title: Cancer cell-derived clusterin modulates the phosphatidylinositol 3'-kinase-Akt pathway through attenuation of insulin-like growth factor 1 during serum deprivation.
abstract: Cancer cells in their respective microenvironments must endure various growth-constraining stresses. Under these conditions, the cancer cell-derived factors are thought to modulate the signaling pathways between cell growth and dormancy. Here, we describe a cancer cell-derived regulatory system that modulates the phosphatidylinositol 3'-kinase (PI3K)-Akt pathway under serum deprivation stress. Through the use of biochemical purification, we reveal that cancer cell-secreted insulin-like growth factor 1 (IGF-1) and clusterin, an extracellular stress protein, constitute this regulatory system. We show that secreted clusterin associates with IGF-1 and inhibits its binding to the IGF-1 receptor and hence negatively regulates the PI3K-Akt pathway during serum deprivation. This inhibitory function of clusterin appears to prefer IGF-1, as it fails to exert any effects on epidermal growth factor signaling. We demonstrate furthermore that the constitutive activation of oncogenic signaling downstream of IGF-1 confers insensitivity to the inhibitory effects of clusterin. Thus, the interplay between cancer cell-derived clusterin and IGF-1 may dictate the outcome of cell growth and dormancy during tumorigenic progression.
authors.affiliation: Department of Pathology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Hakryul
authors.initials: H
authors.lastname: Jo
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Jia
authors.forename: Kulandayan K
authors.initials: KK
authors.lastname: Subramanian
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hattori
authors.forename: Hongbo R
authors.initials: HR
authors.lastname: Luo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D051152:Clusterin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D016895:Culture Media, Serum-Free; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D015027:Zebrafish
chemical_list: D051152:Clusterin; D016895:Culture Media, Serum-Free; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt