Chromosomes of Tumor Cells. IV. Cell Population Changes in Thymus, Spleen, and Bone Marrow During X-Ray-lnduced Leukemogenesis in C57BL/6J Mice

• Published in: JNCI : Journal of the National Cancer Institute 1965-09, Vol.35 (3), p.421-434
• Main Authors: Joneja, M. G., Stich, H. F.
• Format: Article
• Language: English
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/35.3.421

The incidence of chromosome aberrations and of cells with abnormal chromosome complements was estimated in the thymus, spleen, and bone marrow of preleukemic, leukemic, and nonleukemic C57BL/6J mice that received repeated total-body irradiations. In early stages of leukemogenesis the normal cell populations of the thymus, spleen, and bone marrow, consisting predominantly of diploid cells, changed into genetically heterogeneous ones, consisting of cells with abnormal chromosome numbers, marker chromosomes, or both. At 7 weeks after irradiation the incidence of chromosomally abnormal cells in the spleen and bone marrow was greatly reduced, whereas clones of chromosomally abnormal cells became established in the thymus of most irradiated mice. All 10 thymic lymphosarcomas examined consisted of cells with abnormal chromosome complements. The presence of particular marker chromosomes in most leukemic cells of a mouse suggests that they originate from one parent cell. Clones of chromosomally abnormal cells were also observed in the spleen and bone marrow of 2 of 5 irradiated but apparently nonleukemic mice 9 months after irradiation. The particular behavior of the cell population of the thymus, the significance of a genetically heterogeneous cell population in preleukemic mice, and the possible role of environment conditions in tissue are discussed.