Opredeljevanja vzrokov in molekularnih značilnosti dednih nagnjenosti k razvoju raka na podlagi genetske analize tumorskega in netumorskega tkiva : doktorska disertacija

Blatnik, Ana (author), Krajc, Mateja (mentor), Novaković, Srdjan (comentor)

Rak se v približno desetini vseh primerov razvije kot posledica dedne predispozicije. V naši raziskavi smo genetsko testiranje za tovrstne dedne predispozicije opravljali ob uporabi netumorskega tkiva pokojnih onkoloških pacientov. Želeli smo ugotoviti, kakšna je uspešnost takega testiranja (tudi ob starosti tkiva več kot 30 let) in vpliv na obravnavo pacientovih živečih sorodnikov. Obenem smo želeli opredeliti spekter tumorjev, ki se pojavljajo v sklopu redkih predispozicij in molekularne značilnosti tumorjev pri pacientih z zelo redkimi dednimi sindromi. Analize smo opravljali z metodo sekvenciranja naslednje generacije (NGS) in ob tem uporabili večgenske komplete/panele, razvite za namen testiranja vzorcev tumorskega tkiva. Z imunohistokemičnimi metodami smo dokazovali izražanje tumorskih supresorskih beljakovin v tumorskem tkivu. Od 160 tkivnih vzorcev pokojnikov smo jih z NGS 132 analizirali uspešno in v 19,7 % primerov dokazali patogene različice (PR), ki ogrožajo za razvoj raka. Analiza je bila uspešna za 87,9 % vzorcev, starejših od 30 let. Rezultat testiranja v skupini 40-ih pokojnic z rakom dojk pred 50. letom je v 32,5 % primerov pomembno vplival na preventivno obravnavo njihovih hčera. V primeru nosilke PR v genu BAP1 smo dokazali izgubo beljakovine BAP1 v tkivu raka dojk. V primeru nosilca PR v genu CDKN2A smo dokazali izgubo beljakovinskega produkta tega gena, p16, v tkivu nevrofibroma. Testiranje tumorskih vzorcev pacientk z drobnoceličnim karcinomom jajčnika hiperkalcemičnega tipa (SCCOHT) in pacientk s sindromom Bloom je v večini primerov dokazalo najdbe, ki bi jih glede na tip tumorja pričakovali. Naša raziskava je potrdila uporabnost tkivnih vzorcev, starejših od 30 let, za namen genetskega testiranja, ki smo ga opravljali za večji nabor genov kot v predhodnih raziskavah. Potrdili smo povezavo med zarodnimi PR v BAP1 in CDKN2A in tumorji, ki jih s temi geni praviloma ne povezujemo. Obenem smo v okviru raziskave prvi podali oceno incidence SCCOHT v odrasli populaciji in med prvimi opravili genetske analize tumorskega tkiva pacientov s sindromom Bloom.

• Language: Slovenian
• Keywords: genetske analize, dedni rak, sekvenciranje naslednje generacije, imunohistokemija, FFPE tkivo, BAP1, CDKN2A, CDC73, SMARCA4, BLM
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Year: 2023
• PID: 20.500.12556/RUL-153158
• COBISS.SI-ID: 178283523
• Publication date in RUL: 20.12.2023

Secondary language

• Language: English
• Title: Determining the causes and molecular characteristics of hereditary cancer predispositions by means of genetic analysis of tumor and non-tumor tissue : doctoral dissertation

Abstract

Approximately 10% of cancers develop in the setting of a hereditary predisposition. In our study, we performed genetic testing for hereditary cancer using non-tumor tissue of deceased cancer patients. We aimed to ascertain the feasibility of such testing (even for samples, older than 30 years) and its impact on the management of patients' living relatives. We also wanted to explore the tumor spectrum for rare predispositions and study molecular characteristics of tumors, associated with very rare hereditary syndromes. Genetic testing was performed using next-generation sequencing multigene panels, originally developed for tumor tissue analysis. We investigated the expression of various tumor suppressor genes in tumor tissue samples using immunohistochemical staining. Of our 160 tissue samples, 132 were analyzed successfully. We detected pathogenic variants (PV), associated with cancer predispositions in 19.7%. For samples older than 30 years, the analysis was successful in 87.9 % of all cases. In the group of 40 patients with breast cancer before age 50, genetic testing results changed the surveillance recommendations for their daughters in 32.5 % of cases. In tumor tissue of a breast cancer patient, known to be a carrier of a BAP1 PV, we demonstrated loss of BAP1 expression. In the case of a carrier of a CDKN2A PV, we detected loss of p16, encoded by CDKN2A, in his neurofibroma. In tumor tissue samples from patients with small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), and patients with Bloom syndrome, we mostly detected somatic aberrations typical for their tumors. Our study confirms the usefulness of tissue samples, older than 30 years for genetic testing purposes. Compared to previous studies, we used a more comprehensive gene panel for our analyses. According to our results, there appears to be an association between germline PVs in BAP1 and CDKN2A and tumors not usually seen in other carriers. We offer the first estimate of SCCOHT incidence in the adult population and present one of the first reports on genetic testing results in tumors of patients with Bloom syndrome.

• Keywords: genetic analysis, hereditary cancer, next-generation sequencing, immunohistochemistry, FFPE tissue, BAP1, CDKN2A, CDC73, SMARCA4, BLM