Immunohistochemical and TUNEL staining in vivo xenograft model. A,Immunohistochemistry with monoclonal antibodies directed against human Slug was performed to compare the Slug expression profile of Slug- and vector-transfectedclones in the in vivo human xenograft model. Bars, 21 mm. (a) Slug is intensely expressed in siRNA mock-transfected group.(b)Slug is weakly expressed in siRNA Slug-transfected group, B, TUNEL staining in the mock siRNA(c) and the siRNA Slug transfected groups(d).