Imunohistohemijska analiza ekspresije regulatornih proteina ćelijskog ciklusa i proliferativnog Ki-67 (MIB-1) indeksa u adenomima hipofize

Abstract

Adenomi hipofize su najčešći primarni tumori hipofize. Predstavljaju oko 15% svih intrakranijalnih tumora, i uzgredan nalaz na oko 20% autopsija. Više od 95% adenoma hipofize karakteriše benigno ponašanje. Preostalih 5% pripada atipičnim adenomima, dok je maligna transformacija adenoma hipofize izuzetno retka. Aktuelna klasifikacija adenoma hipofize Svetske zdravstvene organizacije se zasniva na imunohistohemijskoj ekspresiji hormona adenohipofize, transkripcionih faktora, citokeratina 8, Ki-67 i p53. Ćelijski ciklus se tradicionalno deli na 4 faze, koje su deo kontinuuma: G1, S, G2 i M, dok je G0 faza faza mirovanja. U kontrolnim tačkama ćelijskog ciklusa (G1/S i G2/M) dolazi do zastoja ukoliko je detektovana nepravilnost u sintezi DNK. Ključnu ulogu u zaustavljanju ćelijskog ciklusa imaju inhibitori ciklin zavisnih kinaza, od kojih su najznačajniji, p16 i p21, obrađeni u ovom istraživanju. Ovi markeri se zato smatraju i markerima senescencije, stanja ireverzibilnog izlaska ćelije iz ćelijskog ciklusa. Ki-67 je protein koji se detektuje u jedru ćelija u svim fazama ćelijskog ciklusa, izuzev G0 faze. Pored toga što omogućava procenu procenta ćelija koje se nalaze u ćelijskom ciklusu, kod adenoma hipofize ima i dijagnostički i prognostički značaj. Protein p53 predstavlja čuvara genoma, budući da se sintetiše nakon detekcije poremećaja DNK. Ovaj protein dovodi do zastoja ćelijskog ciklusa, čija dužina zavisi od veličine popravke. Imunohistohemijska detekcija p53 pozitivnih jedara u adenomima hipofize ima dijagnostičku vrednost, predstavljajući jedan od kriterijuma za dijagnozu atipičnih adenoma i karcinoma hipofize. Cilj ovog istraživanja je procena aktivacije inhibitora ciklin-zavisnih kinaza p16 i p21 i proliferativnog Ki-67 indeksa u adenomima hipofize, njihovim tipovima i podtipovima, kao i u normalnoj adenohipofizi...

Pituitary adenomas (PA) are the most frequent primary pituitary tumors. They comprise up to 15% of all intracranial tumors, and they are found as an incidental finding in up to 20% of all autopsies. PAs are characterized by benign clinical behavior, with the weak tendency to malignant transformation. The WHO classification of PAs is based on immunohistochemical analysis of positivity of anterior pituitary hormones, transcriptional factors, cytokeratin 8, Ki-67 and p53. The cell cycle is traditionally divided into 4 phases, all of them being a part of the continuum: G1, S, G2 and M. G0 is recognized as the quiescent phase. The cell cycle is halted in checkpoints (G1/S and G2/M) after detection of any DNA irregularity. Cyclindependent kinases belong to the group of the most powerful cell cycle inhibitors, p16 and p21 being used in this work. These markers are also known as markers of an irreversible arrest of cell proliferation, known as senescence. Protein Ki-67 is detected in nuclei of all cells that are out of G0 phase of cell cycle. Furthermore, immunohistochemical Ki-67 detection had diagnostic and prognostic significance in PAs. Protein p53 is known as „guardian of genome“, given that it is synthesised after any DNA damage. This protein causes the halting of the cell cycle, which is qualified by the extension of DNA damage. Immunohistochemical p53 detection in PAs is of diagnostic importance, being one of arteria for the diagnosis of atypical adenomas and pituitary carcinomas. The aim of this study is the analysis of activation of cell-cycle inhibitors p16 and p21, p53 protein and proliferative Ki-67 index in types and subtypes of PAs. These markers are also analyzed in the normal anterior pituitary. The investigation is performed on 345 PAs, which paraffin block were used as donor blocks for tissue micro array (TMA) construction. The control group was made of normal anterior pituitaries, which were a part of resection specimen for surgery of PAs...