Descriptive and functional analysis of (Pro)renin receptor (PRR) in colorectal cancer

Abstract

Despite the last progress made on biomedical field during the last years, colorectal cancer (CRC) is still the third most frequent cancer in men and the second in women worldwide according to the WHO (World Health Organization). Moreover, its high incidence makes it one of the main causes of cancer-related deaths.Renin Angiotensin System (RAS) is a peptide system classically related to the regulation of blood pressure and hydroelectrolitic balance. Recent studies have demonstrated that beyond the classical functions, RAS is also involved in processes related to cancer progression. However, the high complexity of the system impedes the full understanding of it specific role in those processes. In fact, there are components, such as (pro)renin receptor (PRR), of which very little is known. The investigation on the functions of the newly discovered components might contribute to the full understanding of the role of RAS in cancer. Even if there are very few works that study the role of PRR in cancer, some preliminary results suggest an important role of PRR in cancer. However, such lack of studies makes its comprehension still superficial.The aim of this Doctoral Thesis is the study of PRR in colorectal cancer from descriptive and functional points of views. To that end, immunohistochemical techniques as well as cell and molecular biology techniques have been employed.The results of the descriptive study point PRR as a key component in the initiation of CRC, since its protein expression augments gradually along the polyp-cancer sequence. Moreover, it could be considered a potential biomarker of CRC progression in the intestinal-type histologic subtype (the most frequent one). In fact, PRR is able to predict the aggressiveness of CRC according to the stage, as well as patients¿ overall survival. Furthermore, this effect seems to be due to its apparent tight association with the metastatic occurrence. The functional studies, on the other hand, suggest PRR as an essential component for the acquisition of the hallmarks of cancer that colonic cell must gain to develop a cancer. Moreover, we have identified possible microRNAs that might be involved in the regulation of PRR protein expression. Finally, even if we were not able to detect angiotensin peptides in sera of patients with CRC, we have realised that C3f complement fragment and prothrombin could be candidate biomarkers able to discriminate between healthy controls and CRC patients with and without metastasis.To sum up, PRR seems to be deeply involved in CRC initiation and progression and this finding may provide us with possible future CRC biomarkers as well as potential drug targets that may help in the improvement of CRC diagnosis, prognosis and treatment.LABURPENAAzken urteotan eremu biomedikoan aurrerapenak eman badira ere, heste lodiko minbizia (CRC) egun mundu mailan hirugarren ohikoena da gizonezkoetan eta bigarrena emakumezkoetan WHO (World Health Organization)-aren arabera. Gainera, intzidentzia hain altua izanda, mundu mailan minbizi guztien artean CRC hirugarren heriotza-kausa da sexu biak batera hartuta (WHO).Errenina Angiotentsina Sistema (RAS) tentsio arteriala eta balantze hidroelektrolitikoaren erregulazioan parte hartzen duen sistema peptidikoa da. Azken aldiko ikerketek, RASak funtzio kasikoetaz gain minbiziaren garapenari loturiko funtzioak ere betetzen dituela frogatu dute. Hala ere, sistemaren konplexutasun handiak RASak minbizian daukan paper espezifikoaren ulermena eragotzi egiten du. Izan ere, azken urteotan sistemaren osagai berriak aurkitu dira, (pro)errenina hartzailea (PRR) kasu, eta hauen papera oraindik sakonki ikertu gabe dirau. Hauen azterketa sakonak, ondorioz, RASaren zereginen ulermenean lagun lezake. Lan gutxi badaude ere, emaitz preliminarrek PRRak zeregin inportantea izan dezakela iradoki dute, baina oraindik ikerketa lan sakonagoak beharrezkoak dira.Doktore Tesi honen helburua, PRRak heste lodiko minbizian daukan papera ikertzea da ikuspuntu deskriptibo zein funtzionaletik. Horretarako, teknika immunohistokimikoak eta biologia zelular eta molekularreko teknikak erabili ziren.Emaitza deskriptiboek PRR CRCaren abiarazle moduan joka lezakela iradoki dute, bere proteina adierazpena gradualki areagotzen baita polipo-minbizi sekuentzian zehar. Gainera, PRR biomarkatzaile potentziala kotsidera liteke heste-motako adenokartzinometan (azpimota histologiko arruntena). Izan ere, PRR CRCaren estadioaren araberako agresibitatea aurresateko gai da eta baita gaixoen biziraupearen indikatzailea da. Honen eragilea PRRak metastasiaren agerpenarekin daukan ustezko erlazioa izan liteke. Azterketa funtzionalek, bere aldetik, PRR minbiziaren markak eskuratzeko ezinbestekoa dela iradoki dute. Beste alde batetik, PRRaren adierazpena erregula lezaketen zenbait mikroRNA identifikatuz genituen. Azkenik, nahiz eta angiotensina peptidoak ez ziren serum peptidomaren profilean detektatu, C3f konplementuaren fragmentua eta protronbina CRC biomarkatzaile baliogarriak kontsidera litezteke, kontrol osasuntsu eta CRC gaixo metastsidun eta metastasigabeen artean bereizteko.Laburbilduz, PRR CRCaren abiarazle eta bultzatzaile kontsidera liteke. Ebidentzia hauek CRCrako biomarkatzaile edota itu terapeutiko berrien aurkikuntza ekar lezake CRCaren diagnostikoa, pronostikoa eta tratamendua hobetzeko.