Duplicated chromosomal fragments stabilize shortened telomeres in normal human IMR‐90 cells before transition to senescence

Abstract

To assess why during in vitro aging of fibroblasts the maintenance of chromosomal stability is effective or occasionally fails, a detailed cytogenetic analysis was performed in normal human IMR-90 fetal lung fibroblasts. The onset of senescence was inferred from proliferation activity, expression pattern of cell cycle regulating proteins, activity of β-galactosidase, and morphological features. Over the period of proliferation, a moderate increase of non-transmissible structural chromosomal aberrations was observed. In addition, using fluorescence in situ hybridization (mFISH and mBAND) techniques, we detected clonally expanding translocations in up to 70% of the analyzed metaphases, all involving one homolog of chromosome 9 as an acceptor. Notably, chromosomes are randomly involved as donor-chromosomes of the translocated terminal acentric fragments. These fragments result from duplication because the donor chromosomes are apparently unchanged. Interstitial telomeric signals were detectable at fusion sites, most likely belonging to chromosome 9. Quantitative fluorescence in situ hybridization (QFISH) detecting telomere sequences, followed by mFISH technique revealed that already in young cells the respective telomeres of one chromosome 9 were particularly short. For the first time, we have observed dysfunctional telomeres of one specific chromosome in normal human cells that have been stabilized by duplicated terminal sequences.

Increased effectiveness of carbon ions in the production of reactive oxygen species in normal human fibroblasts

“…Susceptibility for manifesting chromosomal instability may be different in normal human fibroblasts of different origin. In lung fibroblasts (IMR-90), we have indication of a high spontaneous occurrence of DNA and chromosomal damage (our own unpublished results) and an accumulation of cytogenetic damage at the end of their life span [ 44 ]. In a previously published study, we used AG1522 cells to show that no radiation-induced genomic instability was observed in addition to the increasing instability of ageing fibroblasts [ 19 ].…”

JNK suppression of chemotherapeutic agents-induced ROS confers chemoresistance on pancreatic cancer stem cells

“…Differentiation of pancreatic CSCs was induced by culturing the cells under the differentiation-inducing condition (DMEM/F12 containing 10% FBS) for 2 weeks, as previously described [ 15 ]. Normal human IMR90 fetal lung fibroblasts [ 46 , 47 ] were obtained from American Type Culture Collection and maintained in DMEM/F12 supplemented with 10% fetal bovine serum (FBS) and 100 units/mL penicillin and 100 μg/mL streptomycin. All IMR90 experiments were performed using low passage number (less than 9) cells.…”

The Fate of a Normal Human Cell Traversed by a Single Charged Particle

“…Chromosomes were stained by mFISH, using a 24XCyte mFISH kit according to the protocol recommended by the manufacturer (Metasystems). Image capturing and processing was performed as described elsewhere33. Generally, 100 metaphases containing 45 or 46 chromosomes were scored.…”