Silencing of Ghrelin Receptor Expression Inhibits Endometrial Cancer Cell Growth in vitro and in vivo (#8)
Ghrelin is a peptide hormone produced in a range of organs and cancers derived from them, including adenocarcinomas1. It has endocrine, paracrine, and autocrine roles in both normal and disease states. Ghrelin is expressed in endometrial cancers, while its receptor, the growth hormone secretagogue receptor 1a (GHSR1a) is expressed at various levels in normal endometrium and cancer tissues. We previously showed that ghrelin has proliferative and anti-apoptotic functions in endometrial cancers, suggesting its potential role in promoting tumour growth2. To further investigate ghrelin-GHSR1a in endometrial cancer cell progression, we examined the effect of knockdown of GHS-R1a expression in the Ishikawa endometrial cancer cell line by using RNA interference (RNAi) both in vitro and in the NOD/SCID xenograft mouse model. The lentiviral short hairpin RNA targeting GHSR1a(GHSR1a-shRNA) resulted in a stable reduction of GHS-R1a mRNA and protein.GHSR1a-shRNA Ishikawa cells showed less non-stimulated cell proliferation compared to the scrambled controls and proliferated less in response to 100nM ghrelin than with controls (100% vs 118% of control, P<0.05). Tumour volumes of GHSR1a-shRNA Ishikawa xenograft tumours were significantly reduced compared with scrambled control tumours (333±173mm3 vs 1217±227mm3 , p=0.0012) as were tumour weights (0.590±0.293g vs 0.983±0.106g, p=0.008). Immunohistochemistry demonstrated GHS-R1a in benign and cancerous glands in human endometrial tissue specimens. In summary, our results indicate that decreasing the GHSR1a protein level by RNAi significantly inhibits endometrial cancer cell line and xenograft tumour growth, hence ghrelin-GHSR1a signalling may have an important role in the development of endometrial cancer. Demonstration of a functional role for ghrelin in endometrial growth and the detection of its receptor in endometrial cancers suggest that blocking GHS-R1a may be therapeutic in this cancer.
Acknowledgement: This work was supported by NHMRC, UQ, MMRI, and QUT. J.N.T.F. is a recipient of UQ Postgraduate Research Scholarship. P.J. is a recipient of QLD Government Smart Futures Fellowship
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