Metilacija promotora i ekspresija proteina SFRP4 u astrocitnim tumorima mozga čovjeka

master's thesis

• Title (english): SFRP4 promoter methylation and protein expression in human brain tumors
• Author: Denis Drmić
• Mentor: Anja Kafka (mentor)
• Mentor: Dubravka Hranilović (sumentor)
• Committee member: Dubravka Hranilović (predsjednik povjerenstva)
• Committee member: Maja Matulić (član povjerenstva)
• Committee member: Petra Peharec Štefanić (član povjerenstva)
• Committee member: Jasna Lajtner (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2022-02-04, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Astrocitomi su najčešća vrsta glioma, a klasificirani su u tri gradusa: difuzne
astrocitome, anaplastične astrocitome i glioblastome. Signalni put Wnt esencijalan je u
mnogim biološkim procesima, stoga njegova aberantna aktivnost ima jednu od ključnih uloga
u tumorigenezi. Obitelj proteina SFRP (engl. Secreted Frizzled-Related Protein) modulira
Wnt signalizaciju. U različitim tumorima se pokazalo da su ovi geni transkripcijski utišani
hipermetilacijom promotorske regije, što u konačnici vodi nekontroliranom prepisivanju
onkogena. Cilj rada bio je utvrditi dolazi li do različite učestalosti promjena metilacijskog
statusa promotora gena i razine ekspresije proteina SFRP4 kod različitih histoloških gradusa
astrocitoma. Ekspresija proteina SFRP4 detektirana je metodom imunohistokemije, dok je
metilacijski status promotora gena istih uzoraka ispitan metodom MS PCR. Statističkom
analizom utvrđeno je da se povećanjem gradusa tumora smanjuje ekspresija proteina SFRP4 u
astrocitomima (p=0,008), što ukazuje da bi SFRP4 mogao djelovati kao tumor supresor
inhibirajući aktivnost signalnog puta Wnt te sprječavajući nastanak i progresiju ovih tumora.
Analiza metilacije otkrila je da 72,7% difuznih astrocitoma ima metiliran promotor gena
SFRP4, dok kod viših gradusa metiliranost promotora nije detektirana. Utvrđena je statistički
značajna razlika u metilacijskom statusu gena SFRP4 između pojedinih stupnjeva malignosti
astrocitnih tumora (p<0,001). Ovi nalazi upućuju da je ekspresija SFRP4 u višim gradusima
astrocitoma regulirana nekim drugim (epi)genetičkim mehanizmima.

Abstract (english)

Astrocytomas are the most common type of glioma. They are classified into three
malignancy grades: diffuse astrocytoma, anaplastic astrocytoma, and glioblastoma. The Wnt
signaling pathway is essential in many biological processes, so its aberrant activity has an
important role in tumorigenesis. The Secreted Frizzled-Related Protein (SFRP) family
modulates Wnt signaling. It has been shown in various tumors that these genes are frequently
hypermethylated, and thereby transcriptionally silent, eventually leading to uncontrolled
transcription of oncogenes. The aim of this study was to determine whether there is a different
frequency of alterations in the methylation status and the level of SFRP4 protein expression
between different histological grades of astrocytomas. SFRP4 protein expression was detected
by immunohistochemistry, while promoter methylation of the same samples was examined by
MS PCR. Statistical analysis revealed that increase in astrocytoma grade results in SFRP4
protein expression decrease (p=0.008), indicating its role as a tumor suppressor by inhibiting
Wnt signaling pathway activity and preventing tumor formation and progression. Methylation
analysis revealed that 72.7% SFRP4 promoters in diffuse astrocytoma were methylated, while
in higher tumor grades, methylated promoters were not detected. A statistically significant
difference in the methylation status of the SFRP4 gene was found between malignancy grades
of astrocytic tumors (p<0.001). These findings suggest that some other epigenetic
mechanisms regulate SFRP4 expression in higher astrocytoma grades.

• Keywords: astrocitomi; signalni put Wnt; obitelj SFRP; MS PCR; imunohistokemija
• Keywords (english): astrocytoma; Wnt signaling pathway; SFRP family; MS PCR; immunohistochemistry
• Language: croatian
• URN:NBN: urn:nbn:hr:217:442511
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra molekularne biologije (magistar/magistra molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-02-07 13:56:22