title: Hyaluronan-CD44 interaction with protein kinase C(epsilon) promotes oncogenic signaling by the stem cell marker Nanog and the Production of microRNA-21, leading to down-regulation of the tumor suppressor protein PDCD4, anti-apoptosis, and chemotherapy resistance in breast tumor cells.
abstract: Multidrug resistance and disease relapse is a challenging clinical problem in the treatment of breast cancer. In this study, we investigated the hyaluronan (HA)-induced interaction between CD44 (a primary HA receptor) and protein kinase Cepsilon (PKCepsilon), which regulates a number of human breast tumor cell functions. Our results indicate that HA binding to CD44 promotes PKCepsilon activation, which, in turn, increases the phosphorylation of the stem cell marker, Nanog, in the breast tumor cell line MCF-7. Phosphorylated Nanog is then translocated from the cytosol to the nucleus and becomes associated with RNase III DROSHA and the RNA helicase p68. This process leads to microRNA-21 (miR-21) production and a tumor suppressor protein (e.g. PDCD4 (program cell death 4)) reduction. All of these events contribute to up-regulation of inhibitors of apoptosis proteins (IAPs) and MDR1 (multidrug-resistant protein), resulting in anti-apoptosis and chemotherapy resistance. Transfection of MCF-7 cells with PKCepsilon or Nanog-specific small interfering RNAs effectively blocks HA-mediated PKCepsilon-Nanog signaling events, abrogates miR-21 production, and increases PDCD4 expression/eIF4A binding. Subsequently, this PKCepsilon-Nanog signaling inhibition causes IAP/MDR1 down-regulation, apoptosis, and chemosensitivity. To further evaluate the role of miR-21 in oncogenesis and chemoresistance, MCF-7 cells were also transfected with a specific anti-miR-21 inhibitor in order to silence miR-21 expression and inhibit its target functions. Our results indicate that anti-miR-21 inhibitor not only enhances PDCD4 expression/eIF4A binding but also blocks HA-CD44-mediated tumor cell behaviors. Thus, this newly discovered HA-CD44 signaling pathway should provide important drug targets for sensitizing tumor cell apoptosis and overcoming chemotherapy resistance in breast cancer cells.
authors.affiliation: Endocrine Unit, Department of Medicine, University of California at San Francisco, and Veterans Affairs Medical Center, San Francisco, California 94121, USA. lilly.bourguignon@ucsf.edu
authors.forename: Lilly Y W
authors.initials: LY
authors.lastname: Bourguignon
authors.forename: Christina C
authors.initials: CC
authors.lastname: Spevak
authors.forename: Gabriel
authors.initials: G
authors.lastname: Wong
authors.forename: Weiliang
authors.initials: W
authors.lastname: Xia
authors.forename: Eli
authors.initials: E
authors.lastname: Gilad
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D015152:Blotting, Northern; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005455:Fluorescent Antibody Technique; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D000071317:Nanog Homeobox Protein; D010766:Phosphorylation; D011485:Protein Binding; D051744:Protein Kinase C-epsilon / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D018398:Homeodomain Proteins; D018960:Hyaluronan Receptors; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; C114487:PDCD4 protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D006820:Hyaluronic Acid; D051744:Protein Kinase C-epsilon; C517918:DROSHA protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases