title: The inhibitor of differentiation isoform Id1b, generated by alternative splicing, maintains cell quiescence and confers self-renewal and cancer stem cell-like properties.
abstract: Id1 has been shown to play a critical role in tumorigenesis and angiogenesis. Moreover, recent reports have involved Id1 in the maintenance of cancer stem cell features in some tumor types. The Id1 gene generates two isoforms through alternative splicing: Id1a and Id1b. We have investigated the role of each isoform in cancer development. Using lentiviral systems we modified the endogenous expression of each of these isoforms in cancer cells and analyzed their biological effect both in vitro and in vivo. Overexpression of Id1b in murine CT26 and 3LL cells caused a G0/G1 cell cycle arrest and reduced proliferation, clonogenicity and phospho-ERK1/2 levels, while increasing p27 levels. High levels of Id1a had an opposite effect and the proportion of cells in the S phase increased significantly. In vivo models confirmed the inhibitory role of Id1b in primary tumor growth and metastasis. Through microarray analysis we found that the cancer stem cell (CSC) markers ALDH1A1 and Notch-1 were up-regulated specifically in Id1b-overexpressing cells. By using qPCR we also found overexpression of Sca-1, Tert, Sox-2 and Oct-4 in these cells. Increased levels of Id1b promoted self-renewal and CSC-like properties, as shown by their high capacity for developing secondary tumorspheres and retaining the PKH26 dye. The acquisition of CSC phenotype was confirmed in human PC-3 cells that overexpressed Id1b. Our results show that Id1b maintains cells in a quiescent state and promotes self-renewal and CSC-like features. On the contrary, Id1a promotes cell proliferation.
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Manrique
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Instituto de Salud Tropical and Department of Microbiology and Parasitology, University of Navarra, Pamplona, Spain.
authors.forename: Paul
authors.initials: P
authors.lastname: Nguewa
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Bleau
authors.affiliation: Gene Therapy and Regulation of Gene Expression Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Estanislao
authors.initials: E
authors.lastname: Nistal-Villan
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.
authors.forename: Ines
authors.initials: I
authors.lastname: Lopez
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Histology and Pathology, University of Navarra, Pamplona, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Villalba
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Oncology, Clinica Universidad de Navarra, Pamplona, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Gil-Bazo
authors.affiliation: Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Histology and Pathology, University of Navarra, Pamplona, Spain. Electronic address: acalvo@unav.es.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Calvo
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D018827:Carcinoma, Lewis Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D051798:Inhibitor of Differentiation Protein 1 / Q000235:genetics* / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D023041:Xenograft Model Antitumor Assays
chemical_list: C497453:ID1 protein, human; D051798:Inhibitor of Differentiation Protein 1; D020033:Protein Isoforms; D012333:RNA, Messenger
keywords: Cancer stem cells; Id1; Metastasis; Quiescence