title: Downregulation of the KIP family members p27(KIP1) and p57(KIP2) by SKP2 and the role of methylation in p57(KIP2) inactivation in nonsmall cell lung cancer.
abstract: Knowing the status of molecules involved in cell cycle control in cancer is vital for therapeutic approaches aiming at their restoration. The p27(KIP1) and p57(KIP2) cyclin-dependent kinase inhibitors are nodal factors controlling normal cell cycle. Their expression in normal lung raises the question whether they have a mutual exclusive or redundant role in nonsmall cell lung cancer (NSCLC). A comparative comprehensive analysis was performed in a series of 70 NSCLCs. The majority of cases showed significantly reduced expression of both members compared to normal counterparts. Low KIP protein levels correlated with increased proliferation, which seems to be histological subtype preponderant. At mechanistic level, degradation by SKP2 was demonstrated, in vivo and in vitro, by siRNA-methodology, to be the most important downregulating mechanism of both KIPs in NSCLC. Decreased p57(KIP) (2)-transcription complements the above procedure in lowering p57(KIP2)-protein levels. Methylation was the main cause of decreased p57(KIP) (2)-mRNA levels. Allelic loss and imprinting from LIT1 mRNA contribute also to decreased p57(KIP2) transcription. In vitro recapitulation of the in vivo findings, in A549 lung cells (INK4A-B((-/-))), suggested that inhibition of the SKP2-degradation mechanism restores p27(KIP1) and p57(KIP2) expression. Double siRNA treatments demonstrated that each KIP is independently capable of restraining cell growth. An additional demethylation step is required for complete reconstitution of p57(KIP2) expression in NSCLC.
authors.affiliation: Molecular Carcinogenesis Group, Laboratory of Histology-Embryology, Medical School, University of Athens, Athens, Greece.
authors.forename: Ioannis S
authors.initials: IS
authors.lastname: Pateras
authors.forename: Kalliopi
authors.initials: K
authors.lastname: Apostolopoulou
authors.forename: Marilena
authors.initials: M
authors.lastname: Koutsami
authors.forename: Kostas
authors.initials: K
authors.lastname: Evangelou
authors.forename: Petros
authors.initials: P
authors.lastname: Tsantoulis
authors.forename: Triantafillos
authors.initials: T
authors.lastname: Liloglou
authors.forename: Giorgos
authors.initials: G
authors.lastname: Nikolaidis
authors.forename: Fragiska
authors.initials: F
authors.lastname: Sigala
authors.forename: Christos
authors.initials: C
authors.lastname: Kittas
authors.forename: John K
authors.initials: JK
authors.lastname: Field
authors.forename: Athanassios
authors.initials: A
authors.lastname: Kotsinas
authors.forename: Vassilis G
authors.initials: VG
authors.lastname: Gorgoulis
mesh_terms: D001483:Base Sequence; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics*; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000235:genetics*; D019175:DNA Methylation; D017931:DNA Primers; D015536:Down-Regulation; D006801:Humans; D019656:Loss of Heterozygosity; D008175:Lung Neoplasms / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044786:S-Phase Kinase-Associated Proteins / Q000502:physiology*
chemical_list: D050761:Cyclin-Dependent Kinase Inhibitor p57; D017931:DNA Primers; D044786:S-Phase Kinase-Associated Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27