[Features of rat cells karyotypic abnormalities in rat cells in their transformation in vitro]

Neoplastic transformation of cells is characterized by karyotypic abnormalities involving aneuploidy, quantitative changes, as well as multiple clonal rearrangements of the number and structure of chromosomes. It is probable that chromosomes are one of the mechanisms of cells immortalization and transformation. Despite many years of study of chromosomal rearrangements, data on primary chromosomal rearrangements in early stages of transformation is still insufficient. We examined karyotypic abnormalities in embryonic rat fibroblasts in both the spontaneous transformation and transformation by oncogenes at different passages in vitro. Literature data and results of our cytogenetical analysis of rat cells lines established by different methods of transformation of cells of different tissue origin in vitro have shown that cell karyotype at early passages may either be normal or acquire diverse clonal chromosomal abnormalities. At later passages, other chromosomes of karyotype are involved in new rearrangements. Despite this, some of the lines do not acquire the malignant phenotype and remain to be immortalized. The role of instable chromosomes and their loci in immortalization and transformation of cells is discussed.