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Studying Triple Negative Breast Cancer Using Orthotopic Breast Cancer Model
Published on: March 20, 2020
Activity of BET-proteolysis targeting chimeric (PROTAC) compounds in triple negative breast cancer
María Del Mar Noblejas-López1,2, Cristina Nieto-Jimenez1,2, Miguel Burgos1
1Translational Research Unit, Albacete University Hospital, C/ Francisco Javier de Moya sn, 02006, Albacete, Spain.
Background:
Triple negative breast cancer (TNBC) is an incurable disease where novel therapeutic strategies are needed. Proteolysis targeting chimeric (PROTAC) are novel compounds that promote protein degradation by binding to an ubiquitin ligase. In this work, we explored the antitumoral activity of two novel BET-PROTACs, MZ1 and ARV-825, in TNBC, ovarian cancer and in a BET inhibitor resistant model.
Methods:
OVCAR3, SKOV3, BT549, MDA-MB-231 cell lines and the JQ1 resistant cell line MDA-MB-231R were evaluated. MTTs, colony-forming assay, three-dimensional cultures in matrigel, flow cytometry, and western blots were performed to explore the anti-proliferative effect and biochemical mechanism of action of MZ1 and ARV-825. In vivo studies included BALB/c nu/nu mice engrafted with MDA-MB-231R cells.
Results:
The BET-PROTACs MZ1 and ARV-825 efficiently downregulated the protein expression levels of the BET protein BRD4, in MDA-MB-231 and MDA-MB-231R. MZ1 and ARV-825 also showed an antiproliferative effect on sensitive and resistant cells. This effect was corroborated in other triple negative (BT549) and ovarian cancer (SKOV3, OVCAR3) cell lines. MZ1 provoked G2/M arrest in MDA-MB-231. In addition, a profound effect on caspase-dependent apoptosis was observed in both sensitive and resistant cells. No synergistic activity was observed when it was combined with docetaxel, cisplatin or olaparib. Finally, in vivo administration of MZ1 rescued tumor growth in a JQ1-resistant xenograft model, reducing the expression levels of BRD4.
Conclusions:
Using both in vitro and in vivo approaches, we describe the profound activity of BET-PROTACs in parental and BETi-resistant TNBC models. This data provides options for further clinical development of these agents in TNBC.
Insights
Novel BET-PROTACs, MZ1 and ARV-825, demonstrate significant anti-tumor activity against triple-negative breast cancer (TNBC) and ovarian cancer cells, including drug-resistant models. These compounds effectively degrade BRD4 protein, offering a promising therapeutic strategy for TNBC.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- Triple-negative breast cancer (TNBC) presents a significant unmet medical need due to its aggressive nature and lack of targeted therapies.
- Proteolysis targeting chimeras (PROTACs) represent a novel therapeutic modality that hijacks the cell's ubiquitin-proteasome system to degrade target proteins.
- BET proteins are epigenetic regulators implicated in various cancers, making them attractive therapeutic targets.
Purpose of the Study:
- To investigate the anti-tumor efficacy of two novel BET-PROTACs, MZ1 and ARV-825, in TNBC, ovarian cancer, and BET inhibitor-resistant models.
- To elucidate the mechanism of action of these BET-PROTACs in cancer cells.
- To evaluate the in vivo efficacy of BET-PROTACs in a resistant TNBC xenograft model.
Main Methods:
- Utilized multiple human cancer cell lines including TNBC (BT549, MDA-MB-231) and ovarian cancer (OVCAR3, SKOV3), along with a JQ1-resistant TNBC line (MDA-MB-231R).
- Assessed anti-proliferative effects using MTT assays, colony-forming assays, and 3D matrigel cultures.
- Investigated molecular mechanisms via flow cytometry for cell cycle analysis and apoptosis, and western blotting for protein degradation (BRD4).
- Conducted in vivo studies using BALB/c nude mice xenografted with MDA-MB-231R cells.
Main Results:
- MZ1 and ARV-825 effectively reduced BRD4 protein levels in both sensitive and resistant TNBC cells.
- Both BET-PROTACs exhibited significant anti-proliferative activity across TNBC and ovarian cancer cell lines, including the resistant model.
- MZ1 induced G2/M cell cycle arrest and promoted caspase-dependent apoptosis in sensitive and resistant cells.
- In vivo administration of MZ1 suppressed tumor growth in a JQ1-resistant xenograft model, correlating with reduced BRD4 expression.
Conclusions:
- BET-PROTACs demonstrate potent anti-tumor activity against both drug-sensitive and drug-resistant TNBC models.
- These findings support the clinical development of BET-PROTACs as a therapeutic option for TNBC patients, including those who have developed resistance to conventional BET inhibitors.
- The study highlights the potential of PROTAC technology in overcoming therapeutic resistance in challenging cancers.
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