title: Pim-1 plays a pivotal role in hypoxia-induced chemoresistance.
abstract: Hypoxia changes the responses of cancer cells to many chemotherapy agents, resulting in chemoresistance. The underlying molecular mechanism of hypoxia-induced drug resistance remains unclear. Pim-1 is a survival kinase, which phosphorylates Bad at serine 112 to antagonize drug-induced apoptosis. Here we show that hypoxia increases Pim-1 in a hypoxia-inducible factor-1alpha-independent manner. Inhibition of Pim-1 function by dominant-negative Pim-1 dramatically restores the drug sensitivity to apoptosis induced by chemotherapy under hypoxic conditions in both in vitro and in vivo tumor models. Introduction of siRNAs for Pim-1 also resensitizes cancer cells to chemotherapy drugs under hypoxic conditions, whereas forced overexpression of Pim-1 endows solid tumor cells with resistance to cisplatin, even under normoxia. Dominant-negative Pim-1 prevents a decrease in mitochondrial transmembrane potential in solid tumor cells, which is normally induced by cisplatin (CDDP), followed by the reduced activity of Caspase-3 and Caspase-9, indicating that Pim-1 participates in hypoxia-induced drug resistance through the stabilization of mitochondrial transmembrane potential. Our results demonstrate that Pim-1 is a pivotal regulator involved in hypoxia-induced chemoresistance. Targeting Pim-1 may improve the chemotherapeutic strategy for solid tumors.
authors.affiliation: Division of Cancer-Related Genes, Institute for Genetic Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Darmanin
authors.forename: Y
authors.initials: Y
authors.lastname: Qiao
authors.forename: C
authors.initials: C
authors.lastname: Gully
authors.forename: R
authors.initials: R
authors.lastname: Zhao
authors.forename: S C
authors.initials: SC
authors.lastname: Yeung
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology; D051573:Proto-Oncogene Proteins c-pim-1 / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D000970:Antineoplastic Agents; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051573:Proto-Oncogene Proteins c-pim-1; D002945:Cisplatin