title: Curcumin Veto the Effects of Osteopontin (OPN) Specific Inhibitor on Leukemic Stem Cell Colony Forming Potential via Promotion of OPN Overexpression.
abstract: BACKGROUND
  Acute myeloid leukemia (AML) is an immunophenotypically heterogeneous malignant disease, in which CD34 positivity is associated with poor prognosis. Osteopontin (OPN) plays different roles in physiologic and pathologic conditions like: survival, metastasis and cell protection from cytotoxic and apoptotic stimuli. Due to anti-apoptotic effect of OPN in normal and malignant cells, silencing of OPN leads to elevation of sensitivity towards chemotherapeutic agents and attenuates cancer cells migration and invasion. Therefore, the aim of this study was to evaluate OPN roles in modulating curcumin-mediated growth inhibitory on leukemic stem cells (LSCs) colony forming potential and survival in AML cell lines and primary CD34+/CD38- bone marrow-derived AML cells.
  
  
  METHODS
  Primary human CD34+/CD38- cells were isolated from bone marrow mononuclear cells of 10 AML patients at initial state of diagnosis, using a CD34 Multi sort kit. The growth inhibitory effects of curcumin (CUR) were evaluated by MTT and colony-formation assays. Apoptosis was analyzed by 7AAD assay in CD34+ KG-1, U937 cell lines and primary isolated cells. Short interfering RNA (siRNA) against OPN was used for OPN silencing in both cell lines and primary AML cells. Then, transfected cells were incubated with/without curcumin. The change in OPN gene expression was examined by Real-time PCR.
  
  
  RESULTS
  CUR inhibited proliferation and induced apoptosis in both KG-1 and U937 cells and also primary isolated AML cells. OPN silencing by siRNA increased the susceptibility of KG-1, U937 and primary CD34+/CD38- AML cells to apoptosis. Moreover, soft agar colony assays revealed that silencing of OPN with siRNA significantly decreased colony numbers in LSCs compared with the non-targeting group. Furthermore, CD34+/CD38- populations as a main LSCs compartment through OPN overexpression towards CUR treatment might be nullified the inhibitory effects of OPN siRNA on their survival and colony forming potential.
  
  
  CONCLUSIONS
  Taken together, our results suggested that knockdown of OPN using OPN specific siRNA significantly decreased colony numbers in LSCs and this effect might be vetoed by LSCs via induction of OPN overexpressionin combination of CUR and siRNA.
authors.affiliation: Iranian Blood Transfusion Research Center, High Institute for Education and Research in Transfusion Medicine, Tehran, Iran; Hematology-Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Mohammadi
authors.affiliation: Hematology-Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Seyed H
authors.initials: SH
authors.lastname: Ghaffari
authors.affiliation: Iranian Blood Transfusion Research Center, High Institute for Education and Research in Transfusion Medicine, Tehran, Iran.
authors.forename: Mojgan
authors.initials: M
authors.lastname: Shaiegan
authors.affiliation: Iranian Blood Transfusion Research Center, High Institute for Education and Research in Transfusion Medicine, Tehran, Iran.
authors.forename: Mahin
authors.initials: M
authors.lastname: Nikogoftar Zarif
authors.affiliation: Hematology-Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Nikbakht
authors.affiliation: Hematology-Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Kamran
authors.initials: K
authors.lastname: Alimoghaddam
authors.affiliation: Hematology-Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ardeshir
authors.initials: A
authors.lastname: Ghavamzadeh
keywords: Colony forming potential; Curcumin; Leukemic stem cell; Osteopontin; SiRNA