Genetska variabilnost v mehanizmih popravljanja poškodb DNA kot označevalec odgovora na zdravljenje z obsevanjem pri duktalnem karcinomu in situ

Serianz, Ema (author), Trebušak Podkrajšek, Katarina (mentor), Goričar, Katja (comentor)

Duktalni karcinom in situ (DCIS) predstavlja neinvazivno obliko raka dojk, pri kateri maligne celice ostajajo znotraj mlečnih vodov in se še niso razširile v okoliško tkivo. Kljub dobri prognozi je DCIS klinično pomemben, saj lahko napreduje v bolj invazivno obliko raka. Zdravljenje običajno vključuje kirurški poseg in obsevanje, ki preprečuje ponovitve bolezni, a lahko povzroči različne neželene učinke. Obsevanje deluje tako, da povzroča poškodbe DNA v rakavih celicah, kar vodi v njihovo smrt. Te poškodbe obsegajo poškodbe baz in prelome verig DNA. Raziskave so pokazale, da genetski dejavniki pomembno vplivajo na to, kako učinkovito celice popravljajo poškodbe DNA, ki jih povzroča obsevanje. Eden od ključnih mehanizmov za popravljanje poškodovanih baz v DNA je pot popravljanja DNA z izrezovanjem baz. V magistrski nalogi smo želeli raziskati, kako genetska variabilnost v poti z izrezovanjem baz vpliva na pojav neželenih učinkov zdravljenja z obsevanjem pri bolnicah z DCIS. Prav tako nas je zanimala povezava med genetskimi dejavniki in stopnjo oksidativne poškodbe DNA, izolirane iz krvi. V longitudinalno raziskavo je bilo vključenih 199 bolnic z DCIS. Genomsko DNA bolnic z DCIS smo izolirali iz vzorcev polne venske krvi. S kompetitivnim alelno specifičnim PCR smo določili prisotnost izbranih polimorfizmov v genih XRCC1 in OGG1, ki nosita zapis za proteina, vključena v popravljanju z izrezovanjem baz. Stopnjo oksidativne poškodbe DNA pred in po obsevanju smo določili s testom ELISA za določanje koncentracije 8-hidroksigvanina v plazmi. Ugotovili smo, da določeni polimorfizmi v genu OGG1 vplivajo na stopnjo oksidativne poškodbe DNA pred in po obsevanju. Prav tako smo zaznali povezavo med nekaterimi polimorfizmi XRCC1 in OGG1 in pojavom neželenih učinkov po obsevanju. Naši rezultati potrjujejo, da genetska variabilnost v mehanizmih popravljanja DNA pomembno vpliva na občutljivost na obsevanje in tveganje za neželene učinke. Ti izsledki poudarjajo pomen individualiziranega pristopa k zdravljenju bolnic z DCIS in odpirajo možnosti za nadaljnje raziskave vpliva genetskih dejavnikov na terapevtski odziv.

• Language: Slovenian
• Keywords: duktalni karcinom in situ, obsevanje, popravljanje DNA, polimorfizem
• Work type: Master's thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2025
• PID: 20.500.12556/RUL-167982
• Publication date in RUL: 22.03.2025

Secondary language

• Language: English
• Title: Genetic variability of DNA repair mechanisms as a marker of response to radiotherapy in ductal carcinoma in situ

Abstract

Ductal carcinoma in situ (DCIS) is a non-invasive form of breast cancer in which malignant cells remain within the milk ducts and have not yet spread to the surrounding tissue. Despite its good prognosis, DCIS is clinically important as it can progress to invasive cancer. Treatment usually involves surgery and radiation therapy, which prevents recurrence but can cause various side effects. The radiation causes DNA damage in the cancer cells, leading to their death. This damage includes damage to the bases and DNA strands breaks. Previous studies have shown that genetic factors have an important influence on how efficiently cells repair the DNA damage caused by irradiation. One of the key mechanisms for repairing damaged bases in DNA is the base excision repair pathway. In this thesis, we wanted to investigate how genetic variability in the base excision repair pathway influences the occurrence of side effects of radiation therapy in patients with DCIS. We were also interested in the association between genetic factors and the extent of oxidative DNA damage in the blood. 199 patients with DCIS were included in the longitudinal study. Genomic DNA from patients with DCIS was isolated from whole venous blood samples. We used competitive allele-specific PCR to determine the presence of selected polymorphisms in the XRCC1 and OGG1 genes, which encode proteins involved in base excision repair. The degree of oxidative DNA damage before and after irradiation was determined by ELISA for 8-hydroxyguanine levels in plasma samples. We found that certain polymorphisms in the OGG1 gene influence the degree of oxidative DNA damage before and after radiation therapy. We also found an association between certain polymorphisms of XRCC1 and OGG1 and the occurrence of adverse effects after radiation. Our results confirm that genetic variability of DNA repair mechanisms has an important impact on sensitivity to irradiation and the risk of adverse effects. These findings underline the importance of an individualised approach to the treatment of patients with DCIS and pave the way for further research into the impact of genetic factors on therapeutic response.

• Keywords: ductal carcinoma in situ, radiation, DNA repair, polymorphism