2008 Barcelona - European Society of Human Genetics

Cancer genetics
P04.021
comparative scanning of polymorphisms in mitochondrial Dloop
region in colorectal and breast cancer
M. Akouchekian1,2 , M. Houshmand2,3 ;
1 2 Hanover university, Hanover, Germany, Department of Medical Genetics,
National Institute for Genetic Engineering and Biotechnology (NIGEB), Tehran,
Islamic Republic of Iran, 3Department of Genetic, Special Medical Center, Tehran,
Islamic Republic of Iran.
ABstRAct
Mitochondrial DNA (mtDNA) mutations have been found in many kinds
of human cancer and especially the 1 .1 kb displacement loop (D-loop)
region was found to be a “hot spot” for mutation in mtDNA of tumors .
Mitochondria play an important role in shifting the cell from death to abnormal
cell growth thus contributing to the neoplastic process, because
of their essential roles in energy metabolism and generation of reactive
oxygen species (ROS) also initiation of apoptosis and aging . The purpose
of this study is to scan the mutation frequencies in hypervariable
regions of mitochondrial D-Loop in colorectal and breast cancer patients
comparatively . The results of our investigation are summarized
in the following table . when each polymorphism is tested individually
using the fisher exact test the frequency of two single-nucleotide polymorphism
SNPs were found to be significantly different between the
colorectal cancer (CRC) and breast cancer patient (p≤0.05).while the
SNP C16261T (p=0.0005) is significantly more in breast cancer patients
than CRC patients, the frequency of SNP T16519C (p=0 .0019)
is less in breast cancer patients than CRC patients .
In this contribution the fact that SNP C16261T may be a consequence
for breast cancer and SNP T16519C for CRC is discussed .
Colorectal cancer
Fisher’’s Exact Test Breast cancer cases (n=6)
Cases (n=40)
p value
% Positive % Positive
0 .0005 83 .3 5 10 4
1 16 .6 1 25 10
1 0 0 10 4
0 .0019 0 0 70 28
P04.022
Identification of two MLH founder mutations in spanish
Hereditary Nonpolyposis colorectal cancer families
E. Borràs 1 , M. Pineda 1 , I. Blanco 2 , G. Llort 3 , T. Caldés 4 , M. Urioste 5 , C.
Martínez-Bouzas 6 , B. Graña 7 , A. Torres 8 , T. Ramón y Cajal 9 , J. Sanz 10,8 , S.
González 1 , C. Lázaro 1 , G. Capellá 1 ;
1 Laboratori de Recerca Translacional, Institut Català d’Oncologia, IDIBELL,
Hospitalet de Llobregat, Spain, 2 Unitat de Consell Genètic, Institut Català
d’Oncologia, IDIBELL, Hospital Duran i Reynals, Hospitalet de Llobregat,
Spain, 3 Unitat de Consell Genètic, Institut Català d’Oncologia, Hospital Germans
Trias i Pujol, Badalona, Spain, 4 Laboratorio de Oncología Molecular, Hospital
Clínico Sant Carlos, Madrid, Spain, 5 Departamento de Genética Humana,
Centro Nacional de Investigaciones Oncologicas, Madrid, Spain, 6 Laboratorio
de Genética Molecular, Hospital de Cruces, Bizkaia, Spain, 7 Unitat d’Avaluació
del Risc de Càncer i Consell Genètic, Institut Català d’Oncologia, Hospital
Universitari Josep Trueta, Girona, Spain, 8 Unitat de Consell Genètic, Hospital
Universitari Sant Joan, Reus, Spain, 9 Servei d’Oncologia Mèdica, Hospital de la
Santa Creu i Sant Pau, Barcelona, Spain, 10 Institut d’Oncologia Corachan-Centre
Mèdic, Barcelona, Spain.
Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal
disorder caused by mutations in DNA mismatch repair genes, most
often in MLH1, MSH2 and MSH6 genes . Tumors of HNPCC-spectrum
are associated with microsatellite instability and loss of mismatch repair
proteins expression . In some populations, founder mutations appear
to explain a substantial fraction of HNPCC cases .
We report here the identification of two mutations in MLH1 gene,
c .306+5G>A and c .1865T>A (p .Leu622His), in 12 and 11 Spanish
HNPCC families, respectively . Both mutations segregate with the disease,
and tumors show microsatellite instability and loss of expression
of MLH1 protein . RNA studies demonstrate that c .306+5G>A mutation
generates two aberrant mRNA transcripts . Experimental approaches
are being performed to elucidate the pathogenicity of the c .1865T>A
(p .Leu622His) mutation .
Haplotype analysis is performed using three single nucleotide polymorphisms
of MLH1 gene, three intragenic and four extragenic microsatellite
markers, located between D3S1609 and D3S3564 . We identify
two common haplotypes associated to c .306+5G>A and c .1865T>A,
suggesting a founder effect .
Mutations c .306+5G>A and c .1865T>A (p .Leu622His) of MLH1 gene
are the first founder MLH1 mutations identified in Spain. This fact
would have important implications for the design of molecular diagnostic
strategies in the HNPCC Spanish families .
P04.023
Further evidence for heritability of an epimutation in one of
twelve cases with mLH1 promoter methylation in blood cells
clinically displaying HNPcc
M. Morak 1,2 , H. Schackert 3 , N. Rahner 4 , B. Betz 5 , C. Walldorf 4 , B. Royer-Pokora
5 , K. Schulmann 6 , W. Dietmaier 7 , G. Keller 8 , T. Massdorf 1 , A. Laner 2 , G.
Leitner 2 , E. Holinski-Feder 2,1 ;
1 University Hospital of the Ludwig-Maximilians-University, Munich, Germany,
2 Center of Medical Genetics, Munich, Germany, 3 Department of Surgical Research,
University of Dresden, Dresden, Germany, 4 Institute of Human Genetics,
University of Bonn, Bonn, Germany, 5 Institute of Human Genetics, Heinrich-Heine
University Düsseldorf, Düsseldorf, Germany, 6 Medical Department,
Ruhr-University Bochum, Bochum, Germany, 7 Institute of Pathology, University
of Regensburg, Regensburg, Germany, 8 Institute of Pathology, Technical University,
Munich, Germany.
ABSTRACT
Germline mutations in mismatch repair (MMR) genes, tumours with
high microsatellite instability (MSI-H) and loss of MMR protein expression
are the hallmarks of HNPCC (Lynch-syndrome) . While somatic
MLH1 promoter hypermethylation is generally accepted in the tumorigenesis
of sporadic tumours, abnormal MLH1 promoter methylation in
normal body cells is controversially discussed as a mechanism predisposing
patients to HNPCC .
94 patients suspected of HNPCC-syndrome with a mean age of onset
of 45 .5 years, MLH1-deficiency in their tumours but no germline mutation
underwent methylation-specific PCR-screening for MLH1 promoter
methylation .
In peripheral blood cells of twelve patients an MLH1 promoter methylation,
in seven informative cases allele-specific, was found. Normal
colonic tissue, buccal mucosa, and tumour tissue available from three
patients also presented abnormal hemiallelic methylation in the MLH1
promoter . The heredity of aberrant methylation is questionable . Pro:
MLH1 promoter methylation was found in a patient and his mother giving
evidence for a familial predisposition for an epimutation in MLH1 .
Contra: a de novo set-up of methylation in one patient, a mosaic or
incomplete methylation pattern in six patients, and no evidence for inheritance
of MLH1 promoter methylation in the remaining families .
Our findings provide strong evidence that MLH1 promoter methylation
in normal body cells mimics HNPCC and constitutes a pathogenic prelesion
in MLH1. The identification of hypermethylation as an epigenetic
defect has important implications for surveillance recommendations,
as these patients should be treated like Lynch-Syndrome patients,
whereas the heritability of methylation is still under investigation .
P04.024
Founder effect of a pathogenic MSH mutation identified in four
Hereditary Non-Polyposis colorectal cancer (HNPcc) families
M. Menéndez 1 , S. Castellví-Bel 2 , M. Pineda 1 , R. de Cid 3 , J. Muñoz 2 , F.
Balaguer 2 , V. Gonzalo 2 , M. Giráldez 2 , I. Blanco 4 , G. Llort 5 , T. Ramón y Cajal 6 , S.
González 1 , A. Castells 2 , G. Capellá 1 ;
1 Laboratori de Recerca Translacional, Institut Català d’Oncologia, IDIBELL,
Hospitalet de Llobregat, Spain, 2 Servei de Gastroenterologia, Institut de Malalties
Digestives i Metabòliques, Hospital Clínic, CIBEREHD, IDIBAPS, Barcelona,
Spain, 3 Programa Gens i Malaltia, Centre de Regulació Genòmica-UPF,
Barcelona, Spain, 4 Unitat de Consell Genètic, Institut Català d’Oncologia,
IDIBELL, Hospital Duran i Reynals, Hospitalet de Llobregat, Spain, 5 Unitat de
Consell Genètic, Institut Català d’Oncologia, Hospital Universitari Germans
Trias i Pujol, Badalona, Spain, 6 Servei d’Oncologia Mèdica, Hospital de la
Santa Creu i Sant Pau, Barcelona, Spain.
HNPCC is caused by germline mutations in DNA mismatch repair genes
MLH1, MSH2, MSH6 and PMS2 . The novel MSH2 c .[2635-3T>C;
2635-5C>T] mutation was identified in 4 HNPCC families, cosegregating
with the disease . This mutation, located in intron 15, was predicted
to alter the correct mRNA processing by in silico analysis .
Our aim was to perform the c .[2635-3T>C; 2635-5C>T] mutation
screening in HNPCC and control populations, to evaluate the founder
effect in our population by haplotype analysis and to confirm the pathogenic
effect of the mutation by MSH2 expression studies .