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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>Identification of Synergistic BH<sub>3</sub>-mimetic–based combinations in LNCaP95 and VCaP-CR Cells. <b>A,</b> Correlation plot depicting DBSumNeg (synergy score) for drugs that pair well with S63845 across LNCaP95 and VCaP-CR lines. <b>B,</b> All pairings of BH<sub>3</sub> mimetics ranked by average DBSumNeg across LNCaP95 and VCaP-CR lines. <b>C</b> to <b>F,</b> Example drug screen data from A-1331852 paired with S63845 in VCaP-CR (<b>C</b> and <b>D</b>) and LNCaP95 (<b>E</b> and <b>F</b>) cells using CellTiter-Glo to measure response. Cell viability (<b>C</b> and <b>E</b>) and Bliss synergy were calculated for each point. Z-plots depict Bliss synergy score at each concentration (<b>D</b> and <b>F</b>). <b>G,</b> Patient mRNA sequencing data from the SU2C 2019 cohort of patients with mCRPC reveals the expression of <i>AR</i>, <i>BCL2</i>, <i>Bcl-xL</i>, and <i>MCL1</i>. Cohort expression was displayed utilizing GraphPad Prism 10, and data are expressed as fragments per kilobase of transcript per million mapped reads (FPKM).</p>
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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.
