TY  - JOUR
A1  - Hansmann, Tamara
A1  - Pliushch, Galyna
A1  - Leubner, Monika
A1  - Kroll, Patricia
A1  - Endt, Daniela
A1  - Gehrig, Andrea
A1  - Preisler-Adams, Sabine
A1  - Wieacker, Peter
A1  - Haaf, Thomas
T1  - Constitutive promoter methylation of BRCA1 and RAD51C in patients with familial ovarian cancer and early-onset sporadic breast cancer
JF  - Human Molecular Genetics
N2  - Genetic defects in breast cancer (BC) susceptibility genes, most importantly BRCA1 and BRCA2, account for ∼40% of hereditary BC and ovarian cancer (OC). Little is known about the contribution of constitutive (soma-wide) epimutations to the remaining cases. We developed bisulfite pyrosequencing assays to screen >600 affected BRCA1/BRCA2 mutation-negative patients from the German Consortium for Hereditary Breast and Ovarian Cancer for constitutive hypermethylation of ATM, BRCA1, BRCA2, RAD51C, PTEN and TP53 in blood cells. In a second step, patients with ≥6% promoter methylation were analyzed by bisulfite plasmid sequencing to demonstrate the presence of hypermethylated alleles (epimutations), indicative of epigenetic gene silencing. Altogether we identified nine (1.4%) patients with constitutive BRCA1 and three (0.5%) with RAD51C hypermethylation. Epimutations were found in both sporadic cases, in particular in 2 (5.5%) of 37 patients with early-onset BC, and familial cases, in particular 4 (10%) of 39 patients with OC. Hypermethylation was always confined to one of the two parental alleles in a subset (12–40%) of the analyzed cells. Because epimutations occurred in cell types from different embryonal layers, they most likely originated in single cells during early somatic development. We propose that analogous to germline genetic mutations constitutive epimutations may serve as the first hit of tumor development. Because the role of constitutive epimutations in cancer development is likely to be largely underestimated, future strategies for effective testing of susceptibility to BC and OC should include an epimutation screen.
KW  - promoter methylation
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125673
VL  - 21
IS  - 21
ER  - 
TY  - JOUR
A1  - Galetzka, Danuta
A1  - Hansmann, Tamara
A1  - El Hajj, Nady
A1  - Weis, Eva
A1  - Irmscher, Benjamin
A1  - Ludwig, Marco
A1  - Schneider-Rätzke, Brigitte
A1  - Kohlschmidt, Nicolai
A1  - Beyer, Vera
A1  - Bartsch, Oliver
A1  - Zechner, Ulrich
A1  - Spix, Claudia
A1  - Haaf, Thomas
T1  - Monozygotic twins discordant for constitutive BRCA1 promoter methylation, childhood cancer and secondary cancer
JF  - Epigenetics
N2  - We describe monozygotic twins discordant for childhood leukemia and secondary thyroid carcinoma. We used bisulfite pyrosequencing to compare the constitutive promoter methylation of BRCA1 and several other tumor suppressor genes in primary fibroblasts. The affected twin displayed an increased BRCA1 methylation (12%), compared with her sister (3%). Subsequent bisulfite plasmid sequencing demonstrated that 13% (6 of 47) BRCA1 alleles were fully methylated in the affected twin, whereas her sister displayed only single CpG errors without functional implications. This between-twin methylation difference was also found in irradiated fibroblasts and untreated saliva cells. The BRCA1 epimutation may have originated by an early somatic event in the affected twin: approximately 25% of her body cells derived from different embryonic cell lineages carry one epigenetically inactivated BRCA1 allele. This epimutation was associated with reduced basal protein levels and a higher induction of BRCA1 after DNA damage. In addition, we performed a genome-wide microarray analysis of both sisters and found several copy number variations, i.e., heterozygous deletion and reduced expression of the RSPO3 gene in the affected twin. This monozygotic twin pair represents an impressive example of epigenetic somatic mosaicism, suggesting a role for constitutive epimutations, maybe along with de novo genetic alterations in recurrent tumor development.
KW  - BRCA1
KW  - childhood cancer
KW  - DNA Methylation
KW  - epimutation
KW  - monozygotic twins
KW  - secondary cancer
KW  - somatic mosaicism
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125386
VL  - 7
IS  - 1
ER  -