Transcription analysis in the MeLiM swine model identifies RACK1 as a potential marker of malignancy for human melanocytic proliferation
1 INRA, UMR955 Génétique Moléculaire et Cellulaire; Laboratoire conventionné CEA n°17 ; Ecole Nationale Vétérinaire d'Alfort, 7 avenue du Général de Gaulle, Maisons-Alfort, F-94704 France
2 Institut Pasteur, Unité de Génétique Fonctionnelle de la Souris; CNRS URA 2578, Département de Biologie du Développement, USC INRA, 25 rue du Dr. Roux, Paris, F-75724 France
3 Ecole Nationale Vétérinaire d'Alfort, Service d'Anatomie pathologique, 7 avenue de Général de Gaulle, Maisons-Alfort, F-94704 France
4 CEA, DSV, IRCM, SREIT, Laboratoire de Radiobiologie et d'Etude du Génome, INRA Jouy-en-Josas, F-78352 France
5 INRA, DGA, Laboratoire de Radiobiologie et d'Etude du Génome, Jouy-en-Josas, F-78352 France
6 Institute of Animal Physiology and Genetics, 27721 Libechov, Czech Republic
7 Institut Curie, Service d'Anatomopathologie, 26 rue d'Ulm, Paris, F-75005 France
Molecular Cancer 2008, 7:34 doi:10.1186/1476-4598-7-34Published: 28 April 2008
Metastatic melanoma is a severe disease. Few experimental animal models of metastatic melanoma exist. MeLiM minipigs exhibit spontaneous melanoma. Cutaneous and metastatic lesions are histologically similar to human's. However, most of them eventually spontaneously regress. Our purpose was to investigate whether the MeLiM model could reveal markers of malignancy in human melanocytic proliferations.
We compared the serial analysis of gene expression (SAGE) between normal pig skin melanocytes and melanoma cells from an early pulmonary metastasis of MeLiM minipigs. Tag identification revealed 55 regulated genes, including GNB2L1 which was found upregulated in the melanoma library. In situ hybridisation confirmed GNB2L1 overexpression in MeLiM melanocytic lesions. GNB2L1 encodes the adaptor protein RACK1, recently shown to influence melanoma cell lines tumorigenicity. We studied the expression of RACK1 by immunofluorescence and confocal microscopy in tissues specimens of normal skin, in cutaneous and metastatic melanoma developped in MeLiM minipigs and in human patients. In pig and human samples, the results were similar. RACK1 protein was not detected in normal epidermal melanocytes. By contrast, RACK1 signal was highly increased in the cytoplasm of all melanocytic cells of superficial spreading melanoma, recurrent dermal lesions and metastatic melanoma. RACK1 partially colocalised with activated PKCαβ. In pig metastases, additional nuclear RACK1 did not associate to BDNF expression. In human nevi, the RACK1 signal was low.
RACK1 overexpression detected in situ in human melanoma specimens characterized cutaneous and metastatic melanoma raising the possibility that RACK1 can be a potential marker of malignancy in human melanoma. The MeLiM strain provides a relevant model for exploring mechanisms of melanocytic malignant transformation in humans. This study may contribute to a better understanding of melanoma pathophysiology and to progress in diagnosis.