The effect of procarbazine on the chromosomes of normal and malignant mouse cells

The effects of the cancer drug methylhydrazine derivative procarbazine (PC) on the chromosomes of normal and malignant cells in the mouse strains Swiss Albino, CF1, and BDF1 have been analyzed. PC broke chromosome in the hypotetraploid Ehrlich and the diploid P388 ascites tumors. Practically all breaks seemed to be of the G2 type and, as far as could be determined, took place in the quinacrine-dark or the corresponding Giemsa-light regions. The vast majority of the broken ends had rejoined to form chromatid translocations. No increase in chromosome breaks were seen in any of the normal tissues treated in vivo: spleen, bone marrow, spermatocytes, or spermatogonia (in this tissue the cells were not counted). The chromosomes of the Ehrlich ascites tumor have been studied by means of both Q-banding and G-banding. Very few, if any, chromosomes seem to have an exact homologue or to correspond to any of the normal mouse chromosomes.