Impact of mutant beta-catenin on ABCB1 expression and therapy response in colon cancer cells

Background: Colorectal cancers are often chemoresistant toward antitumour drugs that are substrates for ABCB1-mediated multidrug resistance (MDR). Activation of the Wnt/beta-catenin pathway is frequently observed in colorectal cancers. This study investigates the impact of activated, gain-of-function beta-catenin on the chemoresistant phenotype. Methods: The effect of mutant (mut) beta-catenin on ABCB1 expression and promoter activity was examined using HCT116 human colon cancer cells and isogenic sublines harbouring gain-of-function or wild-type beta-catenin, and patients' tumours. Chemosensitivity towards 24 anticancer drugs was determined by high throughput screening. Results: Cell lines with mut beta-catenin showed high ABCB1 promoter activity and expression. Transfection and siRNA studies demonstrated a dominant role for the mutant allele in activating ABCB1 expression. Patients' primary colon cancer tumours shown to express the same mut beta-catenin allele also expressed high ABCB1 levels. However, cell line chemosensitivities towards 24 MDR-related and non-related antitumour drugs did not differ despite different beta-catenin genotypes. Conclusion: Although ABCB1 is dominantly regulated by mut beta-catenin, this did not lead to drug resistance in the isogenic cell line model studied. In patient samples, the same beta-catenin mutation was detected. The functional significance of the mutation for predicting patients' therapy response or for individualisation of chemotherapy regimens remains to be established

Phosphorus in sediments of high-elevation lakes in the Sierra Nevada (California): implications for internal phosphorus loading

In high-elevation lakes of the Sierra Nevada (California), increases in phosphorus (P) supply have been inferred from changes in phytoplankton growth during summer. To quantify rates of sediment P release to high-elevation Sierran lakes, we performed incubations of sediment cores under ambient and reducing conditions at Emerald Lake and analyzed long-term records of lake chemistry for Emerald and Pear lakes. We also measured concentrations of individual P forms in sediments from 50 Sierra Nevada lakes using a sequential fractionation procedure to examine landscape controls on P forms in sediments. On average, the sediments contained 1,445 µg P g−1, of which 5 % was freely exchangeable, 13 % associated with reducible metal hydroxides, 68 % associated with Al hydroxides, and the remaining 14 % stabilized in recalcitrant pools. Multiple linear regression analysis indicated that sediment P fractions were not well correlated with soluble P concentrations. In general, sediments behaved as net sinks for P even under reducing conditions. Our findings suggest that internal P loading does not explain the increase in P availability observed in high-elevation Sierran lakes. Rather, increased atmospheric P inputs and increased P supply via dissolved organic C leaching from soils may be driving the observed changes in P biogeochemistry

Efficacy of the Vaccine Candidate Based on the P0 Peptide against Dermacentor nitens and Ixodes ricinus Ticks

(This article belongs to the Collection Advances in Tick Research)The control of ticks through vaccination offers a sustainable alternative to the use of chemicals that cause contamination and the selection of resistant tick strains. However, only a limited number of anti-tick vaccines have reached commercial realization. In this sense, an antigen effective against different tick species is a desirable target for developing such vaccines. A peptide derived from the tick P0 protein (pP0) conjugated to a carrier protein has been demonstrated to be effective against the Rhipicephalus microplus, Rhipicephalus sanguineus, and Amblyomma mixtum tick species. The aim of this work was to assess the efficacy of this peptide when conjugated to the Bm86 protein against Dermacentor nitens and Ixodes ricinus ticks. An RNAi experiment using P0 dsRNA from I. ricinus showed a dramatic reduction in the feeding of injected female ticks on guinea pigs. In the follow-up vaccination experiments, rabbits were immunized with the pP0-Bm86 conjugate and challenged simultaneously with larvae, nymphs, and the adults of I. ricinus ticks. In the same way, horses were immunized with the pP0-Bm86 conjugate and challenged with D. nitens larva. The pP0-Bm86 conjugate showed efficacies of 63% and 55% against I. ricinus and D. nitens ticks, respectively. These results, combined with previous reports of efficacy for this conjugate, show the promising potential for its development as a broad-spectrum anti-tick vaccine.This research was funded by the Center for Genetic Engineering and Biotechnology, Havana, Cuba, the Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal, and the Czech Science Foundation grant no. 20-05736S. Mobility was supported by the CYTED Network INCOGARR 110RT0541.info:eu-repo/semantics/publishedVersio

Alternative splicing variant of the hypoxia marker carbonic anhydrase IX expressed independently of hypoxia and tumour phenotype

CA IX is a hypoxia-induced, cancer-associated carbonic anhydrase isoform with functional involvement in pH control and cell adhesion. Here we describe an alternative splicing variant of the CA9 mRNA, which does not contain exons 8–9 and is expressed in tumour cells independently of hypoxia. It is also detectable in normal tissues in the absence of the full-length transcript and can therefore produce false-positive data in prognostic studies based on the detection of the hypoxia- and cancer-related CA9 expression. The splicing variant encodes a truncated CA IX protein lacking the C-terminal part of the catalytic domain. It shows diminished catalytic activity and is intracellular or secreted. When overexpressed, it reduces the capacity of the full-length CA IX protein to acidify extracellular pH of hypoxic cells and to bind carbonic anhydrase inhibitor. HeLa cells transfected with the splicing variant cDNA generate spheroids that do not form compact cores, suggesting that they fail to adapt to hypoxic stress. Our data indicate that the splicing variant can functionally interfere with the full-length CA IX. This might be relevant particularly under conditions of mild hypoxia, when the cells do not suffer from severe acidosis and do not need excessive pH control

Biology of Francisella tularensis Subspecies holarctica Live Vaccine Strain in the Tick Vector Dermacentor variabilis

Background: The c-proteobacterium Francisella tularensis is the etiologic agent of seasonal tick-transmitted tularemia epizootics in rodents and rabbits and of incidental infections in humans. The biology of F. tularensis in its tick vectors has not been fully described, particularly with respect to its quanta and duration of colonization, tissue dissemination, and transovarial transmission. A systematic study of the colonization of Dermacentor variabilis by the F. tularensis subsp. holarctica live vaccine strain (LVS) was undertaken to better understand whether D. variabilis may serve as an inter-epizootic reservoir for F. tularensis. Methodology/Principal Findings: Colony-reared larva, nymph, and adult D. variabilis were artificially fed LVS via glass capillary tubes fitted over the tick mouthparts, and the level of colonization determined by microbial culture. Larvae and nymphs were initially colonized with 8.860.8610 1 and 1.160.03610 3 CFU/tick, respectively. Post-molting, a significant increase in colonization of both molted nymphs and adults occurred, and LVS persisted in 42 % of molted adult ticks at 126 days post-capillary tube feeding. In adult ticks, LVS initially colonized the gut, disseminated to hemolymph and salivary glands by 21 days, and persisted up to 165 days. LVS was detected in the salivary secretions of adult ticks after four days post intra-hemocoelic inoculation, and LVS recovered from salivary gland was infectious to mice with an infectious dose 50 % of 3 CFU. LVS in gravid female ticks colonized via the intra-hemocoelic route disseminated to the ovaries and then t

Hypoxia upregulates expression of human endosialin gene via hypoxia-inducible factor 2

Endosialin is a transmembrane glycoprotein selectively expressed in blood vessels and stromal fibroblasts of various human tumours. It has been functionally implicated in angiogenesis, but the factors that control its expression have remained unclear. As insufficient delivery of oxygen is a driving force of angiogenesis in growing tumours, we investigated whether hypoxia regulates endosialin expression. Here, we demonstrate that endosialin gene transcription is induced by hypoxia predominantly through a mechanism involving hypoxia-inducible factor-2 (HIF-2) cooperating with the Ets-1 transcription factor. We show that HIF-2 activates the endosialin promoter both directly, through binding to a hypoxia-response element adjacent to an Ets-binding site in the distal part of the upstream regulatory region, and indirectly, through Ets-1 and its two cognate elements in the proximal promoter. Our data also suggest that the SP1 transcription factor mediates responsiveness of the endosialin promoter to high cell density. These findings elucidate important aspects of endosialin gene regulation and provide a rational frame for future investigations towards better understanding of its biological significance

A Deep Insight into the Sialotranscriptome of the Gulf Coast Tick, Amblyomma maculatum

Background: Saliva of blood sucking arthropods contains compounds that antagonize their hosts ’ hemostasis, which include platelet aggregation, vasoconstriction and blood clotting; saliva of these organisms also has anti-inflammatory and immunomodullatory properties. Perhaps because hosts mount an active immune response against these compounds, the diversity of these compounds is large even among related blood sucking species. Because of these properties, saliva helps blood feeding as well as help the establishment of pathogens that can be transmitted during blood feeding. Methodology/Principal Findings: We have obtained 1,626,969 reads by pyrosequencing a salivary gland cDNA library from adult females Amblyomma maculatum ticks at different times of feeding. Assembly of this data produced 72,441 sequences larger than 149 nucleotides from which 15,914 coding sequences were extracted. Of these, 5,353 had.75 % coverage to their best match in the non-redundant database from the National Center for Biotechnology information, allowing for the deposition of 4,850 sequences to GenBank. The annotated data sets are available as hyperlinked spreadsheets. Putative secreted proteins were classified in 133 families, most of which have no known function. Conclusions/Significance: This data set of proteins constitutes a mining platform for novel pharmacologically activ

Phosphate sorption characteristics of European alpine soils

9 páginas.We evaluated the chemical properties controlling phosphate (PO4–P) sorption characteristics of alpine soils at elevations of 1725 to 2900 m above sea level in four European mountain ranges (the Tatra Mountains, Slovakia and Poland; the Alps, Austria; the Pyrenees, Spain and France; and the Rila Mountains, Bulgaria). PO4–P sorption isotherms were determined, ranging in concentration from 0 to 6.5 mM KH2PO4 at original soil pH, and were evaluated using the Langmuir equation. PO4–P sorption maxima (Xmax) varied from 6 to 145 mmol kg−1 in the dry (105°C) fine soil fraction (<2 mm). Concentrations of Al oxohydroxides, determined as oxalate extractable aluminum (Alo), ranged between 36 and 770 mmol kg−1, and were the dominant parameter affecting the soil's ability to adsorb PO4–P. In the Tatra Mountains, Rila, and Alps, oxalate-extractable iron (Feo) was also important, while in the Pyrenees we found a significant correlation (p < 0.01) between Xmax and total organic C concentrations. The ability of Al and Fe oxohydroxides to adsorb PO4–P was higher in areas with more acidic soils (the Tatra Mountains) than in areas with higher soil pH (the Pyrenees), and in the more acidic uppermost organic soil horizons than in mineral soil horizons. A simple model based only on two basic soil characteristics (Alo and pH) explained 81 to 89% of the Xmax variability observed in individual mountain areas and 74% of the Xmax variability associated with all samples.Peer reviewe