title: NOTCH knockdown affects the proliferation and mTOR signaling of leukemia cells.
abstract: OBJECTIVE
  The effects of small interfering RNA (siRNA)-mediated knockdown of NOTCH1 and NOTCH2 on cell proliferation and downstream signaling pathways in leukemia cells were examined.
  
  
  METHODS
  Two T-lymphoblastic leukemia (T-ALL) cell lines and two acute myeloblastic leukemia (AML) cell lines were transfected with siRNAs targeting NOTCH1 and NOTCH2. The effects of knockdown on cell proliferation and protein expression were examined by colorimetric WST-8 assay and immunoblotting, respectively.
  
  
  RESULTS
  In T-ALL cell lines, NOTCH1 knockdown as well as NOTCH2 knockdown suppressed cell proliferation and induced apoptosis. v-Myc avian myelocytomatosis viral oncogene homolog (MYC) protein expression was down-regulated in NOTCH1-knockdown cells but not affected in NOTCH2-knockdown cells. In AML cell lines, cell proliferation was not significantly affected by NOTCH siRNAs. NOTCH2 knockdown increased the level of cleaved NOTCH1 fragment without increasing NOTCH1 expression. NOTCH knockdown reduced the level of mechanistic target of rapamycin (mTOR) protein in the monoblastic leukemia cell line THP-1. Contrastingly, NOTCH activation by NOTCH ligand stimulation increased the expression of mTOR in THP-1 cells.
  
  
  CONCLUSIONS
  These novel findings on NOTCH signaling may contribute to the development of effective NOTCH-targeted therapies against leukemia.
authors.affiliation: Department of Laboratory Medicine, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-Ku, Tokyo 113-8519, Japan. tohda.mlab@tmd.ac.jp.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Okuhashi
authors.forename: Mai
authors.initials: M
authors.lastname: Itoh
authors.forename: Nobuo
authors.initials: N
authors.lastname: Nara
authors.forename: Shuji
authors.initials: S
authors.lastname: Tohda
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006801:Humans; D007938:Leukemia; D034741:RNA, Small Interfering / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics* / Q000378:metabolism; D051883:Receptor, Notch2 / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: C497761:NOTCH1 protein, human; C497764:NOTCH2 protein, human; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D051883:Receptor, Notch2; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases
keywords: Leukemia; MYC; NOTCH; mTOR; siRNA