Ghrelin promotes pancreatic adenocarcinoma cellular proliferation and invasiveness

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Abstract

Ghrelin, a newly described potent orexigenic peptide, may have therapeutic potential in patients with cachexia. We assessed whether pancreatic adenocarcinoma, commonly associated with marked cachexia, is a ghrelin-responsive malignancy. Pancreatic adenocarcinoma cells were exposed to ghrelin (0–100 nM). Proliferation was determined by MTT assay. Ghrelin, ghrelin 1a and 1b receptor expression and Akt phosphorylation were assessed. The effects of ghrelin (± its antagonist d-Lys-GHRP6, or the PI3-K inhibitor Wortmannin) on cellular motility and invasiveness were quantified by Matrigel Boyden chamber assay. All cell lines expressed ghrelin 1a and 1b receptor transcript and protein, but only PANC1 weakly expressed ghrelin transcript. Ten nanomolar ghrelin increased proliferation, motility, invasiveness, and Akt phosphorylation in all cell lines. Proliferation was affected dose-dependently, being suppressed at higher ghrelin concentrations. d-Lys-GHRP6 suppressed ghrelin-induced proliferation, invasion, and Akt phosphorylation. Wortmannin abolished the effects of ghrelin on motility and invasiveness. Pancreatic adenocarcinoma is a ghrelin-responsive malignancy.

Section snippets

Materials and methods

Cell lines. Poorly differentiated human pancreatic cancer cell lines PANC1 and MIAPaCa2 and well-differentiated lines BxPC3 and Capan2 were obtained from ATCC (Rockville, MD). PANC1, MIAPaCa2, and BxPC3 were maintained in Dulbecco’s modified Eagle’s medium (DMEM) containing 10% fetal bovine serum (FBS) and Capan2 was maintained in McCoy’s 5A medium containing 10% FBS in a humidified (37 °C, 5% CO2) incubator. All cell lines were sub-cultured before confluence and seeded at a density of 1 × 104 

Results

Ghrelin transcript was detected at very low levels in only PANC1 (Fig. 1). Ghrelin peptide was not detected in any cell line examined (Fig. 2). GHS-R1a and b transcripts were present in all cell lines tested. Single RT-PCR products were detected for the ghrelin 1a (65 bp) and 1b (66 bp) receptor. Expression of both the functional GHS-R1a isoform and GHS-R1b was confirmed at the protein level by Western analysis. Ghrelin treatment for 72 h increased cellular proliferation relative to control cells

Discussion

In this study, we have demonstrated expression of GHS-R1a and 1b isoforms in pancreatic adenocarcinoma cells. Although ghrelin transcript was only weakly present in PANC1 and ghrelin peptide was not detected, cellular proliferation, invasiveness, and motility were stimulated by exposure to 10 nM ghrelin, indicating that pancreatic adenocarcinoma is ghrelin-responsive. In addition, we have demonstrated that the PI3-K/Akt pathway is an important mediator of ghrelin’s stimulatory effects on

Acknowledgements

This study was supported by a grant from the National Pancreas Foundation and by National Institute of Health Grants DK02786 (E.E.W.) and DK47326 (S.W.A.). The authors gratefully acknowledge the technical support of Jan Rounds.

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