title: A polymethoxyflavone from Laggera pterodonta induces apoptosis in imatinib-resistant K562R cells via activation of the intrinsic apoptosis pathway.
abstract: BACKGROUND
  Treatment with imatinib mesylate (IM) (a tyrosine kinase inhibitor) is the first line of standard care for patients newly diagnosed with CML. Despite the success of IM and other tyrosine kinase inhibitors (TKIs), chronic myeloid leukemia (CML) remains largely incurable, and a number of CML patients die due to Abl mutation-related drug resistance and blast crisis. 3, 5-Dihydroxy-6, 7, 3'4'-tetramethoxyflavone (DHTMF) is a polymethoxyflavone isolated from Laggera pterodonta which is a herbal medicine used to treat cancer in the Chinese folk. In the previous study, we found DHTMF demonstrated good antiproliferative activities against a number of cancer cell lines and induced the apoptosis of CNE cells in vitro in a time- and dose-dependent manner while exhibiting low cytotoxicity in the two normal cell lines Vero and EVC304. The aim of the present study was to evaluate the proliferation inhibition and apoptosis induced by DHTMF alone and in combination with IM in the IM-resistant CML cell line K562R.
  
  
  METHODS
  Cell proliferation was assayed with the cell counting kit-8 (CCK8) method. The apoptosis percentage was determined by flow cytometry (FCM). Mitochondrial transmembrane potential was detected using FCM and confocal laser-scanning microscopy. The level of proteins involved in apoptosis was detected by Western blotting.
  
  
  RESULTS
  DHTMF suppressed K562R cell viability in both time- and dose-dependent manners. DHTMF combined with IM enhanced the inhibitory effects and apoptosis in K562R cells as compared with DHTMF alone. DHTMF alone and in combination with IM significantly decreased the mitochondrial membrane potential and increased the levels of cleaved caspase-9, caspase-7, caspase-3, and PARP in K562R cells.
  
  
  CONCLUSIONS
  We demonstrated that DHTMF could inhibit IM-resistant K562R cell proliferation and induces apoptosis via the intrinsic mitochondrial apoptotic pathway. These results suggest that DHTMF may be a potential therapeutic drug with lower side effects against IM resistance in CML cells.
authors.affiliation: Department of Human Anatomy, Medical School of Jinan University, Guangzhou, 510632 China ; Institute of Hematology, Jinan University, Guangzhou, 510632 China.
authors.forename: Changshu
authors.initials: C
authors.lastname: Cao
authors.affiliation: Institute of Traditional Chinese Medicine & Natural Products, College of Pharmacy, Jinan University, Guangzhou, China.
authors.forename: Bailian
authors.initials: B
authors.lastname: Liu
authors.affiliation: Institute of Hematology, Jinan University, Guangzhou, 510632 China.
authors.forename: Chengwu
authors.initials: C
authors.lastname: Zeng
authors.affiliation: Department of Hematology, the First Affiliated Hospital of Jinan University, Guangzhou, 510632 China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Institute of Hematology, Jinan University, Guangzhou, 510632 China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Chen
authors.affiliation: Institute of Hematology, Jinan University, Guangzhou, 510632 China.
authors.forename: Lijian
authors.initials: L
authors.lastname: Yang
authors.affiliation: Institute of Hematology, Jinan University, Guangzhou, 510632 China.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.affiliation: Institute of Traditional Chinese Medicine & Natural Products, College of Pharmacy, Jinan University, Guangzhou, China.
authors.forename: Yaolan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Hematology, Jinan University, Guangzhou, 510632 China ; Key Laboratory for Regenerative Medicine of Ministry of Education, Jinan University, Guangzhou, 510632 China.
authors.forename: Yangqiu
authors.initials: Y
authors.lastname: Li
keywords: Apoptosis; Cell proliferation; DHTMF; Imatinib-resistant K562 cells