title: Saponins from Rubus parvifolius L. induce apoptosis in human chronic myeloid leukemia cells through AMPK activation and STAT3 inhibition.
abstract: BACKGROUND
  Saponins are a major active component for the traditional Chinese medicine, Rubus parvifolius L., which has shown clear antitumor activities. However, the specific effects and mechanisms of saponins of Rubus parvifolius L. (SRP) remain unclear with regard to human chronic myeloid leukemia cells. The aim of this study was to investigate inhibition of proliferation and apoptosis induction effects of SRP in K562 cells and further elucidate its regulatory mechanisms.
  
  
  METHODS
  K562 cells were treated with different concentrations of SRP and MTT assays were performed to determine cell viability. Apoptosis induction by SRP was determined with FACS and DAPI staining analysis. Western blotting was used to detect expression of apoptosis and survival related genes. Specific inhibitors were added to confirm roles of STAT3 and AMPK pathways in SRP induction of apoptosis.
  
  
  RESULTS
  Our results indicated that SRP exhibited obvious inhibitory effects on the growth of K562 cells, and significantly induced apoptosis. Cleavage of pro-apoptotic proteins was dramatically increased after SRP exposure. SRP treatment also increased the activities of AMPK and JNK pathways, and inhibited the phosphorylation expression level of STAT3 in K562 cells. Inhibition of the AMPK pathway blocked the activation of JNK by SRP, indicating that SRP regulated the expression of JNK dependent on the AMPK pathway. Furthermore, inhibition of the latter significantly conferred resistance to SRP pro- apoptotic activity, suggesting involvement of the AMPK pathway in induction of apoptosis. Pretreatment with a STAT3 inhibitor also augmented SRP induced growth inhibition and cell apoptosis, further confirming roles of the STAT3 pathway after SRP treatment.
  
  
  CONCLUSIONS
  Our results demonstrated that SRP induce cell apoptosis through AMPK activation and STAT3 inhibition in K562 cells. This suggests the possibility of further developing SRP as an alternative treatment option, or perhaps using it as adjuvant chemotherapeutic agent for chronic myeloid leukemia therapy.
authors.affiliation: Zhejiang Provincial Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, Hangzhou, China E-mail : biothcheng@hotmail.com.
authors.forename: Yu-Qing
authors.initials: YQ
authors.lastname: Ge
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Xu
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.forename: Ru-Bin
authors.initials: RB
authors.lastname: Cheng
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D010766:Phosphorylation / Q000187:drug effects; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D065856:Rubus / Q000737:chemistry*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D054832:Urocortins / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D016755:Proto-Oncogene Proteins c-jun; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D012503:Saponins; C426705:UCN2 protein, human; D054832:Urocortins; D003346:Corticotropin-Releasing Hormone; D055372:AMP-Activated Protein Kinases