title: FOXO proteins regulate tumor necrosis factor-related apoptosis inducing ligand expression. Implications for PTEN mutation in prostate cancer.
abstract: Mutations in PTEN occur in 60-80% of prostate cancers and lead to a constitutive activation of the phosphatidylinositol 3-kinase pathway and a resultant loss of activity of the FOXO family of forkhead transcription factors FKHRL1 and FKHR. To provide insight into the role of PTEN mutations in prostate cancer, we used microarrays to identify genes regulated by FKHRL1 and FKHR in LAPC4 prostate carcinoma cells. These studies revealed that adenoviral overexpression of FKHRL1 and FKHR in the LAPC4 prostate cancer cell line resulted in apoptosis and induced the expression of many genes that affect cellular proliferation or survival. The expression of one of these FOXO-regulated genes, TRAIL, a pro-apoptotic member of the tumor necrosis factor family, was decreased in human metastatic prostate tumors. The altered expression of TRAIL in these tumors correlated directly with decreased PTEN expression and the resultant loss of FKHRL1 and FKHR activity. Analysis of the effects of FOXO proteins on the TRAIL promoter localized the FKHRL1 responsive element of the TRAIL promoter to nucleotides -138 to -121 and demonstrated that TRAIL is a direct target of FKHRL1. These findings suggest that the decreased activity of FKHRL1 and FKHR in prostate cancers resulting from loss of PTEN leads to a decrease in TRAIL expression that may contribute to increased survival of the tumor cells.
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001665:Binding Sites; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D009154:Mutation; D009362:Neoplasm Metastasis; D020411:Oligonucleotide Array Sequence Analysis; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D004268:DNA-Binding Proteins; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D008024:Ligands; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D025521:Tumor Suppressor Proteins; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human