title: Volume increase and spatial shifts of chromosome territories in nuclei of radiation-induced polyploidizing tumour cells.
abstract: The exposure of tumour cells to high doses of ionizing radiation can induce endopolyploidization as an escape route from cell death. This strategy generally results in mitotic catastrophe during the first few days after irradiation. However, some cells escape mitotic catastrophe, polyploidize and attempt to undergo genome reduction and de-polyploidization in order to create new, viable para-diploid tumour cell sub-clones. In search for the consequences of ionizing radiation induced endopolyploidization, genome and chromosome architecture in nuclei of polyploid tumour cells, and sub-nuclei after division of bi- or multi-nucleated cells were investigated during 7 days following irradiation. Polyploidization was induced in p53-function deficient HeLa cells by exposure to 10Gy of X-irradiation. Chromosome territories #1, #4, #12 and centromeres of chromosomes #6, #10, #X were labelled by FISH and analysed for chromosome numbers, volumes and spatial distribution during 7 days post irradiation. The numbers of interphase chromosome territories or centromeres, respectively, the positions of the most peripherally and centrally located chromosome territories, and the territory volumes were compared to non-irradiated controls over this time course. Nuclei with three copies of several chromosomes (#1, #6, #10, #12, #X) were found in the irradiated as well as non-irradiated specimens. From day 2 to day 5 post irradiation, chromosome territories (#1, #4, #12) shifted towards the nuclear periphery and their volumes increased 16- to 25-fold. Consequently, chromosome territories returned towards the nuclear centre during day 6 and 7 post irradiation. In comparison to non-irradiated cells (∼500μm(3)), the nuclear volume of irradiated cells was increased 8-fold (to ∼4000μm(3)) at day 7 post irradiation. Additionally, smaller cell nuclei with an average volume of about ∼255μm(3) were detected on day 7. The data suggest a radiation-induced generation of large intra-nuclear chromosome territories and their repositioning prior to genome reduction.
authors.affiliation: Kirchhoff-Institute for Physics, University of Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Schwarz-Finsterle
authors.forename: Harry
authors.initials: H
authors.lastname: Scherthan
authors.forename: Anda
authors.initials: A
authors.lastname: Huna
authors.forename: Paula
authors.initials: P
authors.lastname: González
authors.forename: Patrick
authors.initials: P
authors.lastname: Mueller
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schmitt
authors.forename: Jekaterina
authors.initials: J
authors.lastname: Erenpreisa
authors.forename: Michael
authors.initials: M
authors.lastname: Hausmann
mesh_terms: D002467:Cell Nucleus / Q000473:pathology* / Q000528:radiation effects*; D002503:Centromere / Q000235:genetics; D045584:Chromosome Positioning / Q000528:radiation effects*; D002877:Chromosomes, Human / Q000528:radiation effects*; D005720:Gamma Rays; D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008677:Metaphase; D011123:Polyploidy
keywords: Chromosome number; ETC; Endopolyploid tumour cells; FISH; High dose X-irradiation; MNGC; NT; Nuclear architecture; PBS; Quantitative image analysis; SSC; cCT; endopolyploid tumour cell; fluorescence in situ hybridization; most centrally located chromosome territory; most peripherally located chromosome territory; multi-nucleated giant cells; non-irradiated; pCT; phosphate buffered saline; saline sodium citrate buffer