Tumour growth and resistance to gemcitabine of pancreatic cancer cells are decreased by AP-2α overexpression

International audienceBACKGROUND: Activator protein-2alpha (AP-2alpha) is a transcription factor that belongs to the family of AP-2 proteins that have essential roles in tumorigenesis. Indeed, AP-2alpha is considered as a tumour-suppressor gene in different tissues such as colonic, prostatic or breast epithelial cells. Moreover, AP-2alpha also participates in the control of colon and breast cancer cells sensitivity towards chemotherapeutic drugs. Despite its potential interest, very few data are available regarding the roles of AP-2alpha in pancreatic cancer. METHODS: We have developed a stable pancreatic CAPAN-1 cell line overexpressing AP-2alpha. Consequences of overexpression were studied in terms of in vivo cell growth, gene expression, migration capacity and chemosensitivity. RESULTS: In vivo tumour growth of CAPAN-1 cells overexpressing AP-2alpha was significantly decreased by comparison to control cells. An altered expression pattern of cell cycle-controlling factors (CDK-4, CDK-6, cyclin-G1, p27(kip1) and p57(kip2)) was observed in AP-2alpha-overexpressing clones by microarrays and western blot analysis. Promoter activity and ChIP analysis indicated that AP-2alpha induces p27(kip1) protein levels by direct binding to and transactivation of its promoter. Moreover, AP-2alpha overexpression increased the chemosensitivity of CAPAN-1 cells to low doses of gemcitabine and reduced their in vitro migration capacity. CONCLUSION: Our data suggested that AP-2alpha overexpression could be exploited to decrease in vivo tumour growth of pancreatic cancer cells and to increase their sensitivity to gemcitabine

A miR-200b/200c/429-Binding Site Polymorphism in the 3′ Untranslated Region of the AP-2α Gene Is Associated with Cisplatin Resistance

The transcription factor AP-2α functions as a tumor suppressor by regulating various genes that are involved in cell proliferation and apoptosis. Chemotherapeutic drugs including cisplatin induce post-transcriptionally endogenous AP-2α, which contributes to chemosensitivity by enhancing therapy-induced apoptosis. microRNAs (miRNAs) miR-200b, miR-200c and miR-429 (miR-200b/200c/429) are up-regulated in endometrial and esophageal cancers, and their overexpression correlates with resistance to cisplatin treatment. Using computational programs, we predicted that the 3′ untranslated region (UTR) of AP-2α gene contains a potential miRNA response element (MRE) for the miR-200b/200c/429 family, and the single nucleotide polymorphism (SNP) site rs1045385 (A or C allele) resided within the predicted MRE. Luciferase assays and Western blot analysis demonstrated that the miR-200b/200c/429 family recognized the MRE in the 3′ UTR of AP-2α gene and negatively regulated the expression of endogenous AP-2α proteins. SNP rs1045385 A>C variation enhanced AP-2α expression by disrupting the binding of the miR-200b/200c/429 family to the 3′ UTR of AP-2α. The effects of the two polymorphic variants on cisplatin sensitivity were determined by clonogenic assay. The overexpression of AP-2α with mutant 3′ UTR (C allele) in the endometrial cancer cell line HEC-1A, which has high levels of endogenous miR-200b/200c/429 and low levels of AP-2α protein, significantly increased cisplatin sensitivity, but overexpression of A allele of AP-2α has no significant effects, compared with mock transfection. We concluded that miR-200b/200c/429 induced cisplatin resistance by repressing AP-2α expression in endometrial cancer cells. The SNP (rs1045385) A>C variation decreased the binding of miR-200b/200c/429 to the 3′ UTR of AP-2α, which upregulated AP-2α protein expression and increased cisplatin sensitivity. Our results suggest that SNP (rs1045385) may be a potential prognostic marker for cisplatin treatment

Low dose cranial irradiation-induced cerebrovascular damage is reversible in mice

BACKGROUND: High-dose radiation-induced blood-brain barrier breakdown contributes to acute radiation toxicity syndrome and delayed brain injury, but there are few data on the effects of low dose cranial irradiation. Our goal was to measure blood-brain barrier changes after low (0.1 Gy), moderate (2 Gy) and high (10 Gy) dose irradiation under in vivo and in vitro conditions. METHODOLOGY: Cranial irradiation was performed on 10-day-old and 10-week-old mice. Blood-brain barrier permeability for Evans blue, body weight and number of peripheral mononuclear and circulating endothelial progenitor cells were evaluated 1, 4 and 26 weeks postirradiation. Barrier properties of primary mouse brain endothelial cells co-cultured with glial cells were determined by measurement of resistance and permeability for marker molecules and staining for interendothelial junctions. Endothelial senescence was determined by senescence associated β-galactosidase staining. PRINCIPLE FINDINGS: Extravasation of Evans blue increased in cerebrum and cerebellum in adult mice 1 week and in infant mice 4 weeks postirradiation at all treatment doses. Head irradiation with 10 Gy decreased body weight. The number of circulating endothelial progenitor cells in blood was decreased 1 day after irradiation with 0.1 and 2 Gy. Increase in the permeability of cultured brain endothelial monolayers for fluorescein and albumin was time- and radiation dose dependent and accompanied by changes in junctional immunostaining for claudin-5, ZO-1 and β-catenin. The number of cultured brain endothelial and glial cells decreased from third day of postirradiation and senescence in endothelial cells increased at 2 and 10 Gy. CONCLUSION: Not only high but low and moderate doses of cranial irradiation increase permeability of cerebral vessels in mice, but this effect is reversible by 6 months. In-vitro experiments suggest that irradiation changes junctional morphology, decreases cell number and causes senescence in brain endothelial cells

Fossil mega- and micro-flora from Bernasso (Early Pleistocene, southern France): A multimethod comparative approach for paleoclimatic reconstruction

International audienceBernasso is an Early Pleistocene locality that has a well-dated floral fossil content including both pollen grains and megaremains. Pollen record shows vegetation changes corresponding to two glacial and one interglacial periods. The megafloral fossil assemblage was interpreted as an association of present-day Mediterranean and Caucasian taxa that developed during a late interglacial stage of the beginning of the Pleistocene. In the present study, climatic reconstruction using the Climate Leaf Analysis Multivariate Program (CLAMP) and the Leaf Margin Analysis (LMA) methods based on the megaflora on one hand and using the Climatic Amplitude Method (CAM) based on the pollen flora on the other hand have been used to check the qualitative climatic estimates based on the comparison between paleovegetation data and similar modern ecosystems. CLAMP and LMA analyses show that the Bernasso climate was colder than the present-day climate of Southern France and of the Hyrcanian and Euxinian regions. On contrary, CAM shows mean annual temperatures higher than the modern Bernasso temperature and equivalent to the temperature of the Hyrcanian and Euxinian regions. Mean annual precipitation and relative humidity reconstructed by CLAMP and CAM are in agreement and indicate that the climate was wetter than today at Bernasso. The differences between the three methods highlight important methodological biases that could be solved by including additional calibration sites in Europe and in the Mediterranean region

Climate changes in the central Mediterranean and Italian vegetation dynamics since the Pliocene

Pollen records and pollen-based climate reconstructions fromthe Italian peninsula (centralMediterranean) show clear signals of vegetation change linked to variations inwater availability in theMediterranean basin over the past 5 million years. Profound vegetation changes occurred in four major steps from the Pliocene to the present. The subtropical taxa that dominate Pliocene assemblages declined and then disappeared between 3–2.8 and 1.66Ma (at around 2.8Ma in the North and later in the South), progressively being replaced by temperate Quercus forests at mid altitude. In the south Italy, Quercus expanded more at around 1.4–1.3 Ma and Fagus proportions increased after 0.5 Ma. Conifer forest (first mainly composed of Tsuga then by Abies and Picea) began to expand at 2.8 Ma, probably rather at high altitude, beginning at 2.8 Ma. Mediterranean-type forest, rare during the Early Pleistocene, developed and increased in diversity during the Middle Pleistocene. Open landscapes, with higher abundances of steppic taxa, becamemore frequent and extensive at the onset of Glacial/Interglacial (G/I) cyclicity around 2.6 Ma and gradually expanded with more and more marked glacials. Climate reconstructions done on selected pollen records from southern Italy suggest a decline in winter temperature and annual precipitation fromthe early Pleistocene to the Holocene. Specifically, both precipitation andwinter temperature reconstructions show changes in interglacial maxima and glacial minima at around 3–2.8 Ma, 2 Ma, 1.3–1.4 Ma and 0.5 Ma. This critical review provides evidence that the North–South precipitation gradient, with drier conditions in the South, has been a consistent feature of the Italian peninsula since the beginning of the Pleistocene

Ecology and biogeography of plant communities associated with the post Plio-Pleistocene relict Rhododendron ponticum subsp. baeticum in southern Spain

17 pages, 5 figures, 5 tables, 79 references.Aims Rhododendron ponticum L. is reputed to be a post Plio-Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500-m main transect in each site, along the stream or river course, in which we placed five 20-m-long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. ponticum individuals. Results Rhododendron ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.Financial support provided by DGICYT-DGESIC grants PB91-0894 and PB95-1144, FED- ER-CICYT grant 1FD97-0743-CO3-03, and GIASA I & II research contracts as a part of environmental compensating tasks for construction of the A-381 highway.Peer reviewe

Evidence for a differentiated chromosomal race north of classical south European refuge areas in the garden dormouse Eliomys quercinus

The dormouse Eliomys quercinus is a forest rodent undergoing long periods of winter hibernation. The species presents a surprisingly large diversity of chromosomal races, which geographic distribution was shown recently to predate the Pleistocene glaciations. Previously reported data on the karyotypes of the garden dormouse in France come from the northeast of the country, where the 2N050 race occurs. New data are presented from specimens trapped near the Atlantic coast (departments of Vendée and Charente-Maritime), in the Pyrenees, the Alps and in the Massif Central. The French Alpine chain, close to the Italian border, is inhabited by the 2N054 race. A karyotype with 2N048 chromosomes, of Iberian type, is found north of the Pyrenees, near the central Atlantic coast and also in the south of the Massif Central, whereas the 2N050 race occurs in the north of the massif. A hybrid between these two races (2N049) was found in Vendée. These facts reveal that neither the Pyrenees nor the Alps constitute a biogeographic barrier to the dormouse and strongly suggest that the present population of northern France derives from a postglacial recolonisation movement initiated in the southernmost regions of France or in the Rhône valley.project no. POCTI/BSE/36626/9