Mio Takahashi

High-Throughput Drug Screening of Clear Cell Ovarian Cancer Organoids Reveals Vulnerability to Proteasome Inhibitors and Dinaciclib and Identifies AGR2 as a Therapeutic Target

Abstract There are currently no effective treatments available for clear cell ovarian cancer (CCC). In this study, we aimed to identify effective drugs for CCC through high-throughput drug screening (HTDS) using ovarian cancer organoids and determine novel therapeutic targets based on the biological characteristics of CCC through omics analysis. An ovarian cancer organoid biobank was established, and HTDS was conducted using CCC organoids based on libraries of 361 and 4,560 compounds. The efficacy of the identified drugs was verified in in vitro and in vivo experiments using a patient-derived organoid xenograft mouse model. Transcriptome analysis was performed to identify genes related to the pathways targeted by the identified drugs in CCC and to assess their potential as therapeutic targets. Proteasome inhibitors and dinaciclib were extracted using HTDS and shown to inhibit tumorigenesis in vitro and in vivo. CCC, like multiple myeloma, exhibited activated endoplasmic reticulum (ER) stress and unfolded protein response (UPR), and treatment with proteasome inhibitors further enhanced ER stress and UPR, ultimately leading to cell death. Transcriptome analysis identified anterior gradient-2 (AGR2) as a key gene involved in UPR in CCC. CRISPR knockout of AGR2 suppressed cell proliferation, increased sensitivity to proteasome inhibitors, and reversed platinum resistance in CCC. AGR2 knockout also upregulated Schlafen 11, contributing to platinum sensitivity. ER stress and the UPR are activated in CCC, and proteasome inhibitors disrupt this balance, ultimately leading to cell death. AGR2 may serve as a potential therapeutic target in CCC. Significance: Proteasome inhibitors and dinaciclib are identified as effective drugs for CCC. CCC has a high basal UPR, and proteasome inhibition may disrupt this balance. AGR2 is involved in the UPR of CCC, and inhibiting AGR2 further enhances the UPR and confers platinum sensitivity, making it a potential therapeutic target.

Efficacy and safety of olaparib maintenance monotherapy for Japanese patients with platinum-sensitive relapsed ovarian, fallopian tube, and primary peritoneal cancer

Olaparib maintenance therapy for platinum-sensitive relapsed ovarian cancer has been approved in Japan since April 2018. Here, we report the experience administering this therapy in our hospital, with the aim of evaluating efficacy and safety in the Japanese population. The study included 52 patients with platinum-sensitive relapsed ovarian, fallopian tube, and primary peritoneal cancer. All patients started olaparib at a dose of 300 mg twice daily. Information about treatment efficacy and adverse effects was collected retrospectively from medical records. Median age was 58 years old (range: 33-80), and 82.7% of the patients were diagnosed with high-grade serous carcinoma. Sixteen patients (30.8%) possessed the BRCA1/2 pathogenic variant (15 germline and 1 tissue), 3 (5.8%) possessed variants of unknown significance (2 germline and 1 tissue), 16 (30.8%) possessed wild type, and 17 (32.7%) were not analyzed. Median progression-free survival was 15.3 months (95% CI 9.0-21.6). Patients with BRCA1/2 pathogenic variants showed significantly longer PFS than patients with wild-type BRCA1/2 (p = 0.007). Disease progression caused 34 cases to discontinue olaparib. Eighteen (34.6%) individuals exhibited ≥ grade 3 anemia, although they recovered in response to appropriate management. One patient discontinued olaparib because of prolonged renal dysfunction. Another patient presented with grade 3 fatigue, but recovered after 2 weeks of interruption and continued olaparib treatment. Olaparib maintenance therapy for platinum-sensitive recurrent ovarian cancer in the Japanese population is sufficiently safe and no less effective than reports from previous studies.