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. 2017 Nov 1;51(4):431-437.
doi: 10.1515/raon-2017-0042. eCollection 2017 Dec.

Metformin Enhanced in Vitro Radiosensitivity Associates with G2/M Cell Cycle Arrest and Elevated Adenosine-5'-monophosphate-activated Protein Kinase Levels in Glioblastoma

Sebastian Adeberg  1   2   3   4 , Denise Bernhardt  1   3   4 , Semi B Harrabi  1   3   4 , Nils H Nicolay  1   2   3   4 , Juliane Hörner-Rieber  1   3   4 , Laila König  1   3   4 , Michael Repka  5 , Angela Mohr  1   3   4 , Amir Abdollahi  1   3   4   6 , Klaus-Josef Weber  1   4 , Juergen Debus  1   2   3   4 , Stefan Rieken  1   3   4
Affiliations

Metformin Enhanced in Vitro Radiosensitivity Associates with G2/M Cell Cycle Arrest and Elevated Adenosine-5'-monophosphate-activated Protein Kinase Levels in Glioblastoma

Sebastian Adeberg et al. Radiol Oncol. .

Abstract

Background: It is hypothesized that metabolism plays a strong role in cancer cell regulation. We have recently demonstrated improved progression-free survival in patients with glioblastoma who received metformin as an antidiabetic substance during chemoradiation. Although metformin is well-established in clinical use the influence of metformin in glioblastoma is far from being understood especially in combination with other treatment modalities such as radiation and temozolomide.

Materials and methods: In this study, we examined the influence of metformin in combinations with radiation and temozolomide on cell survival (clonogenic survival), cell cycle (routine flow cytometric analysis, FACScan), and phosphorylated Adenosine-5'-monophosphate-activated protein kinase (AMPK) (Phopho-AMPKalpha1 - ELISA) levels in glioblastoma cell lines LN18 and LN229.

Results: Metformin and temozolomide enhanced the effectiveness of photon irradiation in glioblastoma cells. Cell toxicity was more pronounced in O6-methylguanine DNA methyltransferase (MGMT) promoter non-methylated LN18 cells. Induction of a G2/M phase cell cycle block through metformin and combined treatments was observed up to 72 h. These findings were associated with elevated levels of activated AMPK levels in LN229 cells but not in LN18 cells after irradiation, metformin, and temozolomide treatment.

Conclusions: Radiosensitizing effects of metformin on glioblastoma cells treated with irradiation and temozolomide in vitro coincided with G2/M arrest and changes in pAMPK levels.

Keywords: cell cycle; gliomas; glycolysis; metabolism; metformin; proliferation.

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Conflict of interest statement

Disclosure: No potential conflicts of interest were disclosed.

Figures

Figure 1
Figure 1
(A,B) Clonogenic survival assays of LN229 and LN18 glioblastoma cell lines after treatment with photon irradiation. (C,D) Clonogenic survival assays after comparing LN229 and LN18 cell lines after combined treatment with TMZ (C) or metformin (D). Error bars represent standard deviations. * shows a statistical significance (P <0.05). In LN229 enhanced cell kill was observed by TMZ and in LN18 cells lines metformin treatment resulted in increased cell toxicity compared to the control, as well as the combination of both agents itself. Combined bimodal and trimodal treatment results in superior cell toxicity.
Figure 2
Figure 2
(A) In LN229 pAMPK measurements were significantly increased after treatment with Metformin, 2 Gy and temozolomide and 6 Gy combined with Metformin compared to the control if not otherwise specified (* p<0.05). (B) No significant increase of pAMPK levels were observed in cell line LN18. Error bars represent standard deviation.
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