胶质瘤SLC22A18耐药细胞株的建立及其耐药机制的研究

目的:以人胶质瘤U251细胞株为载体,探讨胶质瘤获得性SLC22A18 基因耐药的可能机制。方法:用重组腺病毒介导的SLC22A18基因(Ad/SLC22A18)反复处理人胶质瘤U251细胞,得到人胶质瘤耐药细胞株U251-SLC22A18/R。通过MTT和Western blot法检测耐药细胞U251-SLC22A18/R对Ad/SLC22A18杀伤作用的敏感性及凋亡相关的信号分子DR4、DR5、Bax、Bcl-XL和caspase-8的表达情况,分析其获得性耐药的可能机制。结果:耐药细胞U251-SLC22A18/R对Ad/SLC22A18和SLC22A18蛋白处理耐药,但对Bax基因处理仍然敏感。U251-SLC22A18/R细胞内Bcl-XL 的表达显著升高,caspase-8的表达明显下降,caspase-8 活性未见明显的裂解。结论:人胶质瘤U251细胞株经Ad/SLC22A18反复处理后产生针对SLC22A18基因的耐药,其机制可能与Bcl-XL 表达升高和caspase-8 表达下降有关。     

Bcl-XL小分子干扰RNA逆转人结肠癌获得性肿瘤坏死因子相关凋亡诱导配体的耐药

目的 探讨Bcl-XL小分子干扰RNA(siRNA)在逆转人结肠癌细胞获得性肿瘤坏死因子相关的凋亡诱导配体(TRAIL)耐药中的作用.方法 以Bcl-XL siRNA转染获得性TRAIL耐药的人结肠癌DLD1-TRAIL/R细胞24 h,并用TRAIL蛋白处理,通过细胞计数和流式细胞仪检测细胞的存活率,并通过Western blot法检测各种凋亡相关蛋白的活化情况.结果Bcl-XL siRNA能有效下调DLD1-TRAIL/R细胞中Bcl-XL蛋白的表达水平,并且能够有效地逆转其对TRAIL蛋白的耐药.DLD1-TRAIL/R细胞经过Bcl-XL siRNA和TRAIL蛋白共同处理2 h后,其细胞凋亡率＞50%;共同处理4 h后,其细胞存活率＜40%;而对照组和TRAIL蛋白处理组的细胞凋亡率和生存率无明显变化(P＜0·05).Western blot法检测结果表明,经Bcl-XL siRNA与TRAIL蛋白联合处理后,DLD1TRAIL/R细胞中caspase-8、caspase-9、Bid、caspase-3以及多聚腺苷酸二磷酸核糖聚合酶(PARP)均明显活化,细胞色素C的释放显著增加.结论 Bcl-XL siRNA能够有效逆转结肠癌细胞获得性TRAIL耐药,这将为治疗肿瘤耐药提供一种新的思路.     

蛋白酶体抑制剂MG-132逆转人结肠癌细胞获得性TRAIL耐药

目的:探讨蛋白酶体抑制剂MG-132逆转人结肠癌细胞获得性TRAIL耐药的作用及其可能的机制.方法:在MG-132和TRAIL蛋白联合处理获得性TRAIL耐药的人结肠癌细胞DLD1-TRAIL/R后,MTT法检测细胞的存活率,流式细胞术检测细胞凋亡率,Western blotting检测细胞中各种凋亡相关蛋白的表达和JNK激酶的磷酸化水平.结果:MG-132联合TRAIL蛋白处理DLD1-TRAIL/R细胞后,其细胞存活率明显下降(P<0.01),而细胞凋亡率则明显增加(P<0.01).Western blotting检测显示,联合处理后DLD1-TRAIL/R细胞中各种凋亡信号分子包括caspase-8、caspase-9、caspase-3、Bid和PARP蛋白均明显活化,线粒体中细胞色素C和Smac蛋白大量释放;进一步的Western blotting检测显示,死亡受体DR5和凋亡诱导蛋白Bik的表达水平明显增高,而其他凋亡信号分子包括DR4、Bax、Bak、Bcl-XL、XIAP和Survivin等则无明显改变;检测结果还显示,MG-132能诱导JNK激酶发生磷酸化,使用JNK激酶抑制剂SP600125能够阻断MG-132诱导的DR5表达,但不影响Bik的表达,并且不能减弱MG-132和TRAIL蛋白联合处理对DLD1-TRAIL/R细胞的致凋亡效应(P<0.05).结论:蛋白酶体抑制剂MG-132能逆转人结肠癌细胞DLD1-TRAIL/R的获得性TRAIL耐药,其机制可能与Bik蛋白上调后启动线粒体凋亡途径有关,与JNK通路激活无关.     

蛋白酶体抑制剂MG-132逆转人结肠癌细胞获得性TRAIL耐药

目的: 探讨蛋白酶体抑制剂MG132逆转人结肠癌细胞获得性TRAIL耐药的作用及其可能的机制。方法：在MG132和TRAIL蛋白联合处理获得性TRAIL耐药的人结肠癌细胞DLD1TRAIL/R后,MTT法检测细胞的存活率,流式细胞术检测细胞凋亡率,Western blotting检测细胞中各种凋亡相关蛋白的表达和JNK激酶的磷酸化水平。结果：MG132联合TRAIL蛋白处理DLD1TRAIL/R细胞后,其细胞存活率明显下降（P<0.01）,而细胞凋亡率则明显增加（P<0.01）。Western blotting检测显示,联合处理后DLD1TRAIL/R细胞中各种凋亡信号分子包括caspase8、caspase9、caspase3、Bid和PARP蛋白均明显活化,线粒体中细胞色素C和Smac蛋白大量释放;进一步的Western blotting检测显示,死亡受体DR5和凋亡诱导蛋白Bik的表达水平明显增高,而其他凋亡信号分子包括DR4、Bax、Bak、BclXL、XIAP和Survivin等则无明显改变;检测结果还显示,MG132能诱导JNK激酶发生磷酸化,使用JNK激酶抑制剂SP600125能够阻断MG132诱导的DR5表达,但不影响Bik的表达,并且不能减弱MG132和TRAIL蛋白联合处理对DLD1TRAIL/R细胞的致凋亡效应（P<0.05）。结论：蛋白酶体抑制剂MG132能逆转人结肠癌细胞DLD1TRAIL/R的获得性TRAIL耐药,其机制可能与Bik蛋白上调后启动线粒体凋亡途径有关,与JNK通路激活无关。     

Bcl-XL小发夹RNA腺病毒载体的构建及其抗肿瘤作用

目的:构建表达Bcl-XL小发夹RNA的腺病毒载体(Ad/Bcl-XL shRNA)并探讨其抗肿瘤作用。方法:构建、纯化重组腺病毒Ad/Bcl-XL shRNA。通过Western blotting、MTT分析验证它对Bcl-XL的下调及其杀伤肿瘤细胞的作用,并检测其处理后细胞凋亡信号的活化情况;在裸鼠皮下荷瘤模型中验证其体内抗肿瘤作用。结果:成功构建和纯化了Ad/Bcl-XLshRNA,它能显著下调结肠癌DLD1细胞Bcl-XL蛋白的表达;与Ad/GFP、PBS组相比,Ad/Bcl-XL shRNA组明显抑制人结肠癌细胞DLD1的生长[1 000 MOI时(60.6±4.8)%vs(99.0±2.6)%、100%;2 000 MOI时,(37.3±6.9)%vs(99.0±2.1)%、100%,P<0.01],但对正常人成纤维细胞无明显抑制作用(P>0.05);Ad/Bcl-XL shRNA组能有效诱导结肠癌细胞中凋亡信号casepase-9、casepase-3、PARP的活化。在裸鼠荷瘤模型中,与Ad/GFP、PBS组相比,Ad/Bcl-XL shRNA组显著抑制DLD1来源皮下肿瘤的生长[第29天时,(250.1±185.7)vs(880.0±286.1)、(911.0±389.1)mm3;P<0.01]。结论:Ad/Bcl-XLshRNA能显著抑制结肠癌细胞在体内外的生长,其在结肠癌治疗中具有潜在的应用价值。     

沉默Bcl-XL逆转人胶质瘤获得性SLC22A18的耐药

目的:探讨RNA干扰Bcl-XL(siRNA）在人胶质瘤获得性SLC22A18的耐药中的作用。方法:以Bcl-XL siRNA转染获得性SLC22A18耐药的人胶质瘤U251-SLC22A18/R细胞,用重组人SLC22A18蛋白处理,MTT法和流式细胞仪检测肿瘤细胞的存活率,免疫印迹法检测凋亡相关蛋白Caspase-3和Caspase-8的表达情况。结果:Bcl-XL siRNA能够降低U251-SLC22A18/R细胞中Bcl-XL的表达,也能逆转其对SLC22A18的耐药。U251-SLC22A18/R细胞经过Bcl-XL siRNA和重组人SLC22A18蛋白共同处理4 h后细胞凋亡率>50%,细胞存活率<30%;而对照组和重组人SLC22A18蛋白处理组的细胞凋亡率和存活率无明显变化。经Bcl-XL siRNA与重组人SLC22A18蛋白联合处理后,U251-SLC22A18/R细胞中Caspase-3和Caspase-8均明显活化。结论:Bcl-XL siRNA能有效逆转人胶质瘤获得性SLC22A18的耐药,为治疗胶质瘤耐药提供一种新的思路。     

不同化疗药物对胶质瘤获得性SLC22A18基因耐药的逆转作用

目的:探讨临床上治疗胶质瘤的不同化疗药物对胶质瘤U251细胞获得性SLC22A18耐药的逆转作用及可能的分子机制。方法:将重组腺病毒载体(Ad)介导的SLC22A18基因联合替莫唑胺(TMZ)、卡氮芥(BCNU)以及顺铂(DDP)3种常见化疗药物处理对Ad/SLC22A18产生耐药的U251-SLC22A18/R胶质瘤细胞,通过MTT比色法检测处理后胶质瘤细胞的存活率,以评估体外不同化疗药物对SLC22A18耐药的逆转作用;在体内进一步评估该逆转策略的有效性;并且通过免疫印迹等方法探讨逆转耐药的可能的分子机制。结果:在体外只有TMZ和BCNU能够使U251-SLC22A18/R细胞对Ad/SLC22A18重新敏感。进一步的研究结果表明联合TMZ和Ad/SLC22A18能在体内有效地抑制U251-SLC22A18/R细胞来源的胶质瘤生长,且联合TMZ和Ad/SLC22A18抑制作用明显比其它对照组强。Ad/SLC22A18和TMZ的联合治疗可以下调MGMT蛋白的表达,并且Ad/SLC22A18和BCNU的联合治疗可以上调Bax蛋白的表达。结论:联合应用Ad/SLC22A18和TMZ或BCNU能在体内外有效地逆转U251-SLC22A18/R细胞对SLC22A18的获得性耐药,TMZ的逆转作用可能与其诱导的MGMT蛋白低表达有关,BCNU的逆转作用可能与其诱导的Bax蛋白过度表达有关。     

结肠癌耐药细胞株LoVo/L-OHP的建立及其耐药机制

目的:建立获得性奥沙利铂(L-OHP)耐药的结肠癌细胞模型LoVo/L-OHP,并初步研究其耐药机制。方法:采用L-OHP浓度递增法建立人结肠癌细胞耐药模型LoVo/L-OHP,观察其生长规律并绘制细胞生长曲线;用MTT法鉴定耐药细胞株耐药性并计算耐药指数(RI);用半定量RT-PCR方法对部分耐药相关基因在耐药细胞及其亲本细胞中的表达情况进行分析。结果:成功建立了耐药的结肠癌细胞模型LoVo/L-OHP,LoVo/L-OHP细胞与LoVo细胞相比,生长缓慢,触角增多。通过RT-PCR半定量分析,P-gp、bcl-2、ERCC-1在LoVo/L-OHP中的表达上调,而p53基因表达下调。结论:LoVo/L-OHP细胞株耐药性稳定,耐药机制可能与P-gp、bcl-2、ERCC-1基因上调、p53基因下调多因素有关。     

结肠癌耐药细胞株LoVo/L-OHP的建立及其耐药机制

目的：建立获得性奥沙利铂（L-OHP）耐药的结肠癌细胞模型LoVo/L-OHP,并初步研究其耐药机制。方法：采用L-OHP浓度递增法建立人结肠癌细胞耐药模型LoVo/L-OHP,观察其生长规律并绘制细胞生长曲线;用MTT法鉴定耐药细胞株耐药性并计算耐药指数（RI）;用半定量RT-PCR方法对部分耐药相关基因在耐药细胞及其亲本细胞中的表达情况进行分析。结果：成功建立了耐药的结肠癌细胞模型LoVo/L-OHP,LoVo/L-OHP细胞与LoVo细胞相比,生长缓慢,触角增多。通过RT-PCR半定量分析,P-gp、bcl-2、ERCC-1在LoVo/L-OHP中的表达上调,而p53基因表达下调。结论：LoVo/L-OHP细胞株耐药性稳定,耐药机制可能与P-gp、bcl-2、ERCC-1基因上调、p53基因下调多因素有关。     

腺病毒介导mda-7/IL-24基因感染对卵巢癌耐药细胞凋亡的影响

背景与目的:Mda-7/IL-24基因是一个具有选择性的诱导肿瘤细胞凋亡和细胞因子免疫调节功能双重作用的基因,在抗肿瘤基因治疗方面有很好的应用前景,本研究利用构建的mda-7/IL-24重组腺病毒感染卵巢癌耐药细胞株,了解其对卵巢癌耐药细胞的抗肿瘤作用.方法:利用腺病毒AdEasy 1载体构建含目的基因的Ad.mda-7/IL-24,感染两种卵巢癌耐药细胞株OVCAR-3和OVCAR-8/TR,Western blot法检测感染后MDA-7/IL-24蛋白表达,用Hoechst33258凋亡染色和流式细胞仪检测感染后细胞的凋亡和细胞周期改变.结果:Ad.mda-7/IL-24经测序、酶切电泳、感染后Western blot检测MDA-7蛋白表达,表明构建成功;感染Ad.mda-7后72 h内OVCAR-3细胞最高凋亡率为14.1%,OVCAR-8/TR细胞为32.4%,明显高于空载体组和未感染组.结论:成功构建了Ad.mda-7/IL-24重组腺病毒,用其感染卵巢癌耐药细胞可诱导细胞凋亡.     

Accelerated degradation of caspase-8 protein correlates with TRAIL resistance in a DLD1 human colon cancer cell line

The tumor-selective cytotoxic effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) makes TRAIL an attractive candidate as an anticancer agent. However, resistance to TRAIL poses a challenge in anticancer therapy with TRAIL. Therefore, characterizing the mechanisms of resistance and developing strategies to overcome the resistance are important steps toward successful TRAIL-mediated cancer therapy. In this study, we investigated mechanisms of acquired TRAIL resistance in a colon cancer DLD1 cell line. Compared with the TRAIL-susceptible DLD1 cell line, TRAIL-resistant DLD1/TRAIL-R cells have a low level of caspase-8 protein, but not its mRNA. Suppression of caspase-8 expression by siRNA in parental DLD1 cells led to TRAIL resistance. Restoration of caspase-8 protein expression by stable transfection rendered the DLD1/TRAIL-R cell line fully sensitive to TRAIL protein, suggesting that the low level of caspase-8 protein expression might be the culprit in TRAIL resistance in DLD1/TRAIL-R cells. Sequencing analysis of the caspase-8 coding region revealed a missense mutation that is present in both TRAIL-sensitive and TRAIL-resistant DLD1 cells. Subsequent study showed that the degradation of caspase-8 protein was accelerated in DLD1/TRAIL-R cells compared to parental DLD1 cells. Thus, accelerated degradation of caspase-8 protein is one of the mechanisms that lead to TRAIL resistance.     

Adenoviral vector expressing CYLD augments antitumor activity of TRAIL by suppression of NF-kappaB survival signaling in hepatocellular carcinoma

CYLD is a tumor suppressor gene related to cylindroma and is negative regulator of NF-kappaB. However, antitumor effect of CYLD has not been reported. The activation of NF-kappaB induced by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) renders hepatocellular carcinoma (HCC) resistant to TRAIL-mediated cell apoptosis. Here we described that the adenoviral vector expressing CYLD (Ad/hTERT-CYLD) augmented the cytotoxicity of TRAIL in HCC cells by negatively regulating NF-kappaB activity since CYLD could reverse the ubiquitination of TNF receptor-associated factor 2 (TRAF2) and interact with the IkappaB kinasegamma (IKKgamma). The combined treatment of Ad/hTERT-CYLD and a conditionally replicating adenovirus carrying TRAIL gene (ZD55-TRAIL) induced rapid and potent apoptosis in HCC cells, characterized by activation of caspase-3, caspase-8, PARP and the reduction of X-linked inhibitor of apoptosis protein (XIAP). In animal study, the combined treatment could eradicate the BEL7404 xenograft tumors. In contrast, treatment with Ad/hTERT-CYLD or ZD55-TRAIL alone achieved less antitumor effect. In conclusion: CYLD inhibits TRAIL-mediated NF-kappaB activation and enhances the sensitivity of HCC cells to TRAIL-triggered apoptosis. The combined delivery of Ad/hTERT-CYLD and ZD55-TRAIL may be a new useful strategy for HCC or other tumor cells with enhanced NF-kappaB activity.     

Adenovirus-mediated small hairpin RNA targeting Bcl-XL as therapy for colon cancer

Bcl-XL, an anti-apoptotic protein of Bcl-2 family, is overexpressed in colon cancers. To determine Bcl-XL's potential feasibility as a therapeutic target, we constructed a recombinant adenovirus that expressed a U6 promoter-driven small hairpin RNA (shRNA) targeting Bcl-XL (Ad/Bcl-XL shRNA) and evaluated the vector's ability to induce RNA interference in vivo and alter apoptosis induction in colon cancer cells and tumours. Ad/Bcl-XL shRNA effectively knocked down Bcl-XL expression in colon cancer cells and decreased their viability. Treatment with Ad/Bcl-XL shRNA but not control vectors led to dramatically increased cleavage of cellular apoptosis-related enzymes caspase-9, caspase-3 and poly(ADP-ribose) polymerase. Ad/Bcl-XL shRNA also significantly suppressed the growth of subcutaneous tumours derived from DLD1 cells in a nude mouse model and did so without causing any obvious damage to normal tissues or normal human fibroblasts. Together, our results support the feasibility of using adenovirus-mediated RNA interference therapy targeting Bcl-XL against colon cancers and warrant further studies of its safety and efficacy.     

Proteasome inhibitors-mediated TRAIL resensitization and Bik accumulation

Proteasome inhibitors can resensitize cells that are resistant to tumor necrosis factor-related apoptotic-inducing ligand (TRAIL)-mediated apoptosis. However, the underlying mechanisms of this effect are unclear. To characterize the mechanisms of interaction between proteasome inhibitors and TRAIL protein, we evaluated the effects of combined treatment with the proteasome inhibitors bortezomib and MG132 and TRAIL protein on two TRAIL-resistant human colon cancer cell lines, DLD1-TRAIL/R and LOVO-TRAIL/R. Both bortezomib and MG132 in combination with TRAIL enhanced apoptotosis induction in these cells, as evidenced by enhanced cleavage of caspases 8, 9, and 3, Bid, poly(ADP-ribose) polymerase and by the release of cytochrome C and Smac. Subsequent studies showed that combined treatment with bortezomib or MG132 resulted in an increase of death receptor (DR) 5 and Bik at protein levels but had no effects on protein levels of DR4, Bax, Bak, Bcl-2, Bcl-XL or Flice-inhibitory protein (FLIP). Moreover, c-Jun N-terminal kinase (JNK) is activated by these proteasome inhibitors. Blocking JNK activation with the JNK inhibitor SP600125 attenuated DR5 increase, but enhancement of apoptosis induction and increase of Bik protein were not affected. However, bortezomib-mediated TRAIL sensitization was partially blocked by using siRNA to knockdown Bik. Thus, our data suggests that accumulation of Bik may be critical for proteasome inhibitor-mediated resensitization of TRAIL.     

Long-term tumor-free survival from treatment with the GFP-TRAIL fusion gene expressed from the hTERT promoter in breast cancer cells

We evaluated anti-tumor activity and toxic effect of an adenoviral vector expressing the GFP/TRAIL fusion gene from the hTERT promoter (designated Ad/gTRAIL) on human breast cancer cell lines and on normal human breast cells. Treatment with Ad/gTRAIL elicited high levels of transgene expression and apoptosis in a variety of breast cancer cell lines. Furthermore, treatment with Ad/gTRAIL was effective in killing breast cancer lines resistant to doxorubicin or soluble TRAIL protein. In contrast, only minimal transgene expression and toxicity was detected in normal human primary mammary epithelial cells after treatment with this vector. An in vivo study further showed that the intralesional administration of Ad/gTRAIL effectively suppressed the growth of human tumor xenografts derived from both doxorubicin-sensitive and doxorubicin-resistant breast cancer lines. Specifically, about 50% of animals bearing doxorubicin-sensitive and doxorubicin-resistant breast cancer xenografts showed complete tumor regression and remained tumor-free for over 5 months. These results suggest that the adenovirus encoding the GFP/TRAIL gene driven by the hTERT promoter has potential application in cancer therapy.