[Retrospective NGS Study in High-risk Hereditary Cancer Patients at Masaryk Memorial Cancer Institute]. / Retrospektivní NGS studie u vysoce rizikových pa-cientu s hereditární predispozicí k nádorovému onemocnení v Masarykove onkologickém ústavu.

BACKGROUND: Currently, more than 200 hereditary cancer syndromes have been described, yet, in most countries genetic testing is restricted to a narrow spectrum of genes within a limited group of people tested. METHODS: For this retrospective study we used the TruSight cancer panel (Illumina)--NGS panel targeting 94 cancer predisposition genes in order to analyze 50 high-risk cancer patients with significant personal and family history of cancer who did not carry mutations in BRCA1, BRCA2, MLH1, MSH2, MSH6, TP53 or APC genes. All pathogenic and potentially pathogenic mutations detected by NGS technology have been confirmed by Sanger sequencing. RESULTS: There were several deleterious (frame-shift/nonsense) mutations detected in ATM, BAP1, FANCC, FANCI, PMS2, SBDS, ERCC2, RECQL4 genes. Various pathogenic or potentially pathogenic (missense, predicted splice site, in-frame insertion/deletion) mutations were detected in ATM, BRIP1, CDH1, CHEK2, ERCC2, ERCC3, ERCC4, FANCA, MC1R, MEN1, MRE11A, MUTYH, PALB2, RAD51C, RET, SDHB, STK11. These mutations affect highly conserved protein domains and affect their function as proved by the available functional assays. They were confirmed to be pathogenic as an "Parent No2 " in serious recessive diseases such as Ataxia telangiectasia or Fanconi anemia. The clinical significance of the majority of detected missense variants still remains to be identified. CONCLUSION: Moderate or low penetrance variants are of limited clinical importance. Panel genetic testing in high-risk individuals with cancer provides important information concerning the cause of the investigated cancer, and may assist in the risk assesment and optimal management of the cancer, as well as in further preventive care.

[The clinical importance of a genetic analysis of moderate-risk cancer susceptibility genes in breast and other cancer patients from the Czech Republic]. / Klinický význam analýz genu stredního rizika pro hodnocení rizika vzniku karcinomu prsu a dalsích nádoru v Ceské republice.

BACKGROUND: Analysis of the major breast cancer (BC) predisposition genes BRCA1 and BRCA2 enables identification of high-risk individuals. Specialized programs enrolling the carriers of BRCA1/2 mutations facilitate an improvement in prevention and early diagnostics in asymptomatic individuals and rationalize the selection of individualized treatment in case of a BC onset. However, the carriers of mutations in the major predisposition genes represent only approximately 25% of cases among high-risk BC patients. Numerous candidate predisposing genes for breast and other cancers have recently been identified. The risk of cancer development associated with alterations in these genes is lower, and there is a considerable population variability in different regions worldwide. AIM: We have performed mutation analyses of moderate-risk cancer susceptibility genes to evaluate their clinical importance for genetic counseling in high-risk patients suffering from breast and other cancers in the Czech population. RESULTS: Czech oncological patients were analysed for mutation in ATM, CHEK2, NBS1 (NBN) and PALB2 genes. The majority of analyzed individuals represent the population of high-risk BRCA1/2-negative BC patients. CONCLUSIONS: Based on results of this study, we recommend an analysis of recurrent truncating mutations in the CHEK2 gene (the c.1100delC mutation and a large deletion affecting exons 9-10) in BRCA1/2-negative patients from high-risk BC families. A clinical assessment of missense variants in CHEK2 is not suitable. A routine mutation analysis of the ATM and NBS1 (NBN) genes is not recommended in BC patients due to the low frequency of alterations in these genes in the Czech Republic. An identification of truncating mutations in the PALB2 gene is important in BRCA1/2-negative BC patients from families with a strong history of BC (HBC families). The frequency of PALB2 mutations may be comparable to the frequency of mutations in the BRCA2 gene in Czech HBC families.

Maternal hyperphenylalaninemias in healthy Czech population of pregnant women: 30 years experience with screening, prevention and treatment.

INTRODUCTION: The increased level of phenylalanine (Phe) in maternal blood--hyperphenylalaninemia (mHPA) has a detrimental effect on the early development of healthy foetus (1965). The toxic effect causes spontaneous abortion or retards intrauterine growth, skeletal malformation, cardiac anomalies can appear. However the most frequent are microcephaly, mental retardation and hypotrophy. PATIENTS AND METHODS: Simultaneously with the introduction of obligatory "Newborn Screening Program" in CR also the facultative screening for mHPA was introduced ("Maternal Hyperphenylalaninemia Preventive Screening Program"). Since 1975 till now 222,990 healthy pregnant women (16-47 yrs) from city Prague and its area (cca 2 mil. inh.) have been screened for increased Phe in blood by Efron's chromatographic screening test (1964); Phe cut off value: 240 micromol/l. Nonfasting venous blood has been taken in 2nd-3rd month of pregnancy during the first antenatal visit. All positive cases have been verified with quantitative Phe estimation on amino acid analyzer incl. pterines analysis in urine. For differentiation of detected mHPAs the Güttler's scheme (1980) has been used. Mutations for Phe-hydroxylase gene analyzed by restriction enzyme digestion after Guldberg (1994). RESULTS: The average incidence of mHPA detected at the beginning of pregnancy was found 1:8675. The major part (65.3%) of all detected mHPA belongs to mild or moderate form of phenylketonuria (PKU) with most frequent PAH gene mutations R408W, Y414C, IVS11 nt8g-a, R158Q, IVS12ntlg-a and R261Q. 19.2% corresponds to atypical or classical PKU with prevailing mutation R408W. Only in 15.3% were detected non-PKU (persistent HPA) with mutations R408W, Y414C, IVS12ntlg-a, IV11nt8g-a and A403V. 28 offsprings born from pregnancies on low-phenylalanine diet (LPD) introduced at least 2 months before the conception and during the whole pregnancy show normal psychomotoric development. In 7 offsprings without LPD or after delayed introducing or on PLD or badly monitored showed malformations (microcephaly, hypotrophy, skeletal malformations) or died. DISCUSSION: Relatively high incidence of mHPA detected in healthy population of pregnant women of Prague area differs from findings of Buist (1989) or Levy (1994) from American pregnant women screened for mHPA from umbilical blood. We consider that screening performed at the beginning of pregnancy from nonfasting venous blood is more effective compared to umbilical blood from two reasons: the Phe level in maternal blood is increased during first trimester of pregnancy due to succing effect of placenta in comparison to decreased Phe level at the end of labour. Umbilical blood for screening of mHPA is not quite suitable to detect the atypical or mild forms of Phe disturbances which prevailed in our Slavonic population of pregnant women. (Tab. 5, Fig. 7, Ref. 16.)

Spectrum of low density lipoprotein receptor mutations in Czech hypercholesterolemic patients.

The aim of our study was to define mutations causing familial hypercholesterolemia (FH) phenotype in Czech hypercholesterolemic individuals. A combination of heteroduplex analysis, SSCP, DGGE, DNA sequencing and PCR/restriction analysis was used for this purpose. Molecular searching in the promoter region and coding sequence of the low density lipoprotein receptor (LDLR) gene in 130 patients from 68 unrelated families resulted in the identification of 37 sequence variations. Thirty of them are most likely disease causing mutations. Nineteen mutations were novel (two nonsense, five missense, six nucleotide(s) insertions and six nucleotide(s) deletions). Their pathological effect can be predicted on the basis of their position with respect to previously reported mutations with an estimated reduction of the receptor activity and/or premature termination of translation. These results expand our knowledge of mutations responsible for FH. Seven nucleotide variations were characterized as silent polymorphisms. Hum Mutat 18:253, 2001.

Metabolic cause of Reye-like syndrome.

The most frequent metabolic cause of Reye-like syndrome is medium chain acyl-CoA dehydrogenase (MCAD) deficiency. The authors describe a gypsy boy who was repeatedly hospitalised due to symptoms of Reye-like syndrome (serious hypoglycemia, loss of consciousness, seizures, increased values of aminotransferases, decreased values of free carnitine). The diagnosis of MCAD deficiency was established by analysis of plasmatic acylcarnitines by use of tandem mass spectrometry. DNA analysis proved the most common K329E (G985) mutation in gene for MCAD deficiency in homozygous state. The authors have emphasised the advantage of tandem mass spectrometry in the diagnosis of disorders of fatty acid beta-oxidation. This highly sophisticated method can detect most of these disorders from dry blood spots disregarding the symptoms and type of mutation.

Identification of mutations in the glucose-6-phosphatase gene in Czech and Slovak patients with glycogen storage disease type ia, including novel mutations K76N, V166A and 540del5.

Mutations in the glucose-6-phosphatase (G6Pase) gene are responsible for glycogen storage disease type Ia (GSD Ia). A study of the molecular basis of GSD Ia was carried out in 12 Czech and Slovak GSD Ia patients from 10 unrelated families. Mutation analysis was performed for the entire coding region of G6Pase gene using DGGE, sequencing and PCR/digestion. With the strategy used, all mutant alleles were identified in this study. Three novel mutations (K76N, V166A and 540del5), six previously described mutations (W77R, R83C, G188R, R295C, Q347X and 158delC) and one known polymorphism (1176T-->C) were detected. The most common mutation identified was R83C, accounting for 8 out of 20 (40%) mutant alleles. The K76N mutation was found in a Gypsy family: two siblings with GSD Ia were homozygous for this mutation. These findings expand our knowledge of mutations responsible for glycogen storage disease type Ia.

Screening of the most common medium-chain acyl CoA dehydrogenase (MCAD) deficiency mutation (K329E) in the Czech newborn population.

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the commonest inherited disorder of fatty acid oxidation. Most clinically ascertained cases are caused by thc point mutation K329E in MCAD gene. The frequency of this mutation as determined by usc of dried blood spots on Guthrie cards and the PCR NeoI digestion method. Using molecular ncwborn screening we found no K329E homozygote and 14 K329E heterozygotes in 2,826 newborns from Moravian area of the Czech Republic. Lower frequency of K329E carriers (1/202)) suggests that the incidence of MCAD deficiency will be probably lower in our population than we expected.