Regulation of BRCA1 and BRCA2 expression in human breast cancer cells by DNA-damaging agents.
Germline mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 have been linked to the development of breast cancer, ovarian cancer, and other malignancies. Recent studies suggest that the BRCA1 and BRCA2 gene products may function in the sensing and/or repair of DNA damage. To investigate this possibility, we determined the effects of various DNA-damaging agents and other cytotoxic agents on the mRNA levels of BRCA1 and BRCA2 in the MCF-7 and other human breast cancer cell lines. We found that several agents, including adriamycin (a DNA intercalator and inhibitor of topoisomerase II), camptothecin (a topoisomerase I inhibitor), and ultraviolet radiation induced significant decreases in BRCA1 and BRCA2 mRNA levels. Decreased levels of BRCA1 and BRCA2 mRNAs were observed within 6-12 h after treatment with adriamycin and persisted for at least 72 h. Adriamycin also induced decreases in BRCA1 protein levels; but these decreases required several days. U.V. radiation induced dose-dependent down-regulation of BRCA1 and BRCA2 mRNAs, with significant decreases in both mRNAs at doses as low as 2.5 J/m2, a dose that yielded very little cytotoxicity. Adriamycin-induced down-regulation of BRCA1 and BRCA2 mRNAs was first observed at doses that yielded relatively little cytotoxicity and little or no apoptotic DNA fragmentation. Adriamycin and U.V. radiation induced distinct dose- and time-dependent alterations in the cell cycle distribution; but these alterations did not correlate well with corresponding changes in BRCA1 and BRCA2 mRNA levels. However, the adriamycin-induced reduction in BRCA1 and BRCA2 mRNA levels was correlated with p53 functional status. MCF-7 cells transfected with a dominant negative mutant p53 (143 val-->ala) required at least tenfold higher doses of adriamycin to down-regulate BRCA1 and BRCA2 mRNAs than did parental MCF-7 cells or control-transfected MCF-7 clones. These results suggest that BRCA1 and BRCA2 may play roles in the cellular response to DNA-damaging agents and that there may be a p53-sensitive component to the regulation of BRCA1 and BRCA2 mRNA expression.
Andres
J L
JL
Department of Radiation Oncology, Long Island Jewish Medical Center, The Long Island Campus for the Albert Einstein College of Medicine, New Hyde Park, New York 11040, USA.
Fan
S
S
Turkel
G J
GJ
Wang
J A
JA
Twu
N F
NF
Yuan
R Q
RQ
Lamszus
K
K
Goldberg
I D
ID
Rosen
E M
EM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D019313:BRCA1 Protein / Q000096:biosynthesis* / Q000187:drug effects* / Q000235:genetics; D024682:BRCA2 Protein; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004317:Doxorubicin / Q000494:pharmacology; D005260:Female; D006801:Humans; D007364:Intercalating Agents / Q000494:pharmacology*; D008466:Mechlorethamine / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000187:drug effects* / Q000235:genetics; D017239:Paclitaxel / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis* / Q000187:drug effects* / Q000235:genetics; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D014750:Vincristine / Q000494:pharmacology
D000970:Antineoplastic Agents; D019313:BRCA1 Protein; D024682:BRCA2 Protein; D007364:Intercalating Agents; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D008466:Mechlorethamine; D014750:Vincristine; D004317:Doxorubicin; D017239:Paclitaxel