Rasopathies - dysmorphic syndromes with short stature and risk of malignancy

OBJECTIVES

The term ´Rasopathies´ represents a group of five neurodevelopmental syndromes (Noonan, LEOPARD, Costello, Cardio-facio-cutaneous, and Neurofibromatose-Noonan syndrome) caused by germline mutation in genes encoding proteins involved in RAS/MAPK (rat sarcoma/mitogen-activated protein kinase) signaling pathway. The RAS/MAPK signaling pathway participates in regulation of cell determination, proliferation, differentiation, migration, and senescence and dysregulation of this pathway can lead to the risk of tumorigenesis. In this review, we aim to summarize the current clinical and molecular genetic knowledge on Rasopathies with special attention for the risk of cancer. We propose also clinical and therapeutic approach for patients with malignancy.

METHODS

We are reviewing the clinical and molecular basis of Rasopathies based on recent studies, clinical examination, and molecular diagnostics (mutation analysis of causal genes for Rasopathies) in Slovak pediatric patients.

RESULTS

Some clinical features, such as short stature, a specific facial dysmorphology and cardiac abnormalities are common to all of Rasopathy syndromes. However, there are unique signs by which the syndromes can differ from each other, especially multiple lentigo in LEOPARD syndrome, increased risk of malignancy in Costello syndrome, dry hyperkeratotic skin in patients with cardio-facio-cutaneous syndrome, and neurofibromas and cafe-au-lait spots in neurofibromatosis-Noonan syndrome.

CONCLUSION

Despite the overlapping clinical features, Rasopathy syndromes exhibit unique fenotypical features and the precise molecular diagnostics may lead to confirmation of each syndrome. The molecular diagnostics may allow the detection of pathogenic mutation associated with tumorigenesis.

Guidelines for surveillance of individuals with constitutional mismatch repair-deficiency proposed by the European Consortium "Care for CMMR-D" (C4CMMR-D)

Lynch syndrome (LS) is an autosomal dominant disorder caused by a defect in one of the DNA mismatch repair genes: MLH1, MSH2, MSH6 and PMS2. In the last 15 years, an increasing number of patients have been described with biallelic mismatch repair gene mutations causing a syndrome referred to as 'constitutional mismatch repair-deficiency' (CMMR-D). The spectrum of cancers observed in this syndrome differs from that found in LS, as about half develop brain tumours, around half develop digestive tract cancers and a third develop haematological malignancies. Brain tumours and haematological malignancies are mainly diagnosed in the first decade of life, and colorectal cancer (CRC) and small bowel cancer in the second and third decades of life. Surveillance for CRC in patients with LS is very effective. Therefore, an important question is whether surveillance for the most common CMMR-D-associated cancers will also be effective. Recently, a new European consortium was established with the aim of improving care for patients with CMMR-D. At a workshop of this group held in Paris in June 2013, one of the issues addressed was the development of surveillance guidelines. In 1968, criteria were proposed by WHO that should be met prior to the implementation of screening programmes. These criteria were used to assess surveillance in CMMR-D. The evaluation showed that surveillance for CRC is the only part of the programme that largely complies with the WHO criteria. The values of all other suggested screening protocols are unknown. In particular, it is questionable whether surveillance for haematological malignancies improves the already favourable outcome for patients with these tumours. Based on the available knowledge and the discussions at the workshop, the European consortium proposed a surveillance protocol. Prospective collection of all results of the surveillance is needed to evaluate the effectiveness of the programme.

Clustering of mutations in the 5' tertile of the NF1 gene in Slovakia patients with optic pathway glioma

Optic pathway gliomas (OPG) occur in 15% of patients with neurofibromatosis type 1 (NF1; OMIM 162200). Genotype-phenotype correlations in patients with NF1 may help to determine the risk group for developing complications such as OPG in coincidence with other NF1.features. We evaluated 52 patients with NF1 (25 with OPG and 27 without OPG). All subjects underwent a clinical examination focused on neurofibromatosis type 1 and molecular diagnostics of NF1 gene using protocol based on RNA analysis confirming the diagnosis of NF1. In the group with OPG patients, there was a significantly higher incidence of freckling (P=0.017), neurofibromatosis bright objects (NBO) (P=0.0038), compared to the group without OPG. The differences between the groups with respect to Lisch nodules were on the borderline of statistical significance (P=0.088). The frequency of neurofibromas in the group with OPG was not significant (P=0.9). From all patients with the mutation localized in the first tertile of the NF1 gene majority (71%) had optic glioma compared to individuals who didn't have the OPG 29% (P=0.0049). Our results present the clustering of mutations in the 5'tertile of NF1 gene in patients with optic nerve glioma and suggest higher incidence of freckling and neurofibromatosis brain objects in these patients. Molecular analysis of NF1 gene is important part in complex management of NF1 patients and contributes to a better understanding of clinical picture of NF1 patients. .

Late onset of familial neurogenic diabetes insipidus in monozygotic twins

OBJECTIVE

Autosomal dominant familial diabetes insipidus (FNDI) is a rare disease characterized by polydipsia and polyuria due to deficiency of the antidiuretic hormone, arginine vasopressin (AVP). We report the first Slovak family with the disease. Noteworthy is the concordantly belated debut of the disease symptoms in two monozygotic twin proband girls in the age of 17 years. Because of inconclusive results of water deprivation test consistent with partial diabetes insipidus (DI), missing "bright spot" of posterior pituitary gland in T1-weighted magnetic resonance imaging and family occurrence of polyuria and polydipsia on anamnestic evaluation.

METHODS

Molecular genetic testing of the AVP gene was proceeded, because of the inconclusive results of water deprivation test consistent with partial diabetes insipidus, missing "bright spot" of posterior pituitary gland in T1-weighted magnetic resonance imaging and family occurrence of polyuria and polydipsia on anamnestic evaluation.

RESULTS

Genetic analysis revealed a heterozygous g.279G>A substitution that predicts a p.Ala19Thr substitution in the signal peptide of the AVP prohormone. The wide intrafamiliar variations (3 to 17 years) in disease onset together with the concordantly delayed debut of polyuria in two monozygotic twin girls suggest that individual differences in genetic influences family environmental factors may modify the penetrance of the mutation of the AVP gene.

CONCLUSIONS

The present paper supports the notion that molecular genetic evaluation should be performed in all patients with familial occurrence of DI regardless of the clinical results.

Targeted prostate cancer screening in men with mutations in BRCA1 and BRCA2 detects aggressive prostate cancer: preliminary analysis of the results of the IMPACT study

OBJECTIVE

To evaluate the role of targeted prostate cancer screening in men with BRCA1 or BRCA2 mutations, an international study, IMPACT (Identification of Men with a genetic predisposition to ProstAte Cancer: Targeted screening in BRCA1/2 mutation carriers and controls), was established. This is the first multicentre screening study targeted at men with a known genetic predisposition to prostate cancer. A preliminary analysis of the data is reported.

PATIENTS AND METHODS

Men aged 40-69 years from families with BRCA1 or BRCA2 mutations were offered annual prostate specific antigen (PSA) testing, and those with PSA > 3 ng/mL, were offered a prostate biopsy. Controls were men age-matched (± 5 years) who were negative for the familial mutation.

RESULTS

In total, 300 men were recruited (205 mutation carriers; 89 BRCA1, 116 BRCA2 and 95 controls) over 33 months. At the baseline screen (year 1), 7.0% (21/300) underwent a prostate biopsy. Prostate cancer was diagnosed in ten individuals, a prevalence of 3.3%. The positive predictive value of PSA screening in this cohort was 47·6% (10/21). One prostate cancer was diagnosed at year 2. Of the 11 prostate cancers diagnosed, nine were in mutation carriers, two in controls, and eight were clinically significant.

CONCLUSIONS

The present study shows that the positive predictive value of PSA screening in BRCA mutation carriers is high and that screening detects clinically significant prostate cancer. These results support the rationale for continued screening in such men.

New insights to the MLL recombinome of acute leukemias

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

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.