title: Combined Treatment with Exendin-4 and Metformin Attenuates Prostate Cancer Growth.
abstract: BACKGROUND
  Recently, the pleiotropic benefits of incretin-based therapy have been reported. We have previously reported that Exendin-4, a glucagon-like peptide-1 (GLP-1) receptor agonist, attenuates prostate cancer growth. Metformin is known for its anti-cancer effect. Here, we examined the anti-cancer effect of Exendin-4 and metformin using a prostate cancer model.
  
  
  METHODS
  Prostate cancer cells were treated with Exendin-4 and/or metformin. Cell proliferation was quantified by growth curves and 5-bromo-2'-deoxyuridine (BrdU) assay. TUNEL assay and AMP-activated protein kinase (AMPK) phosphorylation were examined in LNCaP cells. For in vivo experiments, LNCaP cells were transplanted subcutaneously into the flank region of athymic mice, which were then treated with Exendin-4 and/or metformin. TUNEL assay and immunohistochemistry were performed on tumors.
  
  
  RESULTS
  Exendin-4 and metformin additively decreased the growth curve, but not the migration, of prostate cancer cells. The BrdU assay revealed that both Exendin-4 and metformin significantly decreased prostate cancer cell proliferation. Furthermore, metformin, but not Exendin-4, activated AMPK and induced apoptosis in LNCaP cells. The anti-proliferative effect of metformin was abolished by inhibition or knock down of AMPK. In vivo, Exendin-4 and metformin significantly decreased tumor size, and further significant tumor size reduction was observed after combined treatment. Immunohistochemistry on tumors revealed that the P504S and Ki67 expression decreased by Exendin-4 and/or metformin, and that metformin increased phospho-AMPK expression and the apoptotic cell number.
  
  
  CONCLUSIONS
  These data suggest that Exendin-4 and metformin attenuated prostate cancer growth by inhibiting proliferation, and that metformin inhibited proliferation by inducing apoptosis. Combined treatment with Exendin-4 and metformin attenuated prostate cancer growth more than separate treatments.
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tsutsumi
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomiyama
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Kawanami
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Hamaguchi
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Terawaki
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Kunitaka
authors.initials: K
authors.lastname: Murase
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Motonaga
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Makito
authors.initials: M
authors.lastname: Tanabe
authors.affiliation: Department of Endocrinology and Diabetes Mellitus, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yanase
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004359:Drug Therapy, Combination; D000077270:Exenatide; D052216:Glucagon-Like Peptide 1 / Q000819:agonists*; D006801:Humans; D008297:Male; D008687:Metformin / Q000494:pharmacology* / Q000627:therapeutic use; D051379:Mice; D008819:Mice, Nude; D010455:Peptides / Q000494:pharmacology* / Q000627:therapeutic use; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D014688:Venoms / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D010455:Peptides; D014688:Venoms; D052216:Glucagon-Like Peptide 1; D008687:Metformin; D000077270:Exenatide