Chromosome alterations that correlate with progression to immortality in Syrian hamster embryo cells transformed by gamma-irradiation.

Primary Syrian hamster embryo (SHE) cells can be transformed in vitro by gamma-irradiation or spontaneously and display morphological alterations in discrete colonies as the earliest recognizable transformants. These morphologically transformed colonies can progress to give rise to immortal cell lines. The purpose of the present study was to determine if specific chromosome changes occur that correlate with immortalization. In the non-irradiated culture, 18 transformed colonies were isolated, of which two became immortal. In the irradiated culture, six out of 18 transformed colonies isolated progress to immortalization. Seven out of eight immortalized cell lines exhibited either numerical and/or structural chromosome alterations. Of six radiation-induced immortal lines, four lines showed rearrangements in the long arms of chromosome 3 (3q +) and chromosome 6 (6q +) non-randomly. In all cases, both 3q + and 6q + were detected in the primary transformed colonies from which the immortal cell lines arose. Both 3q + and 6q + occurred always as heterozygotes in the primary-transformed colonies. 3q + and 6q + were never found in the non-irradiated culture, demonstrating that these chromosome changes were induced by irradiation. 3q + and 6q + may correlate with progression to immortality in SHE cells transformed by gamma-irradiation.