A novel human lymphokine that inhibits haematopoietic progenitor cell proliferation

T lymphocytes in culture synthesize and secrete a variety of factors that activate and guide the differentiation, replication and maturation of haematopoietic cells in vitro. Malignant T-cell lines as well as T-cell hybridomas producing several of these factors have been established. We report here a factor produced by a human cell line that exerts a potent inhibitory effect on the growth of bone marrow progenitor cells. The properties of this factor, which we have termed colony-inhibiting lymphokine ( CIL ), differ from other inhibitors of haematopoietic progenitor cell proliferation, but resemble those of a T-cell-derived factor causally linked with some cases of severe aplastic anaemia in humans. Sensitivity of cells to this factor appears to correlate positively with expression of HLA-DR surface antigens.     

Expression of a transfected human c-myc oncogene inhibits differentiation of a mouse erythroleukaemia cell line

The Friend-virus-derived mouse erythroleukaemia (MEL) cell lines represent transformed early erythroid precursors that can be induced to differentiate into more mature erythroid cells by a variety of agents including dimethyl sulphoxide (DMSO). There is a latent period of 12 hours after inducer is added, when 80-90% of the cells become irreversibly committed to the differentiation programme, undergoing several rounds of cell division before permanently ceasing to replicate. After DMSO induction, a biphasic decline in steady-state levels of c-myc and c-myb messenger RNAs occurs. Following the initial decrease in c-myc mRNA expression, the subsequent increase occurs in, and is restricted to, the G1 phase of the cell cycle. We sought to determine whether the down-regulation is a necessary step in chemically induced differentiation. Experiments reported here indicate that expression in MEL cells of a transfected human c-myc gene inhibits the terminal differentiation process.     

Parthenolide inhibits proliferation of vascular smooth muscle cells through induction of G0/G1 phase cell cycle arrest

Objective: This study is to determine the effect of the natural product parthenolide, a sesquiterpene lactone isolated from extracts of the herb Tanacetum parthenium, on the proliferation of vascular smooth muscle cells (VSMCs). Methods: Rat aortic VSMCs were isolated and cultured in vitro, and treated with different concentrations of parthenolide (10, 20 and 30 μmol/L). [³H]thymidine incorporation was used as an index of cell proliferation. Cell cycle progression and distribution were determined by flow cytometric analysis. Furthermore, the expression of several regulatory proteins relevant to VSMC proliferation including IκBα, cyclooxygenase-2 (Cox-2), p21, and p27 was examined to investigate the potential molecular mechanism. Results: Treatment with parthenolide significantly decreased the [³H]thymidine incorporation into DNA by 30%~56% relative to control values in a dose-dependent manner (P<0.05). Addition of parthenolide also increased cell population at G₀/G₁ phase by 19.2%~65.7% (P<0.05) and decreased cell population at S phase by 50.7%~84.8% (P<0.05), which is consistent with its stimulatory effects on p21 and p27. In addition, parthenolide also increased IκBα expression and reduced Cox-2 expression in a time-dependent manner. Conclusion: Our results show that parthenolide significantly inhibits the VSMC proliferation by inducing G₀/G₁ cell cycle arrest. IκBα and Cox-2 are likely involved in such inhibitory effect of parthenolide on VSMC proliferation. These findings warrant further investigation on potential therapeutic implications of parthenolide on VSMC proliferation in vivo.     

Dual regulatory effects of resveratrol on activation of NF-kB and cell proliferation in human embryonal kidney 293 cells

Resveratrol (3,4 ,5-trihydroxystilbene, Res), a naturally occurring polyphenol, was first detected in grapevines (Vinis vitifera) in 1976[1]. It is also found in various fruits, vegetables and some other plants. It is abundant in grapes and the root of Polygonum cuspidatum, which is an im-portant constituent of traditional Chinese medicine. The concentration of Res in red wine reaches 2×10?6―4×10?5 mol/L. Res has been shown to have antioxidant properties, anti-inflammatory effect, estrog…     

Amplification of specific DNA sequences correlates with multi-drug resistance in Chinese hamster cells

Mammalian cells selected for resistance to certain cytotoxic drugs frequently develop cross-resistance to a broad spectrum of other drugs unrelated in structure to the original selective agent. This phenomenon constitutes a major problem in cancer chemotherapy. Multi-drug resistance arises from decreased intracellular drug accumulation, apparently due to an alteration of the plasma membrane. The observation of double minute chromosomes or homogeneously staining regions in some of the multi-drug-resistant cell lines suggests that gene amplification underlies this phenomenon. We have used the technique of DNA renaturation in agarose gels to detect, compare and clone amplified DNA sequences in Adriamycin- and colchicine-resistant sublines of Chinese hamster cells. We show that both Adriamycin- and colchicine-resistant cells contain amplified DNA fragments, some of which are amplified in both of these independently derived cell lines. Furthermore, loss of the multi-drug resistance phenotype on growth in the absence of drugs correlates with the loss of amplified DNA. These results strongly suggest that the DNA sequences which are amplified in common in multi-drug-resistant cell lines include the gene(s) responsible for a common mechanism of multi-drug resistance in these cells. We have cloned one of the commonly amplified DNA fragments and show that the degree of amplification of this fragment in the cells correlates with the degree of their drug resistance.     

Tumour necrosis factor alpha stimulates resorption and inhibits synthesis of proteoglycan in cartilage

During inflammatory reactions, activated leukocytes are thought to produce a variety of small proteins (cytokines) that influence the behaviour of other cells (including other leukocytes). Of these substances, which include the interleukins, interferons and tumour necrosis factors (TNFs), interleukin-1 (IL-1) has been considered potentially a most important inflammatory mediator because of its wide range of effects. In vivo it is pyrogenic and promotes the acute phase response; in vitro it activates lymphocytes and stimulates resorption of cartilage and bone. Cartilage resorption is a major feature of inflammatory diseases such as rheumatoid arthritis, and IL-1 is the only cytokine hitherto known to promote it. TNFs are characterized by their effects on tumours and cytotoxicity to transformed cells, but share some actions with IL-1. I report here that recombinant human TNF alpha stimulates resorption and inhibits synthesis of proteoglycan in explants of cartilage. Its action is similar to and additive with IL-1, and it is a second macrophage-derived cytokine whose production in rheumatoid arthritis, or inflammation generally, could contribute to tissue destruction.     

Expression of active human factor IX in transfected cells

Factor IX is the precursor of a serine protease that functions in the intrinsic blood clotting pathway. Deficiencies in this plasma glycoprotein result in haemophilia B (or Christmas disease) and occur in about 1 in 30,000 males. Patients are currently treated with fresh frozen plasma or prothrombin complex concentrates prepared from pooled plasma from normal individuals. There are several problems with this method of treatment, including the probable exposure of the patients to contaminants such as the viral agents responsible for hepatitis and AIDS (acquired immune deficiency syndrome). As a first step towards an alternative source of pure human factor IX, we report here on the use of recombinant DNA techniques to produce biologically active factor IX in cultured mammalian cells. Stable cell lines were produced by cotransfecting a baby hamster kidney (BHK) cell line with a plasmid containing a gene for factor IX and a plasmid containing a selectable marker. Protein secreted by these cell lines reduces the clotting time of plasma from factor IX-deficient patients. We present additional evidence that this protein is authentic human factor IX.     

Epstein-Barr virus latent membrane protein inhibits human epithelial cell differentiation

Epstein-Barr virus (EBV), a human herpesvirus, is strongly linked with two relatively rare forms of B-cell lymphoma and with a much more prevalent epithelial malignancy, undifferentiated nasopharyngeal carcinoma (NPC). The availability of suitable culture systems has allowed detailed analysis of EBV-induced growth transformation in B lymphocytes, but little is known about the virus--epithelial cell interaction or about the possible effector role of viral proteins in the pathogenesis of NPC. Here we describe an experimental system to monitor the effects of introduced viral or cellular genes upon human epithelial cell growth and differentiation. We transfected a human epithelial cell line, which retains several features of normal keratinocyte behaviour in vitro, with the EBV gene encoding latent membrane protein (LMP), one of only two viral proteins known to be expressed in NPC cells in vivo. LMP expression was accompanied by changes in the epithelial cell surface phenotype, mimicking surface changes observed in NPC cells, and by severe impairment of the cellular response to differentiation signals. The ability of LMP to inhibit terminal differentiation indicates a mechanism whereby EBV infection of squamous epithelium could contribute to the multi-step pathogenesis of NPC.     

红景天苷抑制Hcy诱导的血管内皮细胞氧化应激损伤的实验研究

研究红景天苷(SAL)对同型半胱氨酸(Hcy)诱导体外培养的人脐静脉内皮细胞(HUVECs)氧化应激损伤的保护作用及可能机制.选择3-8代生长状态良好的HUVECs用于实验,采用SAL预孵育HUVECs 2h后,再加入Hcy(1mmol/L)共孵育12 h诱导内皮细胞氧化应激损伤.采用MTT和LDH法分析细胞损伤,荧光...     

MSH2 is required for cell proliferation, cell cycle control and cell invasiveness in colorectal cancer cells

We have investigated the role of MSH2,a mismatch repair gene in cell proliferation,cell cycle control and cell invasiveness in the SW480 human colorectal cancer cell line.RNAi-mediated inhibition of MSH2 expression was achieved using MSH2 shRNA lentiviral expression vectors.Effective knockdown of endogenous MSH2 expression was determined by real-time PCR analysis.The most efficient MSH2 knockdown vector was selected for subsequent studies using SW480 cells.Endogenous MSH2 mRNA levels decreased after lentiviral delivery of the MSH2-RNAi,indicating efficient silencing of MSH2 expression in SW480 cells.Cell proliferation,cell cycle progression and cell invasiveness were quantified by MTT assays,flow cytometry and transwell assays,respectively.RNAi-mediated inhibition of MSH2 expression in SW480 cells resulted in decreased cell proliferation,cell cycle arrest at the G0/G1 phase and decreased cell invasiveness.Taken together,these results provide evidence that MSH2 stimulates cell proliferation,promotes cell cycle progression and positively regulates cell invasiveness.     

大蒜多糖抗氧化活性及其对PC12细胞增殖的影响

目的: 检测大蒜多糖对大鼠嗜铬瘤细胞株(pheochromocytoma cells, PC12)增殖的影响和对经过氧化氢(H2O2)诱导损伤的PC12细胞的保护作用.方法:应用四氮唑蓝(MTT)比色法检测大蒜多糖对细胞增殖的影响;建立H2O2致PC12细胞损伤模型,于倒置相差显微镜下观察细胞形态的变化;化学比色法测定乳酸脱氢酶(LDH)释放量及细胞内和细胞培养上清液中丙二醛(MDA)含量和超氧化物歧化酶(SOD)的活性.结果:大蒜多糖各剂量组均能显著提高正常PC12细胞的存活数,大蒜多糖各剂量组均能有效对抗由25 μmol/L H2O2引起的细胞存活率下降和细胞凋亡,可明显改善细胞形态的衰变,显著降低LDH释放量和细胞培养液及细胞内的MDA含量,提高SOD活性.结论: 大蒜多糖促进正常PC12细胞增殖;且对H2O2诱导PC12细胞损伤具有保护作用,其作用机制可能与提高PC12细胞的抗氧化能力有关.     

Androgen regulation of cell proliferation and expression of viral sequences in mouse mammary tumour cells

The role of steroids in promoting cell proliferation is well established but the molecular mechanisms are not clear. The S115 mouse mammary tumour cell line provides a model system for molecular studies in vitro in that it exhibits in tissue culture both a positive proliferative response to androgens and a change from a transformed phenotype in the presence of androgen to a normal phenotype when androgen is removed. We have considered here the possible involvement of mouse mammary tumour virus (MMTV) in these processes. We have demonstrated the presence in S115 cells of MMTV-related sequences which are transcribed into RNA only in the long-term presence of androgen. Prolonged culture in the absence of androgen, which results in loss of proliferative response to androgen, is accompanied by loss of MMTV-related RNA and increased methylation of MMTV-related sequences.     

野西瓜水溶性生物碱抑制HepG-2增殖作用

研究野西瓜生物碱的抗肿瘤作用.采用MTT实验观察野西瓜水溶性生物碱的体外抗肿瘤作用,采用流式细胞仪测定野西瓜水溶性生物碱对肿瘤细胞凋亡及细胞周期的影响. 10、50、100、150、200、300 μg/mL的野西瓜水溶性生物碱作用于HepG-2细胞72 h后均可不同程度的抑制HepG-2细胞的增殖,其中野西瓜水溶性生物碱IC50为171.5 μg/mL;作用48 h后出现凋亡形态;180 μg/mL、360 μg/mL的野西瓜水溶性生物碱作用48 h时出现细胞凋亡;周期分布发生改变.结果表明,野西瓜水溶性生物碱具有抗肿瘤作用.     

重楼活性单体PP-26抑制结肠癌SW620细胞增殖并诱导细胞凋亡

目的:探讨重楼活性单体PP-26对人结肠癌SW620细胞增殖抑制作用及其机制.方法:采用噻唑蓝(MTT)法和克隆形成抑制实验观察不同浓度的重楼单体PP-26对人结肠癌SW620细胞增殖抑制作用;PI单染及Annexin V-FITC/PI双染流式细胞术检测细胞周期变化及细胞凋亡水平;Western blotting检测PP-26对细胞周期、细胞凋亡相关蛋白以及Akt和ERK蛋白的表达.结果:与正常肝LO2细胞相比,重楼单体PP-26能显著抑制SW620细胞的生长,作用呈剂量-效应关系;随着PP-26浓度的增加,细胞克隆形成逐渐减少,与细胞对照组相比有显著差异;不同浓度PP-26作用后,细胞阻滞于G1期;PP-26作用细胞24 h后,CDK4、CDK6表达下降,P15、cyclin D1表达增加;不同浓度PP-26作用后,细胞晚期凋亡率增加,随浓度增加有上升趋势;PP-26作用细胞24 h后,线粒体相关凋亡信号通路蛋白Caspase-9、Caspase-3表达下降,PARP切割条带增加,细胞促凋亡蛋白Bax的表达增加,抗凋亡蛋白Bcl-2和Bcl-x L减少,p-Akt和p-ERK蛋白表达均下降.结论:重楼活性单体PP-26通过上调p15促进结肠癌SW620细胞阻滞于G1期,通过抑制P13K/Akt信号通路及ERK信号通路,活化线粒体凋亡通路,诱导细胞凋亡.