Runx2 activates PI3K/Akt signaling via mTORC2 regulation in invasive breast cancer cells.
BACKGROUND
The Runt-related transcription factor Runx2 is critical for skeletal development but is also aberrantly expressed in breast cancers, and promotes cell growth and invasion. A de-regulated serine/threonine kinase Akt signaling pathway is implicated in mammary carcinogenesis and cell survival; however, the mechanisms underlying Runx2 role in survival of invasive breast cancer cells are still unclear.


METHODS
The phenotypic analysis of Runx2 function in cell survival was performed by gene silencing and flow cytometric analysis in highly invasive MDA-MB-231 and SUM-159-PT mammary epithelial cell lines. The expression analysis of Runx2 and pAkt (serine 473) proteins in metastatic breast cancer specimens was performed by immunohistochemistry. The mRNA and protein levels of kinases and phosphatases functional in Akt signaling were determined by real-time PCR and Western blotting, while DNA-protein interaction was studied by chromatin immunoprecipitation assays.


RESULTS
The high Runx2 levels in invasive mammary epithelial cell lines promoted cell survival in Akt phosphorylation (pAkt-serine 473) dependent manner. The analysis of kinases and phosphatases associated with pAkt regulation revealed that Runx2 promotes pAkt levels via mammalian target of rapamycin complex-2 (mTORC2). The recruitment of Runx2 on mTOR promoter coupled with Runx2-dependent expression of mTORC2 component Rictor defined Runx2 function in pAkt-mediated survival of invasive breast cancer cells.


CONCLUSIONS
Our results identified a novel mechanism of Runx2 regulatory crosstalk in Akt signaling that could have important consequences in targeting invasive breast cancer-associated cell survival.
Manish
M
Tandon
Zujian
Z
Chen
Jitesh
J
Pratap
D017209:Apoptosis / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics; D002867:Chromones / Q000494:pharmacology; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D000076225:Mechanistic Target of Rapamycin Complex 2; D009025:Morpholines / Q000494:pharmacology; D046912:Multiprotein Complexes / Q000096:biosynthesis*; D009361:Neoplasm Invasiveness / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010749:Phosphoprotein Phosphatases / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases / Q000096:biosynthesis*
D002867:Chromones; D050659:Core Binding Factor Alpha 1 Subunit; D009025:Morpholines; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; C493709:RUNX2 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D058539:Phosphatidylinositol 3-Kinase; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C400601:PHLPP1 protein, human; D010749:Phosphoprotein Phosphatases