PURPOSE: FOXO1(FKHR), one of the Forkhead family of transcription factors, is involved in pro-apoptotic signaling. Phosphorylated Akt/PKB leads to the inhibition of FOXO1 activity by phosphorylation and cytoplasmic sequestration. In this study, we examined the role of FOXO1 in apoptosis of non-small cell lung cancer (NSCLC) cells.
METHODS: Localization of FOXO1 was examined by fluorescent immunohistochemistry on three different NSCLC cell lines (A549, EBC1,and PC3). Akt/PKB was knocked down by the RNA interference method to examine the relationship between Akt/PKB expression and FOXO1 status. Furthermore, TUNEL staining was performed to identify the induction of apoptosis in these cells.
RESULTS: FOXO1 was sequestered from the nucleus in all three cell lines cultured with fetal bovine serum (FBS), while without FBS, nuclear inclusion of FOXO1 was observed. Inhibition of Akt/PKB resulted in the accumulation of FOXO1 in the nucleus of A549 and EBC1, in which, induction of apoptosis was accelerated.
CONCLUSION: FOXO1 is constitutively present in the cytoplasm in NSCLC cells, and inhibition of Akt/PKB induces its translocation to the nucleus, leading to apoptosis.
CLINICAL IMPLICATIONS: Further investigations could yield novel molecular targeted treatment strategies for non-small cell lung cancer aimed at inhibiting the Akt/PKB-FOXO1 signaling pathway.
DISCLOSURE: Takayo Maekawa, None.