[en] Chapter One Inflammatory bowel disease (IBD) is characterized by chronic inflammation in the gastrointestinal tract and represents an important risk factor for the onset of colorectal cancer (CRC). Hakai is an E3 ubiquitin-ligase involved in tumour progression and metastasis of carcinomas through the degradation of E-cadherin. The loss of E-cadherin is the hallmark of EMT, a key process at early stages of carcinoma progression. In this work we investigated the expression of Hakai in all the different stages of CRC as well as its potential role in IBD. Our results show that Hakai is a potential biomarker for CRC progression and its expression is increased even at early TNM-stages of tumorigenesis. Interactome analysis of Hakai in CRC cells allowed us to identify a novel Hakai-interacting protein named FASN, a protein reported to be associated to IBD. We described that Hakai increases FASN ubiquitination and degradation, resulting in the regulation of FASN-mediated lipid accumulation. Moreover, we showed that Hakai is downregulated in inflammatory tissues by using different IBD mice models and that IFN-γ downregulates Hakai expression in CRC cells. Our findings open a new research field to better understand the mechanisms involved in intestinal inflammation and cancer bowel disease. Chapter Two CRC is one of leading causes of mortality in western countries and new strategies are required for its treatment. Natural products comprise a vast diversity of biologically active substances with high therapeutic potential including compounds widely used in anticancer chemotherapy. Polysaccharide-rich extracts from fungal origin, for example, have proven their antitumoral effects in different previous studies. In the present study, we aim to evaluate the possible antitumor effect on CRC cells of a series of fungal polysaccharide-rich extracts, obtained from autochthonous fungi of Galicia. We identified two extracts from Trametes versicolor (TV) and Grifola frondosa (GF) which exhibited inhibition of human colon cancer cell proliferation and induced cytotoxicity. Furthermore, both fungal extracts significantly inhibited oncogenic potential, cell migration and invasion in CRC cells as well as increased E-Cadherin expression and reduced metalloproteinase activity. Finally, our results also showed that the combination of the extracts with one the most clinical used agents for colorectal cancer, 5-fluorouracil, increases cell cytotoxicity, opening the door to further research for the use of fungal extracts as adjuvant treatment in cancer.

[gl] Capítulo Un A enfermidade inflamatoria intestinal (EII) caracterízase pola inflamación crónica do tracto gastrointestinal e representa un importante factor de risco para o desenvolvemento do cancro colorrectal (CRC). Hakai é unha E3 ubiquitina-ligasa implicada na progresión tumoral e metástase de carcinomas a través da degradación da E-cadherina. A perda de E-cadherina é o selo distintivo de TMS, un proceso clave nas primeiras fases da progresión dos carcinomas. Neste traballo, investígase a expresión de Hakai en todas as diferentes etapas do CRC, así como o seu potencial papel na EII. Os resultados mostran que Hakai é un biomarcador potencial da progresión do CRC cunha expresión aumentada incluso nas fases iniciais da carcinoxénese. A análise do interactoma de Hakai nas células CRC identificou unha nova proteína que interactúa con Hakai, FASN, unha proteína asociada ao desenvolvemento da EII. Neste traballo, descríbese que Hakai aumenta a ubiquitinación e degradación de FASN, provocando a regulación da acumulación de lípidos mediada por FASN. Ademais, móstrase que Hakai está regulado negativamente nos tecidos inflamatorios de diferentes modelos animais de IBD e que o IFN-γ regula negativamente a expresión de Hakai nas células CCR. Os nosos descubrimentos abren un novo campo de investigación para comprender mellor os mecanismos implicados na inflamación intestinal e no cancro. Capítulo dous O CRC é unha das principais causas de mortalidade nos países occidentais e son necesarias novas estratexias para o seu tratamento. Os produtos naturais comprenden unha gran variedade de substancias biolóxicamente activas con alto potencial terapéutico, incluídos compostos moi utilizados na quimioterapia contra o cancro. Extractos ricos en polisacáridos de orixe fúngica, por exemplo, demostraron os seus efectos antitumorais en diferentes estudos anteriores. No presente traballo pretendemos avaliar o posible efecto antitumoral sobre as células CRC dunha serie de extractos de fungos ricos en polisacáridos, obtidos a partir de fungos autóctonos de Galicia. Identificáronse dous extractos de Trametes versicolor (TV) e Grifola frondosa (GF) con capacidade citotóxica e de inhibición da proliferación de células CRC. Ademais, ambos extractos foron capaces de inhibir significativamente o potencial oncoxénico, a migración celular e a invasión das células CRC, así como aumentar os niveis de expresión da E-Cadherina e reducir a actividade das metaloproteinasas. Por último, os nosos resultados tamén mostran que a combinación dos extractos cun dos axentes máis empregados na clínica para o cancro colorrectal, o 5-fluorouracilo, aumenta a citotoxicidade celular, abrindo a porta a novas investigacións sobre o uso de extractos de fungos como tratamento adxuntivo no cancro.