Ghrelin O-acyltransferase (GOAT) is expressed in prostate cancer tissues and cell lines and expression is differentially regulated in vitroby ghrelin

Abstract

BackgroundGhrelin 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.MethodsWe 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.ResultsWe 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.ConclusionsThis 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.

Plasma ghrelin O‐acyltransferase (GOAT) enzyme levels: A novel non‐invasive diagnosis tool for patients with significant prostate cancer

“…In line with this, our group and others have recently demonstrated that GOAT enzyme is overexpressed (at the mRNA and/or protein level) in PCa tissues and PCa cell lines compared to healthy prostate tissues and normal cell lines, and, most importantly, we also reported that GOAT is oversecreted in PCa cells compared to normal prostate cells . In fact, this initial, pilot study from our group revealed that plasma GOAT levels could discriminate between PCa and healthy subjects, suggesting that this enzyme might be used as a potential novel non‐invasive biomarker of PCa .…”

“…13 Consequently, these data have led to widespread criticism that PCa is now an "overdiagnosed" and "overtreated" cancer based on the PSA test. Therefore, there is an urgent need for the identification of new diagnostic and prognostic biomarkers for PCa, especially for Sig PCa, in order to improve the clinical management of PCa and to reduce the elevated number of biopsies and the over- In line with this, our group and others have recently demonstrated that GOAT enzyme is overexpressed (at the mRNA and/or protein level) in PCa tissues and PCa cell lines compared to healthy prostate tissues and normal cell lines, 10,21 and, most importantly, we also reported that GOAT is oversecreted in PCa cells compared to normal prostate cells. 10 In fact, this initial, pilot study from our group revealed that plasma GOAT levels could discriminate between PCa and healthy subjects, suggesting that this enzyme might be used as a potential novel non-invasive biomarker of PCa.…”

Ghrelin: Ghrelin as a Regulatory Peptide in Growth Hormone Secretion

“…As in rats, a 28-amino acid peptide octanoylated at Ser3 is the major active form of human Ghrelin. However, the ratio of circulating desacyl ghrelin to acyl ghrelin is 9: 1 while in the human stomach, the ratio is around 1:3 [26,27].…”

“…The acylation of ghrelin promoted by Ghrelin O-acyltransferase (GOAT) [27] is essential not only for binding with GHS-R1a but also for stimulation of GH secretion [28,29]. Unacylated ghrelin cannot bind and activate the GHS-R 1a and hence is devoid of any effects on endocrine axes.…”

Ghrelin and Breast Cancer: Emerging Roles in Obesity, Estrogen Regulation, and Cancer

“…Ghrelin mRNA is then translated into preproghrelin, which contains 117 amino acids and can then be acylated and processed into ghrelin and obestatin (Figure 2). Ghrelin- O -acyl transferase (GOAT) is the only enzyme that has been molecularly identified to be able to acylate ghrelin (26–28). The ghrelin pro-peptide is cleaved by signal peptidase, prohormoneconvertase 1/3 (PC 1/3) (29), and carboxypeptidase-B like enzyme (18).…”