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The development of patient-derived tumor organoids (TOs) from an epithelial ovarian cancer tumor obtained at the time of primary or interval debulking surgery has the potential to play an important role in precision medicine. Here, we utilized TOs to test front-line chemotherapy sensitivity and to investigate genomic drivers of carboplatin resistance. We developed six high-grade, serous epithelial ovarian cancer tumor organoid lines from tissue obtained during debulking surgery (two neoadjuvant-carboplatin-exposed and four chemo-naïve). Each organoid line was screened for sensitivity to carboplatin at four different doses (100, 10, 1, and 0.1 µM). Cell viability curves and resultant EC50 values were determined. One organoid line, UK1254, was predicted to be resistant to carboplatin based on its EC50 value (50.2 µM) being above clinically achievable Cmax. UK1254 had a significantly shorter PFS than the rest of the subjects (p = 0.0253) and was treated as a platinum-resistant recurrence. Subsequent gene expression analysis revealed extensively interconnected, differentially expressed pathways related to NF-kB, cellular differentiation (PRDM6 activation), and the linkage of B-cell receptor signaling to the PI3K–Akt signaling pathway (PI3KAP1 activation). This study demonstrates that patient-derived tumor organoids can be developed from patients at the time of primary or interval debulking surgery and may be used to predict clinical platinum sensitivity status or to investigate drivers of carboplatin resistance.

Objectives: Ovarian carcinosarcoma is an unusual and aggressive form of ovarian cancer. Due to the rarity of the disease, little empirical evidence exists about the efficacy of different chemotherapeutic regimens. Thus, the objective of this research is to establish and validate patient-derived carcinosarcoma xenograft and organoid models and assess the ability these models to predict response to chemotherapy. Methods: A patient-derived xenograft (PDX) was established during an optimal (R=0cm) upfront debulking surgery. Fresh tumor tissue was implanted subcutaneously in an 8-week-old NOD.Cg-Prkdcscid (NSG) mouse. Tumor growth was closely monitored until volume exceeded 2.0 cm3. The mouse was sacrificed and tumor tissue was harvested. A portion of the tissue was digested with highly purified collagenase I and collagenase II for establishment of in vitro monolayer and tissue organoid cell lines. IHC and flow cytometry were performed to validate the harvested PDX tumor and the in vitro cell line using FLEX monoclonal anti-human cytokeratin, high molecular weight, clone 34E12. Dose response curves were generated to assay the effects of five standard-of-care cytotoxic chemotherapy regimens (paclitaxel, carboplatin, gemcitabine, doxorubicin, and topotecan) and one experimental regimen (artesunate) after 96hours of incubation. Drug sensitivities were compared to other established commercially available platinum-sensitive ovarian carcinoma cells (UWB1.289), a model of acquired platinum-resistance (UWB1.289-CR), and to the patient’s clinical response to chemotherapy. Results: Palpable tumor tissue was harvested 14 weeks after implantation. The harvested tissue reveals strong expression of high molecular weight cytokeratin. Successful propagation of the patient’s malignancy in vitro was confirmed via flow cytometry. Dose response curves of cytotoxic chemotherapy reveals a relatively high resistance to carboplatin (IC50 44.6uM), gemcitabine (IC50 307.1nM), and topotecan (IC50 117.4nM) but sensitivity to paclitaxel (IC50 2.9nM), doxorubicin (IC50 59.7nM), and artesunate (IC50 1.8uM) when compared to established ovarian cancer cell lines. The patient recurred approximately 4 months after optimal debulking surgery despite treatment with adjuvant carboplatin/paclitaxel, thus classifying her disease as clinically platinum refractory. Conclusions: This is the first ovarian carcinosarcoma established in a PDX model and as an organoid cell line. Notably, the model predicted clinical response. The IC50 of the carcinosarcoma in vitro model was 44.6uM compared to 25.9uM in our established acquired platinum-resistant cell line and the patient had platinum-refractory disease. Additional insight into the intrinsic platinum resistance of this tumor may be gleaned from RNA and whole-exome sequencing that is currently in process. Citation Format: Joseph R. McCorkle, Brian T. Burgess, Anthony B. McDowell, Jodi DeJohn, Christopher P. DeSimone, Frederick R. Ueland, Jill M. Kolesar, Justin W. Gorski. Development of the first ovarian carcinosarcoma patient-derived xenograft and tissue organoid model to predict clinical response to chemotherapy [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B22.