Cytological, cytogenetic and ultrastructural studies of rat cell lines carrying avian and murine sarcoma genomes

Two rat cell lines (RSK 4 and XC) which carry the RSV genome but do not produce infectious virus were studied together with a control rat cell line (LW 13). One rat cell line (MSB-1) which carries the MSV genome and produces infectious particles was also studied. The cells carrying viral sarcoma genome showed pleomorphic cytology. All cell lines showed acid phosphatase positivity, indicating the presence of lysosomes, but only cells of the MSB-1 line contained glycogen granules. Cytogenetic studies revealed a wide range of chromosomal changes. Most cells carrying sarcoma viral genome contained large metacentric and/or submetacentric “marker” chromosomes. Such chromosomes are not present in normal rat cells even after prolonged in vitro cultivation. Many of the RSK 4 cells showed a chromosome number ranging between 70 to 80, while XC cells showed a pseudodiploid pattern with a chromosome number around the normal. About half the MSB-1 cells contained between 50–60 chromosomes.