The rapamycin-regulated gene expression signature determines prognosis for breast cancer.
BACKGROUND
Mammalian target of rapamycin (mTOR) is a serine/threonine kinase involved in multiple intracellular signaling pathways promoting tumor growth. mTOR is aberrantly activated in a significant portion of breast cancers and is a promising target for treatment. Rapamycin and its analogues are in clinical trials for breast cancer treatment. Patterns of gene expression (metagenes) may also be used to simulate a biologic process or effects of a drug treatment. In this study, we tested the hypothesis that the gene-expression signature regulated by rapamycin could predict disease outcome for patients with breast cancer.


RESULTS
Colony formation and sulforhodamine B (IC50 < 1 nM) assays, and xenograft animals showed that MDA-MB-468 cells were sensitive to treatment with rapamycin. The comparison of in vitro and in vivo gene expression data identified a signature, termed rapamycin metagene index (RMI), of 31 genes upregulated by rapamycin treatment in vitro as well as in vivo (false discovery rate of 10%). In the Miller dataset, RMI did not correlate with tumor size or lymph node status. High (>75th percentile) RMI was significantly associated with longer survival (P = 0.015). On multivariate analysis, RMI (P = 0.029), tumor size (P = 0.015) and lymph node status (P = 0.001) were prognostic. In van 't Veer study, RMI was not associated with the time to develop distant metastasis (P = 0.41). In the Wang dataset, RMI predicted time to disease relapse (P = 0.009).


CONCLUSIONS
Rapamycin-regulated gene expression signature predicts clinical outcome in breast cancer. This supports the central role of mTOR signaling in breast cancer biology and provides further impetus to pursue mTOR-targeted therapies for breast cancer treatment.
Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA. aakcakanat@mdanderson.org
Argun
A
Akcakanat
Li
L
Zhang
Spiridon
S
Tsavachidis
Funda
F
Meric-Bernstam
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D011379:Prognosis; D016016:Proportional Hazards Models; D020123:Sirolimus / Q000494:pharmacology*; D016019:Survival Analysis; D013997:Time Factors; D014410:Tumor Stem Cell Assay; D023041:Xenograft Model Antitumor Assays / Q000706:statistics & numerical data
D000903:Antibiotics, Antineoplastic; D020123:Sirolimus