Predisposing genes in hereditary breast and ovarian cancer

AbstractIn the present study, mutations in BRCA1 and BRCA2, the two major genes predisposing individuals to hereditary breast and ovarian cancer, were screened in Finnish and Turkish cancer families. Germline BRCA1 mutations were found in 7% (6/88) and BRCA2 mutations in 6% (5/88) of the Finnish families studied in Oulu. Two distinct BRCA1 (3745delT, 4216nt-2A→G) and three BRCA2 (999delTCAAA, 6503delTT, 9346nt-2A→G) mutations were identified, all of which are recurrently found in Finland. In the 15 Turkish cancer families studied, 5382insC and 5622C→T were detected in BRCA1, and 3414delTCAG in BRCA2. The novel 3414del4 mutation was found in a family with a case of male breast cancer.In order to determine their ages and origin, 9 recurrent Finnish BRCA1 and BRCA2 mutations were studied further as regards haplotype conservation. Common origins approximately 18–80 generations (400–1600 years) ago were demonstrated for all studied mutations by partial haplotype sharing. The majority of the mutations showed geographical clustering, supporting the theory of regional founder effects. Four of the nine mutations are unique for Finland, whereas five have also been seen elsewhere. Mutations in the 5′ end of BRCA1 tend to predispose individuals to ovarian cancer and those found in the 3′ end to breast cancer. The age of ovarian cancer onset was significantly lower for BRCA1 (51 years) than for BRCA2 mutation carriers (61 years). Germline TP53 mutations were sought in the Finnish breast cancer families found to be negative after BRCA1 and BRCA2 screening but who exhibited some phenotypic features of the Li-Fraumeni syndrome. The Asn235Ser was found in a family displaying Li-Fraumeni syndrome phenotype and the Tyr220Cys in a family with a milder Li-Fraumeni-like phenotype. The nature of both mutations as cancer-predisposing alterations was supported by means of loss of heterozygosity (LOH) and p53 immunohistochemistry studies. Regional clustering of BRCA1 and BRCA2 founder mutations enables targeted genetic tests including especially those mutations characteristic of the birthplace of each patient. Additional genes are likely to explain a large proportion of the inherited susceptibility to breast cancer in particular. Germline TP53 mutations are expected to be found in the breast cancer families with other clinical features seen in the Li-Fraumeni syndrome.Academic Dissertation to be presented with the assent of the Faculty of Medicine, University of Oulu, for public discussion in Auditorium 9 of the University Hospital of Oulu, on September 11th, 1999, at 12 noon.Abstract In the present study, mutations in BRCA1 and BRCA2, the two major genes predisposing individuals to hereditary breast and ovarian cancer, were screened in Finnish and Turkish cancer families. Germline BRCA1 mutations were found in 7% (6/88) and BRCA2 mutations in 6% (5/88) of the Finnish families studied in Oulu. Two distinct BRCA1 (3745delT, 4216nt-2A→G) and three BRCA2 (999delTCAAA, 6503delTT, 9346nt-2A→G) mutations were identified, all of which are recurrently found in Finland. In the 15 Turkish cancer families studied, 5382insC and 5622C→T were detected in BRCA1, and 3414delTCAG in BRCA2. The novel 3414del4 mutation was found in a family with a case of male breast cancer. In order to determine their ages and origin, 9 recurrent Finnish BRCA1 and BRCA2 mutations were studied further as regards haplotype conservation. Common origins approximately 18–80 generations (400–1600 years) ago were demonstrated for all studied mutations by partial haplotype sharing. The majority of the mutations showed geographical clustering, supporting the theory of regional founder effects. Four of the nine mutations are unique for Finland, whereas five have also been seen elsewhere. Mutations in the 5′ end of BRCA1 tend to predispose individuals to ovarian cancer and those found in the 3′ end to breast cancer. The age of ovarian cancer onset was significantly lower for BRCA1 (51 years) than for BRCA2 mutation carriers (61 years). Germline TP53 mutations were sought in the Finnish breast cancer families found to be negative after BRCA1 and BRCA2 screening but who exhibited some phenotypic features of the Li-Fraumeni syndrome. The Asn235Ser was found in a family displaying Li-Fraumeni syndrome phenotype and the Tyr220Cys in a family with a milder Li-Fraumeni-like phenotype. The nature of both mutations as cancer-predisposing alterations was supported by means of loss of heterozygosity (LOH) and p53 immunohistochemistry studies. Regional clustering of BRCA1 and BRCA2 founder mutations enables targeted genetic tests including especially those mutations characteristic of the birthplace of each patient. Additional genes are likely to explain a large proportion of the inherited susceptibility to breast cancer in particular. Germline TP53 mutations are expected to be found in the breast cancer families with other clinical features seen in the Li-Fraumeni syndrome

Genetic Basis of Familial Lymphoma Predisposition

Lymphomas are classified into Hodgkin and non-Hodgkin lymphomas (HL and NHL), and they are further categorized into tens of different subtypes. This thesis has focused on two rare lymphoma subtypes: nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) and primary mediastinal large B-cell lymphoma (PMBCL). Although the majority of lymphomas are sporadic, a familial component has been observed in both HL and NHL. The aim of this thesis was to study the genetic background of familial NLPHL and PMBCL predisposition. HL is classified into NLPHL and classical Hodgkin lymphoma (cHL). Germline mutations of the KLHDC8B gene have been observed in some families with cHL. In this study, the KLHDC8B gene was analyzed in four families with NLPHL, but mutations were not detected. The results suggest that germline mutations of KLHDC8B do not underlie familial NLPHL susceptibility. To clarify the genetic basis of NLPHL predisposition, a Finnish family with NLPHL susceptibility was studied with new genome-wide methods, SNP microarray and exome sequencing. Data from these two efforts were integrated, and a germline deletion of two nucleotides (c.2437-2438delAG) was observed in the NPAT gene. Subsequently, NPAT was screened in a number of familial and sporadic HL cases, and an in-frame deletion of one serine residue was found to be more frequent in the cases versus healthy controls (odds ratio 4.11, p = 0.018). Thus, NPAT was identified as a candidate gene for NLPHL predisposition. The familial risk in NLPHL was studied by using the Finnish Cancer Registry (FCR) and the Finnish Population Registries. Altogether 693 patients with NLPHL were identified, and a family member cohort comprising of the first-degree relatives of 692 patients was collected. Cancer data for the relatives was derived from the FCR. We calculated the standardized incidence ratios (SIRs) for all cancers, NHL, cHL and NLPHL in the family member cohort. In addition, the primary tumor samples from 20 first-degree relatives with HL diagnosis were histopathologically reviewed. In the family member cohort, the SIR for NLPHL was 19. Thus, a high familial risk in NLPHL was observed, suggesting that familial factors contribute to NLPHL susceptibility. An increased relative risk for NHL and cHL was also observed. We studied a family of three siblings with PMBCL and a cousin affected by diffuse large B-cell lymphoma (DLBCL). Re-examination of tumor samples revealed that all four tumors resembled each other histopathologically, proposing a common background. Genome-wide SNP array, linkage analysis and exome sequencing were performed to identify the genetic factor underlying PMBCL/DLBCL in this family. A missense change c.5533C>A (His1845Asn) was detected in the MLL gene and was the only non-database variation residing in linked regions and segregating in lymphoma affected family members. To our knowledge, this is the first description of familial clustering of PMBCL. Our findings suggest that sometimes PMBCL may arise in the context of familial predisposition, and MLL was identified as a candidate gene for PMBCL susceptibility. However, our observations are preliminary, and need to be confirmed in future studies.Lymfoomat ovat imukudoksen kasvaimia, jotka luokitellaan Hodgkinin ja non-Hodgkin lymfoomiin (HL ja NHL), sekä edelleen useisiin eri alatyyppeihin. Suurin osa lymfoomista on sattumalta syntyneitä, mutta pienen osan on havaittu esiintyvän perheittäin. Perheittäin esiintyvien lymfoomien etiologia ja geenitausta on kuitenkin huonosti tunnettu. Väitöskirjatutkimuksessa selvitettiin kahden harvinaisen lymfoomatyypin, nodulaarisen lymfosyyttivaltaisen Hodgkinin lymfooman (NLPHL) sekä primaarin mediastinaalisen suurisoluisen B-solulymfooman (PMBCL), periytyvän muodon geenitaustaa. HL:n päätyypit ovat klassinen HL sekä NLPHL. Klassisen HL:n periytyvän muodon taustalta on kuvattu geenivirheitä KLHDC8B-geenissä. Tutkimuksessa selvitetiin, löytyykö myös NLPHL-suvuissa geenivirheitä kyseisestä geenistä. KLHDC8B-geeni analysoitiin neljästä tunnetusta NLPHL-suvusta. Geenivirheitä ei todettu, mikä viittaa siihen, että KLHDC8B-geenin geenivirheet eivät ole perheittän esiintyvän NLPHL:n syy. Tutkimuksen toisessa osassa tavoitteena oli tunnistaa NLPHL:lle altistava geenivirhe suomalaisessa NLPHL-suvussa. Menetelminä käytettiin genominlaajuista SNP-mikrosirua sekä eksomisekvenointia. Menetelmien tuottamaa tietoa yhdistämällä tunnistetiin suomalaisessa NLPHL-suvussa NPAT-geenin geenivirhe. Kyseessä oli kahden emäksen deleetio c.2437-2438delAG. Jatkoselvityksissä tutkittiin suurta määrää suomalaisia ja englantilaisia HL-potilaita, ja tunnistettiin toinen NPAT-geenin muutos, jota esiintyi merkittävästi enemmän HL-potilailla kuin terveillä henkilöillä. Näin ollen tutkimuksessa tunnistettiin mahdollinen perinnöllisen NLPHL:n alttiusgeeni. Väitöstyön kolmannessa osassa arvioitiin Suomen syöpärekisteristä kerätyn tiedon avulla erityyppisten lymfoomien riskiä NLPHL-potilaiden ensimmäisen asteen sukulaisilla. Syöpärekisteristä löydettiin 693 NLPHL-potilasta, ja heidän ensimmäisen asteen sukulaisensa selvitettiin. Sukulaisten syöpätiedot kerättiin syöpärekisteristä, ja niiden perusteella tarkasteltiin eri lymfoomien esiintyvyyttä sukulaisjoukossa. Lisäksi HL:an sairastuneiden sukulaisten kasvainnäytteitä tutkittiin uudelleen hematopatologin toimesta. Tutkimuksessa havaittiin, että lähisukulaisilla oli noin 19-kertainen sairastumisriski NLPHL:an muuhun väestöön verrattuna. Tutkimustulos viittaa siihen, että familiaaliset tekijät, kuten ympäristö- tai geneettiset tekijät, voivat vaikuttaa NLPHL:n riskiin. Myös klassisen HL:n sekä NHL:n riski oli sukulaisjoukossa suurempi kuin muulla väestöllä. Väitöskirjan neljännessä osassa tunnistettiin suomalainen PMBCL-suku, joka on tiettävästi ensimmäinen raportoitu tapaus, jossa PMBCL esiintyy perheittäin. Sukua tutkittiin genominlaajuisen SNP-mikrosirun ja eksomisekvensoinnin avulla. Suvussa tunnistettiin MLL-geenin variantti c.5533C>A (His1845Asn), jota ei löytynyt terveiltä henkilöiltä tai geneettisistä tietokannoista. Näin ollen MLL-geenin muutokset saattavat liittyä perinnölliseen PMBCL-alttiuteen. Tutkimustulokset mahdollistavat uusien PMBCL-perheiden tunnistamisen, mikä edesauttaisi tämän uuden tautikokonaisuuden kliinistä ja geneettistä karakterisointia

Genetic factors in childhood cancer. Associations between tumors in childhood and adulthood, and prevalence of germline TP53 mutations

The etiology of childhood cancer is largely unknown. Approximately 1-10% of all childhood tumors are associated with known cancer predisposition syndromes. However, the contribution may be underestimated due to the failure to detect patients with genetic susceptibility for cancer when relying on known family pattern and anomalies. Growing evidence indicates that patients with genetic susceptibility to cancer may be at higher than normal risk for therapy related cancers. Increased knowledge regarding the importance of hereditary factors in the development of childhood tumors may improve the medical care of such patients by identifying those in need of more individualized treatment. In this thesis, genetic factors, familial cancers, and their associations with childhood cancer have been studied. The general aim was to investigate the importance of hereditary factors in the etiology of childhood cancer and to evaluate possible associations between childhood and adult cancers. In paper I, a national registry-based cohort of parous women with breast cancer was used to study whether the occurrence of childhood cancer in children affects the survival of mothers with breast cancer. Women who had a child with childhood cancer were found to have shorter survival compared to other parous patients with breast cancer, suggesting that hereditary factors may affect prognosis. In paper II, the occurrence of childhood cancer in families with hereditary adult cancer syndromes was investigated. Families with BRCA2-associated hereditary breast and ovarian cancer, mismatch repair gene-associated hereditary non-polyposis colorectal cancer and CDKN2A-associated malignant melanoma were found to have a higher occurrence of childhood cancer compared to the general population. No increased occurrence of childhood cancer was found in families with BRCA1-associated breast and ovarian cancers. In paper III, the incidence of childhood and adult cancer was evaluated in the extended families of patients with childhood cancer, and the frequency of germline TP53 mutations in families with multiple childhood tumors was investigated. The relatives of patients with childhood cancer were found to have an increased incidence of childhood and adult cancers, particularly of the breast and prostate. Breast and prostate cancers were observed at earlier than average ages. No germline TP53 mutations were found in families with multiple childhood tumors, which exclude TP53 mutations as a contributor to the observed excess of childhood tumors. In paper IV, a population-based material was used to confirm the prevalence of germline TP53 mutations in children with adrenocortical tumors, choroid plexus tumors and early childhood rhabdomyosarcomas and investigate whether these may be early manifestations of Li-Fraumeni syndrome (LFS). Germline TP53 mutations were found in few children with adrenocortical tumors and rhabdomyosarcomas. No mutations were found in children with choroid plexus tumors. Furthermore, neither the family history nor the observed tumor spectra in the relatives of most children with these rare tumors were suggestive of LFS. These data suggest that most children, particularly those with choroid plexus tumors or rhabdomyosarcomas, do not present early manifestations of LFS. Nevertheless, an increased cancer incidence, particularly for certain adult tumors, was found in the relatives of children with choroid plexus tumors and rhabdomyosarcomas, which suggests that other syndromes or predisposing factors may exist. In summary, this thesis adds new data suggesting that hereditary factors play a role in the development of childhood tumors. In addition, these factors may also increase the risk for adult tumors, modify the onset age of common adult tumors, and affect breast cancer prognosis. Our findings further support the need for future studies regarding the importance of genetic susceptibility to childhood cancer, particularly in families with multiple childhood tumors. Also the associations between tumors of childhood and adulthood in the same family should be further studied

Identification of tumour-associated and germ line p53 mutations in canine mammary cancer

Mutations of the tumour suppressor p53 gene are found in a number of spontaneous canine cancers and may contribute to increased cytogenetic alterations and tumour formation. Using reverse transcription and DNA amplification, we isolated p53 cDNA from normal and tumour tissue of ten canine mammary cancer patients. DNA sequencing identified p53 mutations in three of the ten patients. These included tumour-associated p53 gene mutations within exons 2 and 5 and a germ line deletion of exons 3 to 7. These results support a role for p53 inactivation in canine mammary tumour formation and breed predisposition to cancer. Such information could prove invaluable in the successful outbreeding of inherited predisposition to cancer in the dog. A putative polymorphism was also identified at codon 69 in exon 4 and we discuss the possibility that similar polymorphisms may be associated with human breast cancer. © 1999 Cancer Research Campaig