title: Induction of Akt activity by chemotherapy confers acquired resistance.
abstract: Resistance to chemotherapy is a major cause of treatment failure in human cancer. Accumulating evidence has indicated that the acquisition of resistance to chemotherapeutic drugs involves the activation of the PI3K/Akt pathway. Modulating Akt activity in response to chemotherapy has been observed often in chemoresistant cancers. The potential molecular mechanisms by which chemotherapeutic agents activate the PI3K/Akt pathway are emerging. Activation of this pathway evades the cytotoxic effects of chemotherapeutic agents via regulation of essential cellular functions such as protein synthesis, antiapoptosis, survival and proliferation in cancer. How chemotherapeutic agents induce Akt activation and how activated Akt confers chemoresistance through regulation of signaling networks are discussed in this review. Combining PI3K/Akt inhibitors with standard chemotherapy has been successful in increasing the efficacy of chemotherapeutic agents both in vivo and in vitro. Several small molecules have been developed to specifically target PI3K/Akt and other components of this pathway, which in combination with chemotherapy may be a valid approach to overcome therapeutic resistance. We propose several feedback and feedforward regulatory mechanisms of signaling networks for maintenance of the Akt activity for cell survival. These regulatory mechanisms may limit the efficacy of PI3K/Akt-targeted therapy; therefore, disruption of these mechanisms may be an effective strategy for development of novel anti-cancer therapies.
authors.affiliation: Center for Molecular Medicine and Graduate Institute of Cancer Biology, China Medical University and Hospital, and Department of Biotechnology, Asia University, Taichung, Taiwan. whuang@mail.cmu.edu.tw
authors.forename: Wei-Chien
authors.initials: WC
authors.lastname: Huang
authors.forename: Mien-Chie
authors.initials: MC
authors.lastname: Hung
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects*; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D019869:Phosphatidylinositol 3-Kinases