted against β-catenin and its effect on cell proliferation and cycle distribution in the human colon cancer cell line Colo205.METHODS: Two shRNA plasmid vectors against β-catenin were constructed and transfected into Colo205 cells with LipofectamineTM2000. The down-regulations of β-catenin, c-myc and cyclinD1 expressions were detected by RT-PCR and western blot analysis. The cell proliferation inhibitions were determined by MTT assay and soft agar colony formation assay. The effect of these two β-catenin shRNAs on cell cycle distribution and apoptosis was examined by flow cytometry.RESULTS: These two shRNA vectors targeted against β-catenin efficiently suppressed the expression of β-catenin and its down stream genes, c-myc and cyclinD1. The expression inhibition rates were around 40%-50% either at the mRNA or at the protein level.The shRNA-mediated gene silencing of β-catenin resulted in significant inhibition of cell growth both on the culture plates and in the soft agar. Moreover, the cancer cells showed significant G0/G1 arrest and increased apoptosis at 72 h post transfection due to gene silencing.CONCLUSION: These specific shRNAs targeted against β-catenin could have a gene silencing effect and block the WNT signaling pathway. They could inhibit cell growth, increase apoptosis, and induce cell cycle arrest in Colo205 cells. ShRNA interference against β-catenin is of potential value in gene therapy of colon cancer.     

ShRNA-mediated gene silencing of β-catenin inhibits growt of human colon cancer cells

AIM: To observe the gene silencing mediated by the specific shRNA targeted against β-catenin and its effect on cell proliferation and cycle distribution in the human colon cancer cell line Colo205. METHODS: Two shRNA plasmid vectors against β-catenin were constructed and transfected into Colo205 cells with LipofectamineTM2000. The down-regulations of β-catenin, c-myc and cyclinD1 expressions were detected by RT-PCR and western blot analysis. The cell proliferation inhibitions were determined by MTT assay and soft agar colony formation assay. The effect of these two β-catenin shRNAs on cell cycle distribution and apoptosis was examined by flow cytometry. RESULTS: These two shRNA vectors targeted against β-catenin efficiently suppressed the expression of β-catenin and its down stream genes, c-myc and cyclinD1. The expression inhibition rates were around 40%-50% either at the mRNA or at the protein level. The shRNA-mediated gene silencing of β-catenin resulted in significant inhibition of cell growth both on the culture plates and in the soft agar. Moreover, the cancer cells showed significant G0/G1 arrest and increased apoptosis at 72 h post transfection due to gene silencing. CONCLUSION: These specific shRNAs targeted against β-catenin could have a gene silencing effect and block the WNT signaling pathway. They could inhibit cell growth, increase apoptosis, and induce cell cycle arrest in Colo205 cells. ShRNA interference against β-catenin is of potential value in gene therapy of colon cancer.     

Gastrin suppresses growth of CCK2 receptor expressing colon cancer cells by inducing apoptosis in vitro and in vivo

BACKGROUND & AIMS: The role of amidated gastrin17 (G17) and the gastrin/CCKB/CCK2 receptor in colorectal carcinogenesis is still a controversial issue. Here, we investigated the effect of G17 on proliferation and apoptosis of CCK2 receptor-expressing human colon cancer cell lines in vitro and in vivo. METHODS: Proliferation was determined by cell counting and cell cycle analysis. Apoptosis was analyzed by annexin V staining, TUNEL staining, caspase-3/7 assay, and JC1 (delta psi) assay. Signal-transduction pathways were analyzed by Western blotting and gel-shift and luciferase assays. An in vivo tumor model with subcutaneously inoculated colon cancer cells in SCID mice was used, and systemic hypergastrinemia was induced by omeprazole. RESULTS: In Colo320 cells stably transfected with the wild-type CCK2 receptor (Colo320wt) or in Lovo cells endogenously expressing CCK2 receptors, G17 treatment inhibited proliferation along with a G2/M cell cycle arrest. Furthermore, the administration of G17 significantly augmented apoptosis of CCK2 receptor-expressing cells. In contrast, G17 had no effect on proliferation and apoptosis in Colo320 cells stably transfected with a tumor-derived CCK2 receptor mutant (Colo320mut) or in cells lacking CCK2 receptor expression. Systemic hypergastrinemia in severe combined immunodeficiency (SCID) mice suppressed the growth of Colo320wt tumors accompanied by enhanced apoptosis as compared with untreated tumors. In contrast, omeprazole did not affect Colo320mut tumors reflecting a loss-of-function state of the CCK2(mut) receptor. This is supported by the observation that, in Colo320wt cells, but not in Colo320mut cells, G17 treatment induced the MAPK/ERK/AP-1 pathway and inhibited the activity of NF-kappaB. CONCLUSIONS: G17 exerts an antiproliferative and proapoptotic effect on human colon cancer cells expressing the wild-type CCK2 receptor. This supports the view that amidated gastrin prevents rather than promotes colorectal carcinogenesis.     

Upregulated CD133 expression in tumorigenesis of colon cancer cells

AIM: To analyze the upregulated CD133 expression in tumorigenesis of primary colon cancer cells. METHODS: Upregulated CD133 expression in tumorigenesis of colorectal cancer cell lines (Lovo, Colo205, Caco-2, HCT116 and SW620) was analyzed by flow cytometry. Human colon cancer tissue samples were stained with anti-human CD133. SW620 cells were sorted according to the CD133 expression level measured by fluorescence-activated cell sorting. Spheroids of colorectal cancer cells were cultured with the hanging dro...     

Murine monoclonal anti-idiotope antibody breaks unresponsiveness and induces a specific antibody response to human melanoma-associated proteoglycan antigen in cynomolgus monkeys.

The mouse monoclonal antibody MEM136 (mAb1) is directed against an epitope on human melanoma-associated proteoglycan antigen (MPG). This epitope is also present on various normal human and subhuman tissues. A monoclonal murine anti-idiotope (anti-Id) antibody (mAb2), designated I-Mel-2, was generated against MEM136 and used as a surrogate antigen for the MPG molecule. I-Mel-2 was tested in cynomolgus monkeys (Macaca fascicularis) for its ability to induce anti-MPG humoral responses. All monkeys immunized with Ab2 developed specific anti-anti-idiotype (Ab3) responses that were capable of inhibiting binding of Ab2 to Ab1. Furthermore, I-Mel-2 immune monkey serum contained anti-MPG antibodies (Ab1') that bound to MPG-positive but not to MPG-negative melanoma cell lines. Monkeys immunized with Colo38 melanoma cells (membrane-bound MPG antigen) did not contain anti-MPG antibodies that inhibited the binding of two distinct anti-MPG mAb 125I-labeled MEM136 or 125I-labeled 225.28 to Colo38 cells. The induction of anti-MPG responses in monkeys did not cause any apparent side effects in animals, despite the fact that the MPG antigen is expressed by many normal tissues. The affinity-purified, I-Mel-2 idiotype-specific, Ab3 immunoprecipitated MPG antigen from melanoma cells. Furthermore, the I-Mel-2-induced Ab3 inhibited melanoma cell invasion in an in vitro assay, implying that these antibodies have biological significance.     

Cyclooxygenase-2 Inhibition Prevents Migration of Colorectal Cancer Cells to Extracellular Matrix by Down-Regulation of Matrix Metalloproteinase-2 Expression

Purpose

Matrix metalloproteinases-2 hydrolyses gelatins and collagens. It has many biologic functions, including cancer cells invasion. Overexpression of cyclooxygenase-2 is known to be involved in colorectal carcinogenesis, although the mechanism is unclear. Up-regulation of matrix metalloproteinases-2 expression may be one of the mechanisms, which explains how cyclooxygenase-2 expression promotes migration of colorectal cancer cells to extracellular matrix.

Methods

Colorectal cancer cell lines HT29, CaCO2, and Colo205 were used. By using flow cytometry, their cyclooxygenase-2 expression was determined. These cell lines were modulated with NS398, a selective cyclooxygenase-2-inhibitor, and prostaglandin-E2. Western blot and enzyme-linked inmmunosorbent assay were used to determine these cells’ matrix metalloproteinases-2 expression. These cell lines’ ability to migrate into extracellular matrix was determined by Matrigel® (Millipore, Watford, UK) Invasion Chamber.

Results

HT29 expressed more cyclooxygenase-2 than CaCO2. Cyclooxygenase-2 was not detected in Colo205. Matrix metalloproteinases-2 expression is highest in HT29 and least in Colo205. Cyclooxygenase-2 inhibition by NS398 showed decreased matrix metalloproteinases-2 expression in HT29 and CaCO2, but not Colo205, reversible with prostaglandin-E2. Prostaglandin-E2 was shown to up-regulate matrix metalloproteinases-2 expression in all cell lines. Matrigel® Invasion Chamber demonstrated that many more HT29 cells migrate across the membrane than CaCO2 and Colo205, and cyclooxygenase-2 inhibition reduced cellular migration in the cyclooxygenase-2–positive cell lines. Prostaglandin-E2 promoted migration in all cell lines.

Conclusions

There is a positive relationship between cyclooxygenase-2 and matrix metalloproteinases-2 expression. The latter is modulated by prostaglandin-E2 in all cell lines and NS398 in cyclooxygenase-2–positive cells. Such modulation has a knock-on effect to the cells’ ability to invade into extracellular matrix. Cyclooxygenase-2 and matrix metalloproteinases-2 expression are potential therapeutic targets into prevention of colorectal cancer metastasis.

     

Molecular mechanisms of denbinobin-induced anti-tumorigenesis effect in colon cancer cells

AIM: To explore both the in vitro and in vivo effects of denbinobin against colon cancer cells and clarify its underlying signal pathways. METHODS: We used COLO 205 cancer cell lines and nude mice xenograft model to study the in vitro and in vivo anti-cancer effects of denbinobin. RESULTS: Denbinobin at concentration of 10-20 μmol/L dose-dependently suppressed COLO 205 cell proliferation by MTT test. Flow cytometry analysis and DNA fragmentation assay revealed that 10-20 μmol/L denbinobin treatment induced COLO 205 cells apoptosis. Western blot analysis showed that caspases 3,8,9 and Bid protein were activated by denbinobin treatment to COLO 205 cells accompanied with cytochrome c and apoptosis-inducing factor (AIF) translocation. Pretreatment of MEK 1 inhibitor (U10126), but not p38 inhibitor (SB203580) and JNK inhibitor (SP600125), reversed denbinobin-induced caspase 8, 9 and Bid activation in COLO 205 cells suggesting that extracellular signal-regulated kinase were involved in the denbinobin-induced apoptosis in COLO 205 cells. Significant regression of tumor up to 68% was further demonstrated in vivo by treating nude mice bearing COLO 205 tumor xenografts with denbinobin 50 mg/kg intraperitoneally. CONCLUSION: Our findings suggest that denbinobin could inhibit colon cancer growth both in vitro and in vivo. Activation of extrinsic and intrinsic apoptotic pathways and AIF were involved in the denbinobin-induced COLO 205 cell apoptosis.     

The combined effect of interferon and 5-FU on tumor-cell metastasis in the nude mouse

In searching for a suitable animal model system to study colorectal tumor-cell metastasis, the method of injecting tumor cells directly into the spleen of athymic nude mice was explored. The cells used in this study consisted of the Colo 205 cell line, isolated and established from the ascitic fluid of a patient with adenocarcinoma of the colon. In spite of showing tumorigenicity in nude mice after subcutaneous injections, anchorage-independent clonal growth in soft agar, and invasion in the chick embryo skin, the Colo 205 cells failed to metastasize to the lung or liver after intrasplenic injections. The effects of interferon, and interferon in combination with 5-fluorouracil (5-FU), on tumor formation in the spleen, were studied. The combined interferon- and 5-Fu-treated animals displayed a significant difference from the controls in the generation of spleen tumors. This combination may possess potentially useful applications in the treatment of solid tumors such as those in the colon and rectum. Read at the meeting of the American Society of Colon and Rectal Surgeons, Anaheim, California, June 12 to 17, 1988.     

A novel anti-CD146 monoclonal antibody,AA98, inhibits angiogenesis and tumor growth

The goal of our study was to raise monoclonal antibodies (mAbs) against endothelial cell-surface proteins specific for tumor vasculature. Here, we describe the generation and intensive characterization of mAb AA98, including its functional properties and its antigen identification. In our study, an enhanced mAb AA98 immunoreactivity was observed on stimulated human umbilical vein endothelial cells (HUVECs). In addition, mAb AA98 showed remarkably restricted immunoreactivity against intratumoral neovasculature compared with blood vessels of normal tissues. We identified the AA98 antigen as human CD146, an adhesion molecule belonging to the immunoglobulin superfamily. Data from in vitro experiments imply structural and signaling functions for endothelial CD146; however, the role of CD146 in vivo is largely unknown. Here, we show that mAb AA98 displays antiangiogenic properties in vitro and in vivo. Proliferation and migration of HUVECs were inhibited by mAb AA98 as was angiogenesis in chicken chorioallantoic membrane (CAM) assays and tumor growth in 3 xenografted human tumor models in mice. Our data provide new insights into the function of CD146 on endothelial cells, validate CD146 as a novel target for antiangiogenic agents, and demonstrate that mAb AA98 has potential as a diagnostic and therapeutic agent in vascular and cancer biology.     

纤维连接蛋白对人结肠癌细胞侵袭力的影响

目的研究纤维连接蛋白（fibronectin，FN）对人结肠癌细胞侵袭力的影响，并探讨其中的信号传导机制。方法以递增浓度的FN刺激结肠癌细胞株Colo320，以免疫沉淀和蛋白质印迹法检测结肠癌细胞内黏着斑激酶（focal adhesion kinase，FAK）第397位酪氨酸（tyr-397）磷酸化的状况．以改良Boyden小室法检测相应的细胞侵袭力变化。设计反义寡核苷酸阻断FAK蛋白质表达，再次观察接受FN刺激后．结肠癌细胞内FAK tyr-397磷酸化状况及细胞侵袭力的改变。结果FN能够促进Colo320 FAK tyr-397磷酸化，在一定范围内具有剂量依赖性。FN浓度达10nmol／L时．此作用最显著，继续增加FN浓度．FAK tyr-397磷酸化不再呈现继续增强趋势．当浓度达到100nmol／L时，磷酸化程度反而有所下降；FN可以增强细胞侵袭力，同样在一定范围内具有剂量依赖性；反义寡核苷酸干预后．结肠癌细胞内FAK tyr-397磷酸化及细胞侵袭力均有显著降低（P〈0.01）。结论FN可以有效增强结肠癌细胞的侵袭力，其作用是通过FN—FAK信号通路实现的，FAK的活性形式是其酪氨酸位点的磷酸化．阻断FAK的表达町以减弱FN促进细胞侵袭的作用。     

Induction of apoptosis by norcantharidin in human colorectal carcinoma cell lines: involvement of the CD95 receptor/ligand

PURPOSE: Cantharidin, a natural toxin, is the active substance of mylabris and has antitumor effects in man. Norcantharidin, the demethylated analogue of cantharidin, has been used in the treatment of patients with primary hepatoma and those with leukopenia in China. The present study was designed to investigate whether norcantharidin exerts cytotoxic activity against colorectal cancer cells by inducing apoptosis and to examine the possible mechanism in the phenomenon. METHODS: Inhibition of proliferation of norcantharidin on Colo205, HT-29, and SW480 colorectal cancer cells was determined by the trypan blue dye exclusion test. Apoptosis of norcantharidin-treated cells was determined by morphological analysis, agarose gel DNA electrophoresis, and quantitated by flow cytometry after staining with propidium iodide. Cell cycle and the cell surface expression of the CD95/CD95 ligand were evaluated by flow cytometry. Caspase 8-like protease and protein phosphatase 1 and 2A activities were also analyzed. RESULTS: Treatment with norcantharidin of colorectal cancer cells not only inhibited cell proliferation, but also induced apoptosis. Norcantharidin induced apoptosis mainly in two phases: rapid apoptosis in S-phase cells and delayed apoptosis in G2/M arrested cells. Treatment with norcantharidin resulted in an upregulation of the CD95 receptor and CD95 ligand on the cell surface. Furthermore, stimulation with anti-CD95 monoclonal antibody (mAb) resulted in further induction of apoptosis after treatment with norcantharidin. In addition, the apoptosis-inducing effect of norcantharidin was almost completely inhibited by anti-CD95 ligand mAb. Norcantharidin-treated cells showed the activation of caspase 8. Both zVAD-FMK (a broad range caspase inhibitor) and IETD-FMK (a caspase-8 inhibitor) showed apparent inhibition of the apoptosis-inducing effect. Norcantharidin did not show an inhibitory effect on protein phosphatase. CONCLUSIONS: These results suggest that norcantharidin triggers apoptosis in colorectal cancer cell lines via the activation of the CD95 receptor/ligand system, and that this agent may be useful for developing new therapeutic regimens for the treatment of colorectal carcinoma.     

From the Cover: Suppression of human prostate tumor growth by a unique prostate-specific monoclonal antibody F77 targeting a glycolipid marker

In our effort to find diagnostic markers and to develop therapeutic approaches for prostate cancer, we have identified an mAb that is capable of binding to a cell surface antigen specifically expressed on both androgen-dependent and androgen-independent prostate cancer cells. Immunohistological studies revealed that this mAb, called F77, stained 112 of 116 primary and 29 of 34 metastatic human prostate cancer specimens. Although the mAb F77 alone directly promotes prostate cancer cell death, it also mediates complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity. In addition, mAb F77 can significantly inhibit androgen-independent PC3 and Du145 tumor growth in nude mice. Antigen characterization revealed that mAb F77 recognizes a very small molecular species with glycolipid properties. F77 antigen is concentrated in the lipid-raft microdomains, which serve as platforms for the assembly of associating protein complexes. Thus, the present study indicates that mAb F77 defines a unique prostate cancer marker and shows promising potential for diagnosis and treatment of prostate cancer, especially for androgen-independent metastatic prostate cancer.     

Salecan-Clay Based Polymer Nanocomposites for Chemotherapeutic Drug Delivery Systems; Characterization and In Vitro Biocompatibility Studies

Salecan is a microbial polysaccharide suitable to obtain hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility properties. In this work, Salecan of different concentrations was introduced into polymethacrylic acid (PMAA) in the presence of clay to form novel semi synthetic hydrogel nanocomposites systems and loaded afterwards with doxorubicin (DOX). The physical–chemical characteristics of the nanocomposites systems and their effect on the viability, and morphology of MDBK (Madin–Darby bovine kidney), HT-29 human colorectal adenocarcinoma and Colo 205 human colon adenocarcinoma cell lines were investigated. DOX release from the nanocomposite systems, cell up-take and subsequent effect on cell proliferation was also analyzed. It was found that Salecan concentration determined the swelling behavior, structural parameters and morphological features of the nanocomposite systems. The hydrogen bonds strongly influenced the formation of PMAA–Salecan–clay systems, each component bringing its own contribution, thus demonstrating the achievement of an advanced crosslinked network and a more compacted hydrogel nanocomposite morphology. All the synthesized nanocomposites had negligible toxicity to normal MDBK cells and chemoresistent HT-29 cell line, whereas in the case of Colo 205 cells a decrease by 40% of the cell viability was obtained for the sample containing the highest amount of Salecan. This effect was correlated with the lowest pore size distribution leading to highest available specific surface area and entrapped amount of DOX which was further released from the nanocomposite sample. Corroborating all the data it can be suggested that the synthesized nanocomposites with Salecan and clay could be good candidates as vehicles for chemotherapeutic agents.     

Antitumor activity of anti-type IV collagenase monoclonal antibody and its lidamycin conjugate against colon carcinoma

AIM: Type Ⅳ collagenase including MMP-2 and-9 plays an important role in cancer cell invasion and metastasis and is an attractive target for mAb-directed therapy. The immunoreactivity of mAb 3G11, a mAb directed against type Ⅳ collagenase in human colorectal carcinomas, was studied by immuno-histochemical (IHC) staining. mAb 3G11 was conjugated to an antitumor antibiotic lidamycin (LDM). The antitumor activity of 3G11-LDM conjugate against colon carcinoma was investigated in mice. METHODS: ELISA, gelatin zymography, and Western blot assay were used for the biological characterization of mAb 3G11. The immunoreactivity of mAb 3G11 with human colorectal carcinomas was detected by IHC staining. The cytotoxicity of LDM and 3G11-LDM conjugate to human colon carcinoma HT-29 cells was examined by clonogenic assay and MTT assay. The therapeutic effect of conjugate 3G11-LDM was evaluated with colon carcinoma 26 in mice. RESULTS: As shown in ELISA, mAb 3G11 reacted specifically with type Ⅳ collagenase, while 3G11-LDM conjugate also recognized specifically its respective antigen. In IHC assay, mAb 3G11 showed positive immunoreactivity in most cases of colorectal carcinoma, and negative immunoreactivity in the adjacent non-malignant tissues. By gelatin zymography, the inhibition effect of mAb 3G11 on the secretion activity of type Ⅳ collagenase was proved. In terms of IC_(50) values in MTT assay, the cytotoxicity of LDM to human colon carcinoma HT-29 cells was 10000-fold more potent than that of mitomycin C (MMC) and adriamycin (ADM). 3G11-LDM conjugate also displayed extremely potent cytotoxicity to human colon carcinoma HT-29 cells with an IC_(50) value of 5.6x10~(-19) mol/L. 3G11-LDM conjugate at the doses of 0.05 and 0.1 mg/kg inhibited the growth of colon carcinoma 26 in mice by 70.3 and 81.2%, respectively. CONCLUSION: mAb 3G11 is immunoreactive with human colorectal carcinoma and its conjugate with LDM is highly effective against colon carcinoma in mice.     

Antitumor activity of anti-type Ⅳcollagenase monoclonal antibody and its lidamycin conjugate against colon carcinoma

AIM: Type Ⅳ collagenase including MMP-2 and -9 plays an important role in cancer cell invasion and metastasis and is an attractive target for mAb-directed therapy. The immunoreactivity of mAb 3G11, a mAb directed against type Ⅳ collagenase in human colorectal carcinomas, was studied by immuno-histochemical (IHC) staining. mAb 3G11 was conjugated to an antitumor antibiotic lidamycin (LDM). The antitumor activity of 3G11-LDM conjugate against colon carcinoma was investigated in mice.METHODS: ELISA, gelatin zymography, and Western blot assay were used for the biological characterization of mAb 3G11. The immunoreactivity of mAb 3G11 with human colorectal carcinomas was detected by IHC staining. The cytotoxicity of LDM and 3G11-LDM conjugate to human colon carcinoma HT-29 cells was examined by clonogenic assay and MTT assay. The therapeutic effect of conjugate 3G11-LDM was evaluated with colon carcinoma 26 in mice.RESULTS: As shown in ELISA, mAb 3G11 reacted specifically with type Ⅳ collagenase, while 3G11-LDM conjugate also recognized specifically its respective antigen. In IHC assay,mAb 3G11 showed positive immunoreactivity in most cases of colorectal carcinoma, and negative immunoreactivity in the adjacent non-malignant tissues. By gelatin zymography,the inhibition effect of mAb 3G11 on the secretion activity of type Ⅳ collagenase was proved. In terms of IC50 values in MTT assay, the cytotoxicity of LDM to human colon carcinoma HT-29 cells was 10 000-fold more potent than that of mitomycin C (MMC) and adriamycin (ADM). 3G11-LDM conjugate also displayed extremely potent cytotoxicity to human colon carcinoma HT-29 cells with an ICs0 value of 5.6×10-19 mol/L. 3G11-LDM conjugate at the doses of 0.05 and 0.1 mg/kg inhibited the growth of colon carcinoma 26 in mice by 70.3 and 81.2%, respectively.CONCLUSION: mAb 3G11 is immunoreactive with human colorectal carcinoma and its conjugate with LDM is highly effective against colon carcinoma in mice.     

XAF1基因与p53基因在结直肠肿瘤中的表达研究

目的观察两个相邻位置的抑癌基因XIAP相关因子1(XAF1)与p53基因在结直肠肿瘤中的表达。方法选取结肠癌细胞株Colo205、Colo320、LoVo、SW1116为体外研究对象,另取41例结直肠癌、28例结直肠腺瘤/息肉以及31例正常人结肠黏膜为体内研究对象。应用逆转录聚合酶链反应检测XAF1mRNA与p53mRNA在体内外的表达,应用免疫组化法检测P53蛋白在结直肠组织中的表达。结果4种细胞株中XAF1表达均较为低下,p53mRNA表达均较高。结直肠肿瘤组织中的XAF1mRNA表达显著低于正常组织(P<0.01),结直肠癌中的表达又显著低于良性肿瘤(P<0.05)。结直肠肿瘤组织中的p53mRNA表达显著高于正常组织(P<0.01),但在良、恶性肿瘤中的表达差异无统计学意义(P<0.05)。P53蛋白在正常组织中未见表达,良、恶性肿瘤组的组织P53蛋白表达之间差异无统计学意义(P>0.05)。结论XAF1基因在结直肠肿瘤中表达降低,且结直肠癌XAF1mRNA表达显著低于良性肿瘤,可作为判断良、恶性肿瘤的鉴别指标。     

Deguelin, an Akt Inhibitor, Down-Regulates NF-κB Signaling and Induces Apoptosis in Colon Cancer Cells and Inhibits Tumor Growth in Mice

Background

Deguelin, a naturally occurring rotenoid, is known to be an Akt inhibitor and to have an anti-tumor effect on several cancers.

Aims

This study was performed to elucidate the effect of deguelin on apoptotic pathways related to NF-κB signaling in colon cancer cells and on the anti-tumor effect in colon cancer xenograft mice.

Methods

We studied COLO 205 and HCT116 cells in the presence or absence of deguelin. NF-κB signaling was examined by real-time RT-PCR for interleukin (IL)-8, by Western blotting for IκB phosphorylation/degradation, and by the electrophoretic mobility shift assay. Cell death was determined by the MTT assay, and apoptosis by Annexin V-FITC staining and caspase-3 activity. We also assessed the expression of antiapoptotic and proapoptotic factors by use of RT-PCR. In colon cancer xenograft mice, we evaluated the effect of deguelin on inoculated tumor growth, and apoptotic index was measured by the in vivo TUNEL assay.

Results

Deguelin significantly inhibited IL-8 gene expression, IκB phosphorylation/degradation, and DNA binding activity of NF-κB in colon cancer cells. Deguelin induced cell death and apoptosis in colon cancer cells in a dose and time-dependent manner. Deguelin down-regulated expression of NF-κB-mediated antiapoptotic factors such as cFLIP, Bcl-2, and Bcl-X_L. In the colon cancer xenograft model, the volume of the tumor treated with deguelin was significantly lower than that of the control, and the apoptotic index for deguelin-treated mice was much higher.

Conclusion

Deguelin might be a potential therapeutic agent for treatment of colorectal cancer.