Beta-escin inhibits colonic aberrant crypt foci formation in rats and regulates the cell cycle growth by inducing p21(waf1/cip1) in colon cancer cells

Extracts of Aesculus hippocastanum (horse chestnut) seed have been used in the treatment of chronic venous insufficiency, edema, and hemorrhoids. Most of the beneficial effects of horse chestnut are attributed to its principal component beta-escin or aescin. Recent studies suggest that beta-escin may possess anti-inflammatory, anti-hyaluronidase, and anti-histamine properties. We have evaluated the chemopreventive efficacy of dietary beta-escin on azoxymethane-induced colonic aberrant crypt foci (ACF). In addition, we analyzed the cell growth inhibitory effects and the induction of apoptosis in HT-29 human colon cancer cell line. To evaluate the inhibitory properties of beta-escin on colonic ACF, 7-week-old male F344 rats were fed experimental diets containing 0%, 0.025%, or 0.05% beta-escin. After 1 week, the rats received s.c. injections of azoxymethane (15 mg/kg body weight, once weekly for 2 weeks) or an equal volume of normal saline (vehicle). Rats were continued on respective experimental diets and sacrificed 8 weeks after the azoxymethane treatment. Colons were evaluated histopathologically for ACF. Administration of dietary 0.025% and 0.05% beta-escin significantly suppressed total colonic ACF formation up to approximately 40% (P < 0.001) and approximately 50% (P < 0.0001), respectively, when compared with control diet group. Importantly, rats fed beta-escin showed dose-dependent inhibition (approximately 49% to 65%, P < 0.0001) of foci containing four or more aberrant crypts. To understand the growth inhibitory effects, HT-29 human colon carcinoma cell lines were treated with various concentrations of beta-escin and analyzed by flow cytometry for apoptosis and cell cycle progression. Beta-escin treatment in HT-29 cells induced growth arrest at the G1-S phase, which was associated with the induction of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1), and this correlated with reduced phosphorylation of retinoblastoma protein. Results also indicate that beta-escin inhibited growth of colon cancer cells with either wild-type or mutant p53. This novel feature of beta-escin, a triterpene saponin, may be a useful candidate agent for colon cancer chemoprevention and treatment.     

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.     

Nitric oxide-releasing aspirin and indomethacin are potent inhibitors against colon cancer in azoxymethane-treated rats: effects on molecular targets

Nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NO-NSAID) are promising chemoprevention agents; unlike conventional NSAIDs, they seem free of appreciable adverse effects, while they retain beneficial activities of their parent compounds. Their effect on colon carcinogenesis using carcinoma formation as an end point is unknown. We assessed the chemopreventive properties of NO-indomethacin (NCX 530) and NO-aspirin (NCX 4016) against azoxymethane-induced colon cancer. Seven-week-old male F344 rats were fed control diet, and 1 week later, rats received two weekly s.c. injections of azoxymethane (15 mg/kg body weight). Two weeks after azoxymethane treatment, rats (48 per group) were fed experimental diets containing NO-indomethacin (0, 40, or 80 ppm), or NO-aspirin (1,500 or 3,000 ppm), representing 40% and 80% of the maximum tolerated dose. All rats were killed 48 weeks after azoxymethane treatment and assessed for colon tumor efficacy and molecular changes in colonic tumors and normally appearing colonic mucosa of different dietary groups. Our results suggest that NO-indomethacin at 40 and 80 ppm and NO-aspirin at 3,000 ppm significantly suppressed both tumor incidence (P < 0.01) and multiplicity (P < 0.001). The degree of inhibition was more pronounced with NO-indomethacin at both dose levels (72% and 76% inhibition) than with NO-aspirin (43% and 67%). NO-indomethacin at 40 and 80 ppm and NO-aspirin at 3,000 ppm significantly inhibited the colon tumors' (P < 0.01 to P < 0.001) total cyclooxygenase (COX), including COX-2 activity (52-75% inhibition) and formation of prostaglandin E2 (PGE2), PGF2alpha, and 6-keto-PGF1alpha, and TxB2 from arachidonic acid (53-77% inhibition). Nitric oxide synthase 2 (NOS-2) activity and beta-catenin expression were suppressed in animals given NO-NSAID. In colonic crypts and tumors of animals fed these two NO-NSAIDs, there was a significant decrease in proliferating cell nuclear antigen labeling when compared with animals fed the control diet. The results of this study provide strong evidence that NO-NSAIDs possess strong inhibitory effect against colon carcinogenesis; their effect is associated with suppression of COX and NOS-2 activities and beta-catenin levels in colon tumors. These results pave the way for the rational design of human clinical trials.     

Antioxidative and antiproliferative effects of astaxanthin during the initiation stages of 1,2-dimethyl hydrazine-induced experimental colon carcinogenesis

Colon cancer is one of the major causes of cancer mortality worldwide. Several carotenoids with antioxidant properties are reported for their chemopreventive nature. In this study, we have evaluated the chemopreventive efficacy of astaxanthin on lipid peroxidation, antioxidant status, total number of aberrant crypt foci (ACF), and cell proliferation in 1,2 dimethylhydrazine (DMH)-induced colon carcinogenesis using a rat model. DMH was induced subcutaneously at a dosage of 40 mg/kg body weight, twice a week for 2 weeks. Astaxanthin was administered before and after the DMH induction, orally at a concentration of 15 mg/kg body weight throughout the experimental period. At the end of 16 weeks, pre-treatment with astaxanthin markedly reduced the degree of histological lesions, ACF development and also lowered the number of argyrophilic nucleolar organizer regions. Our results also showed the decreased levels of colon enzymic and non-enzymic antioxidants and increased levels of lipid peroxidation marker levels in DMH-induced rats, which were significantly reversed on astaxanthin administration. In conclusion, the results of this study suggest that astaxanthin has an affirmative and beneficial effect against chemically induced colonic pre-neoplastic progression in rats induced by DMH.     

青蒿琥酯对结肠癌HCT116细胞间黏附分子蛋白表达的影响

目的：研究青蒿琥酯对结肠癌细胞锚着不依赖性增殖及其细胞间黏附分子-1（intercellular adhesion molecule-1，ICAM-1）基因蛋白表达的影响。方法：以人结肠癌细胞株HCT116为模型，以软琼脂集落培养试验检测青蒿琥酯对肿瘤细胞的增殖抑制效应；Western blot方法检测青蒿琥酯作用前后细胞ICAM-1蛋白表达的变化。结果：青蒿琥酯能有效地抑制结肠癌细胞HCT116的恶性增殖，且呈剂量依赖性。青蒿琥酯能有效地抑制ICAM-1基因蛋白表达，作用呈时间和浓度依赖性。结论：青蒿琥酯可明显抑制结肠癌HCT116细胞增殖，可能与下调ICAM-1表达有关。     

RNAi沉默STAT3基因对结肠癌HCT116细胞侵袭的调控

目的:观察RNA干扰沉默STAT3基因对结肠癌细胞侵袭的影响,并探讨其可能机制。方法:应用STAT3小干扰RNA(small interfering RNA,siRNA)转染处理人结肠癌细胞系HCT116后,采用RT-PCR检测STAT3 mRNA表达,软琼脂集落培养试验检测锚着不依赖性增殖,Boyden小室模型试验检测癌细胞的侵袭性,琼脂糖凝胶电泳和TUNEL检测癌细胞失巢凋亡。结果:STAT3 siRNA可有效抑制结肠癌细胞集落生长和侵袭能力,且与浓度相关。琼脂糖凝胶电泳和TUNEL结果显示,STAT3 siRNA转染可诱导结肠癌细胞失巢凋亡,且与浓度相关。结论:STAT3 siRNA可抑制结肠癌细胞的恶性侵袭,其机制与诱导失巢凋亡有关。     

Differential antiproliferative mechanisms of novel derivative of benzimidazo[1,2-alpha]quinoline in colon cancer cells depending on their p53 status

In the present article, we describe a mechanistic study of a novel derivative of N-amidino-substituted benzimidazo[1,2-alpha]quinoline in two human colorectal cancer cell lines differing in p53 gene status. We used a proteomic approach based on two-dimensional gel electrophoresis coupled with mass spectrometry to complement the results obtained by common molecular biology methods for analyzing cell proliferation, cell cycle, and apoptosis. Tested quinoline derivative inhibited colon cancer cell growth, whereby p53 gene status seemed to be critical for its differential response patterns. DNA damage and oxidative stress are likely to be the common triggers of molecular events underlying its antiproliferative effects. In HCT 116 (wild-type p53), this compound induced a p53-dependent response resulting in accumulation of the G(1)- and S-phase cells and induction of apoptosis via both caspase-3-dependent and caspase-independent pathways. Quinoline derivative triggered transient, p53-independent G(2)-M arrest in mutant p53 cells (SW620) and succeeding mitotic transition, whereby these cells underwent cell death probably due to aberrant mitosis (mitotic catastrophe). Proteomic approach used in this study proved to be a valuable tool for investigating cancer cell response to newly synthesized compound, as it specifically unraveled some molecular changes that would not have been otherwise detected (e.g., up-regulation of the p53-dependent chemotherapeutic response marker maspin in HCT 116 and impairment in ribosome biogenesis in SW620). Finally, antiproliferative effects of tested quinoline derivative on SW620 cells strongly support its possible role as an antimetastatic agent and encourage further in vivo studies on the chemotherapeutic potential of this compound against colorectal carcinoma.     

Gab2对结肠癌细胞细胞外黏附作用的影响

;目的探讨Gab2对结肠癌细胞外黏附作用的影响。方法选取SW620和HCT116两种结肠癌细胞系,建立Gab2表达降低和Gab2表达升高的稳定细胞株。将实验NOD/SCID小鼠分为3组,每组10只。(1)对照组;接种scr/MGC803体结肠癌细胞;(2)Gab2降低组;接种Gab2降低的siGab2/MGC803结肠癌细胞;(3)Gab2升高组;接种Gab2升高的Gab2/MGC803结肠癌细胞。检测细胞迁移能力,测量肿瘤的大小和侵袭范围及细胞凋亡情况。结果处理后3组细胞迁移数计算结果显示,Gab2降低组的细胞迁移数显著低于Gab2升高组和对照组(P<0.05)。各组NOD/SCID小鼠均在接种40 d后处死,比较接种前与接种后小鼠体质量,Gab2降低组显著低于Gab2升高组、对照组,对照组低于Gab2升高组。测量瘤体积,Gab2升高组高于Gab2降低组、对照组。Gab2降低组瘤体积抑制率显著高于对照组(P<0.05)。相关分析发现,MMP-2、MMP-9蛋白的表达与Gab2蛋白表达呈正相关。结论 Gab2可有效调控体外细胞迁移数,显著抑制小鼠结肠癌细胞侵袭及转移,通过调节MMP-2、MMP-9蛋白表达,从而抑制结肠癌生长及转移。     

Transcriptome analysis reveals GA induced apoptosis in HCT116 human colon cancer cells through calcium and p53 signal pathways

Gallic acid (GA) is a polyphenol widely found in numerous fruits and vegetables that has been reported to exert anticancer effects, including apoptosis, against cancer cell lines. However, little is known about the induction of apoptotic effects and the underlying mechanism. We used RNA-seq to examine differentially expressed genes in human colon cancer HCT116 cells after 12 h and 24 h exposure to GA. A total of 792 and 911 genes with known functions showed significantly different expression levels in 12 h and 24 h GA-treated HCT116 cells, respectively. KEGG enrichment analysis showed that the identified genes were involved in pathways such as cholinergic synapse, circadian entrainment, calcium signal processing and transport, arachidonic acid metabolism and the p53 signal pathway. Real-time quantitative PCR was used to validate the reliability of the results obtained by RNA-seq. The results of this study indicate that GA triggers apoptosis in HCT116 cells through obstructing the growth of cells in the early phase treatment by down-regulation of calcium channels and then up-regulation of the intrinsic p53 signal pathway through activation of apoptosis caspases, finally leading to the mitochondrial apoptosis pathway.

Gallic acid (GA) is a polyphenol widely found in plants that induced apoptosis in human colon cancer cells through calcium and p53 signal pathways.     

Colon cancer chemoprevention by a novel NO chimera that shows anti-inflammatory and antiproliferative activity in vitro and in vivo

Chemopreventive agents in colorectal cancer possess either antiproliferative or anti-inflammatory actions. Nonsteroidal anti-inflammatory drugs (NSAID) and cyclooxygenase-2 inhibitors have shown promise, but are compromised by side effects. Nitric oxide donor NSAIDs are organic nitrates conjugated via a labile linker to an NSAID, originally designed for use in pain relief, that have shown efficacy in colorectal cancer chemoprevention. The NO chimera, GT-094, is a novel nitrate containing an NSAID and disulfide pharmacophores, a lead compound for the design of agents specifically for colorectal cancer. GT-094 is the first nitrate reported to reduce aberrant crypt foci (by 45%) when administered after carcinogen in the standard azoxymethane rat model of colorectal cancer. Analysis of proximal and distal colon tissue from 8- and 28-week rat/azoxymethane studies showed that GT-094 treatment reduced colon crypt proliferation by 30% to 69%, reduced inducible NO synthase (iNOS) levels by 33% to 67%, reduced poly(ADP-ribose)polymerase-1 expression and cleavage 2- to 4-fold, and elevated levels of p27 in the distal colon 3-fold. Studies in cancer cell cultures recapitulated actions of GT-094: antiproliferative activity and transient G(2)-M phase cell cycle block were measured in Caco-2 cells; apoptotic activity was examined but not observed; anti-inflammatory activity was seen in the inhibition of up-regulation of iNOS and endogenous NO production in lipopolysaccharide (LPS)-induced RAW 264.7 cells. In summary, antiproliferative, anti-inflammatory, and cytoprotective activity observed in vivo and in vitro support GT-094 as a lead compound for the design of NO chimeras for colorectal cancer chemoprevention.     

吲哚美辛对结肠癌细胞HCT116的影响及机制探讨

目的:研究吲哚美辛对结肠癌细胞株HCT116增殖及体外侵袭的影响并对其机制进行探讨。方法:应用WST-8法和体外侵袭小室测定吲哚美辛对结肠癌细胞株HCT116增殖和侵袭能力的影响;Westen-blotting方法检测吲哚美辛作用后HCT116细胞β-连环素(β-Catenin)、细胞周期素D1(Cyclin D1)、基质金属蛋白酶7(matrix metalloproteinase-7,MMP-7)蛋白的表达。结果:吲哚美辛能够明显抑制结肠癌细胞株HCT116的增殖,呈时间-剂量依赖性,作用24、48、72h的IC50值分别为440.36、323.90、254.37μmol/L;吲哚美辛能够明显抑制结肠癌细胞株HCT116的体外侵袭,呈剂量依赖性;吲哚美辛作用24、48、72h后,β-Catenin、CyclinD1、MMP-7蛋白表达均有下降。结论:吲哚美辛能抑制结肠癌细胞株HCT116的增殖与迁移,其作用机制之一可能是通过Wnt/β-catenin信号通路。     

Inactivating cholecystokinin-2 receptor inhibits progastrin-dependent colonic crypt fission,proliferation, and colorectal cancer in mice

Hyperproliferation of the colonic epithelium, leading to expansion of colonic crypt progenitors, is a recognized risk factor for colorectal cancer. Overexpression of progastrin, a nonamidated and incompletely processed product of the gastrin gene, has been shown to induce colonic hyperproliferation and promote colorectal cancer in mice, but the mechanism of pathogenesis has not been defined. Cholecystokinin-2 receptor (CCK2R) is the primary receptor for cholecystokinin (CCK) and amidated gastrin. Here, we show that Cck2r was expressed in murine colonic crypts and upregulated in the transgenic mice that overexpress human progastrin. Murine deletion of Cck2r abrogated progastrin-dependent increases in colonic proliferation, mucosal thickness, and β-catenin and CD44 expression in the colon tumor. In addition, either deletion or antagonism of Cck2r resulted in the inhibition of progastrin-dependent increases in progenitors expressing doublecortin and CaM kinase–like-1 (DCAMKL1), stem cells expressing leucine rich repeat–containing G protein–coupled receptor 5 (LgR5), and colonic crypt fission. Furthermore, in the azoxymethane mouse model of colorectal carcinogenesis, Cck2r deletion in human progastrin–overexpressing mice resulted in markedly decreased aberrant crypt foci formation and substantially reduced tumor size and multiplicity. Taken together, these observations indicate that progastrin induces proliferative effects, primarily in colonic progenitor cells, through a CCK2R-dependent pathway. Moreover, our data suggest that CCK2R may be a potential target in the treatment or prevention of colorectal cancer.     

Green-synthesized gold nanoparticles from black tea extract enhance the chemosensitivity of doxorubicin in HCT116 cells via a ROS-dependent pathway

Green gold nanoparticles (GNPs) were prepared from black tea extract (BTE) and used to examine the chemosensitivity of doxorubicin in colon cancer cell line HCT116. BTE-GNPs were prepared by a single-step method and characterized by UV-Vis spectroscopy, FTIR spectroscopy, SEM, DLS and zeta-potential. The MTT assay was performed to determine the cytotoxicity of HCT116 cells and also normal kidney cells HEK293. Apoptosis and ROS generation were investigated by flow cytometry. The inhibition of ROS levels by the inhibitor NAC was determined by both spectrofluorimetry and confocal microscopy. Expression levels of pro- and anti-apoptotic proteins were determined by a western blot technique. BTE-GNPs significantly enhanced the cytotoxic effect of DOX with its co-treatment in HCT116 cells. The cytotoxic effect of BTE-GNP + DOX was involved in apoptosis via a ROS-dependent pathway by enhancing the pro-apoptotic protein expression. Therefore, our results indicated that green gold nanoparticles of black tea extract (BTE-GNP) may be potent chemosensitizers of doxorubicin.

Green gold nanoparticles (GNPs) were prepared from black tea extract (BTE) and used to examine the chemosensitivity of doxorubicin in colon cancer cell line HCT116.     

奥沙利铂对结肠癌细胞DNA损伤修复类抗药基因表达的影响

目的观察奥利沙铂对结肠癌细胞DNA损伤修复类基因表达的影响。方法采用奥利沙铂处理结肠癌细胞株HCT116 48 h。以Western blot免疫印迹法检测奥利沙铂诱导的DNA损伤。采用CCK-8方法探讨奥利沙铂对HCT116细胞生长的影响。采用实时荧光定量PCR(qRT-PCR)方法检测奥利沙铂处理后相关DNA损伤修复基因的表达。结果奥利沙铂处理后,HCT116细胞中DNA损伤标志基因γ-H2AX表达明显上升。DNA损伤切除修复相关基因XPC表达在奥利沙铂处理后出现显著上升,其他DNA损伤修复基因mRNA表达无明显上调。结论 XPC基因可能在临床应用奥沙利铂治疗结肠癌时肿瘤细胞产生抗药性的过程中起到了关键作用。     

结直肠癌TP53相关外泌体的差异蛋白分析

目的 比较分析T P53突变、敲除及野生的结直肠癌细胞分泌外泌体的蛋白质组差异.方法 从TP53野生型[HCT116-p53(WT)]、敲除型[HCT116-p53(-/-)]和构建的273位点突变型的结直肠癌HCT116细胞[HCT116-p53(R273H)]培养上清中分别提取外泌体,通过透射电镜观察其形态和免疫印...     

Knockdown of Forkhead box A1 suppresses the tumorigenesis and progression of human colon cancer cells through regulating the phosphatase and tensin homolog/Akt pathway

BackgroundThis study aimed to evaluate the role and the underlying mechanisms of Forkhead box A1 (encoded by FOXA1) in colon cancer.MethodsWe analyzed FOXA1 mRNA and protein expression in colon cancer tissues and cell lines. We also silenced FOXA1 expression in HCT116 and SW480 cells to evaluate the effects on cell proliferation, cell cycle, migration, and invasion by using MTT, colony formation, flow cytometry, and the Transwell assay, respectively.ResultsFOXA1 immunostaining was higher in colon cancer tissues than adjacent healthy tissues. FOXA1 mRNA and protein expression was significantly increased in human colon cancer cells compared with a normal colonic cell line. FOXA1 expression was also significantly higher in colorectal cancer tissues from TCGA data sets and was associated with worse prognosis in the R2 database. FOXA1 expression was negatively correlated with the extent of its methylation, and its knockdown reduced proliferation, migration, and invasion, and induced G2/M phase arrest in HCT116 and SW480 cells by suppressing the phosphatase and tensin homolog/Akt signaling pathway and inhibiting epithelial–mesenchymal transition.ConclusionFOXA1 may act as an oncogene in colon cancer tumorigenesis and development.     

Aspirin inhibits endothelial nitric oxide synthase (eNOS) and Flk-1 (vascular endothelial growth factor receptor-2) prior to rat colon tumour development

Formation of blood vessels is a fundamental element in the control of tumour growth in which vascular endothelial growth factor (VEGF) and nitric oxide (NO) have been demonstrated to be involved. Our aim was to analyse whether changes in the expression of endothelial NO synthase (eNOS) and VEGF in colonic tissue could be detected early and even before the identification of colon tumour-associated morphological modifications in azoxymethane-treated rats. We studied further whether aspirin treatment changed these parameters. An increased expression of both eNOS and VEGF in colonic tissue from azoxymethane-treated rats compared with that from control rats was found. Aspirin treatment (10 mg/kg of body weight per day) reduced eNOS expression, but failed to modify the expression of VEGF in the colonic tissue of azoxymethane-treated rats. No evidence of aberrant crypt formation or changes in the number of blood vessels were observed in the colon of any of the animals studied. Expression of the VEGF receptor Flk-1, but not Flt-1, was increased in colonic tissue of azoxymethane-treated rats compared with control rats. The expression of Flk-1 was mainly localized in the epithelial cells, particularly in the lower part of the crypt. Aspirin treatment reduced Flk-1 expression in both control and azoxymethane-treated rats. Caspase-3 activity, which has been considered as an apoptotic index, was almost undetectable in azoxymethane-treated rats. Aspirin treatment stimulated caspase-3 activity. Overexpression of eNOS, VEGF and its receptor Flk-1 occurred early after azoxymethane administration in rat colonic tissue, even before morphological changes associated with tumour generation were observed, and aspirin prevented the overexpression of both eNOS and VEGF receptor Flk-1.     

肝X受体激动剂GW3965对人结肠癌细胞增殖的抑制作用

目的:探讨激活肝X受体(liver X receptors,LXRs)对人结肠癌细胞增殖的影响。方法:采用实时定量聚合酶链反应检测人结肠癌细胞HCT116和Lovo中LXRα和LXRβ的mRNA表达;LXRs激动剂GW3965分别处理2种细胞后,以CCK-8法检测细胞生长曲线的变化,流式细胞仪检测细胞增殖周期的变化,蛋白印迹法检测AMPK、mTOR和p70S6K蛋白及相应磷酸化蛋白的表达变化。结果 :设定LXRαmRNA在HCT116细胞的表达水平为1,LXRβmRNA在HCT116和Lovo细胞中的相对表达量分别是LXRαmRNA在HCT116细胞表达水平的3.1倍和4.6倍。经10μmol/L和20μmol/L的GW3965处理48 h及72 h后,2种结肠癌细胞的生长都受到明显抑制(P<0.05);相应G1~G0期细胞百分比显著增多,而S期细胞百分比明显减少(P<0.01);磷酸化AMPK蛋白(p-AMPK)的表达水平在HCT116和Lovo细胞中分别上升了2.97倍和3.48倍(P<0.05);p-mTOR和p-p70S6K在HCT116细胞中的表达分别下降了33.14%和38.44%,在Lovo细胞中的表达分别下降了51.68%和31.52%(P<0.05)。结论:激活LXRs可通过干预细胞周期和AMPK-mTOR-S6K信号通路抑制结肠癌细胞增殖。     

以KDR为启动子的双自杀基因系统诱导结肠癌细胞凋亡的实验研究

目的研究以KDR为启动子的双自杀基因系统CDglyTK诱导结肠癌细胞凋亡的实验研究。方法用联合基因AdKDR-CDglyTK腺病毒转染表达KDR不同的人结肠癌细胞HCT116和LS174T,检测转染效率;RT-PCR检测双自杀基因CDglyTK的表达;用梯度浓度的前药5-FC及GCV处理,MTT法检测双自杀基因系统对HCT116和LS174T的细胞毒性作用;流式细胞术观察细胞凋亡变化;免疫组织化学法检测caspase-3蛋白的表达。结果携带双自杀基因的重组腺病毒载体成功转染结肠癌细胞。RT-PCR结果显示：表达KDR的HCT116细胞能表达目的基因,而不表达KDR的LS174T细胞不表达目的基因。5-FC和GCV对转染腺病毒的HCT116有明显的细胞毒作用而对LS174T细胞不敏感。流式细胞仪结果显示：给予5-FC和GCV后HCT116细胞出现凋亡峰,G0/G1升高、S期下降。Caspase-3表达增强（P〈0.01）。结论 KDR启动子驱动的双自杀基因系统CDglyTK能特异性杀伤结肠癌HCT116细胞,KDR可作为结肠癌基因治疗的靶点,并通过增强caspase-3途径诱导细胞凋亡。     

5-Aminoimidazole-4-carboxamide riboside sensitizes TRAIL- and TNF{alpha}-induced cytotoxicity in colon cancer cells through AMP-activated protein kinase signaling

Death receptor-mediated tumor cell death, either alone or in combination with other anticancer drugs, is considered as a new strategy for anticancer therapy. In this study, we have investigated the effects and molecular mechanisms of 5-aminoimidazole-4-carboxamide riboside [AICAR; a pharmacologic activator of AMP-activated protein kinase (AMPK)] in sensitizing tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)- and TNFalpha-induced apoptosis of human colon cancer HCT116 cells. The cytotoxic action of AICAR requires AMPK activation and may occur at various stages of apoptotic pathways. AICAR cotreatment with either TRAIL or TNFalpha enhances activities of caspase-8, caspase-9, and caspase-3; down-regulates the antiapoptotic protein Bcl-2; increases the cleavage of Bid and results in the decrease of mitochondrial membrane potential; potentiates activation of p38 and c-Jun NH(2)-terminal kinase; and inhibits nuclear factor-kappaB activity. In addition, this sensitized cell apoptosis was neither observed in p53-null HCT116 cells nor affected by the cotreatment with mevalonate. In summary, we have developed a novel strategy of combining AICAR with TRAIL for the treatment of colon cancer cells. The sensitization effect of AICAR in cell apoptosis was mediated through AMPK pathway, requires p53 activity, and involves mitochondria-dependent apoptotic cascades, p38 and c-Jun NH(2)-terminal kinase.