C-myc overexpression, c-mil, c-myb expression in a breast tumor cell line. Effects of estrogen and antiestrogen.
In breast tumor cell lines, c-myc amplification is frequently associated with estrogen unresponsiveness. We, however, succeeded in characterizing an estrogen-responsive cell line VHB1 derived from a duct cell carcinoma, which exhibits c-myc amplification and overexpression. We therefore studied the effects of estrogen and antiestrogen on c-myc expression in this particular cell line. We also investigated these effects on the expression of c-mil and c-myb oncogenes, also expressed but not amplified in VHB1 cells. Short-(1 h) and long-(72 h) term stimulations were performed. Our experiments showed that estradiol (E2 10(-8) M) was still able to stimulate c-myc expression equally either after short or long-term treatment. In the same way, the antiestrogen 4-hydroxytamoxifen equally decreased c-myc expression but the reversal effect of E2 after long-term antiestrogen treatment was more pronounced than after short-term treatment. The effects of E2 and 4-OH Tam on the expression of the not-amplified c-mil and c-myb oncogenes were stronger than those observed on c-myc expression; however, the E2 reversal effect was identical either after short or long-term antiestrogen treatment. Our results may enlighten some aspects of the complex action of some of the early- and late-growth regulated genes in breast cancer.
Collyn-d'Hooghe
M
M
U 124 INSERM, Lille, France.
Vandewalle
B
B
Hornez
L
L
Lantoine
D
D
Revillion
F
F
Lefebvre
J
J
Kerckaert
J P
JP
D015152:Blotting, Northern; D015139:Blotting, Southern; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016259:Genes, myc; D006801:Humans; D009857:Oncogenes; D011518:Proto-Oncogene Proteins / Q000235:genetics; D020598:Proto-Oncogene Proteins c-myb; D019908:Proto-Oncogene Proteins c-raf; D012334:RNA, Neoplasm / Q000032:analysis; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004965:Estrogen Antagonists; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D012334:RNA, Neoplasm; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; D019908:Proto-Oncogene Proteins c-raf