Circulating Endocannabinoids in Canine Cutaneous Mast Cell Tumor.

Simple Summary: Cutaneous mast cell tumors (cMCTs) are a common type of tumor in dogs. This study measured blood concentrations of endocannabinoids, namely 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA), and AEA congeners, namely N-palmitoylethanolamine (PEA) and N-oleoylethanolamine (OEA), in 17 dogs with cMCTs and 11 healthy dogs. Dogs with cutaneous mast cell tumors had significantly higher levels of 2-AG and lower levels of AEA and PEA compared to healthy dogs, while OEA levels showed no difference. The ability of these endocannabinoids to serve as differentiators between healthy dogs and those with tumors was evaluated, and 2-AG was found to be a highly accurate (98%) indicator for identifying dogs with cMCTs. Levels of 2-AG above 52.75 pmol/mL had 94% sensitivity and 90% specificity in detecting the tumor. This is the first study to show that endocannabinoid levels are altered in dogs with mast cell tumors, indicating their potential use as biomarkers for diagnosing or monitoring this type of cancer in the future. A cutaneous mast cell tumor (cMCT) is among the most common tumors in dogs. Endocannabinoids (eCBs) belong to the endocannabinoid system (ECS), which involves also cannabinoid receptors and an enzymatic system of biosynthesis and degradation. In this study, plasma levels of N-arachidonoylethanolamine (AEA), 2-arachidonoylglycerol (2-AG), N-palmitoylethanolamine (PEA), and N-oleoylethanolamine (OEA) were evaluated in 17 dogs with MCTs of varying histological grades and clinical stages, as well as in a control group of 11 dogs. Dogs affected by cMCT had higher plasma levels of 2-AG (p = 0.0001) and lower levels of AEA (p = 0.0012) and PEA (p = 0.0075) compared to the control group, while no differences were observed at the OEA level between healthy and cMCT dogs (p = 0.9264). The ability of eCBs to help discriminate between healthy and cMCT dogs was interrogated through the area under the ROC curve (AUC). An accuracy of 0.98 (95% confidence interval [CI], 0.94–1.02) was found for 2-AG, of 0.85 (95% CI, 0.71–0.99) for AEA, and of 0.81% for PEA (95% CI, 0.64–0.69). Values > 52.75 pmol/mL for 2-AG showed 94% sensitivity and 90% specificity in distinguishing cMCT. This is the first study to demonstrate alterations in plasmatic levels of eCBs in dogs affected by MCTs, suggesting the significance of these biomarkers in the tumorigenic process and their potential use as biomarkers in the future. [ABSTRACT FROM AUTHOR]