SOX Family Members Expression in Canine Oral Melanoma: Role of the SOX3 in Tumor Aggressiveness

The aggressiveness of oral melanoma can be related to several mutations that occur during development. Based on the knowledge of the role of transcription factors of the SOX family in other neoplastic types, it is necessary to understand their behavior in oral melanomas. In this work, the expression of SOX2, SOX3, and SOX10 and its relationship with the proliferative index and histological aspects indicative of aggressiveness in canine oral melanomas were evaluated. Thirty tumors were histologically reviewed and the expression of Melan-A, SOX2, SOX3, SOX10, and Ki67 in these tumors were determined. All tumors presented histomorphological characteristics compatible with malignant tumors and immunopositivity for Melan-A. The expression of SOX2, SOX3, and SOX10 was observed in 7/30 (23.3%), 6/30 (20%), and 23/30 (76.6%) of the cases, respectively. Among the analyzed markers, the relationship between the loss of SOX3 expression in tumors with higher proliferative rates was highlighted. An inverse correlation was also observed between the expression cytoplasmic SOX10 and nuclear SOX10, suggesting a change in the location of this protein in oral melanomas. Among the SOX family proteins studied, the SOX3 protein plays a role in the regulation of cell proliferation in oral melanomas, and it is suggested that the SOX2 and SOX10 proteins are constitutively expressed in these neoplasms, without a determining role for aggressiveness. New studies of this gene transcription pathway may assist in possible prognostic and predictive determinations of the SOX3 protein in oral canine melanoma.