Selective activity of deguelin identifies therapeutic targets for androgen receptor-positive breast cancer

• Published in: Breast cancer research and treatment Vol. 157; no. 3; pp. 475 - 488
• Main Authors: Robles, Andrew J., Cai, Shengxin, Cichewicz, Robert H., Mooberry, Susan L.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2016; Springer Nature B.V
• Subjects: Androgens; Animals; Antineoplastic Agents - administration & dosage; Antineoplastic Agents - therapeutic use; Breast cancer; Cancer research; Cancer therapies; Cell Line, Tumor; Cell Nucleus - metabolism; Cell Proliferation - drug effects; Cell Survival - drug effects; Drug Synergism; Drug therapy; Female; Gene Expression Regulation, Neoplastic - drug effects; Humans; Medicine; Medicine & Public Health; Mice; Oncology; Phenylthiohydantoin - administration & dosage; Phenylthiohydantoin - analogs & derivatives; Phenylthiohydantoin - therapeutic use; Phosphatidylinositol 3-Kinases - metabolism; Preclinical Study; Proto-Oncogene Proteins c-akt - metabolism; Receptors, Androgen - metabolism; Rotenone - analogs & derivatives; Rotenone - pharmacology; Signal Transduction - drug effects; Sirolimus - administration & dosage; Sirolimus - therapeutic use; TOR Serine-Threonine Kinases - metabolism; Triple Negative Breast Neoplasms - drug therapy; Triple Negative Breast Neoplasms - metabolism; Xenograft Model Antitumor Assays; mTOR; Deguelin; Enzalutamide; Luminal androgen receptor; Natural products; Triple-negative breast cancer
• ISSN: 0167-6806; 1573-7217
• DOI: 10.1007/s10549-016-3841-9

Triple-negative breast cancers (TNBC) are aggressive malignancies with no effective targeted therapies. Recent gene expression profiling of these heterogeneous cancers and the classification of cell line models now allows for the identification of compounds with selective activities against molecular subtypes of TNBC. The natural product deguelin was found to have selective activity against MDA-MB-453 and SUM-185PE cell lines, which both model the luminal androgen receptor (LAR) subtype of TNBC. Deguelin potently inhibited proliferation of these cells with GI 50 values of 30 and 61 nM, in MDA-MB-453 and SUM-185PE cells, respectively. Deguelin had exceptionally high selectivity, 197 to 566-fold, for these cell lines compared to cell lines representing other TNBC subtypes. Deguelin’s mechanisms of action were investigated to determine how it produced these potent and selective effects. Our results show that deguelin has dual activities, inhibiting PI3K/Akt/mTOR signaling, and decreasing androgen receptor levels and nuclear localization. Based on these data, we hypothesized that the combination of the mTOR inhibitor rapamycin and the antiandrogen enzalutamide would have efficacy in LAR models. Rapamycin and enzalutamide showed additive effects in MDA-MB-453 cells, and both drugs had potent antitumor efficacy in a LAR xenograft model. These results suggest that the combination of antiandrogens and mTOR inhibitors might be an effective strategy for the treatment of androgen receptor-expressing TNBC.