Abstract 1674
Background
Triple negative breast cancer (TNBC) is an incurable disease, therefore novel therapies are needed. Bromo and extraterminal domain inhibitors (BETi) are currently in clinical development with promising activity in TNBC. However, resistance to these agents will limit their efficacy. Proteolysis targeting chimeric (PROTAC) are novel compounds that by binding to a ubiquitin ligase promotes protein degradation.
Methods
In our study we explore the antitumoral activity of two BET-PROTACs, MZ1 and ARV-825 in TNBC and ovarian cancer. We used MDAMB-231, BT549 and MDAMB-231 JQ1 resistant TNBC cells lines; and OVCAR3 and SKOV3 ovarian cancer cells lines. We evaluated the antiproliferation effect using MTT assay, colony-forming assay and three-dimensional cultures in Matrigel. To explore the molecular mechanism of drugs we used flow cytometry (cell cycle and cell death). The analysis of protein expression was determined by western blot. In vivo studies included BALB/c nu/nu mice that were injected with MDAMB-231 JQ1 resistant cells and later treated with BETi JQ1 and BET-PROTAC MZ1.
Results
Both PROTACs efficiently and maintained deleted the levels of BRD4 in MDA-MB-231 and in the resistant JQ1 cell line MDA-MB-231R. MZ1 and ARV-825 showed a profound antiproliferative effect in MDA-MD-231 sensitive and resistant cells using 2D and 3D cultures, and had a similar activity in other triple negative (BT549) and ovarian cancer (SKOV3, OVCAR) cell lines. MZ1 slightly arrested cells at G2/M in sensitive and resistant JQ1 MDA-MB-231 cells. In addition, a profound effect on apoptosis was observed, that was more evident in the sensitive cell line, effect that was caspase dependent. Given the potent antiproliferative activity of MZ1 no synergistic activity was observed when combined with docetaxel, cisplation or olaparib. Finally, administration of MZ1 was able to recue tumor growth in nude mice of MDA-MB-231 JQ1 resistant cells, by reducing the expression of BRD4.
Conclusions
We describe the profound activity of BET-PROTACs in TNBC cell lines and in an in vivo BETi resistant model. This data provides options for further clinical development of these agents in TNBC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Instituto de Salud Carlos III (PI16/01121), ACEPAIN; Diputación de Albacete, CIBERONC, CRIS Cancer Foundation, implementation research program of the UCLM System of Science, Technology and Innovation-Secti (co-funded by the European Commission/FSE funds) and scientific foundation of the AECC.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
4022 - Ribociclib (RIB) plus letrozole (LET) in male patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) from the CompLEEment-1 trial
Presenter: Mario Campone
Session: Poster Display session 2
Resources:
Abstract
3599 - Comparative effectiveness of palbociclib plus letrozole vs letrozole for metastatic breast cancer in US real-world clinical practices
Presenter: Rachel Layman
Session: Poster Display session 2
Resources:
Abstract
901 - Pharmacokinetics (PK), safety, and efficacy of [fam-] trastuzumab deruxtecan with OATP1B/CYP3A inhibitors in subjects with HER2-expressing advanced solid tumors
Presenter: Yung-Jue Bang
Session: Poster Display session 2
Resources:
Abstract
2777 - A Phase 2 study of abemaciclib in patients (pts) with brain metastases (BM) secondary to non-small cell lung cancer (NSCLC) or melanoma (MEL).
Presenter: Solmaz Sahebjam
Session: Poster Display session 2
Resources:
Abstract
3980 - Ribociclib (RIB) + letrozole (LET) in patients (pts) with visceral metastases (VM) or bone-only metastases (BOM) in hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC): Subgroup analysis from the CompLEEment-1 trial
Presenter: Michelino De Laurentiis
Session: Poster Display session 2
Resources:
Abstract
4024 - Ribociclib (RIB) + letrozole (LET) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) and central nervous system (CNS) metastases: Subgroup analysis from the phase 3b CompLEEment-1 trial
Presenter: Paul Cottu
Session: Poster Display session 2
Resources:
Abstract
2151 - Clinical outcome and toxicity data in patients with advanced breast cancer treated with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors combined with endocrine therapy in a real-world clinical setting.
Presenter: Elena Fountzilas
Session: Poster Display session 2
Resources:
Abstract
3994 - Safety and efficacy of Ribociclib (RIBO) + letrozole (LET) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (ABC): Interim results from the Italian cohort of the CompLEEment-1 (C-1) study.
Presenter: Michele De Laurentiis
Session: Poster Display session 2
Resources:
Abstract
1370 - Interim Results From CompLEEment-1 (A Phase 3b Study of Ribociclib and Letrozole as First-Line Therapy for Advanced Breast Cancer in an Expanded Population): Spanish cohort results
Presenter: Javier Salvador
Session: Poster Display session 2
Resources:
Abstract
1109 - First Canadian Interim Analysis from the Phase IIIb CompLEEment-1 Ribociclib + Letrozole HR+ HER2- Advanced Breast Cancer Trial
Presenter: Cristiano Ferrario
Session: Poster Display session 2
Resources:
Abstract