To shed light on the multistep process of
squamous cell carcinoma development and the underlying pathologic mechanisms, we performed comparative
proteome analysis of keratinocytes, keratinocytes stimulated with Il-1beta, and A431
epidermoid carcinoma cells. Fractionation of the cells into supernatant, nucleus, and cytoplasm was followed by
protein separation, proteolytic digest, and nano-LC separation, and fragmentation using an ion trap mass spectrometer. Specific bioinformatics tools were used to generate a list of keratinocyte-specific
proteins. Ninety percent of these
proteins were found to be upregulated in keratinocytes versus the A431 cells. Classification of the identified
proteins by biologic function and gene set enrichment analysis revealed that keratinocytes produced more
proteins involved in cell differentiation, cell adhesion, cell junction,
calcium ion,
calmodulin binding, cytoskeleton organization, and cytokinesis, whereas A431 produced more
proteins involved in cell cycle checkpoint, cell cycle process, RNA processing and transport, DNA damage and repair,
RNA and
DNA binding, and chromatin remodeling. The
protein signatures of A431 and normal keratinocytes treated with IL-1beta showed marked similarity, confirming that
inflammation is an important step in malignant transformation in nonmelanoma
skin cancer. Thus,
proteome profiling and bioinformatic processing may support the understanding of the underlying mechanisms, with the potential to facilitate development of early
biomarkers and patient-tailored
therapy.