Ghrelin and its unacylated isoform stimulate the growth of adrenocortical tumor cells via an anti-apoptotic pathway.
Ghrelin is expressed in normal human adrenocortical cells and induces their proliferation through growth hormone secretagogue receptor 1a (GHS-R1a). Consequently, it was of interest to us to determine whether acylated ghrelin and its predominant serum isoform, unacylated ghrelin, also act as factors for adrenocortical carcinoma cell growth. To examine a potential ghrelin-regulated system in adrenocortical tumors, we measured proliferative effects of acylated and unacylated ghrelin in the adrenocortical carcinoma cell lines SW-13 and NCI-H295R. We also examined the expression of ghrelin, GHS-R1a, and corticotrophin-releasing factor receptor 2 (CRF-R2). Acylated and unacylated ghrelin in the nanomolar range dose-dependently induced adrenocortical cell growth up to 200% of untreated controls, as measured by thymidine uptake and WST1 assay. The proliferative effects of acylated and unacylated ghrelin in SW-13 cells was blocked by [D-Lys(3)]growth hormone-releasing peptide 6 (GHRP6), but a CRF-R2 antagonist had no effect on unacylated ghrelin growth stimulation. Cell cycle analysis suggests that acylated and unacylated ghrelin suppress the sub-G(0)/apoptotic fraction by up to 50%. Measurement of DNA fragmentation and caspase-3 and -7 activity in SW-13 cells confirmed that acylated and unacylated ghrelin suppress apoptotic rate. SW-13 cells express preproghrelin mRNA and secrete ghrelin, and [D-Lys(3)]GHRP6 suppresses their basal proliferation rate, strongly suggesting that ghrelin could act as an auto/paracrine growth factor. Acylated and unacylated ghrelin are potential auto/paracrine factors acting through an antiapoptotic pathway to stimulate adrenocortical tumor cell growth. Unacylated ghrelin-stimulated growth is suppressed by an antagonist of GHS-R1a, suggesting either that unacylated ghrelin is acylated before its action or that ghrelin, unacylated ghrelin, and [D-Lys(3)]GHRP-6 bind to a novel receptor in these cells.
Delhanty
P J D
PJ
Department of Internal Medicine, Rm. Ee542, Erasmus Medical Centre, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands. p.delhanty@erasmusmc.nl
van Koetsveld
P M
PM
Gauna
C
C
van de Zande
B
B
Vitale
G
G
Hofland
L J
LJ
van der Lely
A J
AJ
D000107:Acetylation; D000306:Adrenal Cortex Neoplasms / Q000473:pathology*; D018268:Adrenocortical Carcinoma / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D054439:Ghrelin; D006801:Humans; D036361:Peptide Hormones / Q000378:metabolism / Q000494:pharmacology*; D020033:Protein Isoforms / Q000494:pharmacology; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D054440:Receptors, Ghrelin; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
C101531:CRF receptor type 2; D054439:Ghrelin; D036361:Peptide Hormones; D020033:Protein Isoforms; D018019:Receptors, Corticotropin-Releasing Hormone; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin