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posted on 2025-08-21, 07:40 authored by Benjamin C. Brim, Andres F. Leon, Erica L. Beatson, Jessica D. Kindrick, Kinjal Bhadresha, Xiaohu Zhang, Giulia C. Napoli, Emily N. Risdon, Keith T. Schmidt, Kelli M. Wilson, Crystal McKnight, Erin Beck, Carleen Klumpp-Thomas, Michele Ceribelli, JuanJuan Yin, Adam G. Sowalsky, Douglas K. Price, Cindy H. Chau, Craig J. Thomas, William D. Figg <p>Dual targeting of Bcl-xL and Mcl-1 leads to synergistic decreases in cell viability in 3D LNCaP95 spheroids and the LuCaP 167CR organoid model. Dual treatment of navitoclax and A-1331852 with S63845 in 3D prostate cancer models. <b>A,</b> Representative images for each treatment condition before treatment and 24, 48, and 72 hours after treatment. <b>B</b> and <b>C,</b> Viability of spheroids measured by 3D CellTiter-Glo after 72 hours of treatment. Plots show mean ± SD. ****, <i>P</i> < 0.0001. LuCaP-167CR organoids were treated with the combination of A-1331852 and S63845 (<b>D–F</b>) or navitoclax and S63845 (<b>G–I</b>). Drug curves (<b>D</b> and <b>G</b>) show mean ± SD. Dose–response matrices (<b>E</b> and <b>H</b>) and Bliss synergy plots (<b>F</b> and <b>I</b>) were generated using the Synergyfinder+ R package to evaluate synergy. All spheroid experiments were completed in triplicate. Organoid experiments had six technical replicates with three biological replicates.</p>
History
ARTICLE ABSTRACT
There is an unmet need to develop novel treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC). Patients often develop resistance to next-generation hormonal therapies that target the androgen receptor (AR) axis (e.g., abiraterone and enzalutamide). A splice variant of AR, AR-V7, is associated with resistance to these inhibitors as well as mCRPC progression and poor prognoses. We embarked upon a high-throughput screen to identify synergistic combinations of targeted therapies using two CRPC cell lines, LNCaP95 and VCaP-CR. Combinations targeting BCL2L1 (Bcl-xL) (A-1331852 and navitoclax) and MCL1 (S63845) synergistically decreased cell viability and induced apoptotic activity via cleavage of PARP, caspase 3, and caspase 7 across AR-V7–expressing CRPC cell lines (LNCaP95, VCaP-CR, and 22Rv1) and a patient-derived organoid model (LuCaP 167CR). We also explored the use of a Bcl-xL–specific proteolysis-targeting chimera degrader (PROTAC) to minimize platelet toxicity associated with Bcl-xL inhibitors. We showed similar synergistic efficacy with the Bcl-xL–targeting PROTAC in combination with S63845 in the three-dimensional spheroid models. Our findings support further preclinical development of Bcl-xL and Mcl-1 inhibitors for mCRPC.
Using an unbiased, combinatorial, high-throughput drug screen, we identified the combination of co-targeting Bcl-xL and Mcl-1 to be highly synergistic across AR-V7–expressing CRPC models. We showed efficacy in higher-order models through validation across in vitro models spanning two-dimensional cell culture, three-dimensional cell culture, and a patient-derived organoid model. These findings identify a promising therapeutic strategy for patients with AR-V7–expressing CRPC.
