Abstract
Simple SummaryPancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancer types with the quasi-mesenchymal (QM) subtype of PDAC having the worst prognosis. De-differentiation of the ductal tumor cells to a mesenchymal phenotype occurs as a result of epithelial–mesenchymal transition (EMT), a process associated with the acquisition of stem cell traits. While QM tumor cells are highly metastatic and drug-resistant, their increased plasticity opens a window of opportunity for trans-differentiation into non-malignant pancreatic cells. In this study we compared established PDAC-derived cell lines of either epithelial (E) or QM phenotype for their potential to be differentiated to pancreatic endocrine cells. We found that QM cells responded more strongly than E cells with transcriptional activation of a pancreatic progenitor or pancreatic β cell-specific program. Our results bear strong implications for a novel type of targeted therapy, namely EMT-based trans-differentiation of highly metastatic PDAC cells in vivo to non-malignant endocrine cells.Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and therapy-resistant cancer types which is largely due to tumor heterogeneity, cancer cell de-differentiation, and early metastatic spread. The major molecular subtypes of PDAC are designated classical/epithelial (E) and quasi-mesenchymal (QM) subtypes, with the latter having the worst prognosis. Epithelial–mesenchymal transition (EMT) and the reverse process, mesenchymal-epithelial transition (MET), are involved in regulating invasion/metastasis and stem cell generation in cancer cells but also early pancreatic endocrine differentiation or de-differentiation of adult pancreatic islet cells in vitro, suggesting that pancreatic ductal exocrine and endocrine cells share common EMT programs. Using a panel of PDAC-derived cell lines classified by epithelial/mesenchymal expression as either E or QM, we compared their trans-differentiation (TD) potential to endocrine progenitor or β cell-like cells since studies with human pancreatic cancer cells for possible future TD therapy in PDAC patients are not available so far. We observed that QM cell lines responded strongly to TD culture using as inducers 5′-aza-2′-deoxycytidine or growth factors/cytokines, while their E counterparts were refractory or showed only a weak response. Moreover, the gain of plasticity was associated with a decrease in proliferative and migratory activities and was directly related to epigenetic changes acquired during selection of a metastatic phenotype as revealed by TD experiments using the paired isogenic COLO 357-L3.6pl model. Our data indicate that a QM phenotype in PDAC coincides with increased plasticity and heightened trans-differentiation potential to activate a pancreatic β cell-specific transcriptional program. We strongly assume that this specific biological feature has potential to be exploited clinically in TD-based therapy to convert metastatic PDAC cells into less malignant or even benign cells.
Highlights
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with an extremely poor prognosis (5-year survival ~7.7%) [1]
Unlike the E cell lines both QM lines were negative for Claudin-4 (CLDN4), a tight junctional protein and potent inhibitor of invasion and a metastatic phenotype of pancreatic cancer cells [50]
MRNA levels of ECAD and those of additional epithelial markers, CLDN7 and EpCAM/CD326 were hardly detectable in MIA PaCa-2, intermediate in PANC-1 and high in COLO 357 cells (Table S2)
Summary
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with an extremely poor prognosis (5-year survival ~7.7%) [1]. A series of genomic and transcriptomic studies have demonstrated that human PDAC is not a homogeneous disease but is composed of subtypes with different functional behaviors in preclinical models and differences in clinical studies with respect to survival and response to drug treatment [3,4]. Single-cell transcriptomic analysis has revealed an unanticipated high heterogeneity of pancreatic cancers and demonstrated that QM cells are even present in E tumors [5]. These cells have been associated with systemic metastasis, escape from standard therapy and tumor recurrence [4,6]
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