Facultad de Ciencias - Tesis Doctorales y Tesinas - 2010-2019
Permanent URI for this collectionhttps://hdl.handle.net/10171/42535
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117 results
Results
- Response of Tempranillo (Vitis vinifera L.) clones to climate change-related factors (elevated temperature, high CO2 and water deficit): plant performance and berry composition(Universidad de Navarra, 2022-06-30) Arrizabalaga-Arriazu, M. (Marta); Pascual-Elizalde, I. (Inmaculada); Hilbert, G. (Ghislaine); Irigoyen, J.J. (Juan Jose)SUMMARY Climate change is expected to modify future environmental conditions, therefore affecting agriculture. Tempranillo, a largely cultivated worldwide grapevine (Vitis vinifera L.) red variety, will be affected by the increase of global mean temperature and atmospheric CO2 levels and the decrease of water availability in its cultivation area. The use of the intra-varietal diversity has been proposed as a strategy for keeping wine typicity and regional varieties cultivation under future growing conditions by shifting the ripening phase to more favourable environmental conditions. The aim of the thesis was to determine the response of different clones of Tempranillo to simulated 2100 environmental conditions, focusing on plant growth and development, as well as on berry composition. Fruit-bearing cuttings of Tempranillo clones, which differed in the length of their reproductive cycle, were exposed from fruit set to maturity to different scenarios of climate change in temperature gradient greenhouses (TGG) and growth chamber greenhouses (GCG). The impact of elevated temperature (+4 °C), elevated CO2 (700 ppm) and water deficit, both in combination or independently, were evaluated. The results show an increment of vegetative growth and a reduction of yield due to high temperatures. Elevated CO2 concentration also increased vegetative growth and photosynthetic activity, even though an acclimation process was observed, being stronger when combined with high temperature. Water deficit reduced severely the photosynthetic activity and vegetative growth, overshadowing the temperature and CO2 effects. Elevated temperature, both individually and combined with high CO2 levels, hastened sugar accumulation and advanced maturity, but these effects were mitigated by water deficit. Malic acid degradation was also enhanced by high temperature, especially when combined with elevated CO2 and water deficit. Amino acid concentration and profile were affected by high temperature, elevated atmospheric CO2 and, especially, water deficit. Elevated CO2 reduced the effect of temperature decoupling the anthocyanin and TSS accumulation; however, the combination of elevated temperature, high CO2 and water deficit led to the imbalance between these two grape components. Anthocyanin profile was modified by climate change, high temperature increasing the relative abundance of acylated forms and both elevated CO2 and drought favouring the relative content of malvidin and acylated, methylated and tri-hydroxylated forms. The clones studied showed differences in their phenological development, vegetative and reproductive growth, as well as in their grape composition. In addition, the results reveal the existence of a differential response of Tempranillo clones to the environmental conditions projected for 2100 in relation to plant performance and grape composition. In general, RJ43 was the most affected by the future growing conditions (high temperature, elevated CO2 and water deficit) among the clones studied in terms of phenology and anthocyanin concentration and profile. Conversely, VN31 maintained the highest anthocyanin and anthoycianin:TSS ratio, whereas 1084 had the lowest sugar, malic acid and anthocyanin levels. The differences observed in the response of the clones to climate change not always depended on their reproductive cycle length. Keywords: Climate change; Grapevine; Tempranillo; Clones; Intra-varietal diversity; Vegetative development; Grape composition; Anthocyanin profile.
- Estudio de la implicación de la presentación cruzada de antígenos en la actividad antitumoral de anticuerpos monoclonales(Universidad de Navarra, 2022-01-20) Rodriguez, A. (Alfonso); Melero, I. (Ignacio)This PhD project has served to uncover the essential role cDC1s and cross-presentation play in the success of the immunotherapeutic agents anti-PD-1 and anti-CD137, analogous to those available in the clinic and that have revolutionized treatment of cancer. We have done so in loss-of-function settings using mouse genetically deficient for Batf3 and devoid of cDC1s, which displayed complete unresponsiveness to immunotherapy. Next, we have devised gain-of-function experiments aimed to systemically and locally expand cDC1 populations, while at the same time providing local activation signals to mature them. In the first chapter, we chose to expand cDC1s by systemically administering sFlt3L through hydrodynamic injection of sFlt3L-coding plasmid, and to locally activate them by intratumoral injection of Hiltonol®, Poly-ICLC, a TLR3 agonist available in the clinic. In the second chapter, we cloned XCL1 and sFlt3L into a Semliki Forest Virus vector (SFV-XF) for intratumoral administration. In this setting, both transgenes were intended to cause chemoattraction and differentiation of cDC1s, while viral RNA would provide the activation signals to drive DC maturation and potentiate CD8 T-cell cross-priming. Although we did not manage to detect increased cDC1 infiltration into injected tumors, SFV-XF showed robust antitumor efficacy against different tumor models in mice and promoted accumulation of conventional DCs in tumor-draining and distant lymph nodes.
- Aclimatación fotosintética, producción y calidad de plantas de vid (Vitis vinifera L.) de la variedad Tempranillo Tinto y Blanco, cultivadas en diferentes escenarios de cambio climático(Universidad de Navarra, 2022-01-19) Kizildeniz, T. (Tefide); Morales, F. (Fermin); Irigoyen, J.J. (Juan Jose)Atmospheric CO2 concentration has increased from preindustrial level of 280 μmol CO2 mol-1 air (ppm) to currently more than 400 ppm. Intergovernmental Panel on Climate Change foresees that atmospheric CO2 concentration will continue increasing to reach at the end of this century 700 ppm. Due to its greenhouse effect, elevated atmospheric CO2 concentration is leading to higher atmospheric temperatures, a phenomenon that is being accompanied by episodes of less water availability or drought periods. Grapevine (Vitis vinifera L.) is a plant species very sensitive to those environmental factors. Fruit-bearing cuttings of red and white Tempranillo were grown under elevated CO2 (around 700 ppm, versus 400), high temperature (ambient temperature + 4ºC, versus ambient) and water deficit (cyclic drought, versus well irrigated) in temperature gradient greenhouses located at the University of Navarra (Pamplona, Spain) for three consecutive growing seasons (years 2013, 2014 and 2015). Vegetative growth (total vegetative mass and leaf area) was significantly reduced by drought (consistent the three years) and was more associated to a worse substrate water status than to decreases in leaf water content. In spite of decreasing leaf water content in both cultivars, elevated CO2 stimulated more vegetative than reproductive growth. The largest increases of elevated CO2 were observed in leaf and root growth in white and red Tempranillo, respectively. There was a clear interaction between temperature and water availability. Yield was significantly reduced by drought and was year-dependent, being especially low in 2015 due to eventual heat shocks episodes. The high temperatures of the heat shocks (above 35ºC) induced berry burn and browning and finally loss of 50% of the berries. The response of berry quality to climate change-related factors was highly variable and depended on the year. However, some general conclusions can be reached from the three years of experimentation. Thus, the simulated climate change scenarios affected to a greater extent the technological maturity parameters (primary metabolism) than the phenolic maturity (secondary metabolism). In particular, high temperature and drought significantly and consistently increased must pH, due to the decrease in malic acid. On the contrary, elevated CO2 decreased pH associated with significant increases in tartaric acid. These changes of the must affect its quality and potentially that of the resulting wine. Under elevated CO2 concentration, grapevine photosynthesis increases, modulated by temperature and water availability. However, under prolonged exposure to elevated CO2, grapevine down-regulates photosynthesis, decreasing photosynthetic capacity. Grapevine plants underwent photosynthetic acclimation after a long exposure to elevated CO2, regardless of temperature and water availability. Evidence comes from photosynthetic capacity decreases, leaf starch accumulation, and increases in leaf carbon/nitrogen ratio. Photosynthetic acclimation was well correlated to leaf starch, but not to soluble sugars. The white Tempranillo has altered its response to prolonged exposure to elevated CO2. For any given sink size or any given leaf starch accumulation, white Tempranillo always had higher levels of photosynthetic acclimation than the red one. Data suggest that mutation in white Tempranillo has affected loci other than grape color.
- Identification of novel regulators of transcription in iPSC-derived cardiovascular progenitors(2020-03-16) Linares-Acosta, J. (Javier); Carvajal-Vergara, X. (Xonia); Prosper-Cardoso, F. (Felipe); Prosper, F. (Felipe)Stem cells allow to investigate about the basic mechanisms that regulate embryonic development, cellular plasticity, and organ maintenance and regeneration. Induced pluripotent stem cells (iPSCs) are a powerful source of cells for diverse applications such as developmental and disease modeling, drug discovery and regenerative medicine. Cardiac development is coordinated by complex interactions between cardiac progenitor cell populations, different molecular signaling pathways, and spatially and temporally regulated gene expression. Cardiovascular progenitors (CVPs), with similar potential to these present in early stages of embryonic development, can be obtained from iPSCs by mimicking signaling during cardiogenesis, creating an ideal cell source to treat the damaged heart. However, the mechanisms and conditions for long-term self-renewal and maintenance of CVPs remain elusive. The generation of new iPSC models for tracing CVP lineages permits to delve into the biology of CVPs and discover novel potential regulators of their fate. We have established three different Cre/LoxP mouse models for lineage tracing of CVPs and their cell progeny by the expression of ZsGreen (ZsG) protein: Ai6-Mesp1-Cre (Mesp1 tracer), Ai6-Isl1-Cre (Isl1 tracer) and Ai6-Mef2c-AHF-Cre (AHF tracer) mice. Multiple iPSC clones have been derived from Ai6-Isl1-Cre and Ai6-Mef2c-AHF-Cre reporter mice. Several generated iPSC lines have been fully characterized, demonstrating embryonic stem-like features. iPSCs encoded the expected genomic insertions, showed normal karyotypes, transgenes were silenced, and expressed endogenous pluripotency-associated markers. Moreover, iPSCs were capable to differentiate into the three germ layers both in vitro and in vivo. We have verified the utility of established AHFiPSCs to track CVPs and their differentiated progeny. Upon differentiation, ZsG+ cells derived from AHFiPSCs appeared from embryoid body (EB) day 6 onwards, expressed cardiovascular-related markers, and were able to differentiate into cardiomyocytes, endothelial and smooth muscle cells. Comparative gene expression analysis using four different AHFiPSC lines revealed distinct molecular signatures in three particular stages of differentiation: undifferentiated iPSCs (AHFiPS-D0), sorted ZsG+ cells at day 6 (AHFiPS-D6.ZsG+) and sorted ZsG+ cells at day 13 of differentiation (AHFiPS-D13.ZsG+), that expressed pluripotency-, CVP- and cardiac/vascular lineages-associated markers, respectively. Gapdh and Polr2a have been determined the most stable housekeeping genes along the differentiation of AHFiPSCs, being optimal for accurate normalization of gene expression in our samples. We have identified novel regulators of transcription specifically upregulated in CVPs: Lin28a (and its paralog Lin28b), Lhx1 and Nr6a1. The expression of these genes was also found increased in the corresponding CVP-enriched samples from two different public analyses using mouse and human pluripotent stem cells. Moreover, using bioinformatic analysis of biological pathways we have found p53 as an interconnecting molecule of all these selected regulators of transcription. In order to explore novel insights into the biological role of the selected regulators in CVP fate, we have generated an inducible vector (pTRE-CDS-IRES-Puro-REX1-Blast) to carry out gain-of-function (GOF) analyses. This Tet-On system worked properly in AHFiPSC clones, but unfortunately it failed to work in EBs of certain size along differentiation. In contrast, this GOF system correctly functioned in human iPSCs differentiated in monolayer cultures. We have established four CBiPS1sv-4F-5 cell lines carrying Tet-On systems for the inducible expression of LIN28A, LIN28B, NR6A1 and LHX1, and preliminary results indicated that these regulators of transcription might have a role in CVP fate determination.
- Analysis of AAV9 biodistribution, transduction efficiency and AAV-miR-935 cardio-specific overexpression in a murine model of myocardial infarction(2020-03-16) García-Olloqui, P. (Paula); Pelacho, B. (Beatriz)Myocardial infarction (MI) leads to an irreversible loss of cardiac myocytes, which compromises cardiac function. The cellular and molecular mechanisms involved in the ischemic event remain under study, being the cardiac exosomes transfer of non-coding RNAs a key process in this pathology. In this context, a comparative analysis of the exosomal compartment of human cardiac progenitor cells (CPC) was performed in comparison with human bone marrow-mesenchymal stem cells (MSC) and human dermal fibroblasts (HDF). A total of 481 differentially expressed microRNAs (miR) were found, being miR-935 the most differentially expressed in CPC. Analysis of miR-935 in vitro overexpression promoted a positive trend to increment cardiomyocyte survival, in response to oxidative stress. Furthermore, when miR-935 regulation was analyzed in a mouse model of MI disease, miR downregulation was shown five days post-infarct in different cardiac subpopulations. In order to study the role of miR-935 in MI and to achieve an optimal miR-935 overexpression in our mouse model, we developed a robust viral-based method for cardiac-specific miR overexpression. Cardiotropic Serotype 9-Adeno-Associated Virus (AAV9) were used for this purpose and their biodistribution was first determined in mice. Ubiquitous EF1α or the cardiac-specific TnT promoters were combined with Luciferase (Luc) or GFP reporters and administered by intramyocardial or intravenous injection, either in healthy or myocardial-infarcted mice. High transgene expression levels were found in the heart, but not in the liver, of mice receiving AAV-TnT, which was significantly higher after intramyocardial injection regardless of ischemia-induction. On the contrary, high hepatic transgene expression levels were detected with the EF1α-promoter, independently of the administration route and heart damage. Luc expression increased with both promoters in a time-dependent manner, reaching a peak by day 3-7 that was stable for at least 60 days. Moreover, tissue-specific GFP expression was found in cardiomyocytes with the TnT-vector, while minimal cardiac expression was detected with the ubiquitous one. Interestingly, we found that MI greatly increased the transcriptional activity of AAV genomes. Thus, we found AAV9-TnT as a robust and stable vector for cardiac-specific delivery after intramyocardial injection. Finally, the therapeutic potential of this vector in combination with miR-935 was evaluated in a mouse model of myocardial ischemia. Intramyocardial injection of AAV9-TnT-miR935 vector did not significantly improve heart function 60 days post-infarct. However, a slight positive trend in the ejection fraction and a decreased adverse cardiac remodeling are observed, suggesting miR-935 putative cardioprotective role.
- Caracterización de enterobacterias productoras de β-lactamasas de espectro extendido aisladas en muestras alimentarias, ambientales y clínicas(2019-11-25) Ojer-Usoz, E. (Elena); González-Fernández, D. (David); Vitas, A.I. (Ana Isabel)Extended-spectrum β-lactamases (ESBLs) are currently considered one of the major public health concerns throughout over the world, being Escherichia coli the main ESBL-producing bacteria and the specie that causes the greatest number of infections. The emergence of these resistances in different environments suggests a successful selection and dissemination of this antibiotic resistant mechanism, representing a potential risk of failure in clinical treatments. According to the latest recommendations of the World Health Organization and the One Health initiative, there is a need for a collaborative, multidisciplinary and cross-sectorial approach to address potential or existing risks that originate at the animal-human-ecosystems interface. Therefore, the main aim of this study was to characterise the bla genes of ESBL-producing Enterobacteriaceae (ESBL-E) isolated from food, environmental and clinical samples in Navarra (Spain), in order to assess the spread of these bacteria. Samples from different origins were investigated for the presence of ESBL-E: food (n=794), waste water treatment plants (WWTP) (n=279), rivers (n=222), farms (n=91) and animal feeding (n=60). The clinical E. coli isolates (n=130) were provided by the Clínica Universidad de Navarra. The susceptibility to antimicrobial agents was determined by disc diffusion and microdilution methods. PCR and sequencing were used for the molecular characterization of β-lactamase genes (blaCTX-M, blaSHV, blaTEM and blaOXA). In order to characterize the clonal diversity of E. coli, the isolates were assigned to phylogenetic groups (A, B1, B2, D) and phylogenetic relationships were determine by MLST. The high prevalence of ESBL-E observed in meat products (59.4 %) and especially in poultry meat (85.2 %), suggests a possible transfer of resistances through the food chain. We observed high rates of multiresistant strains (> 80 %), especially associated with quinolones and aminoglucosides, but sensibility to carbapenems still continue high (97%). Molecular characterization determined CTX-M-1 the most extended BLEE, being blaCTX-M-1 predominant in environmental samples, blaCTX-M-14 in food, WWTP and animal feeding, blaSHV-12 in farms and blaCTX-M-15 in clinical samples. Regarding phylogenetic groups, A and B1 were prevalent among food and environmental isolates, but those corresponding to phylogroup B2 (more virulent ones) were detected not only in clinical, but also in food, farm and WWTP isolates. A high variability of STs (n=177) and clonal complexes (n=26) were identified, and most of ST addressed to aquatic environments have been detected in other niches. These results showed the wide dissemination of these ESBL producing E. coli among the different sources and the need to control the continuous spread of this resistance.
- Estudio de la degradación fotocatalítica de contaminantes emergentes: desarrollo de composites fotoactivos y aplicación en un reactor de spouted bed(2019-11-21) Rioja-Leal, N. (Nerea); Peñas-Esteban, F.J. (Francisco Javier)Photocatalysis is currently being considered for water decontamination due to its ability to degrade organic pollutants to CO2, water and mineral acids. In TiO2 photocatalysis, UV radiation is needed to create hole-electron pairs which can be transferred to water to form oxidizing species. However, this process generally suffers low apparent quantum yield. Hence, the first goal of this work was to investigate the parameters that deactivate the catalyst in real waters such as tap, river or wastewater. In general, the removal efficiency of clofibric acid (CFA) decreased with inorganic salts, especially with sulfates and carbonates, and also in environmental waters. A general kinetic model was developed to describe the CFA photodegradation depending on the type and concentration of substances present in water. High correlation was observed between experimental CFA concentrations and those predicted by the model. After that, several strategies were tried to improve quantum yields by adding electron scavengers and powdered activated carbon (PAC). Among the e--scavengers tested, only NaIO4 showed significant effect on the degradation of the analytes (a mixture of 5 pharmaceuticals: sulfamethoxazole, carbamazepine, CFA, diclofenac and ibuprofen), especially when the assays were performed in river water. Regarding the addition of PAC, different composites prepared from titania nanoparticles and PAC were tested. In any case, depending on each pharmaceutical tested and on its competitive affinity with the others, the combined treatment of adsorption and photocatalytic degradation improved the overall removal efficiency of drugs in water. One of the main drawbacks of TiO2 photocatalysis its nanometric size that usually leads to catalyst washing out from systems. Hence, a new procedure to immobilize TiO2 nanoparticles on a larger matrix such as calcium alginate was investigated to obtain millimetric-size particles with photocatalytic activity. Two natural thickeners, xanthan gum (XG) and locust bean gum (LBG), were also added to improve the mechanical stability of the photoactive beads. Nevertheless, the presence of thickening compounds affected negatively to their photocatalytic efficiency, while the most effective ones were alginate-TiO2 (TA) beads. Furthermore, a new type of photocatalytic material based on TiO2, calcium alginate and 1.5% of PAC was tested. It was confirmed that these so formed composites (TA/PAC) combined adsorption with photolysis and, thus, were more efficient at micropollutants removal. Finally, a new spouted bed photocatalytic reactor (SBPR) was designed at bench scale. After assessing the effect of light adsorption, inlet air flow and photocatalyst load, continuous-flow experiments were performed for the mixture of pharmaceuticals. Different operational conditions were set in order to evaluate the influence of influent flow rate and pollutant concentration. On the whole, it was noticed that the SBPR worked efficiently for high inlet loadings of contaminants and that it was able to treat satisfactorily micropollutant concentrations of up to 10 mg L-1.
- Implication of ghrelin isoforms in the improvement of nonalcoholic fatty liver disease after bariatric surgery(2019-09-20) Ezquerro-Ezquerro, S. (Silvia); Frühbeck, G. (Gema); Rodriguez, A. (Amaia)Bariatric surgery improves NAFLD and NASH, but the underlying mechanisms remain unknown. The present thesis shows the potential role of acylated and desacyl ghrelin in the progression of NAFLD to NASH through the amelioration of hepatic steatosis and inflammation after bariatric surgery in an experimental model of obesity as well as in patients with morbid obesity. Diet-induced obese rats developed hepatosteatosis and showed decreased circulating desacyl ghrelin without changes in acylated ghrelin concentrations. Sleeve gastrectomy and RYGB induced a dramatic reduction in desacyl ghrelin levels, whereas the acylated/desacyl ghrelin ratio was augmented in obese rats. In patients with morbid obesity and NAFLD, desacyl ghrelin levels were diminished, while circulating TNF-α and the acylated/desacyl ghrelin ratio were increased. Interestingly, six months after bariatric surgery, decreased acylated/desacyl ghrelin levels were found in morbidly obese patients. We demonstrated that bariatric surgery improved hepatic steatosis by reducing hepatic TG content and the lipogenic enzymes Mogat2 and Dgat1, and triggering AMPK-activated mitochondrial FFA β-oxidation and autophagy to a higher extent than caloric restriction in diet-induced obese rats. In addition, both sleeve gastrectomy and RYGB ameliorated hepatic inflammation, as evidenced by a decrease in portal and lobulillar CD68+ and apoptotic cells, proinflammatory JNK activation and a downregulation in the expression of inflammation-related genes (Crp, Tnf and Il6). In parallel, mitochondrial dysfunction was significantly attenuated after sleeve gastrectomy and RYGB via an increase in mitochondrial DNA amount as well as OXPHOS complexes I and II together with an amelioration of ER stress. Specifically, GRP78, spliced XBP-1, ATF4 and CHOP levels were reduced, as was phosphorylated eIF2α, following both bariatric surgical procedures. Our results show that the stimulation of primary rat hepatocytes with acylated and desacyl ghrelin significantly increased TG content, but also prompted AMPK-activated mitochondrial FFA β-oxidation and autophagy. Furthermore, acylated and desacyl ghrelin also inhibited palmitate-triggered inflammation and UPR induction through the downregulation of IRE1α, PERK and ATF6 expression as well as their downstream effectors, ATF4 and CHOP, and chaperone GRP78. In human HepG2 hepatocytes, acylated and desacyl ghrelin treatment reduced TNF-α-induced apoptosis, evidenced by lower caspase-8 and caspase-3 cleavage, as well as TUNEL-positive cells and pyroptosis, revealed by decreased caspase-1 activation and lower HMGB1 expression. Moreover, acylated ghelin suppressed TNF-α-activated hepatocyte autophagy, supported by decreased LC3B-II/I ratio and increased p62 accumulation via AMPK/mTOR, with acylated ghrelin being a protective factor against hepatocyte cell death. Thus, the decrease in the most abundant isoform, desacyl ghrelin, after bariatric surgery contributes to the reduction of lipogenesis, whereas the increased relative acylated ghrelin levels activate factors involved in mitochondrial FFA β-oxidation and autophagy as well as contribute to mitigate obesity-associated hepatic inflammation, mitochondrial dysfunction, ER stress and cell death, thereby ameliorating NAFLD
- Identificación del factor de splicing SLU7 como controlador de la estabilidad genómica(2019-11-07) Jiménez-Andrés, M. (Maddalen); Lázaro-Cantero, R. (Raquel); Raquel; Berasain, C. (Carmen)Hemos estudiado el desconocido papel del factor de splicing SLU7 como mediador de la integridad genómica y regulador de la progresión en la mitosis durante el ciclo celular. Hemos demostrado que la disminución de la expresión de SLU7 en líneas celulares cancerosas de diferentes orígenes contribuye (1) a la formación de híbridos RNA:DNA (R-loops) asociados con la inducción de daño en el DNA y (2) a la parada en la mitosis asociada con la pérdida de cohesión entre las cromátidas hermanas. Ambos eventos están directamente relacionados con la inducción de inestabilidad genómica, característica fundamental de la carcinogénesis. Tanto in vitro como in vivo, hemos caracterizado los mecanismos moleculares que implican alteraciones del splicing y la generación de proteínas aberrantes de SRSF3 y la disminución de SRSF1 y sororina. Nuestros datos presentan a SLU7 como un guardián de la estabilidad genómica y la disminución de su expresión observada en el hígado enfermo de los pacientes podría estar participando en el proceso de hepatocarcinogénesis. Así mismo, en las células transformadas la dependencia de SLU7 para su supervivencia, lo presentan como una nueva diana terapéutica para el cáncer.
- On the hipoxia regulation of CD137 and CD69 expression(2019-07-15) Labiano, S. (Sara); Melero, I. (Ignacio)The tumor microenvironment is characterized to be under severe conditions (nutrient shortage, low pH and oxygen deprivation) that affect not only tumor cells but also stroma and immune infiltrate. Tumor cells have developed mechanism in order to adapt their biology to such extreme circumstances. One of these adaptation strategies is the HIF-1α pathway that is activated under hypoxia (low oxygen availability) promoting angiogenesis, metabolic changes and survival. The projects that have been carried out during this thesis are focused on the influence of hypoxia in the biology of malignant and immune cells in the tumor microenvironment regarding the regulation of two important lymphocyte receptors: CD137 and CD69. Under hypoxic conditions tumor cells promote the alternative splicing of the co-stimulatory receptor CD137 (also known as 4-1BB) resulting in the generation of a functional soluble form of CD137 (sCD137). The secreted sCD137 binds the natural ligand of CD137 (present on APCs) preventing the CD137 ligand-mediated co-stimulation of T-lymphocytes acting as an immune-evasion mechanism. Additionally, CD137 silencing in a colon carcinoma cell line enhances the tumor growth control mediated by CD8+ T lymphocytes. Tumor-infiltrating T lymphocytes (TILs) are also influenced by hypoxia that controls many of the mechanisms that confer T-cells a cytotoxic phenotype. TILs from transplantable and spontaneous mouse tumors express the early T-cell activation marker CD69 more intensely than lymphocytes located in a non-hypoxic tissue such as the spleen. The second study of this thesis points out that hypoxia up-regulates CD69 in T-lymphocytes undergoing TCR-CD3 activation in a HIF-1α dependent manner. Indeed, HIF-1α is able to bind a hypoxia response element (HRE) that we have found in the promoter of the human CD69 gene. In addition, in vivo staining with pimonidazole shows a correlation between hypoxia and the intensity of CD69 expression on T lymphocytes from hypoxic tissues, such as bone marrow and tumor. These studies highlight that hypoxia plays an important role in the interplay between tumors and immune infiltrates in the tumor microenvironment.