Tandem Mass Spectrometry Study Using Micro-Dissected Epithelial Cells from Psoriasis and Chronic Eczematous Dermatitis
Richard A Owings, Jennifer Kaley, Stephanie Byrum, Jeffrey Givens, Alan Tackett, Wang Cheung. University of Arkansas for Medical Sciences, Little Rock, AR
Background: Psoriasis and chronic eczematous dermatitis are clinically distinct entities. However there is an overlap in their histopathologic appearance. Additionally, the molecular mechanisms leading to each disease state are quite different. Previous studies in our lab have validated the use of tandem mass spectroscopy in preparations made from formalin fixed paraffin embedded tissue (FFPE) to identify altered protein expression in cutaneous tumors. This study aims to determine if this method can be used to identify differentially expressed proteins in inflammatory lesions such as psoriasis and chronic eczematous dermatitis. Additionally, proteins that are variably expressed will then be the target for further analysis.
Design: Epidermal cells from 4 cases of psoriasis or chronic eczematous dermatitis were harvested via laser micro-dissection. The proteins were extracted and analyzed by Thermo-LTQ-XL mass spectrometer coupled to an Eksigent nanoLC-2D. Using NSAF spectral counting techniques, we were able to normalize and compare protein levels between samples. Anything with 1.5 fold difference is considered to be a significant difference.
Results: 891 distinct proteins were identified in these samples. Interestingly, only 15 proteins were found to be up-regulated in psoriasis and 3 proteins were found to be down-regulated in psoriasis. Only three of these proteins have been published in the literature as having misregulated expression in psoriasis. From this list, we have chose cytokeratin 10 and CCT3 (chaperon containing TCP3) proteins, to validate the mass spectrometry results using immunohistochemical stains. Both of these proteins appear to be increased in psoriatic lesions when compared to normal epidermis and eczematous lesions.
Conclusions: This study demonstrates that laser micro-dissected FFPE sections coupled with mass spectrometry can even identify biomarkers for inflammatory lesions. Finding only 18 proteins that have significant expression differences between psoriasis and eczema is not surprising, because histologically these two lesions have many overlapping features. Our findings can be validated by immunohistochemistry, which may then be used to distinguish psoriasis and chronic eczematous dermatitis.
Monday, March 19, 2012 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 82, Monday Morning