Retinoic acid can induce markers of endocrine transdifferentiation in pancreatic ductal adenocarcinoma: preliminary observations from an in vitro cell line model.
OBJECTIVE
The pancreatic ductal adenocarcinoma (HPAF) cells have a multipotent stem cell potential. It was hypothesised that all-trans-retinoic acid (atRA) can induce transdifferentiation of these cells into cells with an endocrine phenotype.


METHODS
To explore this hypothesis, an in vitro system of cells was established. Some cells were treated with atRA at concentrations of 100 nmol/l (non-apoptosis-inducing) and 5 micromol/l (apoptosis-inducing) and harvested. Cells were examined for cell cycle kinetics, apoptosis (terminal deoxynucleotidyl transferase assay and p53 protein expression) and immunomorphological features of redifferentiation (MUC1 and DUPAN-2) and endocrine transdifferentiation (insulin, somatostatin, glucagon, neurone-specific enolase) by using immunoperoxidase staining methods. Levels of insulin, transforming growth factor (TGF) beta2, TGFalpha and epidermal growth factor receptor (EGFR) were measured by enzyme-linked immunosorbent assay (ELISA). The vehicle-treated cells served as a control group.


RESULTS
When compared with untreated cells, cells treated with 100 nmol/l and 5 micromol/l atRA were observed to show (1) decreased proliferative activity (cpm) as indicated by decreased incorporation of thymidine labelled with hydrogen-3; (2) cell cycle arrest; (3) increased apoptotic activity associated with p53 protein overexpression; (4) upregulated expression of the transdifferentiation and redifferentiation markers; (5) morphological changes indicative of transdifferentiation (increased cell size and appearance of dendrites); (6) decreased production of EGFR; (7) upregulation of TGFalpha and TGFbeta2; and (8) increase in basal and glucose-induced insulin secretion.


CONCLUSIONS
Functional endocrine transdifferentiation can be induced in HPAF lines by atRA. Further investigations are mandated to explore the underlying mechanisms of this transdifferentiation and to explore its in vivo extrapolation.
El-Metwally
T H
TH
Department of Medical Biochemistry, Faculty of Medicine, Assiut University, Assiut, Egypt. thelmetwally@hotmail.com
Hussein
M R
MR
Abd-El-Ghaffar
S Kh
SKh
Abo-El-Naga
M M
MM
Ulrich
A B
AB
Pour
P M
PM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D021441:Carcinoma, Pancreatic Ductal / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D007328:Insulin / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D015291:Transforming Growth Factors / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
D000970:Antineoplastic Agents; D007328:Insulin; D009363:Neoplasm Proteins; D014212:Tretinoin; D015291:Transforming Growth Factors; D066246:ErbB Receptors