title: Frequent inactivation of the cyclin-dependent kinase inhibitor p18 by homozygous deletion in multiple myeloma cell lines: ectopic p18 expression inhibits growth and induces apoptosis.
abstract: Multiple myeloma (MM) is a clonal neoplasm of plasma cells which offers an excellent model to study multistep molecular oncogenesis. In 20-25% of primary tumors and cell lines examined, cyclin D1 is overexpressed due to the translocation t(11;14)(q13;q32). We have characterized cyclin-dependent kinase inhibitor p15 (CDKN2B), p16 (CDKN2A) and p18 (CDKN2C) deletions in cyclin D1-expressing and non-expressing MM cell lines. p18 was found to be frequently deleted (38%); in some cases p18 deletions coexisted with hemizygous p16 deletion. To examine the function of p18 as a putative tumor suppressor in myeloma cells, a zinc-inducible p18 construct was stably transfected into KMS12, a MM cell line with biallelic p18 and monoallelic p16 deletions as well as cyclin D1 overexpression. Ectopic expression of p18 caused 40-45% growth suppression as determined by trypan blue exclusion and MTS assays. p18 induction also resulted in apoptosis, suggesting that inhibition of the cyclin D1/CDK/pRb pathway in these tumor cells could be a crucial step toward the induction of tumor regression via apoptotic cell death. This cell cycle pathway is thus frequently mutated and provides a potentially novel target for gene therapeutic or pharmacologic approaches to human myeloma.
authors.affiliation: Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Kulkarni
authors.forename: J L
authors.initials: JL
authors.lastname: Daggett
authors.forename: T P
authors.initials: TP
authors.lastname: Bender
authors.forename: W M
authors.initials: WM
authors.lastname: Kuehl
authors.forename: P L
authors.initials: PL
authors.lastname: Bergsagel
authors.forename: M E
authors.initials: ME
authors.lastname: Williams
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002455:Cell Division; D019938:Cyclin D1 / Q000502:physiology; D051361:Cyclin-Dependent Kinase 6; D050763:Cyclin-Dependent Kinase Inhibitor p18; D018844:Cyclin-Dependent Kinases; D004791:Enzyme Inhibitors; D017353:Gene Deletion; D016147:Genes, Tumor Suppressor; D005838:Genotype; D006801:Humans; D020522:Lymphoma, Mantle-Cell / Q000473:pathology; D009101:Multiple Myeloma / Q000235:genetics* / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics* / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: C493971:CDKN2C protein, human; D018797:Cell Cycle Proteins; D050763:Cyclin-Dependent Kinase Inhibitor p18; D004791:Enzyme Inhibitors; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D017346:Protein Serine-Threonine Kinases; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases