Research on the Genetic Mechanism of Leukemogenesis

We have studied the chromosome in human- and mouse-leukemia and made a further investigation into the normal somatic chromosome in order to compare the normal complex with the chromosome condition in leukemic cells. Further, we have performed a search of virus within the leukemic tissue in the human- and mouse-leukemia to throw light on the causes of the change in karyotype of leukemia. The major conclusion obtained from the present study are summarized as follows: 1) The somatic chromosorrme number of normal C 58 mice was 40 in every cell and the chromosome pattern was found to be entirely composed of rod-shaped chromosomes. In our mouse leukemia the basic chromosome number was also 40, but it showed a variation ranging from 32 to 43, and chromosome pattern was found to be also entirely composed of rod-shaped chromosomes. However, in the leukemic cells the dotlike chromosome (very short rodshaped one) which is never found in the somatic cells is to be seen, and one of the medium sized chromosome undergone a change in chemical structure, that is to say, it does not get stained with acetic orcein at the intermediate part of its arm and so the arm of this chromosome looks as if it were cut in two. 2) The normal somatic chromosome number of human adults is determined as 46 in both sexes, though there is a variation ranging from 40 to 50, and also there are found a few cells which show polyploid number and polypolar division. The normal somatic human complex consists of 22 pairs of homolognous chromosome and a pair of sex-element and the X-element represented by a large L-shaped chromosome having a submedian centromere, while the smaller one does the Y-element. The stemline chromosome number in leukemic cells varies with each of the cases of the nryelogenous leukemia, and this is not only 46 but also 44 or 45. But the chromosome in human leukemia is nearly identical both in number and in pattern with that of the somatic human cells. However, the large L-shaped chromosome corresponding to the X-element disappears in most leukemic cells and an increase of rod-shaped chromosome is very frequently to be seen. 3) We could observe the virus-like particles in the leukemic tissue of the mouse leukemia and of a human leukemia. Hence, there is possibility that the change in chromosome in these mouse- and human-leukemia may be due to virus, but this is not yet determined at present.