SOME BIOCHEMICAL ASPECTS OF LEUKAEMIAS: THE APPEARANCE OF A SOLUBLE DISULPHIDE IN THE BLOOD IN CHRONIC GRANULOCYTIC LEUKAEMIA

Evolutionary Dynamics of Chronic Myeloid Leukemia Progression: the Progression-Inhibitory Effect of Imatinib

The t(9;22) translocation that causes chronic myeloid leukemia (CML) drives both transformation and the progression process that eventually results in the disease changing to acute leukemia. Constitutively activated Bcr-Abl signaling in CML creates high levels of reactive oxygen species (ROS) that produce 8-oxo-guanine in DNA; this is mutagenic and causes chronic phase (CP) progression to blast phase (BP). We modeled three types of mutations involved in this progression: mutations that result in myeloid progenitor cells proliferating independently of external growth factors; mutations causing failure of myeloid progenitor cells to differentiate; and mutations that enable these cells to survive independently of attachment to marrow stroma. We further modeled tyrosine kinase inhibitors (TKI) as restoring myeloid cell apoptosis and preventing ROS-driven mutagenesis, and mutations that cause TKI resistance. We suggest that the unusually low rate of resistance to TKI arises because these drugs deplete ROS, which in turn decrease mutation rates.

A pharmacodynamic model of Bcr-Abl signalling in chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is an unusual malignancy in which myeloid progenitor cells are transformed by a single chromosomal translocation where the Bcr domain of chromosome 22 is placed adjacent to the proto-oncogene c-Abl of chromosome 9, resulting in constitutive Abl tyrosine kinase activity. This has a twofold effect: it causes increased numbers of myeloid progenitor cells and circulating myeloid cells, and it causes leakage of reactive oxygen species from mitochondria. We describe a kinetic and pharmacodynamic (PD) model of Bcr-Abl signalling in myeloid cells that is used to simulate effects of four classes of drugs: Bcr-Abl signalling inhibitors, such as imatinib, cyclin-dependent kinase inhibitors, and pro- and anti-oxidants. The model also has the potential to describe the PD effects of agents acting on other sites in the Bcr-Abl signalling pathway. Having calibrated the model against dose-response curves of these drugs acting as single agents on Bcr-Abl-transformed cells in vitro, the model was used to predict effects of the agents in combination. Used in conjunction with pharmacokinetic models, our PD model enables an approach to protocol optimization: large numbers of doses and timings and (in the case of combination treatments) relative dose ratios can be simulated in silico. Predicted selectivity, as well as efficacy, can be extracted from the model. An understanding of the Bcr-Abl signalling pathway has implications for strategies to prevent acquired drug resistance, and for preventing or delaying CML progression to its blast phase.

Synthesis and biological activity of some 1-N-substituted 2-acetamido-2-deoxy-beta-D-glycopyranosylamine derivatives and related analogs

Several 1-N-substituted derivative [haloacetyl-, glycyl-, (dimethyl)amino-acetyl-, azidoacetyl-, trifluoroacetyl-, and trifluoromethylsulfonyl-] of 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-beta-D-glucopyranosylamine (1) were synthesized as potential metabolic inhibitors of cellular-membrane glycoconjugates. Several fully acetylated derivatives were found to inhibit growth of mouse mammary adenocarcinoma TA3, leukemia L1210, or leukemia P-288 cells at 1-0.01 mM concentration in vitro. Some of these derivatives were less active after O-deacetylation. Analogs of 1 in which NH2-1 was replaced by OH- or OAc-1 were also active on the same cell systems. The growth-inhibitory activity was correlated with inhibition of the incorporation of 2-amino-deoxy-D-glucose and L-leucine into a macromolecular fraction.

Studies in the enzymology of glutathione metabolism in human erythrocytes

Spectrophotometric assay methods are described for glutathione synthetase, gamma-glutamylcysteine synthetase and gamma-glutamyl transpeptidase of erythrocytes. The contents of these enzymes in normal human erythrocytes are reported. Erythrocyte glutathione synthetase is inhibited by ADP; this inhibition is competitive with respect to ATP. gamma-Glutamylcysteine synthetase is subject to feedback inhibition by GSH, and is also inhibited by NADH, and to a lesser extent by NAD(+) and NADPH. This enzyme is irreversibly inactivated by cysteamine.