title: Honokiol inhibits sphere formation and xenograft growth of oral cancer side population cells accompanied with JAK/STAT signaling pathway suppression and apoptosis induction.
abstract: BACKGROUND
  Eliminating cancer stem cells (CSCs) has been suggested for prevention of tumor recurrence and metastasis. Honokiol, an active compound of Magnolia officinalis, had been proposed to be a potential candidate drug for cancer treatment. We explored its effects on the elimination of oral CSCs both in vitro and in vivo.
  
  
  METHODS
  By using the Hoechst side population (SP) technique, CSCs-like SP cells were isolated from human oral squamous cell carcinoma (OSCC) cell lines, SAS and OECM-1. Effects of honokiol on the apoptosis and signaling pathways of SP-derived spheres were examined by Annexin V/Propidium iodide staining and Western blotting, respectively. The in vivo effectiveness was examined by xenograft mouse model and immunohistochemical tissue staining.
  
  
  RESULTS
  The SP cells possessed higher stemness marker expression (ABCG2, Ep-CAM, Oct-4 and Nestin), clonogenicity, sphere formation capacity as well as tumorigenicity when compared to the parental cells. Treatment of these SP-derived spheres with honokiol resulted in apoptosis induction via Bax/Bcl-2 and caspase-3-dependent pathway. This apoptosis induction was associated with marked suppression of JAK2/STAT3, Akt and Erk signaling pathways in honokiol-treated SAS spheres. Consistent with its effect on JAK2/STAT3 suppression, honokiol also markedly inhibited IL-6-mediated migration of SAS cells. Accordingly, honokiol dose-dependently inhibited the growth of SAS SP xenograft and markedly reduced the immunohistochemical staining of PCNA and endothelial marker CD31 in the xenograft tumor.
  
  
  CONCLUSIONS
  Honokiol suppressed the sphere formation and xenograft growth of oral CSC-like cells in association with apoptosis induction and inhibition of survival/proliferation signaling pathways as well as angiogenesis. These results suggest its potential as an integrative medicine for combating oral cancer through targeting on CSCs.
authors.affiliation: Comprehensive Cancer Center, Taipei Medical University, Taipei, Taiwan.|Cancer Center, Wan Fang Hospital, Taipei Medical University, No.111, Section 3, Hsing-Long Road, Taipei, 116, Taiwan.
authors.forename: Jhy-Shrian
authors.initials: JS
authors.lastname: Huang
authors.affiliation: Comprehensive Cancer Center, Taipei Medical University, Taipei, Taiwan.|Cancer Center, Wan Fang Hospital, Taipei Medical University, No.111, Section 3, Hsing-Long Road, Taipei, 116, Taiwan.|Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, No.250, Wuxing Street, Taipei, 110, Taiwan.
authors.forename: Chih-Jung
authors.initials: CJ
authors.lastname: Yao
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan.
authors.forename: Shuang-En
authors.initials: SE
authors.lastname: Chuang
authors.affiliation: Department of Surgery, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chi-Tai
authors.initials: CT
authors.lastname: Yeh
authors.affiliation: Department of Urology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Liang-Ming
authors.initials: LM
authors.lastname: Lee
authors.affiliation: Comprehensive Cancer Center, Taipei Medical University, Taipei, Taiwan.|Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Ruei-Ming
authors.initials: RM
authors.lastname: Chen
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan.
authors.forename: Wan-Ju
authors.initials: WJ
authors.lastname: Chao
authors.affiliation: Comprehensive Cancer Center, Taipei Medical University, Taipei, Taiwan.|Cancer Center, Wan Fang Hospital, Taipei Medical University, No.111, Section 3, Hsing-Long Road, Taipei, 116, Taiwan.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Whang-Peng
authors.affiliation: Comprehensive Cancer Center, Taipei Medical University, Taipei, Taiwan. gminlai@nhri.org.tw.|Cancer Center, Wan Fang Hospital, Taipei Medical University, No.111, Section 3, Hsing-Long Road, Taipei, 116, Taiwan. gminlai@nhri.org.tw.|Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, No.250, Wuxing Street, Taipei, 110, Taiwan. gminlai@nhri.org.tw.|National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan. gminlai@nhri.org.tw.
authors.forename: Gi-Ming
authors.initials: GM
authors.lastname: Lai
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects; D001713:Biphenyl Compounds / Q000008:administration & dosage*; D049109:Cell Proliferation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D053612:Janus Kinases / Q000096:biosynthesis; D017705:Lignans / Q000008:administration & dosage*; D051379:Mice; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000473:pathology; D050791:STAT Transcription Factors / Q000096:biosynthesis; D058985:Side-Population Cells / Q000187:drug effects / Q000473:pathology; D023041:Xenograft Model Antitumor Assays; D000498:Allyl Compounds; D010636:Phenols
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D001713:Biphenyl Compounds; D053612:Janus Kinases; D017705:Lignans; D009363:Neoplasm Proteins; D050791:STAT Transcription Factors; C005499:honokiol; D000498:Allyl Compounds; D010636:Phenols
keywords: Cancer stem-like side population; Honokiol; JAK2/STAT3 pathway; Oral cancer