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Unformatted text preview: on in melanocytes of normal skin. 57 Chapter III – Medic and Ziman, 2010 Figure 3.1. PAX3 expression in melanocytic and melanoma cells. A) Immunohistochemistry shows PAX3 expression (top panel) in representative samples of normal skin, naevus, primary melanoma and melanoma metastasis, compared to MITF expression in adjacent sections (bottom panel). B‐D) Show the distribution of PAX3‐
positive melanocytes (arrowheads) in normal skin: along the hair follicle (early (B) and late (C) anagen); and in the epidermis (D). Arrows in D point to the cytoplasmic melanin deposit distinguishable from the nuclear PAX3 staining (arrowheads). Asterisk in (B) and (C) marks a dermal papilla. PAX3 was labelled with mouse monoclonal antibody (DSHB). E) PAX3 expression was analysed by RT‐PCR and the graph shows the mean fold increase of PAX3 expression in naevi, primary melanomas and lymph node metastases normalised to the expression in normal skin. 58 Chapter III – Medic and Ziman, 2010 Characterisation of PAX3positive cells: Coexpression of PAX3 and MITF In order to validate PAX3 expression in naevi and melanomas as well as to confirm that PAX3‐positive cells in normal skin are in fact melanocytes, co‐staining of PAX3 and MITF was assessed by immunofluorescence. Indeed, in all of the samples analysed, including normal skin, PAX3‐positive cells co‐express MITF (Figure 3.2, A‐C and E). However, in normal skin (as in other samples) a small number of cells showed only MITF and not PAX3 expression, highlighting the variation in normal epidermal melanocyte cell phenotype. In normal skin samples 81.6% of all MITF‐positive melanocytes were also PAX3‐
positive (Figure 3.2D). Both naevi and primary melanoma samples show similar numbers of MITF‐positive cells that also express PAX3 (97.2% and 94.5%, respectively) (Figure 3.2D). Interestingly, melanoma metastases show significantly less PAX3‐positive than MITF‐positive cells (Figure 3.2D), and generally these were weakly stained for PAX3. However, this was...
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This document was uploaded on 03/06/2014 for the course CHEMISTRY 12 at National University of Singapore.
- Spring '14