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SUMMARY: Veterinary oncology is very important nowadays to get a better understanding of human carcinogenesis. Estrogen receptor, progesterone receptor and Human Epidermal Growth Factor receptor 2 are frequently evaluated by immunohistochemistry (HIC) in human breast tumor. WT1 is an oncogene, its overexpression has been detected in leukemia and diverse solid tumors like breast cancer, lung cancer and mesothelioma in humans. WT1 expression was evaluated in 15 canine breast tumors (CBT) diagnosed by histopathological analysis to find its relationship with neoplasia and malignancy. IHC and RT-PCR were performed in CBT tissues. Fisher´s test was used to analyze WT1 relationship with malignancy. Of the 15 tumors, 9 (60 %) were diagnosed as benign and 6 (40 %) were malignant. With IHC, WT1 expression was positive only in biopsies diagnosed as malignant. Expression of WT1 by RT-PCR was detected in 14 of the 15 tumors (93.33 %) as well as in control healthy mammary gland. Clinical significance: This study describes for the first time a close correlation between CBT and a positive result for WT1 expression with IHC; hence, it can be used as a biomarker for this neoplasia and as an indicator of malignancy. RT-PCR analysis also showed to be good option to detect WT1 expression. These results will be useful to further investigations to elucidate WT1-related signaling pathways in CBT. Also to know molecules that regulate the translation of this protein as a marker for tumor progression. RESUMEN: La oncología veterinaria es muy importante hoy en día para comprender mejor la carcinogénesis humana. El receptor de estrógeno, el receptor de progesterona y el receptor 2 del factor de crecimiento epidérmico humano se evalúan con frecuencia mediante inmunohistoquímica (HIC) en tumores de mama humanos. WT1 es un oncogén, su sobreexpresión se ha detectado en leucemia y en diversos tumores sólidos como el cáncer de mama, cáncer de pulmón y mesotelioma en humanos. La expresión de WT1 se evaluó en 15 tumores de mama caninos (TCC) diagnosticados mediante análisis histopatológico para encontrar su relación con la neoplasia y la malignidad. IHC y RT-PCR se realizaron en tejidos CBT. La prueba de Fisher se utilizó para analizar la relación de WT1 con la malignidad. De los 15 tumores, 9 (60 %) fueron diagnosticados como benignos y 6 (40 %) fueron malignos. Con IHC, la expresión de WT1 fue positiva solo en biopsias diagnosticadas como malignas. La expresión de WT1 por RT-PCR se detectó en 14 de los 15 tumores (93,33 %), así como en el control de la glándula mamaria sana. Importancia clínica: este estudio describe por primera vez una estrecha correlación entre la TCC y un resultado positivo para la expresión de WT1 con IHC; por lo tanto, se puede utilizar como un biomarcador para esta neoplasia y como un indicador de malignidad. El análisis por RT-PCR también demostró ser una buena opción para detectar la expresión de WT1. Estos resultados serán útiles para futuras investigaciones para dilucidar las vías de señalización relacionadas con WT1 en la TCC. También para conocer moléculas que regulan la traducción de esta proteína como marcador de progresión tumoral.

Although TiO2 particles constitute a highly used material in consumer products, including food and pharmaceutical industries, considerable experimental evidence suggests that TiO2 particle exposure could be harmful and cause adverse health effects. Generally, the most studied factor for toxicity is size as nano, and fine particles are considered more toxic than bulk forms. The second structural factor most studied is the crystalline phase. The TiO2 rutile phase is considered a more inert phase than the highly active, high-refractive-index anatase phase. The cytotoxicity of TiO2-anatase has been related to that these particles can induce higher production of reactive oxygen species (ROS), which is a trigger of apoptosis pathway and alteration of mitochondrial membrane potential in cells. However, such a toxicological susceptibility to the TiO2-anatase phase may differ from the one initiated by the TiO2-rutile phase, suggesting a different cell death mechanism, which is not known at the detail. In this thesis, a series of experimental measurements were carried out to analyze TiO2-anatase and TiO2-rutile submicron-sized particles' physical properties. The TiO2 particles in anatase phase were transformed to rutile phase through a heating process, and then both were analyzed by Raman spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), and zeta potential. The evaluation of the toxicity of TiO2 particles in H9c2 cardiac cells to identify the role of the crystalline phase that may pose a health risk in a dose-dependent manner is the main objective of this study. The TiO2-anatase and TiO2-rutile particles' toxicity assessment was conducted in vitro, evaluating the metabolic activity, the plasma membrane integrity, mitochondrial superoxide production, and intracellular redox state. The particles' characterization by XRD and Raman spectroscopy confirmed the successful transformation of anatase particles to the rutile phase through a heating process. By DLS, it was confirmed that the hydrodynamic particle diameter was 166 nm and 468 nm for anatase and rutile, respectively. At the same time, further analysis by XLPA methods: Williamson-Hall and Warren Averbach showed that the apparent crystallite size of anatase is larger than for rutile. SEM microscopy identified that anatase particles had a spheric-like shape while for rutile were slightly more elongated. H9c2 cells show metabolic activity inhibition of 50% at an approximate value of 30 μg/mL when exposed to either anatase or rutile particles for 24 h. However, the dose-dependent inhibition at lower or higher values of the IC50 is dependent on the crystalline structure. Neither anatase phase nor rutile phase reduces the number of viable cells through necrosis; however, cell death has been categorized as early or late apoptosis for both particles. No significant alteration of the intracellular redox state at any particle exposure concentration between 0.3 μg/mL – 30 μg/mL was observed. On the other hand, for anatase, a 3-fold increase in mitochondrial superoxide production at 30 μg/mL was found, indicating that the intrinsic mitochondrial apoptotic pathway might mediate the apoptosis. However, for rutile, there is no increase in mitochondrial ROS production, suggesting that the cell death mechanism is dependent on a different metabolic pathway independent of the mitochondria. Master of Science in Nanotechnology