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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Molecular Diagnosis, Cancer Institute, Japanese Foundation for Cancer Research, 1-37-1 Kami-ikebukuro, Toshima-ku, Tokyo 170-8455, Japan.
Fumie
F
Matsuo
Ken-ichi
K
Yano
Hiroko
H
Saito
Keiko
K
Morotomi
Masahiro
M
Kato
Masataka
M
Yoshimoto
Fujio
F
Kasumi
Futoshi
F
Akiyama
Goi
G
Sakamoto
Yoshio
Y
Miki
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000235:genetics*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D019656:Loss of Heterozygosity; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D063150:Polycomb Repressive Complex 1; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics*; D012097:Repressor Proteins; D014407:Tumor Cells, Cultured / Q000378:metabolism
D017931:DNA Primers; D004268:DNA-Binding Proteins; C489348:PCGF2 protein, human; D012333:RNA, Messenger; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1