Abstracts 105 INTERPHASE CYTOGENETICS IN THE ANALYSIS OF CHROMOSOME ABERRATIONS IN PARAFFIN SECTIONS OF SOLID TUMORS M. Vallinga, F.C.S. Ramaekers Dept. of Molecular Cell Biology & Genetics, Univ. of Limburg, P.O.Box 616, 6200 MD, Maastricht. The Netherlands In situ hybridization (ISH) using repetitive probes can be performed in routinely processed, paraffin-embedded tissue sections from solid tumors. This enable us to study chromosomal aberrations in archival pathological material. An important parameter to obtain strong ISH signals and reproducible results in sections appeared to be the proteolytic treatment of the sections prior the ISH reaction. Different parameters were studied involving influence of nuclear truncation in the detection of numerical chromosome aberrations, the detection of tumor cells among stromal and inflammatory cells, flow cytometric DNA index in relation to chromosome copy number, and chromosome heterogeneity. Paraffin sections of several routinely processed tumors were studied. In bladder cancer we compared the detection of trisomy up to nullisomy in cells isolated from tumors with the results obtained in paraffin sections. In mesotheliomas we compared the results of classical karyotyping with the detection of aberrations in the paraffin section. In hydatiform moles and hydropic abortions we compared sex chromosome patterns, chromosome aneuploidy and chromosome composition in different subpopulations. In case of a melanoma we compared human melanoma cell lines with tissue sections of xenografted lesions obtained from these cell lines in nude mice. The results of these studies in different types of cancer will be discussed. METAPHASE CHROMOSOME STRUCTURE: AN IN SITU HYBRIDIZATION APPROACH AT INFRAGENIC LEVEL N. Lemieux*# B. Malfoy*, R. Fetni#, M. Muleris*, N. Vogt*, C.L. Richer ° and ~=_.[~Lt.dJ.~l~* *URA 620 CNRS, Institut Curie, Section de Biologie, Structure et Mutagen~se Chromosomiques, 26 rue d'UIm, 75231 Paris C~dex 05, France. #D(~partements de Pathologie et °d'Anatomie, Facult~ de M~decine, Universit6 de Montreal, C.P. 6128, Succ. A, Montr(~al, Quebec, H3C 3J7, Canada. New methods of in situ hybridization were developed for fluorescence (FISH) and electron microscopy (EMISH). A very high resolution could be obtained, allowing us to discriminate small non repetitive DNA sequences at infragenic level. This was applied to the retinoblastoma gene, for which several probes distributed along the 200 kb gene were hybridized. DNA sequences 30-40 kb apart could be precisely positioned in the same order as expected by the molecular mapping. These observations suggests that the chromosome structure is fairly well preserved after hybridization and that the target DNA is located on a semi-rigid structure which would correspond to loops not completely embedded in a rigid network. They bring out experimental data to support present models on chromosomal organization.

Interphase cytogenetics in the analysis of chromosome aberrations in paraffin sections of solid tumors

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Abstracts 105

INTERPHASE CYTOGENETICS IN THE ANALYSIS OF CHROMOSOME ABERRATIONS IN PARAFFIN SECTIONS OF SOLID TUMORS

M. Vallinga, F.C.S. Ramaekers Dept. of Molecular Cell Biology & Genetics, Univ. of Limburg, P.O.Box 616, 6200 MD, Maastricht. The Netherlands

In situ hybridization (ISH) using repetitive probes can be performed in routinely processed, paraffin-embedded tissue sections from solid tumors. This enable us to study chromosomal aberrations in archival pathological material. An important parameter to obtain strong ISH signals and reproducible results in sections appeared to be the proteolytic treatment of the sections prior the ISH reaction. Different parameters were studied involving influence of nuclear truncation in the detection of numerical chromosome aberrations, the detection of tumor cells among stromal and inflammatory cells, flow cytometric DNA index in relation to chromosome copy number, and chromosome heterogeneity. Paraffin sections of several routinely processed tumors were studied. In bladder cancer we compared the detection of trisomy up to nullisomy in cells isolated from tumors with the results obtained in paraffin sections. In mesotheliomas we compared the results of classical karyotyping with the detection of aberrations in the paraffin section. In hydatiform moles and hydropic abortions we compared sex chromosome patterns, chromosome aneuploidy and chromosome composition in different subpopulations. In case of a melanoma we compared human melanoma cell lines with tissue sections of xenografted lesions obtained from these cell lines in nude mice. The results of these studies in different types of cancer will be discussed.

METAPHASE CHROMOSOME STRUCTURE: AN IN SITU HYBRIDIZATION APPROACH AT INFRAGENIC LEVEL N. Lemieux*# B. Malfoy*, R. Fetni#, M. Muleris*, N. Vogt*, C.L. Richer ° and ~=_.[~Lt.dJ.~l~* *URA 620 CNRS, Institut Curie, Section de Biologie, Structure et Mutagen~se Chromosomiques, 26 rue d'UIm, 75231 Paris C~dex 05, France. #D(~partements de Pathologie et °d'Anatomie, Facult~ de M~decine, Universit6 de Montreal, C.P. 6128, Succ. A, Montr(~al, Quebec, H3C 3J7, Canada.

New methods of in situ hybridization were developed for fluorescence (FISH) and electron microscopy (EMISH). A very high resolution could be obtained, allowing us to discriminate small non repetitive DNA sequences at infragenic level. This was applied to the retinoblastoma gene, for which several probes distributed along the 200 kb gene were hybridized. DNA sequences 30-40 kb apart could be precisely positioned in the same order as expected by the molecular mapping. These observations suggests that the chromosome structure is fairly well preserved after hybridization and that the target DNA is located on a semi-rigid structure which would correspond to loops not completely embedded in a rigid network. They bring out experimental data to support present models on chromosomal organization.