Abstract 5809: Tracking cancer stem cell expression of pancreatic and ampullary cancer organoids in response to chemotherapy

Background: Cancer stem cells (CSCs) have been described to confer resistance and aggressive disease biology in pancreatic ductal adenocarcinoma (PDAC) and ampullary carcinoma (AMPC). Patient derived cancer organoids (PCOs) are an important model of PDAC that maintain the molecular features of advanced disease and have been shown to predict drug response. This study aimed to determine the dynamics of CSC expression on the oligoclonal culture growth of three independent PCOs models.Methods: PCOs were assayed using low volume 10μL microformat in 96 well design (Ibidi, Inc). PCOs were treated with physiologic FOLFIRINOX or gemcitabine + nab-paclitaxel (nab-pac) including single agent controls. Response was assayed by growth using timecourse data from 0h to 72h using high content imaging (Cytation 5). At 72h, the PCOs were stained using four distinct CSC markers (CD44, CD133, CD117, and EpCAM). Images were aligned using thresholded root mean standard deviation of 75μm and tracked for normalized change in longest diameter. At 72h, CSC markers were tracked using % area positive from brightfield region of interest. Response was tracked by effect size Glass’s Delta (GΔ) defined as the difference between the mean of media control and treatment group normalized to standard deviation of media control.Results: PCOs maintained nuclear atypia and high nuclear-chromatin ratios consistent with matured xenografts. AMPC1 showed similar sensitivity with growth arrest by PCO Δ diameter for gem + nab-pac (mean = +2.2%, GΔ = 1.29) and FOLFIRINOX (mean = 0.0%, GΔ = 1.33). AMPC1 had CSC enrichment for CD44 after treatment with nab-pac (GΔ = 0.93), CD133 expression after treatment with gem + nab-pac (GΔ = 0.75), CD117 after treatment with nab-pac treatment (GΔ = 0.80), and EpCAM after treatment with gem + nab-pac (GΔ = 0.78). In AMPC1, interquartile analysis revealed increased CSC expression conferred reduced growth for CD133 (+72% v. 37%, p<0.005) and CD117 (+81% v. +25%, p<0.005). Normalized Δ diameter across PDAC PCOs revealed PDAC1 had reduced sensitivity to gem + nab-pac (mean = +16.0%, GΔ = 1.2) vs. PDAC2 (Mean = 2.1%, GΔ = 1.65). PDAC1 had CSC enrichment with increased % area of CD44+ after treatment with gem + nab-pac (GΔ = 1.13). In PDAC2, interquartile analysis revealed increased CSC expression conferred decreased growth rate for CD133 (+65% v. +36%, p< 0.005) and CD117 (+75% v. +38%, p<0.005).Conclusions: PDAC and AMPC PCOs reveal oligoclonal expression of CSC markers within a population. Increased CSC expression for CD133 and CD117 within a population consistently revealed decreased growth within an organoid population. CSC expression (CD44, CD133, CD117, and EpCAM) was found to be enriched under therapeutic challenge with gem and nab-pac containing chemotherapy. This work supports the oligoclonal and dynamic nature of CSCs for pancreaticobiliary cancers in response to therapeutic challenge.Citation Format: Eleanor Riedl, Austin Stram, MD Shahadat Hossan, Ethan S. Lin, Luke Koeppel, Jamie Warner, Sam Lubner, Stephanie McGregor, Wei Zhang, Jeremy Kratz. Tracking cancer stem cell expression of pancreatic and ampullary cancer organoids in response to chemotherapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5809.