Petr Goetz

Clinical findings with implications for genetic testing in families with clustering of colorectal cancer.

BACKGROUND Germ-line mutations in DNA mismatch-repair genes (MSH2, MLH1, PMS1, PMS2, and MSH6) cause susceptibility to hereditary nonpolyposis colorectal cancer. We assessed the prevalence of MSH2 and MLH1 mutations in families suspected of having hereditary nonpolyposis colorectal cancer and evaluated whether clinical findings can predict the outcome of genetic testing. METHODS We used denaturing gradient gel electrophoresis to identify MSH2 and MLH1 mutations in 184 kindreds with familial clustering of colorectal cancer or other cancers associated with hereditary nonpolyposis colorectal cancer. Information on the site of cancer, the age at diagnosis, and the number of affected family members was obtained from all families. RESULTS Mutations of MSH2 or MLH1 were found in 47 of the 184 kindreds (26 percent). Clinical factors associated with these mutations were early age at diagnosis of colorectal cancer, the occurrence in the kindred of endometrial cancer or tumors of the small intestine, a higher number of family members with colorectal or endometrial cancer, the presence of multiple colorectal cancers or both colorectal and endometrial cancers in a single family member, and fulfillment of the Amsterdam criteria for the diagnosis of hereditary nonpolyposis colorectal cancer (at least three family members in two or more successive generations must have colorectal cancer, one of whom is a first-degree relative of the other two; cancer must be diagnosed before the age of 50 in at least one family member; and familial adenomatous polyposis must be ruled out). Multivariate analysis showed that a younger age at diagnosis of colorectal cancer, fulfillment of the Amsterdam criteria, and the presence of endometrial cancer in the kindred were independent predictors of germ-line mutations of MSH2 or MLH1. These results were used to devise a logistic model for estimating the likelihood of a mutation in MSH2 and MLH1. CONCLUSIONS Assessment of clinical findings can improve the rate of detection of mutations of DNA mismatch-repair genes in families suspected of having hereditary nonpolyposis colorectal cancer.

DiGeorge/velocardiofacial syndrome: FISH studies of chromosomes 22q11 and 10p14, and clinical reports on the proximal 22q11 deletion

DiGeorge anomaly/velocardiofacial syndrome (DG/VCFS) occurs with different deletion intervals on chromosomes 22q11, while the DiGeorge anomaly (with other findings) is seen in patients with deletions of 10p14. The clinical outcome with the common 22q11 deletion (90% of cases) is well known, but the outcome with the less frequent deletion types has not been well documented. Using cytogenetic and fluorescence in situ hybridization (FISH) analysis we studied a series of 295 patients with suspected DG/VCFS. We identified 58 subjects with a 22q11 deletion, and none with a 10p deletion. Fifty‐two subjects had the common deletion, five had the proximal deletion, and one had an atypical proximal deletion due to a 1;22 translocation. We report clinical data of four subjects with the proximal 22q11 microdeletion, and of one patient with the atypical proximal deletion. The anomalies observed with the proximal 22q11 microdeletion fell within the DG/VCFS spectrum. Two females, 6 and 25 years old, had normal mental development. Normal development has been reported with the common 22q11 deletion, but only in a minority of cases. This study may indicate a better intellectual and/or behavioral outcome with the proximal vs. the common 22q11 deletion, rather than a chance finding.

Is there anticipation in the age at onset of cancer in families with Li-Fraumeni syndrome?

AbstractAnticipation in the age at onset of cancer in successive generations was described in several familial cancer syndromes. Based on multiple statistical analyses of a database of families with germline TP53 mutations, and using several different approaches and measures to eliminate possible biases, we show that anticipation may be a feature of the Li-Fraumeni syndrome. Definitive proof of anticipation in pedigrees with germline TP53 mutations will require more family data and further analysis, as well as research on the role of the p53 protein in processes like genome stability, which may represent the biological basis of anticipation in these families. This should have important practical implications for genetic testing, counselling, and preventative care for individuals at risk.

Fluorescent Multiplex PCR: Fast Method for Autosomal Dominant Spinocerebellar Ataxias Screening

Expansion of CAG trinucleotide repeats has been shown to cause a number of autosomal dominant spinocerebellar ataxias such as SCA1, SCA2, SCA3/MJD, SCA6, and SCA7. These disorders are characterized by a wide inter- and intrafamiliar variation in clinical features. The same mutation can result in different phenotypes and the very similar phenotypes can be caused by different mutations. Therefore it is necessary to investigate more SCA genes (according to prevalence) to identify the causal elongation. We developed a fast and efficient screening method based on touchdown multiplex PCR with fluorescent labelled primers for the most common types of SCAs (SCA 1, 2, 3, and 7). It has been reliable in 113 probands tested. Fragment analysis was performed by using 6% denaturing polyacrylamide gel and employing the automated DNA sequencer. This method considerably shortens the process of molecular genetic screening of SCAs and might be used as a tip for designing other SCA screening sets.

Large de novo expansion of CAG repeats in patient with sporadic spinocerebellar ataxia type 7

Sirs: Spinocerebellar ataxia type 7 (SCA7) is a rare neurodegenerative disorder caused by CAG repeat expansion within the 5’-translated region. Ataxia is usually combined with pigmentary macular degeneration [1, 3]. The locus for SCA7 has been mapped to chromosome 3p14-p21.1 [1]. Expanded alleles in SCA7 patients range from 37 to > 200 repeats, whereas in normal alleles the number of trinucleotides varies from 4 to 35 [4, 7]. The repeat sequence in SCA7 gene is extremely unstable, therefore the age of onset may be shifted in descendent generations as many as decades. SCA7 repeat is liable to expand in particular when transmitted by males [2, 5]. We report an unusual case of sporadic SCA7 with de novo CAG expansion. Initially the patient was misdiagnosed as having Friedreich’s ataxia (FRDA) due to sporadic occurrence in the family and early age of onset. DNA analysis of FRDA was performed first to confirm the clinical diagnosis but the proband showed to be a heterozygous with both alleles in normal range (15/21 GAA). Later we have analysed SCA7 CAG repeat number in the patient and 4 relatives. DNA analysis was performed using a modified PCR method [6] (primers 7ALT/4 U716) either with direct incorporation of α32P dCTP, or by PCR fragment analysis using ABI PRISM 377 Automated Sequencer (Perkin Elmer). To resolve the multiple bands in the expanded allele, we diluted the DNA samples to about 10 genome copies of DNA/ PCR reaction (Fig. 1). We found a large de novo expansion in the proband, where the 51 CAG allele expanded from a normal range 10 CAG (Fig. 2). PCR fragments were gel-purified, subcloned into pGEMT Easy Vector (Promega), and the number of CAG in each allele was confirmed by sequencing using BigDyeTM Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems). For the paternity testing, we genotyped also multiallelic microsatellite markers using LETTER TO THE EDITORS

The Bleeding Risk during Warfarin Therapy Is Associated with the Number of Variant Alleles of CYP2C9 and VKORC1 Genes

Background: Warfarin is commonly used for the treatment and prevention of arterial and venous thromboembolism but its use is hindered by the risk of bleeding. The main reason for this risk is a narrow therapeutic index and a wide response variability after warfarin treatment. These shortcomings affect clinical outcomes including bleeding complications and may be associated with variant polymorphisms in the CYP2C9 and VKORC1 genes. Aim: It was the aim of this study to assess the impact of the total variant allele count of CYP2C9 and VKORC1 genes on bleeding related to warfarin treatment. Methods: In a retrospective cohort-design study, patients were genotyped for polymorphisms in genes CYP2C9 (*1, *2, *3) and VKORC1 (haplotype A, B). Extensive clinical data were obtained. Adjusted hazard ratios (HR) for the occurrence of major bleeding events (MBE) were counted separately for the induction and maintenance phases of warfarin therapy. Results: Out of the 329 patients in our clinical database, 194 patients were eligible and included in the analysis. MBE occurred in 51 patients (26.3%) during a mean follow-up of 26 months: 6 patients (11.8%) experienced early MBE during warfarin initiation, and 45 MBE occurred during the maintenance phase. The adjusted HR for MBE risk for patients with any CYP2C9 variant allele was 1.962 [95% confidence interval (CI) 1.08-3.56, p = 0.027]; for the VKORC1 AA haplotype, HR was 1.841 (95% CI 0.97-3.48, p = 0.06), while for 3 variant allele carriers of both genes, HR was 4.34 (95% CI 1.95-9.65, p < 0.001). Despite the insignificant association of the VKORC1 genotype with bleeding in our study, we have noted a warfarin dose-dependent effect with risk significance ascending: CYP2C9 *1/*1 + VKORC1 B/B < CYP2C9 *1/*1 + VKORC1 A/B < CYP2C9 *1/*2 + VKORC1 B/B. Conclusion: Patients who are carriers of 3 variant alleles of the genes CYP2C9 and VKORC1 exhibited a significantly higher risk of MBE during the initiation and maintenance phases of warfarin therapy. Vigilant and careful management of patients with a higher variant allele count, including switching to newer anticoagulants, could be considered in this high-risk cohort.

Absence of spinocerebellar ataxia type 3/Machado-Joseph disease within ataxic patients in the Czech population

Although spinocerebellar ataxia type 3 (SCA3)/Machado–Joseph disease is the most common type of SCA worldwide, we did not identify any cases of the disease amongst SCA patients in the Czech population. It has been proposed that the prevalence of large normal alleles correlates with the frequency of various types of SCA. We have therefore attempted to resolve the absence of SCA3 in our population by investigating, within 204 normal chromosomes, the frequency and nature of CAG repeats as well as two intragenic polymorphisms. We found that large normal alleles with more than 33 CAG repeats were observed at a frequency of only 0.49%. Whereas most of the expanded alleles worldwide have the CA haplotype, this was the least common (5.4%) variant observed in our study, although it was associated with a larger mean CAG repeat length (26.9). We postulate that the absence of SCA3 in the Czech population might be explained by the lack of large normal alleles and consequently a relatively small reservoir for aberrant CAG expansions at the SCA3 locus.

Discussion on the use of taxanes for treatment of breast cancers in BRCA1 mutations carriers

BRCA1-associated cancers differ from non-hereditary cancers for many factors, including somatic mutation. It can be a subject of discussion that the natural history and response to treatment also may differ between the hereditary and sporadic subgroups. Three frequent BRCA1 mutations (5382insC, 4153delA, C61G) in the Baltic countries (Lithuania, Latvia, Byelorussia and Poland) open a way for the chip test to select a subgroup from women with breast cancer. These women with BRCA1 breast cancer have a chance to get adequate treatment, including neo-adjuvant chemotherapy. So far many retrospective studies of survival, that used the same gold standard treatment for women with BRCA1 breast cancer and for women without a mutation, have not found a difference between these groups. Some studies show a worse survival result in women with a BRCA1 mutation than women without the mutation.