Abstract 27: Orthotopic tumor models using luciferized patient-derived organoids for investigating EGFR-MAPK pathway inhibition in colorectal and pancreatic cancer

Abstract The EGFR-MAPK signaling pathway is frequently activated in cancers, particularly due to KRAS gain-of-function mutations. Certain types, such as pancreatic ductal adenocarcinoma (PDAC) with KRAS mutations and cholangiocarcinoma with FGFR2 fusions, show dependency on EGFR. Recent studies demonstrate promising outcomes in metastatic colorectal cancer by combining an irreversible KRASG12C inhibitor with an EGFR inhibitor. To explore therapeutic benefits across tumor types, we analyzed the expression of EGFR and co-receptors (ERBB) in TCGA samples and CCLE models with different KRAS mutations. We also verified the reliance on ERBB receptors using DepMap data. Patient-derived organoid (PDO) models from PDAC, colorectal cancer (CRC), and CRC liver metastases were utilized to develop orthotopic tumor models. These PDO lines were characterized through mutational profiling, cell signaling analysis, RNA-sequencing, and whole exome sequencing, providing insights into their molecular features. Higher EGFR expression levels at both protein and RNA levels were observed in specific CRC PDO models, consistent in in-vitro PDO models and in-vivo PDO-derived Xenograft (PDOX) tissues from subcutaneous implantation in immunocompromised mice. Additionally, the PDO models were evaluated for sensitivity to standard of care (SOC) drugs and EGFR inhibitors, revealing EGFR expression-independent and tumor type-dependent sensitivities (e.g., Afatinib IC50: PDAC (128nM+/-123) vs CRC (2776nM+/-3099)). Surface expression levels of ERBBs were measured in in-vivo PDOX tissues to assess the comparative use case for targeting the EGFR pathway via inhibition or antibody-drug conjugate (ADC) molecules. Furthermore, we generated and validated stable tumoroid models expressing firefly luciferase in PDOs derived from primary CRC, CRC metastasis to the liver, and primary PDAC. To further validate the potential for in-vivo models, orthotopic tumor models were established in immunocompromised mice for each PDO line, monitoring tumor burden using bioluminescence imaging. Correlation with MRI and ultrasound imaging was conducted for PDAC and liver tumor burden, respectively, with significant correlation observed. Overall, this study aims to enhance understanding of tumor biology and response to treatment through the development and validation of PDO-based orthotopic models, with future work involving validation of EGFR inhibitors targeting the pathway and ADCs based on ERBBs targeting tumor cells expressing these proteins. In vivo luciferase reactivation in our models will allow us to dissect the mechanisms of resistance to these agents using physiologically relevant tumor models and single-cell RNA-sequencing analysis. Citation Format: Krishna S. Tummala, Milind Chalishazar, Minilik Angagaw, Ali Savadipour, Qingyun Yan, Cui Long, Mark Buchanan, Panagiotis N. Lalagkas, Eric Muise, Lan Chen, Kuoyuan Cheng, Eunsil Park, Jennifer Piesvaux, Erica Leccese, Brian Long, Nicolas Solban. Orthotopic tumor models using luciferized patient-derived organoids for investigating EGFR-MAPK pathway inhibition in colorectal and pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 27.