Studies on the behaviour of human pancreatic carcinoma cell lines, with particular reference to stem cells

Abstract

Stem cell therapy represents a potential -cell replacement strategy in diabetes and a pancreatic cancer (PC) stem cell is an attractive therapeutic target in this dire disease. However, a normal stem cell remains unidentified and proposed malignant stem cell markers await verification. Using human PC cell lines as an in vitro tumour model and human archival tissue, and proposed stem cell markers identified in other normal tissues and tumours, we attempted to identify a PC stem cell. These markers included high aldehyde dehydrogenase activity, the Side Population (SP) phenotype, and the cell surface markers CD44 and CD133. These markers were evaluated by flow cytometry, immunohistochemistry (IHC) and reverse-transcriptase PCR. Positive populations were isolated from cell lines using fluorescence activated cell sorting (FACS) and subjected to in vitro colony-forming assays to assess their relative proliferative capacities. The presence of a differentiation hierarchy was investigated in one line to test the assumptions of the tumour model. No single marker or combination thereof consistently identified a highly clonogenic fraction, though some differences in clonogenicity were seen. Furthermore, the dye Hoechst 33342 was found to inhibit proliferation, potentially inducing artefactual differences in clonogenicity between SP and non-SP cells. Recently, expression of trefoil factor family peptide (TFF) 3, a gastrointestinal motogen, was reported in human islets of Langerhans. Furthermore, this peptide was reported as a -cell mitogen in vitro, and a potential agent of functional -cell production. We employed isotopic in situ hybridization and IHC to evaluate TFF expression in normal human pancreas, chronic pancreatitis and PC. Expression of all three TFFs was increased in inflammation and cancer, and TFF3 mRNA was occasionally detected in islets. The motogenic activity of TFF peptides was investigated using in vitro wound healing and invasion assays on human PC lines and primary stellate cell cultures. TFF2 was seen to enhance migration in PC lines at high concentrations.