Yeh AH, Jeffery PL, Duncan RP, Herington AC, Chopin LKGhrelin and a novel preproghrelin isoform are highly expressed in prostate cancer and ghrelin activates mitogen-activated protein kinase in prostate cancer. Clin Cancer Res 11: 8295-8303

Authors' Affiliation: School of Life Sciences, Queensland University of Technology, Brisbane, Australia.
Clinical Cancer Research (Impact Factor: 8.72). 12/2005; 11(23):8295-303. DOI: 10.1158/1078-0432.CCR-05-0443
Source: PubMed


There is evidence that the hormone ghrelin stimulates proliferation in the PC3 prostate cancer cell line although the underlying mechanism(s) remain to be determined. A novel, exon 3-deleted preproghrelin isoform has previously been detected in breast and prostate cancer cells; however, its characterization, expression, and potential function in prostate cancer tissues are unknown.
Expression of ghrelin and exon 3-deleted preproghrelin was investigated in prostate cancer cell lines and tissues by reverse transcription-PCR and immunohistochemistry. Proliferation and apoptosis assays were done in the LNCaP prostate cancer cell line to determine if ghrelin stimulates proliferation and/or cell survival. Stimulation of mitogen-activated protein kinase (MAPK) pathway activation by ghrelin was determined in PC3 and LNCaP cells by immunoblotting with antibodies specific for phosphorylated MAPKs.
Prostate cancer tissues display greater immunoreactivity for ghrelin and exon 3-deleted preproghrelin than normal prostate tissues, and prostate cancer cell lines secrete mature ghrelin into conditioned medium. Treatment with ghrelin (10 nmol/L), but not the unique COOH-terminal peptide derived from exon 3-deleted preproghrelin, stimulates proliferation in the LNCaP cells (45.0 +/- 1.7% above control, P < 0.01) and rapidly activates the extracellular signal-regulated kinase-1/2 MAPK pathway in both PC3 and LNCaP cell lines. Ghrelin, however, does not protect prostate cancer cells from apoptosis induced by actinomycin D (1 microg/mL). The MAPK inhibitors PD98059 and U0126 blocked ghrelin-induced MAPK activation, as well as proliferation, in both cell lines.
These data suggest that these components of the ghrelin axis may have potential as novel biomarkers and/or adjunctive therapeutic targets for prostate cancer.

Full-text preview

Available from:
  • Source
    • "However, the ghrelin gene can also undergo additional processes of alternative splicing such as exon skipping or intron retention. Specifically, an event of exon 3 skipping has been documented (Yeh et al. 2005), which generates a 91-amino acid peptide named the Ex3-deleted ghrelin that lacks the coding region for obestatin (Fig. 1). Although the precise functions of the Ex3-deleted ghrelin variant remain uncertain, its expression is increased in human prostate and breast cancers (Seim et al. 2009), suggesting a putative role in these pathologies. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ghrelin is a 28-aa acylated hormone, highly expressed in the stomach, which binds to its cognate receptor (GHSR-1a) to regulate a plethora of relevant biological processes, including food intake, energy balance, hormonal secretions, learning, inflammation, etc. However, ghrelin is, in fact, the most notorious component of a complex, intricate regulatory system comprising a growing number of alternative peptides (i.e. obestatin, unacylated ghrelin, In1-ghrelin, etc.), known (GHSRs) and, necessarily unknown receptors, as well as modifying enzymes (i.e. ghrelin-O-acyl-transferase or GOAT), which interact among them as well as with other regulatory systems in order to tightly modulate key (patho)-physiological processes. This multiplicity of functions and versatility of the ghrelin system sprouts from a dual, genetic and functional, complexity. Importantly, a growing body of evidence suggests that dysregulation in some of the components of the ghrelin system can lead to or influence the development and/or progression of highly concerning pathologies such as endocrine-related tumors, inflammatory/cardiovascular diseases, and neurodegeneration, wherein these altered components could be used as diagnostic, prognostic or therapeutic targets. In this context, the aim of the present review is to integrate and comprehensively analyze the multiple components and functions of the ghrelin system described to date in order to define and understand its biological and (patho)-physiological significance.
    Full-text · Article · Nov 2013 · Journal of Endocrinology
  • Source
    • "These results could in part account for the high obestatin concentrations detected in human semen samples (Moretti et al., 2011). Studies have reported that prostate cancer and prostate cancer cell lines are able to produce ghrelin (Yeh et al., 2005); however, according to our findings, normal prostate cells fail to express this hormone. Finally, ghrelin and obestatin were detected by immunofluorescence in ejaculated human spermatozoa. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The role of ghrelin and obestatin in male reproduction has not completely been clarified. We explored ghrelin and obestatin localisation in the male reproductive system. Polyclonal antibodies anti-ghrelin and anti-obestatin were used to detect the expression of these hormones in human testis, prostate and seminal vesicles by immunocytochemistry, while in ejaculated and swim up selected spermatozoa by immunofluorescence. Sertoli cells were positive for both peptides and Leydig cells for ghrelin; germ cells were negative for both hormones. Mild signals for ghrelin and obestatin were observed in rete testis; efferent ductules were the most immune reactive region for both peptides. Epididymis was moderately positive for ghrelin; vas deferens and seminal vesicles showed intense obestatin and moderate ghrelin labelling; prostate tissue expressed obestatin alone. Ejaculated and selected spermatozoa were positive for both peptides in different head and tail regions. This study confirms ghrelin localisation in Leydig and Sertoli cells; the finding that ghrelin is expressed in rete testis, epididymis, vas deferens and seminal vesicles is novel, as well as the localisation of obestatin in almost all tracts of the male reproductive system. This research could offer insights for stimulating other studies, particularly on the role of obestatin in sperm physiology, which is still obscure.
    Full-text · Article · Oct 2013 · Andrologia
  • Source
    • "As prostate cancer cell lines produce ghrelin, and exogenous ghrelin treatment stimulates cell proliferation in prostate cancer cell lines, we hypothesized that the ghrelin axis may play an autocrine/paracrine role in prostate cancer [39]. Our previous studies demonstrated that ghrelin and the ghrelin receptor, GHSR, are expressed at the mRNA and protein levels in prostate cancer cell lines and prostate cancer specimens [16,38,39]. A study demonstrating that a fluorescein-labelled ghrelin (1–18) probe binds prostate cancer tissue with high specificity also demonstrated GHSR1a expression in the PC3 and LNCaP prostate cancer cell lines and the BPH-1 cell line [20]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ghrelin is a 28 amino acid peptide hormone that is expressed in the stomach and a range of peripheral tissues, where it frequently acts as an autocrine/paracrine growth factor. Ghrelin is modified by a unique acylation required for it to activate its cognate receptor, the growth hormone secretagogue receptor (GHSR), which mediates many of the actions of ghrelin. Recently, the enzyme responsible for adding the fatty acid residue (octanoyl/acyl group) to the third amino acid of ghrelin, GOAT (ghrelin O-acyltransferase), was identified. We used cell culture, quantitative real-time reverse transcription (RT)-PCR and immunohistochemistry to demonstrate the expression of GOAT in prostate cancer cell lines and tissues from patients. Real-time RT-PCR was used to demonstrate the expression of prohormone convertase (PC)1/3, PC2 and furin in prostate cancer cell lines. Prostate derived cell lines were treated with ghrelin and desacyl ghrelin and the effect on GOAT expression was measured using quantitative RT-PCR. We have demonstrated that GOAT mRNA and protein are expressed in the normal prostate and human prostate cancer tissue samples. The RWPE-1 and RWPE-2 normal prostate-derived cell lines and the LNCaP, DU145, and PC3 prostate cancer cell lines express GOAT and at least one other enzyme that is necessary to produce mature, acylated ghrelin from proghrelin (PC1/3, PC2 or furin). Finally, ghrelin, but not desacyl ghrelin (unacylated ghrelin), can directly regulate the expression of GOAT in the RWPE-1 normal prostate derived cell line and the PC3 prostate cancer cell line. Ghrelin treatment (100nM) for 6 hours significantly decreased GOAT mRNA expression two-fold (p < 0.05) in the PC3 prostate cancer cell line, however, ghrelin did not regulate GOAT expression in the DU145 and LNCaP prostate cancer cell lines. This study demonstrates that GOAT is expressed in prostate cancer specimens and cell lines. Ghrelin regulates GOAT expression, however, this is likely to be cell-type specific. The expression of GOAT in prostate cancer supports the hypothesis that the ghrelin axis has autocrine/paracrine roles. We propose that the RWPE-1 prostate cell line and the PC3 prostate cancer cell line may be useful for investigating GOAT regulation and function.
    Full-text · Article · Jul 2013 · Reproductive Biology and Endocrinology
Show more