新合成黄腐酚类似物联合顺铂对宫颈癌细胞化疗增敏作用的研究

摘要 目的：探讨新合成黄腐酚类似物联合顺铂对宫颈癌Hela细胞化疗敏感性的影响及其机制。方法：以不同浓度（5、7.5、15、20 μmol/L）黄腐酚类似物处理宫颈癌Hela细胞和正常MRC-5细胞48 h后,MTT实验检测细胞增殖活力并计算出黄腐酚类似物对2种细胞的半数抑制浓度(IC₅₀);采用MTT实验进一步观察IC₅₀最低的黄腐酚类似物联合顺铂对Hela和MRC-5细胞增殖活力的影响,采用流式细胞仪检测Hela细胞周期和凋亡情况,Western blot法检测Hela细胞中凋亡相关蛋白表达变化。结果：黄腐酚类似物a8、a13、b11和b12对宫颈癌Hela细胞增殖均有一定的抑制作用,且a13的IC₅₀值最小;另外,这4种浓度的黄腐酚类似物对正常MRC-5细胞有轻微的抑制作用,且a13的IC50值最大。与对照组比较,顺铂组、a13组、顺铂+a13组中正常MRC-5细胞存活率差异均无统计学意义（P<0.05）,但顺铂组、a13组和顺铂+a13组中宫颈癌Hela细胞存活率、G2/M期细胞百分比和B淋巴细胞瘤-2基因（Bcl-2）蛋白表达水平均明显降低,而G0/G1期细胞百分比、细胞凋亡率和细胞中细胞色素C（Cyt-c）、Bcl-2关联X蛋白（Bax）、活化的半胱氨酸天冬氨酸蛋白酶3（Cleaved Caspase-3）、活化的半胱氨酸天冬氨酸蛋白酶9（Cleaved Caspase-9）蛋白表达水平均明显升高,且顺铂+a13组中上述指标变化幅度明显大于顺铂组、a13组（P<0.05）。结论：黄腐酚类似物与顺铂联合可协同抑制宫颈癌Hela细胞增殖,表现良好的化疗增敏效果,其作用机制可能与阻滞细胞周期进程和调控凋亡相关蛋白表达促进细胞凋亡有关。     

P53突变、表达及人乳头状瘤病毒感染与宫颈癌

利用免疫组化、聚合酶链反应(PCR)、单链构象多态性(SSCP)分析等方法, 对49例同一标本宫颈癌组织中p53蛋白、P₅₃外显子7～8变异、HPV6、11、16、18-DNA进行检测,以探讨它们在宫颈癌形成中的作用、相互关系和临床意义.结果表明: a.P₅₃基因外显子7～8突变率14.29％、p53蛋白阳性率48.98％、HPV-DNA阳性率87.76％.b.P₅₃基因突变不一定伴有p53蛋白阳性,但P₅₃基因突变而p53蛋白阴性的标本必是HPV-DNA阳性;91.67％的p53蛋白阳性标本具有HPV-DNA阳性.c.HPV16-DNA阳性率显著高于HPV6、11、18-DNA阳性率.证明：宫颈癌的发生主要与HPV16感染有关,其次是P₅₃基因突变所致;p53蛋白阳性由HPV感染和/或P₅₃基因突变所致.     

p53转录活化的p21和Gadd45在细胞DNA损伤监视中的作用

p2 1,Gadd45均是受抑癌基因p5 3转录调控的分子 ,当电离辐射引起细胞DNA损伤时 ,p2 1,Gadd45基因的转录以p5 3依赖的方式增强 .为了深入探讨p2 1,Gadd45在DNA损伤监视中的作用 ,构建了稳定表达p2 1及Gadd45反义RNA的p2 1^as/MCF 7及Gadd45 ^as/MCF 7细胞系 .对辐射引起这些细胞G₁期阻滞、DNA损伤修复和细胞凋亡的发生进行了研究 ,发现Gadd45同p2 1一样 ,当其表达受阻后辐射引起的细胞G₁期阻滞明显减弱 ,宿主细胞对辐射损伤的报告基因的修复减弱 ,还观察到辐射引起的p2 1表达受阻的细胞调亡的增加 ,结果表明p2 1,Gadd45通过参与多种辐射细胞学反应发挥DNA损伤监视作用 .     

Rb、P53调控平滑肌细胞c-fos和c-jun基因表达

为研究外源性Rb和P₅₃基因导入血管平滑肌细胞后对c-fos和c-jun基因表达的调控作用,将Rb基因或P₅₃基因重组腺病毒载体转染人脐动脉血管平滑肌细胞,应用RT-PCR和免疫组化法检测c-fos、c-jun的mRNA及蛋白质表达水平,以DNA琼脂糖凝胶电泳和β-半乳糖苷酶染色分别观察细胞凋亡和细胞衰老.结果显示,野生型P₅₃基因导入可诱导平滑肌细胞凋亡,c-fos和c-jun mRNA及蛋白质表达水平显著增高.外源性Rb基因导入能促进细胞衰老,下调c-fos基因表达,但对c-jun基因表达没有明显影响.     

参与细胞增殖调控的多功能分子p21

p21是近年来发现的一类调控细胞增殖的小分子,是依赖周期素的CDK抑制因子.这些蛋白因子可结合cyclin－CDK并抑制其激酶活性从而调节细胞周期p15、p16、p27均属该类分子,他们在G₁期限制点及G₁／S检查点调控中发挥作用．进一步的研究表明,p21为p53调控,在p53介导的DNA损伤诱发的细胞周期阻断中发挥作用p21在老化细胞中高表达、细胞分化的同时表达,表明其在细胞增殖、分化及老化中发挥调节作用．     

KGF联合HIF-1α对BECN1敲除IEC-6细胞缺氧的保护作用及机制

摘要 目的：探讨KGF联合HIF-1α对BECN1敲除后的IEC-6细胞在缺氧应激状态下的保护作用及相关机制。方法：构建敲除BECN1基因的稳定细胞系IEC-6B-细胞,分为空白对照组（BC）、阴性对照组（NC）、HIF-1α组、KGF联合HIF-1α组（KH）。观察细胞形态学改变。检测细胞存活率、ATP含量、细胞周期和细胞凋亡率。检测自噬相关基因表达水平和凋亡、自噬相关蛋白的表达。结果：低氧处理24 h后,各组细胞可见梭形、星形及其它异常形态变化;NC组细胞胞质内可见大量大小不一的吞噬溶酶体泡;其他各组细胞呈现细胞早期凋亡形态变化,BC组和KH组细胞胞质中可见自噬泡。与BC组相比较,各敲除组细胞存活率均显著降低（P<0.01）,其中KH组细胞存活率高于NC组、KGF组及HIF-1α组（P<0.05）。BC组细胞内ATP含量均显著高于其他各组（P<0.05）。与BC组和KH组比较,其他三组细胞G0/G1期百分比显著增加,细胞凋亡率均显著增加（P<0.05）。与BC组相比较,其余各组细胞自噬基因BECN1、SQSTM1及LC3基因mRNA表达均显著降低（P<0.05）;Beclin 1蛋白及LC3 II/LC3 I的比值均显著降低（P<0.05）,且p62蛋白表达显著增加（P<0.05）。KH组的Bax/Bcl-2的比值、Caspase3蛋白表达低于NC组（P<0.05）。结论：KGF联合HIF-1α能促进细胞增殖、增强细胞能量代谢、减少G₀/G₁期阻滞细胞率、抑制细胞凋亡作用,对低氧应激的IEC-6B-细胞具有保护作用。     

人线粒体tRNALeu（UUR）基因氧化损伤与修复研究

人mtDNA比核DNA更易受到自由基的氧化损伤,这些损伤可以被线粒体内的DNA修复机制所修复,损伤与修复是决定突变是否产生的两个重要因素.为了确定氧化损伤与损伤后修复对mtDNA突变的具体影响,采用四氧嘧啶处理LO₂细胞,这种试剂进入细胞后,经氧化还原反应生成的自由基与线粒体自身代谢产生的自由基类似,然后观察自由基对细胞mtDNA的氧化损伤与损伤后DNA修复的动力学变化.由于线粒体的正常功能为修复机制所必需,采用MTT细胞活力实验检测不同浓度四氧嘧啶处理下线粒体酶活力,发现9 mmol/L四氧嘧啶培养细胞1h后,线粒体琥珀酸脱氢酶功能在撤去药物后0,2,8和24 h时间点均无明显变化.提取各组细胞的mtDNA,用EndoⅢ和Fgp两种酶切除受氧化损伤的核苷酸,然后用碱性琼脂糖凝胶电泳分离大小不等的mtDNA,进行DNA印迹实验,地高辛-抗体-碱性磷酸酶系统显色,检测完整与断裂的mtDNA量,利用Poisson公式（s=－lnP₀/P,P₀为未断裂链光密度值,P为所有链光密度值总和）计算一个mtDNA分子的平均损伤频率,结果显示,9 mmol/L四氧嘧啶处理细胞1 h,链平均损伤频率由对照的0.11个/分子增加至5.60个/分子,明显增加了mtDNA上核苷酸的氧化损伤,除去药物后8 h,绝大部分损伤可被修复,损伤频率减至0.40个/分子,除去药物后24 h核苷酸的氧化损伤恢复至正常水平.采用接头介导PCR（LM-PCR）检测MTTL1基因区域内单个核苷酸的损伤与修复动力学.这种方法可以检测各组mtDNA上MTTL1基因75 bp区域内单个核苷酸损伤的部位及频率.结果显示,人MTTL1基因存在20个易受氧化损伤的核苷酸热点,经与相应区域内文献报道的16个突变热点比较,有12个热点部位重合,而修复未显示热点部位或区域.结果提示,自由基对核苷酸的选择性氧化损伤是决定mtDNA点突变发生及发生部位的主要原因.     

iNOS抑制剂1400W通过p53途径增强顺铂对宫颈癌SiHa细胞的化疗效果

该文探讨了iNOS抑制剂1400W联合顺铂对宫颈癌SiHa细胞株生长抑制作用及其机制。应用MTT法检测1400W及顺铂对宫颈癌Si Ha细胞生长的抑制作用;流式细胞仪检测1400W及顺铂对宫颈癌Si Ha细胞凋亡的影响;quantitative RT-PCR和Western blot检测1400W及顺铂对宫颈癌Si Ha细胞p53、鼠双微基因2(murine double minut 2,MDM2)、DNA依赖蛋白激酶(DNA-dependent protein kinase,DNA-PK)蛋白及m RNA表达的影响。结果显示,通过i NOS抑制剂1400W联合顺铂作用于宫颈癌Si Ha细胞株发现,1400W联合顺铂能明显抑制Si Ha细胞生长,其抑制作用与剂量呈正相关。1400W可以增强顺铂诱导的细胞凋亡作用。进一步研究证实,1400W可以抑制顺铂诱导的p53积聚,增加鼠双微基因2及DNA依赖蛋白激酶的表达。该实验结果为治疗宫颈癌患者提供了新的治疗策略,即通过联合使用i NOS抑制剂,可以增强顺铂对宫颈癌细胞的杀伤作用,提高顺铂对宫颈癌患者的治疗作用。     

肺腺癌A549/DDP细胞周期变化及其多药耐药性

用Fura-2/AM标记药物敏感的肺腺癌细胞A₅₄₉和抗顺铂药物的肺腺癌细胞A₅₄₉/DDP两种细胞胞内游离Ca²⁺,用碘化丙锭(PI)标记细胞DNA,检测其胞内Ca²⁺的变化及两种细胞增殖能力和细胞周期.实验结果表明,抗药性细胞株A₅₄₉/DDP胞浆内游离Ca²⁺的浓度仅为药物敏感细胞株A₅₄₉的1/3左右,同时前者的细胞增殖能力较后者明显增强,而且细胞周期也明显缩短.当用BAPTA-AM和EGTA或A₂₃₁₈₇和Thapsigargin处理细胞以降低或升高其胞内自由Ca²⁺浓度时可改变细胞的生长周期,二者也呈现明显差别.这些结果表明,对顺铂产生耐药性的人肺腺癌A₅₄₉/DDP细胞胞内Ca²⁺浓度的降低,可能影响细胞的增殖,缩短细胞的生长周期,特别是影响起决定作用的G1期,从而有利于肿瘤细胞多药耐药特性的维持.     

三氧化二砷下调MG-63骨肉瘤细胞IEX-1基因表达的转录调控机制研究

三氧化二砷(arsenic trioxide, As₂O₃)是中国传统中药砒霜的主要有效成分,最早应用于血液系统肿瘤的治疗,随后研究表明其对实体瘤也具有抑制细胞增殖并诱导凋亡的作用．早期研究发现,1.0 μmol/L的As₂O₃可以体外诱导骨肉瘤细胞系MG-63细胞凋亡,进一步的cDNA芯片分析、RT-PCR、RNA印迹证实细胞凋亡与As2O3干预后IEX-1基因表达下调有关．IEX-1为早期诱导应答基因,调节细胞生长和凋亡．通过荧光素酶分析,EMSA、蛋白质印迹等实验,发现As₂O₃干预骨肉瘤细胞系MG-63后能诱导p53蛋白表达上调,增加的p53蛋白通过与IEX-1的启动子结合,转录抑制IEX-1的转录,导致IEX-1基因表达下调．进一步证实了IEX-1与骨肉瘤的重要关系,同时也阐明As₂O₃诱导IEX-1基因表达下调的转录调控机制．     

Epstein-Barr virus efficiently immortalizes human B cells without neutralizing the function of p53.

Epstein-Barr virus (EBV) efficiently converts resting human B cells into actively cycling, immortal, lymphoblastoid cell lines (LCLs). Here we show that LCLs expressing the full complement of latent viral genes are very sensitive to DNA-damaging agents such as cisplatin. The response includes a rapid accumulation of the tumour suppressor protein p53 and induction of the cellular genes mdm2 and WAF1/p21. Although the levels of Bcl2 protein and Bax mRNA appear unaltered by the activation of p53, within 24 h the majority of cells undergo apoptosis. Over-expression of wild-type p53 in an LCL also resulted in apoptosis; this was preceded by the dephosphorylation of the retinoblastoma gene product, pRb. Primary resting B cells showed no response to cisplatin and even after drug treatment, p53 remained undetectable. However, after infection with EBV, p53 gene expression was induced to a similar level to that found in mitogen-activated B cells. When the physiologically activated primary B cells were exposed to cisplatin, although p53 accumulated as in LCLs, the outcome was growth-arrest rather than gross cell death. We conclude that, in contrast to the transformation of fibroblasts by adenovirus, SV40 or HPV, when B cells become activated and immortalized by EBV they are sensitized to the p53-mediated damage response. When the resulting LCLs are treated with genotoxic agents such as cisplatin, they are unable to arrest like normal cells because they are driven to proliferate by EBV and consequently undergo apoptosis.     

The residues between the two transformation effector sites of Epstein-Barr virus latent membrane protein 1 are not critical for B-lymphocyte growth transformation

Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) is essential for EBV-mediated transformation of primary B lymphocytes. LMP1 spontaneously aggregates in the plasma membrane and enables two transformation effector sites (TES1 and TES2) within the 200-amino-acid cytoplasmic carboxyl terminus to constitutively engage the tumor necrosis factor receptor (TNFR)-associated factors TRAF1, TRAF2, TRAF3, and TRAF5 and the TNFR-associated death domain proteins TRADD and RIP, thereby activating NF-kappaB and c-Jun N-terminal kinase (JNK). To investigate the importance of the 60% of the LMP1 carboxyl terminus that lies between the TES1-TRAF and TES2-TRADD and -RIP binding sites, an EBV recombinant was made that contains a specific deletion of LMP1 codons 232 to 351. Surprisingly, the deletion mutant was similar to wild-type (wt) LMP1 EBV recombinants in its efficiency in transforming primary B lymphocytes into lymphoblastoid cell lines (LCLs). Mutant and wt EBV-transformed LCLs were similarly efficient in long-term outgrowth and in regrowth after endpoint dilution. Mutant and wt LMP1 proteins were also similar in their constitutive association with TRAF1, TRAF2, TRAF3, TRADD, and RIP. Mutant and wt EBV-transformed LCLs were similar in steady-state levels of Bcl2, JNK, and activated JNK proteins. The wt phenotype of recombinants with LMP1 codons 232 to 351 deleted further demarcates TES1 and TES2, underscores their central importance in B-lymphocyte growth transformation, and provides a new perspective on LMP1 sequence variation between TES1 and TES2.     

Differential Gene Expression Patterns of EBV Infected EBNA-3A Positive and Negative Human B Lymphocytes

The genome of Epstein-Barr virus (EBV) encodes 86 proteins, but only a limited set is expressed in EBV–growth transformed B cells, termed lymphoblastoid cell lines (LCLs). These cells proliferate via the concerted action of EBV nuclear antigens (EBNAs) and latent membrane proteins (LMPs), some of which are rate limiting to establish a stable homeostasis of growth promoting and anti-apoptotic activities. We show here that EBV mutants, which lack the EBNA-3A gene, are impaired but can still initiate cell cycle entry and proliferation of primary human B cells in contrast to an EBNA-2 deficient mutant virus. Surprisingly, and in contrast to previous reports, these viral mutants are attenuated in growth transformation assays but give rise to permanently growing EBNA-3A negative B cell lines which exhibit reduced proliferation rates and elevated levels of apoptosis. Expression profiles of EBNA-3A deficient LCLs are characterized by 129 down-regulated and 167 up-regulated genes, which are significantly enriched for genes involved in apoptotic processes or cell cycle progression like the tumor suppressor gene p16/INK4A, or might contribute to essential steps of the viral life cycle in the infected host. In addition, EBNA-3A cellular target genes remarkably overlap with previously identified targets of EBNA-2. This study comprises the first genome wide expression profiles of EBNA-3A target genes generated within the complex network of viral proteins of the growth transformed B cell and permits a more detailed understanding of EBNA-3A''s function and contribution to viral pathogenesis.     

Differences in B cell growth phenotype reflect novel patterns of Epstein-Barr virus latent gene expression in Burkitt''s lymphoma cells.

Recently established Epstein-Barr virus (EBV)-positive Burkitt's lymphoma (BL) cell lines, carrying chromosomal translocations indicative of their malignant origin, have been monitored for their degree of in vitro progression towards a more 'lymphoblastoid' cell surface phenotype and growth pattern, and for their expression of three EBV latent gene products which are constitutively present in all virus-transformed normal lymphoblastoid cell lines (LCLs). BL cell lines which stably retained the original tumour biopsy phenotype on serial passage were all positive for the nuclear antigen EBNA 1 but did not express detectable amounts of two other 'transforming' proteins, EBNA 2 and the latent membrane protein (LMP). This novel pattern of EBV gene expression was also observed on direct analysis of BL biopsy tissue. All three viral proteins became detectable, however, in BL cell lines which had progressed towards a more LCL-like phenotype in vitro. This work establishes a link between B cell phenotype and the accompanying pattern of EBV latent gene expression, and identifies a novel type of EBV:cell interaction which may be unique to BL cells.     

The Epstein-Barr virus (EBV)-induced tumor suppressor microRNA MiR-34a is growth promoting in EBV-infected B cells

Epstein-Barr virus (EBV) infection of primary human B cells drives their indefinite proliferation into lymphoblastoid cell lines (LCLs). B cell immortalization depends on expression of viral latency genes, as well as the regulation of host genes. Given the important role of microRNAs (miRNAs) in regulating fundamental cellular processes, in this study, we assayed changes in host miRNA expression during primary B cell infection by EBV. We observed and validated dynamic changes in several miRNAs from early proliferation through immortalization; oncogenic miRNAs were induced, and tumor suppressor miRNAs were largely repressed. However, one miRNA described as a p53-targeted tumor suppressor, miR-34a, was strongly induced by EBV infection and expressed in many EBV and Kaposi's sarcoma-associated herpesvirus (KSHV)-infected lymphoma cell lines. EBV latent membrane protein 1 (LMP1) was sufficient to induce miR-34a requiring downstream NF-κB activation but independent of functional p53. Furthermore, overexpression of miR-34a was not toxic in several B lymphoma cell lines, and inhibition of miR-34a impaired the growth of EBV-transformed cells. This study identifies a progrowth role for a tumor-suppressive miRNA in oncogenic-virus-mediated transformation, highlighting the importance of studying miRNA function in different cellular contexts.     

An Epstein-Barr virus that expresses only the first 231 LMP1 amino acids efficiently initiates primary B-lymphocyte growth transformation

An Epstein-Barr virus (EBV) recombinant (MS231) that expresses the first 231 amino acids (aa) of LMP1 and is truncated 155 aa before the carboxyl terminus transformed resting B lymphocytes into lymphoblastoid cell lines (LCLs) only when the infected cells were grown on fibroblast feeder cells (K. M. Kaye et al., J. Virol. 69:675-683, 1995). Higher-titer MS231 virus has now been compared to wild-type (WT) EBV recombinants for the ability to cause resting primary B-lymphocyte transformation. Unexpectedly, MS231 is as potent as WT EBV recombinants in causing infected B lymphocytes to proliferate in culture for up to 5 weeks. When more than one transforming event is initiated in a microwell, the MS231 recombinant supports efficient long-term LCL outgrowth and fibroblast feeder cells are not required. However, with limited virus input, MS231-infected cells differed in their growth from WT virus-infected cells as early as 6 weeks after infection. In contrast to WT virus-infected cells, most MS231-infected cells could not be grown into long-term LCLs. Thus, the LMP1 amino-terminal 231 aa are sufficient for initial growth transformation but the carboxyl-terminal 155 aa are necessary for efficient long-term outgrowth. Despite the absence of the carboxyl-terminal 155 aa, MS231- and WT-transformed LCLs are similar in latent EBV gene expression, in ICAM-1 and CD23 expression, and in NF-kappaB and c-jun N-terminal kinase activation. MS231 recombinant-infected LCLs, however, require 16- to 64-fold higher cell density than WT-infected LCLs for regrowth after limiting dilution. These data indicate that the LMP1 carboxyl-terminal 155 aa are important for growth at lower cell density and appear to reduce dependence on paracrine growth factors.