title: Protein tyrosine phosphatase-dependent activation of beta-globin and delta-aminolevulinic acid synthase genes in the camptothecin-induced IW32 erythroleukemia cell differentiation.
abstract: Camptothecin, an antitumor drug that specifically targets topoisomerase I, induced IW32 erythroleukemia cells to differentiate along the erythroid pathway, as demonstrated by the increased mRNA and protein expression of hemoglobin. Unlike other chemically induced erythroleukemia cell differentiation, no c-myc mRNA down-regulation was observed in the early phases of drug treatment. Among the heme-synthesizing enzyme mRNAs that were analyzed, only that of the erythroid-specific delta-aminolevulinic acid synthase (ALAS-E) was stimulated. Vanadate or benzylphosphonic acid, which inhibited protein tyrosine phosphatases (PTPase), blocked the camptothecin-induced differentiation. Maximal inhibition was attained if vanadate was added within the first 6 hr of camptothecin treatment, after which vanadate gradually lost its effectiveness. Camptothecin-induced expression of beta-globin or ALAS-E transcript levels was inhibited in the presence of cycloheximide or vanadate. It was also shown that vanadate blocked differentiation of IW32 cells induced by sodium butyrate, VM-26, and p53. Increased PTPase activity could be observed 48 hr after cells were treated with camptothecin, VM-26, or sodium butyrate. Analysis of PTPase activity in the course of camptothecin treatment showed elevated levels of PTPase in the cytosol and the nucleus, with a greater increase demonstrated in the cytosol than in the nucleus. Our results suggest that by stimulating the beta-globin and ALAS-E gene expression, PTPase plays a critical role in the induced differentiation of IW32 erythroleukemia cells.
authors.affiliation: Institute of Biochemistry, College of Life Sciences, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: M C
authors.initials: MC
authors.lastname: Wang
authors.forename: J H
authors.initials: JH
authors.lastname: Liu
authors.forename: F F
authors.initials: FF
authors.lastname: Wang
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002166:Camptothecin / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects / Q000502:physiology*; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics; D004915:Leukemia, Erythroblastic, Acute / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics; D051379:Mice; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology*; D013713:Teniposide / Q000494:pharmacology; D013997:Time Factors; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D002087:Butyrates; D004791:Enzyme Inhibitors; D011500:Protein Synthesis Inhibitors; D020148:Butyric Acid; D014638:Vanadates; D005914:Globins; D013713:Teniposide; D003513:Cycloheximide; D000624:5-Aminolevulinate Synthetase; D017027:Protein Tyrosine Phosphatases; D002166:Camptothecin