title: Cloning of the 5' upstream region of the rat p16 gene and its role in silencing.
abstract: Hypermethylation of the 5' upstream region (5' region) of the human p16(CDKN2A) (p16) gene is known to cause silencing, which is involved in a wide range of human cancers. For the rat p16 gene, its 5' region has not been cloned, and it is uncertain whether surrogate use of exon 1 alpha is adequate for analysis of p16 silencing. In this study, we observed that methylation analysis of exon 1 alpha gave false positive results in three samples of normal rat mammary epithelia and in two of six primary mammary carcinomas. Therefore, we determined the nucleotide sequence of the 5' region of the rat p16 gene. To confirm that methylation status of the 5' region is correlated with p16 expression, the methylation status was analyzed by bisulfite sequencing and methylation-specific PCR in three samples of normal mammary glands, six samples of mammary carcinomas and four cell lines. The 5' region was demethylated in all of the three normal and six carcinoma samples that fully expressed p16. On the other hand, the 5' region was highly methylated in the 3Y1 cell line, which lacked p16 expression, but without deletion. These results showed that the methylation status of the 5' region was more closely correlated with p16 expression than that of the exon 1 alpha and analysis of the methylation status is useful in examining p16 silencing in various rat tumors.
authors.affiliation: Carcinogenesis Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Abe
authors.forename: Eriko
authors.initials: E
authors.lastname: Okochi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuramoto
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kaneda
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takato
authors.forename: Takashi
authors.initials: T
authors.lastname: Sugimura
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Ushijima
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018899:CpG Islands; D019175:DNA Methylation; D005091:Exons; D020868:Gene Silencing; D019942:Genes, p16 / Q000502:physiology*; D008969:Molecular Sequence Data; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured