2823 - Patient-Derived Pancreatic Tumor Organoids as a Surrogate to Predict Radiation and Chemotherapy Response in Individual Patients: A Model for Precision Medicine

Z. Keepers, S. Roy, B. Bhandary, F. Carrier, N. Lamichhane, J. K. Molitoris, W. F. Regine Jr, and H. D. Shukla; Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD

Purpose/Objective(s): We investigated 3 patient-derived pancreatic tumor organoids (PTOs) (ID # 8510, 7800 and 11777) response to gemcitabine, FOLFIRINOX, 5 FU and radiation therapy (RT). The aim of this study was to demonstrate that each patient’s tumor organoids responded differently to chemotherapy drugs and RT, and genetic mutations played a role in RT resistance. The combination of chemotherapy followed by RT and the role of cancer stem cells (CSCs) in radiation resistance was also investigated. Materials/

Methods: 3-D Culture of tumor organoids: PTOs were obtained from the NCI and 3D culture was initiated in Matrigel. The mixture (Matrigel and organoids) was then pipetted into the wells of 24-well plates that were pre-warmed overnight and 750 µl of Panc complete media was added to each well with a dome and incubated at 37 ºC with 5 % CO2. Chemotherapy and RT Dose Response: The cultured tumor organoids were allowed to grow for 24 hours. Then, treated with different doses of gemcitabine, 5-fluorouracil, and FOLFIRINOX (0-100 µM) and RT (2-12 Gy). After treatment MTT assay was performed using CellTiter 96 Reagent (Promega) and percentage viability was calculated and the IC-50 doses were determined.
Results: Dose response of patients derived pancreatic tumor organoids to chemotherapy drugs and RT: PTOs were treated with different doses of gemcitabine, FOLFIRINOX, 5 FU and RT and allowed to grow for 7 days. The treatment response of the tumor organoid was determined by MTT assay which measures organoids proliferation. The data has shown significant variation in IC50 dose of chemotherapy drugs and RT required to kill 50 % of tumor organoids. The tumor organoid 8510 exhibited higher tolerance to 5-FU and FOLFIRINOX treatment as compared to 7800 and 11777. We also observed 11777 showed resistance to 12 Gy of RT and the genetic profile of this patients showed mutation in ARID1A & PIM1 genes which could be linked to RT resistance. We further examined effectiveness of chemotherapy and RT alone vs combination treatment of chemotherapy and RT. Interestingly, tumor organoids treated with combination of chemotherapy and RT exhibited significant higher killing as compared to chemotherapy or RT alone. Upregulation of OCT4 and SOX2 in pancreatic cancer stem cells exhibited resistance to radiation treatment: The data demonstrated significant upregulation of SOX2 and OCT4 pancreatic cancer stem cell markers in tumor organoids treated with radiation therapy (RT). The data have shown upregulation of OCT4 and SOX2 (CSC) markers in tumor organoids treated with 4 and 8 Gy of RT, suggesting their role in therapy resistance. The combination of chemotherapy with RT suppressed OCT4 and SOX2 expression.
Conclusion: The data unambiguously suggest that PTOs showed differential sensitivity toward chemotherapy drugs and RT. The combination treatment modality exhibited significant higher killing than individual modality. The upregulation of OCT4 and SOX2, CSC markers in pancreatic tumor could be playing a role in radiation and chemotherapy resistance.