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991.
c-Myc interacts with components of the pre-replication complex and directly regulates DNA replication [1]. However the consequences of this novel c-Myc function on cell cycle dynamics and replication-associated damage are unknown. Here, we show that c-Myc overexpression in primary human fibroblasts markedly accelerates S-phase while c-Myc deficient fibroblasts exhibit a prolonged S-phase. We also show that the Werner DNA helicase protein (WRN) plays a critical role in supporting c-Myc-driven S-phase, as depletion of WRN in c-Myc overexpressing cells increases DNA damage specifically at sites of DNA synthesis. This excess DNA damage activates a “replication stress” pathway involving ATR, CHK1, CHK2, and p53, leading to rapid senescence of WRN deficient c-Myc overexpressing cells. Indeed, depletion of p53 rescues this senescence response. We propose that WRN functions to repair abnormal replication structures caused by the acceleration of DNA replication by c-Myc. This work provides an additional mechanistic explanation for c-Myc-induced DNA damage and senescence, and reveals a vulnerability of c-Myc overexpressing cells that could potentially be exploited in cancer therapy. 相似文献
992.
Francesca Boscia Carla Lucia Esposito Antonella Di Crisci Vittorio de Franciscis Lucio Annunziato Laura Cerchia 《PloS one》2009,4(8)
The glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for several neuronal populations in different brain regions, including the hippocampus. However, no information is available on the: (1) hippocampal subregions involved in the GDNF-neuroprotective actions upon excitotoxicity, (2) identity of GDNF-responsive hippocampal cells, (3) transduction pathways involved in the GDNF-mediated neuroprotection in the hippocampus. We addressed these questions in organotypic hippocampal slices exposed to GDNF in presence of N-methyl-D-aspartate (NMDA) by immunoblotting, immunohistochemistry, and confocal analysis. In hippocampal slices GDNF acts through the activation of the tyrosine kinase receptor, Ret, without involving the NCAM-mediated pathway. Both Ret and ERK phosphorylation mainly occurred in the CA3 region where the two activated proteins co-localized. GDNF protected in a greater extent CA3 rather than CA1 following NMDA exposure. This neuroprotective effect targeted preferentially neurons, as assessed by NeuN staining. GDNF neuroprotection was associated with a significant increase of Ret phosphorylation in both CA3 and CA1. Interestingly, confocal images revealed that upon NMDA exposure, Ret activation occurred in microglial cells in the CA3 and CA1 following GDNF exposure. Collectively, this study shows that CA3 and CA1 hippocampal regions are highly responsive to GDNF-induced Ret activation and neuroprotection, and suggest that, upon excitotoxicity, such neuroprotection involves a GDNF modulation of microglial cell activity. 相似文献
993.
Aude Legoffic Ezequiel Calvo Carla Cano Emma Folch-Puy Marc Barthet Jean Robert Delpero Montse Ferrés-Masó Jean Charles Dagorn Daniel Closa Juan Iovanna 《PloS one》2009,4(10)
Background
The aim of our work was to identify the genes specifically altered in pancreatic adenocarcinoma and especially those that are altered early in cancer development.Methodology/Principal Findings
Gene copy number was systematically assessed with an ultra-high resolution CGH oligonucleotide microarray in DNA from samples of pancreatic cancer. Several new cancer-associated variations were observed. In this work we focused on one of them, involving the reg4 gene. Gene copy number gain of the reg4 gene was confirmed by qPCR in 14 cancer samples. It was also found with increased copy number in most PanIN3 samples. The relationship betweena gain in reg4 gene copy number and cancer development was investigated on the human pancreatic cancer cell line Mia-PaCa2 xenografted under the skin of nude mice. When cells were transfected with a vector allowing reg4 expression, they generated tumors almost twice larger in size. In addition, these tumors were more resistant to gemcitabine treatment than control tumors. Interestingly, weekly intraperitoneal administration of a monoclonal antibody to reg4 halved the size of tumors generated by Mia-PaCa2 cells, suggesting that the antibody interfered with a paracrine/autocrine mechanism involving reg4 and stimulating cancer progression. The addition of gemcitabine resulted in further reduction, tumors becoming 5 times smaller than control. Exposure to reg4 antibody resulted in a significant decrease in intra-tumor levels of pAkt, Bcl-xL, Bcl-2, survivin and cyclin D1.Conclusions/Significance
It was concluded that adjuvant therapies targeting reg4 could improve the standard treatment of pancreatic cancer with gemcitabine. 相似文献994.
Laura Cerchia Carla Lucia Esposito Andreas H. Jacobs Bertrand Tavitian Vittorio de Franciscis 《PloS one》2009,4(11)
The hope of success of therapeutic interventions largely relies on the possibility to distinguish between even close tumor types with high accuracy. Indeed, in the last ten years a major challenge to predict the responsiveness to a given therapeutic plan has been the identification of tumor specific signatures, with the aim to reduce the frequency of unwanted side effects on oncologic patients not responding to therapy. Here, we developed an in vitro evolution-based approach, named differential whole cell SELEX, to generate a panel of high affinity nucleic acid ligands for cell surface epitopes. The ligands, named aptamers, were obtained through the iterative evolution of a random pool of sequences using as target human U87MG glioma cells. The selection was designed so as to distinguish U87MG from the less malignant cell line T98G. We isolated molecules that generate unique binding patterns sufficient to unequivocally identify any of the tested human glioma cell lines analyzed and to distinguish high from low or non-tumorigenic cell lines. Five of such aptamers act as inhibitors of specific intracellular pathways thus indicating that the putative target might be important surface signaling molecules. Differential whole cell SELEX reveals an exciting strategy widely applicable to cancer cells that permits generation of highly specific ligands for cancer biomarkers. 相似文献
995.
Maria J. Santos Hugo M. Matos Carla Baltazar Clara Grilo Margarida Santos-Reis 《Mammalian Biology》2009,74(6):448-455
Carnivores in Mediterranean ecosystems respond to the inherent heterogeneity of these systems by tracking the spatial and temporal availability of food resources. This feeding strategy, however, has been associated primarily with generalist carnivores and little is known for specialist species such as the European polecat. We collected polecat scat to determine the diet of this species, how it matches the seasonal availability of food resources, and how it is affected by population spatial structure and anthropogenic disturbance. Polecats were present in only 34% of the surveyed area and were clumped into three main population nuclei. Despite the spatial segregation of the populations, they had no significant differences in food items consumed. Polecats mostly fed on mammals (percentage of occurrence (P.O.)=43%) and arthropods (P.O.=49%). Biomass intake was also mostly from mammals (percentage of biomass (P.B.)=96%), followed by birds (P.B.=3%), with arthropods contributing less than 1%. Lagomorphs were the most consumed prey (P.O.=25% and P.B.=87%), which is consistent with the marked spatial overlap between scat with high content in lagomorphs and the areas with high wild rabbit availability. These results indicate that polecats are specialists in the consumption of wild rabbits, spatially track the availability of this prey, and may be affected by the decrease in abundance of the prey populations. Future conservation of polecats in Mediterranean regions of southern Portugal may be achieved through the restoration of hunted and diseased wild rabbit populations. 相似文献
996.
997.
Agostina Nardone Carla Cavaliere Sara Corvigno Gennaro Limite Sabino De Placido Bianca Maria Veneziani 《Cell and tissue banking》2009,10(4):301-308
In breast cancer, various clinical parameters are assessed to define clinical stage and thus obtain a more accurate prognosis.
However, banks of tumor tissues are an important source of material for studies of risk of recurrence and of features governing
clinical outcome in breast cancer. Although the heterogeneous characteristics of individual tumors, subtle phenotypes and
stem cells can only be identified in viable cells, tissue banks often give low priority to the preservation of living cells
because it is labor-intensive and expensive. The present study was designed to evaluate the feasibility of introducing, within
the routine procedures of tissue preservation, a cryopreservation protocol that allows the recovery of living cells after
storage. We analyzed the effect of storage time on cell viability, growth rates, and protein expression of ten human breast
cancer specimens subjected to various cryopreservation techniques. Cryopreservation of cancer tissue specimens for 12 months
allowed protein characterization but not the recovery of living cells. Here we show that enzymatic digestion immediately before
slow freezing, and storage in liquid nitrogen permits the recovery and expansion of living cells that can be tailored to specific
requirements and projects. 相似文献
998.
Fonseca I Silva PV Lange CC Guimarães MF Weller MM Sousa KR Lopes PS Guimarães JD Guimarães SE 《Genetics and molecular biology》2009,32(4):776-781
In order to characterize the expression of genes associated with immune response mechanisms to mastitis, we quantified the relative expression of the IL-2, IL-4, IL-6, IL-8, IL-10, IFN-γ and TNF- α genes in milk cells of healthy cows and cows with clinical mastitis. Total RNA was extracted from milk cells of six Black and White Holstein (BW) cows and six Gyr cows, including three animals with and three without mastitis per breed. Gene expression was analyzed by real-time PCR. IL-10 gene expression was higher in the group of BW and Gyr cows with mastitis compared to animals free of infection from both breeds (p < 0.05). It was also higher in BW Holstein animals with clinical mastitis (p < 0.001), but it was not significant when Gyr cows with and without mastitis were compared (0.05 < p < 0.10). Among healthy cows, BW Holstein animals tended to present a higher expression of all genes studied, with a significant difference for the IL-2 and IFN- γ genes (p < 0.001). For animals with mastitis no significant difference in gene expression was observed between the two breeds. These findings suggest that animals with mastitis develop a preferentially cell-mediated immune response. Further studies including larger samples are necessary to better characterize the gene expression profile in cows with mastitis. 相似文献
999.
1000.
Claudia Canales Michalis Barkoulas Carla Galinha Miltos Tsiantis 《Journal of plant research》2010,123(1):25-33
Cardamine hirsuta, a small crucifer closely related to the model organism Arabidopsis thaliana, offers high genetic tractability and has emerged as a powerful system for studying the genetic basis for diversification
of plant form. Contrary to A. thaliana, which has simple leaves, C. hirsuta produces dissected leaves divided into individual units called leaflets. Leaflet formation requires activity of Class I KNOTTED1-like
homeodomain (KNOX) proteins, which also promote function of the shoot apical meristem (SAM). In C. hirsuta, KNOX genes are expressed in the leaves whereas in A. thaliana their expression is confined to the SAM, and differences in expression arise through cis-regulatory divergence of KNOX regulation.
KNOX activity in C. hirsuta leaves delays the transition from proliferative growth to differentiation thus facilitating the generation of lateral growth
axes that give rise to leaflets. These axes reflect the sequential generation of cell division foci across the leaf proximodistal
axis in response to auxin activity maxima, which are generated by the PINFORMED1 (PIN1) auxin efflux carriers in a process
that resembles organogenesis at the SAM. Delimitation of C. hirsuta leaflets also requires the activity of CUP
SHAPED
COTYLEDON (CUC) genes, which direct formation of organ boundaries at the SAM. These observations show how species-specific deployment of
fundamental shoot development networks may have sculpted simple versus dissected leaf forms. These studies also illustrate
how extending developmental genetic studies to morphologically divergent relatives of model organisms can greatly help elucidate
the mechanisms underlying the evolution of form. 相似文献