Metformin inhibits growth and enhances radiation response of non-small cell lung cancer (NSCLC) through ATM and AMPK

• Published in: British journal of cancer Vol. 108; no. 10; pp. 2021 - 2032
• Main Authors: Storozhuk, Y, Hopmans, S N, Sanli, T, Barron, C, Tsiani, E, Cutz, J-C, Pond, G, Wright, J, Singh, G, Tsakiridis, T
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28-05-2013; Nature Publishing Group
• Subjects: 631/92/609; 692/699/67/1059/99; 692/699/67/1612/1350; 692/700/565/485; Adenylate Kinase - metabolism; Adenylate Kinase - physiology; Animals; Ataxia Telangiectasia Mutated Proteins; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cancer Research; Carcinoma, Non-Small-Cell Lung - metabolism; Carcinoma, Non-Small-Cell Lung - pathology; Carcinoma, Non-Small-Cell Lung - radiotherapy; Cell Cycle Proteins - metabolism; Cell Cycle Proteins - physiology; Cell Proliferation - drug effects; Cells, Cultured; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; Down-Regulation - drug effects; Drug Resistance; Embryo, Mammalian; Epidemiology; Humans; Lung cancer; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Lung Neoplasms - radiotherapy; Medical sciences; Metformin - pharmacology; Metformin - therapeutic use; Mice; Mice, Inbred BALB C; Mice, Knockout; Mice, Nude; Molecular Medicine; Multiple tumors. Solid tumors. Tumors in childhood (general aspects); Oncology; Pneumology; Protein-Serine-Threonine Kinases - metabolism; Protein-Serine-Threonine Kinases - physiology; Radiation-Sensitizing Agents - pharmacology; Radiation-Sensitizing Agents - therapeutic use; Translational Therapeutics; Tumor Suppressor Proteins - metabolism; Tumor Suppressor Proteins - physiology; Tumors; Tumors of the respiratory system and mediastinum; Xenograft Model Antitumor Assays; H2AX; mTOR; Akt; cell cycle; 4EBP1; Lung disease; Respiratory disease; Growth; Lung cancer; Radiation; Akt protein kinase; Malignant tumor; non-small cell lung carcinoma; cAMP-dependent protein kinase; Hypoglycemic agent; Biguanides; Cancerology; γH2AX; Cell cycle; Mammalian target of rapamycin; Bronchus disease; Inhibitor; Metformin; Cancer; Tumor suppressor gene
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.2013.187

Background:
We examined the potential of metformin (MET) to enhance non-small cell lung cancer (NSCLC) responses to ionising radiation (IR).
Methods:
Human NSCLC cells, mouse embryonic fibroblasts from wild-type and AMP-activated kinase (AMPK)
α
1/2-subunit
−/−
embryos (AMPK
α
1/2
−/−
-MEFs) and NSCLC tumours grafted into Balb/c-nude mice were treated with IR and MET and subjected to proliferation, clonogenic, immunoblotting, cell cycle and apoptosis assays and immunohistochemistry (IHC).
Results:
Metformin (2.5 
μ
M
–5 m
M
) inhibited proliferation and radio-sensitised NSCLC cells. Metformin (i) activated the ataxia telengiectasia-mutated (ATM)–AMPK–p53/p21
cip1
and inhibited the Akt–mammalian target of rapamycin (mTOR)–eIF4E-binding protein 1 (4EBP1) pathways, (ii) induced G1 cycle arrest and (iii) enhanced apoptosis. ATM inhibition blocked MET and IR activation of AMPK. Non-small cell lung cancer cells with inhibited AMPK and AMPK
α
1/2
−/−
-MEFs were resistant to the antiproliferative effects of MET and IR. Metformin or IR inhibited xenograft growth and combined treatment enhanced it further than each treatment alone. Ionising radiation and MET induced (i) sustained activation of ATM–AMPK–p53/p21
cip1
and inhibition of Akt–mTOR–4EBP1 pathways in tumours, (ii) reduced expression of angiogenesis and (iii) enhanced expression of apoptosis markers.
Conclusion:
Clinically achievable MET doses inhibit NSCLC cell and tumour growth and sensitise them to IR. Metformin and IR mediate their action through an ATM–AMPK-dependent pathway. Our results suggest that MET can be a clinically useful adjunct to radiotherapy in NSCLC.