title: Analysis of a role for p16/CDKN2 expression and methylation patterns in human oral squamous cell carcinoma.
abstract: The p16/CDKN2 (cyclin dependent kinase number 2) gene is known to be one of the negative regulators of the cell cycle. Aberrant 5'CpG island methylation is one of the most important mechanisms of p16/CDKN2 gene promoter region alteration. We studied 8 oral squamous cell carcinoma cell lines and 25 primary tumor tissues for the p16/CDKN2 gene and its expression by PCR-SSCP, MSP, RT-PCR, and immunohistochemical methods to determine the mechanism and the potential biological significance of p16/CDKN2 gene inactivation. In primary tumors, no p16/CDKN2 gene mutations were found by PCR-SSCP. However, hypermethylation of the CpG sites of p16/CDKN2 gene was observed in 48% (12/25) cases of primary tumors and in 50% (4/8) of cell lines. To verify the p16 mRNA expression, we employed RT-PCR and observed decreased or lacked p16 mRNA in 44% (11/25) of primary tumor tissues. In addition, hypermethylation was observed in 6 of the above 11 cases (55%). An immunohistochemistry assay was also performed with the primary tumor tissues, and a semi-quantitative method was used to evaluate the staining intensity of p16 protein. We observed 52% (13/25) negative nuclear staining. When we compared these results with clinicopathological stages, there was no statistical significance. These findings suggest that hypermethylation of p16/CDKN2 promoter region may be associated with p16/CDKN2 gene alteration.
authors.affiliation: First Department of Oral & Maxillofacial Surgery, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yakushiji
authors.forename: H
authors.initials: H
authors.lastname: Noma
authors.forename: T
authors.initials: T
authors.lastname: Shibahara
authors.forename: K
authors.initials: K
authors.lastname: Arai
authors.forename: N
authors.initials: N
authors.lastname: Yamamoto
authors.forename: C
authors.initials: C
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Uzawa
authors.forename: H
authors.initials: H
authors.lastname: Tanzawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism*; D016009:Chi-Square Distribution; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis / Q000378:metabolism; D005260:Female; D019942:Genes, p16; D006801:Humans; D007124:Immunoenzyme Techniques; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics* / Q000378:metabolism*; D018807:Polymorphism, Single-Stranded Conformational; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm