Metformin reduces cisplatin-mediated apoptotic death of cancer cells through AMPK-independent activation of Akt.
Metformin is an antidiabetic drug with anticancer properties, which mainly acts through induction of AMP-activated protein kinase (AMPK). In the present study we investigated the influence of metformin on the in vitro anticancer activity of the well-known chemotherapeutic agent cisplatin. Cell viability was determined by MTT and LDH release assay, oxidative stress and apoptosis (caspase activation, DNA fragmentation, and phosphatidylserine exposure) were assessed by flow cytometry, while activation of AMPK and Akt was analyzed by immunoblotting. Although metformin reduced the number of tumour cells when applied alone, it surprisingly antagonized the cytotoxicity of cisplatin towards U251 human glioma, C6 rat glioma, SHSY5Y human neuroblastoma, L929 mouse fibrosarcoma and HL-60 human leukemia cell lines. Only in B16 mouse melanoma cells metformin augmented the cytotoxicity of cisplatin. In U251 glioma cells metformin suppressed cisplatin-induced apoptotic cell death through inhibition of oxidative stress and caspase activation. The observed cytoprotection was apparently AMPK-independent, as metformin did not further increase cisplatin-induced AMPK activation in U251 cells and other pharmacological AMPK activators failed to block cisplatin-mediated apoptosis. On the other hand, metformin induced Akt activation in cisplatin-treated cells and Akt inhibitor 10-DEBC hydrochloride or phosphoinositide 3-kinase/Akt inhibitor LY294002 abolished metformin-mediated antioxidant and antiapoptotic effects. In conclusion, the antidiabetic drug metformin reduces cisplatin in vitro anticancer activity through AMPK-independent upregulation of Akt survival pathway. These data warrant caution when considering metformin for treatment of diabetic cancer patients receiving cisplatin or as a potential adjuvant in cisplatin-based chemotherapeutic regimens.
Institute of Microbiology and Immunology, University of Belgrade, 11000 Belgrade, Serbia.
Kristina
K
Janjetovic
Ljubica
L
Vucicevic
Maja
M
Misirkic
Urosh
U
Vilimanovich
Gordana
G
Tovilovic
Nevena
N
Zogovic
Zoran
Z
Nikolic
Svetlana
S
Jovanovic
Vladimir
V
Bumbasirevic
Vladimir
V
Trajkovic
Ljubica
L
Harhaji-Trajkovic
D000263:Adenylate Kinase / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D019610:Cytoprotection / Q000187:drug effects; D004336:Drug Antagonism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats
D000970:Antineoplastic Agents; D007004:Hypoglycemic Agents; D008687:Metformin; D051057:Proto-Oncogene Proteins c-akt; D000263:Adenylate Kinase; D020169:Caspases; D002945:Cisplatin