h-89 and Leukemia--Myeloid

ST1926 is an atypical retinoid and a promising anti-tumour agent with selective apoptotic activity on the leukaemic blast. The anti-tumour activity of the compound has been associated with its capacity to induce DNA double stranded breaks. Target profiling by affinity chromatography coupled to mass spectrometry led to the identification of histone H2A.Z as a protein capable of binding ST1926 specifically. The result was confirmed by studies involving Surface Plasmon Resonance (SPR). This indicates that H2A.Z is a primary target of ST1926 and links the perturbations of the histone pathway observed by microarray analysis to the DNA damage and apoptotic responses caused by the atypical retinoid. Comparison of the whole-genome gene-expression profiles of the ST1926-sensitive NB4 and the ST1926-resistant NB4.437r cell lines demonstrated differential expression of numerous genes. Network analysis of the data indicated enrichment of the cellular pathways controlling cAMP (cyclic adenosine-monophosphate)-dependent signal transduction, proteasome-dependent protein degradation and nuclear histones in NB4.437r cells. Pharmacological inhibition of cAMP-dependent protein kinase A with H89 partially reverted resistance of NB4.437r cells to ST1926. Conversely, inhibition of the proteasome with MG132 or bortezomib blocked the apoptotic response afforded by ST1926 in the NB4 cell line. This last effect was associated with a dramatic reduction in the DNA damage caused by the atypical retinoid. The results corroborate the idea that DNA damage is an important determinant of ST1926 apoptotic activity. More importantly, they demonstrate a proactive role of the proteasome in the DNA damaging and ensuing apoptotic response observed upon the challenge of acute myeloid leukaemia cells with ST1926.

Topics: Acute Disease; Adamantane; Apoptosis; Blotting, Western; Cell Line, Tumor; Cell Survival; Cinnamates; Cyclic AMP-Dependent Protein Kinases; Drug Resistance, Neoplasm; Enzyme Inhibitors; Gene Expression Profiling; Gene Expression Regulation, Leukemic; Histones; Humans; Isoquinolines; Leukemia, Myeloid; Leupeptins; Oligonucleotide Array Sequence Analysis; Proteasome Endopeptidase Complex; Protein Binding; Signal Transduction; Sulfonamides; Surface Plasmon Resonance

Bafilomycin A1, a selective inhibitor of vacuolar H+-ATPase, time- and dose-dependently induced the differentiation of M1 cells, a murine myeloid leukemic cell line, into macrophage-like cells as revealed by the phagocytosis of polystyrene latex particles. This differentiation was inhibited not only by actinomycin D and cycloheximide but also by ST-638 (an inhibitor of tyrosine kinase). However, it was affected neither by K-252a (an inhibitor of C-kinase) nor by H-89 (an inhibitor of A-kinase), in contrast to the M1 cell differentiation induced by leukemia inhibitory factor (LIF). Okadaic acid inhibited both the bafilomycin A1-induced and LIF-induced differentiation of M1 cells.

Topics: Animals; Anti-Bacterial Agents; Carbazoles; Cinnamates; Ethers, Cyclic; Growth Inhibitors; Indole Alkaloids; Interleukin-6; Isoquinolines; Leukemia Inhibitory Factor; Leukemia, Myeloid; Lymphokines; Macrolides; Macrophages; Mice; Okadaic Acid; Phagocytosis; Phosphoprotein Phosphatases; Phosphorylation; Protein Biosynthesis; Protein Kinase C; Protein Kinase Inhibitors; Proton-Translocating ATPases; RNA; Sulfides; Sulfonamides; Tumor Cells, Cultured; Vacuoles