Chromosomal analysis of some transplanted tumors induced by 3‐methylcholanthrene in golden hamsters

Three primary tumors induced by 3‐MCA in the golden hamster, with a diploid chromosome constitution and a short latency period, were allogeneically transplanted. Three tumor lines with a total of 19 individual transplanted tumors were chromosomally analyzed. None of the originally diploid tumors preserved its chromosomal constitution in allogeneic serial transplantation. A model of heteroploid transformation was established. In two tumor lines the presence of host cells was observed and in one line at advanced passages a new tumor‐cell population occurred with multiple severe chromosomal aberrations derived from the host cells. No specific chromosomal changes could be observed, but each line was characterized by chromosomal markers and a non‐random distribution in some chromosome groups was identified. The spontaneous occurrence of chromosomal aberrations with a very high incidence occurring in the host cells at advanced passages could not be accounted for by direct action of the chemical substance and possible secondary factor/s of a viral or metabolic nature are discussed.