A) JQ1 and OTX015 inhibitory action, as the IC50, calculated after 48 and 72 hours of treatment using MTT assay as described in "Material and methods". 2B) Antiproliferative effect of JQ1 in semi-solid MDA-MB-231 cultures. Cells (25,000/ml) were plated in 48 multiwell plates and grown in medium containing 2% matrigel in the presence of JQ1 (0.2µM), cisplatin (2.5 µM) and docetaxel (0.5nM) alone and in combination for 3 days. All images were taken at Ã-20 magnification. The quantification of sphere diameter was performed manually by tracing a straight line across the sphere diameter of untreated cells (controls) and scoring its value as arbitrary length units. Total number of colonies per plate was manually counted.
Funding
Instituto de Salud Carlos III
ACEPAIN; AMAC, Diputación de Albacete and CRIS Cancer Foundation
Ministry of Economy and Competitiveness of Spain
AECC
Miguel Servet
ARTICLE ABSTRACT
Triple-negative breast cancer (TNBC) is an incurable disease with poor prognosis. At this moment, therapeutic options are limited to chemotherapy, and no targeted agent has reached the clinical setting. Bromodomain and extraterminal (BET) inhibitors are a new family of compounds that inhibit bromodomain-containing proteins affecting the expression of transcription factors, therefore modifying the expression of relevant oncogenic genes. In the present article, by using an in silico approach, we have identified the expression of upregulated transcription factors in TNBC compared with normal breast. Treatment with JQ1, a well-characterized BET inhibitor, modified some transcription factors, including DEP domain containing 1 (DEPDC), Forkhead box M1 (FOXM1), and Lim domain only 4 (LM04). In cell line models, administration of JQ1 or OTX015, another BET inhibitor, produced a significant antiproliferative effect and synergized with chemotherapies. Biochemical evaluation demonstrated an arrest at G1 as the main mechanism of action with a clear increase of p27. Addition of these compounds to chemotherapy induced apoptosis compared to each agent given alone. Evaluation of JQ1 in xenografted tumors in nude mice showed a profound antitumoral effect with a reduction of DEPDC, FOXM1, and LM04, in addition to an increase of p27. Globally, our data demonstrate the antitumor effect of this new family of compounds in TNBC, paving the way for its future clinical development. Mol Cancer Ther; 15(8); 1823–33. ©2016 AACR.
