Mutation analysis of the mel-18 gene that shows decreased expression in human breast cancer cell lines

• Published in: Breast cancer (Tokyo, Japan) Japan), 2002-01, Vol.9 (1), p.33-38
• Main Authors: Matsuo, Fumie, Yano, Ken-ichi, Saito, Hiroko, Morotomi, Keiko, Kato, Masahiro, Yoshimoto, Masataka, Kasumi, Fujio, Akiyama, Futoshi, Sakamoto, Goi, Miki, Yoshio
• Format: Article
• Language: English
• Subjects: Adult; Aged; Breast Neoplasms - genetics; DNA Primers; DNA-Binding Proteins - genetics; Female; Gene Expression Regulation, Neoplastic; Genetic Predisposition to Disease - genetics; Humans; Loss of Heterozygosity; Middle Aged; Mutation - genetics; Polycomb Repressive Complex 1; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; Repressor Proteins; RNA, Messenger - genetics; Tumor Cells, Cultured - metabolism
• ISSN: 1340-6868; 1880-4233
• DOI: 10.1007/BF02967544

Mammalian mel-18 is a member of the polycomb group, and it acts as a transcriptional repressor with DNA binding activity. Murine mel-18 negatively regulates the cell cycle through the c-myc/cdc25 cascade, and mice haploinsufficient for mel-18 develop mammary gland tumors. In addition, the human homolog of mel-18 is located at 17q, on which candidate tumor suppressor genes for breast cancer have been suggested for a long time. These observations indicate that the mel-18 gene may be a tumor suppressor gene for breast cancer. To investigate this possibility, we examined the expression of mel-18 mRNA in human breast cancer cell lines and searched for mel-18 gene mutations in sporadic and familial breast cancers. The expression of mel-18 mRNA was examined in five breast cancer cell lines by RT-PCR, and somatic and germline mutations of the mel-18 gene were analyzed by the PCR-SSCP and sequence methods in 48 sporadic breast cancers, including 16 cases with loss of heterozygosity (LOH) at the mel-18 locus, and in 23 cases from 18 breast cancer families, respectively. We found that most cell lines examined here showed decreased expression of mel-18 mRNA, however, no alteration other than a single nucleotide change that did not lead to amino acid alteration in one patient was identified. Our results reveal that mel-18 gene mutations are exceedingly rare in human breast cancers, and a reduction of mel-18 expression in human breast cancer cell lines would support a role for mel-18 haploinsufficiency in breast carcinogenesis.