[Genetics of Colorectal Tumorigenesis (Possibilities of Testing and Screening Prediction of Hereditary Form of Colorectal Cancer--Lynch Syndrome)]. / Genetika tumorigenézy nádorov kolorekta (moznosti testovania a screeningovej predikcie dedicnej formy ochorenia--Lynchovho syndrómu).

Colorectal cancer is currently one of the most frequent cancers in developed countries. Understanding the molecular principles of its pathogenesis has recently come into focus of many oncogenetic studies. Colorectal cancer also represents an ideal model for the study of molecular basis of cancerogenesis owing to the wide availability of its precursor lesions and the existence of several notorious genetic predispositions such as familial adenomatous polyposis and Lynch syndrome. The classical model of colorectal tumorigenesis, described by Fearon and Vogelstein, suggested the idea of a conventional progression from adenoma to carcinoma. It was based on a careful analysis of mutations occurring within particular stages of carcinogenesis with regards to their stepwise accumulations leading to neoplastic transformation of the colonic epithelium. Recently, new evidence has pointed to an alternative model of colorectal tumorigenesis introducing the concept of serrated precursors. This alternative pathway, known as the serrated pathway, has provided a new perspective on colorectal cancer development. Nowadays, three molecular pathways leading to colorectal tumorigenesis are recognized: 1. the chromosomal instability pathway typified by familial adenomatous polyposis; 2. the mutator pathway characterized by inactivation of DNA mismatch repair genes such as in Lynch syndrome or a number of sporadic colorectal cancers; 3. the hypermethylation serrated neoplasia pathway characterized by excessive methylation of some CpG islands in the promoter region of certain genes (positive CpG islands methylator phenotype) (CIMP+).

[Possibilities of genetic diagnostics of intestine tumour and inflammatory diseases in Slovakia]. / Moznosti genetickej diagnostiky nádorových a zápalových ochorení criev na Slovensku.

In recent years, gastroenterologists focused their interest on finding the genetic background of inflammatory bowel disease and colon cancer. NOD2/ CARD15 gene is still the most investigated gene of all known genes and its mutations can explain approximately 20% of genetic predisposition to Crohns disease. From later identified genes that play an important role in the etiology of Crohns disease, the IL23R and ATG16L1 genes have a perspective place. In the case of hereditary colorectal cancer, we can select by the help of genetic diagnostics, the group of patients with high risk of colon cancer, which requires more intensive monitoring. The aim is to find out the colon cancer in the early, treatable stage. In practical terms, genetic diagnostics of inflammatory bowel disease and colon cancer has no screening and only poor prognostic importance. It is pleasant, that the Slovak genetic workplaces are interested in this issue and in accordance with modern trends they try to expand its diapason.

STK11/LKB1 germline mutations in the first Peutz-Jeghers syndrome patients identified in Slovakia.

Peutz-Jeghers syndrome (PJS) is characterized by number of hamartomatous polyps in the gastrointestinal tract and by mucocutaneous hypermelanocytic lesions at different sites. Older patients have an increased risk of the cancers of small intestine, stomach, pancreas, colon, esophagus, ovary, testis, uterus, breast and lung. In majority of PJS cases, the germline mutations in serine/threonine kinase STK11/LKB1 gene were found to be associated with disease. Here we report the results of a first mutational screen of STK11/LKB1 in PJS patients characterized in Slovak population. The first patient with unusual carcinoma of duodenum was a sporadic case and carried c.842delC change residing in a mutational C6 repeat hotspot. Neither the polyp nor the tumor of the patient displayed the loss of heterozygosity at the site of mutation suggesting different mechanism involved in the formation of polyp and tumor in this case. The second patient belonged to a three-generation family with typical PJS features but not cancers. Interestingly, the patient displayed concomitant occurrence of adenomatous and hamartomatous polyps. Molecular analysis revealed an IVS2+1A>G mutation that alters the second intron 5' splice site and was shown to lead to aberrant splicing mediated by the U12-dependent spliceosome. The same mutation was present in the 9 affected members of the family but in none of their normal relatives. We also observed novel c. IVS2+61G>A unclassified variant, and recurrent IVS2+24G>T and 3UTR+129C>T polymorphisms. Based on the achieved results, we could offer predictive genetic testing and counseling to other members of the patient's families.

The spectrum and incidence of BRCA1 pathogenic mutations in Slovak breast/ovarian cancer families.

Pathogenic germline mutations in BRCA1 and BRCA2 account for the majority of hereditary breast/ovarian cancer cases. The analysis of BRCA1 gene was carried out in 156 breast/ovarian cancer families: 82 families with strong family history and 59 families with medium family history. Generally, 31 families and 71 cases with BRCA1 pathologic mutations (14 different types) were identified in this study by combination of SSCP and direct sequencing techniques. Using approved systematic nomenclature numbering, c.5266dupC (8 families, 21 cases), c.181T>G (5 families, 11 cases), c.68_69delAG (3 families, 5 samples) and c.843_846del4 (3 families, 4 samples) were the most frequently found mutations in BRCA1 gene. Altogether these 4 mutations accounted for 61.3% of all detected pathogenic mutations in BRCA1. One novel mutation c.1166delG was detected in one family (4 cases). Frame-shift mutations were found in 21 families (46 cases), nonsense mutations in 4 families (8 cases) and missense mutations in 6 families (17 cases). Even though the 4 most frequent mutations account for 61.3% of all detected pathogenic mutations, screening of the whole BRCA1 coding region is necessary, due to the large scale of low frequency disease causing mutations in breast/ovarian cancer families in Slovakia.