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Characterization of genetic changes in oligodendroglial tumors including glioblastomas with oligodendroglial component
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Abstracts / Cancer Genetics and Cytogenetics 203 (2010) 66e99
MUTATION AND HOMOZYGOUS DELETION OF ARHGEF10 IN BLADDER CANCER; A CANDIDATE TUMOUR SUPPRESSOR GENE AT 8p23.3 Sarah V. Williams1, Claire Taylor1, Fiona Platt1, Carolyn D. Hurst1, Jo Aveyard1, Margaret A. Knowles1 1. Leeds Institute of Molecular Medicine, St James’s University Hospital, Beckett Street, Leeds LS9 7TF, United Kingdom
Loss of chromosome arm 8p is found in urothelial carcinoma (UC) and other epithelial cancers and is associated with a more advanced tumour stage. The pattern of complex copy number loss without clear common breakpoints may reflect the need to lose several regions on 8p. We have been examining genomic changes throughout 8p using array CGH on a panel of 33 UC cell lines and 174 bladder tumours, followed by a more detailed investigation of the changes in the cell lines. One of the emerging regions of interest is 8p23.3. This region was involved in breakpoints or specific loss in 6 of the UC tumours. Using duplex PCR we identified and defined a homozygous deletion in one UC cell line. This included the gene ARHGEF10, which is of interest due to its function in regulating RhoA. We performed a mutation screen on ARHGEF10 in 44 UC cell lines, including the original panel of 33. In cell line 639V we found two missense mutations in the same exon, neither of which are known polymorphisms. Further examination using allele specific primers showed that these mutations were in trans, so this could represent biallelic inactivation of the gene. We also showed reduced expression of ARHGEF10 in over half of the UC cell lines. ARHGEF10 is therefore a candidate tumour suppressor gene for UC and other epithelial cancers. It lies in a region frequently lost as part of extensive distal 8p loss, and we have shown specific loss or mutation in some samples, as well as reduced expression.
CHARACTERIZATION OF GENETIC CHANGES IN OLIGODENDROGLIAL TUMORS INCLUDING GLIOBLASTOMAS WITH OLIGODENDROGLIAL COMPONENT Evelin Schrock1, Karl Hackmann1, Dietmar Krex2, Eva-Maria Gerlach1 1. Institut fu¨r Klinische Genetik, TU-Dresden, Germany 2. Klinik und Poliklinik fu¨r Neurochirurgie, TU-Dresden, Germany
In contrast to astrocytic tumors including glioblastomas (GBM), oligodendrogliomas (O) show a better prognosis and increased responsiveness to chemotherapy. Interestingly, a small subgroup of glioblastomas contains areas with histological features of oligodendroglial differentiation. In the current WHO classification (2007) these tumors are now included as a variant of glioblastomas and are called glioblastomas with oligodendroglial component (GBMO). However, definitive diagnostic criteria still do not exist. In this study we used a genome-wide approach (chromosomal comparative genomic hybridization [CGH] and molecular karyotyping) in combination with interphase fluorescence in situ hybridization (FISH) (regions 1p, 1q, 7q, 10q, 17p, 19q, cen18, 21q) to genetically characterize GBMO and “classical” O. We analyzed the oligodendroglial and the astrocytic glioblastoma parts of 13 GBMO separately by chromosomal CGH of microdissected paraffin-embedded tumor tissue and interphase FISH on paraffin sections. Furthermore, freshly frozen material of eight oligodendrogliomas (3 WHO grade II, 5 WHO-grade III) was examined genome-wide by using the standard Agilent 244A chip. We identified four distinct genetic subtypes in GBMO: an “astrocytic” subtype (9/13) characterized by +7/ 10, an “oligodendroglial” subtype with 1p/ 19q (1/13), an “intermediate” subtype showing +7/ 1p (1/13), and an “other” subtype having none of the former aberrations typical for gliomas (2/13). In contrast, most “classical” O (7/8) showed combined 1p/19q deletion, corresponding genetically to the “oligodendroglial” subtype. Five of the O with 1p/19q codeletion showed additional aberrations (e.g., 4, 14, 9, 18). The different histological tumor parts of GBMO revealed common genetic changes in all tumors and showed additional aberrations specific for their oligodendroglial and astrocytic parts. These findings demonstrate the monoclonal origin of the tumor followed by the formation of the astrocytic and oligodendroglial components. We are currently evaluating the array CGH results of the oligodendrogliomas, which will also be presented. The diagnostic determination of these genetic signatures may allow for a better prognostication of the patients. Our results underline the importance of molecular cytogenetic analyses to supplement the histological diagnosis of gliomas.
Abstracts / Cancer Genetics and Cytogenetics 203 (2010) 66e99
MUTATION AND HOMOZYGOUS DELETION OF ARHGEF10 IN BLADDER CANCER; A CANDIDATE TUMOUR SUPPRESSOR GENE AT 8p23.3 Sarah V. Williams1, Claire Taylor1, Fiona Platt1, Carolyn D. Hurst1, Jo Aveyard1, Margaret A. Knowles1 1. Leeds Institute of Molecular Medicine, St James’s University Hospital, Beckett Street, Leeds LS9 7TF, United Kingdom
Loss of chromosome arm 8p is found in urothelial carcinoma (UC) and other epithelial cancers and is associated with a more advanced tumour stage. The pattern of complex copy number loss without clear common breakpoints may reflect the need to lose several regions on 8p. We have been examining genomic changes throughout 8p using array CGH on a panel of 33 UC cell lines and 174 bladder tumours, followed by a more detailed investigation of the changes in the cell lines. One of the emerging regions of interest is 8p23.3. This region was involved in breakpoints or specific loss in 6 of the UC tumours. Using duplex PCR we identified and defined a homozygous deletion in one UC cell line. This included the gene ARHGEF10, which is of interest due to its function in regulating RhoA. We performed a mutation screen on ARHGEF10 in 44 UC cell lines, including the original panel of 33. In cell line 639V we found two missense mutations in the same exon, neither of which are known polymorphisms. Further examination using allele specific primers showed that these mutations were in trans, so this could represent biallelic inactivation of the gene. We also showed reduced expression of ARHGEF10 in over half of the UC cell lines. ARHGEF10 is therefore a candidate tumour suppressor gene for UC and other epithelial cancers. It lies in a region frequently lost as part of extensive distal 8p loss, and we have shown specific loss or mutation in some samples, as well as reduced expression.
CHARACTERIZATION OF GENETIC CHANGES IN OLIGODENDROGLIAL TUMORS INCLUDING GLIOBLASTOMAS WITH OLIGODENDROGLIAL COMPONENT Evelin Schrock1, Karl Hackmann1, Dietmar Krex2, Eva-Maria Gerlach1 1. Institut fu¨r Klinische Genetik, TU-Dresden, Germany 2. Klinik und Poliklinik fu¨r Neurochirurgie, TU-Dresden, Germany
In contrast to astrocytic tumors including glioblastomas (GBM), oligodendrogliomas (O) show a better prognosis and increased responsiveness to chemotherapy. Interestingly, a small subgroup of glioblastomas contains areas with histological features of oligodendroglial differentiation. In the current WHO classification (2007) these tumors are now included as a variant of glioblastomas and are called glioblastomas with oligodendroglial component (GBMO). However, definitive diagnostic criteria still do not exist. In this study we used a genome-wide approach (chromosomal comparative genomic hybridization [CGH] and molecular karyotyping) in combination with interphase fluorescence in situ hybridization (FISH) (regions 1p, 1q, 7q, 10q, 17p, 19q, cen18, 21q) to genetically characterize GBMO and “classical” O. We analyzed the oligodendroglial and the astrocytic glioblastoma parts of 13 GBMO separately by chromosomal CGH of microdissected paraffin-embedded tumor tissue and interphase FISH on paraffin sections. Furthermore, freshly frozen material of eight oligodendrogliomas (3 WHO grade II, 5 WHO-grade III) was examined genome-wide by using the standard Agilent 244A chip. We identified four distinct genetic subtypes in GBMO: an “astrocytic” subtype (9/13) characterized by +7/ 10, an “oligodendroglial” subtype with 1p/ 19q (1/13), an “intermediate” subtype showing +7/ 1p (1/13), and an “other” subtype having none of the former aberrations typical for gliomas (2/13). In contrast, most “classical” O (7/8) showed combined 1p/19q deletion, corresponding genetically to the “oligodendroglial” subtype. Five of the O with 1p/19q codeletion showed additional aberrations (e.g., 4, 14, 9, 18). The different histological tumor parts of GBMO revealed common genetic changes in all tumors and showed additional aberrations specific for their oligodendroglial and astrocytic parts. These findings demonstrate the monoclonal origin of the tumor followed by the formation of the astrocytic and oligodendroglial components. We are currently evaluating the array CGH results of the oligodendrogliomas, which will also be presented. The diagnostic determination of these genetic signatures may allow for a better prognostication of the patients. Our results underline the importance of molecular cytogenetic analyses to supplement the histological diagnosis of gliomas.