Fig. 1.

PPARβ expression in normal skin, primary and metastatic melanoma. Representative examples of normal skin (a), nodular melanoma (b), a melanoma metastasis (c) and superficial spreading melanoma (d) stained for PPARβ (rabbit polyclonal antibody and VIP as substrate, purple). Sections were counterstained with haematoxylin to visualise nuclei. Note the mostly nuclear expression of PPARβ in keratinocytes, melanocytes and hair follicles and the heterogenous, both nuclear and cytoplasmatic expression in tumoural melanocytic lesions. Within the same melanoma metastasis, regions of moderate (c (b)) and low (c (c)) PPARβ expression coexist. In superficial spreading melanoma, PPARβ expression dominated in the invasive front of the tumour (d). Arrows in (d (a)) indicate the position of the high-power magnifications of the invasive front (d, (b)) and adjacent tissue (epidermis) with melanocyte atypia (d (c)). No staining could be observed by replacing the first antibody with normal serum (e). Human colon sections served as additional positive (f (a)) and negative (f (b)) controls (DAB substrate, brown). Scale bars indicate 50 µm