Chromosomal Banding Patterns and in Vitro Transformation of Syrian Hamster Cells

Summary

Chromosome banding techniques were used to analyze the chromosomal constitution of hamster cells transformed by chemical carcinogens and fibrosarcomas obtained after injection of the transformed cell lines. Each transformed line is considered unique because each was derived from fetal material from a different pregnant animal. The chromosome modes of the transformed lines and tumors were generally near-diploid. Analysis of bands verified the occurrence of identical banding patterns in the marker chromosomes of transformed lines and tumor-derived cultures, thus providing unequivocal evidence that the fibrosarcomas were produced by the cells that were transformed in vitro and making it possible to recognize 10 marker chromosomes and their origin. Different carcinogens may produce transformations associated with the same specific marker, but not all transformed lines have the same markers even with the same chemical carcinogen. Some markers were found in the tumor-derived culture and not the transformed line or occurred in later passages of both the transformed line and tumor cultures but not in the early passage of these lines. In some transformed cell lines the chromosome number increased but did not involve a specific chromosome group or pair. The incidence of chromosomal deviation in cancer is species dependent and contributes to the characteristics of cancer. Chromosome alterations are responsible for the genotypic changes capable of autonomous growth and thus are considered reflections of secondary alterations. The question whether chromosome changes are the causal factors in carcinogenesis remains unanswered.