title: Src Family Kinase Inhibitor PP2 Has Different Effects on All-Trans-Retinoic Acid or Arsenic Trioxide-Induced Differentiation of an Acute Promyelocytic Leukemia Cell Line.
abstract: OBJECTIVE
  Leukemic promyelocytes have the unique ability to undergo differentiation after exposure to retinoic acid and both differentiation and apoptosis after exposure to arsenic trioxide (ATO). Recent studies have shown that inhibition of Src family kinases (SFKs) resulted in enhancement of retinoic acid-induced myeloid differentiation.
  
  
  METHODS
  In this study, we investigated the question of whether the SFK inhibitor PP2 enhanced the differentiation of NB4 cells when combined with ATO as well as when combined with all-trans-retinoic acid (ATRA). In addition, we attempted to determine the difference in retinoic acid-induced gene expression between cells treated with PP2 in combination with ATRA and in combination with ATO.
  
  
  RESULTS
  SFK inhibitor PP2 induced significant enhancement of ATRA- or ATO-induced differentiation of NB4 cells. A significantly stronger synergistic effect was observed when PP2 was combined with ATRA than when combined with ATO. Flow cytometric analysis demonstrated a significant increase in CD11b-positive granulocytes up to 60.73% and 31.58%, respectively. These results were confirmed by nitroblue tetrazolium staining. These effects were not related to apoptosis. Results of Annexin-V-fluorescein staining revealed that PP2 combined with ATRA or PP2 combined with ATO did not induce apoptosis in NB4 cells. Retinoic acid-induced gene expression was different in both groups. Intercellular adhesion molecule-1 expression showed a significant increase in cells treated with PP2 in combination with ATRA, whereas cathepsin D expression showed a significant increase in cells treated with PP2 in combination with ATO.
  
  
  CONCLUSIONS
  Our data showed that SFK inhibitor PP2 enhanced acute promyelocytic leukemia cell differentiation when combined with either ATRA or ATO with difference in activation of retinoic acid-induced genes.
authors.affiliation: Division of Hematology-Oncology, Department of Internal Medicine, Institute for Clinical Molecular Biology Research, Soonchunhang University Hospital, Soonchunhang University College of Medicine, Seoul, Korea.
authors.forename: Suk-Gu
authors.initials: SG
authors.lastname: Yoon
authors.forename: Hee-Jeong
authors.initials: HJ
authors.lastname: Cheong
authors.forename: Sook-Ja
authors.initials: SJ
authors.lastname: Kim
authors.forename: Kyoung Ha
authors.initials: KH
authors.lastname: Kim
authors.forename: Sang-Cheol
authors.initials: SC
authors.lastname: Lee
authors.forename: Namsu
authors.initials: N
authors.lastname: Lee
authors.forename: Hee Sook
authors.initials: HS
authors.lastname: Park
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Won
keywords: Acute promyelocytic leukemia; All-trans-retinoic acid; Arsenic trioxide; Cell differentiation; Src kinase