BRAF and epithelial-mesenchymal transition in primary cutaneous melanoma: a role for Snail and E-cadherin?

In vitro studies in melanoma indicate that up-regulation of the transcriptional repressor Snail occurs with a concomitant decrease of its target E-cadherin, both hallmarks of epithelial-mesenchymal transition-an association not established in vivo. We sought to elucidate the relationship between BRAF, Snail, E-cadherin, and established histopathologic prognosticators in primary cutaneous melanoma. Archived annotated samples with a diagnosis of primary cutaneous melanoma were retrieved (n = 68 cases; 34 BRAF mutant and 34 BRAF wild type) and immunohistochemically stained for Snail and E-cadherin protein expression. A semiquantitative scoring system was used. Multivariate logistic analysis was used to control confounders of BRAF. Snail expression was significantly associated only with ulceration (42% versus 13%; P = .02). E-cadherin expression was present in 26% of BRAF mutant and 71% of BRAF wild-type cases (P = .0003). Loss of E-cadherin expression was associated with female sex (60% versus 34%; P = .05), BRAF mutation (74% versus 29%; P = .0003), thickness greater than or equal to 1 mm (68% versus 32%; P = .004), mitosis (63% versus 25%; P = .007), and ulceration (75% versus 44%; P = .05). BRAF mutation was associated with male sex (60% versus 30%; P = .02), Breslow thickness (P = .007), thickness greater than or equal to 1 mm (68% versus 29%; P = .002), and ulceration (75% versus 42%; P = .02). Snail expression did not correlate with loss of E-cadherin expression (47% versus 53%; P = .79). After controlling for potential confounding, BRAF mutation was associated with loss of E-cadherin (adjusted odds ratio, 8.332; 95% confidence interval, 2.257-30.757; P = .0015) and Breslow thickness greater than 1 mm (adjusted odds ratio, 7.360; 95% confidence interval, 1.534-35.318; P = .0126). Our findings, indicating that mutant BRAF represses E-cadherin expression, implicating a catalytic role for BRAF in epithelial-mesenchymal transition.