Systematic molecular and clinical analysis of uterine leiomyomas from fertile-aged women undergoing myomectomy.

STUDY QUESTION: What are the distributions and associated clinical characteristics of mediator complex subunit 12 (MED12), high mobility group AT-hook 2 (HMGA2) and fumarate hydratase (FH) aberrations in uterine leiomyomas from fertile-aged myomectomy patients? SUMMARY ANSWER: These driver mutations account for the majority (83%) of tumours in fertile-aged patients. WHAT IS KNOWN ALREADY: Alterations affecting MED12, HMGA2 and FH account for 80-90% of uterine leiomyomas from middle-aged hysterectomy patients, while the molecular background of tumours from young myomectomy patients has not been systematically studied. STUDY DESIGN, SIZE, DURATION: A retrospective series of 361 archival uterine leiomyoma samples from 234 women aged ≤45 years undergoing myomectomy in 2009-2014 was examined. Associations between the molecular data and detailed clinical information of the patients and tumours were analysed. PARTICIPANTS/MATERIALS, SETTING, METHODS: DNA was extracted from formalin-fixed paraffin-embedded samples and MED12 exons 1 and 2 were sequenced to identify mutations. Level of HMGA2 expression was evaluated by immunohistochemistry. Biallelic FH inactivation was analysed with 2-succinylcysteine staining, which is an indirect method of assessing FH deficiency. All patients' medical histories were reviewed, and clinical information of patients and tumours was combined with molecular data. MAIN RESULTS AND THE ROLE OF CHANCE: The median age at operation was 34 years. The majority (58%) of patients were operated on for a single leiomyoma. Known driver mutations were identified in 83% of tumours (71% MED12; 9% HMGA2; 3% FH). In solitary leiomyomas, the MED12 mutation frequency was only 43%, and 29% were wild-type for all driver alterations. MED12 mutations were associated with multiple tumours, smaller tumour size and subserosal location. LIMITATIONS, REASONS FOR CAUTION: Although comprehensive, the study is retrospective in nature and all samples have been collected for routine diagnostic purposes. The use of paraffin-embedded samples and immunohistochemistry may have led to an underestimation of mutations. Due to the limited sample size and rarity of especially FH-deficient leiomyomas, the data are partly descriptive. WIDER IMPLICATIONS OF THE FINDINGS: The contribution of driver mutations in leiomyomas from young myomectomy patients is comparable to tumours obtained from hysterectomies of mostly middle-aged women. Our results support the earlier findings that MED12 mutations are associated with multiple tumours, smaller tumour size and subserosal location. The study emphasizes the distinct molecular background of solitary leiomyomas, and more research is needed to clarify the underlying causes of the notable proportion of wild-type leiomyomas. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by the Academy of Finland (307773), the Sigrid Jusélius Foundation, the Cancer Foundation Finland and the iCAN Digital Precision Cancer Medicine Flagship. The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

Identification of 33 candidate oncogenes by screening for base-specific mutations.

BACKGROUND: Genes with recurrent codon-specific somatic mutations are likely drivers of tumorigenesis and potential therapeutic targets. Hypermutable cancers may represent a sensitive system for generation and selection of oncogenic mutations. METHODS: We utilised exome-sequencing data on 25 sporadic microsatellite-instable (MSI) colorectal cancers (CRCs) and searched for base-specific somatic mutation hotspots. RESULTS: We identified novel mutation hotspots in 33 genes. Fourteen genes displayed mutations in the validation set of 254 MSI CRCs: ANTXR1, MORC2, CEP135, CRYBB1, GALNT9, KRT82, PI15, SLC36A1, CNTF, GLDC, MBTPS1, OR9Q2, R3HDM1 and TTPAL. A database search found examples of the hotspot mutations in multiple cancer types. CONCLUSIONS: This work reveals a variety of new recurrent candidate oncogene mutations to be further scrutinised as potential therapeutic targets.

Mutation analysis of components of the Mediator kinase module in MED12 mutation-negative uterine leiomyomas.

BACKGROUND: Kinase module of Mediator complex ('CDK8 submodule') consists of four subunits: CDK8, Cyclin C, MED12, and MED13. Recently, we reported recurrent MED12 mutations in 70% of uterine leiomyomas. The aim of this study was to analyse whether mutations in other components of the module contribute to the development of these lesions. METHODS: Mutation screening of altogether 70 MED12 mutation-negative uterine leiomyomas was carried out by direct sequencing. RESULTS: None of the tumours displayed somatic mutations in the coding regions of CDK8/CDK19, CCNC, or MED13. CONCLUSIONS: Mutations in CDK8/CDK19, CCNC, and MED13 do not frequently contribute to genesis of uterine leiomyomas.

Somatic MED12 mutations in uterine leiomyosarcoma and colorectal cancer.

BACKGROUND: Mediator complex participates in transcriptional regulation by connecting regulatory DNA sequences to the RNA polymerase II initiation complex. Recently, we discovered through exome sequencing that as many as 70% of uterine leiomyomas harbour specific mutations in exon 2 of mediator complex subunit 12 (MED12). In this work, we examined the role of MED12 exon 2 mutations in other tumour types. METHODS: The frequency of MED12 exon 2 mutations was analysed in altogether 1158 tumours by direct sequencing. The tumour spectrum included mesenchymal tumours (extrauterine leiomyomas, endometrial polyps, lipomas, uterine leiomyosarcomas, other sarcomas, gastro-intestinal stromal tumours), hormone-dependent tumours (breast and ovarian cancers), haematological malignancies (acute myeloid leukaemias, acute lymphoid leukaemias, myeloproliferative neoplasms), and tumours associated with abnormal Wnt-signalling (colorectal cancers (CRC)). RESULTS: Five somatic alterations were observed: three in uterine leiomyosarcomas (3/41, 7%; Gly44Ser, Ala38_Leu39ins7, Glu35_Leu36delinsVal), and two in CRC (2/392, 0.5%; Gly44Cys, Ala67Val). CONCLUSION: Somatic MED12 exon 2 mutations were observed in uterine leiomyosarcomas, suggesting that a subgroup of these malignant tumours may develop from a leiomyoma precursor. Mutations in CRC samples indicate that MED12 may, albeit rarely, contribute to CRC tumorigenesis.

Aryl hydrocarbon receptor interacting protein mutations seem not to associate with familial non-medullary thyroid cancer.

BACKGROUND: Over 95% of all thyroid malignancies are non-medullary thyroid carcinomas (NMTC). Familial NMTC are more aggressive and mortality is higher as compared with sporadic carcinomas. Known genetic factors do not explain all familial NMTC. Recently, thyroid disorders have been observed in families with germline mutations in aryl hydrocarbon receptor interacting protein (AIP) but, due to frequent occurrence of these conditions in the population, the significance of this co-occurrence is not clear. AIM, SUBJECTS AND METHODS: To examine whether AIP is involved in familial NMTC, we performed AIP mutation screening in 93 familial NMTC cases. In addition, the AIP status was studied in one follicular thyroid adenoma patient with a known AIP mutation from an additional cohort. RESULTS: No potentially pathogenic changes were identified, but two likely rare polymorphisms were detected. AIP mutation-positive patient's follicular thyroid adenoma showed no loss of heterozygosity or lack of immunohistochemical AIP staining. CONCLUSION: Our study indicates that germline AIP mutations are rare or do not exist in familial NMTC.

Mutation analysis of MEN1, HRPT2, CASR, CDKN1B, and AIP genes in primary hyperparathyroidism patients with features of genetic predisposition.

OBJECTIVE: Primary hyperparathyroidism (PHPT), a common endocrine condition, is usually caused by sporadically occurring parathyroid adenoma. A subset of patients carry germline mutations in genes such as MEN1 (multiple endocrine neoplasia type 1), HRPT2 (hyperparathyroidism 2), and CASR (calcium-sensing receptor) predisposing to syndromic forms of PHPT or familial isolated hyperparathyroidism (FIHP). Recently, germline mutations in two novel genes AIP (aryl hydrocarbon receptor-interacting protein) and CDKN1B (cyclin-dependent kinase inhibitor 1B) have been found to be associated with endocrine tumors. The purpose of this study was to evaluate the role of MEN1, HRPT2, CASR, AIP, and CDKN1B genes in PHPT patients with clinical features suggestive of genetic predisposition. PATIENTS AND DESIGN: Medical records of patients treated for PHPT from 1974 to 2001 at Oulu University Hospital were reviewed. Patients with multiglandular or recurrent/persistent disease, other MEN1- related manifestations, aged 40 yr or younger at onset or with a family history of PHPT/MEN1-related tumor were invited to the study. Twenty patients with previously diagnosed MEN1 were excluded. Participants were interviewed and blood samples obtained for biochemical screening and mutation analysis of MEN1, HRPT2, CASR, AIP, and CDKN1B. RESULTS: Of the 56 invited patients, 29 took part in the study. One patient was found to carry the c. 1356_1367del12 MEN1 founder mutation. Mutations in other genes were not detected. CONCLUSIONS: Apart from MEN1, mutations in other genes predisposing to PHPT seem to be rare or non-existing in Northern Finnish PHPT patients. No evidence was found for a role of AIP or CDKN1B in PHPT predisposition.

No evidence of somatic aryl hydrocarbon receptor interacting protein mutations in sporadic endocrine neoplasia.

Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene were recently observed in patients with pituitary adenoma predisposition (PAP). Though AIP mutation-positive individuals with prolactin-, mixed growth hormone/prolactin-, and ACTH-producing pituitary adenomas as well as non-secreting pituitary adenomas have been reported, most mutation-positive patients have had growth hormone-producing adenomas diagnosed at relatively young age. Pituitary adenomas are also component tumors of some familial endocrine neoplasia syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Carney complex (CNC). Genes underlying MEN1 and CNC are rarely mutated in sporadic pituitary adenomas, but more often in other lesions contributing to these two syndromes. Thus far, the occurrence of somatic AIP mutations has not been studied in endocrine tumors other than pituitary adenomas. Here, we have analyzed 32 pituitary adenomas and 79 other tumors of the endocrine system for somatic AIP mutations by direct sequencing. No somatic mutations were identified. However, two out of nine patients with prolactin-producing adenoma were shown to harbor a Finnish founder mutation (Q14X) with a complete loss of the wild-type allele in the tumors. These results are in agreement with previous studies in that prolactin-producing adenomas are component tumors in PAP. The data also support the previous finding that somatic AIP mutations are not common in pituitary adenomas and suggest that such mutations are rare in other endocrine tumors as well.

Screening for BRCA1 and BRCA2 mutations in Eastern Finnish breast/ovarian cancer families.

Familial aggregation is thought to account for 5-10% of all breast cancer cases, and high penetrance breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 explain < or =20% of these. Hundreds of mutations among breast/ovarian cancer families have been found in these two genes. The mutation spectrum and prevalence, however, varies widely among populations. Thirty-six breast/ovarian cancer families were identified from a population sample of breast and ovarian cancer cases among a relatively isolated population in Eastern Finland, and the frequency of BRCA1/BRCA2 germline mutations were screened using heteroduplex analysis, protein truncation test and sequencing. Five different mutations were detected in seven families (19.4%). Two mutations were found in BRCA1 and three in BRCA2. One of the mutations (BRCA2 4088insA) has not been detected elsewhere in Finland while the other four, 4216-2nt A-->G and 5370 C-->T in BRCA1 and 999del5 and 6503delTT in BRCA2, are recurrent Finnish founder mutations. These results add to the evidence of the geographical differences in distribution of Finnish BRCA1/BRCA2 mutations. This screen also provides further evidence for the presumption that the majority of Finnish BRCA1/BRCA2 founder mutations have been found and that the proportion of BRCA1/BRCA2 mutations in Finnish breast/ovarian cancer families is around 20%.

Blood-derived gene-expression profiling in unravelling susceptibility to recessive disease.

Identification of new disease predisposition genes with chip-based technologies typically requires extensive financial and sample resources. We have recently shown that combining peripheral blood genome and transcriptome (BGT) information in highly selected materials can be a successful low-cost approach to unravelling dominant tumour susceptibility. In this study, we extended our investigations to recessively inherited tumour predisposition, and identified a homozygous germline mutation in the damage-specific DNA binding protein 2 (DDB2) gene in a patient with several facial tumours, for which doctors had been unable to provide a diagnosis. Our results provide proof of principle that BGT is a powerful approach for both dominant and recessive genes. In addition to tumour susceptibility, the method may be useful in characterising genetic defects underlying other disease phenotypes.

Mutation analysis of aryl hydrocarbon receptor interacting protein (AIP) gene in colorectal, breast, and prostate cancers.

Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene were recently identified in individuals with pituitary adenoma predisposition (PAP). These patients have prolactin (PRL) or growth hormone (GH) oversecreting pituitary adenomas, the latter exhibiting acromegaly or gigantism. Loss-of-heterozygosity (LOH) analysis revealed that AIP is lost in PAP tumours, suggesting that it acts as a tumour-suppressor gene. Aryl hydrocarbon receptor interacting protein is involved in several pathways, but it is best characterised as a cytoplasmic partner of the aryl hydrocarbon receptor (AHR). To examine the possible role of AIP in the genesis of common cancers, we performed somatic mutation screening in a series of 373 colorectal cancers (CRCs), 82 breast cancers, and 44 prostate tumour samples. A missense R16H (47G>A) change was identified in two CRC samples, as well as in the respective normal tissues, but was absent in 209 healthy controls. The remaining findings were silent, previously unreported, changes of the coding, non-coding, or untranslated regions of AIP. These results suggest that somatic AIP mutations are not common in CRC, breast, and prostate cancers.

CHEK2 I157T associates with familial and sporadic colorectal cancer.

BACKGROUND: Recently, a functionally defective CHEK2 variant I157T has been proposed to associate with an increased risk of several types of cancer. We investigated the CHEK2 I157T variant for colorectal cancer (CRC) predisposition in a large population based study including a significant number of familial CRC cases. METHODS: We screened the CHEK2 I157T variant in a population based series of 1042 Finnish CRC patients using restriction fragment length polymorphism. Mutation status was studied for correlation with clinical characteristics and family history of CRC and other cancers. RESULTS: The frequency of CHEK2 I157T was significantly higher in CRC patients (7.8%, 76/972) than in healthy population controls (5.3%, 100/1885) (OR = 1.5, 95% CI 1.1 to 2.1, p = 0.008). The significant association of CHEK2 I157T with CRC was observed among patients with (10.4%, 14/135) and without (7.4%, 62/837) a family history of CRC (OR = 2.1, 95% CI 1.1 to 3.7, p = 0.01; OR = 1.4, 95% CI 1.0 to 2.0, p = 0.03; respectively). A trend towards higher variant frequency was also noted among patients with multiple primary tumours and a family history of any cancer. CONCLUSIONS: CHEK2 I157T associates with an increased risk of CRC: the association was observed both among familial and sporadic CRC patients. Furthermore, the higher frequency of I157T among patients with multiple primary tumours as well as those with a family history of any cancer supports a role for CHEK2 I157T as a susceptibility allele for multiple cancer types.

The MDM2 promoter polymorphism SNP309T-->G and the risk of uterine leiomyosarcoma, colorectal cancer, and squamous cell carcinoma of the head and neck.

BACKGROUND: MDM2 acts as a principal regulator of the tumour suppressor p53 by targeting its destruction through the ubiquitin pathway. A polymorphism in the MDM2 promoter (SNP309) was recently identified. SNP309 was shown to result, via Sp1, in higher levels of MDM2 RNA and protein, and subsequent attenuation of the p53 pathway. Furthermore, SNP309 was proposed to be associated with accelerated soft tissue sarcoma formation in both hereditary (Li-Fraumeni) and sporadic cases in humans. METHODS: We evaluated the possible contribution of SNP309 to three tumour types known to be linked with the MDM2/p53 pathway, using genomic sequencing or restriction fragment length polymorphism as screening methods. Three separate Finnish tumour materials (population based sets of 68 patients with early onset uterine leiomyosarcomas and 1042 patients with colorectal cancer, and a series of 162 patients with squamous cell carcinoma of the head and neck) and a set of 185 healthy Finnish controls were analysed for SNP309. RESULTS: Frequencies of SNP309 were similar in all four cohorts. In the colorectal cancer series, SNP309 was somewhat more frequent in women and in patients with microsatellite stable tumours. Female SNP309 carriers were diagnosed with colorectal cancer approximately 2.7 years earlier than those carrying the wild type gene. However, no statistically significant association of SNP309 with patients' age at disease onset or to any other clinicopathological parameter was found in these three tumour materials. CONCLUSION: SNP309 had no significant contribution to tumour formation in our materials. Possible associations of SNP309 with microsatellite stable colorectal cancer and with earlier disease onset in female carriers need to be examined in subsequent studies.

No MSH6 germline mutations in breast cancer families with colorectal and/or endometrial cancer.

BACKGROUND: The genetic background in breast cancer families with colorectal and/or endometrial cancer is mostly unknown. The functional connection between MSH6 and the known breast cancer predisposition gene product BRCA1 suggests that the MSH6 gene may also play a role in breast cancer predisposition. METHODS: We analysed 38 breast cancer families with colorectal and/or endometrial cancer for germline mutations in MSH6. RESULTS: No disease associated mutations were detected among the breast cancer families. However, mutation analysis revealed a Glu995STOP mutation in an atypical HNPCC family. The same mutation was found in a patient with both breast and colorectal carcinoma in our previous study, and haplotype analysis confirmed a common ancestral origin. The Glu995STOP mutation was further examined in an extensive series of 245 colorectal and 142 breast carcinoma patients with a family history of breast, colorectal, and/or endometrial carcinoma, and in 268 healthy population controls, but none was found to carry the mutation. CONCLUSIONS: Our results suggest that MSH6 may not be the underlying gene in breast cancer families with a history of colorectal and/or endometrial cancer. The Glu995STOP founder mutation is not a familial breast cancer predisposition allele and makes only a limited contribution to colorectal cancer burden in Finland.

p53, CHK2, and CHK1 genes in Finnish families with Li-Fraumeni syndrome: further evidence of CHK2 in inherited cancer predisposition.

Germ-line mutations in the p53 gene predispose individuals to Li-Fraumeni syndrome (LFS). The cell cycle checkpoint kinases CHK1 and CHK2 act upstream of p53 in DNA damage responses, and recently rare germ-line mutations in CHK2 were reported in LFS families. We have analyzed CHK1, CHK2, and p53 genes for mutations in 44 Finnish families with LFS, Li-Fraumeni-like syndrome, or families phenotypically suggestive of LFS with conformation-sensitive gel electrophoresis. Five different disease-causing mutations were observed in 7 families (7 of 44 families; 15.9%): 4 in the p53 gene (5 of 44 families; 11.4%) and 1 in the CHK2 gene (2 of 44 families; 4.5%). Interestingly, the other CHK2-mutation carrier also has a mutation in the MSH6 gene. The cancer phenotype in the CHK2-families was not characteristic of LFS, and may indicate variable phenotypic expression in the rare families with CHK2 mutations. No mutations in the CHK1 gene were identified. Additional work is necessary to completely unravel the molecular background of LFS.

Survival of breast cancer patients in BRCA1, BRCA2, and non-BRCA1/2 breast cancer families: a relative survival analysis from Finland.

Reports on the prognosis of familial breast cancer patients have been contradictory. True differences in survival, if they exist, would have important implications for genetic counselling and in treatment of hereditary breast cancer. We assessed the survival rates of 359 familial breast cancer patients (32 patients from BRCA1-positive families, 43 patients from BRCA2-positive families and 284 patients from BRCA1/2-negative breast cancer families) and compared them with those of all other breast cancer patients diagnosed in Finland from 1953 to 1995 (n = 59,517). Cumulative relative survival rates (RSR) were calculated by dividing the observed survival rates by the expected ones. The expected survival rates were derived from the sex, age and calendar year specific life-tables of the general population in Finland. Regression model was used to calculate relative excess risk of death (RR) and to adjust for confounding factors. The overall 5-year RSR of the patients in the BRCA1 families, BRCA2 families, non-BRCA1/2 families and among sporadic cases was 67%, 77%, 86% and 78%, respectively. However, we found no significant differences in the RR adjusted for age, stage and year of diagnosis between the different familial patient groups or the general breast cancer population. In the BRCA1 families the RR tended to be higher [RR 1.30, 95% confidence interval (CI) 0.63--2.70] and in the BRCA2 families lower (RR 0.78, 95% CI 0.39--1.57) than among the general breast cancer patient population. The RR among patients in the non-BRCA1/2 families did not differ from that of the general patient population.

BRCA1 and BRCA2 mutations among 233 unselected Finnish ovarian carcinoma patients.

Germline mutations of BRCA1 and BRCA2 predispose to hereditary breast-ovarian cancer syndrome. In Finland, 20 different BRCA1/2 mutations have been identified, and 13 of them are founder mutations that account for the vast majority of Finnish BRCA1/2 families. The purpose of our study was to determine the prevalence of BRCA1/2 mutations in unselected Finnish ovarian carcinoma patients and to evaluate the relationship between mutation carrier status and personal/family history of cancer. Two hundred and thirty-three patients were screened for all the 20 BRCA1/2 mutations known in the Finnish population. Additionally, a subgroup of patients with personal history of breast cancer and/or family history of breast and/or ovarian cancer was screened for novel BRCA1/2 mutations. Thirteen patients (5.6%) had mutations: eleven in BRCA1 and two in BRCA2. All the mutation-positive patients were carriers of the previously known Finnish BRCA1/2 mutations, and seven recurrent founder mutations accounted for 12 of the 13 mutations detected. A logistic regression analysis was used to determine the odds of mutation for ovarian carcinoma patients. The most significant predictor of a mutation was the presence of both breast and ovarian cancer in the same woman, but family history of breast cancer was also strongly related to mutation carrier status. Although BRCA1/2 mutation testing is not warranted in the general Finnish ovarian cancer patient population, patients who have also been diagnosed with breast cancer or have family history of breast or breast and ovarian cancer could benefit from referral to genetic counselling and mutation testing.

A probability model for predicting BRCA1 and BRCA2 mutations in breast and breast-ovarian cancer families.

Germline mutations in BRCA1 and BRCA2 genes predispose to hereditary breast and ovarian cancer. Our aim was to find associations between the clinical characteristics and positive mutation status in 148 breast cancer families in order to predict the probability of finding a BRCA mutation in a family. Several factors were associated with mutations in univariate analysis, whereas in multivariate analysis (logistic regression with backward selection) only the age of the youngest breast cancer patient and the number of ovarian cancer cases in a family were independent predictors of BRCA mutations. A logistic model was devised to estimate the probability for a family of harbouring a mutation in either BRCA1 or BRCA2. Altogether, 63 out of 148 families (43%) and 28 out of 29 (97%) mutation carrier families obtained probabilities over 10%. The mean probability was 55% for mutation-positive families and 11% for mutation-negative families. The models by Couch et al (1997) and Shattuck-Eidens et al (1997) previously designed for BRCA1 were also tested for their applicability to distinguish carrier families with mutations in either gene. The probability model should be a useful tool in genetic counselling and focusing the mutation analyses, and thus increasing also the cost-effectiveness of the genetic screening.

Involvement of BRCA1 and BRCA2 in breast cancer in a western Finnish sub-population.

To date, two major familial breast cancer predisposition genes, BRCA1 and BRCA2, have been identified with hundreds of germ-line mutations, accounting for 5--10% of all breast cancer and 40--60% of all inherited breast cancer. Unexpectedly elevated incidence of breast cancer, especially in the older age classes, was observed in a Western Finnish region representing a relatively homogeneous population. This study was designed to test the hypothesis that there are inherited BRCA1 or BRCA2 mutations, which confer variable and/or age-dependent penetrance on carriers. Expecting a founder effect, we searched for geographical clustering of breast cancer cases and searched for associations between the affected phenotype and shared genomic segments in the BRCA1 and BRCA2 genomic regions. Our haplotype association study did not reveal any founder effects for either BRCA1 or BRCA2. However, there were two mutations prevalent in this geographical area with minor founder effects, BRCA2 T8555G and 999del5. This is one of the few geographically ascertained, population-based studies that indicate an overall frequency of BRCA1 and BRCA2 mutations at about 2--3% in all breast cancer cases. The geographical clustering of breast cancer cases was not explained by BRCA1 or BRCA2 genes.

Germline TP53 alterations in Finnish breast cancer families are rare and occur at conserved mutation-prone sites.

We have screened for germline TP53 mutations in Finnish BRCA1 and BRCA2 mutation-negative families. This study represents the largest survey of the entire protein-encoding portion of TP53, and indicates that mutations are only found at conserved domains in breast cancer families also meeting the criteria for Li-Fraumeni/Li-Fraumeni-like syndrome, explaining only a very small additional fraction of the hereditary breast cancer cases.

Multiple founder effects and geographical clustering of BRCA1 and BRCA2 families in Finland.

In the Finnish breast and ovarian cancer families six BRCA1 and five BRCA2 mutations have been found recurrently. Some of these recurrent mutations have also been seen elsewhere in the world, while others are exclusively of Finnish origin. A haplotype analysis of 26 Finnish families carrying a BRCA1 mutation and 20 families with a BRCA2 mutation indicated that the carriers of each recurrent mutation have common ancestors. The common ancestors were estimated to trace back to 7-36 generations (150-800 years). The time estimates and the geographical clustering of these founder mutations in Finland are in concordance with the population history of this country. Analysis of the cancer phenotypes showed differential ovarian cancer expression in families carrying mutations in the 5' and 3' ends of the BRCA1 gene, and earlier age of ovarian cancer onset in families with BRCA1 mutations compared with families with BRCA2 mutations. The identification of prominent and regional BRCA1 and BRCA2 founder mutations in Finland will have significant impact on diagnostics in Finnish breast and ovarian cancer families. An isolated population with known history and multiple local founder effects in multigenic disease may offer distinct advantages also for mapping novel predisposing genes.