Finally, using a lineage tracing single-cell RNA sequencing (scRNA-seq) dataset based on a Ptf1a-CreER; LSL-KRas-G12D; LSL-tdTomato PDAC mouse model,21 we found that epithelial cells expressing Epcam, Ly6a/Sca-1 and Prom1/CD133 expand from early metaplastic states to full tumour cells (figure 2H,I), supporting the existence of these cells early on and throughout tumour development. This evidence concerns the gene LY6S and neoplasm.