title: Reduced expression of cell cycle regulator p18(INK4C) in human hepatocellular carcinoma.
abstract: Cyclins, cyclin-dependent kinases (Cdks), and Cdk inhibitors (CdkIs) are frequently altered in human cancer. p18INK4C, a member of the INK4 family of CdkIs, is a potential tumor-suppressor gene product. However, the expression of p18INK4C in hepatocellular carcinoma (HCC) remains unknown. The aim of this study was to examine the expression of p18INK4C in various liver diseases including HCC and to assess its clinical significance in HCC. To that end, we examined the expression of p18INK4C by immunohistochemistry in various liver diseases, including 51 HCCs, and also studied the relationship between p18INK4C expression, the phosphorylation of retinoblastoma protein (pRb), and the activity level of Cdk4 and Cdk6. Immunohistochemical analysis revealed the frequent loss of p18INK4C expression in HCC, especially in poorly differentiated HCC. The loss of p18INK4C expression was shown to be associated with a poor prognosis compared with that associated with p18INK4C- positivity. Further, the kinase activity of Cdk4 was found to be higher in p18INK4C-negative HCCs than in p18INK4C- positive HCCs. However, the level of Cdk6 activity was similar in the 2 groups of HCCs. In p18INK4C- positive HCCs, p18INK4C dominantly interacted with Cdk4 rather than with Cdk6. pRb phosphorylated at serine(Ser) 780 was detected more frequently in p18INK4C - negative than in p18INK4C - positive HCCs. In conclusion, the loss of p18INK4C expression may play a role in the differentiation and development of HCC through the up-regulation of Cdk4 activity.
authors.affiliation: Third Department of Internal Medicine, Kagawa Medical University, Kagawa, Japan.
authors.forename: Asahiro
authors.initials: A
authors.lastname: Morishita
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Masaki
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshiji
authors.forename: Seiji
authors.initials: S
authors.lastname: Nakai
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ogi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: Shuhei
authors.initials: S
authors.lastname: Yoshida
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Funaki
authors.forename: Naohito
authors.initials: N
authors.lastname: Uchida
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kita
authors.forename: Fumi
authors.initials: F
authors.lastname: Funakoshi
authors.forename: Hisashi
authors.initials: H
authors.lastname: Usuki
authors.forename: Setsuo
authors.initials: S
authors.lastname: Okada
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Izuishi
authors.forename: Seishiro
authors.initials: S
authors.lastname: Watanabe
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kurokohchi
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kuriyama
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D018797:Cell Cycle Proteins / Q000235:genetics*; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050763:Cyclin-Dependent Kinase Inhibitor p18; D018844:Cyclin-Dependent Kinases / Q000032:analysis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: C493971:CDKN2C protein, human; D018797:Cell Cycle Proteins; D050763:Cyclin-Dependent Kinase Inhibitor p18; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases