title: SIRT1-mediated downregulation of p27Kip1 is essential for overcoming contact inhibition of Kaposi's sarcoma-associated herpesvirus transformed cells.
abstract: Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus associated with Kaposi's sarcoma (KS), a malignancy commonly found in AIDS patients. Despite intensive studies in the last two decades, the mechanism of KSHV-induced cellular transformation and tumorigenesis remains unclear. In this study, we found that the expression of SIRT1, a metabolic sensor, was upregulated in a variety of KSHV-infected cells. In a model of KSHV-induced cellular transformation, SIRT1 knockdown with shRNAs or knockout by CRISPR/Cas9 gene editing dramatically suppressed cell proliferation and colony formation in soft agar of KSHV-transformed cells by inducing cell cycle arrest and contact inhibition. SIRT1 knockdown or knockout induced the expression of cyclin-dependent kinase inhibitor 1B (p27Kip1). Consequently, p27 knockdown rescued the inhibitory effect of SIRT1 knockdown or knockout on cell proliferation and colony formation. Furthermore, treatment of KSHV-transformed cells with a SIRT1 inhibitor, nicotinamide (NAM), had the same effect as SIRT1 knockdown and knockout. NAM significantly inhibited cell proliferation in culture and colony formation in soft agar, and induced cell cycle arrest. Significantly, NAM inhibited the progression of tumors and extended the survival of mice in a KSHV-induced tumor model. Collectively, these results demonstrate that SIRT1 suppression of p27 is required for KSHV-induced tumorigenesis and identify a potential therapeutic target for KS.
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Meilan
authors.initials: M
authors.lastname: He
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Hongfeng
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Tan
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Bai
authors.affiliation: Center for Genome Engineering, Institute for Basic Science, Seoul, South Korea.|Department of Chemistry, Seoul National University, Seoul, South Korea.
authors.forename: Heon Seok
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Center for Genome Engineering, Institute for Basic Science, Seoul, South Korea.|Present address: Department of Chemistry, Hanyang University, Seoul, South Korea.
authors.forename: Sangsu
authors.initials: S
authors.lastname: Bae
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Lu
authors.initials: L
authors.lastname: Che
authors.affiliation: Center for Genome Engineering, Institute for Basic Science, Seoul, South Korea.|Department of Chemistry, Seoul National University, Seoul, South Korea.
authors.forename: Jin-Soo
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, CA, USA.
authors.forename: Shou-Jiang
authors.initials: SJ
authors.lastname: Gao
mesh_terms: D002461:Cell Line, Transformed; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D003260:Contact Inhibition / Q000235:genetics*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D055786:Gene Knockout Techniques; D019288:Herpesvirus 8, Human / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D012514:Sarcoma, Kaposi / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050760:Cyclin-Dependent Kinase Inhibitor p27; D056564:Sirtuin 1
keywords: SIRT1; cellular transformation; p27Kip1; Kaposi's sarcoma-associated herpesvirus