Chromosomal aberrations and genetic instability in long-term cultures of nor- mal human fibroblast cell lines*

Introduction Former experiments have shown an increase in number of unstable chromosomal aberrations in normal human fibroblast strains with ongoing culturing time of the populations [1, 2]. These de novo formed unstable aberrations are an indicator of genomic instability which is considered to be one important step towards carcinogenesis. In the same experiments we observed the accumulation of stable aberrations during culturing time, in some cases as clonal aberrations in normal human fibroblasts [2]. We intend to assess whether both effects are interrelated, especially because stable aberrations and their clonal amplifications are reported to be involved in the formation of tumors, especially soft tissue sarcomas [3]. Materials and Methods Four fibroblast cell lines originating from three different tissues were cultured up to 7 months until they reached replicative senescence (AG1521A, AG1522C/D, NHDF, IMR-90). The cells were subcultured every 2 weeks and chromosome samples were prepared. Unstable aberrations such as dicentrics, rings or breaks were scored regularly after solid Giemsa staining (100 metaphases per time point). At representative time points stable aberrations were assessed by analyzing 100 metaphases using the multiplex fluorescence in situ hybridization (mFISH).