Open Access Research article

RACK1, a clue to the diagnosis of cutaneous melanomas in horses

Cécile Campagne12, Sophia Julé126, Florence Bernex123, Mercedes Estrada4, Geneviève Aubin-Houzelstein125, Jean-Jacques Panthier125 and Giorgia Egidy125*

Author affiliations

1 INRA, UMR955 de Génétique fonctionnelle et médicale, Ecole Nationale Vétérinaire d’Alfort, 7 avenue du Général de Gaulle, Maisons-Alfort, F-94704, France

2 Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, 7 avenue du Général de Gaulle, Maisons-Alfort, F-94704, France

3 Ecole Nationale Vétérinaire d’Alfort, Service d’Anatomie pathologique, 7 avenue Général de Gaulle, Maisons-Alfort, F-94704, France

4 Laboratoire IDEXX Alfort, 17 allée Jean-Baptiste Preux, Alfortville, F-94140, France

5 Département de Biologie du Développement, Institut Pasteur, Unité de Génétique Fonctionnelle de la Souris; CNRS URA 2578, USC INRA, 25 rue du Dr. Roux, Paris, F-75724, France

6 Present address: CRC – UMRS 872, 15 rue de l’Ecole de Médecine, Paris, F-75006, France

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Citation and License

BMC Veterinary Research 2012, 8:95  doi:10.1186/1746-6148-8-95

Published: 29 June 2012



Melanocytic proliferations are common in horses but the diagnosis of malignancy is not always straightforward. To improve diagnosis and prognosis, markers of malignancy are needed. Receptor for activated C kinase 1 (RACK1) protein may be such a marker. RACK1 was originally found to characterize malignant melanocytic lesions in the Melanoblastoma-bearing Libechov minipig (MeLiM) and, later, in human patients. Our purpose was to investigate the value of RACK1 in the classification of cutaneous melanocytic proliferations in horses.


Using immunofluorescence, we report here that both MITF (Microphthalmia-associated transcription factor) and PAX3 (Paired box 3) allow the identification of melanocytic cells in horse skin samples. Importantly, RACK1 was detected in melanocytic lesions but not in healthy skin melanocytes. Finally, we found that RACK1 labeling can be used in horses to distinguish benign melanocytic tumors from melanomas. Indeed, RACK1 labeling appeared more informative to assess malignancy than individual histomorphological features.


This study confirms that horses provide an interesting model for melanoma genesis studies. It establishes MITF and PAX3 as markers of horse melanocytic cells. RACK1 emerges as an important marker of malignancy which may contribute to progress in the diagnosis of melanomas in both human and veterinary medicine.

Melanoma; Diagnosis; RACK1; MITF; PAX3