Rationally derived drug combinations with the novel Mcl-1 inhibitor EU-5346 in breast cancer
Recent studies have emphasized a key role for the anti-apoptotic Bcl-2 family member Mcl-1 in conferring tumor cell survival and drug resistance in breast cancer (BC). Mcl-1 inhibitors, such as the BH3-mimetic EU-5346, therefore represent an exciting new class of targeting agents and are a current focus of widespread cancer-drug development efforts.
ONCOMINE analysis was utilized to compare expression profiles of Bcl-2 family members across all major BC subgroups. Potential toxicities of EU-5346 were evaluated using iPS-generated cardiomyocytes, blood cells and astrocytes. The anti-BC cell activity of EU-5346-based therapies was evaluated using [3H]-thymidine uptake and spheroid-forming assays as well as immunoblotting and the Chou-Talalay method. Protein level-based activity of EU-5346, the specific anti-Bcl-2 inhibitor ABT-199 and the specific anti-Bcl-xL inhibitor WEHI-539 was verified in Mcl-1Δ/null versus Mcl-1wt/wt MEFs.
We previously demonstrated significant anti-tumor activity of EU-5346 in all BC subtypes. Our present results go further and suggest that EU-5346 may induce limited adverse events such as cardiotoxicity, hematotoxicity, and neurotoxicity, frequently observed with other BH3 mimetics. As demonstrated by our mathematical scoring model, the prediction of EU-5643-induced IC50 not only relies on the protein level of Mcl-1 but also on Bak, Bim, and Noxa. Synergistic anti-BC activity of low-dose EU-5346 with the BH3 mimetics ABT-199 or WEHI-539 was observed only in those BC cells expressing Bcl-2 or Bcl-xL, respectively. Similarly, when combined with tamoxifen or trastuzumab, low-dose EU-5346 induced significant anti-BC activity in hormone receptor positive or Her2-positive BC cells, respectively. Finally, EU-5346 in combination with paclitaxel induced synergistic anti-BC activity in both paclitaxel-sensitive and paclitaxel-resistant TNBC cells.
These data strongly support the further clinical development of EU-5346 to improve BC patient survival.
KeywordsBreast cancer Mcl-1 BH3 mimetics Mathematical scoring model Combination therapies
Mitochondrial outer membrane permeabilization
Myeloid cell leukemia-1
Bcl-2 homology 3
The Cancer Genome Atlas (TCGA)
Induced pluripotent stem cell
Murine embryonic fibroblasts
Peripheral blood mononuclear cells
SM is the recipient of a DGHO/ Jose Carreras stipend. KP is the recipient of a B. Braun Stiftungs Grant. MP and KP received research support from Roche Pharmaceuticals. We cordially thank Muhammad Hasan Bashari for technical assistance.
SV conceived of the study, designed experiments, analyzed data, and wrote the manuscript. FF and SM performed experiments and participated in data analysis and interpretation. MS, JTO and MHC conceived of the study and participated in data analysis and interpretation. MP, AS and DJ made substantial contributions to the acquisition and interpretation of data. KP conceived of the study, designed and coordinated experiments, analyzed and interpreted data and wrote the manuscript. All authors were involved in revising the manuscript critically for important intellectual content. All authors approved the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
KP received speaker honorarium from Celgene, Janssen, and Amgen. MP and KP received research support from Roche Pharmaceuticals. JTO received consultant honorarium and research support from AbbVie. DJ received consultant honorarium from Bayer, Amgen, MSD, CureVac, Roche, BMS. MHC is the co-funder, president and CEO of Eutropics, Inc. The remaining authors declare no conflict of interest.
This study complied with current laws of Germany, Austria and USA. The collection and use of primary cells has been approved by the Ethics committee of the Medical Faculty, University of Heidelberg (Approval Number 022/2013).
Informed consent was obtained in accordance with the Declaration of Helsinki. This article does not contain any studies with animals performed by any of the authors.
- 15.Leverson JD, Zhang H, Chen J et al (2015) Potent and selective small-molecule MCL-1 inhibitors demonstrate on-target cancer cell killing activity as single agents and in combination with ABT-263 (navitoclax). Cell Death Dis 6:e1590. https://doi.org/10.1038/cddis.2014.561 CrossRefPubMedPubMedCentralGoogle Scholar
- 27.Placzek WJ, Wei J, Kitada S et al (2010) A survey of the anti-apoptotic Bcl-2 subfamily expression in cancer types provides a platform to predict the efficacy of Bcl-2 antagonists in cancer therapy. Cell Death Dis 1:e40. https://doi.org/10.1038/cddis.2010.18 CrossRefPubMedPubMedCentralGoogle Scholar
- 38.Bannister T, Koenig M, He Y, Mishra J, Spicer T, Minond D, Saldanha A, Mercer BA, Cameron M, Lena R, Carlson N, Richard D, Cardone MHP (2013) ML311: A Small Molecule that Potently and Selectively Disrupts the Protein-Protein Interaction of Mcl-1 and Bim: A Probe for Studying Lymphoid Tumo… In: Probe Reports from NIH Mol. Libr. Progr. [Internet]. Bethesda Natl. Cent. Biotechnol. Inf. http://www.ncbi.nlm.nih.gov/pubmed/23762927. Accessed 8 Jun 2015