HSVTK gene therapy for carcinoembryonic antigen-producing human lung cancer cells

The long-term success of gene therapy for cancer relies heavily on the development of effective targeting systems. We investigate the possibility of targeted gene therapy using promoter of carcinoembryonic antigen (CEA) gene. By using luciferase reporter gene, we found that CEA promoter exhibit 16 times high activity in CEA-producing lung cancer cells, A549 than in nonproducing cells, Hela. We also constructed a recombinant expression plasmid pCEATK, in which CEA promoter drives the effector gene, thymidine kinase gene of Herpes Simplex Virus (HSVTK). A549 cells transfected with pCEATK became 865 times more sensitive to ganciclovir (GCV) than the control cells. However, Hela cells transfected with this plasmid remained resistant to GCV. These data indicate the potential for targeted gene therapy using the CEA promoter against CEA-producing tumor cells, such as lung cancer cells. Foundation item: Supported by the National Natural Science Foundation of China Natural Science Foundation of Hubei Province Biography: XIAO Geng-fu(1966-), male, phD graduate candidate, Lecturer.     

PKA和PKC对HeLa细胞G_2/M/G_1进程的影响

为了研究PKA和PKC对HeLa细胞G2 →M期和M→G1期进程的影响 ,用PKA和PKC抑制剂分别处理同步的G2 期和M期的HeLa细胞后 ,测定了细胞有丝分裂指数和PKA ,PKC与CDC2激酶的活性 .结果表明 ,PKAⅢ型抑制剂在促进HeLa细胞G2 /M /G1进程的同时 ,刺激了PKC的活性 ,反之 ,PKC的抑制剂GF 10 92 0 3X在阻抑HeLa细胞G2 /M /G1进程的同时 ,激活了PKA的活性 ,与其相关的CDC2激酶活性也发生了相应的变化 .实验表明 ,PKA和PKC分别负调和正调HeLa细胞G2 /M/G1进程 ,两者表现出拮抗关系 .     

大鼠实验性甲亢心肌内肌酸激酶变化的免疫组化研究

以药物诱导的方法建立了大鼠实验性甲亢模型，并以该模型心肌切片进行了免疫组化染色检测肌酸激酶。结果显示，随着甲亢病程的延长，着色呈现酶含量降低，酶活性减少的变化。实验证实甲亢时心肌呈现渐进性缺血过程。     

Long-Term Exposure to High Corticosterone Levels Inducing a Decrease of Adenylate Kinase 1 Activity

Corticosterone, a principal glucocorticoid synthesized in the rodent adrenal cortex, can be cumulatively toxic to hippocampal neurons, the cause of which is not known. The present study determined whether the cytosol adenylate kinase (AK) system was involved in the neuronal damage induced by long-term exposure to high corticosterone levels. We investigated the effects of long-term exposure to high corticosterone levels on AK1 activity, AK1 mRNA expression, and energy levels in cultured hippocampal neurons. The results show that long-term exposure to high corticosterone levels induces a reduction of the cultured hippocampal neuron viability, significantly reduces energy levels, and causes a time-dependant reduction of the AK1 activity. These findings indicate that changes in the AK system might be the mechanism underlying neuronal damage induced by long-term exposure to high corticosterone levels.     

生长抑素类似物通过细胞生长抑制和细胞溶解途径以SSTR2依赖的方式抑制癌细胞增殖

通过在两个具有不同内源性生长抑素受体(SSTR)表达谱的癌细胞系capan-2和A549中过表达SSTR2,用生长抑素类似物(SSA)奥曲肽或者伐普肽(RC-160)处理实验组的癌细胞,对过表达SSTR2和生长抑素类似物的抗肿瘤增殖效果通过细胞增殖实验进行了研究,而且进一步通过免疫印记的方法研究了SSA/SSTR2涉及的信号通路.结果表明,过表达SSTR2明显抑制了内源性SSTR2表达阳性和阴性癌细胞增殖,而单独使用奥曲肽或者伐普肽对癌细胞增殖影响甚微.然而,在过表达SSTR2的癌细胞中奥曲肽或者伐普肽则可明显抑制癌细胞的增殖,而且具有剂量依赖性.深入研究发现SSA/SSTR2是通过细胞周期阻滞和促凋亡来抑制细胞增殖.结果提示SSTR2可作为候选基因用于本身SSTR2表达阳性或阴性肿瘤的基因治疗,细胞内SSTR2的水平可能是影响肿瘤进程和SSA治疗效果的一个关键因素.     

ERK_(1,2)抑制剂联合5-FU对B16细胞增殖和凋亡的影响

目的:观察ERK_(1,2)抑制剂联合5-Fu对B16细胞增殖和凋亡的影响,并探讨作用机制.方法:用MTT法观察ERK_(1,2)抑制剂、5-FU和联合用药对细胞增殖的抑制作用,流式细胞仪检测细胞凋亡率,用RT-PCR观察ERK_(1,2)抑制剂、5-Fu和联合用药对bcl-2和caspase-9的表达的影响.结果:ERK_(1,2)抑制剂联合5-Fu组在抑制细胞增殖,诱导细胞凋亡,均较对照组、单独用药组作用增强,并且下调bcl-2和上调easpase-9的表达.结论:ERK_(1,2)抑制剂联合5-Fu有协同抑制B16细胞增殖,促进凋亡的作用,其机制可能与诱导细胞凋亡,下调bcl-2和上调caspase-9的表达有关.     

Src与FAK的相互作用及其在心肌肥大信号转导中的作用

心肌细胞肥大是许多心血管疾病常见的细胞形态学改变，其表型特征由其核内基因表达模式决定。Src和黏着斑激酶（focal adhesion kinase，FAK）作为胞质蛋白酪氨酸激酶是整合素信号的早期调控因子，是多细胞生物体所必须的。本文主要综述Src激酶家族及FAK在心肌肥大中信号转导的最新进展。     

Separate functional features of proinsulin C-peptide

Proinsulin C-peptide influences a number of physiological parameters in addition to its well-established role in the parent proinsulin molecule. It is of interest as a candidate for future co-replacement therapy with insulin for patients with diabetes mellitus type 1, but specific receptors have not been identified and additional correlation with functional effects is desirable. Based on comparisons of 22 mammalian proinsulin variants, we have constructed analogues for activity studies, choosing phosphorylation of mitogen-activated protein kinases (MAPKs) in Swiss 3T3 fibroblasts for functional measurements. In this manner, we find that effective phosphorylation of MAPKs is promoted by the presence of conserved glutamic acid residues at positions 3, 11 and 27 of C-peptide and by the presence of helix-promoting residues in the N-terminal segment. Previous findings have ascribed functional roles to the C-terminal pentapeptide segment, and all results combined therefore now show the importance of different segments, suggesting that C-peptide interactions are complex or multiple.Received 2 May 2005; received after revision 9 June 2005; accepted 13 June 2005     

Oxidation and tyrosine phosphorylation: synergistic or antagonistic cues in protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs) have been generally recognised as key modulators of cell proliferation, differentiation, adhesion and motility. During signalling, several PTPs undergo two posttranslational modifications that greatly affect their enzymatic activity: tyrosine phosphorylation and cysteine oxidation. Although these modifications share their reversibility depending on the intracellular environment, their effects on enzymatic activity are opposite, tyrosine phosphorylation being correlated to enzyme activation and thiol oxidation to complete inactivation. Several papers have suggested that both these modifications occur in response to the same stimuli i.e. cell proliferation induced by numerous growth factors and cytokines. Conversely, the possibility that these two regulation mechanisms act simultaneously on PTPs has not been established and very few reports investigated this dual regulation of PTPs. To underline the relevance of the question, we discuss several possibilities: (i) that tyrosine phosphorylation and cysteine oxidation of PTPs may share the same target molecules but with different kinetics; (ii) that PTP phosphorylation and oxidation may take place on different subcellular pools of the same protein and (iii) that these two modifications, although having divergent effects on enzyme activity, cooperate in the integrated and coordinated function of PTPs during receptor tyrosine kinase signalling. We believe that our perspective will open new perspectives on an ancient problem – the apparent contradiction of opposing enzymatic regulation of many PTPs – thus clarifying their role as positive or negative transducers (or both) of many extracellular stimuli.Received 11 October 2004; received after revision 26 January 2005; accepted 10 February 2005 Available online 29 March 2005     

The renal plumbing system: aquaporin water channels

Aquaporins are channels that facilitate movement of water across lipid bilayers. They are expressed in multiple tissues and are essential for regulation of body water homeostasis. The kidney is the main organ responsible for this regulation, and at least seven aquaporins are expressed at distinct sites in the kidney. Aquaporin expression correlates with observed water permeability of each nephron segment: proximal tubule and descending thin limb of Henle have constitutive high water permeability due to expression of AQP1, whereas collecting duct water permeability is tightly regulated by the antidiuretic hormone vasopressin via regulation of AQP2. This review aims at providing insight into renal aquaporins, with special focus on AQP2.Received 9 December 2004; received after revision 8 April 2005; accepted 11 April 2005