HER2 expression and responsiveness to HER2 inhibition in patient-derived gastric cancer organoids. (A) Immunofluorescence of HER2 expression (red) in huTGOs. Dose-response curves generated by using (B) huTGO1, (C) huTGO2, (D) huTGO4, and (E) huTGO6 organoid lines in response to epirubicin, oxaliplatin, or 5-FU with or without HER2 inhibitor (HER2I). Each assay was run in triplicate for each individual organoid line.