Functional identification of genes causing estrogen independence of human breast cancer cells.
Endocrine treatment of breast cancer is widely applied and effective. However, in advanced disease cases, the tumors will eventually progress into an estrogen-independent and therapy-resistant phenotype. To elucidate the molecular mechanisms underlying this endocrine therapy failure, we applied retroviral insertion mutagenesis to identify the main genes conferring estrogen independence to human breast cancer cells. Estrogen-dependent ZR-75-1 cells were infected with replication-defective retroviruses followed by selection with the anti-estrogen 4-hydroxy-tamoxifen. In the resulting panel of 79 tamoxifen-resistant cell lines, the viral integrations were mapped within the human genome. Genes located in the immediate proximity of the retroviral integration sites were characterized for altered expression and their capacity to confer anti-estrogen resistance when transfected into breast cancer cells. Out of 15 candidate BCAR (breast cancer anti-estrogen resistance) genes, seven (AKT1, AKT2, BCAR1, BCAR3, EGFR, GRB7, and TRERF1/BCAR2) were shown to directly underlie estrogen independence. Our results show that insertion mutagenesis is a powerful tool to identify BCAR loci, which may provide insights into the molecular and cellular mechanisms of breast tumor progression and therapy resistance thereby offering novel targets for the development of tailor-made therapeutical and prevention strategies.
van Agthoven
Ton
T
Department of Pathology, Josephine Nefkens Institute, Be 432, Erasmus MC-University Medical Center Rotterdam, P.O. Box 2040, Rotterdam, CA, 3000, The Netherlands.
Veldscholte
Jos
J
Smid
Marcel
M
van Agthoven
Thecla L A
TL
Vreede
Lilian
L
Broertjes
Marieke
M
de Vries
Ingrid
I
de Jong
Danielle
D
Sarwari
Roya
R
Dorssers
Lambert C J
LC
D001943:Breast Neoplasms / Q000235:genetics* / Q000503:physiopathology*; D045744:Cell Line, Tumor; D004967:Estrogens / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D016254:Mutagenesis, Insertional; D012190:Retroviridae; D016662:Virus Integration
D004967:Estrogens