title: Inhibitory effects of metformin at low concentration on epithelial-mesenchymal transition of CD44(+)CD117(+) ovarian cancer stem cells.
abstract: BACKGROUND
  Although metformin, a first-line drug for treating diabetes, may play an important role in inhibition of epithelial ovarian cancer cell growth and cancer stem cells (CSCs), metformin at low dose showed less effect on the proliferation of ovarian cancer cells. In this study, we evaluated the effect of metformin at low dose on ovarian CSCs in order to understand the molecular mechanisms underlying.
  
  
  METHODS
  The inhibitory effects of metformin at los dose on proliferation and population of ovarian cancer cells including SKOV3 and A2780 were assessed by cell proliferation assay and flow cytometry. Quantitative real-time PCR assay on expression of Bcl-2, Survivin and Bax was performed to determine the effect of metformin at low dose on epithelial-mesenchymal transition (EMT) of cancer cells and CSCs. Tumor sphere formation assay was also performed to evaluate the effect of metformin on spheres forming ability of CSCs. The therapeutic efficacy and the anti-CSC effects of metformin at low dose were investigated by using both SKOV3 cells and primary tumor xenografts. In addition, the CSC frequency and EMT in tumor xenograft models were also assessed by flow cytometry and quantitative real-time PCR.
  
  
  RESULTS
  Metformin at low dose did not affect the proliferation of ovarian cancer cells. However, it inhibited population of CD44(+)CD117(+) selectively, neither CD133(+) nor ALDH(+) cells. It suppressed expression of snail2, twist and vimentin significantly in cancer cells and CD44(+)CD117(+) CSCs in vitro. Low dose of metformin reduced survivin expression in CSCs. Low concentrations of metformin inhibited the secondary and the tertiary tumor sphere formation, decreased SKOV3 and primary ovarian tumor xenograft growth, enhanced the anticancer effect of cisplatin, and lowered the proportion of CD44(+)CD117(+) CSCs in the xenograft tissue. Metformin was also associated with a reduction of snail2, twist, and vimentin in CD44(+)CD117(+) ovarian CSCs in vivo.
  
  
  CONCLUSIONS
  Our results implicate that metformin at low dose inhibits selectively CD44(+)CD117(+) ovarian CSCs through inhibition of EMT and potentiates the effect of cisplatin.
authors.affiliation: Department of Gynecology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200092, China. rrzhangcn@126.com.
authors.forename: Rongrong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Gynecology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200092, China. pingzhang_xhyy@126.com.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Gynecology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200092, China. hongwang_xhyy@163.com.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Otolaryngology & Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200092, China. hdm1968@hotmail.com.
authors.forename: Dongming
authors.initials: D
authors.lastname: Hou
authors.affiliation: Department of Interventional Radiology, Cancer Hospital, Fudan University, Shanghai, 200032, China. liwentao98@126.com.
authors.forename: Wentao
authors.initials: W
authors.lastname: Li
authors.affiliation: School of Pharmaceutical Science and Technology, Dalian University of Technology, Dalian, 116024, China. gxiao@dlut.edu.cn.
authors.forename: Guishan
authors.initials: G
authors.lastname: Xiao
authors.affiliation: Sunstem Biotechnology Co., Ltd, Shanghai, 200439, China. sunstem1@163.com.
authors.forename: Chenwei
authors.initials: C
authors.lastname: Li
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D005260:Female; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D016688:Mice, Inbred NOD; D008819:Mice, Nude; D016513:Mice, SCID; D014411:Neoplastic Stem Cells / Q000166:cytology / Q000378:metabolism* / Q000637:transplantation; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D000071250:Snail Family Transcription Factors; D000077022:Survivin; D014157:Transcription Factors / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D018960:Hyaluronan Receptors; D051034:Inhibitor of Apoptosis Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C000604407:SNAI1 protein, human; C000604429:Snai1 protein, mouse; D000071250:Snail Family Transcription Factors; D000077022:Survivin; D014157:Transcription Factors; D014746:Vimentin; D051028:bcl-2-Associated X Protein; D008687:Metformin; D019009:Proto-Oncogene Proteins c-kit; D002945:Cisplatin