The nuclear matrix shell proteome of human epidermis

Background: Proteomic approaches have identified cancer specific biomarker proteins in the nuclear matrix fraction of cancer cells. We wanted to determine whether a similar approach could be used to investigate melanoma biomarkers. Objective: Since it was not clear that a nuclear matrix fraction could be isolated from the intact human epidermis, we first wanted to determine whether a nuclear matrix fraction could be isolated from the intact epidermis of human skin. If this was possible, we secondarily wanted to compare the proteome of cultured melanoma and carcinoma cells to that of the intact epidermis. Methods: We applied two-dimensional electrophoresis (2DGE) and LC/MS/MS to identify proteins isolated in the nuclear matrix shell protein fraction isolated from the human epidermis and from cultured primary skin and cancer cells. Results: A subcellular fractionation of intact epidermis succeeded in yielding a nuclear matrix shell which made up approximately 40% of total tissue protein. Only 5-10% of total cell protein was fractionated in the nuclear matrix shell of cultured skin cells. The nuclear matrix shell of the intact epidermis was distinguishable from cultured keratinocytes or HaCaT cells by expression of keratin 1. The nuclear matrix of the epidermis was distinguishable from melanocytes and melanoma cells by expression of vimentin in melanocyte-derived cells and by expression of desmoplakin in the intact epidermis. Conclusion: The nuclear matrix-intermediate filament system can be isolated from the intact human epidermis. A careful examination of the protein composition of this subcellular fraction from the epidermis and skin cancers may identify useful cancer specific biomarkers.