Another surprise from Metformin: novel mechanism of action via K-Ras influences endometrial cancer response to therapy.
Metformin is an oral biguanide commonly used for the treatment of type II diabetes and has recently been demonstrated to possess antiproliferative properties that can be exploited for the prevention and treatment of a variety of cancers. The mechanisms underlying this effect have not been fully elucidated. Using both in vitro and in vivo models, we examined the effects of metformin on endometrial tumors with defined aberrations in the PI3K/PTEN/mTOR and MAPK signaling pathways to understand metformin mechanism of action and identify clinically useful predictors of response to this agent. In vitro assays of proliferation, cytotoxicity, and apoptosis were used to quantify the effects of metformin on endometrial cancer cell lines with mutations in the PI3K/PTEN/mTOR and MAPK signaling pathways. The in vivo effects of oral metformin on tumor progression were further examined using xenograft mouse models of endometrial cancer. K-Ras localization was analyzed by confocal microscopy using GFP-labeled oncogenic K-Ras and by immunoblot following subcellular fractionation. Metformin inhibited cell proliferation, induced apoptosis, and decreased tumor growth in preclinical endometrial cancer models, with the greatest response observed in cells harboring activating mutations in K-Ras. Furthermore, metformin displaces constitutively active K-Ras from the cell membrane, causing uncoupling of the MAPK signaling pathway. These studies provide a rationale for clinical trials using metformin in combination with PI3K-targeted agents for tumors harboring activating K-Ras mutations, and reveal a novel mechanism of action for metformin.
Corresponding Author: Karen H. Lu, Department of Gynecologic Oncology and Reproductive Medicine, 1155 Hermann Pressler Dr., Unit 1362, Houston, TX 77030. khlu@mdanderson.org.
David A
DA
Iglesias
Melinda S
MS
Yates
Dharini
D
van der Hoeven
Travis L
TL
Rodkey
Qian
Q
Zhang
Ngai Na
NN
Co
Jennifer
J
Burzawa
Sravanthi
S
Chigurupati
Joseph
J
Celestino
Jessica
J
Bowser
Russell
R
Broaddus
John F
JF
Hancock
Rosemarie
R
Schmandt
Karen H
KH
Lu
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016889:Endometrial Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D009154:Mutation; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D015398:Signal Transduction / Q000187:drug effects; D047368:Tumor Burden / Q000187:drug effects / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D000970:Antineoplastic Agents; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D008687:Metformin; D011493:Protein Kinase C; D051059:PTEN Phosphohydrolase; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins