Cannabinoid Receptors CB1, CB2 and Orphan Receptor GPR55 in Canine Amelanotic Oral Melanomas: A Spontaneous Model to Explore Translational Targets in Immuno-Oncology

Cannabinoid receptors 1 (CB1R) and 2 (CB2R) are integral components of the endocannabinoid system and play key roles in modulating immune responses and tumor progression. The orphan receptor GPR55, sometimes referred to as a “third cannabinoid receptor,” has been increasingly implicated in oncogenesis, being associated with pro-proliferative and pro-metastatic signaling. Canine oral melanomas, particularly the amelanotic subtype, are highly aggressive and share biological similarities with human mucosal melanomas, making them valuable spontaneous models for translational research.
AIMS:
To assess the immunohistochemical expression of CB1R, CB2R, and GPR55 in canine amelanotic oral melanomas.
METHODOLOGY:
Twenty samples of canine oral amelanotic melanomas were analyzed. Indirect immunohistochemistry was performed using anti-CB1R (Origen®), anti-CB2R (Abcam®), and anti-GPR55 (Abcam®) antibodies, diluted 1:100, 1:200, and 1:200, respectively. Mucosa epithelium served as internal positive controls. Receptor expression in neoplastic cells was semi-quantitatively scored on a scale from 0 (negative) to 3 (strong) by three independent blinded observers.
RESULTS:
CB1R expression was absent or minimal