MKI67 and neoplasm: RNA in situ hybridization of surgical primary tumor samples for KRT19 (a marker of neoplastic PDAC cells), TFF3 (a marker of secretory cells and of the classical PDAC subtype), S100A2 (a marker of the basal-like PDAC subtype), and MKI67 (a proliferation marker) showed higher TFF3 expression in the classical subtype and higher S100A2 expression in the basal-like subtype (Fig. 3g, h), confirming that PDAC organoids reflect the original patient tumors.