The B16-F10 mouse model of melanoma is a widely used model to study many aspects of cancer biology and therapeutics in a solid tumor. Melanomas aggressively progress within a dynamic microenvironment containing in addition to tumor cells, stroma cells and components such as fibroblasts, immune cells, vascular cells, extracellular matrix (ECM) and extracellular molecules. The goal of this study was to elucidate the processes of tumor progression by identifying differentially expressed proteins in the tumor mass during specific stages of tumor growth. A comparative proteome analysis was performed on B16-F10 derived tumors in C57BL/6 mice at days 3, 5, 7, and 10. Statistical approaches were used to determine quantitative differential protein expression at each tumor time stage. Hierarchical clustering of 44 protein spots (p < 0.01) revealed a progressive change in the tumor mass when all 4 time stages were classified together, but there was a clear switch in expression of these proteins between the day 5 and the day 7 tumors. A trend analysis showed 53 protein spots (p < 0.001) following 6 predominant kinetic paths of expression as the tumor progressed. The protein spots were then identified using MALDI-TOF mass spectrometry. Proteins involved in glycolysis, inflammation, wounding, superoxide metabolism, and chemotaxis increased during tumorigenesis. From day 3 to day 7 VEGF and active cathepsin D were induced 7-fold and 4-fold, respectively. Proteins involved in electron transport, protein folding, blood coagulation, and transport decreased during tumorigenesis. This work illustrates changes in the biology of the B16-F10 tumor mass during tumor progression.

Keywords: proteomics • melanoma • tumor progression • Cathepsin D • albumin • VEGF