Abstract 220: Thresholding response assessment in biliary tract cancer organoids to inform sensitivity to chemotherapy across molecular subtypes
Authors: Riedl Eleanor , Stram Austin , Hossan Md Shahadat , Lin Ethan Samuel , Warner Jamie , Koeppel Luke , Kratz Jeremy D. 
Published: March 2024

Abstract
Background: Cholangiocarcinoma (CCA) remains a highly morbid cancer for which accurate models. Patient-derived cancer organoid (PCOs) have been generated in CCA, however their utility in clinical prediction has not been validated. Z’ factoring often fails in assessing CCA organoid response. Prior analysis for organoid response has shown an effect size by Glass’s Delta (GΔ) of ≥1.25 in growth inhibition is predictive of clinical response. Here, we present subclonal organoid response across a diverse set of CCA models in response to therapy by growth and organoid level viability response.
Methods: PCOs were expanded from the NCI’s Patient-Derived Model Repository (PDMR), tissue biopsy, and rapid autopsy. Organoid response was tracked from growth using Z-stacked high content imaging (Cytation5) with endpoint at 144h and stained using established viability markers, Caspase-3/7 (C3/7) and ToPro3. Treatment groups included media control, positive control of cycloheximide 200uM continuous, gemcitabine (gem) 10uM 24h, cisplatin (cis) 5uM 48h, combination gem+cis, and FGFR2 inhibitor futibatinib (futi) 300nM continuous.
Results: Across models, PCO growth directly correlated with Z’ factor thresholding (R= 0.868). NCI PDMR organoids, CK11523 and CK10519 are IDH1mutant (mt), and both showed superior response to gem when compared to cis by growth (gem GΔ 1.18 and 0.44 v. cis GΔ 0.11 and 0.23) and C3/7 (gem GΔ 3.25 and 2.34 v. cis GΔ 1.46 and 0.33). BRCA1mt CCA was found to achieve modest growth inhibition with gem and gem+cis (GΔ 1.09 and 1.17) and yet significant increase in C3/7 (gem GΔ 1.68 and gem+cis GΔ 1.36) and ToPro3 (gem GΔ 1.65 and gem+cis GΔ 1.82). Despite this result, the patient developed early clinical recurrence after neoadjuvant gem+cis chemotherapy (&lt;3 months). FGFR2-HPGDS fusion CCA achieved no meaningful difference in growth response with gem+cis (GΔ 0.94) or futi (GΔ 0.36). These findings were consistent with the clinical outcome of primary chemotherapy resistance and progression on futi. However, we observed increase in C3/7 positivity with both gem+cis (GΔ 2.11) and futi (GΔ 1.37).
Conclusions: Primary resistance to both targeted and chemotherapy remains a formidable barrier to therapeutic development in CCA. While growth inhibition remains a validated marker of clinical response, further work is needed to understand thresholds for C3/7 and ToPro3 across physiologic drug dosing. This is the first report of modeling the novel FGFR2-HPGDS fusion CCA in organoids. Ongoing work is evaluating therapeutic sensitivity across prospective specimens of CCA in support of establishing thresholding for response to apoptosis (C3/7) and necrosis (ToPro3).
Citation Format: Eleanor Riedl, Austin Stram, Md Shahadat Hossan, Ethan Samuel Lin, Jamie Warner, Luke Koeppel, Jeremy D. Kratz. Thresholding response assessment in biliary tract cancer organoids to inform sensitivity to chemotherapy across molecular subtypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 220.