The MLH1 c.2252_2253delAA mutation was found in 11 unrelated families from a restricted area southwest of Turin among 140 families with mutations in the mismatch repair genes. The mutation is located in the highly conserved C-terminal region, responsible for dimerization with the PMS2 protein. Twenty-five tumour tissues from 61 individuals with the c.2252_2253delAA mutation were tested for microsatellite instability(MSI) and protein expression.We compared the clinical features of these families versus the rest of our cohort and screened for a founder effect. All but one tumours showed the MSI-high mutator phenotype. Normal, focal and lack of MLH1 staining were observed in 16, 36 and 48 % of tumours, respectively. PMS2 expression was always lost. The mutation co-segregated with Lynch syndrome-related cancers in all informative families. All families but one fulfilled Amsterdam criteria, a frequency higher than in other MLH1 mutants. This was even more evident for AC II (72.7 vs. 57.5 %). Moreover, all families had at least one colon cancer diagnosed before 50 years and one case with multiple Lynch syndrome-related tumours. Interestingly, a statistically significant (p = 0.0057) higher frequency of pancreatic tumourswas observed compared to familieswith other MLH1 mutations: 8.2 % of affected individuals versus 1.6 %. Haplotype analysis demonstrated a common ancestral origin of the mutation, which originated about 1,550 years ago. The mutation is currently classified as having an uncertain clinical significance. Clinical features, tissue analysis and co-segregation with disease strongly support the hypothesis that the MLH1 c.2252_2253delAA mutation has a pathogenic effect

A founder MLH1 mutation in Lynch syndrome families from Piedmont, Italy, is associated with an increased risk of pancreatic tumours and diverse immunohistochemical patterns

BORELLI, Iolanda;CASALIS, guido claudio;MICHELETTI, MONICA;MANDRILE, Giorgia;BERCHIALLA, Paola;BRACCO, CECILIA;PASINI, Barbara
2014

Abstract

The MLH1 c.2252_2253delAA mutation was found in 11 unrelated families from a restricted area southwest of Turin among 140 families with mutations in the mismatch repair genes. The mutation is located in the highly conserved C-terminal region, responsible for dimerization with the PMS2 protein. Twenty-five tumour tissues from 61 individuals with the c.2252_2253delAA mutation were tested for microsatellite instability(MSI) and protein expression.We compared the clinical features of these families versus the rest of our cohort and screened for a founder effect. All but one tumours showed the MSI-high mutator phenotype. Normal, focal and lack of MLH1 staining were observed in 16, 36 and 48 % of tumours, respectively. PMS2 expression was always lost. The mutation co-segregated with Lynch syndrome-related cancers in all informative families. All families but one fulfilled Amsterdam criteria, a frequency higher than in other MLH1 mutants. This was even more evident for AC II (72.7 vs. 57.5 %). Moreover, all families had at least one colon cancer diagnosed before 50 years and one case with multiple Lynch syndrome-related tumours. Interestingly, a statistically significant (p = 0.0057) higher frequency of pancreatic tumourswas observed compared to familieswith other MLH1 mutations: 8.2 % of affected individuals versus 1.6 %. Haplotype analysis demonstrated a common ancestral origin of the mutation, which originated about 1,550 years ago. The mutation is currently classified as having an uncertain clinical significance. Clinical features, tissue analysis and co-segregation with disease strongly support the hypothesis that the MLH1 c.2252_2253delAA mutation has a pathogenic effect
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http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10689-014-9726-3
Lynch syndrome; MLH1 mutations; MLH1-PMS2 dimerization; Focal immunohistochemical expression; Founder effect
Iolanda Borelli;Guido C. Casalis Cavalchini;Serena Del Peschio;Monica Micheletti;Tiziana Venesio;Ivana Sarotto;Anna Allavena;Luisa Delsedime;Marco A. Barberis;Giorgia Mandrile;Paola Berchialla;Paola Ogliara;Cecilia Bracco;Barbara Pasini
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/143995
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