title: Small interfering RNA targeting of S phase kinase-interacting protein 2 inhibits cell growth of oral cancer cells by inhibiting p27 degradation.
abstract: S phase kinase-interacting protein 2 (Skp2), an F box protein, is required for the ubiquitination and consequent degradation of p27. It is well known that reduced expression of p27 is frequently observed in various cancers including oral squamous cell carcinoma and is due to an enhancement of its protein degradation. Our previous study showed that overexpression of Skp2 was frequently found in oral squamous cell carcinoma and inversely correlated with p27 expression. Recently, a technique known as RNA interference has been successfully adapted to mammalian cells. In the present study, we investigated if small interfering RNA (siRNA)-mediated gene silencing of Skp2 can be employed in order to inhibit p27 down-regulation in oral squamous cell carcinoma. We used a siRNA plasmid vector, which has an advantage over synthetic siRNAs in determining the effects of decreasing the high constitutive levels of Skp2 protein in oral squamous cell carcinoma. We showed that Skp2 siRNA transfection decreased Skp2 protein and induced the accumulation of p27 protein in oral squamous cell carcinoma cells. Moreover, p27 protein in Skp2 siRNA-transfected cells is more stabilized than that in control siRNA-transfected cells. Interestingly, Skp2 siRNA inhibited the cell proliferation of oral squamous cell carcinoma cells both in vitro and in vivo. Our findings suggest that siRNA-mediated gene silencing of Skp2 can be a novel modality of cancer gene therapy for suppression of p27 down-regulation.
authors.affiliation: Department of Oral Maxillofacial Pathobiology, Division of Frontier Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan. ykudo@hiroshima-u.ac.jp.
authors.forename: Yasusei
authors.initials: Y
authors.lastname: Kudo
authors.forename: Shojiro
authors.initials: S
authors.lastname: Kitajima
authors.forename: Ikuko
authors.initials: I
authors.lastname: Ogawa
authors.forename: Masae
authors.initials: M
authors.lastname: Kitagawa
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Miyauchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Takata
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D020868:Gene Silencing; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008819:Mice, Nude; D008957:Models, Genetic; D009062:Mouth Neoplasms / Q000188:drug therapy*; D010957:Plasmids / Q000378:metabolism; D061988:Proteasome Inhibitors; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000964:Antimetabolites, Antineoplastic; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D061988:Proteasome Inhibitors; D034741:RNA, Small Interfering; D044786:S-Phase Kinase-Associated Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D001973:Bromodeoxyuridine