Extracellular ATP induces the inactivation of FoxO transcription factors and cell cycle progression of MCF-7 cells

SCODELARO BILBAO, PAOLA GABRIELA; BOLAND, RICARDO

San Diego

Congreso; American Society for Biochemistry and Molecular Biology Annual Meeting; 2012

American Society for Biochemistry and Molecular Biology

Forkhead box-O (FoxO) transcription factors play an importantrole in tumour suppression by regulating the expression of genesinvolved in DNA damage repair, apoptosis and cell cycle arrest.We studied the role of extracellular ATP in the modulation ofFoxO transcription factors and of cell cycle progression in MCF-7breast cancer cells. Western blot analysis showed that 5 μM ATPinduced the phosphorylation of FoxO1/3a at threonine 24/32, andalso reduced the expression of FoxO1. The use of thephosphatidilinositol 3 kinase (PI3K) inhibitor Ly294002 and ofsiRNA to reduce the expression of the serine/threonine kinase Aktshowed that these effects are mediated by the PI3K/Akt signalingpathway. Immunocytochemistry and subcellular fractionationstudies showed that ATP induces the translocation of FoxO3a fromthe nucleus to the cytoplasm. Flow cytometry analysis revealedthat ATP increases the number of cells in the S phase of cell cycle.In addition, analysis by Western blot showed that ATP increasesthe expression of the cyclins D1 and D3 and diminishes theinhibitory proteins p21Cip1 and p27Kip1. However, these effectswere independent of the PI3K/Akt pathway. Taken together, ourresults suggest that ATP induces the inactivation of FoxOtranscription factors in a PI3K dependent manner and also induceschanges in the expression of proteins involved in cell cycleregulation in MCF-7 cells.