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¹ Committee on Cancer Biology, University of Chicago, Chicago, Illinois and ² Department of Oncology, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Johns Hopkins University, Baltimore, Maryland

Requests for reprints: Charles M. Rudin, Department of Oncology, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Johns Hopkins University, Bunting Blaustein Cancer Research Building, Room 344, 1650 Orleans Street, Baltimore, MD 21231. Phone: 410-955-8904; Fax: 410-502-0677. E-mail: rudin{at}jhmi.edu

Chemotherapeutic agents induce apoptosis in cancer cells through effects on multiple intracellular targets. Recent observations suggest that a consistent cellular response to chemotherapeutic agents of disparate classes is down-regulation of glycolytic metabolism. Inhibition of glycolytic activity has been linked to apoptotic induction in several models. The serine/threonine kinase Akt (protein kinase B) promotes both glycolytic metabolism and survival, and these functions have been shown to be linked. Because of its key role in both glycolysis and survival, we examined the function of Akt in the cellular response to cytotoxic agents. Following exposure to any of several chemotherapeutic agents, an initial up-regulation in endogenous Akt activity is rapidly suppressed. Using cells containing constitutively active myristoylated Akt, dominant-negative kinase-dead Akt, or an empty vector control, we show here that Akt activation markedly increases resistance to microtubule-directed agents, including vincristine, colchicine, and paclitaxel. Akt also maintains increased glycolytic rate in response to antimicrotubule treatment. Rapamycin inhibits Akt-mediated maintenance of glycolysis and therapeutic resistance, indicating that these effects are dependent on mammalian target of rapamycin (mTOR). Furthermore, an activated mTOR mutant confers resistance to antimicrotubule agents. Taken together, these observations suggest that activation of the Akt-mTOR signaling pathway can augment glucose utilization and promote resistance to chemotherapeutic agents that do not directly target metabolic regulation. These data provide insight into potentially synergistic combinations of anticancer therapies.

Key Words: apoptosis • chemotherapy • glycolysis • vincristine • Akt

Grant support: NIH grant K08 CA81134 (C.M. Rudin).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to 1indicate this fact.

Received 7/22/04; revised 9/14/04; accepted 10/ 7/04.