Gynaecological carcinomas (ovarian, endometrial, cervical, vaginal, vulvar and breast) are among the ones leading to the highest cancer-related deaths worldwide. The presence of germline pathogenic... Show moreGynaecological carcinomas (ovarian, endometrial, cervical, vaginal, vulvar and breast) are among the ones leading to the highest cancer-related deaths worldwide. The presence of germline pathogenic variants in the breast cancer susceptibility genes BRCA1 and BRCA2 is associated with an increased risk for breast and ovarian cancer as well as other cancers. The BRCA proteins play a crucial role in the homologous recombination (HR) pathway, which is the only DNA damage repair pathway that can repair DNA double-strand breaks error-free. The repair of DNA damage by HR is crucial to maintain genomic integrity. Patients whose tumors are HR-Deficient (HRD) are particularly sensitive to platinum-based chemotherapy and poly-ADP ribose polymerase inhibitors (PARPi). BRCA1/2 deficiency, but also (epi)genetic defects in other HR-related genes or other unknown factors can lead to HRD. However, BRCA1/2 deficiency, and not HRD, is still the leading prerequisite to be eligible for PARPi therapy. In this thesis, two functional RAD51-based HRD tests (RECAP and RAD51-FFPE test), were developed and validated using gynaecological carcinomas. These functional HRD tests were benchmarked with BRCA1/2 deficiency and with other DNA-based HRD tests measuring genomic scars and mutational signatures. In addition, the prevalence of functional HRD was explored among a variety of gynaecological carcinomas. Show less
PurposeBRCA-deficient breast cancers (BC) are highly sensitive to platinum-based chemotherapy and PARP inhibitors due to their deficiency in the homologous recombination (HR) pathway. However, HR... Show morePurposeBRCA-deficient breast cancers (BC) are highly sensitive to platinum-based chemotherapy and PARP inhibitors due to their deficiency in the homologous recombination (HR) pathway. However, HR deficiency (HRD) extends beyond BRCA-associated BC, highlighting the need for a sensitive method to enrich for HRD tumors in an alternative way. A promising approach is the use of functional HRD tests which evaluate the HR capability of tumor cells by measuring RAD51 protein accumulation at DNA damage sites. This study aims to evaluate the performance of a functional RAD51-based HRD test for the identification of HRD BC.MethodsThe functional HR status of 63 diagnostic formalin-fixed paraffin-embedded (FFPE) BC samples was determined by applying the RAD51-FFPE test. Samples were screened for the presence of (epi)genetic defects in HR and matching tumor samples were analyzed with the RECAP test, which requires ex vivo irradiated fresh tumor tissue on the premise that the HRD status as determined by the RECAP test faithfully represented the functional HR status.ResultsThe RAD51-FFPE test identified 23 (37%) of the tumors as HRD, including three tumors with pathogenic variants in BRCA1/2. The RAD51-FFPE test showed a sensitivity of 88% and a specificity of 76% in determining the HR-class as defined by the RECAP test.ConclusionGiven its high sensitivity and compatibility with FFPE samples, the RAD51-FFPE test holds great potential to enrich for HRD tumors, including those associated with BRCA-deficiency. This potential extends to situations where DNA-based testing may be challenging or not easily accessible in routine clinical practice. This is particularly important considering the potential implications for treatment decisions and patient stratification. Show less
BRCA1 en BRCA2 zijn tumorsuppressor genen die betrokken zijn bij homologe recombinatie reparatie. Een kiembaanmutatie in BRCA1 of BRCA2 leidt tot het erfelijke borst- en eierstokkanker syndroom ... Show moreBRCA1 en BRCA2 zijn tumorsuppressor genen die betrokken zijn bij homologe recombinatie reparatie. Een kiembaanmutatie in BRCA1 of BRCA2 leidt tot het erfelijke borst- en eierstokkanker syndroom (HBOC syndroom). Of vrouwen met een BRCA1/2 mutatie ook een verhoogd risico hebben op het ontwikkelen van endometriumcarcinoom was tot nu toe onzeker.In dit proefschrift hebben middels functionele analyse mechanistisch bewijs geleverd dat een zeldzame subgroep van het endometriumcarcinoom, namelijk de sereuze of p53-abnormale/SCNA-hoge endometriumcarcinomen, vaak homoloog recombinatie deficiënt is. Daarnaast hebben we in een groot landelijk cohort: Hereditair Borst- en Eierstokkanker Onderzoek Nederland (HEBON), laten zien dat vrouwen met een BRCA1/2 mutatie (1) vaker endometriumcarcinomen van de p53-abnormale/SCNA-hoge subgroep ontwikkelen en dat deze tumoren ook verlies van het wildtype allel tonen, wat ondersteunt dat deze tumoren gBRCA1/2 geassocieerd zijn, en (2) een verhoogd risico hebben op het ontwikkelen van endometriumcarcinomen, waarbij het hoogste risico werd gevonden voor sereuze endometriumcarcinomen en endometriumcarcinomen van de p53-abnormale/SCNA-hoge subgroep bij BRCA1 mutatie draagsters. Tot slot, door aan te tonen dat BRCA1/2 mutaties betrouwbaar kunnen worden gedetecteerd in diagnostisch tumorweefsel, hebben we een basis gelegd voor een efficiëntere genetische work-up van eierstokkanker patiënten, die ook kan worden uitgebreid naar andere tumortypen. Show less
