In two patients with plasma cell leukemia (PCL) the cytokinetics of blood and bone marrow plasmocytomatous cells was examined shortly after Peptichemio (PTC 40 mg/alternate days for 6-7 doses) therapy by combined DNA cytofluorometry and in vitro tritiated thymidine (3H-TdR) cytoautoradiography. In both cases a rapid fall in circulating plasma cells was induced by the treatment and in one of them the percentage of bone marrow plasma cells was also diminished. After treatment the values of labeling index (LI) and growth fraction (GF) were increased both in blood and bone marrow plasma cells and proliferating bone marrow plasma cells were mostly in early S phase. Their mean grain count (MGC) did not change. Increased population of U-like cells. i.e. damaged cells, was found in the bone marrow. By examining the possible explanations of the findings, the authors relate them to a cellular recruitment following tumor mass reduction. DNA content only was also determined in the blood during the treatment and an increased percentage of 2n-4n plasma cells was found. The significance of this last finding is not known at the present.
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