ORIGINAL ARTICLE

Retinoic acid can induce markers of endocrine transdifferentiation in pancreatic ductal adenocarcinoma: preliminary observations from an in vitro cell line model

T H El-Metwally¹, M R Hussein², S Kh Abd-El-Ghaffar³, M M Abo-El-Naga⁴, A B Ulrich⁵, P M Pour⁵

¹ Department of Medical Biochemistry, Faculty of Medicine, Assiut University, Assiut, Egypt
² Departments of Pathology, Faculty of Medicine, Assiut University
³ Faculty of Veterinary Medicine, Assiut University
⁴ Department of Anatomy & Embryology, Faculty of Medicine, Al-Azhar University, Damietta, Egypt
⁵ Department of Pathology & Microbiology, Eppely Cancer Institute & UNMC, Omaha, Nebraska, USA

Correspondence to:
Dr T H El-Metwally
Department of Medical Biochemistry, Faculty of Medicine, Assiut University, Assiut, Egypt; thelmetwally{at}hotmail.com

Background and hypothesis: 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.

Material and 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 µmol/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) ß2, TGF 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 µmol/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 TGF and TGFß₂; 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.

Abbreviations: atRA, all-trans-retinoic acid; CK, cytokeratin; EGFR, epidermal growth factor receptor; ELISA, enzyme-linked immunosorbent assay; HPAF, pancreatic ductal adenocarcinoma cells; PDX-1, pancreas duodenum homeobox-l; TGF, transforming growth factor; TUNEL, terminal deoxynucleotidyl transferase

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