Abstract 1686
Background
Novel therapeutic strategies are needed for the treatment of triple negative breast cancer (TNBC). Inhibition of bromo and extraterminal domains (BET) has shown an anti-proliferative effect in TNBC as well as a synergistic interaction with polo-like kinase (PLK) inhibitors. As for many other therapeutic interventions, resistance to BET inhibitors is expected to occur at a given treatment point.
Methods
We generated two resistant models to the BET inhibitor JQ1, MDA-MB 231R and HS578TR. Western-blot, flow cytometry analysis, genomic and pharmacologic inhibition were executed to evaluate the anti-proliferative activity and biochemical effect. Nude mice were used to explore the in vivo pharmacological efficacy.
Results
We report the generation of two resistant models to the BET inhibitor JQ1. In both models, resistant cells were particularly sensitive to PLK1 inhibition, and reduced cell proliferation in 2D and 3D cell cultures. Although PLK1 levels were similar in sensitive and resistant cell lines, pharmacological inhibition of BRD4 using JQ1 reduced PLK1 to a less extent in the resistant model, effect not observed with BRD4 gene downregulation. PLK1 inhibitor volasertib induced G2/M arrest in both cell lines, and this effect was more evident in resistant cells, in addition to an increase in pH3 and pCDK1. Combination of volasertib and JQ1 induced apoptosis that was partially caspase dependent. A slight activation of Erk1/2 and pS6 was observed in the resistant model, but the inhibition of these kinases did not have a different effect on proliferation compared with the sensitive one. Finally, JQ1-resistant cells xenografted in mice displayed resistance to JQ1 that was reversed after administration of the PLK1 inhibitor volasertib.
Conclusions
PLK1 inhibition reverts resistance to BET inhibitors in our in vivo and in vitro models. These findings open avenues for further drug combinations in the clinical setting.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Universidad de Castilla-La Mancha.
Funding
Instituto de Salud Carlos III; ACEPAIN; CRIS CANCER; Diputación Albacete; UCLM.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
3963 - Robot-assisted natural orifice specimen extraction surgery for radical resection of colorectal cancer
Presenter: Zhengchuan Niu
Session: Poster Display session 2
Resources:
Abstract
3989 - Bevacizumab as adjuvant treatment for colon cancer: Updated results from the AVANT phase III Study by the GERCOR Group
Presenter: Thierry André
Session: Poster Display session 2
Resources:
Abstract
4741 - Real world data on adjuvant chemotherapy for high-risk stage II colorectal cancer – the role of tumor side
Presenter: Camila Araujo de Carvalho
Session: Poster Display session 2
Resources:
Abstract
4973 - Oncological Outcome and Safety of Bevacizumab (BV) Therapy in Patients with Occlusive Colon Cancer and Self-Expandable Metal Stents (SEMS)
Presenter: Vilma Pacheco-Barcia
Session: Poster Display session 2
Resources:
Abstract
2295 - Active chronic hepatitis B increases the risk of liver metastasis of colorectal cancer- a retrospective clinical study of 7187 consecutive cases of newly diagnosed colorectal cancer
Presenter: Lei Zhao
Session: Poster Display session 2
Resources:
Abstract
3845 - Comprehensive Evaluation of Recurrence Risk (CERR) Score for Colorectal Liver Metastases: Development and Validation
Presenter: Wei Ye
Session: Poster Display session 2
Resources:
Abstract
1976 - BRAF-mutated colorectal metastases: what is the benefit of liver surgery? Results from a cohort of 91 patients.
Presenter: Sahir Javed
Session: Poster Display session 2
Resources:
Abstract
2688 - The smallest colorectal liver metastasis size as a prognosis factor after laparoscopic liver resection
Presenter: Baptiste Cervantes
Session: Poster Display session 2
Resources:
Abstract
4961 - Validation of GAME score risk groups in resected colorectal cancer liver metastases and the prognostic relevance of KRAS, NRAS and BRAF mutation analysis
Presenter: Berta Martin-Cullell
Session: Poster Display session 2
Resources:
Abstract
5295 - Predictive factors and survival outcomes with stereotactic body radiation therapy in treatment of oligometastases in colorectal cancer
Presenter: Vibhay Pareek
Session: Poster Display session 2
Resources:
Abstract