title: Effects of metformin on retinoblastoma growth in vitro and in vivo.
abstract: Recent studies suggest that the anti-diabetic drug metformin may reduce the risk of cancer and have anti-proliferative effects for some but not all cancers. In this study, we examined the effects of metformin on human retinoblastoma cell proliferation in vitro and in vivo. Two different human retinoblastoma cell lines (Y79, WERI) were treated with metformin in vitro and xenografts of Y79 cells were established in nu/nu immune-deficient mice and used to assess the effects of pharmacological levels of metformin in vivo. Metformin inhibited proliferation of the retinoblastoma cells in vitro. Similar to other studies, high concentrations of metformin (mM) blocked the cell cycle in G0‑G1, indicated by a strong decrease of G1 cyclins, especially cyclin D, cyclin-dependent kinases (4 and 6), and flow cytometry assessment of the cell cycle. This was associated with activation of AMPK, inhibition of the mTOR pathways and autophagy marker LC3B. However, metformin failed to suppress growth of xenografted tumors of Y79 human retinoblastoma cells in nu/nu mice, even when treated with a maximally tolerated dose level achieved in human patients. In conclusion, suprapharmacological levels (mM) of metformin, well above those tolerated in vivo, inhibited the proliferation of retinoblastoma cells in vitro. However, physiological levels of metformin, such as seen in the clinical setting, did not affect the growth of retinoblastoma cells in vitro or in vivo. This suggests that the potential beneficial effects of metformin seen in epidemiological studies may be limited to specific tumor types or be related to indirect effects/mechanisms not observed under acute laboratory conditions.
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Brodowska
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Sofia
authors.initials: S
authors.lastname: Theodoropoulou
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Meyer Zu Hörste
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Eleftherios I
authors.initials: EI
authors.lastname: Paschalis
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Kimio
authors.initials: K
authors.lastname: Takeuchi
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Gordon
authors.initials: G
authors.lastname: Scott
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Ramsey
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kiernan
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Mien
authors.initials: M
authors.lastname: Hoang
authors.affiliation: Department of Immunology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Cichy
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Joan W
authors.initials: JW
authors.lastname: Miller
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Evangelos S
authors.initials: ES
authors.lastname: Gragoudas
authors.affiliation: Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
authors.forename: Demetrios G
authors.initials: DG
authors.lastname: Vavvas
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000096:biosynthesis; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008687:Metformin / Q000008:administration & dosage*; D051379:Mice; D012175:Retinoblastoma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D058570:TOR Serine-Threonine Kinases / Q000096:biosynthesis; D023041:Xenograft Model Antitumor Assays
chemical_list: D008687:Metformin; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases