Abstract A012: Development of a translational tumoroid-organoid platform revealing tumor-specific radiosensitization in rectal cancer using matched patient-derived models
Authors: Zambare Wini , Wu Chao , Kalvin Hannah , Huang Hanchen , Yoder Sara , Del Latto Michael , Kierstead Maria , Meguro Satoru , Chen Xi Steven , Gonen Mithat , Smith J. Joshua , Romesser Paul B. 
Published: January 2025

Abstract
Background: Radiation therapy in rectal cancer treatment is limited by variable tumor responses among patients and harmful effects on normal tissues. We developed a translational human tumoroid-organoid platform to assess novel tumor-specific strategies for radiation sensitization using matched patient-derived models. Methods: Fifteen rectal cancer-derived tumoroids and three matched normal tissue-derived organoids were established from patients, representing primary tumors, metastases, and recurrences. Four tumoroids were derived from a single patient, encompassing different disease stages: primary tumor and splenic metastasis (pre-progression), and rectal and vaginal recurrences (post-progression). To evaluate tumor-specific radiation sensitizers, both tumoroids and their matched normal organoids were treated with 5-fluorouracil (5-FU), one of four DNA damage repair inhibitors (DDRis; ATMi, DNA-PKi, PARPi, or ATRi), or a DMSO control. Following treatment, samples were irradiated, and cell viability was measured. We assessed intrinsic radiation sensitivity under control conditions and radiosensitizer efficacy using a linear regression model with log-transformed cell viability as the outcome. Whole-exome sequencing characterized the mutation profiles of the tumoroids. Results: Intrinsic radiosensitivity was heterogeneous among tumoroids, with a 10–28% decrease in cell growth per unit increase in radiation dose. Critically, when comparing tumoroids to their matched normal organoids, we observed greater sensitization in tumoroids across all cases and for all DDRis, demonstrating tumor-specific radiosensitization. The most potent radiosensitizer relative to DMSO was DNA-PKi in 7 tumoroids, ATMi in 4 tumoroids, and PARPi in 1 tumoroid. Tumoroids derived after disease progression exhibited increased resistance to radiation and a diminished degree of sensitization with DDRi treatment compared to pre-progression tumoroids. Despite variations in radiation sensitivity and DDRi responses, the genetic profiles of the tumoroids remained largely unchanged. Conclusion: We developed a translational ex vivo tumoroid-organoid platform using matched patient-derived models to test tumor-specific radiation sensitizers in rectal cancer. This platform allowed us to determine tumor-specific sensitization by directly comparing tumoroids with matched normal organoids, demonstrating greater sensitization in tumoroids. Our findings highlight the potential of this platform to uncover precise, tumor-selective treatment options, improve patient responses, reduce toxicity, and address resistant tumors in patients with disease progression.
Citation Format: Wini Zambare, Chao Wu, Hannah Kalvin, Hanchen Huang, Sara Yoder, Michael Del Latto, Maria Kierstead, Satoru Meguro, Xi Steven Chen, Mithat Gonen, J. Joshua Smith, Paul B. Romesser. Development of a translational tumoroid-organoid platform revealing tumor-specific radiosensitization in rectal cancer using matched patient-derived models. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr A012.