Abstract
BackgroundPancreatic cancer stem cells (CSCs) represent a small subpopulation of pancreatic cancer cells that have the capacity to initiate and propagate tumor formation. However, the mechanisms by which pancreatic CSCs are maintained are not well understood or characterized.MethodsExpression of Notch receptors, ligands, and Notch signaling target genes was quantitated in the CSC and non-CSC populations from 8 primary human pancreatic xenografts. A gamma secretase inhibitor (GSI) that inhibits the Notch pathway and a shRNA targeting the Notch target gene Hes1 were used to assess the role of the Notch pathway in CSC population maintenance and pancreatic tumor growth.ResultsNotch pathway components were found to be upregulated in pancreatic CSCs. Inhibition of the Notch pathway using either a gamma secretase inhibitor or Hes1 shRNA in pancreatic cancer cells reduced the percentage of CSCs and tumorsphere formation. Conversely, activation of the Notch pathway with an exogenous Notch peptide ligand increased the percentage of CSCs as well as tumorsphere formation. In vivo treatment of orthotopic pancreatic tumors in NOD/SCID mice with GSI blocked tumor growth and reduced the CSC population.ConclusionThe Notch signaling pathway is important in maintaining the pancreatic CSC population and is a potential therapeutic target in pancreatic cancer.
Highlights
Pancreatic cancer is the fourth most common cause of cancerrelated death in the United States despite being the 10th most common cancer diagnosis [1]
We evaluated the role of the Notch pathway in maintaining the cancer stem cells (CSCs) population and its effects of inhibition in pancreatic tumor growth
Using primary human pancreatic cancer xenografts from 8 different patient tumors we evaluated expression levels of Notch signaling pathway components in cancer stem cells compared to bulk tumor cells
Summary
Pancreatic cancer is the fourth most common cause of cancerrelated death in the United States despite being the 10th most common cancer diagnosis [1]. Cancer stem cells were first isolated in myeloid leukemia [2] and were shown to share stem cell properties such as potential for self-renewal and the ability to differentiate and proliferate. Pancreatic cancer stem cells (CSC) were first isolated from human pancreatic cancers using the marker profile ESA+/CD44+/CD24+ [10]. These marker positive CSCs were able to form tumors in NOD/SCID mice that appeared histologically similar to the primary tumor, suggesting multipotency with reconstitution of the various tumor cell types. In vitro evidence for a stem cell phenotype such as self-renewal was demonstrated by the ability to form tumor spheres in vitro in contrast to ESA-/CD44-/CD24- cells which could not. The mechanisms by which pancreatic CSCs are maintained are not well understood or characterized
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