title: Canine melanoma diagnosis: RACK1 as a potential biological marker.
abstract: Melanoma diagnosis in dogs can be challenging due to the variety of histological appearances of canine melanocytic neoplasms. Markers of malignancy are needed. Receptor for activated C-kinase 1 (RACK1) was found to characterize melanomas in other mammals. We investigated the value of RACK1 detection in the classification of 19 cutaneous and 5 mucosal melanocytic neoplasms in dogs. These tumors were categorized as melanocytomas or benign and melanomas or malignant after evaluation of their morphology, mitotic index, and Ki-67 growth fraction. Using immunofluorescence, we confirmed microphthalmia-associated transcription factor (MITF) as a marker of normal and transformed melanocytic cells in dog tissues. All control (n = 10) and tumoral (n = 24) samples stained positively for MITF (34/34, 100%). Whereas RACK1 was not detected in healthy skin melanocytes, melanocytic lesions were all positive for RACK1 signal (24/24, 100%). RACK1 cytoplasmic staining appeared with 2 distinct distribution patterns: strong, diffuse, and homogeneous or granular and heterogeneous. All melanoma samples (13/13, 100%) stained homogeneously for RACK1. All melanocytomas (11/11, 100%) stained heterogeneously for RACK1. Immunohistochemistry was less consistent than immunofluorescence for all labelings in melanocytic lesions, which were often very pigmented. Thus, the fluorescent RACK1-MITF labeling pattern helped to distinguish melanomas from melanocytomas. Furthermore, RACK1 labeling correlated with 2 of 11 morphological features linked to malignancy: cell and nuclear size. These results suggest that RACK1 may be used as a marker in dog melanomas.
authors.affiliation: INRA, UMR955 de Génétique fonctionnelle et médicale, Ecole Nationale Vétérinaire d'Alfort, 7 avenue du Général de Gaulle, Maisons-Alfort, F-94704 France. Email: gegidy@vet-alfort.fr.
authors.forename: C
authors.initials: C
authors.lastname: Campagne
authors.forename: S
authors.initials: S
authors.lastname: Julé
authors.forename: C
authors.initials: C
authors.lastname: Alleaume
authors.forename: F
authors.initials: F
authors.lastname: Bernex
authors.forename: J
authors.initials: J
authors.lastname: Ezagal
authors.forename: S
authors.initials: S
authors.lastname: Château-Joubert
authors.forename: M
authors.initials: M
authors.lastname: Estrada
authors.forename: G
authors.initials: G
authors.lastname: Aubin-Houzelstein
authors.forename: J-J
authors.initials: JJ
authors.lastname: Panthier
authors.forename: G
authors.initials: G
authors.lastname: Egidy
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D003937:Diagnosis, Differential; D004283:Dog Diseases / Q000175:diagnosis* / Q000378:metabolism; D004285:Dogs; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology; D008545:Melanoma / Q000175:diagnosis / Q000378:metabolism / Q000662:veterinary*; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012878:Skin Neoplasms / Q000175:diagnosis / Q000378:metabolism / Q000662:veterinary*
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface
keywords: MITF; RACK1; diagnosis; dog; immunofluorescence; melanocytoma; melanoma