title: Arsenic trioxide augments all-trans retinoic acid-induced differentiation of HL-60 cells.
abstract: OBJECTIVE
  All-trans retinoic acid (ATRA) is used to treat patients with acute promyelocytic leukemia (APL) due to its ability to resume the differentiation of APL cells. Recently, clinical trials have been started to evaluate ATRA plus arsenic trioxide (ATO) as a combination treatment for APL patients. However, little is known about the detailed mechanisms underlying its efficacy. We therefore investigated the effects of this combination on the differentiation and differentiation-related gene expression.
  
  
  METHODS
  Human leukemia HL-60 cells differentiation was examined using nitro blue tetrazolium and CD11b. The levels of mRNA and protein were determined by RT-qPCR, microarray, western blot and ELISA, respectively. The promoter activity was assessed by luciferase activity. The arsenic concentration was determined by ICP-MS.
  
  
  RESULTS
  ATRA-induced HL-60 differentiation was augmented by co-treatment with ATO. A microarray analysis showed that ATRA plus ATO treatment markedly down-regulated the expression of proteinase 3 (PRTN3), which is involved in the differentiation arrest of leukemia cells, compared with treatment with ATRA alone. The PRTN3 mRNA level was suppressed by treatment with ATRA alone, and then further suppressed by co-treatment with ATO, accompanied by a concomitant increase in Sp1 protein, which is known to facilitate differentiation. The expression levels of azurocidin, telomerase reverse transcriptase, ferritin, and interleukin-1β were also altered by co-treatment with ATO.
  
  
  CONCLUSIONS
  Co-treatment with ATO enhances ATRA-induced HL-60 differentiation by altering the expression of genes involved in cell differentiation, providing the molecular basis for a combination therapy using ATO plus ATRA to treat leukemia patients.
authors.affiliation: Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan.
authors.forename: Daigo
authors.initials: D
authors.lastname: Sumi
authors.affiliation: Department of Hematology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennno-dai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Suzukawa
authors.affiliation: Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan. Electronic address: himenos@ph.bunri-u.ac.jp.
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Himeno
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage*; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D018922:HL-60 Cells; D006801:Humans; D010087:Oxides / Q000008:administration & dosage*; D014212:Tretinoin / Q000008:administration & dosage*
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D014212:Tretinoin; D000077237:Arsenic Trioxide
keywords: Acute myeloid leukemia; Azurocidin 1; Proteinase 3; Sp1