h-89 and Leukemia--Promyelocytic--Acute

Low dose arsenic trioxide(As2O3) is one of the effective treatments for patients with acute promyelocytic leukemia (APL). As2O3 could induce complete remission in de novo APL patients as well as in relapsed APL patients who have been resistant to all-trans retinoic acid (ATRA). However, the underlying mechanisms of As2O3-induced remission remain obscure. Therefore, we designed this study to explore the possible mechanism of low dose As2O3 in treatment of the patients with APL.. The APL cell line NB4 and primary malignant cells isolated from APL patients were used as in vitro models. Cell differentiation was determined by cell morphology, NBT reduction test and cytometry assay of cell differentiation antigens. The change of PML-RAR alpha fusion protein was analyzed by immunofluorescence and Western blot.. The 0.25 mumol/L As2O3 combined with cyclic adenosine monophosphate(cAMP) analogue, 8-(4-chlorophenylthio) adenosine 3', 5'-cyclic monophosphate (8-CPT-cAMP), had induced differentiation in NB4 cell line and primary cells. It was also found that this effect could be attenuated by H89, a specific PKA inhibitor. Moreover, 8-CPT-cAMP was able to facilitate the As2O3-mediated degradation of PML-RAR alpha.. The 8-CPT-cAMP could enhance As2O3-induced differentiation in APL cells.

Topics: Antineoplastic Agents; Arsenic Trioxide; Arsenicals; Cell Differentiation; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Drug Interactions; Drug Resistance, Neoplasm; Enzyme Inhibitors; Humans; Isoquinolines; Leukemia, Promyelocytic, Acute; Oxides; Sulfonamides; Thionucleotides; Tumor Cells, Cultured

The mRNA of transferrin receptor (TfR) is constitutively expressed in proliferating human leukaemic HL-60 cells. Treatment of HL-60 cells with phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, or dibutyryl-cyclic AMP (dbcAMP), a protein kinase A (PKA) activator, resulted in a 90% decrease in the level of TfR mRNA. Inhibition of TfR mRNA expression induced by 10 nM PMA and 100 microM dbcAMP was abolished by prior incubation of cells with 0.1-1.0 microM GF109203X, a PKC-specific inhibitor, and 1-10 microM H-89, a PKA-specific inhibitor, respectively. The blocking effects of GF109203X and H-89 were dose-dependent and complete at the highest concentrations of the inhibitors used. Although treatment of cells with GF109203X or H-89 alone did not alter the constitutive expression of TfR mRNA, incubation of cells with 30-100 nM staurosporine, a wide-spectrum protein kinase inhibitor, resulted in suppression of the constitutive expression of TfR mRNA in a dose-dependent manner. These results suggest that (i) the down-regulation of TfR mRNA expression during the differentiation of HL-60 cells can be mediated by activation of either PKC or PKA; (ii) the constitutive expression of TfR mRNA in proliferating HL-60 cells is staurosporine-sensitive and is probably maintained by protein kinase(s) other than PKC and PKA.

Topics: Alkaloids; Bucladesine; Cell Division; Cell Line; Cyclic AMP-Dependent Protein Kinases; DNA, Neoplasm; Enzyme Activation; Gene Expression; Humans; Indoles; Isoquinolines; Leukemia, Promyelocytic, Acute; Maleimides; Protein Kinase C; Protein Kinases; Receptors, Transferrin; RNA, Messenger; Staurosporine; Sulfonamides; Tetradecanoylphorbol Acetate; Thymidine; Tumor Cells, Cultured