AUTHOR=Ayakannu Thangesweran , Taylor Anthony H. , Marczylo Timothy H. , Maccarrone Mauro , Konje Justin C. 

TITLE=Identification of Novel Predictive Biomarkers for Endometrial Malignancies: N-Acylethanolamines

JOURNAL=Frontiers in Oncology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2019.00430

DOI=10.3389/fonc.2019.00430

ISSN=2234-943X

ABSTRACT=<p><bold>Objective:</bold> To identify new biochemical markers for endometrial cancer (EC). Recent evidence suggests that members of the endocannabinoid system (<italic>N</italic>-acylethanolamines) that bind to and activate receptors that are dysregulated in EC are involved in this tumour's biology. These observations suggest increased <italic>N</italic>-acylethanolamine levels in the tissue that might appear in plasma and could be used as disease biomarkers.</p><p><bold>Methods:</bold><italic>N</italic>-arachidonoylethanolamine (anandamide, AEA) and the <italic>N</italic>-acylethanolamine substances, <italic>N</italic>-oleoylethanolamine (OEA), and <italic>N</italic>-palmitoylethanolamine (PEA) were quantified in plasma and endometrial tissue collected from 31 EC and seven atrophic controls using UHPLC-MS/MS. Receiver-operating characteristics (ROC) and logistic regression were used to determine diagnostic accuracy. Cannabinoid receptor 1 (CB1) and 2 (CB2) protein levels were determined by specific immunohistochemistry and histomorphometric analyses. Correlations between plasma and tissue levels of the three <italic>N</italic>-acylethanolamines and tissue levels of the three <italic>N</italic>-acylethanolamines and CB1 and CB2 receptor expression levels were determined using correlation analysis.</p><p><bold>Results:</bold> Plasma and tissue AEA and PEA levels were significantly (<italic>p</italic> &lt; 0.05) higher in EC than controls whilst OEA levels were significantly elevated in type 1 EC tissues but not in plasma. There were significant positive correlations between plasma and tissue levels of AEA (<italic>R</italic><sup>2</sup> = 0.302, <italic>p</italic> = 0.008) and PEA (<italic>R</italic><sup>2</sup> = 0.182, <italic>p</italic> = 0.047), but not for OEA (<italic>R</italic><sup>2</sup> = 0.022, <italic>p</italic> = 0.506). The diagnostic accuracies for EC were: sensitivity of 53.3%, specificity of 100% for plasma AEA (&gt;1.36 nM); sensitivity of 73.3%, specificity of 100% for plasma PEA (&gt;27.5 nM); and sensitivity of 93.3%, specificity of 28.6% for plasma OEA (&gt;4.97 nM). Logistic regression increased the area under the ROC curve (AUC) from 0.781 for AEA, 0.857 for PEA, and 0.543 for OEA to a combined AUC of 0.933 for EC diagnosis. Significant inverse correlations between tissue AEA (<italic>R</italic><sup>2</sup> = 0.343, <italic>p</italic> = 0.003) and PEA (<italic>R</italic><sup>2</sup> = 0.384, <italic>p</italic> &lt; 0.0001) levels and CB1 expression were observed. No correlation between tissue levels of OEA and CB1 and tissue levels of any of the three <italic>N</italic>-acylethanolamines and CB2 protein expression were observed, except in the type 1 EC patients.</p><p><bold>Conclusion:</bold> Since plasma AEA and PEA are significantly elevated in patients with EC and a reflection of production by the endometrial tumour, then these lipids have the potential to be useful biomarkers for the early diagnosis of EC.</p>