Pathogenic APC Variants in Latvian Familial Adenomatous Polyposis Patients.

Background and objectives: Familial adenomatous polyposis is one of the APC-associated polyposis conditions described as genetically predetermined colorectal polyposis syndrome with a variety of symptoms. The purpose of this study was to determine sequence variants of the APC gene in patients with familial adenomatous polyposis (FAP) phenotype and positive or negative family history. Materials and Methods: Eight families with defined criteria of adenomatous polyposis underwent molecular genetic testing. Coding regions and flanking intron regions of the APC gene were analyzed by Sanger sequencing. Results: Eight allelic variants of the APC gene coding sequence were detected. All allelic variants of the APC gene were predicted to be pathogenic based on criteria according to the "Joint Consensus Recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology" (2015), four of them c.1586_1587insAT, c.2336delT, c.3066_3067insGA, and c.4303_4304insC, were considered novel. Conclusions: The timely molecular genetic analysis of APC germline variants and standardized interpretation of the pathogenicity of novel allelic variants has a high impact on choice for treatment, cancer prevention, and family genetic counseling.

Initial results of colorectal polyposis research in Latvia.

AIM: Patients suffering from colorectal polyps are more likely to develop a malignant condition with poor prognosis. The aim of the study is to investigate clinical and molecular features of colorectal polyposis syndromes in Latvia in order to offer and provide predictive genetic testing for the affected families, as well as to evaluate the frequency of familial adenomatous polyposis (FAP) in Latvia. PATIENTS AND METHODS: Six polyposis patients along with three of their relatives were included in this study. Two patients were selected from the colorectal cancer database (from a total of 2,552), and four patients not affected with colorectal cancer (CRC) were referred from the endoscopic facility of our hospital. All the patients were examined during the period from January 1st, 2000 until June 30th, 2007. Clinical data, histological examinations and family cancer histories of the respective patients were evaluated. Screening for germline APC mutations was performed in five patients and their relatives. In addition, all patients underwent genetic counseling. RESULTS: Two patients out of 2,552 from the CRC Hereditary Cancer Institute database fulfilled the clinical criteria for FAP. Thus, the frequency of FAP is 0.08% (2/2,552) of all CRC cases, and comprises approximately 0.0003% of the population of Latvia (7/22 million inhabitants). Unknown polyposis was identified in two cases. Pathogenic APC gene mutations were detected in five out of seven examined patients and their relatives. Two of the mutations (c.3942delG:p.Arg1314SerfsX7 and c.3286C > T;p.Gln1096X) are novel. CONCLUSION: In this study, we report the first four APC mutation-positive FAP cases in Latvia. The present frequency of FAP is lower than that reported in Finland, Lithuania, and other neighbouring countries, but the numbers might increase if a more systematic identification approach is used. Initial molecular examinations reveal partially unique spectrum of APC gene mutations.

Nationwide study of clinical and molecular features of hereditary non-polyposis colorectal cancer (HNPCC) in Latvia.

BACKGROUND: The mutational spectrum of mismatch repair (MMR) genes in the Baltic States has been reported to be quite similar to that in Poland; however during a country-wide study considerable differences in the population of Latvia were discovered. This study was undertaken to investigate the clinical and molecular features of HNPCC in Latvia. MATERIALS AND METHODS: Family cancer histories were collected, from January 2000 until October 2003, for 702 consecutive hospital based colorectal cancer (CRC) cases. In families suspected of having a history consistent with hereditary non-polyposis colorectal cancer (HNPCC), DNA testing for MLH1, MSH2 and MSH6 genes was performed. Immunohistochemical examination of the normal and the cancer tissue from large bowel tumors was undertaken for MSH2 and MSH6 protein expression in 182 out of 702 (26%) of the cases. RESULTS: Among the 702 CRC patients only 1 (0.14%) fulfilled the Amsterdam criteria. Thirteen (1.9%) cases matched the criteria for suspected HNPCC and 10 (1.4%) cases matched the late onset HNPCC criteria. Altogether in 7 out of 702 (1%) cases MMR gene mutations were detected: 2 in MLH1, 3 in MSH2 and 2 in MSH6 gene. Only one out of the seven mutations was registered in the Human Genome Mutation Database and the ICG (International Collaborational Group)-HNPCC mutation data base. Negative MSH2 and MSH6 protein expression was detected in 4 (2.2%) and 18 out of 182 (9.9%) cases respectively. CONCLUSION: The role of the classical Amsterdam criteria in diagnosing HNPCC in CRC patients from Latvia is very limited and diagnostic criteria for suspected HNPCC are the most effective. The frequency of constitutional mutations within the MMR genes is 1% of all newly diagnosed CRC cases and the spectrum of mutations is potentially characteristic.

Population screening for hereditary and familial cancer syndromes in Valka district of Latvia.

BACKGROUND: The growing possibilities of cancer prevention and treatment as well as the increasing knowledge about hereditary cancers require proper identification of the persons at risk. The aim of this study was to test the outcome of population screening in the scientific and practical evaluation of hereditary cancer. METHODS: Population screening for hereditary cancer was carried out retrospectively in a geographic area of Latvia. Family cancer histories were collected from 18642 adults representing 76.6% of the population of this area. Hereditary cancer syndromes were diagnosed clinically. Molecular testing for BRCA1 founder mutations 300 T/G, 4153delA and 5382insC was conducted in 588 persons who reported at least one case of breast or ovary cancer among blood relatives. RESULTS: Clinically, 74 (0.40%; 95% confidence interval (CI): 0.32 - 0.50%) high-risk and 548 (2.94%, 95% CI: 2.71 - 3.19) moderate-risk hereditary cancer syndromes were detected covering wide cancer spectrum. All syndromes were characterised by high cancer frequency among blood relatives ranging 8.6 - 46.2% in contrast to spouse correlation of 2.5 - 3.6%. The mean age of cancer onset ranged 38.0 - 72.0 years in different syndromes. The BRCA1 gene mutations were identified in 10 (1.7%; 95% CI: 0.9 - 3.1%) probands. Families with established BRCA1 gene founder mutations were identified with the frequency 1:2663 clinically screened persons. CONCLUSIONS: Population screening is a useful practical tool for the identification of persons belonging to families with high frequency of malignant tumours. The whole hereditary and familial cancer spectrum along with the age structure was identified adjusting follow-up guidelines. Another benefit of the population screening is the possibility to identify oncologically healthy persons belonging to hereditary and familial cancer families so that appropriate surveillance can be offered. Clinical diagnostics is appropriate for population screening purposes; molecular investigation provides additional information. In collaboration with family doctors, the screening is technically manageable as characterised by high compliance.

Clinical, molecular and geographical features of hereditary breast/ovarian cancer in latvia.

INTRODUCTION: The aim of the study is to evaluate the incidence and phenotype-genotype characteristics of hereditary breast and ovarian cancer syndromes in Latvia in order to develop the basis of clinical management for patients and their relatives affected by this syndrome. MATERIALS AND METHODS: In 2002-2004 in two Latvian oncology hospitals (Liepãja Oncology Hospital and Daugavpils Oncology Hospital) cancer family histories were collected from 287 consecutive patients with breast and ovarian cancer. In all cases, when it was possible to obtain the blood sample, DNA testing for founder mutations in the BRCA1 gene was performed. RESULTS: Among 287 family cancer histories analysed in 8 (2.8%) cases criteria of hereditary breast cancer (HBC) were fulfilled and in 5 (1.7%) cases hereditary breast and ovarian cancer (HBOC) was diagnosed. In 50 (17.4%) cases we have suspicion of hereditary breast cancer (HBC susp.) and in 8 (2.8%) cases - suspicion of hereditary breast and ovarian cancer (HBOC susp.). We have one (0.3%) case with hereditary ovarian cancer (HOC). DNA testing of founder mutations in the BRCA1 gene (exon 20 (5382 insC) exon 5 (300T/G), exon 11, 17 (4153delA)) for 178/287 (62%) patients was performed. In 9/287 (4.9%) cases we found a mutation in the BRCA1 gene. 4 mutations were detected in exon 11, 17 (4153delA) and 4 mutations in exon 20 (5382 insC) and 1 in exon 5. CONCLUSIONS: Existing pedigree/clinical data suggest that in Latvia the clinical frequency of hereditary breast and ovarian cancer is around 5% of consecutive breast and ovarian cancer patients and suspicion of the syndrome is observed in another 20% of cases. Frequency of BRCA1 founder mutations is 5% of all consecutive breast and ovarian cancers. Considerable geographical differences in the clinical and molecular frequency of hereditary breast ovarian cancer have been observed in Latvia.