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Research Articles: Therapeutics

Synergistic induction of apoptosis in human leukemia T cells by the Akt inhibitor perifosine and etoposide through activation of intrinsic and Fas-mediated extrinsic cell death pathways

¹ Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia, Cell Signalling Laboratory, Università di Bologna; ² Istituto per i Trapianti d'Organo e l'Immunocitologia del Consiglio Nazionale delle Ricerche, Sezione di Bologna c/o Instituto Ortopedico Rizzoli, Bologna, Italy; and ³ Dipartimento di Scienze Motorie e della Salute, Sezione di Anatomia, Università di Cassino, Cassino, Italy

Requests for reprints: Alberto M. Martelli, Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Università di Bologna, via Irnerio 48, 40126 Bologna, Italy. Phone: 39-512091580; Fax: 39-512091695. E-mail: amartell{at}biocfarm.unibo.it

Perifosine is an Akt inhibitor displaying strong antineoplastic effects in human tumor cell lines and is currently being tested in phase II clinical trials for treatment of major human cancers. Several recent studies showed the apoptotic effect of perifosine alone or in combination with other anticancer agents. However, this is the first study describing the effects of combining perifosine with the commonly used chemotherapy drug etoposide in cultured human Jurkat T-leukemia cells. Low concentrations of perifosine (5 µmol/L) induced cell death in a synergistic fashion with etoposide if used simultaneously or immediately following exposure to etoposide (posttreatment). The increase in cell death seems to be due to an inactivation of the Akt survival pathway, where treated cells showed a complete dephosphorylation of Akt. Moreover, combined drug-induced Akt deactivation was associated with a parallel decrease in phosphorylation of FoxO1 transcription factor and in expression of antiapoptotic Bcl-xL. Furthermore, the increase in cell death was associated with a specific activation of the caspase-dependent Fas death receptor pathway. These findings might be useful when designing clinical trials where chemotherapy is combined with perifosine for a potential broad use against hematologic malignancies in which the Akt survival pathway is frequently activated. [Mol Cancer Ther 2006;5(6):1559–70]

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Received 2/ 9/06; revised 4/ 5/06; accepted 4/21/06.