Abstract B55: Patient-Derived Organoids model time-dependent sensitivities to PARP inhibitors in patients with metastatic colorectal cancer
Authors: Mastropaolo Maria , Kuo Helen , Nguyen John , Rowdo Florencia Madorsky , Capuano Jared , Moyer Jenna , Martin M. Laura , Hall Julianne , Elemento Olivier 
Published: December 2022

Abstract
Background: Poly (ADP-ribose) polymerase inhibitors (PARPi) have been approved as monotherapy and combination therapy for BRCA-mutated breast, ovarian, and prostate cancer and it is proposed that they may be effective for other BRCA-mutated cancer as well. However, recent clinical trials show inconsistent efficacy of PARPi on BRCA-mutated cancers, partially due to imperfect biomarker definition and unknown resistance mechanism. BRCA status alone may not be a good indicator for PARPi responsiveness as many proteins are involved in the homologous recombination (HR) pathway, which is why this experiment raises the question of whether time plays a role in tumor drug sensitivity. Patient-derived tumor organoids (PDTOs) can be used to study the pharmacogenomics between PARPis and HR deficient cancer. PDTOs are emerging ex vivo cancer models used for precision medicine because they harbor the mutational landscape of primary tumors. The common pipeline for organoid preclinical research includes confirming mutation profile, performing drug screening, and proposing clinically relevant candidates. The goal of this experiment was to model if the responses of patient-derived colorectal cancer organoids with BRCA gene deletion and TP53, SMAD4, and KRAS gene mutations to the PARPi talazoparib and olaparib differ depending on time.Methods: Patient sample: Colorectal: rectal cancer with BRCA1 gene deletion. Mutations in ⦁ KRAS p.Gly12Val ⦁ TP53 p.Arg175His ⦁ SMAD4 p.Arg361Cys + control: Puromycin 2 ug/mL - control: DMSO PARPi: talazoparib and olaparib In a 96 well plate, 1500 cells per well were plated in 10uL of a media/matrigel mixture and 100 uL of additional media were added to each well. The plate was put in the incubator at 37 C for 48 hours. The PARPi talazoparib and olaparib were then added after a serial dilution at max 50 uM concentration. The plates with the drugs (additional 100uL media with 2X drugs) were put in the incubator at 37 C for 120 hours. The plate for timepoint 1 was then read using the viability assay called Cell Titer Glo 3D. The next timepoint was taken after 168 hours using the same method. In addition, cell viability was measured by high content imaging which is being developed at EIPM.Results: Patient-Derived organoids were sensitive to talazoparib at hour 120 and hour 168 (IC50 1.6 and 1.9 respectively). Patient-derived organoids were not sensitive to olaparib at any time point tested and did not yield a meaningful IC50.Conclusion: The sensitivity of patient-derived colorectal cancer organoids with BRCA gene deletion and TP53, SMAD4, and KRAS gene mutations to the PARPi talazoparib and olaparib did not significantly differ depending on time. However, organoids were more sensitive to talazoparib than to olaparib. These results can guide which PARPi should be used in similar ex vivo experiments to yield meaningful results to eventually lead to successful clinical treatments for patients.
Citation Format: Maria Mastropaolo, Helen Kuo, John Nguyen, Florencia Madorsky Rowdo, Jared Capuano, Jenna Moyer, M. Laura Martin, Julianne Hall, Olivier Elemento. Patient-Derived Organoids model time-dependent sensitivities to PARP inhibitors in patients with metastatic colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B55.