Detekcija i karakterizacija genomske nestabilnosti tumora mozga glijalnog porekla
Detection and characterization of genomic instability in patients with malignant glioma
Author
Milinković, VedranaMentor
Matić, Gordana
Committee members
Tanić, Nikola
Banković, Jasna
Rakić, Miodrag
Ruždijić, Sabera

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Show full item recordAbstract
Glioblastomi (GBM) predstavljaju najčešći i najmaligniji tip tumora mozga. Iako imaju istu
histopatološku sliku, primarni i sekundarni glioblastomi se razlikuju po mehanizmu nastanka
i setu karakterističnih genetičkih promena. Iako je tokom poslednjih godina došlo do
određenog poboljšanja u sagledavanju njihove kompleksne prirode, glioblastomi i dalje
predstavljaju neizlečivu bolest. Osnovni cilj ove doktorske disertacije bio je detekcija i
kvantifikacija genomske nestabilnosti, kao i identifikacija specifičnih genetičkih promena
odgovornih za promociju i progresiju malignih glioma, a sa dugoročnim ciljem da se definišu
potencijalni molekularni markeri za dijagnozu i prognozu bolesti. Sa tim u vezi, izvršena je i
analiza najčešćih poznatih genetičkih promena u gliomima: detekcija inaktivacije ključnih
tumor supresor gena (p53, PTEN i p16) i amplifikacije EGFR onkogena. Promene dva ili više
navedenih gena su prisutne u većini analiziranih uzoraka, što potvrđuje značaj višestrukih
genski...h alteracija u patogenezi glioma.
Upoređivanjem AP-PCR DNK profila tumorskog i zdravog tkiva pacijenata uočena su dva
tipa razlika: kvalitativne razlike koje nastaju usled promena u sekvenci DNK molekula i
predstavljaju manifestaciju mikrosatelitske nestabilnosti i nestabilnosti pojedinačnih
nukleotida (MIN-PIN), kao i kvantitativne razlike nastale usled amplifikacija ili delecija
većih hromozomskih regiona, pokazatelj hromozomske nestabilnosti (CIN). Oba tipa
promena su prisutna u svim analiziranim uzorcima, doprinoseći podjednako visokom stepenu
ukupne genomske nestabilnosti u oba histološka podtipa GBM. Detaljnija analiza DNK
profila je omogućila identifikaciju specifičnih promena 11 novih gena, koji do sada nisu
povezani sa progresijom glioma: LHFPL3, SGCG, HTR4, ITGB1, CPS1, PROS1, GP2,
KCNG2, PDE4D, KIR3DL3 i INPP5A. Većina identifikovanih gena ima značajnu ulogu u
procesima signalne transdukcije i ćelijske adhezije, koji su veoma značajni za nastanak i
progresiju kancera. Prisustvo promena u identifikovanim genima je, dalje, korelisano sa
kliničko-patološkim parametrima, stepenom genomske nestabilnosti i preživljavanjem
pacijenata, kao i sa statusom p53, PTEN, p16 i EGFR gena. Pokazane su statistički značajne
ko-alteracije nekih od identifikovanih gena sa p53, p16 i EGFR genima, ali nije pokazana
statistički značajna povezanost između inaktiviranog PTEN-a i bilo kojeg novog identifikovanog gena...
Glioblastoma is the most frequent and the most malignant human brain tumor. Despite a similar
histological appearance, primary and secondary glioblastomas are distinct tumor entities with
different genetic alterations but none being specific enough to distinguish them. Despite better
insight in its complex genetic nature, glioblastoma is still incurable disease, with extremely
short median survival. The purpose of this study was to detect specific genetic changes, as well
as to quantify overall level of genomic instability in samples of malignant glioma patients.
Besides, we analyzed genetic alterations of key tumor suppressors (p53, PTEN and p16) and
EGFR oncogene, commonly aberrant in glioma samples. Alterations of two or more genes were
present in majority of analyzed samples indicating importance of multiple changes for
gliomagenesis.
AP-PCR DNA profiling revealed two types of genetic differences between tumor and normal
tissue: qualitative changes which represent accumulation of c...hanges in DNA sequence and are
the manifestation of microsatellite and point mutation instability (MIN-PIN) and quantitative
changes which represent amplifications or deletions of existing chromosomal material and are
the manifestation of chromosomal instability (CIN). Both types of alterations were present in
all analyzed samples contributing almost equally to the total level of genomic instability, and
showing no differences between histological subtypes. Further investigation of alterations in
DNA profiles revealed specific changes in the following 11 genes that were not previously
associated with glioma pathogenesis: LHFPL3, SGCG, HTR4, ITGB1, CPS1, PROS1, GP2,
KCNG2, PDE4D, KIR3DL3, and INPP5A. Most of identified genes have significant role in
signal transduction or cell adhesion, which are important processes for cancer development and
progression.
The frequencies of observed alterations were correlated with clinicopathologic parameters, the
level of genomic instability and patient survival, as well as with presence of alterations in p53,
PTEN, p16 and EGFR genes. Some of the identified genes showed significant association with
p53 and p16 tumor suppressors, as well as with EGFR, but there was no significant correlation
between loss of PTEN and any of identified genes.
In conclusion, our results confirmed complexity of glioma genetic nature, emphasizing high
level of genomic instability as hallmark of this tumor type. Identified novel genes could be used as potential biomarkers for diagnosis of primary and secondary glioblastoma, as well as
predictors of patients’ outcome.