Abstract A21: Utilizing endoscopic-derived gastric cancer organoids for personalized neoadjuvant chemotherapy

Introduction: Patient-derived organoids (PDOs) have become attractive tools for genetic studies, biomarker identification, drug screening, and preclinical evaluation of personalized medicine strategies. Previously, we created gastric cancer PDOs from esophagogastroduodenoscopy (EGD) biopsy specimens. As a continuation of our previous work, we sought to optimize methods for creating EGD-derived PDOs for drug sensitivity testing within clinically actionable time constraints. Methods: We previously established a standard operating protocol for creating PDOs from EGD specimens of patients with gastric cancer. To optimize the development of PDOs, we enrolled patients with gastric adenocarcinoma undergoing EGD at Markey Cancer Center. During diagnostic EGDs, additional research biopsies were collected for creation of gastric cancer PDOs and placed in ice-cold organoid medium. We employed different dissociation methods based on the texture of the biopsy tissues. Briefly, soft tissues were washed and isolated in a chelating solution to release the glands, while the hard tissues were digested with collagenase and dispase to release epithelium. Glands or epithelia cells were collected, resuspended in BME (basement membrane extract), and plated in 2 wells of 24-well chambers. On day 4-6, PDOs were dissociated and passaged using manual pipetting. For passage 2 on day 9-11, PDOs were isolated into smaller and uniform-sized PDOs or single cells with both mechanical and enzymatic (TripLE Express) dissociation and plated in a 96-well plate at 10uL (500-1000 cells)/well. To test drug sensitivities, PDOs were treated on day 12 with current standard-of-care cytotoxic combination chemotherapies (e.g., FLOT, ECF, FOLFIRI, and FOLFOX) or solvent control. We tested concentrations determined by the Cmax and AUC of each drug associated with a single highest recommended dose in drug product label. We performed LIVE/DEAD assay on CellInsight CX7 High-Content Screening (HCS) Platform (ThermoFisher) and CellTiter Glo luminescent cell viability assay consecutively to measure response of PDOs to chemotherapy regimens. Result: Consistent with our prior experience, we successfully developed EGD-derived gastric cancer PDOs from patients undergoing diagnostic EGD. Using our modified technique for PDO creation and expansion, we obtained sufficient and uniform-sized PDOs at the second passage on day 10 and then treated these PDOs with current standard-of-care chemotherapy regimens to predict