Transcriptional regulation of Rex1 (zfp42) in normal prostate epithelial cells and prostate cancer cells

The enormous regenerative capacity of the blood system to sustain functionally mature cells are generated from highly proliferative, short‐lived progenitors, which in turn arise from a rare population of pluripotent and self‐renewing hematopoietic stem cells (HSC). In the bone marrow, these stem cells are kept in a low proliferative, relatively quiescent state in close proximity to stromal cells and osteoblasts, forming specialized niches. The interaction in particular to bone is crucial to prevent exhaustion of HSCs from uncontrolled cell‐cycle entry and to excessive proliferation. In addition, the niche and its components protect stem cells from stress, such as accumulation of reactive oxygen species and DNA damage. One of the key issues is to identify conditions to increase the number of HSCs, either in vivo or during ex vivo growth cultures. This task has been very difficult to resolve and most attempts have been unsuccessful. However, the mechanistic insights to HSC self‐renewal and preservation are gradually increasing and there is now hope that future research will enable scientists and clinicians to modulate the process. In this review, we will focus on the molecular mechanisms of self‐renewal and HSC maintenance in the light of novel findings that HSCs reside at the lowest end of an oxygen gradient. Hypoxia appears to regulate hematopoiesis in the bone marrow by maintaining important HSC functions, such as cell cycle control, survival, metabolism, and protection against oxidative stress. To improve the therapeutic expansion of HSCs we need to learn more about the molecular mechanisms of hypoxia‐mediated regulation. J. Cell. Physiol. 222:17–22, 2010. © 2009 Wiley‐Liss, Inc.     

Influence of p53 expression on sensitivity of cancer cells to bleomycin

In this study, we determined whether p53 expression affected the sensitivity of non–small cell lung cancer (NSCLC) and colon cancer cells to bleomycin (BLM). Two human NSCLC cell lines (A549 expressing wild‐type p53 and p53‐null H1299) and two colon cancer cell lines (HCT116 p53+/+ and its p53 deficient subline HCT116 p53?/?) were subjected to treatment with BLM. Cells were treated with various concentrations of BLM, and cellular viability was assessed by formazan assay. To investigate the role of p53 in BLM sensitivity, we transduced cells with adenovirus with wild‐type p53, dominant‐negative p53, and GFP control, and analyzed the effect on cellular viability. Cells expressing wild‐type p53 were more sensitive to BLM than p53‐null cells in both NSCLC and colon cancer cells. Sensitivity to BLM of the cells with wild‐type p53 was reduced by overexpression of dominant‐negative p53, while BLM sensitivity of p53‐null cells was increased by wild‐type p53 in both NSCLC cells and colon cancer cells. In conclusion, our data show that p53 sensitizes all four cancer cells lines tested to BLM toxicity and overexpression of p53 confers sensitivity to the cytotoxic activity of the anticancer agent in p53‐null cells. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:260–269, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.20334     

Partitioning of Minimotifs Based on Function with Improved Prediction Accuracy

Background

Minimotifs are short contiguous peptide sequences in proteins that are known to have a function in at least one other protein. One of the principal limitations in minimotif prediction is that false positives limit the usefulness of this approach. As a step toward resolving this problem we have built, implemented, and tested a new data-driven algorithm that reduces false-positive predictions.

Methodology/Principal Findings

Certain domains and minimotifs are known to be strongly associated with a known cellular process or molecular function. Therefore, we hypothesized that by restricting minimotif predictions to those where the minimotif containing protein and target protein have a related cellular or molecular function, the prediction is more likely to be accurate. This filter was implemented in Minimotif Miner using function annotations from the Gene Ontology. We have also combined two filters that are based on entirely different principles and this combined filter has a better predictability than the individual components.

Conclusions/Significance

Testing these functional filters on known and random minimotifs has revealed that they are capable of separating true motifs from false positives. In particular, for the cellular function filter, the percentage of known minimotifs that are not removed by the filter is ∼4.6 times that of random minimotifs. For the molecular function filter this ratio is ∼2.9. These results, together with the comparison with the published frequency score filter, strongly suggest that the new filters differentiate true motifs from random background with good confidence. A combination of the function filters and the frequency score filter performs better than these two individual filters.     

Lysophosphatidic acid acyltransferase β (LPAATβ) promotes the tumor growth of human osteosarcoma

Background

Osteosarcoma is the most common primary malignancy of bone with poorly characterized molecular pathways important in its pathogenesis. Increasing evidence indicates that elevated lipid biosynthesis is a characteristic feature of cancer. We sought to investigate the role of lysophosphatidic acid acyltransferase β (LPAATβ, aka, AGPAT2) in regulating the proliferation and growth of human osteosarcoma cells. LPAATβ can generate phosphatidic acid, which plays a key role in lipid biosynthesis as well as in cell proliferation and survival. Although elevated expression of LPAATβ has been reported in several types of human tumors, the role of LPAATβ in osteosarcoma progression has yet to be elucidated.

Methodology/Principal Findings

Endogenous expression of LPAATβ in osteosarcoma cell lines is analyzed by using semi-quantitative PCR and immunohistochemical staining. Adenovirus-mediated overexpression of LPAATβ and silencing LPAATβ expression is employed to determine the effect of LPAATβ on osteosarcoma cell proliferation and migration in vitro and osteosarcoma tumor growth in vivo. We have found that expression of LPAATβ is readily detected in 8 of the 10 analyzed human osteosarcoma lines. Exogenous expression of LPAATβ promotes osteosarcoma cell proliferation and migration, while silencing LPAATβ expression inhibits these cellular characteristics. We further demonstrate that exogenous expression of LPAATβ effectively promotes tumor growth, while knockdown of LPAATβ expression inhibits tumor growth in an orthotopic xenograft model of human osteosarcoma.

Conclusions/Significance

Our results strongly suggest that LPAATβ expression may be associated with the aggressive phenotypes of human osteosarcoma and that LPAATβ may play an important role in regulating osteosarcoma cell proliferation and tumor growth. Thus, targeting LPAATβ may be exploited as a novel therapeutic strategy for the clinical management of osteosarcoma. This is especially attractive given the availability of selective pharmacological inhibitors.     

砷超富集植物蜈蚣草原生质体的分离及其抗砷性分析

蜈蚣草(Pteris vittata)是一种砷超富集植物, 能够通过根从土壤中吸收砷, 并将其输送至羽叶中富集。为了探索蜈蚣草单个细胞在砷积累和砷抗性中的特性, 本文首次通过酶解方法获得了这一砷超富集蕨类植物的原生质体, 并研究了原生质体在不同浓度砷胁迫下的生活力。结果显示, 蜈蚣草原生质体的抗砷性远高于烟草原生质体的抗砷性, 与其整体植株的抗性一致。这为探索砷抗性和超富集机理提供了一个新的研究体系。     

Efficient purification and preconcentration of erythropoietin in human urine by reusable immunoaffinity column

In this paper, an efficient method is proposed for purification and preconcentration of erythropoietin (EPO) in human urine samples. The EPO-specific immunoaffinity column (IAC) was generated by covalent immobilization of anti-EPO polyclonal antibodies on Sepharose 4B support. The EPO-binding capacity of the IAC was found to be about 2.0 microg (6.6IU) per 1.5 mL of gel and the activity recoveries of EPO at low concentrations of 7.8, 10 and 120 m IU/mL by the IAC were between 78 and 86%. Substantial cleanup effect was observed when the IAC was applied to human urine samples.     

The role of chloroplast NAD(P)H dehydrogenase in protection of tobacco plant against heat stress

After incubation at 42°C for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (ΔndhCKJ), followed by wilt of the leaves, while less the phenotype was found in its wild type (WT). Analysis of the kinetics of post-illumination rise in chlorophyll fluorescence indicated that the PSI cyclic electron flow and the chlororespiration mediated by NAD(P)H dehydrogenase (NDH) was significantly enhanced in WT under the high temperature. After leaf disks were treated with methyl viologen (MV), photosynthetic apparatus of ΔndhCKJ exhibited more severe photo-oxidative damage, even bleaching of chlorophyll. Analysis of P700 oxidation and reduction showed that the NDH mediated cyclic electron flow probably functioned as an electron competitor with Mehler reaction, to reduce the accumulation of reactive oxygen species (ROS). When leaf disks were heat stressed at 42°C for 6 h, the photochemical activity declined more markedly in ΔndhCKJ than in WT, accompanied with more evident decrease in the amount of soluble Rubisco activase. In addition, the slow phase of millisecond-delayed light emission (ms-DLE) of chlorophyll fluorescence indicated that NDH was involved in the building-up of transthylakoid proton gradient (ΔpH), while the consumption of ΔpH was highly inhibited in ΔndhCKJ after heat stress. Based on the results, we supposed that the cyclic electron flow mediated by NDH could be stimulated under the heat stressed conditions, to divert excess electrons via chlororespiration pathway, and sustain CO₂ assimilation by providing extra ΔpH, thus reducing the photooxidative damage.     

Inductin of neuron-derived orphan receptor-1 in the dentate gyrus of the hippocampal formation following transient global ischemia in the rat

Neuron-derived orphan receptor (NOR-1) is a member of the thyroid/steroid receptor superfamily that was originally identified in forebrain neuronal cells undergoing apoptosis. In addition to apoptotic stimuli, activation of several signal transduction pathways including direct neuronal depolarization regulates the expression of NOR-1. In this study we tested whether the expression of NOR-1 is changed following transient ischemic injury in the adult rat brain. NOR-1 mRNA increased rapidly in the dentate gyrus of the hippocampal formation and piriform cortex 3 h after transient global ischemia and returned to basal level at 6 h. On the other hand, oxygen-glucose deprivation of cultured cerebral cortical neurons did not alter the expression of NOR-1. These results suggest that expression of NOR-1 is differentially regulated in different brain regions in response to globally applied brain ischemia, but that hypoxia is not sufficient to induce its expression.     

Recombinant chimeric antibody hCAb as a novel anti-human colorectal carcinoma agent

A new chimeric IgG1 antibody hCAb which could be specifically directed against a cell surface-associated glycoprotein of colorectal cancer cells was prepared by genetic engineering technology in our lab. In this study, we explored the potential therapeutic mechanisms and described the evaluation of hCAb directed against colorectal cancer. The standard 51Cr release assay showed that like many other clinically validated IgG1 monoclonal antibodies, hCAb primarily acts by antibody-dependent cell-mediated cytotoxicity (ADCC). The maximal cell lysis of ADCC induced by hCAb was over 50% in the presence of peripheral blood mononuclear cells (PBMCs). Moreover, in vivo studies showed potent antitumor effects in nude mice with SW480 and Hce-8693 tumor xenografts. The treatment with hCAb induced a dramatic reduction (over 70%) in tumor volume in comparison to untreated control group. Furthermore, during the period of treatment, the animals treated by hCAb did not show signs of wasting or other visible signs of toxicity. No obvious tissue damage in vital organs was detected. The chimeric antibody hCAb may be a promising candidate in the treatment of human colorectal cancer. This study can provide a reference for the potential application of hCAb in clinical trial.