Perturbation of generation cycle of human leukaemic blast cells in vivo by daunomycin

Effects of cytapheresis on cell cycle distribution of peripheral blood and bone marrow cells in some hematological malignancies

Feulgen-DNA cytophotometry and 3H-thymidine autoradiography were used to evaluate therapeutic cytapheresis effects on cell cycle distributions of peripheral blood leukemic cells in 15 acute leukemia, 5 CML and 8 CLL patients and of bone marrow erythroblasts in 18 PV patients. Both individual cytapheresis procedures and a long-term program of cytapheresis altered cell cycle distributions and biochemistry which may be summarized as follows: An increase in percentage of cells in S-phase (acute leukemia, CML); a decrease in the differences between values of S-cell number obtained by cytophotometry and autoradiography (acute leukemia, CML, PV); a decrease in some cases in enlarged fraction of cells in G2 (blast crisis of CML, PV); an activation of G0----G1 transition and an increase in the PAS-positive lymphocyte fraction in CLL patients. An apparent increase of blasts in S-phase was found after a pheresis in acute leukemia patients who responded to subsequent chemotherapy. In "nonresponders", a pheresis had no effect on cell cycle distributions. The results of the study demonstrate that despite the wide variability of individual responses, cytapheresis activates cell proliferation and metabolic processes in patients with hematological malignancies.

Effects of cytosine arabinoside and daunorubicin on survival and cell cycle progression of Chinese hamster ovary cells

Kinetic and cytotoxic effects of cytosine arabinoside (Ara-C) and daunorubicin (DNR) on exponentially growing Chinese hamster ovary (CHO) cells were measured by flow cytometry and by a colony-forming assay, respectively. With Ara-C alone, increasing drug concentrations between 10(-7) M and 10(-4) M, for up to 27 hr, were associated with increased inhibition of cell progression through the S phase. Even at the very toxic concentration of 10(-4) M, however, cells were able to enter and progress slowly through S. DNR, which appears to enter these cells relatively slowly, was highly toxic even at 2 X 10(-7) M. It decreased the rate of progression through S phase and caused cells to accumulate in G2, except at the highest concentration (2 X 10(-5) M, at which progression was inhibited throughout the cycle. Simultaneous exposure of the cells to Ara-C and DNR yielded cell cycle distributions similar to those of the former drug alone. When cells were exposed to a non-lethal dose of Ara-C and to a dose of DNR which was lethal to a fraction of the cell population (or conversely), either simultaneously or separated by a drug-free interval, small, but in some cases significant, drug interactions were observed. These effects were not caused by drug-induced redistribution of cells within the cell cycle, but may have been related to the effects of the non-lethal drug on DNA synthesis rate.

Bone-marrow-profileration patterns in acute myeloblastic leukaemia determined by pulse cytophotometry

The proliferation patterns of normal and leukaemic bone-marrow were studied by measuring the D.N.A. content of large numbers of cells by pulse cytophotometry (P.C.P.). In nineteen normal bone-marrow samples an average of 66-3% of the bone-marrow cells were in the G1 phase (2n D.N.A.), 26-1% in the S phase (2n smaller than D.N.A. smaller than 4n), and 7-5% in G2+M phase (4n D.N.A.). The percentages of S-phase cells determined by autoradiography and P.C.P. correlated well, both in normal and in leukaemic bone-marrow. In 25 patients with untreated acute myeloblastic leukaemia (A.M.L.) lower percentages of cells were found in S and G2+M phases, indicating a smaller proliferating pool compared with normal bone-marrow. The likelihood of a complete remission being attained in A.M.L. with the first treatment course was correlated with the percentage of S-phase cells present before treatment. At remission in A.M.L. the proliferation pattern was restored to normal.