title: Involvement of FKHR-dependent TRADD expression in chemotherapeutic drug-induced apoptosis.
abstract: Chemotherapeutic drugs exhibit their cytotoxic effect by inducing apoptosis in tumor cells. Because the serine/threonine kinase Akt is involved in apoptosis suppression, we investigated the relationship between Akt activity and drug sensitivity. We discovered that certain chemotherapeutic drugs induced apoptosis with caspase activation only when Akt was inactivated after drug treatment, while inactivation of Akt was not observed when tumor cells showed resistance to the drug-induced caspase activation. So, turn-off of the Akt-mediated survival signal is correlated with the sensitivity of the cells to chemotherapy. With a cDNA microarray, we revealed that tumor necrosis factor receptor-associated death domain (tradd) gene expression was elevated in response to Akt inactivation. Reportedly, Forkhead family transcription factors are phosphorylated by Akt, which results in their nuclear exit and inactivation. Analysis of the tradd promoter revealed that it contains at least one potential Forkhead family transcription factor-responsive element, and we confirmed that this element was involved in chemotherapeutic drug-induced TRADD expression. Overexpression of mutant TRADD proteins to block its apoptosis-inducing capability attenuated chemotherapeutic drug-induced apoptosis. Thus, chemotherapeutic drugs exhibited their cytotoxic effects in part by down-regulating Akt signaling following TRADD expression. These results indicate that Akt kinase activity after drug treatment is a hallmark of sensitivity of the cells to chemotherapeutic drugs.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Rokudai
authors.forename: Naoya
authors.initials: N
authors.lastname: Fujita
authors.forename: Osamu
authors.initials: O
authors.lastname: Kitahara
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuruo
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D005786:Gene Expression Regulation; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D047990:TNF Receptor-Associated Factor 1; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000970:Antineoplastic Agents; D020169:Caspases; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins; D047990:TNF Receptor-Associated Factor 1; D014157:Transcription Factors; C085126:FOXO1 protein, human; C494918:AKT1 protein, human