Gankyrin: An intriguing name for a novel regulator of p53 and RB

SummaryThe RB and p53 tumor suppressors lie at the heart of cancer biology, and inactivation of both pathways is seemingly essential for tumor development. Previous studies identified gankyrin as a component of the 26S proteasome that is consistently overexpressed in liver cancer and promotes cell transformation by binding RB. In the current issue of Cancer Cell, Fujita and colleagues (Higashitsuji et al., 2005) show that gankyrin also binds MDM2 and facilitates its destruction of p53. These important findings implicate gankyrin as a dual-purpose negative regulator of RB and p53, thereby identifying gankyrin as a rational cancer therapeutic target

Element distribution imaging in rat kidney using a 2D rapid scan EDXRF device

Visualization of elemental distributions of biological tissue is gaining importance in many disciplines of biological, forensic, and medical research. On the other hand, the mapping of elements has wider application to the archaeological, to understanding pigments, modes of preservation, and environmental context. Since major advances in relation to collimators and detectors have yielded micro scale images, the chemical mapping via synchrotron scanning micro-X-ray fluorescence spectrometry (SR-µXRF) is widely used as microanalytical techniques. However, the acquisition time is a limitation of current SR-µXRF imaging protocols, doing tedious micro analysis of samples of more than 1 cm and very difficult to study of larger samples such as animal organ, whole organisms, work of art, etc. Recently we have developed a robotic system to image the chemistry of large specimens rapidly at concentration levels of parts per million. Multiple images of distribution of elements can be obtained on surfaces of 100x100 mm and a spatial resolution of up to 0.2 mm2 per pixel, with a spectral capture time up to 1 ms per point. This system has proven to be highly efficient for the XRF mapping of elements in large biological samples, achieving comparables results to those obtained by SR-μXRF. Thus, images of As and Cu accumulation in renal cortex of arsenic-exposed rats were obtained by both methodologies. However, the new imaging system enables the XRF scanning in few minutes, whereas SR-μXRF required several hours. These and other advantages as well as the potential applications of this system, will be discussed.Fil: Figueroa, Rodolfo. Universidad de la Frontera; ChileFil: Lozano, E.. Instituto Nacional del Cancer; ChileFil: Bongiovanni, Guillermina Azucena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnol.conicet - Patagonia Norte. Instituto de Investigación y Des. En Ing. de Procesos, Biotecnología y Energias Alternativas. Idepa - Subsede San Antonio Oeste; Argentin

Mesenchymal Stem Cells and the Origin of Ewing's Sarcoma

The origin of Ewing's sarcoma is a subject of much debate. Once thought to be derived from primitive neuroectodermal cells, many now believe it to arise from a mesenchymal stem cell (MSC). Expression of the EWS-FLI1 fusion gene in MSCs changes cell morphology to resemble Ewing's sarcoma and induces expression of neuroectodermal markers. In murine cells, transformation to sarcomas can occur. In knockdown experiments, Ewing's sarcoma cells develop characteristics of MSCs and the ability to differentiate into mesodermal lineages. However, it cannot be concluded that MSCs are the cell of origin. The concept of an MSC still needs to be rigorously defined, and there may be different subpopulations of mesenchymal pluripotential cells. Furthermore, EWS-FLI1 by itself does not transform human cells, and cooperating mutations appear to be necessary. Therefore, while it is possible that Ewing's sarcoma may originate from a primitive mesenchymal cell, the idea needs to be refined further

Uloga karotenoida iz ekstrakta mesa bundeve u zaštiti od oštećenja krvno-moždane barijere uzrokovane mikotoksinima in vitro

Some mycotoxins such as beauvericin (BEA), ochratoxin A (OTA), and zearalenone (ZEA) can cross the blood brain barrier, which is why we tested the anti-inflammatory action of a pumpkin carotenoid extract (from the pulp) against these mycotoxins and their combinations (OTA+ZEA and OTA+ZEA+BEA) on a blood brain barrier model with co-cultured ECV304 and C6 cells using an untargeted metabolomic approach. The cells were added with mycotoxins at a concentration of 100 nmol/L per mycotoxin and pumpkin carotenoid extract at 500 nmol/L. For control we used only vehicle solvent (cell control) or vehicle solvent with pumpkin extract (extract control). After two hours of exposure, samples were analysed with HPLC-ESI-QTOF-MS. Metabolites were identified against the Metlin database. The proinflammatory arachidonic acid metabolite eoxin (14,15-LTE4) showed lower abundance in ZEA and BEA+OTA+ZEA-treated cultures that also received the pumpkin extract than in cultures that were not treated with the extract. Another marker of inflammation, prostaglandin D2-glycerol ester, was only found in cultures treated with OTA+ZEA and BEA+OTA+ZEA but not in the ones that were also treated with the pumpkin extract. Furthermore, the concentration of the pumpkin extract metabolite dihydromorelloflavone significantly decreased in the presence of mycotoxins. In conclusion, the pumpkin extract showed protective activity against cellular inflammation triggered by mycotoxins thanks to the properties pertinent to flavonoids contained in the pulp.Pojedini mikotoksini poput bovericina (BEA), okratoksina A (OTA) i zearalenona (ZEA) prelaze krvno-moždanu barijeru, a to je i razlog zbog kojega smo istražili djelovanje ekstrakta karotenoida iz mesa bundeve protiv upalnih procesa izazvanih ovim mikotoksinima i njihovim kombinacijama (OTA+ZEA i OTA+ZEA+BEA) na modelu krvno-moždane barijere koji se sastojao od kultura stanica ECV304 i C6, oslanjajući se pritom na neciljani metabolomički pristup. Stanice su tretirane mikotoksinima u koncentraciji od 100 nmol/L po mikotoksinu odnosno ekstraktom karotenoida u koncentraciji od 500 nmol/L. Za kontrolu smo upotrijebili samo otapalo (stanična kontrola) odnosno otapalo s bundevinim ekstraktom (ekstraktna kontrola). Nakon dva sata tretmana uzorci su analizirani metodom tekućinske kromatografije / masene spektrometrije (HPLC-ESI-QTOF-MS), a dobiveni metaboliti identificirani su usporedbom s bazom podataka Metlin. Primjena ekstrakta značajno je smanjila količinu metabolita proupalne arahidonske kiseline eoksina (14,15-LTE4) u kulturama tretiranima samo zearalenonom odnosno kombinacijom BEA+OTA+ZEA. Drugi upalni biljeg, prostaglandin D2-glicerol ester, otkriven je samo u kulturama tretiranima kombinacijama OTA+ZEA odnosno BEA+OTA+ZEA, ali ne i u onima koje su usto tretirane bundevinim ekstraktom. Osim toga, u prisutnosti mikotoksina značajno je porasla koncentracija metabolita dihidromoreloflavona iz bundevina ekstrakta. Time je taj ekstrakt iskazao zaštitno djelovanje protiv stanične upale uzrokovane mikotoksinima zahvaljujući svojstvima flavonoida koji se nalaze u njezinu mesu

Nitric oxide sensing in plants is mediated by proteolytic control of group VII ERF transcription factors

Nitric oxide (NO) is an important signaling compound in prokaryotes and eukaryotes. In plants, NO regulates critical developmental transitions and stress responses. Here, we identify a mechanism for NO sensing that coordinates responses throughout development based on targeted degradation of plant-specific transcriptional regulators, the group VII ethylene response factors (ERFs). We show that the N-end rule pathway of targeted proteolysis targets these proteins for destruction in the presence of NO, and we establish them as critical regulators of diverse NO-regulated processes, including seed germination, stomatal closure, and hypocotyl elongation. Furthermore, we define the molecular mechanism for NO control of germination and crosstalk with abscisic acid (ABA) signaling through ERF-regulated expression of ABSCISIC ACID INSENSITIVE5 (ABI5). Our work demonstrates how NO sensing is integrated across multiple physiological processes by direct modulation of transcription factor stability and identifies group VII ERFs as central hubs for the perception of gaseous signals in plants

MDM2 Associates with Polycomb Repressor Complex 2 and Enhances Stemness-Promoting Chromatin Modifications Independent of p53

SummaryThe MDM2 oncoprotein ubiquitinates and antagonizes p53 but may also carry out p53-independent functions. Here we report that MDM2 is required for the efficient generation of induced pluripotent stem cells (iPSCs) from murine embryonic fibroblasts, in the absence of p53. Similarly, MDM2 depletion in the context of p53 deficiency also promoted the differentiation of human mesenchymal stem cells and diminished clonogenic survival of cancer cells. Most of the MDM2-controlled genes also responded to the inactivation of the Polycomb Repressor Complex 2 (PRC2) and its catalytic component EZH2. MDM2 physically associated with EZH2 on chromatin, enhancing the trimethylation of histone 3 at lysine 27 and the ubiquitination of histone 2A at lysine 119 (H2AK119) at its target genes. Removing MDM2 simultaneously with the H2AK119 E3 ligase Ring1B/RNF2 further induced these genes and synthetically arrested cell proliferation. In conclusion, MDM2 supports the Polycomb-mediated repression of lineage-specific genes, independent of p53

Coexpression of Normally Incompatible Developmental Pathways in Retinoblastoma Genesis

It is widely believed that the molecular and cellular features of a tumor reflect its cell of origin and can thus provide clues about treatment targets. The retinoblastoma cell of origin has been debated for over a century. Here, we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type-specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Furthermore, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro

Expression Signatures of Metastatic Capacity in a Genetic Mouse Model of Lung Adenocarcinoma

Background: Non-small cell lung cancer (NSCLC) is the foremost cause of cancer-related death in Western countries, which is due partly to the propensity of NSCLC cells to metastasize. The biologic basis for NSCLC metastasis is not well understood. Methodology/Principal Findings: Here we addressed this deficiency by transcriptionally profiling tumors from a genetic mouse model of human lung adenocarcinoma that develops metastatic disease owing to the expression of K-rasG12D and p53R172H. We identified 2,209 genes that were differentially expressed in distant metastases relative to matched lung tumors. Mining of publicly available data bases revealed this expression signature in a subset of NSCLC patients who had a poorer prognosis than those without the signature. Conclusions/Significance: These findings provide evidence that K-rasG12D; p53R172H mice recapitulate features of human NSCLC metastasis and will provide a useful platform on which to study the biologic basis for lung adenocarcinom