Cutaneous melanoma is a cancer of melanocytes, the pigment-producing cells in our skin. It is one of the most aggressive human malignancies, constituting only about 2% of all dermatological cancers but being responsible for over 75% of all deaths from skin cancer. It has recently become a major public health problem, as it is now the fifth most common cancer in the United Kingdom after its incidence more than quadrupled in the last three decades. For these reasons, understanding the biological processes that are involved in its development is of great importance for devising novel treatments and for the management of patients in the clinic. The study of the genetic factors that influence melanoma risk can uncover mechanisms that are relevant in the transition from a benign melanocyte to a malignant melanoma. Approximately 10% of all melanoma cases are familial, and about half of these familial cases can be explained by pathogenetic variants in genes such as cyclin-dependent kinase inhibitor 2A (CDKN2A), cyclin-dependent kinase 4 (CDK4), breast cancer 2 (BRCA2), BRCA1-associated protein-1 (BAP1) and in the promoter of the telomerase reverse transcriptase (TERT). However, about 50% of all familial melanoma cannot be explained by mutations in known genes. In this dissertation, I detail the methodology I followed in an effort to uncover additional high-penetrance melanoma susceptibility genes. I analysed exome and genome sequence data from a total of 184 individuals that belong to 105 melanoma-prone families from the United Kingdom, The Netherlands and Australia that did not have any pathogenetic variants in known susceptibility genes. I applied different gene prioritisation strategies and developed novel software tools in order to devise a list of plausible melanoma susceptibility candidate genes; these analyses suggested that genes regulating telomere function could be influencing melanoma risk. After performing functional experimental analyses, our research team was able to determine that carriers of rare variants in the protection of telomeres (POT1) gene, a member of the shelterin complex that safeguards telomere integrity, are at high risk for developing melanoma. We successfully described the mechanism by which this happens, showing that the variants identified either disrupt POT1 mRNA splicing or abolish the ability of POT1 to bind to telomeres, and lead to increased telomere length in carriers when compared to melanoma cases with wild-type POT1. The main finding of the work described in this dissertation is the identification of telomere dysfunction as an important contributor to the risk of developing melanoma, and possibly other cancers. Our analyses suggest that POT1 is the second most commonly mutated high-penetrance melanoma susceptibility gene reported thus far, and moreover, that rare variants in this gene constitute the first hereditary mechanism for telomere lengthening in humans.

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Ce travail de thèse illustre l’intérêt d’utiliser le séquençage de nouvelle génération (Next- Generation Sequencing ou NGS) pour améliorer le diagnostic moléculaire des formes de prédispositions aux cancers. Nous avons appliqué deux stratégies différentes, l’une basée sur l’analyse simultanée d’un panel de gènes impliqués dans une pathologie, l’autre sur l’analyse de toutes les parties codante du génome ou exome.Nous avons montré que le développement d’un panel de 10 gènes impliqués dans la carcinogenèse des cancers coliques a permis d’améliorer le diagnostic moléculaire de ces formes de cancers. Cette technologie a diminué le délai de rendu des résultats et est plus sensible que le séquençage Sanger et la QMPSF (Quantitative Multiplex PCR of Short Fragment).L’application d’une stratégie d’analyse d’exomes de trio par NGS, à l’analyse de deux formes de cancers sporadiques de phénotype extrême, cancers du sein et de l’ovaire, a permis la détection de mutations de novo portant sur des gènes impliqués dans l’oncogenèse. Pour mettre en cause ces mutations dans le phénotype, nous avons réalisé des tests fonctionnels et des études de récurrence. / The working thesis Illustre interest of the USE next generation sequencing (NGS Next- Generation Sequencing e) pay Improve Molecular diagnosis of predisposition to cancer forms. Have we applied two different strategies you in June based on the simultaneous analysis of genes not involved in panel A pathology, the Other on the analysis of all the parties of the coding genome e exome.Nous Have Shown que le development of a panel of 10 genes involved in carcinogenesis of colon cancer a Permit to improve the molecular diagnosis of forms of CES dE cancers. This technology has reduced the Delai rendering results and is more reasonable That Sanger sequencing and QMPSF (Quantitative Multiplex PCR of Short Fragment) .The application OF exomes an analysis by NGS trio Strategy at analysis of two forms of sporadic cancer phenotype extreme, breast cancer and ovarian cancer, permit the detection of de novo mutations on genes involved in oncogenesis. For Questioning mutations IN THESE phenotype, We Have made Functional testing and induction studies.

On average, 5-10% of all cancers occur in patients with hereditary tumors, who may have mutations in tens to hundreds of tumor predisposition genes. The phenotypes in mutation carriers overlap, and parallel analyses with sequencing panels is the method of choice in diagnostics. In our laboratory, we designed a universal panel and a targeted panel for a specific cancer, which allowed us to identify genetic alterations in patients with ovarian cancer, breast cancer, melanoma, and other cancers in the Czech Republic. The results of next generation sequencing (NGS) analyses show that the most frequent genetic alteration in ovarian cancers patients in the Czech Republic are hereditary mutations in BRCA1 (in 24% of unselected patients) and in malignant melanoma patients CDKN2A (in 2% of high risk patients). The presence of hereditary alterations is a clinically significant phenomenon affecting the prognosis and treatment of the disease. However, the interpretation of NGS findings is complicated by the presence of variants of unknown significance (VUS). We participate in the interpretation of VUS in the main predisposing genes BRCA1 and BRCA2 within the international consortium ENIGMA (Evidence-based Network for the Interpretation of Germline Mutant Alleles). Our and international results of the most...

Ovarian cancer (OC) is the deadliest gynecologic malignancy with a substantial proportion of hereditary cases and a frequent association with breast cancer (BC). Genetic testing facilitates preventive management for carriers of mutations in OC-susceptibility genes. However, the prevalence of germline mutations varies among populations and many rarely mutated OC predisposition genes remain to be identified. We analyzed 219 genes in 1333 Czech OC patients and 2278 population-matched controls (PMC) using next-generation sequencing. Altogether, 427/1333 (32%) patients and 58 /2278 (2,5%) PMC carried pathogenic mutations in 18 known/anticipated OC predisposition genes. Mutations in BRCA1, BRCA2, RAD51C, RAD51D, BARD1 and mismatch repair genes conferred a high OC risk (with OR>5). Mutations in BRIP1 and NBN were associated with moderate risk (both OR ≥2 - <5). BRCA1/2 mutations dominated in almost all clinicopathological subgroups including sporadic borderline tumors of ovary (BTO). Analysis of remaining 201 genes revealed somatic mosaics in PPM1D and germline mutations in SHPRH and NAT1 associating with a high/moderate OC risk significantly; however, further studies are warranted to delineate their contribution to OC development in other populations. Results of this study demonstrate the high proportion...

Abstract Breast cancer is the most common cancer among women, and inherited predisposition is one of the major recognized causes of increased breast cancer risk. Only about half of the hereditary cases are explained by mutations in the known susceptibility genes, including the DNA damage response genes BRCA1, BRCA2 and PALB2, leaving the majority still uncovered. Identification of the missing genetic predisposing factors is important for more effective diagnostics and counseling of the risk families, and also for better understanding of the etiology and cellular characteristics of breast cancer. The first aim of this study was to investigate the cancer associations of six rare germline copy number variant (CNV) deletions, which were previously identified in breast cancer patients by a genome-wide microarray approach. The second aim was to identify novel susceptibility alleles, both protein-truncating variants and missense mutations, by next-generation sequencing (NGS) of nearly 800 DNA damage response genes in 189 hereditary breast cancer patients. The cancer-associations of all selected candidate alleles (6 CNVs, 39 protein-truncating variants and 35 missense mutations) were studied by case-control approach using DNA samples from several hundred breast cancer patients and healthy controls. The prevalence of the studied CNVs did not significantly differ between the cases and controls, but when studying the associations with specific clinical parameters, deletion in the CYP2C19 gene showed enrichment in the breast cancer patients with hormonally triple-negative tumors (p=0.021). As CYP2C19 functions in estrogen metabolism, the results indicate that disturbance of hormonal balance due to enzyme defects may predispose specifically to the estrogen receptor-negative subtype of breast cancer. Two protein truncating-variants, TEX15 c.7253dupT and FANCD2 c.2715+1G&gt;A showed significant breast cancer association in the Northern Finnish cohort (p=0.018 and p=0.036, respectively). Similarly, two of the studied missense variants, RECQL p.Ile156Met (p=0.043) and POLG p.Leu392Val (p=0.010), were enriched in the breast cancer cases. Thus, this study provided novel connections between increased breast cancer risk and inherited mutations in TEX15, FANCD2 and POLG genes, and further supported the recently established role of RECQL as a breast cancer susceptibility gene. / Tiivistelmä Rintasyöpä on naisten yleisin syöpä, ja perinnöllinen alttius on yksi merkittävimmistä sairastumisriskiin vaikuttavista tekijöistä. Tunnetuimpia alttiustekijöitä ovat mutaatiot BRCA1-, BRCA2- ja PALB2-DNA-vauriovastegeeneissä, mutta ne yhdessä muiden altistavien geenimutaatioiden kanssa selittävät kuitenkin vain noin puolet perinnöllisistä rintasyöpätapauksista. Uusien alttiusgeenien löytäminen mahdollistaa tehokkaamman diagnostiikan ja korkeassa syöpäriskissä olevien sukujen perinnöllisyysneuvonnan, sekä auttaa ymmärtämään syvemmin rintasyövän etiologiaa ja syntymekanismeja solutasolla. Tämän väitöskirjan ensimmäisenä päämääränä oli tutkia tarkemmin aiemmin genominlaajuisella mikrosirumenetelmällä rintasyöpäpotilailta tunnistettujen harvinaisten perinnöllisten DNA-kopiolukuvariaatioiden (CNV) yhteyttä rintasyöpäriskiin. Toisena tavoitteena oli tunnistaa uusia rintasyöpäalttiusalleeleja, sekä proteiinitrunkaatioita että missense-mutaatioita, hyödyntämällä uuden sukupolven sekvensointitekniikkaa, jonka avulla tutkittiin mutaatioita lähes 800 DNA-vauriovastegeenistä 189 pohjoissuomalaiselta rintasyöpäpotilaalta. Valittujen kandidaattialleelien (6 deleetion aiheuttavaa CNV:tä, 39 proteiinitrunkaatiota ja 35 missense-mutaatiota) yhteyttä rintasyöpään tutkittiin tapaus-verrokkimenetelmällä käyttäen DNA-näytteitä usealta sadalta rintasyöpäpotilaalta ja terveeltä kontrollihenkilöltä. Tutkittujen CNV:iden esiintyvyydessä ei ollut merkitseviä eroja potilaiden ja kontrollien välillä, mutta tarkasteltaessa yhteyttä potilaiden kasvaimista saatuihin kliinisiin parametreihin, deleetio CYP2C19-geenissä oli yleisempi hormonaalisesti kolmoisnegatiivisissa rintatuumoreissa kuin muissa tuumorityypeissä (p=0.021). Koska CYP2C19 on estrogeenimetaboliaan osallistuva entsyymi, sen viallinen toiminta voi mahdollisesti altistaa erityisesti estrogeenireseptorinegatiiviselle rintasyövälle. Kaksi tutkituista proteiinitrunkaatioista, TEX15 c.7253dupT ja FANCD2 c.2715+1G&gt;A, olivat rikastuneet perinnöllisessä rintasyöpäpotilasaineistossa verrattuna kontrolleihin (p=0.018 ja p=0.036). Myös kaksi missense-alleelia, RECQL p.Ile156Met (p=0.043) ja POLG p.Leu392Val (p=0.010), olivat yleisempiä rintasyöpäpotilailla. Tulokset osoittivat uuden yhteyden kohonneen rintasyöpäriskin ja perinnöllisten muutosten TEX15-, FANCD2- ja POLG-geenien välillä, sekä tukivat aiempia tutkimustuloksia, joiden mukaan RECQL on kohtalaisen riskin rintasyöpäalttiusgeeni.

Abstract Breast cancer is the most common malignancy in women and it is strongly influenced by hereditary risk factors. So far, most of the breast cancer-associated genes, including BRCA1/2, have been identified among those that encode proteins involved in DNA damage response (DDR) pathways. However, known genetic risk factors explain less than half of the familial risk of breast cancer. Identification of novel genes and mutations that predispose to breast cancer is important for the understanding of the mechanisms that contribute to the disease development and also for the identification of those individuals who are at high risk. The first aim of this study was to resolve the complementation groups of Finnish patients with Fanconi anemia (FA), which is a rare genetic disease caused by defects in a specific DDR pathway, and to study the role of the causative gene mutations in breast cancer predisposition. The second aim of this study was to identify novel breast cancer susceptibility genes and alleles by targeted next-generation sequencing (NGS) of multiple (~800) DDR related genes. In both approaches, the identified gene mutations were subjected to case-control association analysis utilizing DNA samples of over 1,000 breast cancer cases and 1,000 healthy controls. Investigation of the Finnish FA patients revealed six different disease-causing mutations in three different genes (FANCA, FANCG and FANCI). All of the studied mutations were recurrent in the Finnish population but did not associate with breast cancer. Targeted NGS identified three novel potential breast cancer susceptibility genes. A significant enrichment of TEX15 c.7253dupT and FANCD2 c.2715+1G&gt;A mutations was observed among the hereditary breast cancer cases (P = 0.018 and P = 0.036, respectively). The strongest evidence was found for a Finnish founder mutation in MCPH1 (c.904_916del), which associated with breast cancer susceptibility both in familial (P = 0.003, OR 8.3) and unselected (P = 0.016, OR 3.3) patient cohorts. The tumor suppressive function of MCPH1 was indicated by the loss of the wild-type allele of MCPH1 in 40% of the studied carrier tumors. Furthermore, carriers exhibited a significant increase in genomic instability measured by spontaneous chromosomal rearrangements in peripheral blood lymphocytes. / Tiivistelmä Rintasyöpä on naisten yleisin syöpä. Sairastumisriskiin vaikuttavat voimakkaasti perinnölliset alttiustekijät, ja suurin osa tähän asti tunnistetuista rintasyöpäalttiusgeeneistä, kuten BRCA1/2, koodaa DNA-vauriovasteessa (DDR) toimivia proteiineja. Tunnistetut tekijät selittävät yhä kuitenkin vain alle puolet rintasyövän perinnöllisestä alttiudesta. Uusien alttiusgeenien tunnistaminen on tärkeää rintasyövän patomekanismien ymmärtämiseksi sekä korkean rintasyöpäriskin omaavien henkilöiden tunnistamiseksi. Tämän tutkimuksen tarkoituksena oli määrittää viallisesta DDR-signaalinsiirtoreitistä johtuvan Fanconin anemian (FA) komplementaatioryhmät suomalaisilta FA-potilailta sekä tutkia sairauden taustalla olevien geenimutaatioden yhteyttä rintasyöpäriskiin. Uusia alttiusgeenejä etsittiin myös kohdennetulla uuden sukupolven sekvensointimenetelmällä, jonka avulla tutkittiin yhtäaikaisesti n. 800 DDR-geeniä. Molemmilla lähestymistavoilla tunnistettujen geenimuutosten yhteyttä rintasyöpään selvitettiin tapaus-verrokkitutkimuksen avulla, jossa tutkittiin DNA-näytteitä yli tuhannelta rintasyöpäpotilaalta sekä yli tuhannelta terveeltä henkilöltä. Suomalaisten FA-potilaiden geenimuutoksia selvittävässä tutkimuksessa tunnistettiin yhteensä kuusi mutaatiota kolmessa eri geenissä (FANCA, FANCG ja FANCI). Kaikki tutkimuksessa tunnistetut mutaatiot olivat toistuvia suomalaisessa väestössä, mutta merkitsevää assosiaatiota näiden mutaatioiden ja rintasyöpäalttiuden välillä ei havaittu. DDR-geenien sekvensoinnin avulla tunnistettiin kolme uutta mahdollista rintasyöpäalttiusgeeniä. Tutkimuksessa havaittiin TEX15 c.7253dupT ja FANCD2 c.2715+1G&gt;A mutaatioiden rikastuminen perinnöllisessä rintasyöpäaineistossa (P = 0.018 ja P = 0.036). Merkittävin yhteys rintasyöpäalttiuden kanssa todettiin MCPH1-geenin perustajamutaatiolle (c.904_916del). Tämä mutaatio assosioitui rintasyöpäalttiuden kanssa sekä perinnöllisessä (P = 0.003, OR 8.3) että valikoimattomassa potilasaineistossa (P = 0.016, OR 3.3). Useissa mutaatiokantajien tuumoreissa (40 %) normaali MCPH1 vastinalleeli oli hävinnyt, mikä viittaisi siihen, että MCPH1 toimii tuumorisuppressorina. Mutaatiokantajilla todettiin myös kohonnut määrä kromosomaalisia muutoksia veren periferaalisissa lymfosyyteissä, mahdollisesti kohonneeseen genomiseen epävakauteen liittyen.

Parmi les cancers du sein, 5 à 10% serait associé à une prédisposition génétique familiale. La prise en charge des patients prédisposés nécessite une bonne définition des risques de cancer. L’identification de l’altération moléculaire causale dans chacune de ces familles est donc un enjeu essentiel dans la prise en charge médicale. Deux gènes, BRCA1 et BRCA2, sont associés à une prédisposition majeure au cancer du sein et de l’ovaire depuis le milieu des années 1990, expliquant environ 15% des formes héréditaires. L’analyse moléculaire de ces deux gènes est désormais réalisée en routine pour la recherche de variations nucléotidiques et plus récemment de remaniements géniques ce qui a permis d’améliorer le taux de détection de mutations délétères. Cependant, pour près de 85% des familles avec une agrégation familiale ou un âge anormalement jeune de cancer du sein, aucune mutation délétère n’a pu être mise en évidence. Dans ce contexte, mon travail de thèse a eu pour objectif de tester plusieurs hypothèses permettant d’expliquer les risques de cancer du sein observés chez des familles montrant l’absence de mutation des gènes BRCA1 et BRCA2. Nous avons ainsi recherché des mécanismes d’altération rarement explorés pour les gènes BRCA1 et BRCA2, et enfin analysé d’autres gènes candidats dont le gène CDH1 et huit autres gènes impliqués dans la réparation de l’ADN. Nous avons pu mieux caractériser des remaniements sur les gènes BRCA1 et BRCA2. Enfin, nous avons pu évaluer l’impact de variants de signification inconnue et des réarrangements détectés par l’étude de leurs transcrits. Dans un premier temps, nous avons mis en place et validé de nouvelles approches techniques de détection et de caractérisation : la CGH-array dédiée, la qPCR-HRM et le peignage moléculaire. Ces techniques ont ensuite été utilisées pour étudier les remaniements géniques et leur fréquence pour onze gènes candidats à la prédisposition au cancer du sein à partir de 472 familles négatives aux mutations délétères BRCA1 et BRCA2. Parmi ces 11 gènes, nous pouvons conclure que les remaniements géniques détectés concernent principalement les gènes BRCA1 et BRCA2, et à un moindre degré le gène CHEK2. En appliquant ces techniques, nous avons pu décrire de nouveaux événements, deux larges délétions et une duplication intronique, pour les gènes CDH1 et BARD1, ouvrant de nouvelles perspectives sur l’étude des transcrits alternatifs. Nous avons en particulier pu décrire la grande diversité des réarrangements délétères en 5’ du gène BRCA1. L’enjeu est ensuite l’interprétation de ces événements. Notre étude des transcrits a permis de décrire un variant exonique d’épissage entraînant une délétion de l’exon 23 au niveau du transcrit BRCA1. Nous avons aussi validé la pathogénicité d’un réarrangement en phase de l’exon 3 de BRCA2 par une étude quantitative du transcrit et une évaluation de la coségrégation. Au final, moins de 1% de nouveaux remaniements ont été mis en évidence. Ce travail est riche d’enseignement pour les nouvelles investigations à mettre en place pour les familles prédisposées. En dehors de la technique d’identification, il est nécessaire de développer des stratégies de validation basées principalement sur la quantification des effets de ces altérations au niveau de l’ARN et des protéines. Cependant, il manque encore de nombreux chaînons pour expliquer l’héritabilité des cancers du sein. Les études sur les nouveaux gènes candidats et l’avènement des techniques de séquençage pangénome à haut débit, devraient permettre d’avoir une meilleure vision des phénomènes pathobiologiques liés à la prédisposition au cancer du sein. / Five to 10% of breast cancers are linked to a genetic predisposition. The management of patients at risk requires a good definition in the risk of cancer. The identification of causal molecular alterations in each of these families is a key issue in medical care. Two genes, BRCA1 and BRCA2, are related with the greatest susceptibility to breast cancer and ovarian cancer since the mid-1990s, accounting for about 15% of hereditary forms. Molecular analysis of these two genes is now routinely performed for the detection of nucleotide variations and more recently large rearrangements which have improved the detection rate of deleterious mutations. However, for more than 85% of families, no mutation explains familial aggregation or unusual young age of breast cancer onset. In this context, my thesis aimed at testing several hypotheses to explain the risks of breast cancer observed in families without any identified mutations in the BRCA1 and BRCA2 genes. We investigated some mechanisms of genic rearrangements rarely explored for BRCA1 and BRCA2 genes, and finally investigated other candidate genes, especially CDH1 gene and eight other genes involved in double-strand DNA repair. We have better characterized some rearrangements in the BRCA1 and BRCA2 genes. Finally, we applied RNA quantitative approaches to better assess the impact from variants of unknown significance and detected rearrangements. Initially, we developed and validated new technical approaches for detection and characterization such as dedicated CGH-array, qPCR-HRM and molecular combing. Rare large germline rearrangements and their frequency in eleven candidate genes for susceptibility to breast cancer were studied among 472 families negative by routine testing for BRCA1 and BRCA2 genes. Of these 11 genes, we conclude that genic rearrangements are found then mainly in the BRCA1 and BRCA2 genes, and to a lesser extent in the CHEK2 gene. We were able to describe two large intronic deletions and one duplication for the CDH1 and BARD1 genes, opening new perspectives on the regulation of their alternative transcript. In particular, we described the wide diversity of new rearrangements involving the 5' region of the BRCA1 gene. Then, it is necessary to validate and interpret those new events. Our transcript analysis described a new exonic variant causing the splice deletion of exon 23 in BRCA1 gene. We have developed tools to validate an in-frame large rearrangement of BRCA2 exon 3 with some transcript quantitative approaches and disease cosegregation.Finally, less than 1% of new rearrangements have been identified. This work is instructive for further investigations to establish molecular etiology in those families with breast cancer predisposition. Not only by applying new technologies, it is necessary to develop other strategies based primarily on quantifying effects of these alterations on transcription and traduction. However, it still lacks many links to explain the heritability of breast cancer. The combination of new candidate genes studies and the advent of high-throughput sequencing are expected to give a better vision of pathobiological phenomena related to the breast cancer predisposition.