GADD45β基因表达诱导对不同p53状态的肝癌细胞作用

目的：体外合成GADD45β基因全序列表达质粒后，研究GADD45β基因表达诱导对呈不同p53状态的肝癌细胞的作用及可能机制。方法：采用RT-PCR法获得GADD45β基因全序列，插入pDrive穿梭克隆载体和pIRES2-EGFP荧光表达载体后大量扩增获得DNA，结合p53全基因表达质粒pp53-EGFP转染HepG2、Hep3B细胞后，以[^3H]胸腺嘧啶脱氧核苷掺入法(^3H—Tdr)和细胞克隆形成法分析DNA合成变化及细胞生长能力；以双抗体夹心ELISA法测定TGF-β1表达变化。结果：成功合成GADD45β基因全序列和表达质粒，通过流式细胞仪收集转染阳性的荧光表达细胞能显著提高转染效率；转染GADD45β后．具有野生型p53基因的HepG2细胞的细胞克隆形成能力和DNA合成能力明显受到抑制，细胞凋亡明显增加，TGF-β1的表达亦明显受抑。与之相反，缺失p53基因的Hep3B需要同时共转染p53基因后，方出现抑制效应。结论：GADD45β基因能够有效抑制肝癌细胞的生长．其功能需要完整p53基因的辅助和(或)调控。GADD45表达和（或)功能异常，导致p53介导的DNA损伤修复途径异常或阻断，是肝脏细胞恶性转化及形成肿瘤的可能机制。     

Wild-type p53 regulates human ribonucleotide reductase by protein-protein interaction with p53R2 as well as hRRM2 subunits

Ribonucleotide reductase (RR) plays a key role in the synthesis of DNA and is the only enzyme responsible for the reduction of ribonucleotides to their corresponding deoxyribonucleotides, providing a balanced supply of precursors for DNA synthesis and repair. There are three known human RR subunits, hRRM1, hRRM2, and p53R2, which is encoded by a p53 target gene. It is not clear whether p53 and RR can directly interact at the protein level to regulate DNA repair. It is also not known where deoxyribonucleotides are synthesized in the cell. In coimmunoprecipitation experiments, we found that hRRM2 and p53R2, but not hRRM1, bound to p53 in KB cells, which express wild-type p53. Moreover, in response to UV irradiation, both p53R2 and hRRM2 were released from p53 and shifted to bind hRRM1. Confocal microscopy confirmed the colocalization of p53 with p53R2 and hRRM2 and the translocation of hRRM1, p53R2 and hRRM2 from the cytoplasm to the nucleus after UV treatment. An in vivo RR activity assay showed that the kinetic profile of increased RR activity was consistent with the accumulation of RR subunits in the nucleus. The ability of p53R2 and hRRM2 to shift from binding p53 to hRRM1 in response to UV irradiation was deficient in the presence of mutant p53. Moreover, in cells overexpressing hRRM2, binding of p53R2 to p53 decreased, whereas binding to hRRM1 increased. Our results suggest that wild-type p53 directly interacts with both p53R2 and hRRM2. In response to UV irradiation, p53R2 and hRRM2 dissociate from p53 and p53R2, and hRRM2 and hRRM1 transfer to the nucleus and form an active RR complex to provide dNDPs for DNA repair. Therefore, the direct interaction of p53 with p53R2 and hRRM2 and the nuclear accumulation of RR subunits after UV exposure might play a pivotal role in DNA repair.     

人皮肤真性组织细胞性淋巴瘤体外细胞株Mei的建立及其生物学特性

本文报道从一例人皮肤真性组织细胞性淋巴瘤体外长期(11个月)培养建成Mei细胞株的建株过程。该细胞株具有如下特征:患者经临床及实验室检查确诊为皮肤真性组织细胞性淋巴瘤;细胞化学染色ANAE等显示弥漫性阳性;抗单核细胞单克隆抗体Liu M_(1～7)呈阳性反应;细胞凝集素受体ConA、RCA及UEA是阳性反应而T细胞促分裂原——花生凝集素受体则呈阴性反应;Mei细胞生长稳定,细胞增殖存第3天达高峰,第4天分裂指数为20%;裸小鼠皮下接种的移碹率为100％;细胞染色体众数是64条人类染色体,核型稳定。     

An increase of cytochrome C oxidase mediated disruption of gemcitabine incorporation into DNA in a resistant KB clone

Mechanistic aberrations leading to Gemcitabine (2',2'-dFdCyd,2,2-difluorodeoxycytidine, Gem) resistance may include alteration in its transport, metabolism and incorporation into DNA. To explore the mechanism of Gem resistance, the restriction fragment differential display PCR (RFDD-PCR) was employed to compare the mRNA expression patterns of KBGem (Gem resistant), KBHURs (hydroxyurea resistant) and KBwt (parental KB cell). Nine gene fragments were overexpressed specifically in the KBGem clone. Sequencing and BLAST results showed that three fragments represent cytochrome C oxidase (CCOX, respiration complex IV) subunit III (CCOX3). The cDNA microarray confirmed that the mRNAs of CCOX and ATP synthase subunits were upregulated in KBGem as compared to KBwt and KBHURs. The increase in CCOX1 protein and activity led to the increase of free ATP concentration, which is consistent with the gene expression profile of KBGem. Furthermore, the sensitivity to Gem could be reversed by sodium azide, a CCOX inhibitor. Following the treatment of sodium azide, the cellular accumulation of [3H]-Gem increased in a dose (of azide)-dependent manner, which is associated with increase of [3H]-Gem incorporation into DNA in KBGem. In summary, an increase of CCOX activity and free ATP level may reduce the transport, metabolism and DNA incorporation of Gem, resulting in Gem resistance.     

Metastasis-suppressing potential of ribonucleotide reductase small subunit p53R2 in human cancer cells.

PURPOSE: Previous gene transfection studies have shown that the accumulation of human ribonucleotide reductase small subunit M2 (hRRM2) enhances cellular transformation, tumorigenesis, and malignancy potential. The latest identified small subunit p53R2 has 80% homology to hRRM2. Here, we investigate the role of p53R2 in cancer invasion and metastasis. EXPERIMENTAL DESIGN: The immunohistochemistry was conducted on a tissue array including 49 primary and 59 metastatic colon adenocarcinoma samples to determine the relationship between p53R2 expression and metastasis. A Matrigel invasive chamber was used to sort the highly invasive cells and to evaluate the invasion potential of p53R2. RESULTS: Univariate and multivariate analyses revealed that p53R2 is negatively related to the metastasis of colon adenocarcinoma samples (odds ratio, 0.23; P<0.05). The decrease of p53R2 is associated with cell invasion potential, which was observed in both p53 wild-type (KB) and mutant (PC-3 and Mia PaCa-2) cell lines. An increase in p53R2 expression by gene transfection significantly reduced the cellular invasion potential to 54% and 30% in KB and PC-3 cells, respectively, whereas inhibition of p53R2 by short interfering RNA resulted in a 3-fold increase in cell migration. CONCLUSIONS: Opposite regulation of hRRM2 and p53R2 in invasion potential might play a critical role in determining the invasion and metastasis phenotype in cancer cells. The expression level of ribonucleotide reductase small subunits may serve as a biomarker to predict the malignancy potential of human cancers in the future.     

S腺苷蛋氨酸对肝癌细胞中GADD45β基因的表达诱导及其机制研究

目的 初步明确肝癌细胞中特异性表达缺失的GADD45β基因近端启动子活性调控中心,并探讨S腺苷蛋氨酸对肝癌细胞HepG2中GADD45β表达的影响及可能机制.方法 以30～50个碱基的间隔,于体外人工合成GADD45β近端启动子序列(-618～-520),分别插入pGL3 basic荧光素表达质粒的荧光基因上游,以电穿孔法转染HepG2,根据启动子活性强度结合TRANSFAC数据库,分析可能存在的转录调节因子结合位点;实时荧光定量PCR比较S腺苷蛋氨酸作用前后HepG2细胞GADD45β表达,并在此基础上进一步比较S腺苷蛋氨酸对GADD45β启动子活性的诱导作用,探讨其可能作用机制,并为GADD45β近端启动子研究提供功能性证据.结果 GADD45β近端启动子中含有3个NF-kB转录调节因子与启动子结合位点(-602/-593、-581/-572、-537/-528);S腺苷蛋氨酸能明显诱导HepG2中GADD45β的表达,并呈现出剂量一效应的正相关关系,同时其能相应明显诱导NF-kB的启动子活性.结论 S腺苷蛋氨酸能明显诱导肝癌细胞中特异性缺失的GADD45β基因表达,增强转录调节因子NF-kB的活性水平是其可能的作用机制,该研究为S腺苷蛋氨酸的肝脏保护作用提供了新的实验依据.     

氟碳代血液的慢性毒性病理学研究

本文用临床通用剂量(20ml/kg,相当于成人一次使用1200ml)的氟碳代血液作慢性毒性病理学研究。狗在一次静脉注入本品后主要沉积在单核巨噬系统,并被固定和游离的组织细胞所吞噬,吞噬后的组织细胞转变为泡沫细胞。 注入后1月仍属潴留高峰,6月后除脾脏外各脏器均已基本排空并不留任何病理痕迹,12月后所有被检脏器在光镜下均已不能查见泡沫细胞,但在电镜下肝脾仍可偶见个别部位留有少量小泡状物质,作者认为此种极微量的潴留缺乏临床意义。 作者也认为氟碳代血液对靶细胞只是被吞噬和潴留,未出现任何明显病理学改变。 根据研究结果,作者认为本品属非原浆毒并为生物惰性物质,亦不存在由于本品在单核巨噬系统潴留而引起的继发性病理损害问题,并认为本剂量的临床应用是安全的。     

Structurally dependent redox property of ribonucleotide reductase subunit p53R2

p53R2 is a newly identified small subunit of ribonucleotide reductase (RR) and plays a key role in supplying precursors for DNA repair in a p53-dependent manner. Currently, we are studying the redox property, structure, and function of p53R2. In cell-free systems, p53R2 did not oxidize a reactive oxygen species (ROS) indicator carboxy-H2DCFDA, but another class I RR small subunit, hRRM2, did. Further studies showed that purified recombinant p53R2 protein has catalase activity, which breaks down H2O2. Overexpression of p53R2 reduced intracellular ROS and protected the mitochondrial membrane potential against oxidative stress, whereas overexpression of hRRM2 did not and resulted in a collapse of mitochondrial membrane potential. In a site-directed mutagenesis study, antioxidant activity was abrogated in p53R2 mutants Y331F, Y285F, Y49F, and Y241H, but not Y164F or Y164C. The fluorescence intensity in mutants oxidizing carboxy-H2DCFDA, in order from highest to lowest, was Y331F > Y285F > Y49F > Y241H > wild-type p53R2. This indicates that Y331, Y285, Y49, and Y241 in p53R2 are critical residues involved in scavenging ROS. Of interest, the ability to oxidize carboxy-H2DCFDA indicated by fluorescence intensity was negatively correlated with RR activity from wild-type p53R2, mutants Y331F, Y285F, and Y49F. Our findings suggest that p53R2 may play a key role in defending oxidative stress by scavenging ROS, and this antioxidant property is also important for its fundamental enzymatic activity.     

SUMOylation plays a role in gemcitabine- and bortezomib-induced cytotoxicity in human oropharyngeal carcinoma KB gemcitabine-resistant clone

Bortezomib, a novel dipeptide boronic acid proteasome inhibitor, has been shown in previous studies to be synergistic with gemcitabine; however, the molecular mechanisms are not fully understood. Because post-translational modification of proteins, such as ubiquitination and SUMOylation, plays a critical role in governing cellular homeostasis, we explored this further by treating human oropharyngeal carcinoma KB wild-type (KBwt) and gemcitabine-resistant (KBGem) cells with gemcitabine and bortezomib in a time-dependent and sequence-dependent manner. Treatment with bortezomib at 4 to 8 hours post-gemcitabine significantly induced cell death in KBwt cell lines. However, in KBGem cells, bortezomib alone was just as cytotoxic. Using reporter assays, nuclear factor-kappaB (NF-kappaB) activity was found to be 5-fold higher in KBGem cells than that in KBwt cells, and the combination treatment decreased NF-kappaB activity by 44% in KBwt cells and 28% in KBGem cells, respectively. By Western blot analyses, treatment with gemcitabine and bortezomib resulted in a cleavage of NF-kappaB in KBwt but not in KBGem cells. SUMOylation capacity was modulated by transducing KBwt and KBGem cells with lenti-SUMO-1 or the unconjugatable lenti-SUMO-1aa followed by drug treatment. The expression of cyclins A, D1, and E was differentially regulated by SUMOylation capacity in KBGem but not in KBwt cells. We report herein that the activation of NF-kappaB signaling plays a critical role in eliciting KBwt cell survival against gemcitabine, whereas the role of SUMOylation in modulating the steady-state levels of key cell cycle regulator proteins seems more significant in KBGem cells.     

厄贝沙坦胶囊溶出度测定方法的改进

目的：建立厄贝沙坦胶囊的溶出度测定方法。方法：照溶出度测定法（《中国药典》2010年版二部附录XC第一法）,以0.1 mol·L-1盐酸溶液为溶剂,转速为100 r·min-1;紫外分光光度法测定,测定波长为245 nm。结果：30 min内产品的溶出率达到75%以上,辅料对主药测定无干扰,厄贝沙坦线性范围为2.5025.00μg·ml-1（r=0.999 9）,回收率为100.5%（RSD=0.13%,n=9）。结论：本法操作简便、准确可靠,适用于厄贝沙坦胶囊的溶出度测定。