Authors: Lisa-Marie Philipp, Axel Künstner, Anne-Sophie Mehdorn, Charlotte Hauser, Jan-Paul Gundlach, Olga Will, Sören Franzenburg, Hendrike Knaack, Udo Schumacher, Hauke Busch, Susanne Sebens
Pancreatic ductal adenocarcinoma (PDAC) is mostly diagnosed at advanced or even metastasized stages limiting patient´s prognosis and overall survival. Metastasis requires strong cancer cell plasticity and high tumor cell heterogeneity implying phenotypic switching, notably, Epithelial-Mesenchymal-Transition (EMT) being associated with the gain of cancer stem cell (CSC) properties, in response to changing environments. To analyze whether CSC-properties are related to distinct EMT-phenotypes and if this CSC-EMT axis impacts malignancy-associated properties, this study aimed at characterizing mesenchymal-like and epithelial PDAC cell variants, with the focus on CSC populations. Single-cell cloning of PDAC cells revealed CSC (Holoclone) and non-CSC (Paraclone) clones from both mesenchymal-like (Panc1) and epithelial (Panc89) cells. Comparatively analyzing parental Panc1 and Panc89 as well as related Holo- and Paraclone cells, it was found that Panc1 and Panc89 cell variants exhibit differences in their colony formation ability, reflecting the potential to self-renew, as well as distinct transcriptional CSC and EMT signatures. While Panc1 cell variants show increased signatures of EMT, Panc89 cell variants exhibit increased self-renewal capacity and CSC signatures. Isolated Panc1 Holoclone cells show a mesenchymal phenotype dominated by high expression of the CSC marker Nestin, while Panc89 Holoclone cells exhibit a Sox2-dominated epithelial stemness phenotype. Functional analysis revealed decreased cell growth for Panc1 cell variants compared to Panc89 cell variants, while response to chemotherapy was overall higher Panc89 cell variants. Panc1 Holoclones show the weakest response to treatment, while Panc89 Holoclones showed the strongest affection to therapy. Invasion assays presented Panc1 cell variants to have an increased invasion potential compared to Panc89 cell variants, while Panc89 cell populations show stronger migration ability. Further detailed, Panc1 Holoclone cells are highly invasive in a mesenchymal-like invasion manner, while Panc89 Holoclone cells show pronounced cell migration in clusters. In vivo, Panc1 and Panc89 cell variants essentially differ with respect to their metastatic capacity, as Panc1 and Panc89 Holo- and Paraclone tumors varied regarding number and size of metastases formed as well as organ manifestation, leading to different survival outcomes. Overall, these data support the view of EMT-related plasticity and heterogeneity within cancer (stem) cells in PDAC, differentially impacting metastatic propensities.